Rebuilding/restoring an older hull

[JimClark]

So I am starting a project to restore a 29in LSH/Spec Hydro to race some this year. It has the pink foam shaped in the sponsons. I am going to take all the pink foam out reseal the inside with epoxy reinforce the turnfin attachment point and then use poar foam and then reskin the bottom of the sponson. I have some 2 part poar foam that appears to still be good (havent tested it yet) but was wondering if anyone has tried using older Poar foam.

[Darin Jordan]

Jim... WHY are you taking out the pink foam??

I would NOT recommend pour foam! From my experience, it has a couple of issue, especially inside of a wood boat.

When it gets warm out, it expands. I've had it change so much in some of my fiberglass boats that it sucked the deck down and the sides in on one of my IM31 monos when I traveled to LA.

Also, if you break the skin on it, it'll absorb water like crazy.

Honestly, I think you should get the skins working on that boat, and then seal the outside, and go race it. Mark Beatty uses a light layer of glass on the outside of his boats and they seem to turn out really nice.

I'm just worried that you'll be into this so far you could have just built from scratch! :doh:

[NativePaul]

I have used pour foam in wood boats without issues in my climate before, but the only advantage it has is that it automatically shapes itself to fit the cavities you have, so is easier to use. If someone has already done the work of shaping hard foam for you it is a much better solution. Pink foam is made by Owens Corning and while they do many different densities the most popular is Foamular 250 which weighs 1.55 lb/cubic foot, has 25 PSI compressive strength and 0.05% maximum water take up by volume. Most popular pour foams are 2 lb/cubic foot with 40 PSI compressive strength, which sounds good, but when I have cut open pour foam I have found voids inside and varying bubble sizes so I doubt I was achieving near 40 PSI in the real world, and Foamular 400 is at least as strong at 40 PSI and only weighs 1.8 lb/cubic foot.

[JimClark]

It just doesn't look like there was much sealing done with epoxy on this boat

Sent from my SGH-M919 using Tapatalk

[Fluid]

I've had popular two-part pour foam shrink in the sun, sucking in my deck on a very strong glass hydro after a long Texas summer (95*F+ every day). OTOH I used pour foam in the sponson tips on my wrecked SAW hydro two years ago and when I split the hull open in a crash the foam was in place, still solid and of course did not absorb water. That boat only had the foam in for a few months though, and it never saw the hot weather we have in Texas.

I can understand the desire to remove the foam if the wood was not waterproofed. A lot of work, but probably worth it if hull longevity is desired.


.

[JimClark]

I understand your point Darin but this boat was built with a lot of CA and there are some slightly loose areas but I could also reinforce those areas with Glas on the outside

Sent from my SGH-M919 using Tapatalk

[JimClark]

Anyone have any recommendations for a turn fin for this 29 inch spec hydro? I want one that I can polish up. Also need help /advice for installing it such as what angle and where on the sponson to mount it.

[785boats]

Hi Jim
A bit late but I've had a computer crash & only recently had it fixed.

But on advice from others I have put the Zippkits .12 rigger fin on a couple of small sports hydros of around 30" long. I like them.
Only twelve bucks, but you have to make, or buy, your own bracket.

http://zippkits.com/~zippkits/index.php?main_page=product_info&cPath=68&products_id=227

Cheers.
Paul.

[JimClark]

Thanks Paul I gave up and bought a UL-1 fin just got it today. Any comment on the 2 part foam?

[785boats]

I use GP3300 foam & don't have any problems with it. But the mixing ratios must be strictly adhered to or it can shrink after curing. If the spec sheet gives mixing ratios by weight, be sure to follow it to the gram. Just because part A & part B are in the same size tin does not necessarily mean it is a 50/50 mix by volume. Unless the spec sheet says so.
Also it is important to warm the two parts up first if the weather is cold or it will not expand as much as it should so it will be more dense, & therefore heavy.

Cheers.

[JimClark]

All I am finding for GP3300 in searches is old refernces to GP3300 NIMH batteries. Nothing in reference to two part foam

[785boats]

Sorry Jim.
Another typo on my part. Should be GP330.

http://www.ccpcomposites.com.au/foam-urethane