TOPIC: Foam Floatation?

I'd like to add foam floatation beneath the new floor I'm installing. Does anyone know a good way to do this? Is there a good spray product? Thanks

You want to use a two part Marine foam what I did was get the deck down and screwed in place then you drill a series of holes with a hole saw (save the plugs) tilt the boat up so the foam will flow down hill and start with the low spot and slowly mix small batches of the expanding foam and fill till it seeps out of the holes. Make sure that the foam has room to flow out of the holes and does not expand and raise the floor. I got some of the 2 pint plastic containers like you get in the Deli for salads and also some 1 pint containers I filled about 5 of the 1 pint containers about 3/4 full with part "A" and 5 with part "B" then when I was ready to mix I would fill one of each into a 2 pint container and there was room to stir - then pour slowly pour into each hole one at a time . When you mix you have a few minutes but not alot. you can also run some drain pipes in before you foam so that if any water does get in it can run to the back ? When done trim off the foam that oozes out of the holes and put the plugs you saved back in and put some fiberglass over them to seal. I'm sure others may have another way but this worked well for me. Good Luck

I think Rick has explained it really well, Nautilus, here's a video that might help as well;

In the spirit of giving proper credit where it is due, FriscoJarret filmed a lot of aspects of his numerous boat restoration projects that I found very interesting and helpful.

I've also seen folks use "Great Stuff" (spray foam in a can) from the building supply stores, but there's some disagreement as to whether it's waterproof or not.

Hope This Helps

Call on your high school math to get a rough volume of what the space will hold as you don't want to over foam it by much. A little isn't bad as the holes will help the overflow, but a lot can be a problem. As it solidifies the foam in the holes starts to plug up and the expansion has no place to go - causing the bottom and floor to bow and possibly rupture... A LOT of pressure in that foam!

Another thing to consider, most use a 4 lb foam instead of a 2 lb. Some of these glassics could use a little extra reinforcing and the denser the foam, the greater the rigidity. I've done that (with the US Composites products)and it works pretty well

use pool noodles , no mess involved and will do a better job of letting water drain out should it get in there .

Use marine pourable foam only! The lower pound rated expand at a greater rate, lighter, and less strength, good for boat voids. The mediums expand less, heavier, stronger, good for mold making. The heavier pounds are strongest, heaviest and least expanding, good for structural, can even be machined.

There are a few reasons for using expandable foam to fill voids in a boat.
1. Floatation; should the boat fill with water the water cannot fill the foamed areas, enough foam will prevent sinking.
2. Condensation Prevention; unless you seal the void in a 0% humidity environment the humidity will condensate inside, needing a drain. Molds start growing in the dark moist surfaces; drains allow stuff to get in. It’ll rot from the inside out.
3. Structural; unless designed to be there, no real need if the boat is going to be used as recommended.

I foamed a void in the bow of the MR. Measured the volume with water, mixed the foam in two batches one for each side, put 4 ammo boxes full of lead on top, went inside to get a towel. When I can back out 2 minutes max…


It cuts easy with a hand saw, elec knife wooks well also.

Either from use, or storage, or condensation, moisture will get in there. Make sure there is space for the water to run toward the drain plug.
On my aluminum boat, my main reason fo using expanding foam was not floatation, but sound deadening.

This is the foam I use now, it's polyurethane closed cell foam used for setting telephone poles, fence post, flag poles, and will never absorb water, sets up hard as a rock in just a few minutes, expands 13 times it's mixed volume, weighs 9 pounds a gallon, 50/50 mix

Great info guys but it looks like it's an un-fun job! Watched the entire video...very informative. Where can I get that "telephone pole" foam? It also seems to me that maybe a better way to insure even and full distribution beneath a deck would be to cut several smaller holes (1") instead of fewer large ones. 3 or 4funnels could be used to distribute the mixture initially and those holes might allow the foam to travel better beneath the decking. Plugs could be replaced with copius 5200 and faired when cured. Your thoughts?

