Make a donation today! Help support your favorite classic fiberglass boating informational site today by making a donation in any amount. Simply paypal swood@fiberglassics.com FAQ (frequently asked questions) Welcome to our little frequently asked questions area. This section is designed to get you on your way & answer some of the most asked questions there are. We hope that you find the information below helpful in your quest to get on the water. Click a folder below to open, or.... Open All | Close All HELP! How do I identify my boat: Soooooooo, how do you identify that boat you just got? Here's how. Identification center coming soon...11:53 AM 11/4/2009 Back to top & close A quick tour of a boat: Let's take a quick tour of a boat to help familiarize yourself. It's always helpful to know what you're talking about. Below is an image with the basic areas of a boat and their descriptions. Back to top & close Basic Boating Lingo: Boat Info - Boating Lingo As you get more into boating, talking on the message boards and into the general hobby, we thought it might be nice if you knew what some of the terms are. Below are some of the typical boating terms in use today. There are more, but this list has been compiled from older sources. A special thanks to Ken Faulkner for providing this information and taking the time to round it up. A - K: Abaft - Toward the rear. Astern. Aft. Abeam - Directly to one side. Adrift - Floating with the wind or current. Not moored. Without Power. Adrift Hull - A design in which two or more hulls trap a mixture of air and spray beneath the planing surface at planing speed. Thus boat is partially supported on air, giving a softer ride. Afloat - Clear of the bottom. Carried by the water. Afoul - Tangled or snarled. Aft - Toward the rear, or stern of a boat. Afterplane - An elevating device attached to rear of boat transom to extend planing surface of boat. Aground - In contact with the bottom. Ahead - In front. Toward the front. Amidships - In or toward center of boat. Anchor - A carried device which is attached to a line or chain and used to secure or moor a boat by attachment to the bottom. Also to use an anchor. Angle of Attack - Angle at which planing surface of boat meets surface of water. A 3"-5" angle of attack is usually approximately correct for most planing hulls. Anticavitation Plate - A flat horizontal plate located just above the propeller at water line to prevent caviation at propeller. Astern - Toward rear of boat. Aft. Athwart - Across from side to side. Traveling or lying at right angles to direction of travel. Aweigh - Clear of bottom. Backwash - Water thrown back, as by a propeller or oar. Bail - To remove water from a boat by using a pail or similar container. Ballast - Weight carried to improve stability or balance. Batten Down - To make seaworthy or watertight. Beam - Distance across boat at widest part as distinguished from lengthwise. Also the side of boat at or near widest part. Beaufort Scale - A numbered code used in seamanship to denote the wind force. Belay - To make fast, or secure a boat, by wrapping line around mooring post, etc. Below - Downstairs. Below deck as on a cabin cruiser. Bend - A mooring knot. Berth - A mooring place for a boat. A bunk bed on a cabin cruiser. Bilge - Inside the hull in bottom of boat, especially the area enclosed below the lower deck. Bilge Pump - A pump used to remove bilge water. Bilge Water - Water accumulating in a bilge from leakage, spray, etc. Boat Hook - A sturdy pole with a hook built on one end for fending off or holding on to dock, or for fishing objects out of water. Bow - The forward, or front end of boat. Prow. Bracket Mount - A method of attaching outboard moto in which motor is suspended from a bracket aft of transom. Breaker - A wave breaking on a shore or reef. Breeze - Light to moderate air movement. See Beaufort Scale. Bridge - A raised platform or cockpit, to be occupied by the person controlling the boat. Broach - Turn crosswise to direction of travel with danger of capsizing. Bulkhead - A partition or wall located inside the hull. Buoy - A floating marker. Canoe - A long, narrow boat, usually sharp at both ends and usually propelled by paddles. Capsize - To upset. Cast Off - To unfasten mooring preparatory to leaving the dock or pier. Catamaran - A twin-hulled boat design. Caulk - The act of plugging seams in hull to make it watertight. Cavitation - The sharp bend or angle formed where sides or transom join the bottom of a boat. Chart - A map of a body of water showing landmarks, distances, depths, etc. Chine - The sharp bend or angle formed where sides or transom join the bottom of a boat. Clinker - A form of hull construction in which each external plank overlaps the preceding plank. Also called lapstrake. Compass - A navigational instrument to indicate direction. Cornering - The ability of a boat to perform a sharp turn without loss of control or danger of capsizing. Course - A planned direction or route. Crest - The highest peak of a wave. Cruiser - A power boat with facilities for living aboard, usually with a cabin. Current - The continuous flow or movement of the water. Dead Ahead - Directly ahead. Deck - A floor or platform aboard a boat. Dinghy - A small rowboat with sharp bow and wide stern. Displacement - The theory of flotation which designates that any object will float at the level at which it displaces its own weight in water. Displacement Hull - Type of boat design in which the entire weight of boat is supported by displacement when in motion. See planing hull. Dock - A landing pier. The act of tying to a landing pier. Draft - Operating depth from water line to lowest point of hull or motor. Drift - Deviation from a planned course caused by water or wind currents. Eddy - A circular flow of water running contrary to the main current. Fathom - A measure of depth equal to six feet. Fender - A guard to protect a boat hull from contact damage with pier or other object. Flare - A side extension at the bow of the boat, designed to deflect spray from the passenger compartment Flipping - Rolling outward and capsizing on a sharp, fast turn. Fore - Toward the front or bow of the boat. Fore & Aft - Parallel to normal direction of boat travel. Opposite to abeam. Forward - In the direction of the front of a boat. Fouled - Entangled, ensnarled or damaged by collision. Freeboard - Distance between waterline and top of gunwale. Gale - A strong wind, See Beaufort Scale. Galley - Ship's kitchen Gear - Equipment of any type. Gunwale - Side of the boat, or railing on the side. Head - Ships Toilet. Headway - Forward motion. Heave - To pull or throw line. Helm - Steering mechanism or control mechanism. Helmsman - Steersman. Hitch - Temporary knot. Hook - A defect of the bottom of a boat where a portion of the keel is higher than the bow or stern. Houseboat - A house-like structure built on a hull or pontoons and capable of navigation. Hull - Main body of vessel as distinguished from fixtures or propulsion mechanism. Hurricane - The strongest air movement, See Beaufort Scale. Hydrofoil - Small wing-like projections which carry the weight of a vessel in movement by planing through the water much like an aero plane wing supports a plane into the air. The main body of a hydrofoil equipped craft is suspended in the air above the surface and is capable of much higher speed and stability. Hydroplane - A flat bottomed, light boat designed for racing. Inboard - Located inside the hull. Inboard - Outboard - A type of propulsion unit using and inboard motor and outdrive. See Outdrive. Jet Drive - A means of boat propulsion utilizing a high speed jet of water as the propellant. John Boat - A long narrow, flat-bottomed boat, square at both ends. Keel - Main center frame member at bottom of the hull. Also used to refer to a shallow steering ridge on the bottom of the boat. Knot - Speed measurement. Equal to one nautical mile (6,080) ft. per hour. (as a comparason, 35 knots = approximately 40 mph) L - Z: Lapline - A series of small longitudinal projections on aluminum or fiberglass hulls which break up the wetted surface and provide lift and directional stability. Similar to lapstrake construction in a wooden hull. Lapstrake - Type of hull construction composed of a series of planks in which each overlaps the preceding plank. The longitudinal ridges