Wet foam core, rotten stringers

[joenapier]

I got hold of a project boat I am excited to restore - a 1980 Centruy Arabian with a 350 V8. I got more than I bargained for when I found rotten stringers in the bilge area. I started digging and removing wood and I am still digging. I'm not scared to replace all the stingers and floor from the bow to the stern if that is what is required - pretty good with wood and I've laid up some glass before.

My question has to do with the high density foam that is beneath some area of the plywood flooring. Some of it is wet and certainly I have to chip it all out. How do I replace this foam? Do I need to? Do most boats not have foam under the floor? (old wooden classic boats do not)

Thanks.

Joe

 

[gcboat]

Re: Wet foam core, rotten stringers

There have been pro's and con's over the years about adding new foam. Some guys throw old soda bottles in the bilge ( sealed plastic ).
The newer closed cell foam is pretty watertight so if you decide to go that route you should have no further worries about it getting waterlogged again. It comes in a spray form or a mix. I think they are epoxy based - don't remember.
Anyway - there's a bunch of guys who have done this and I'm sure they hopefully come along and bail me out.
BTW - welcome to the zoo !!

 

[joenapier]

Re: Wet foam core, rotten stringers

Thanks - I wonder if the coke bottle idea would work encapsulated in the foam. Sure would save some money on foam volume.
Does the foam add strength or just displace water in case your boat is swamped? Probably the answer is "both".

 

[oops!]

Re: Wet foam core, rotten stringers

ok......hang on......in some boats foam is a structural component of the hull and it needs to be replaced ......ill post back in with why in 3 minits....

hang on

 

[gcboat]

Re: Wet foam core, rotten stringers

In some cases you're right - both. Wouldn't be necessarily so on a fiberglass boat.
Pretty much 'no' on the bottles mixed with the foam. The foam expands with such a terrific force it would literally crush that plastic to nothing. Then you would have voids - sorta' defeat the whole purpose.
I guess there would be a way to do it but that would be up to someone who's tried it to answer.
Here's a quick link to just one company that sells buoyancy foam: http://www.buoyancyfoam.com/
Good luck with your project - keep us posted and take lots of pics.

 

[oops!]

Re: Wet foam core, rotten stringers

ok.....first of all


uscg rules state that all boats under 20 feet need flotation foam....its the law.

the floatation foam is there so if the boat gets swamped, the people in the boat have somthing to hang on to instead of floating away with the current.

the problem is....as you can see the foam gets wet and it rots the boat.

now.....having said that.....some of the manufacturers decided in order to cut costs......they could use the foam to stiffen the hull....add more rigidity....and there for use less fibergalss and resin....less weight, less cost....same stregnth...boat is toast after 20 years...them coustomers come buy a new one....perfect......

they didnt figure on us back yard boyz rippen em apart and saying WTF ???

thats the back ground....

you can replace the foam using ping pong balls and pool noodles if you want...but if the foam is structural....it must be replaced....unless you do an entire hull wrap of fiberglass.....to stiffen the hull

the way to tell isf the foam is structural is if it is poured in and has direct contact with the hull down the entire legnth of the boat on both sides.....kinda like a filler........if there is just big chunks of foam thrown in there...it is not structural and then you can use your soda bottles.

hope that helps....

cheers
oops

 

[salty87]

Re: Wet foam core, rotten stringers

oops, i think your definition of structural foam is a little cautious...or i'm missing something. i think foam is just poured, out of ease in most hulls so it's contacting everywhere.

unless it really is structural....the only problem with foam is that when it is poured into the cavities in the hull, it seals them in a manner that prevents water from draining. water gets trapped in the foam which surrounds the wood. if you don't pour it into the hull you can prevent it from sealing everything.

has foam been a structural component of a boat over 16' built since the 70's? i dunno, is there a reg. about the structural use of foam? i think it only covers manufacturers and when used for flotation.