Don't use funnels, it restricts the flow of the liquid to the point it will set-up before you are ready, 1" holes are too small, the foam liquis builds up quick, hard to hit the hole, run's out on the top. You don't have but One Minute for get the foam mixed in in the hole, No More.
I put the wood back in the holes mainly for the reason of mounting seats, and anything else that is screwed to the floor, after fiberglassing the wood piece's back in place, it's more solid. The 5200 is a Great product, the best there is for it's purpose, but it takes it Days to cure, and it won't hold a screw very well, one more thing, it will scrink when used in the volumn it takes to fill a hole that size, not be flat.
The contact for the Secure Set foam products is listed on one of the pic's I posted

I have used the stuff you can buy at Home Depot, or Lowes, "Great Stuff" but Now, they have changed the chemical make-up of it to several different consistancies, it's not as rigid as it used to be, but it is water proof, and easy to inject, but you need to do it as you lay the floor in, so you can see where to inject the next can. although it expands rapidly, it don't cure for a couple days, and creates some pressure while curing. I didn't use the little tip that comes with the can, I drilled 1/4" holes in the floor where I wanted to inject the foam, and inserted the nozzel of the can right into the hole, the can emties in 9 seconds that way, and achieves greater expantion. A lot of folks don't know that this "Stuff" will set up under water, and is absolutely water proof.

Great thread but really zeros in on the floor flotation areas. On the Herters flying fish there is no fake floor. The only floatation is to put something under the seats, dividers, fins, gunwales etc. I'm thinking of hauling it to an insulation place and having them spray some stuff in the voids. Anyone try that?

can you flip the boat, if so, you can pout the foam wher you want it, and it would look nice and clean.

Cal I know flipping your boat now would be a little tricky, but it would make "pouring" the foam possible as Red said. Another idea: Glastron (older Glassic ones, don't know about the newer models) used some 2"x4" or 2"x6" foam "boards" in the gunnels (installed side by side, on edge) and up under the bow (flat). They were and glass tabbed/strapped in from the bottom. Might give some thought to making some "panels" or "pads" and doing it that way if you don't want to flip her over again.

The "sheathing foam" used in construction is also closed cell, won't absorb water. Just make sure you seal ALL the wood (incl. floor bottom), and provide a drain for any condensation that may form.

i use those swimming pool noodles as there is no foam flotation in the mantaray. i figure if 1 keeps me afloat (190lbs.) then 4 should keep the bow above above water. but i add 2 more and i just lash them together with a bungee cord wrapped around the deck support.pretty easy way to do it. ron

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1 ---- Pool noodle does not provide 190 LBS of floatation / bouyancy !!

There are a few insulation companies in my area, I'll stop in and get some information on different applications and processes and post. Don't like the idea of flipping again.

jim bart wrote:

Either from use, or storage, or condensation, moisture will get in there. Make sure there is space for the water to run toward the drain plug.
On my aluminum boat, my main reason fo using expanding foam was not floatation, but sound deadening.

I hear ya Jim, i dont have mush exposure to metal boats. I've seen blocks of styrofoam glued under benches for floatation. Using the sheet PVC, no rot worries. I noticed the only thing that did not mold while while the boat was covered was the PVC.

I've seen the foam installed in new construction. They spray the stud cavity and let expand. When cured its cut flush to the studs with a hand saw. Don't know how if it can be used for marine apps?

1 pool noodle keeps me afloat after i exhale. i'm 190 lbs.professor wrote:

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1 ---- Pool noodle does not provide 190 LBS of floatation / bouyancy !!

Regardless if you exhale or not your body has bouyancy. Fiberglass has none. I promise you if you take a concrete block and tie ONE pool noodle to it and drop it in the lake... It will sink to the bottom of the lake.

The human body nearly floats by itself and just needs a boost from a pool noodle !!!!!!

