# spray foam + inflatable boat = save it or kill it?



## TSOJOURNER (Dec 16, 1999)

my old metzler inflatable is still leaking and the fabric is pretty... crusty. i've applied copious amounts of various inflatable boat paints, glues, patches and unorthodox products including elastromeric paint and "barge" (contact) cement... yet she is still leaking faster than i am comfortable with. then i saw what appeared to be a "foam-filled" inflatable boat mentioned somewhere. is this a terrible idea?


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## danjarch (Jun 18, 2007)

No but the canned stuff is propably to heavy, as weel as being expensive. You'd have to do some investigating to find out what foam to use.


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## TSOJOURNER (Dec 16, 1999)

danjarch said:


> No but the canned stuff is propably to heavy, as weel as being expensive. You'd have to do some investigating to find out what foam to use.


what do you think?
"special" foam i found is this...
Boat Ship and Pontoon Foam Insulation


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## TSOJOURNER (Dec 16, 1999)

The problem I see with it, is most of the spray foams are rigid. The break when flexed. Since they would be flexing inside the inflatable pontoons they would quickly break into a bunch of tiny pieces, and water would fill the cracks. Defeating the purpose of the foam.

This is my theory only, observed from cutting overfill from around windows.


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## TSOJOURNER (Dec 16, 1999)

I thought about doing this too but never did. I quite sure the foam would be more than strong enough as it would have a 12 inch plus diamater. The problem I see is as the foam shrinks, water will get traped inside. Try it, what do you have to lose? Hang if from the rear, cut a slit in each chamber and pour it in. When it's done expanding, patch over the hole and float it.
Let us know how it works out.


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## TSOJOURNER (Dec 16, 1999)

Did I mention you woould have to use the two part pourable foam?


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## sailingdog (Mar 19, 2006)

I think you'd be better off using a small air compressor or pump to keep the damn thing inflated and then quickly glassing over the tubes...  Turn it into a fiberglass dinghy. Keep it inflated until the fiberglass cures. Then cut a small hole in the fiberglass and through the inflatable cloth and pour foam in to the opening....then glass over the hole after the foam hardens. 

A friend of mine got a dinghy that this had been done to down in the French Antilles or somewhere like that... I never laughed so hard when I first saw it—really ugly—but it worked pretty well for her.... It was built from a high-pressure, inflatable floor model, but all the inflatable bits were glassed over with a light layer of glass (a couple of layers of 2 or 4 oz as my best guess) and filled with foam.


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## danjarch (Jun 18, 2007)

I think at $700 hundred plus shipping for the foam you would need, I'd plunk it down on a new inflatable. I think the idea would work, but you could probably find a used inflatable or a nice dingy for about about the cost of the foam.


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## TSOJOURNER (Dec 16, 1999)

danjarch said:


> I think at $700 hundred plus shipping for the foam you would need, I'd plunk it down on a new inflatable. I think the idea would work, but you could probably find a used inflatable or a nice dingy for about about the cost of the foam.


good point. there is a cheaper foam available too: cheaper foam url

...however, it's not "coast guard approved."


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## TSOJOURNER (Dec 16, 1999)

The tubes are replaceable on (RHI)Avons, have you checked that Avenue? I'm not sure what you are dealing with there...maybe just go here and get a new one?!WholesaleInflatableBoats.com | Wholesale Inflatable Boats | Inflatable Boats | Rigid Inflatable Boats | Inflatable Boat


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## TSOJOURNER (Dec 16, 1999)

*any math wizards out there?*



USCGRET1990 said:


> ...maybe just go here and get a new one?!


sadly i am coming to this conclusion... after calculating square feet of this particular inflatable i am surprised to learn (if my math is correct) that it holds about 176 S.F. per pontoon!

for any math wizards out there: raft is 52" diameter X 12' each pontoon. 
please refer to the following link or tell me what is wrong with these calculations...

Frequently Asked Questions - General


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## hellosailor (Apr 11, 2006)

Area of circle = pi times the radius squared.
Pi=3.14 more or less.
52" diameter would be HUGE, your pontoons are really more than four feet wide? Or did you mean 52" circumference? Which would give you about 215 square inches (about 1.49 sq.ft.) in the cross-section of the tube. Times twelve feet long, 12 x 1.49 = 17.88 cubic feet per pontoon, let's say 18 cubic feet, for a total of 36 cubic feet of foam to fill in the two pontoons.

How much the foam expands will affect how dense the final foam is, and how bouyant. If you open the pontoon, pour in foam, let it expand and overflow out, you'll have lighter but weaker pontoons. If you fill through the valves and then seal them once the air is mainly out...you'll have denser stronger foam.

Someplace like Tiger Foam | Spray Foam Insulation Kits that sells larger kits is probably going to be cheaper than buying the quart cans in the hardware store. But taking the raft to a place that does bulk insulation (homes, etc.) and having them fill it, probably way cheaper still.

If you can dent or break or crack the foam...so what? Just get a single can, make one hole, squirt it in and glue the break together again.<G>


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## TSOJOURNER (Dec 16, 1999)

hellosailor said:


> Area of circle = pi times the radius squared.
> Pi=3.14 more or less.
> 52" diameter would be HUGE, your pontoons are really more than four feet wide? Or did you mean 52" circumference? Which would give you about 215 square inches (about 1.49 sq.ft.) in the cross-section of the tube. Times twelve feet long, 12 x 1.49 = 17.88 cubic feet per pontoon, let's say 18 cubic feet, for a total of 36 cubic feet of foam to fill in the two pontoons.


thanks so much. i just kept staring at my numbers and couldn't figure out what i was doing wrong... swapping circumference for diameter--doh!~


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## sailingdog (Mar 19, 2006)

LOL... That would be a really huge dinghy if it had 52" diameter tubes... it would also take a long time to inflate too.


