Another d@*# foam question!!

[58hydraglide]

All right guys,

I've read as much info here that I can find and done other research until I'm blue in the face and I'm not entirely satisfied with my decision on my foam yet for my project (73 Slickcraft, new transom, stringers etc. The original foam was poured and held water, caused rot, blah, blah. My inital thought was to line the cavities with poly sheeting and lay in some channel molds in the bottom of the hull to drain water. pour the foam, remove the channels ans poly and reinstall the foam. I've been following North beach's starcraft rebuild and Am considering the block foam now (expanded polystyrene, I think). I really like it's ability to pass water on through to the bilge.

The thing that concerns me is, I am sure that the original poured foam provides rigidity to the hull. Can I accomplish this with the other foam, even with careful carving and fine tuning the fit? what is its compressive strength? Will it break down into little beads and plug my bilge up?

If part of the foam's job in my application is to provide strength and this type won't do it, then I need to eliminate the hull's need for the foam as strength. I have some pics below of my hull with an option on how I can compensate for the lack of the structural foam.

The first pic is of the transom with the main stringer on the left and the outboard edge of the hull on the right. The main sringer is buried in a chine and I have another chine halfway between the main stringer and the outboard edge. The total distance from the main stringer to the hull edge is 20" ,the chine falls halfway between the 2. If I installed a stringer in the outboard chine that would leave me about 10" between each to fill with foam. This added stringer would be 5" tall at the transom.

In your opinions, would this be necessary or would the molded chine provide enough strength to the hull without the addition of "poured foam"

I really need to hear some input on this. I need a whole LOT of foam and the polystyrene would be much less expensive than poured foam, if it is suitable in this application.

 

[Mark42]

Re: Another d@*# foam question!!

If you don't want to worry about rot due to foam under the deck, consider putting it above the deck. Foam seat bases, under gunnels, build/box in the area under the splashwell and foam that. Leave the stringer spaces empty.

This is what the CG recomends because leaving the under deck area empty and foam higher up prevents the boat from rolling over when swamped. Water can fill the under deck area, keeping it down, and the foam above deck keeps the boat upright.

 

[slasmith1]

Re: Another d@*# foam question!!

You are blaming the foam for rot in a 36 year old boat? I say it did well to hold up and still be re-buildable pour it in and go for another 36 years.

 

[58hydraglide]

Re: Another d@*# foam question!!

You are blaming the foam for rot in a 36 year old boat? I say it did well to hold up and still be re-buildable pour it in and go for another 36 years.

Yeah Yeah, your right slasmith1 , but,

Mark42 you have a very valid point about installing the foam higher up, but again, that leads me to the question of whether or not Slickcraft intended the foam I'm replacing to provide structural support to the hull or not.

One other point slasmith1. I think the previous owners made a conscious effort to keep the boat as dry as possible. Wherever there was rot there was saturated foam directly next to it. when I removed it I set the saturated pieces aside and set them up on a piece of plywood vertically to drain and they wouldn't give up an ounce of water. They sat there for over a week. My point being that once that pourable foam was wet, it's not going to drain. Particularly in the environment it's in.

 

[83mulligan]

Re: Another d@*# foam question!!

what about lining the cavity to be filled with tyvek or something similar?

 

[jonesg]

Re: Another d@*# foam question!!

Extruded foam is a lot stronger than expanded bead. Pink being lighter than the blue versions at home depot. It won't stand up to gasoline.
But then, neither does expanded bead.

If you are certain the foam was integral and don't want it bonded to the hull then you just have to install some formers instead first.
Then install the loose foam, I'd bond it to the new formers.
Pink insulation foam could be spaced 1/4" off the hull, its ez to cut with an elec bread knife or a hot wire bow hooked to a car battery will cut it like a hot knife in butter. Limber holes with plastic pipe to ensure drainage through all compartments to bilge. Splashing a bit of resin or fancy looking gelcoat in the limber holes isn't good enough.

I think my approach, being cheap and lazy, would be go back with pourable foam but stick some soda bottles in there to reduce the amount of foam required. Maybe lay down a bed of foam, stick the bottles in , then cover with foam. If the foam gets wet, the bottles will reduce the amount of water the compartment can absorb.