provide lift and direction stability similar to lapline hull. Also called clinker built. Lee - The side of an island, boat, etc., which is protected from the wind. Leeward - On the lee side, or side away from the wind. Line - Nautical term for any rope. List - To lean to one side, or side because of damage or improper loading. Midship - In center of boat. Mooring - A berth of pier for securing a boat. Navigate - To select and steer a course. Neap Tide - Tide at time of moon when tidal movement is least. See Spring Tide. Oar - A device used for propelling or steering a boat by hand. Usually used in pairs. Differs from a paddle in that center of oar is attached or pivoted to a swiveling fulcrum on the gunwale. Outboard - Located outside the hull but attached as part of the boat. Outboard Motor - Small boat propulsion unit consisting of an engine, drive mechanism and steering mechanism combined in a unit which attaches to a boat but usually is carried mostly outside of the hull. Outdrive - Combined propulsion and steering mechanism which extends through boat transom and is powered by an inboard engine. Similar in appearance and construction to lower unit of an outboard motor. Paddle - A short, hand-held device used for propelling and steering a boat or canoe. Differs from an oar in that a paddle is used singly and held with both hands. Pier - A passenger or cargo platform floating on or suspended above the water, with one end attached to the shore and the other extending out into navigable water. Pitching - The act of being tossed up and down as by rough water. Planing - Rising partly out of the water when underway. Planing Hull - A type of hull design which rises partly out of the water when under way, the weight of the boat being supported on a small, flat planing surface of the hull and thus capable of much higher speed than the displacement hull. Plimsol Mark - A load-line on the side of a craft which designates the highest safe water line when loaded. Plowing - Moving through the water by pushing the water aside, as a displacement hull; rather than riding on top as a planing hull. Typical of the planing hull at slow speeds. Pontoon - A boat-like floating structure used as a support for a dock or a platform. Pontoon Boat - A boat design consisting of a deck or platform attached to two or more parallel pontoons and capable of mobility. Port - The side of a boat which is on the left when facing forward. Rake - The angle of the bow or stern of a boat with relation to the water. Reef - A sandbar or shelf of rock lying just below or even with the water surface. Ribs - Vertical frame members of a boat hull. Rocker - A defect in the bottom of a boat in which a portion of the keel is lower than the bow or stern. Roosertail - A high, curving spray extending out behind the stern of a speeding motorboat. Rolling - Rocking sideways caused by rough water. Round Bottom - A type of hull construction where a cross-section of the bottom has a rounded outline. Rowboat - A small boat usually propelled by oars. Rudder - A steering device consisting of a vertical flat piece of wood or metal affixed to the stern of a boat by a hinge. Runabout - A small, fast pleasure boat. Screw - A propeller. Scull - An oar used singly at the stern of a boat; or to propel a boat with such an oar. Sea Anchor - A canvas container or pail on a frame which is attached with a line to the bow or stern of a boat and dropped overboard to keep the boat heading into or away from the current. Seagoing - Suitable or capable of being used in the open sea. Seam - The joint between two plans in wooden hull construction. Semi-V Hull - Type of hull construction in which a cross-section of the bottom has the outline of a very flat vee. Seaworthy - Safe for use in the open sea. Sextant - A portable instrument used in navigation to determine location or time from the apparent position of the sun, moon or stars. Sheer - The upward slope of the gunwale of a boat toward the bow and stern. Shingle - A small, wedge-shaped projection added in pairs to the planing surface of a boat bottom to improve speed and control. Skeg - The downward projectiong fin on the keel of a sailboat. Also, the lower projection fin on the lower unit of an outboard. Skiff - A small, light boat for rowing or sailing. Spray - A driven misture of air and water droplets caused by the wind, a boat, or other moving object. Spray Rails - Projections from the sides of a hull, used at forward part to deflect spray; or aft to increase lift of the planing surface. Sponson - A part projection from the side of a boat for protection or support. Spring Tide - Tide at time of moon when tidal movement is greatest. See Neap Tide. Starboard - The side of a boat which is on the right when facing forward. Stem - The upright at forward end of hull at which the two sides meet. Also, forward part of boat. Stepped Hull - A hull design consisting of a series of steps upon which the boat rises with each increase in planing speed. Stern - The rear or after part of a boat. Strake - A continuous like of planks extending from stern to stern along sides and bottom of a boat. Also a hull so constructed. Surfing - The condition of forward travel midway between planing and plowing. Attained by planing hull just before reaching planing speed and characterized by maximum wake. Swamp - To fill or become filled with water. Swell - A continuous wave of water which is above the normal water level. The crest of a wave. See Trough. Three-Point Hull - A planing hull in which the weight of the boat is carried on three separated points when in planing position. Thwarts - Seats placed crosswise in rowboats or other small boats. Tide - The periodic rise and fall of the ocean caused by gravity attraction of the sun and moon. See Neap Tide, Spring Tide. Tiller - A lever for turning the rudder of a boat. Tilt Angle - The difference between the vertical swivelpoint of the outboard motor lower unit and the transom angle to which the mounting brackets are attached. Transom - The vertical portion of the rear of the hull to which the outboard motor is attached. Transom Chine - The line of juncture between the transom and planing surface of a hull. Tredronic Hull - A type of hull design characterized by a single bow and divided planing surface. Trim - The balance of a boat, or the way it floats in the water. Trough - The depression between the crests of two waves. See Crest, Swell. Tumble Home - Inward curve of boat's side above waterline. Under Way - Moving, as a boat under it's own power. Vee Bottom - A hull design in which a cross-section of the bottom is in the shape of a shallow vee. Wake - The track or trail left by a boat or other object in moving through the water. Water Line - The position on the sides of the hull which is even with the surface of the water. Waterplane - The area or surface of the boat bottom which supports the weight of the boat. In a planing hull, this area diminishes as speed increases and the pressure or load per sq. ft. of area increases in direct relation to the decrease in area. Wedge - A wedge-shaped downward projection at the bottom of the transom resulting in a built-in hook. Designed to lift the stern of a semi-planing hull and reduce power requirements. Wetted Surface - The area of the boat hull in contact with the water. See Waterplane. Wharf - A pier or dock. Windward - On the side towards the wind or from which the wind blows. See Leeward. Yacht - Any type of pleasure boat, especially in the luxury class. Yaw - A deviation from a straight course. Back to top & close Fiber Facts: FiberFact #1 Beginning One of the first apparent uses of fiberglass was in radar domes at the end of WWII. General Electric was using fiberglass to build radar domes. The world's first fiberglass boat appeared at the 1946-47 New York Boat Show. FiberFact #2 Resin types There are two basic resin types: - polyester - epoxy 99% of boats built are of polyester resin because they are: - cheaper, and - cure time can be adjusted Polyester resins come in three categories: - orthophthalic - isophthalic - vinylester The majority of boats were built with ortho resins, although some high performance use iso and vinyl. Epoxy resins are better glues than polyester resins. They are stronger, and some can actually cure under water. The problem with epoxy resins are: - 4 to 5 times the cost of polyester resins - harder to handle - mix is exact and can not be adjusted to change cure times. FiberFact #3 Polyester Polyester (the one 99% of boats are built with) comes in two types; finishing abd laminating. Finishing is used for most small jobs using a single layer of cloth or for the final layer of glass. Laminating DOES NOT DRY TACK FREE, and so is called air inhibited. It is used to build up success layers in construction and big repair jobs. EPOXY CAN BE USED TO REPAIR POLYESTER......BUT!!!! POLYESTER SHOULD NOT BE USED TO REPAIR EPOXY. FiberFact #4 Glass Fiber Material There are a number of different styles of fiberglass materials used in new construction and repairs. 