FYI pool noodles have a very bad habit of sucking up water. These are not really made to hold you up in the water for any great length of time. They are ok to mess around with in a pool but to use as flotation in a boat hull is just kinda asking for trouble. Also don't let your insurance company know about them. Just take a 12" piece of one and hold it under water and squeeze it. Notice the air bubbles coming out and watch it sink to the bottom as the water replaces the air. Not something one would really want in a boat. Plus the color comes out of them and will stain your gelcoat. Don't ask how I found that one out. Skip.

professor wrote:

The human body nearly floats by itself and just needs a boost from a pool noodle !!!!!!

i've tried many times to float. my body sinks like a rock..lol..but i will try that cinderblock in the spring.

skipthescrounger wrote:

FYI pool noodles have a very bad habit of sucking up water. These are not really made to hold you up in the water for any great length of time. They are ok to mess around with in a pool but to use as flotation in a boat hull is just kinda asking for trouble. Also don't let your insurance company know about them. Just take a 12" piece of one and hold it under water and squeeze it. Notice the air bubbles coming out and watch it sink to the bottom as the water replaces the air. Not something one would really want in a boat. Plus the color comes out of them and will stain your gelcoat. Don't ask how I found that one out. Skip.

i'll try that too.....

whaddya think a big agricultural tractor innertube would hold up?

You would have to calculate the volume of the tube.

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1 cubic foot of air will give you about 62.5 LBS of positive floatation.

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Do not try your pool noodle floatation theory at the local high school science fair.

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A pool noodle may give about 20 LBS of positive floatation.

In order to support 190 lbs, you would need to displace a minimum 190/62.4, or 3.05 ft^3 of water. If we assume the pool noodle to be 3" diameter with no hole in the middle, that would translate to a cross sectional area of a little over 7 in^2, or 0.05 ft^2. 3.05/.05 translates to the pool noodle being 61 ft long in order to support that weight. (The weight of the noodle is assumed to be 0). However, it is reasonable to assume that a 190# person would occupy greater that 3.05 ft^3, therefore would float on his or her own. A 6 ft pool noodle could give an assist and allow us to control our position better. Same idea as PFDs.

professor wrote:

You would have to calculate the volume of the tube.

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1 cubic foot of air will give you about 62.5 LBS of positive floatation.

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Do not try your pool noodle floatation theory at the local high school science fair.

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A pool noodle may give about 20 LBS of positive floatation.

i'm quite sure that i can put more pressure on a pool noodle than a 40lb. cinder block. hmmm... maybe a boogie board would be better. that i cannot hold below the surface. can't wait for spring.

With one pool noodle the 40 LB cinder block will sink " like a stone "

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Let us know how you make out on this experiment !!!

skipthescrounger wrote:

FYI pool noodles have a very bad habit of sucking up water. These are not really made to hold you up in the water for any great length of time. They are ok to mess around with in a pool but to use as flotation in a boat hull is just kinda asking for trouble. Also don't let your insurance company know about them. Just take a 12" piece of one and hold it under water and squeeze it. Notice the air bubbles coming out and watch it sink to the bottom as the water replaces the air. Not something one would really want in a boat. Plus the color comes out of them and will stain your gelcoat. Don't ask how I found that one out. Skip.

Seems we -have to- replace the noodles every year, after storing them over the winter and trying to reuse them they fall apart. I put a fiber fish filter on our return line on the pool filter because there where these .."things" suspended in the pool water that you could not trap with a pool net or a skimmer, looked in the fiber in line trap I made and it was the little beads of foam that are used to make the noodle. the sand filter would not trap them either, they would just pass thought it.

about the 2 part foam, I always figure 'if' you pre mold a block to fit -a- space, then sealed it with a couple coats with a resin brush that would be the ideal way to set in to the hull.

Not sure what kind of NOODLES you guys use but the ones I get are 100% water resistant being made from Closed Cell Foam. They WILL deteriorate due to not having any UV protection but being under a sealed deck I doubt they'd get much sunshine down there. Any porous material will yield air bubbles when squeezed underwater but each individual poly cell is closed and thus water tight. I have NEVER found a Pool Noodle at the bottome of my pool.

I guess maybe Not all NOODLES are created equal. Is that a Racist statement!!!!!

