Going Back with foam???? WHY?????????

[tank1949]

I am, reluctantly, rebuilding and replacing ROT under, around and behind a 1994 Pro Line 2950 cuddy cabin's fuel tanks and fish box area. A rotted nightmare to say the least... Under each of the approx. 120 gal tanks, the builders had poured in foam for strength, which over a period of years had become saturated with water and rotted the plywood cap and fish box bulk heads. It isn't rocket science to remove and replace the ROT, BUT why would I go back with same crappy foam that will eventually allow water in, become saturated and rot the new wood???

I know it does provide strength, but I am not in a hurry , like the builders who wanted them to quickly sell. I want it to last. I want this repair to be done ONCE.

Under each tank, the builder had only glassed in 2 triangles in a 9.5'run, excluding stern and forward mid-cabin bulkhead. They had glassed in the top of the cap and poured in foam. The bottom of the cap was not cover in fiberglass/cloth, as best that I can tell.

The tanks were all sealed on bottom and back side with foam. I am not going back with same tanks in the same locations.

I plan on glassing in 1/2 dozen more triangles and replacing cap with pressure treated plywood, covered by 6 oz cloth and epoxy on both sides. The triangles with be glassed in using epoxy and 6 oz cloth too. I will cut a drain hole in each triangle's bottom where it will be glasses against the stringers. Therefore, any water that comes in can drain towards the end of the boat and escape via a drain plug hole (also cut). The small potential gap between cap's underneath and top part of each triangle will be epoxied with fumed silica.

Pressure treated plywood isn't as pretty as marine ply, and not expensive a synthetic miracle material. My epoxy will stick to the pressure treated plywood.

If anyone sees a problem, please advise.

 

[ondarvr]

Don't use cloth is about the only comment, it's not as strong as other types of glass, but it will work. If the new fuel tanks are metal, don't let them come in contact with the PT wood.

 

[tpenfield]

Putting foam back in will add the needed strength to the boat and deaden sound. If you use PT wood, you have to let it dry out first. Boat builders use a PT wood that is kiln dried after treatment (KDAT), so the can use it right away.

The foam should be closed cell and will add flotation as well as strength. The old foam does not readily absorb water when new, only after being subjected to water and weather. Don't blame the foam for something that is not its fault.

 

[gm280]

I think I would forego the pressure treated plywood and get some other quality exterior grade or even marine ply. And as stated, the new mix and pour foam doesn't absorb water like the old foam did. It provides strength and flotation and if I were doing the work, I would use the foam myself. but that is just me and my opinion for what it's worth.

 

[ondarvr]

The new foams are no different than the old ones, and they are, and always have been, closed cell.

 

[airshot]

With all of todays high technology you would think that they could make a foam that did not absorb water??? What about adding things like noodles that do not absorb water then just filling in the tiny left over cracks with the expanding foam? I know a lot of guys that restore the tinnies use the swimming noodles for their flotation. Just a thought here.........

 

[ondarvr]

It always comes down to cost, if customers would pay for better materials they would be used.

 

[jbcurt00]

With all of todays high technology you would think that they could make a foam that did not absorb water??? What about adding things like noodles that do not absorb water then just filling in the tiny left over cracks with the expanding foam? I know a lot of guys that restore the tinnies use the swimming noodles for their flotation. Just a thought here.........

I'd never skip flotation foam, and I would skip it before using pool noodles. Tie a 10lb dead weight to one and drop it in the water. Not only do noodles not float nearly what some think they will, they also absorb water... Even noodles left floating in a pool will, if left long enough. More sponge like then foam.

 

[tank1949]

I'd never skip flotation foam, and I would skip it before using pool noodles. Tie a 10lb dead weight to one and drop it in the water. Not only do noodles not float nearly what some think they will, they also absorb water... Even noodles left floating in a pool will, if left long enough. More sponge like then foam.

I am not near as worried about sound than I am for strength. It just seems to me glassing in extra triangles, although labor intensive, would do a good and not trap water. I have several pieces of PT DRIED plywood and gallons of epoxy. I don't know if boat builder still use the foam. Yet, it is my understanding that they have all replaced wood with synthetics. No rot regardless.

 

[roscoe]

Yet, it is my understanding that they have all replaced wood with synthetics. No rot regardless.

That is simply not true.

Lots of wood in lots of boats being built today.

Plywood is strong, light, cheap, and flexible. Nothing else compares.

 

[jbcurt00]

Roscoe is absolutely correct, and yes, boat builders are still using foam.

The foam isnt the problem, neglectful owners are what causes boats to get waterlogged and develop wood rot.

 

[Teamster]

Use the foam,........

Drowning sucks,...

Or, At least I guess that it does, No one has ever lived to tell after dying when their boat sank,....

 

[Old Ironmaker]

Putting foam back in will add the needed strength to the boat and deaden sound. If you use PT wood, you have to let it dry out first. Boat builders use a PT wood that is kiln dried after treatment (KDAT), so the can use it right away.

The foam should be closed cell and will add flotation as well as strength. The old foam does not readily absorb water when new, only after being subjected to water and weather. Don't blame the foam for something that is not its fault.

Just this past Friday we cut and laid in a new PT plywood not marine grade in a rebuild on a 19' StarCraft. What should the max. moisture be before laying the new carpet? Should I start a new thread? I will now that I think about it.

As far as the closed cell foam that's what we sprayed in where it was removed. Not much of a choice as that's what's is used until they come up with something else. I have heard of blowing it into sealed bags to ensure it doesn't take on water as I have read here on iboats.com but we didn't. We cut and pasted everywhere else with ridged panels of closed cell. The foam in the gunnels were white open cell not closed cell. Open cell is like a Styrofoam coffee cup. You can tell by seeing the larger balls in the white open cell foam. Less structurally sound but better buoyancy per sq. inch. Styrofoam is a brand name. Just like we call all plastic containers here Tupperware. not the same quality.

 

[Scott Danforth]

Just this past Friday we cut and laid in a new PT plywood not marine grade in a rebuild on a 19' StarCraft. What should the max. moisture be before laying the new carpet? Should I start a new thread? I will now that I think about it.

As far as the closed cell foam that's what we sprayed in where it was removed. Not much of a choice as that's what's is used until they come up with something else. I have heard of blowing it into sealed bags to ensure it doesn't take on water as I have read here on iboats.com but we didn't. We cut and pasted everywhere else with ridged panels of closed cell. The foam in the gunnels were white open cell not closed cell. Open cell is like a Styrofoam coffee cup. You can tell by seeing the larger balls in the white open cell foam. Less structurally sound but better buoyancy per sq. inch. Styrofoam is a brand name. Just like we call all plastic containers here Tupperware. not the same quality.

do not use PT wood on an aluminum boat. the chemicals in the PT will eat the aluminum.

 

[tank1949]

Roscoe is absolutely correct, and yes, boat builders are still using foam.

The foam isnt the problem, neglectful owners are what causes boats to get waterlogged and develop wood rot.

I don't see how neglect cause this rot of Biblical proportions. More like poor design... Besides, I am not original owner.

 

[jbcurt00]

I didnt blame you for the neglect.

There are 1950s and 60s boats w original decks, stringers and transoms floating and in use all over the US. Theres at least 1 owned by a currently active member.

Those boats were somehow made differently then every other one coming off the production lines 50yrs ago? No, their owners were diligent about use and maintenance and took protective measures when the boat was stored.