 

[alumi numb]

Re: Another d@*# foam question!!

get some pool noodles and cut them in half.
then lay them upside down in a strategic way as to create bridged channels for the moisture to flow.
then go ahead and pour your foam.
then again you could cut pvc pipe and use that for the bridged channels.
something to think about anyway.
my boat is aluminum and i'm using pool noodles in the cavity behind the side panels.
the noodles are hollow so i'm running the wiring thru them.
never have to worry about grounding out or chafing the wiring.
there will be about 6 layers of noodles on each side so that's 12 channels for wiring.
won't work out quit that way but they will be there if i need.
couldn't sleep so here i am.

 

[North Beach]

Re: Another d@*# foam question!!

58, I can't answer the question about whether the poured in place was intended to be structural. I can say that the PIP and the expanded (bead) insulation is open cell and will absorb water when heat is introduced. Once that happens it doesn't like to let the water go The extruded (pink and blue) is closed cell and that is the way I'll go with the 66. This approach also negates the beads and bilge problem. I also thought about the structural aspects of the PIP and thought it would also quiet things down a bit, but just looking at the way my boat is put together, I don't think more structure is what I need.

BTW, I carry a small thin keyhole saw on my tool belt like they sell at Home Depot for cutting drywall and it cuts the stuff just fine.

Good luck with your project!

 

[Bondo]

Re: Another d@*# foam question!!

for my project (73 Slickcraft, In your opinions, would this be necessary or would the molded chine provide enough strength to the hull without the addition of "poured foam"

Ayuh,... I've both Restored,+ Junked Out several Slickcrafts,....

Those hulls are Very Well Built..... A Slickcraft does Not rely on Foam for Strength....
Matter of fact,... I hope to find another nice Slickcraft for restoring sometime in the future,...
They're just Fantastic Hulls.....

So,.... If you're trying to justify the Foam as a Strength thing,... Move on...The hull Don't need it....

 

[johnbell47]

Re: Another d@*# foam question!!

58, I can't answer the question about whether the poured in place was intended to be structural. I can say that the PIP and the expanded (bead) insulation is open cell and will absorb water when heat is introduced. Once that happens it doesn't like to let the water go The extruded (pink and blue) is closed cell and that is the way I'll go with the 66. This approach also negates the beads and bilge problem. I also thought about the structural aspects of the PIP and thought it would also quiet things down a bit, but just looking at the way my boat is put together, I don't think more structure is what I need.

BTW, I carry a small thin keyhole saw on my tool belt like they sell at Home Depot for cutting drywall and it cuts the stuff just fine.

Good luck with your project!

I just have to throw this in...What do they make floating docks out of? Well, they use stryofoam, bead foam, polystyrene. It does'nt absorb water. each bead is a bead, not open cell. there are open cells between the beads though. they are making folks encapsulate the billetts now cause it will break off or the ducks pick at it and it ends up all over the lake. It does melt in gasoline, just don't let the gas get to it, you really should'nt have gas in the bottom of your ship. I used 1 inch, 4 x 8 sheets ripped into suitable sizes, then trimmed with a bread knife. I left it one inch off the hull and drilled limber holes, lined them with pvc, glassed in place. I made the limber holes 1 1/2. I was worried the beads would break off and stop up the holes. I cut this stuff on my table saw, what a mess! Little electrostaticly charged bits floating everywhere, sticking to everything. Stuff is cheap too!

 

[58hydraglide]

Re: Another d@*# foam question!!

Ayuh,... I've both Restored,+ Junked Out several Slickcrafts,....

Those hulls are Very Well Built..... A Slickcraft does Not rely on Foam for Strength....
Matter of fact,... I hope to find another nice Slickcraft for restoring sometime in the future,...
They're just Fantastic Hulls.....

So,.... If you're trying to justify the Foam as a Strength thing,... Move on...The hull Don't need it....

Bond-o,

you hit the nail on the head. That's the question I needed an answer to. I agree that Slickcraft is an exceptional boat.

Thanks, gentleman for your input. I will take all of it into consideration. There are some excellent threads on foam here. For the sake of redundancy, I don't want this to turn into another one of which is best etc.

