To foam or not to foam, that is the question

[Anchoraways]

Hi there: I tore apart the floor on my 15ft double eagle to replace, and there was foam underneath. The foam was wet, and there was water still trappped under the foam. My question is, is it necessary to replace that foam? And if so, can a person just use spray expanding foam? Thank you

 

[Scott Danforth]

no a person can not use spray foam. you would need about 6 cases of it. buy the proper 2# foam (much less expensive than the cans of great stuff)

 

[Woodonglass]

To be more specific, NO you don't have too but...in the event of a hull breech, you'll be glad you did. Yes you can use spray foam but NOT from a can. Check local home and building contrators. They CAN spray foam for your boat hull, or you can buy the pour in foam to get the job done.

 

[jbcurt00]

The foam isnt the problem, leaving a boat out in the yard, uncovered, bow down or w the plug installed(esp) IS the problem..... Possibly before you got it.

Put the foam back in. There are other choices if you dont want to use pour in foam similar to what you took out. Great stuff or any typically available canned spray foam isnt 1 of the good choices...

 

[Ned L]

Obviously the foam is there for a reason. Sometimes it is 'part' structural and 'part' reserve floatation.
If you change from how it was done originally you will need to understand if it also serves any structural purpose. If you change from how it was done originally you will also need to understand if you are providing enough floatation. I.e. Using "pool noodles" (which has been done) will probable give you a boat that just goes to the bottom a tad slower than if there were nothing. (Pool noodles will not come close to the same volume as original pored in expanded foam. ... And I would consider it short sighted to think the manufacturers install much more than what is needed to pass the USCG requirements.)

 

[Anchoraways]

Thanks fellas. I got the boat as a project, the previous owner said it filled with water while docked and he pulled the floor. He mentioned that there was foam, but not very much of it. The stingers are still on good shape, but interestingly enough there's really no frame to speak of for the floor. He didn't pull all of the floor out, so you can get a good grasp of the rest of the structure. He also drilled a few small holes in the hull to drain it, which i couldn't understand why, but it's easily fixable. Got it for free, and the boat it delft is in great condition aside from the mentioned. I'll go get foam I suppose and lay it in. What's a good tool to cut the #2 foam with? I only really have knives or a hacksaw at the moment

 

[Scott Danforth]

You mix the 2# foam and pout it in.

To remove old foam, a 4" wire brush on a 2' drill extension will chew it up

 

[Anchoraways]

Well took a closer look at the inside and there's only about 1" to 1 1/2" of space between the floor and the bottom of the hull. Further inspection also revealed that the only foam that was placed was closer to the bow. There nothing under the rest of the floor. Does that seam right? I spoke the old Owens and he said the only foam removed was maybe 3ft long section around 2ft wide and around 1"width

 

[creed205]

This is an interesting topic!
I have a smaller (14") runabout that had VERY little foam in the bottom. In fact I think there was a 5" gap between the floor and the lowest part of the hull, but only about 2" of foam at it's thickest.
There are 4 cavities going front to back between the stringers (so 3 stringers and 4 spaces). Only 3/4 had foam in them. The furthest port had nothing (maybe to contract against the weight of the driver if going solo).
Also, there are no bulkheads in my boat. So I am not sure how to replace the foam with the pour in, if there is nothing from stopping it spreading fore and aft.

Any guidance would be great!
​Thanks

 

[Anchoraways]

I decided to just fill the bottom with foam, I went to my local marine place,
They guided me as to what foam to buy, and then off to Home Depot. Spent around $31 after taxes for a 2" 4x8 sheet of water repellent foam, so once the holes are finished being patched up, I'll just make templates and fill everywhere with foam. At this point i don't see the harm in adding more foam than what might have been there originally

 

[Coach Dave]

The Coast Guard Guidelines for flotation foam for boat builders can be found here: https://www.uscgboating.org/regulations/assets/builders-handbook/FLOTATION.pdf

It's worth reading. They give flotation values for different materials, and with basic math and the specs on your boat you can calculate how much foam you'll need to keep your boat from sinking to the bottom. The main key is to evenly distribute it fore and aft left and right and get some underneath your gunnels if you can.

Use ONLY closed cell foam. Pour foam is kinda expensive and tricky for a novice. I used the PINK Owens Corning XPS foam board & cut it to fit with a large retractable razor knife. XPS is the key. It is closed cell and won't absorb water. DO NOT GET EPS foam - it's usually the crumbly white stuff and probably what you took out. It retains water. I believe Home Depot sells the Pink and Lowes sells a blue XPS foam board. Both are closed cell. They both come in various thicknesses to suit your needs. I used 1".

 

[Anchoraways]

It wasn't eps foam, it's some other stuff that's closed cell with what I can assume some sort of thin vinyl layer around it. The foam between the sand which is very stiff and not easy to puncture or tear apart by hand