Wally world noodles are the worst ones out there. What you want for .99cents.

Only flotation in my MFG is the wooden keel and deck. I think I better avoid sinking altogether. My boat is kept undercover all season long and the only water in it for the last 2-3 years is from wet feet. Pool noodles under my deck would do in an emergency since it never gets wet to begin with. It is also made to let free air flow so nothing condenses. I don't want to replace my wooden keel.

If one went for a dip in the ocean you would find that a smaller pool noodle is all you need to stay afloat.

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Then visit the Dead Sea ( water at 1.24 KG / liter or about 77 LB / cubic foot) and you would find that the water there gives enuff bouyancy and you do not need a pool noodle to stay afloat.

I cut the entire bottom out of my 57-footer last year and replaced the planking with pool noodles. Floats great, quite colorful and no bottom painting.

Recently, I founded the Synthetic Cylindrical Hull Corporation and am currently soliciting investors. Private offering shares are currently being sold for $1,000. Don't miss out on this rare opportunity to get in on the ground floor or you may find yourself looking at container ships with noodle hulls in a few years saying, "I could have been a zillionaire if I had just taken a chance." But wait! Act now and you'll also get my award-winning CD, "How to pick up girls using pool noodles and basalmic vinegar." Visa/Mastercard/Paypal...whatever.

Lots of guys use pool noodles. They are under the deck so UV degradation won't be an issue. As far as soaking up water, maybe they do. How long does it take to soak up water? Take a pool noodle cut it down and submerge it in a bucket. How long will you're boat be under water? Do you plan on leaving you're boat uncovered and under a pine tree? The pour in foam will soak up water eventually too. Check out iboats, Starcraft forum. Many restorations start with a deck and then removal of waterlogged foam.

On aluminum boats the foam against the hull leads to pitting of the aluminum. In Glass it's not an issue as far as I know. Leave room for drainage though.

I've seen guys use the pink foam at home Depot too (Starcraft factory used it in the 60's-70's). Make sure it's closed cell. Remember nothing lasts forever, and I'll bet there's more than one right way. I've seen guys use plastic bottles too lol.

Question: Will pour-in stiffen an aluminum hull for better performance? I need to tackle this issue in my Starcaft 18', and I'm on the fence.

Good luck and keep us posted.

hmmm..empty 5 gallon water jugs. try and hold one of those underwater. i bet they're at least a 3 cinderblocker.

vuyosevich

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Floatation can all be calculated.

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Hopefully after this you will not be taking innocent kids out into cold / rough water thinking that 6 pool noodles will keep the boat floating !!!

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Water weighs about 8 LBS / US gallon , so a 5 gallon pail would have trouble holding up a 40 LB cinder block !

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End of coaching !!!

the pour in foams they used to use in boats for Years would absorb water if continually exposed over time, I am currently re-flooring a 1997 Celebrity and had to dig out some waterlogged foam, this hull depends on the rigidity of the foam for it's strength, that foam, as stated, will keep a boat afloat for a long time, but will eventually soak up water, even moisure, it don't have to be submerged to absorb water, a wet stringer would probably transfer moisture to the foam. On the other hand, there are a few closed cell foams that will not absorb water, like polyurethane, styrene, and polystyrene closed cell foam blocks have floated boat docks and boat house's here in Oklahoma for 50 years that I know of, and they are still floating, that foam is used under the seats of some boats, and under some decks. The foam I have used in the past, and the "Great Stuff" in a can from home depot, the rigid set stuff, will expand and set up under water, it creates a "skin" during expantion that prevents water from entering the little closed cells, but once the "skin" is broken, it may absorb water. The "Secure Set" foam I use now is a polyurethane closed cell foam, it sets up hard as a rock, bonds to everything it come's in contact with like glue, as long as it's a dry surface, and it will not absorb water, it is designed for setting telephone poles, flag poles and fence posts. I believe that if the Secure Set foam was applied to a clean dry aluminum surface, that it would not cause pitting, no moisture can get to it, but I've not tried it on aluminum boats ... yet.