 

[Mark42]

Re: Another d@*# foam question!!

I just have to throw this in...What do they make floating docks out of? Well, they use stryofoam, bead foam, polystyrene.....

I have found that many floating dock suppliers have switched over to polyurethane foam. The polystyrene and polyerster foams of yesterday are not as tough as todays polyurethane foam, and polyurethane does not break down when exposed to water over a long period of time like the old polyester foams that absorbed water in so many boats.

I think you will find that nearly all the PIP foams are now polyurethane.

 

[Mark42]

Re: Another d@*# foam question!!

BTW, I found the best adhesive for gluing the foam panels is Gorilla Glue. The regular maple syrup colored product (they now have several). It glues foam really well, and sets fast. Its also expands when a little water is added. So if you want to glue up 3 or 4 1.5" panels to make a block to cut/carve, pour about 2-3 oz of glue into a plastic cup. Add about 5-10 drops of water and mix until it starts to turn honey color. That means its ready to "kick" and expand. Just pour a few thin lines down the panels, and press together. Add some weight to prevent them from lifting apart as the glue expands. In about 10 minutes the glue is cured enough to start working with the panels.

 

[North Beach]

Re: Another d@*# foam question!!

58, Just thought I'd throw in what little I know. Personally, I've been involved in millions of dollars of water soaked EPS insulation removal projects so I won't be using it in my boat. I'm sure if you keep your boat covered, you won't have any problems with whatever you use.

 

[Lou C]

Re: Another d@*# foam question!!

I can't speak for what other manufacturers would say, but when I asked Four Winns abou the foam they said it was for both structural and floation reasons....and other boats I have seen re-done, that did not have foam orginally, had a beefier structure (more transverse bulkheads) than boats that had foam. So I replaced the foam and sealed the new deck way better than FW did and got rid of the carpet. People make a big deal about foam holding water, etc, but usually the beginning of rot in any boat with plywood decks, is CARPET and UNSEALED HOLES. Carpet holds moisture and unsealed holes let it get into the wood, the foam is several inches below all this...and is just where that same moisture eventually winds up....Stop it at the source....and you don't have to worry...

 

[1cobia]

Re: Another d@*# foam question!!

Hi any of you guys know if a 1991 cobia cuddy has foam for structure
its a 19' with 4 stringers they did lousy glass work but i'm redoing all that

 

[58hydraglide]

Re: Another d@*# foam question!!

Mark42,
I haven't used gorilla glue yet , that's a good tidbit of ifo there. Do you use it anywhere else in a marine application? I've decided to replace some of my underdeck foam with foam above the waterline in several areas that were previously empty. Thanks for the advice.

Northbeach,
That's interesting also, but I have come to a conclusion that Any foam, given enough time, will become saturated. But once it does, will it allow the water to drain away or not. I would think that would be the deciding factor. (hmm, maybe a little test is in order.) I think it was Bond-o that stated in a previous discuss about foam and rot etc. that it's a boat..... in a wet environment.... What more do you need to know?

1cobia, maybe some pics of your boat will get a few answers. I've seen hulls that have relatively large flat areas in the hull without any chines or ribbing so to speak that probably relies on foam for strength but If you can post pics You'll get better answers from guys with a wealth of knowledge on here.

 

[Mark42]

Re: Another d@*# foam question!!

Mark42,
I haven't used gorilla glue yet , that's a good tidbit of ifo there. Do you use it anywhere else in a marine application? I've decided to replace some of my underdeck foam with foam above the waterline in several areas that were previously empty. Thanks for the advice.

I only used it on my hard top project so far. Had to glue up the foam panels and Gorilla Glue was the only adhesive I found that worked. The foam top is covered in epoxy and glass, so the glue is pretty well isolated from weather and water.

 

[Lone Duck]

Re: Another d@*# foam question!!

If you don't want to worry about rot due to foam under the deck, consider putting it above the deck. Foam seat bases, under gunnels, build/box in the area under the splashwell and foam that. Leave the stringer spaces empty.

This is what the CG recomends because leaving the under deck area empty and foam higher up prevents the boat from rolling over when swamped. Water can fill the under deck area, keeping it down, and the foam above deck keeps the boat upright.

YUP!