# Foam Core boatbuilding



## swampfox (May 9, 2007)

I have seen insulation board used. They just peel the aluminiun off.


----------



## lemaymiami (Feb 9, 2007)

the various foams used for boat building have very specific properties. Using foam in fiberglass construction isn't as simple as just adding it to the composite (that's why early composite technology was so hit and miss...). Talk to someone that builds with it before going down that road for best results.... and be prepared to spend some bucks for stuff like klegecell, divinycell, etc.


----------



## firecat1981 (Nov 27, 2007)

The foam you are looking at is not the same as the foam board you would use in boat building, they have different densities. It has little strength in both compression and tensile ranges. Basically you would flank it in glass but the core would be so soft that it would end up buckling if any stress is applied to it. 

The insulation boards (R-max.....) that swamp is talking about doesn't have any real strength either. What some guys do is use it as a form for simple bulkheads and such, then build up heavy glass around it so it really isn't acting as a core, just a form, but doing this means you don't save any weight and it's not as strong as it would be if properly cored.

I've done some tests with R-max and poly from home depot, Even flanked on both sides with glass they all failed with very little weight.


----------



## fishy82 (Nov 6, 2011)

That foam is 1lb eps. It's pretty much useless, except in surf board building. It must be vac bagged or resin infused with a veneer covering or multiple glass layers to have any sort of strength. Plus 1lb should be vented to prevent delamination caused by exotherm. Royal foam in jax sells 2lb or you can custom order higher density eps if needed. Theres also a couple manufacturers in Orlando and s fl that make this.


----------



## swampfox (May 9, 2007)

What are you trying to do with it? I used to lay up a lot of carbon and glass for race cars and shifter karts. We would use strips of card board in some applications. Are you making a deck,console or what?


----------



## Virnut (Nov 8, 2012)

rebuilding a boat, Just wondering about that material.
In the case of divinycell etc what are proper weights? 
3 4 5 pounds?


----------



## el_scorcho (Oct 23, 2008)

You can, I've done it in small applications. It is allot like surfboard foam and has similar characteristics when laminated. It really depends on what you are trying to do with it.  But you can use it for some pieces for sure.  Having done it I would not use it for a deck again. Its not dense enough.  Make a few test panels and hit them with a hammer  and drop weight on them and see how they fail and you will get a good picture of what you can and cannot do with it. 

I would recommend looking at plascore.(1" 4x8 was $80 also 1/2, 3/4 and 2")  It's relatively inexpensive, easy to work with, and light. It also has very impressive strength characteristics.  I am using it now for a little glades skiff and against the advise of everybody I talked to even made the transom out of it.  Which I will say came out extremely strong and extremely light. At least half the weight of the same size transom using the 25lb foam ($300 for 4x8) everybody said I "had to use".  

My rear bulk head weighs 2lb 14oz.  Front bulkhead 3lb 10oz.  Transom 1.5" thick using x2 3/4" inch placore panels laminated together and skinned weighs less that 10 pounds which I over laminated because of all of the "you cannot make the transom out of this" comments I got. I would not use it in the transom if I was going  to mount a motor with through bolts. I think It could be done, but it would be more complicated.  

FYI  you can get similar results to bagging if you get a flat surface (I use glass, I have a 4x8 piece of 5/8") lay it up on the glass put down the core material then place another flat surface on top of the core material and add weight, let it cure and repeat the process on the other side. When you pop the panel off of the glass is as smooth as you guessed it glass, and looks like it was popped from a mold.  I like glass because I can see what is happening from underneath and make adjustments to the weight to get the best lam.  But you need thick glass. 

One more note. Some people will say Nidacore is the same material. Its not. Finished Plascore panels are stronger in several ways. 

I would also add that there is no good argument for marine ply given the materials that are available today.


----------



## el_scorcho (Oct 23, 2008)

Not how I do it but interesting. 

http://spearflatsskiffs.com/?p=236#more-236


----------



## el_scorcho (Oct 23, 2008)

Forgot to say that I used a polyurethane foam. Polystyrene requires epoxy resin. I would use the same resin that the hull is made of which is probably polyester.


----------

