Foam Replacement

[Still Afloat]

I recently shifted boat projects from the little Jon build to rigging out a new to me North River Mariner. It’s a very solid boat but, it feels heavier than it should be. So I pulled up the port side strip of decking the other day and as expected the foam is completely saturated. I wasn’t planning on tackling the flotation until next winter but, most out the seats are out right now so maybe it’s a good time.

For the past couple of years there have been several threads on flotation foam. Some thread had good ideas and some not so good. I remember one thread but that talked about a new pour in foam product that’s made specifically for boats. Anyway, it’s not supposed to saturate as bad as some of the old pour in foam products. I’ve dug through several old threads and can’t find it. Does anyone recall what this product is?

 

[Lost But Happy]

Everything I have read says that the pour in foam eventually gets water logged, hence why I went with the pink board. YMMV

 

[Still Afloat]

Yep, that’s what I’m reading. Even the Total Boat brand says it will eventually absorb water.

I’m not looking forward to a bunch of foam sheet cutting but, it looks like the best option so far. I guess my only concern with foam sheets is that the deck is supporting all of the floatation once swamped because the foam is not adhered to the hull.

 

[LDUBS]

To me a big advantage of sheet foam is ease of removal when it eventually needs to be moved or replaced. I had not thought about it being fully supported by the deck. That is a head scratcher.

Whatever product is used I think a good practice is to include as many drainage channels as possible to the drain/bilge pump area. Sheet foam sitting on top of the ribs would do that.

The following link is a discovery that @thill made about using tyvek house wrap on top of floatation foam. It sounds like it might be a worthwhile thing to consider.

https://www.tinboats.net/threads/tyvek-house-wrap-under-decking-and-over-pour-in-foam.50217/

 

[airshot]

Why not a smaller amount of the pour in foam then add the sheet foam. Thinking just enough pour in to attach the foam board to the hull ? Then again, I might be all wet !!

 

[Ray Clark]

Why not a smaller amount of the pour in foam then add the sheet foam. Thinking just enough pour in to attach the foam board to the hull ? Then again, I might be all wet !!

There are probably better and cheaper adhesives that will do that job. Polyurethane glues are waterproof and have some gap filling properties.

 

[LDUBS]

There are probably better and cheaper adhesives that will do that job. Polyurethane glues are waterproof and have some gap filling properties.

Or shoot some spots with that gap filling spray can insulation stuff to hold the sheets. That stuff sticks to everything. Might eat a hole through aluminum for all I know. IMO, having space under the rigid sheets is a good thing.

 

[Still Afloat]

Or shoot some spots with that gap filling spray can insulation stuff to hold the sheets. That stuff sticks to everything. Might eat a hole through aluminum for all I know. IMO, having space under the rigid sheets is a good thing.

Thought I read that Thill does this. I was thinking the same thing about the stuff eating the aluminum.

No ribs that I’m aware of in this boat. Maybe I’ll find some after removal of the entire deck. It has a 0.190” thick hull and transom with 0.125” thick gunnels. There are two runners on the hull plus a runner about halfway up the gunnel and then the gunnel caps. It’s a solid boat, all 5086 aluminum. The only wood product is the deck and it looks like some sort of melamine.

 

[Ray Clark]

Thought I read that Thill does this. I was thinking the same thing about the stuff eating the aluminum.

No ribs that I’m aware of in this boat. Maybe I’ll find some after removal of the entire deck. It has a 0.190” thick hull and transom with 0.125” thick gunnels. There are two runners on the hull plus a runner about halfway up the gunnel and then the gunnel caps. It’s a solid boat, all 5086 aluminum. The only wood product is the deck and it looks like some sort of melamine.

Gorilla glue website and other sources all say polyurethane glues are good for bonding to aluminum.

Great Stuff, the "foam in a can" stuff, is a form of polyurethane with other ingredients added.