1.) Chopped strand mat - these are short strands of glass layed randomly. This cloth has equal strength in all directions. It is considered the most adhesive, the most watertight, the most easily molded, and the most versatile. 2.) Woven roving - looks like coarse cloth or burlap. Strands are layered perpendicular to each other so it is high in strength at right angles, and weakest at 45 degree angles. 3.) Unidirectional roving - strands all run parallel. 4.) Fiberglass cloth - much finer texture than woven roving. Used for interior fininshing. 5.) Strand roving - heavy strands of 100 or more continuous fibers packaged on spools. Can be laid into sharp cornerss, depressions, etc. Strand roving is the material fed through a glass gun, chopped, and srayed out with resin when building new boats. The recommended width of these materials when one person is doing the work is 38". FiberFact #5 Molds Essentially all production glass boats are built using molds. These are highly polished surfaces coated with a releasing wax. The first coat (and outside of the boat!), typically gel-coat, is sprayed onto the mold about 15 - 20 mils thick, then the boat is layed up from the outside in, typically 2 - 4 layers of fabric at a time in alternating layers. When removed from the mold, the exterior needs little or no work except trim paint. FiberFact #6 Joinery methods Click on the links below marked "helpful image" to show typical deck to hull joinery methods which may help you take apart your Glassic. Reference: The Fiberglass Boat Repair Manual, Allan H. Vaitses, McGraw-Hill - International Marine; Camden, Maine; 1988 FiberFact #7 Gelcoat vs. Paint Gelcoat: Most production boats produced using molds (many boats produced from 1 mold) have been finished (actually started!) using gelcoat. Gelcoat easily lasts 10 years looking great. Most paints or coatings last half as long as gelcoat. Paint: Painting is the usual way to finish a "one-off" form built boat (1 boat made per form), or it is the way to refinish a boat whose gelcoat is worn or damaged. Awlgrip and Imron are examples of slick/durable paints. FiberFact #8 Restoring the Finish Gelcoated boats, if cleaned, waxed and polished will look nearly new after 10 years, and not bad enough to restore after 20. If they're old or really dirty, more heroic techniques are needed. 1.) Compounding - is polishing with a paste containing a fine grit. Pastes come in varying size grits. Try the smallest possible, and work to coarser grits until you get the result you want. Make sure you remove any old wax. Use acetone on gelcoat in reasonably good shape to remove wax. Use a toluene based wax removal product if you've used silicone based wax. Use a polisher with a soft pad to apply and polish. Work in patches. If you don't get the results you want, it's wet sanding next. 2.) Wet Sanding - uses emory paper kept constantly wet. Emory paper (aka wet/dry paper) comes in 100 to 600 grit; 100 is coarsest, 600 finest. Use the finest possible to get the color back, constantly rinsing and wetting the paper and surface. Then work back up through the papers to fine grit and finish with compounding and polishing. If you still don't get the results you want, it's time to refinish!! FiberFact #9 More Serious Surface Repairs Repairing a scratch, dig, gash, etc. (Or also could be titled look out for the......NAIL!!!!) If your gelcoat is generally ok, and you have a small repair, the best thing to do is repair the gelcoat. Remember, gelcoat is resin with pigment and additives to resist wear and weathering. It is the best finish for glass; better than urethane paints and better than marine paint. As supplied from the vendor, resin is meant for spraying or painting on in thin coats (~20 mil max thickness when done). Gelcoat will not stay where it is applied in any thickness because of its thin viscosity. So...you make gelcoat putty out of it. Conversely, you can buy a gelcoat repair putty. 1.) Start with a gelcoat resin that matches your color as closely as possible, and then add pigment to get to the finished color. 2.) Thicken the resin with talc from a paint store to a good working consistancy for the repair you need to do. Make extra! Stored properly (in the dark, where it's cool, and air tight) this mix will last upwards of a couple years. 3.) Working in small batches, catalyze some test batches until you get a cure time >0.5 hour and < 1.5 hour. You need to ensure you mix the catalyst in extremely well or you may well get a bad cure. This is harder to ensure for putty. 4.) The gelcoat repair WILL SHRINK a little!! Although psychologically hard, it is best to not overfill the repair, but rather bring it up flush with the surface the first time, sand it off when cured, and hit it again, sanding down to a flush finish. 5.) Sand and polish the repaired area to blend in with the balance of the finish. Good luck!! FiberFact #10 Re-Gelcoating vs. Re-Painting When gelcoat is beyond repair you have 4 options: 1.) re-gelcoat the boat 2.) re-paint the boat with a polyurethane paint (e.g., Awlgrip or Imron) 3.) re-paint the boat with conventional marine paint (1 or 2 part epoxy paints, alkyd or modified alkyd enamels 4.) too ugly to mention.......yet Option 1 - Gelcoat There is no better protection for fiberglass than gelcoat...period. It bonds chemically with the underlaying fiberglass. It goes on much thicker than a paint finish. It can look good for 20 years. HOWEVER, no one makes gelcoat that is self smoothing. It is labor intensive to apply and to polish up to a high gloss shine when applied to exterior surfaces. It will not, on its own, dry to a high gloss finish. It takes a lot of labor to sand and polish a gelcoat finish to a high gloss shine. Option 2 - Polyutethane paint Imron and Awlgrip will last half as long as gelcoat, and because the finish is thin in comparison, is more subject to marring than gelcoat. These paints go on and dry to an incredible shine, almost wet looking. There is no need to polish the finish. HOWEVER, they are very tricky paints to apply well. They need a moisture and dust free environment. They contain materials that are quite hazardous to health so proper ventilation must be used. They are very expensive, probably in excess if $100 per foot to apply. And when applied over fiberglass, an epoxy seal should be laid down before the urethane paint. Option 3 - Marine Paint This third option is often overlooked for refinishing fiberglass. It shouldn't be! Marine paint is a great choice for fiberglass refinishing. These paints are far more durable on glass than on wood. They will look good on glass for years; not as long as urethane, and certainly not as long as gelcoat, but also at a fraction of the cost and labor. These paints are cheap compared to options 1 and 2. These paints also are not difficult to apply. They can be water sanded to a high gloss finish. Do not make your decision without checking out option 3 and giving it some consideration. Option 4 - Navy Target. Barrier reef addition. Salad bar. (You get the idea!) FiberFact #11 Putty in Your Hands! Ever seen cars with Bondo and primer gray? Hey...it's fiberglass! Yup...Bondo is polyester resin based putty. There is little difference between Bondo and gelcoat putty (discussed in an earlier FiberFact). Biggest difference is Bondo has no pigment (color), and is easier to sand. Gelcoat putty is more brittle and weaker than Bondo. So...if you have a lot of big gouges, large areas to fill in, etc., use Bondo. If you are re- gelcoating, bring the Bondo to just below the surface and finish up with the more expensive gelcoat putty. If you are painting, use Bondo all the way to flush with the finished surface, then sand and paint. You can buy Bondo is just about any auto parts store. FiberFact #12 Gelcoating I If you already own your glassic, you will probably never apply gelcoat the way builders do; that is from the outside in. You might though, if you are repairing a hole, but more about that in later FiberFacts. Builders typically spray gelcoat against a highly polished mold, and then "build" the boat from the outside in. So the finished side of the gelcoat (during contruction) is actually against the mold and never seen until popped from the mold. The smoother the mold the better the finish when removed. As a boat owner, we are standing on the outside saying "What the !