Glassing the underside of the floor?

[F14CRAZY]

http://forums.iboats.com/showthread.php?t=272749

My primary rebuild thread is above.

When I get my stringers all done, what can I do to the plywood to better protect it? I want to call it the deck but it's technically the "sole", right? I do intend on putting a layer or two of fabric on top w/ epoxy but can you do anything to the bottom side to better preserve it? Like use penetrating epoxy? Or put a layer or two of glass on it before screwing it down? Should I use penetrating epoxy on the topside too before adding a couple layers of fabric?

I understand the idea of predrilling holes larger, filling with epoxy, predrilling again, and then screwing the deck down, but would you put some peanut butter between the top of the stringers and the bottom of the decking?

 

[lucid484]

Re: Glassing the underside of the floor?

yeah i was wondering the same thing for when I redo my deck....only problem i see is say your stringers are glassed perfectly and same with you deck...once you drill a screw from deck to stringer you basically open up a whole between them...and if you get rot in the deck thats where it spreads to the stringers......so i guess the mystery is how to 100% seal the screw in so there in no chance at all for water penetration.

 

[maxum247]

Re: Glassing the underside of the floor?

Coat the underside of the plywood with two coats of epoxy resin, be sure to get all the edges of the plywood with two coats of epoxy also.

 

[oops!]

Re: Glassing the underside of the floor?

the specs show that 4 layers of epoxy is that best.......in fact it doubles between one and two layers....triples at three.....and at 4 layers....its 10 x the protection.......

if you were using polyester you would need to add csm as well....not so with epoxy.........


it is very inportant for the longeviety of the deck and stringers to plug all the thru holes.......

if you search here and see rotted stringers....you will find that most stringers are rotted from the top down......and only in certain areas........this is where the screws are drilled into the stringers.....

the big thing is to make sure the drill holes are well coated........

 

[ondarvr]

Re: Glassing the underside of the floor?

For long life it's best to use at least one layer of glass on the bottom side of the plywood, a light cloth works well. Plywood tends to check (crack) after a period time and depending on the type of wood it's made from, some types may do it sooner than others. The glass adds strength to resist the checking and provides a thicker layer for better water resistance.

 

[Aussiefishn]

Re: Glassing the underside of the floor?

I'm thinking about this too.
What if you were to cap the stringers with a strip of glass and carefully place down and screw the floor down while the resin is wet. Either that or the(peanut butter) as mentioned.
Wouldn't that make a seal around where the floor/stringers fasten together?

My floor was very rotted but the stringers weren't. by the look of them the glass over stringers was wet when the floor was nailed down. I don't think the under floor was sealed at all.

The new floor will be sealed fu sure.

 

[oops!]

Re: Glassing the underside of the floor?

that only workes to a certain degree.....the bond you get is only a fraction of the surface.....so it is weak.

one way is to over drill the holes.....fill with epoxy then screw into the epoxy.

another way is simple....if you are using poly......screw the peice down. back the screw out totally....fill hole with 5200.....coat screw with 5200....and reinsert...................this way is not perfect....but better than nothing.

any way you do it.....its the tedious part of a deck job

 

[F14CRAZY]

Re: Glassing the underside of the floor?

How many layers, and what weight fabric should i use for the deck? I will be using epoxy. One of two CSM?

 

[Chris1956]

Re: Glassing the underside of the floor?

Boy,I think using epoxy on a plywood deck is an expensive overkill. it will obviously work great, but Poly resin will work acceptly. I would lay strips of poly saturated cloth on the stringers, a piece of cloth on the underside of the plywood, all sides (but not the top) sealed with poly resin, and then screw thru the plywood into the stringers to hold the plywood in place. Countersink the screws and use stainless steel screws. Now two layers of medium cloth over the plywood and screw heads, and saturate it with poly resin. That floor will last as long as the rest of the boat, provided you do not allow water to get into the plywood from above by driving screws into it without sealing them.

 

[F14CRAZY]

Re: Glassing the underside of the floor?

Thanks for all the input guys. Complicated stuff but nobody said it would be easy

 

[Robj]

Re: Glassing the underside of the floor?