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## TSOJOURNER (Dec 16, 1999)

sailingdog said:


> LOL... That would be a really huge dinghy if it had 52" diameter tubes... it would also take a long time to inflate too.


lol, that is pretty funny, isn't it?


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## TSOJOURNER (Dec 16, 1999)

sailingdog said:


> I think you'd be better off using a small air compressor or pump to keep the damn thing inflated and then quickly glassing over the tubes...  Turn it into a fiberglass dinghy. ....


'like the idea captain. and i don't care how "ugly" it comes out as long as it's good and solid (it can always be prettied up afterwards). however, i haven't got the skill with fiberglass or the several days time it would take me to do the layup. i'll check for unemployed surfboard glassers who might be interested. otherwise, i may gamble on the bulk foam method discussed on this thread.

ben


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## sailingdog (Mar 19, 2006)

Ben-

I think the fiberglassed over version, without foam in it, would be significantly lighter and easier for you to handle... however, the foam filled pontoons might be more damage resistant.


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## TSOJOURNER (Dec 16, 1999)

We tried this with a small Avon single person boat. Used loads of the cheap Wal-Mart spray can foam. The thing was lumpy and pretty much looked like a turd. It kinda worked, but the floor started leaking to the point where it was more bailing than paddling. The marina ended up throwing it away for us. 

BTW, this is what a buddy of mine planed to use to get back and forth to his boat at anchor. He ended up getting a little 2 person Wal-Mart boat that popped on him.


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## TSOJOURNER (Dec 16, 1999)

SVDistantStar said:


> We tried this with a small Avon single person boat.... was lumpy and pretty much looked like a turd...


ROFL. that is too damn funny and easy to picture as well....

ha ha ha ha...

just wondering if you put foam in all the chambers or just the pontoons? and how long was it exposed to weather (did it live in the water) before it became unusable? also, what kind of bottom treatment (paint, patches, etc.) did you use before it became a floating bathtub?

thanks

ben


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## TSOJOURNER (Dec 16, 1999)

sailingdog said:


> Ben-
> 
> I think the fiberglassed over version, without foam in it, would be significantly lighter and easier for you to handle... however, the foam filled pontoons might be more damage resistant.


i've posted my "quick cash" help wanted item for someone to glass my boat, but i'm not going to hold my breath. i like the concept, and wish i could offshore this assignment to china or india.

i'm leaning toward taking the boat (shell, skeleton, husk?) to an insulation company that does houses--as recommended above--or ordering in bulk from the best source i've come up with so far (40 C.F. for $300 includes shipping Urethane Foam , Expanding Marine Polyurethane Foam.)

if i do it myself, i'll hang the boat by it's bowline at about 75 degrees with the stern end of the pontoons just touching the ground. i'll make a sort of "beer bong" style mixing/gravity feed injection device, cut vent holes near the stern end of the pontoons at ground level and cut insertion holes near the bow. i'll attach a garden hose to the injection device, feed the hose through the nose and fill the foam from the stern of the pontoon up to the bow, withdrawing the hose as foam transfers into the pontoons... then i'll stand back and hope that it doesn't explode or catch fire


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## TSOJOURNER (Dec 16, 1999)

The only thing to put foam in was the tube. It had a thin rubber floor. There was no bottom paint or anything, it only lasted a few days. It was just total junk.


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## TSOJOURNER (Dec 16, 1999)

SVDistantStar said:


> ... it only lasted a few days. It was just total junk.


UGH. ok, so the foam may be the last-last resort before the trash heap...


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## cruisingdream (Feb 7, 2007)

Let me add one more math fact
apromx 40 cubic feet of foam to fill the dink 
weight of 40 cubic feet of foam is apromx 80 pounds
weight of dink empty is apromx 70-100 pounds 
80 pounds plus (70-100pounds) equals one heavy dink
good luck getting that up on plane or on deck


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## OlDave (Jun 22, 2018)

When the Great Stuff foam first came out I ended up with two case from a salesman.. My old rubber raft was dead and a few small holes in it and not worth fixing them all. So one boring week end i figured I would try it. Free foam leaky boat what the heck. I punched small holes around the top of it boat about 8 inches apart. I took a can can started at the first hole and just went around the boat with it. I put about a 1/4 can in each hole. Now this was a four man rubber boat cheap from a thrift store.. I let it set over night. When i came out the next morning I was happy to see it filled in pretty good. As i felt around the top of the boat I found small places where the foam did not fill in. So i punched a small hole and filled it in with a small amount. After this I filled the floor chamber. I sat back and looked at it. Not bad.. Now i know the foam floats good.. But as people have said it may fill up with water later. Well knowing this from old foam i have seen. I chose to cover the entire thing in rubber. You know the kind you paint on. Now Days they have the spray rubber coats. I then chose to place a wood float in it but when I did i chose to spray more foam over the floor and push the wood down on it.. Kind of like glue.. 
This all worked great.. I used the boat until it was stole. 
So yes it will work if you put your mind to it. I see there are allot of guys that know more than anyone else but have not put their idea to practice.. So i say unless you have tried it say nothing or at least say you it is just a guess...

I had the boat for five years.. Oh and I can not remember how many cans it took.. I did have some left over but not sure how many cans..

OlDave


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