@#$%^& can I do to make this look good?! Gelcoat, from an earlier FiberFact, is orthophthalic or isophthalic resin. Epoxy is NOT gelcoat, and vinylester resin is too much $$$$$$. WARNING UP FRONT - WHEN CATALYZING GELCOAT, YOU MUST MIX IT THOROUGHLY. FAILURE TO DO SO WILL RESULT IN UNDER CURED AREAS, AND A TOTAL MESS ON YOUR HANDS. FiberFact #13 Gelcoating II - Exterior Application Gelcoat applied to the exterior of a surface will not dry like gelcoat sprayed to a mold surface. It will tend to dry as applied. Gelcoat is NOT paint. It will not self-level. Re-gelcoating large parts, hulls, etc. is VERY labor intensive because of the sanding and polishing AFTER the gelcoat has dried. I'll say it again though, there is NO better finish. The trade-off is the level of shine you're willing to accept for the labor or money you're willing to perform or pay for. You can roll on gelcoat to a well prepared surface (after fairing and smoothing) and get a great color job, that is very good looking and highly wear resistant. It just won't be shiny. But you can sand it and buff it (for a lot more labor/$$) if you want. FiberFact #14 Gelcoating III - General Rules 1.) If you are using a backing material (say for a hole repair) or building a part using a mold, apply a few coats of mold release wax, letting it dry between coats ~ an hour. 2.)You may want to perform a compatabilty test with your materials (backing, wax, and gelcoat) to make sure you get good release and no odd chemical reactions. 3.) Protect areas you don't want gelcoat on. Use wax, tape, newspaper, etc. 4.) Tend toward the high side of the manufacturers recommendations on catalyst, and mix it extremely well......then mix it again. Pooly mixed gelcoat will yield gooey non-curing parts!! 5.) Make sure you know whether the gelcoat you are using is air inhibited. If it is, you will need to seal it from air to get a good cure. 6.)You can thin gelcoat using acetone and spray it on. Start with the hardest to get to areas and work to the easiest. Keep a wet edge, and when done, go back and repeat at a diagonal or perpendicular angle to the first pass. A total of three passes should give you the recommended 15 - 20 mil thickness. Caution!! Acetone is highly flammable. DO NOT SMOKE OR USE ELECTRIC TOOLS IN YOUR WORK AREA!! FiberFact #15 Layering Up Glass Laminate (I) Here are some general rules of thumb to consider when layering up glass. This is in two parts. See #16 for balance. 1.) Protect areas you don't want resin on. Newspaper and masking tape work well. 2.) Set up your work area to include: - table for cutting fabric - lay down a piece of plywood for cutting fabric - set up an area for dispensing resin, catalyst and mixing - have an eye wash station handy in the event you get resin, or God forbid, catalyst in your eyes - have a tool cleaning/hand cleaning area - a 5 gallon pail with acetone or laquer thinner (a lot cheaper) works well. Note: the fumes from acetone will dissapate faster than laquer thinner. 3.) NO FLAMES, POWER TOOLS, IGNITION SOURCES PLEASE!!!!! 4.) Cut all your fiberglass materials ahead, and stage them in the order you will need them. Use rolls 38" wide. 5.) Use small pieces, not big pieces. For vertical sections, about 2 sq. yds.; for horizontal secitons slightly large; for overhead work use smaller. 6.) Butt the joints when applying OUTSIDE. Overlap the joints when applying inside. 7.) When tapering a patch, start with the SMALLEST piece first, anda then work out to the largest. This prevents your patch from being totally dependent on the first piece you lay up. 8.) ALWAYS start with MAT glass (see prior FiberFact for material description). It will give you the besst adhesion. 9.) Never laminate over glass that has not been recently sanded, unless the glass was laid up in the prior 24 hours. FiberFact #16 Layering Up Glass Laminate (II) 1.) Always paint a surface with resin before putting on the material unless the surface is pretty wet from prior layers. 2.) Catalyze only small amounts of resin in ~2.5 qt NON-WAXED paper buckets. This allows you to adjust the catalyst for the area you're working, and won't cause you to lose much resin if it gels before you can apply it all. 3.) Use throw away tools to apply resin; cheap brushes for small areas, and high nap rollers for big areas. 4.) Use a hard knobby rollers or grooved aluminum rollers to roll out the glass. This gets rid of the entrapped air and thoroughly wets the glass. 5.) Presaturate small pieces on a piece of pasteboard, then put them in position. They'll mold very easily into shape. 6.) Work 2 layers at a time for larger areas. More in small areas. More layers will actually cure faster than fewer layers. The curing process is an exothermic reaction (i.e., gives off heat), so the more material, the more heat, the faster the cure. But be careful that on hot days and working many layers you don't cook the resin. 7.) Wash your tools often with acetone. And remember that MEKP catalyst and acetone are both volatile and flammable. SO NO IGNITION SOURCES!!! 8.)PROTECT NEWLY GLASSED SURFACES FROM MOISTURE INCLUDING DEW. Use polyethlene sheets or mylar sheets. 9.) Do not glass over a dripping leak in a boat. The water will make a path through the glass and it will not cure. 10.)Ventilate your work area very well with fans. 11.) Work the small detail areas separately from the large areas. You will need to slow down and spend more time with the small areas. FiberFact #17 Cores A core is a bulky, stiff material placed between fiberglass layers. A core stiffens, provides sound insulation, absorbs vibration, and insulates from heat and cold. In order to retain these properties, core materials MUST be bonded to the glass laminates on both sides. Layering core material into a pool of resin wont work. Core materials should be pressed and weighted into mat fiber, and then another layer of mat used on the other side. Thoroughly roll out the matting to remove entrapped air. Wet your core material too. Porous cores require more resin than non-porous cores. Some core materials are designed to dissolve chemically in the resin which makes a great bond. However, be careful not to over wet these core materials or you can damage them. FiberFact #18 Cutting and Grinding Safety In light of the recent AeroCraft Satellite photos, I researched the safety of cutting and grinding...just in case Kevin (and Guido if he's looking for free beers) may have to do some in the future! The best type of grinder for readying an area for repair is an open wheel disk grinder. The downside of this fact is that this tool spews glass fibers and disk pieces at random. So: 1.) NEVER GRIND FIBERGLASS WITHOUT A STOUT PAIR OF SAFETY GLASSES ON WITH GOOD PROTECTIVE SIDESHIELDS, OR PREFERABLY A PAIR OF SAFETY GOGGLES. The dust can cause serious irritation, and the grinding disk can release pieces without warning. 2.)DO NOT WEAR GLASS LENSES IN YOUR GLASSES THAT CAN SHATTER ON IMPACT WITHOUT GOGGLES OVER THEM!!! 3.) Disks can be controlled as to where they give off their grinding debris. Experiment on wood and learn the technique of directing the debris away from you. Debris exits a grinding disk in the direction of rotation, so you have 360 degree control of where the debris goes.....dependent solely on where you allow the disk to touch down. 4.) DON'T BE A HERO. AS GEEKY AS THEY SEEM WEAR A GOOD RESPIRATOR DURING GRINDING. FIBERGLASS FIBERS IN THE LUNGS CANNOT BE A GOOD THING. 5.) Do not wear surgical masks. They do not seal at the mask skin interface well enough. 6.) Wear as least a toxic dusk mask. 7.) Glass fibers themselves are not irritants to skin. Rather, it is the fiber ends that cause skin irritation. 