 

[Bondo]

Re: Wet foam core, rotten stringers

uscg rules state that all boats under 20 feet need flotation foam....its the law.

Ayuh,...

But only if you're an OEM boat Manufacturer......

An old boat is Your boat....
You can do Any danm thing you please....

 

[oops!]

Re: Wet foam core, rotten stringers

oops, i think your definition of structural foam is a little cautious...or i'm missing something. i think foam is just poured, out of ease in most hulls so it's contacting everywhere.

unless it really is structural....the only problem with foam is that when it is poured into the cavities in the hull, it seals them in a manner that prevents water from draining. water gets trapped in the foam which surrounds the wood. if you don't pour it into the hull you can prevent it from sealing everything.

has foam been a structural component of a boat over 16' built since the 70's? i dunno, is there a reg. about the structural use of foam? i think it only covers manufacturers and when used for flotation.

the foam can add as much as 10 % rigidity to the hull....some boats...are actually really thin as far as glass.... i know in my b-liner you can feel the ripples of the water agains your leg when the boat is floating.

there is a very well known and loved boat, that is so thin on glass...it absolutly NEEDS foam as its main component....

Ayuh,...

But only if you're an OEM boat Manufacturer......

An old boat is Your boat....
You can do Any danm thing you please....

fully agree....and the more i think about your statment about "the foam just being there to rot the boat" still rings loud in my head.....and its true

thats why the only expanding foam in my boat....is just an insulator for the cooler !

the marine surveyor that inspected my hull prior to the extension said if you are going to register the hull as "new"...it needed flotation if it was under 20 feet....(all kinds of insurance stuff if the boat goes down)......(canadian regs are very close to the us regs.

but if you are just doing a resto....its your call.....thats also why i wraped my entire hull with 1708 stiffining it. (following another one of your statments)..."know its strong enough"........
because of that statement......i KNOW my hull is strong enough.....

to the op..........as stated....its your choice.....just make sure you know your hull is strong enough.

cheers
oops

 

[Bondo]

Re: Wet foam core, rotten stringers

Ayuh,...

Sure is Great to know that atleast Somebody listens to Me,.....

 

[joenapier]

Re: Wet foam core, rotten stringers

OK - I'm relieved that the actual stringers are in good shape under the glass layup. The first picture shows 1/2 of the way through the foam on the port side. The second shows where the majority of the rot is - under the motor mounts. The thrid is a drawing of the boat as-found condition and the plans to fix.

At the time of this posting, I have removed all the foam on both sides. I supported the motor with blocks (I'd like to avoid pulling the entire motor and drive) and dug all the wood from under the ledge where the motor mount is. The motor is resting on blocks and there is only a skin of chopped glass under the motor mounts.

Now for some discussion...

I plan to pour seacast in the section under the motor mounts. Seems like this will fill the glass shell (and support the motor) better than a beam of wood wedged in there. Any issues with bolting into seacast?

What the heck is below the flat floor portion of the bilge below the motor? Maybe I need to dig it up also? I guess I just answered my own question...

The transom is not in bad shape. There is exposed plywood on the inside of the transom and a splattering of chopped glass around the edges of it. If I wanted to firm it up, would you recommend a penetrating epoxy for the wood? What brand?

When this is all done, I bet that I will reduce the weight of the boat by 200lbs in wet foam alone! I know the seacast weighs 50 lbs / ft3, but that is only about 30% more than wood.

Thanks for the input.

 

[oops!]

Re: Wet foam core, rotten stringers

i dont really see how you can repair the motor mounts with out remopving the motor.....i like to have room to "get in there".

but, if you can figgure out a plan to fix it without disturbing the alignment of the motor............

looks like you have lots of help there


cheers
oops

 

[jonesg]

Re: Wet foam core, rotten stringers

Bolting INTO seacast ?, it threads well but I dunno if it will hold a thread without backing and a nut to hold the bolt. Give them a call, they'd know for sure.