 

[davidj65]

I had the same thing happen, went to set up an electrical system and discovered the foam was saturated and starting to rot the deck. Pulled it all(what a pain) and replaced it with blueboard. Left lots of drain channels and room for circulation. The challenge seems to be in getting enough material for buoyancy.

The fact of the deck(specifically the screws attaching the deck to the hull) would be supporting the wjhole boat also occurred to me. I suppose there are probably around 60 screws on my boat, all told, attaching decking, and the boat is 600 pounds with gear, that's 10 pounds per screw. It doesn't seem unreasonable if the attachments are sound. This all conjecture, though, and to me the more concerning thing is getting enough square footage of bluboard in there.

 

[Still Afloat]

That would probably be Ok then. I think I’ll just stick with the gorilla glue and try to cut to fit. A few gaps at the hull should allow water flow.

The only thing with me is one thing leads to another. Next thing you know I’ll be pulling the gas tank to clean it out. Then welding previous owner drill holes while the tank is out. That will lead to a new paint job and on and on.

I was really planning to fish this boat this summer.

 

[David Atkins]

Why not a smaller amount of the pour in foam then add the sheet foam. Thinking just enough pour in to attach the foam board to the hull ? Then again, I might be all wet !!

your pour in foam will be all wet, lol - they may say it won't absorb water but trust me after so many years in boats building most all of the poured foam will absorb water.

 

[airshot]

your pour in foam will be all wet, lol - they may say it won't absorb water but trust me after so many years in boats building most all of the poured foam will absorb water.

Would the spray in foam ( aerosol can) home insulation absorb water ? Just think of it as an adhesive for the foam board.

 

[Lost But Happy]

If you do go with the foam board, get yerself a foam knife. A regular knife sucks for foam. DAMHIK lol

 

[David Atkins]

Would the spray in foam ( aerosol can) home insulation absorb water ? Just think of it as an adhesive for the foam board.

If it is closed cell foam then it will absorb less water than open cell foam but they all absorb water, just closed cell does not absorb like open cell foam. I would go with the Closed-cell polyurethane foam.

 

[Still Afloat]

Would the spray in foam ( aerosol can) home insulation absorb water ? Just think of it as an adhesive for the foam board.

I was thinking of that but, I expect it would eventually absorb water just like the pour in stuff. Also, leaving some gaps might promote drainage. Like Davidj65 said, it could be tough getting enough sheet foam cramped in there.

 

[Still Afloat]

Time to quit contemplating, will go pull the deck right now.

 

[airshot]

I was thinking of that but, I expect it would eventually absorb water just like the pour in stuff. Also, leaving some gaps might promote drainage. Like Davidj65 said, it could be tough getting enough sheet foam cramped in there.

My thought was if the foam board was cut somewhat close to the hull, a quick squirt along the edge to hold the foam board in place....if that is even needed ?
When I look at my 1992 Sylvan, actually their is not much foam in it ! Small nooks and crannies have been filled and much of the under the floor area is foam, but no where near what I expected to be there. Lucky for me all is dry as it has been a garage Queen its whole life.

 

[Still Afloat]

Ok, got my back side and goter done. Here are some pics for my fellow couch potatoes.

Here’s the mucky mush foam. There wasn’t that much floatation, maybe a cubic foot on each side between the stringer and gunnel.



Aluminum look good for the most part.





There was no floatation foam between the stringers. Unfortunately, the stringers (~6” x 10” x 117”) are filled with foam. Maybe I can dissolve it with acetone.

 

[Still Afloat]

My thought was if the foam board was cut somewhat close to the hull, a quick squirt along the edge to hold the foam board in place....if that is even needed ?
When I look at my 1992 Sylvan, actually their is not much foam in it ! Small nooks and crannies have been filled and much of the under the floor area is foam, but no where near what I expected to be there. Lucky for me all is dry as it has been a garage Queen its whole life.

My boat certainly did not have enough foam to keep her afloat.