8.) Wear either tyvek or paper suits during grinding. DO NOT WASH YOUR CLOTHES IN A WASHING MACHINE USED FOR THE FAMILY. YOU WILL CONTAMINATE IT WITH FIBERS!! And, really piss off your wife! 9.)If not sweaty, the best way to clean yourself is with a vacuum cleaner. Actually vacuum off the fibers. Then wash with cold water. You want to keep the skin pores closed to preclude entry of fibers. Be safe, not sorry!! FiberFact #19 Grinding There are 4 principle reasons for grinding areas to be repaired: 1.) To cut away damaged material so what's left to attach to is sound. 2.) To grind a drepression so that patches are built up in tapered layers to the original surface. Done properly, a repair will be barely visible. 3.) To taper the edges of a repair area so that you end up with a scarf joint, not a butt joint butt. A scarfed joint provides more surface area and strength. The more the joint can be spread out, the stonger the joint. 4.)To remove wax, polish, grease, pait, gelcoat, etc. so that a strong bond can occur. In testing, the strongest bond that can be made is one where the fibers of the original laminate are paritally exposed by grinding, but are then partially pulled up out of the laminate by layering on heavy cloth and them ripping it off before it cures completely. The best grinder to use is a 6 - 8", heavy, right angle, high speed industrial grinder with coarse cloth backed disks (#36 or lower). The coaser the grit, the faster the removal. These grinders can also take cut off wheels for removing bad sections. Grinders, especially with coarse disks, are very dangerous. They can release material or fly apart with no warning. Wear safety glasses/goggles. Don't be a hero! FiberFact #20 Repairing Holes In case someone might have an AeroGlass Satellite needing a little more drastic work.......... If damage includes a hole through the laminate, the best repair is made by backing the area (either inside or outside)with stiff (but flexible) sheet material against which you do the layup. If you can get to the hole on the inside of the boat, then the best way to apply the backing is to the outside of the boat, and do the repairs from the inside. Ensure the backing has a smooth, waxed surface. Your finished surface will mirror it, eliminating a lot of sanding to blend the repair area. Step by step...we start! 1.) Grind all the edges of the hole on the surface opposite what the backing will be applied to. Make sure you grind/cut away any lose pieces or material. Taper the edges of the grinding 12X the thickness of the laminate you are repairing. For a 1/4" laminate, grind out to 3". For a 2" hull bottom, grind out 24" from the hole edge. The ground out area should mimic the approach down a beach to the ocean, giving you the ability to layer successively larger pieces. 2.) Protect the area around the repair where the backing wont be by waxing it heavily. 3.) Apply the backing material ensuring you apply a large enough piece to capture the curvature of the piece. Too small a backing will end up with a flat spot in the repair. For large holes or complex curves, try cutting the backing into strips and applying them horizintally. You'll get a much better fit. Put scotch tape on the seams to keep resin from pertruding, but recognize you will probably have some sanding to do. If you use strips, you will not get flat spots in the repair. 4.) Next, wax the backing surface very well. Keep it as smooth as possible. 5.) If gelcoat is the outside layer, apply about 15-20 mils, matching the color as closely as possible, and let it cure. 6.) After the gelcoat has cured, apply 2 layers of MAT material, and allow it to cure completely. 7.) Next, start building in the repair with your schedule of materials. Do not work more than 4 layers at a time, or the exothermic reaction may create too much heat and cook the resin. 8.) Remember prior FiberFacts; cut all your materials in advance, and make each succesive layer slightly larger, matching the grinding taper. 9.) If building from the outside in, finish with material that matches the finish. If building from the inside out, finish with 2 layers of MAT. 10.) Stop 2 layers from completion and grind and epoxy any problems that have built up during the repair, then finish off. 11.) Remove the backing, sand, polish and wax. PIECE 'O CAKE!! FiberFact #21 Core Construction (I) Different core materials produce laminates of differing characteristics, including the ability to be able to be repaired. The best core material to use today if you are building new, or making a new member is PVC (polyvinyl chloride) foam. It is an excellent heat and sound absorbant material, resin sticks well to it, and best of all, IT ABSORBS NO WATER IF WETTED. Problem for Glassics is that about 80-90% of boats built from the mid-60's to the 70's used balsa wood for core material. And, prior to that plywood and other woods were used as core material. Note an exception to 50's Glassics is the Crosby Boat line, which used balsa wood in its contruction. If these wood cores get wet, or worse saturate, and then heat, freeze, etc., this can delaminate the laminate. If left uncorrected, the core over a number of years will turn to mush and be pretty useless. More later. FiberFact #22 Core Construction (II) - Delamination Delamination is the separation of fiberglass layers (rare) or the separation of a fiberglass layer from a core material (more common). It is frequent with cored contruction that delamination occurs with no visible external damage being observable. In a solid fiberglass piece, this type of delamination is unlikely because the bonds between the layers are very stong. The resin-core bond, unless the core is PVC, is weak comparatively. An all glass part may crack or break before it delaminates. A cored piece will sheer between layers to release stress. Delamination can occur from water infiltration and then freezing/thawing, sharp blows (i.e., jumping onto a deck, dropping a heavy object onto a piece, etc.). You can detect delamination by "sounding". That is, tapping lightly with a hammer and listening for differences in tone. This is similar to sounding for a stud behind sheetrock. A failed laminate will sound different than an intact laminate. You can also see lamination problems. Look for softness under foot when walking, or if you see marks in your hull after your boat has been on a trailer or in a cradle, could be there's a problem. . FiberFact #23 Core Construction (III) - Repairing Delamination I wrote earlier about sounding and observable core damage in #22. Here's a little more info. A Crosby Seaquin I looked had all the classic signs of delamination with very serious core problems. 1.) Bubbling/blistering of the glass over the core on the inside of the boat. Bubbles were visible. 2.) A "squishy" feeling when walking on the floor. 3.) A "dull" sound on "sounding" the floor. Almost like knocking on an open book where there was give and no "ring" to the knock. [In comparison, I sounded my 58 Crosby Capri and these soundings were like rapping on solid wood...sharp sounds, and almost a ring to them.] 4.) Upon inspection of the underside where the rollers contacted the boat there was a clear indentation in the glass. The balsa wood core had taken on water and was totally rotted, and the hull was unable to support its weight, to the point of actually cracking in an effort to relieve stress. To repair something like this is possible. But you need to: 1.) Remove the topsides if there are interferences. 2.) Cut away the interior skin and remove it. 3.) Remove the core material and dry out the removed skin and hull. 4.) You may want to consider a layer of MAT/resin here, especially if you need to reform the hull in any way. 5.) Re-install new core. Bed it with MAT/resin. Highly recommend PVC foam core so your grandkids won't have to do this repair too. 6.) Re-install inner skin. Use old skin and pour resin to fill voids and use material and resin on cut joints, or lay up MAT layers and make a new skin. Think ahead about any stringers you may want for fastening seats, etc. Good luck! . FiberFact #24 Core Construction (IV) - Repairing Delamination If you are lucky, and your area of delamination is dry, repair will be pretty simple. If you are unsure, drill some test holes in inconspicuous areas and check for wetness. If the core is wet, this method will not work for repair. However, if your area to be repaired is dry, you should have good luck. 1.) Set up your piece to be repaired parallel with the ground if possible. [You're going to need gravity working for you.] 2.) Get a length of threaded pipe. Drill a hole in your piece to repair at one side of the delaminated area and thread in the pipe. This hole should be set up higher than than the vent holes discussed below. Wax the area around the fill hole. 3.) Drill one or two vent holes at the other side of the delaminated edge, and lower than the fill hole. Wax the area around the vent holes. 