When I secured my deck to the stringers, I coated the stringers with lots of 5200, predrilled the holes and secured the deck. Afterwards, a coat of resin onto the ply and then a layer of matt. Seals all the holes.

Have a great day,

Rob.

 

[jonesg]

Re: Glassing the underside of the floor?

When I secured my deck to the stringers, I coated the stringers with lots of 5200, predrilled the holes and secured the deck. Afterwards, a coat of resin onto the ply and then a layer of matt. Seals all the holes.

Have a great day,

Rob.

ditto that and what chris1956 stated, I'd go poly with light cloth for the underside of the deck , seal edges real good !,
maybe slooow epoxy putty on top of the stringers to bed the deck, then bed screws with 5200 and glass the whole top to seal.

 

[F14CRAZY]

Re: Glassing the underside of the floor?

Thanks, sounds logical to me.

Where the left and right edge of the floor come to the hull I know you would "tab" it to the hull with glass on the top but would you put down epoxy too? I know Bayliner didn't

 

[proshadetree]

Re: Glassing the underside of the floor?

I packed the sides of mine with csm till level befor I laid down the first tab.

 

[erikgreen]

Re: Glassing the underside of the floor?

I like the boatbuilding technique where you glue the deck down to the stringers (and cleats as necessary) using an epoxy peanut butter mix.

No holes to leak.

All you have to worry about then is holes generated by screwing stuff down onto the deck, and you can mitigate that by using a mounting block instead of screwing onto the deck itself.

Erik

 

[F14CRAZY]

Re: Glassing the underside of the floor?

Is the epoxy alone enough to hold the deck to the stringers?

 

[Chris1956]

Re: Glassing the underside of the floor?

I do not like the idea of using just epoxy (or poly) to bed the plywood deck to the stringers. There is a chance that the plywood will not "seat" into the resin, due to some warpage or defect in the plywood. You may end up piling cement blocks on top of the plywood to bend it into shape. The stainless steel screws force the plywood to bed to the stringers. If they are countersunk and covered with cloth and resin, they will never leak.

 

[F14CRAZY]

Re: Glassing the underside of the floor?

I think it's possible to get everything right to avoid using cement blocks when epoxying it down but I don't think the tolerances of my work are that low

(I'm doing the best I can though). I've used a 4' level as a straight edge and have made my stringers about a quarter inch below the hull where the deck will be tabbed (that make sense?).

I do like the idea of putting down peanut butter/mayo between the stringer and plywood where the screws are for further sealing from beneath . I also think that counter sinking and all that should be good enough to keep water from entering from the top

 

[capri1600]

Re: Glassing the underside of the floor?

I am definately glassing the underside of my deck ('83 Bayliner Capri 1600). In fact, I plan to glass flat panels on both sides from which I will cut all of the wood pieces for above the deck as well. That way when I screw it together I am filleting and glassing corners instead of actually having to try to work with glass pieces on each piece of wood at wierd angles, etc. For the decking I plan on a layer or two of mat for the underside. Then a puddy of resin and flox on the top of the stringer and where the decking meets the hull sides. I totally agree with the predrilling of the holes, fill with resin or 5200 then coat the stainless screw and screw in place idea. The flox/resin will squeeze out of the seam between the stringer and the deck. The screw will be sealed inside the wood with resin or 5200 then when the whole deck is glassed the screw heads will be sealed as well. I also love the idea of mounting blocks on the deck. These could be floxed and glassed to the decking to eliminate any breach of screws into the deck at all.

 

[J. Mark]

Re: Glassing the underside of the floor?

I'm in the same boat getting ready to install my deck soon.

My plan is slightly different. I am going to bed the deck to the stringers with PL Premium and use pan head screws and washers to secure it until the glue cures. I will then remove the screws and fill all holes with epoxy before glassing the top of the deck.

Pan head screws and washers with predrilled holes should do less crushing of the wood fibers

Underside of my wood will be epoxy coated, top side gets epoxy and 3 oz glass after being tabbed in with a few layers of 10 oz glass.

If factories did their work the way the folks here tend to . . . we'd see a lot less restoration going on.