4.) Next, blow in the pipe and see if you can force air through the area to be reglued. If you can't, continue adding small vent holes. Do not use an air compressor for this as too much pressure can force your layers apart even more! 5.) Fit a piece of hose and a funnel to the pipe. 6.) Pour in the resin with catalyst all mixed. 7.) Raise the funnel to force the resin into the delaminted area. Each foot above the repair area adds 72 pounds per square foot pressure. Don't go too high so as to cause a bulge. 8.) You may want to think about shape retention by using weights, etc. 9.) Keep adding resin until resin issues forth from the vent holes. 10.) Remove pipe and smooth resin in fill hole. 11.) Allow to dry thoroughly and finish. . FiberFact #25 From Under the Hull - Advice I want to share with you a conversation I had sitting on the ground under a 45' cruiser at the Essex Boat Works in Essex, CN. The Essex Boat Works is truly a shipyard, able to handle REALLY big boats. What caught my eye first was the size of the boat. 45' of fiberglass out of the water on blocks with a fly bridge is hard to miss! As I walked toward it, the way the finish shined told me it had to be new. But the man laying on the ground helping to bolt home new drive shafts and hangers said it wasn't. Turns out this boat had been sitting on the bottom months earlier, the victim of a faulty check valve in a fresh water system. The boat had been brought up and restored, including a complete hull refinishing. The size of the drive shafts being installed were as big as my arm. We got to talking about fiberglass repair and finishing. This man has been in the business for over 30 years, and talked with the calm knowledge of someone who truly knows what he's doing. Here's some advice he offered me. 1.) Gelcoating is for new boat construction. He said that while he has personally re-gelcoated a 33' sailboat, money better not be an option, 'cause it will cost a bundle to pay for the labor involved. 2.) The old boats we love so much were made of products inferior to those available today. He said the paint products available today are tough and durable, and will last for decades if protected from sun fade. He also said these products are truly impervious to water, which is not the case with fiberglass. 3.) If you're doing the work, follow the directions EXACTLY as they are written. If there's a difference in thinners recommended for specific temperatures, use the right one. Todays products are the products of chemists. They know what they're doing. You are essentially running a chemistry lab on your boat's hull. 4.) If you're painting the product on the boat, DO NOT PAINT STEM TO STERN. PAINT UP AND DOWN!! These paints will tend to sag a little when applied. Paints applied stem to stern will show the sags. Paints applied top to bottom will not. 5.) He said that if you need to spot repair a boat (remember those dock crushers!!) you'll have less and will get a better job with repainting rather than trying to match gel-coat color and get the shine to match too. I wish I could give you all the feeling of grace this man had. He was willing to sit and share as long as I was. He was willing to teach and give advice. It made the "John Courage" at the Griswold Inn up the hill from the Essex Boat Works taste all the better that night! . FiberFact #26 Repairs to the Overhead A few weeks ago on the message board someone posted the question of repairing a rotted core in a deck or overhead of a cabin. By all means the easist method is to attack the repair from inside, leaving the gelcoat intact, if possible. Cutting away the inner skin and replacing it will me much easier than re-gelcoating, matching colors, shining it to match, etc. Here are a few tips. 1.) Cover everything below where you'll be working with resin proof plastic. 2.) Use a high nap roller to apply the resin, not a brush. It will drip less. 3.) Wait until the resin gets a little tacky before applying the glass cloth. 4.) Instead of applying mat to the resin in the overhead, try applying the resin and mat to the core on a work surface and build it up. Then, shore up the core piece, wetted to seal with the gelcoat. Then, apply resin and strips of cloth around the seams to tie it all together. You may need to grind back a rabbet to blend this in. 5.) Alternatively, wet the back side of the gel coat, get it tacky, and then lay the mat. Then, place the core in place and shore it up. Continue building up the cloth layers after the core has set up. 6.) Work smaller pieces than you would working on a surface on a deck. Good luck! . FiberFact #27 Installing New Core and Outer Skin From the Outside If you need to accomplish core replacement from the outside, you probably need to match up non-skid surfaces, deck patterns and gelcoat color. You should begin by assessing the area needing to be repaired. Is it small and by itself? Or, is it a small part of a large area? Or, is it a large area? You may want to choose a different approach for each of these situations. 1.) If you have a small area by itself, you may not need to worry about matching gelcoat color closely. So, you can handle the repair in a straight forward manner. 2.a.) If the area to be repaired is a small part of a large area in otherwise good shape, matching designs (i.e., non-skid surface, deck designs, etc.) and color is essential for a good job. For gelcoat color matching, you can experiment by adding your color pigment to your resin, and then take a small amount of resin, catalyze it, and apply it to a piece of test fiberglass and let it dry. Check for color match. If not right, go back to your resin pot again, adjust the pigment, take a small sample, catalyze, apply to test piece....ad nauseum until you get the color match right. Then....protect your resin from heat and light and it will last for several years. Only catalyze the amount of resin you need. 2.b.) If you have a pattern you need to include in your repair area, you can make a mold from an area that is in good shape. Clean the area to serve as the mold well. Tape off and protect surrounding areas. Thoroughly wax the mold area with release wax. Spray or brush on you color matched gelcoat resin. Remember, brushing is ok because the smooth surface is the surface towards the mold, not where you're brushing. When the gelcoat is cured, apply a single layer of MAT fiber and concentrate on getting ALL of the air bubbles out. Then, once cured, apply additional layers until you have a thickness that will retain it's shape, then remove the mold. Repeat this until you have enough of the mold to complete your repair. You may to need trim and fit and sand the edges of the mold pieces to lay up the final layer. 3.) For large areas, assess the whole area. If it is crazed, cracked, or faded, you may want to grind out the whole area, replace the core and then lay up an all new top layer. Good luck! . FiberFact #28 Hull Desaturation Options Seems like a number of us have found old boats with saturated (i.e., waterlogged) cores. A saturated hull's core is repaired the same way as a saturated deck. There are a number of ways to accomplish the job; some 4.0, some 1.5. Depends on what you want out of the boat. 1.) The best way is to remove the inner skin, rip out the bad core, replace it with new core material and replace the inner skin. In some old boats I've found (Flying Scott and a Crosby Hurricane), this is a simple decision. The seats are gone, and you're left staring at the inner skin anyway. In a Crosby Seaquin I found, this really means separating the topsides and molded front seat section off the hull in order to get to the inner skin area. Big difference in level of effort required. 2.) The next best method is to remove the inner skin and try to dry the core using warm air, heat and/or acetone flushes. This may take some time to accomplish thorough drying. For a restoration, most of us have this time. Frankly, I think I'd get bored waiting, and would probably opt for #1. 3.) Not recommended for a restoration, but still an option is to drill a number of holes in the skin and subject the whole boat to drying. This will take even longer to dry than method 2. Once dry, plug the holes and add 2 layers of additional MAT to the inside. 4.) Not recommened, but still an option is to ignore the saturation. Repair cracks and holes as needed, and drain excess water and let dry as much as possible. Then add two layers of MAT outside if the outer skin is too flexible with the mushy core. Then, add PVC foam disks between the skins and especially in large unsupported and flat areas. You may want MAT layers inside also. This makes the two skins independent of the core that used to do this work. But I wouldn't expect the hull to perform like the designer envisioned. I personally would reserve this method for skows and work boats, not a rare Glassic. . FiberFact #29 Safety Notes The materials and equipment we work with to repair and restore Glassics are hazardous. I have tried in FiberFacts to include cautions on equipment and materials when necessary. Here are some cautions, again. Large disk grinders, saws, sharp tools, etc. can inflict serious wounds in the bat of an eye. Keep your tools sharp (you won't fight them as much), wear gloves when possible, and keep a first aid kit in your work space. Think of your shop as an industrial area. Think about and incorporate similar safety strategies. Light your repair area well. Being able to see well is critical to safety. And, wear eye protection when cutting, grinding, etc. Many of us use halogen lamps. They are cheap and very bright, however, they generate incredible amounts of heat. NEVER LEAVE HALOGEN LAMPS ON IN YOUR SHOP UNATTENDED! If using halogen lamps to heat an area on your boat, stay with it and monitor it. Halogen lamps have caused many devastating fires. Fiberglass fibers are irritants. Wear respiratory protection, eye protection, and cover your skin as much as practical when cutting, grinding, sanding, etc. Tyvek suits are cheap, re-usable clothing. Invest in a good respirator....DO NOT USE SURGICAL MASKS....THEY ARE INEFFECTIVE! Many of us are weekend warriors, and may not be in the best of shape. We work in cramped spaces, odd angles, hold heavy equipment for long periods. And we have limited time to get things done with everything else going on in our lives. Monitor yourself as you work. Check your pulse and respirations. Wearing tyvek and working will heat you up quickly. Watch your back. When you feel tired...stop! Rest a while. Accidents are far more likely to occur if you are fatigued. Drink lots of water - NOT ALCHOHOL - while working. Alchohol will dehydrate you further. Save the beer for a stroll around the boat after you've cleaned up! Be careful of electricity. If working around the waterfront, every electrical circuit should be a ground fault circuit. It could save your life. If you need extension cords, make sure you are using one heavy enough for the equipment you are using. Make sure that your electrical equipment has all the insulation in good shape. Be aware of your total load. If you have a shop, how is power fed? Are the outlets off your main panel? Most household circuits are rated for 15 amps. If you are plugging a couple of halogen lamps, a grinder, radio, normal shop lights, etc. into this circuit, you could be pushing the limits. Consider a 50 or 100 amp sub-service to your shop area. This will get power to where you need it, and then you can add circuits to distribute the load, and minimize the need for long extension cords. Fire safety is paramount. Resin, catalyst, acetone, thinners, cleaners, etc. are all highly flammable. Ensure your work area is well ventilateed to dissipate fumes. DO NOT SMOKE IN YOUR WORK AREA!! Be aware that mixing resin and catalyst creates and exothermic (i.e., gives off heat) reaction. Fiberglass will heat up as it cures. The thicker the new glass layer, the more heat will be generated. Don't lay up more than 4 layers at a time. Too much heat will cook the resin and spoil the job. Think twice before adding heat lamps to make the cure go faster. The heat from the reaction and the lamps may be too much. Be cautious of rags, resin buckets, and container closure at the end of work. Close all containers tightly. Spread out rags to dry. Donot store them in a heap. Preferably, hang them outside. Use disposable resin buckets. At the end of work, take the resin bucket outside to an open area and let it harden. When cool, throw it away. Think about fire safety. Is your shop connected to or separated from your house. If it is connected, does the area have a smoke/fire detector(s)? If not PUT ONE IN!! And, wire it such that if one detector activates, they all ring. If your shop is detached, you may still want a detector that can activate your house detectors if you have a problem. Accidents can and do happen. Review your insurance policy. Is it up to date? Is your policy automatically inflation adjusted? Does it have "full replacement value" or "prorated value". For a few extra dollars you can have full replacement value. It's worth it...trust me. Does your policy cover your Glassic(s). You may need a rider to recover the true value vs. book value. Attached are photos from a Glassic restorer. The first shows a '57 Crosby Capri shortly after re-decking. The next shows the boat the next morning after a devastating garage fire. It can and does happen. Hey...be careful out there! Back to top & close Boating Fundamentals: Some fundamentals anyone? Click the images below, each opens a separate window. Back to top & close What's my boat worth: Yea yea, what's it worth? Let's try to answer that... (sort of, stay tuned) Back to top & close Long shaft motor or Short shaft: Long shaft or short? (stay tuned) Back to top & close How Much Horsepower will my boat handle: Back to top & close About Props: Understanding your Propeller Identifying your propeller The size of a prop is described using two sets of numbers. (e.g. 14 X 19) The first number designates the diameter, and the second number designates the propeller pitch. Propeller Terminology: Diameter Diameter is the width of the circle described by the rotating blades. Pitch Pitch is the theoretical distance a prop moves forward in one revolution. The following propeller has a pitch that will theoretically result in 24” of forward travel in one revolution. However, in the real world, the propeller experiences “slippage” so that its actual travel per revolution is less than the stated pitch. Prop pitch is frequently misunderstood. Many people mistakenly believe that switching to a larger pitch prop will make the boat go faster. If a prop with too large a pitch is used, the motor simply doesn't have enough horsepower to turn the prop adequately and the RPM level drops. Not only does the boat go slower, but the motor can load up and the plugs become fouled. If a prop with too low a pitch is used the prop can exceed the manufacturers recommended RPM level and damage the engine. The ideal situation is to select a prop with a pitch that allows the motor to reach the maximum RPM suggested by the engine manufacturer without going over. If the prop selected doesn't reach the recommended RPM level, the boat will sacrifice speed and lift. Here's a simple rule of thumb to follow when experimenting with prop pitch. Remember that at wide-open RPM increasing the prop pitch reduces RPM levels by roughly 200 rpm's per inch of pitch. In other words, when switching from a 23- to a 25-pitch prop, the maximum RPM level will drop approximately 400 rpm's. The reverse is true when going down in pitch size. Propeller Cup Many of today's propellers incorporate a cup at the trailing edge of the propeller blade. This curved lip on the propeller allows it to get a better bite on the water. This results in reduced ventilation, slipping, and allows for a better hole shot in many cases. A cupped propeller also works very well where the motor can be trimmed so that the propeller is near the surface of the water. The cup will typically result in higher top end speed on one of these applications. Switching from an un-cupped to a cupped propeller will reduce your RPM. The actual amount of RPM decrease is dependent on where, how much, and the quality of the cupping. Typically, a cupped propeller of the same pitch and diameter will reduce your RPM by approximately 200. Ventilation Air from the water surface or exhaust gases from the exhaust outlet being drawn into the prop blades causes ventilation. When this situation occurs, boat speed is lost and engine RPM climbs rapidly. This occurs most often with high transom mounting, over-trimming the engine, or sharp turns. Cavitation Cavitation (often confused with ventilation), is a phenomena of water vaporizing or "boiling" due to the extreme reduction of pressure on the back of the propeller blade. Many propellers partially cavitate during normal operation, but excessive cavitation can result in metal erosion or "cavitation burn" to the prop's blade surface. There are numerous causes of cavitation such as incorrect matching of prop style to application, incorrect pitch, damage to the blade edges, etc. Rake Rake is the measurement of the angle of the tilt of the blade's tip toward or away from the gearcase. The angle is measured on a line extending from the center of the hub through the center of one blade. Selecting the right propeller The best propeller size for your boat and engine combination is based on the recommended operating range at wide open throttle (w.o.t.) for your engine, which you will find in your engine operator's manual. The goal in prop selection is to determine what propeller style and size will maximize performance for your boat, while allowing your engine to operate in the recommended RPM range. The correct propeller will prevent the engine from over-revving, yet allow it to reach the minimum RPM where maximum horsepower is produced. Run the boat/motor at w.o.t. under normal operating load to determine the maximum RPM you are able to obtain. Adjust the motor trim angle for the optimum performance. If during this test, you begin to exceed the maximum rated RPM of the engine, reduce throttle setting to a position where maximum RPM is not exceeded. If your test results in your being able to over-rev the engine, you need to increase the pitch of the propeller. Increasing the pitch increment by 1" will result in approximately a 200 RPM drop. If your testing shows, however, that you are only able to obtain a RPM somewhat lower than the maximum rating given by your engine manufacturer, you would need to decrease pitch. Decreasing pitch would increase your RPM. Once your wide open throttle RPM falls within the recommended range of the engine manufacturer, you have a propeller that is suited correctly for your boat with respect to RPM. If you use your boat for fishing, cruising and skiing, one prop probably won't do all three things equally well. It is best in circumstances like this to have two propellers; One to accommodate one set of circumstances and the other to perform best under the different load. It is imperative, however, that the wide open throttle RPM fall within the range specified by your engine manufacturer. Aluminum or Stainless? Aluminum props are the ideal choice for small- to medium-sized boats and motors. Available up to 23 pitch, aluminum props are also the logical choice for use in areas where prop damage comes with the territory. The average aluminum prop costs about $150 compared to $400-$500 for stainless propellers. Stainless steel props are more expensive, but they offer several advantages. They deliver more performance and are available in larger pitch sizes. One reason stainless props provide more performance than similar pitch aluminum models is because the steel blades are rigid and they don't flex under power. The blades on an aluminum prop actually bend when the prop is in use, reducing the overall size of the prop by approximately one pitch size. Stainless props also provide increased bow lift, especially on heavy boats. The more bow lift a prop provides, the faster and smoother the boat will ride at high speed and in rough water. Three-Blade, Four-Blade, or Five-Blade? Propellers are available in three-blade, four-blade and five-blade models. Multiple blade props came on the scene in response to high horsepower outboards that are typically mounted higher on the transom than smaller motors. Because the prop runs closer to the surface, the extra blades help to provide bite and stability at high speed The advantages of props with extra blades are they provide quicker take-offs, and allow the boat to be kept on plane with fewer engine rpm's. However, they are slower at top-end speeds. A quality three-blade prop is normally two or three miles per hour faster at top end than the same pitch prop featuring multiple blades. Maintenance Check your propeller often for nicks, rolled tips, or bent blades. Any distortion from normal will cause a loss in performance and can create vibrations harmful to the engine. A propeller with worn blades will allow the engine to accelerate beyond the recommended operating range which can result in damage to the engine. Keep the bottom of the boat clean. A fouled bottom, an accumulation of marine growth, moss and barnacles in sea water, and the accumulation of dirt, slime, lime, and other matter in fresh water, is the major cause of poor boat performance. Cleaning the boat's bottom frequently during your boating season will greatly improve boat performance. Things to Remember 1. Engine RPM at W.O.T. must be within the recommended operating range with the rated horsepower RPM as the target number (see specification in your engine operator's manual). 2. Increasing or decreasing prop pitch directly affects engine load throughout its RPM range. 3. Trim angle affects propeller performance. 4. Atmospheric pressure, elevation, temperature, and humidity all affect engine performance, which directly affects propeller performance. 5. Salt water is more buoyant than fresh water; this may cause some hulls to run faster than identical freshwater setups. 6. Water conditions can play a big part in boat performance and propeller efficiency. 7. The boat's load and position of the load can significantly affect performance. Other tidbits Hector Gutierrez wrote on Wed Aug 1, 2001 3:39:19 PST in response to a posting on props: Here is a handy little formula to calculate your theoretical speed for a given RPM. Us Mechanical Engineers have nothing better to do than to come up with this stuff. How close is your actual speed to the calculated? For my boat it was off by 1 MPH! (Prop Pitch x RPM) ------------------- = Theoretical Speed in MPH (Gear Ratio x 1056) Example: Prop size = 15" x 17" Gear Ratio 1.68 WOT = 4,000 RPM (17 x 4,000) ------------- = 38.33 MPH (1.68 x 1056) My actual was about 37 MPH Back to top & close Cable Steering Setup: Cable Steering Setup & Instructional... (stay tuned) Back to top & close Hull Types & Characteristics: This area is to show some basic known hull types in the boating industry. It doesn't cover all types because there were many many types but this should give you a general idea of the types that are used today. Below are some images depicting these types and descriptions with handling & safety characteristics. Flat Bottom - Flat bottom boats are typically small open boats such as john-boats or in some cases, ski boats. Flat bottomed boats can easily get "on plane" or ride on top of the water at high speeds. Flat bottom boats are typically intended for use on calm waters such as ponds, small lakes, and slow rivers because of the ride they give in choppy or rough water, especially at planing speeds. If they're small, flat bottomed boats are not very stable, caution should be used when moving around them. If they're relatively wide, they are somewhat stable but care should be taken when moving around in them. Flat Bottom with soft chines - Catamaran - Pontoon - Tri-Hull - Tunnel Hull - Tunnel-Vee - Vee Hull - Vee Hull with Strakes & center Pad - Vee Hull with strakes - Back to top & close What's with the pinup girls: The reason for the pinup girls... (stay tuned) Back to top & close Home  |  New Visitors  |  FAQ  |  Galleries  |  The Library  |  Links  |  Contact  |  News  |  Marketplace