Plywood Deck Core Work

[ssanzone]

while balsa is certainly, historically, the core material of choice, one should ask why they want an organic material in proximity to water...

decks are always subject to rotting because they 'lots' of holes into the core (deck hardware).

using a foam core will provide a higher threshold to the presence of water (via the aforementioned screw holes), be easier to work with / cut (form) to the size and shape of the replacement and provide better adhesion for the resin.

remember that poly wont adhere to epoxy so if 105 was there, bite the bullet, pay for the 105 and stick with it. when doing deck work, i would recommend extra slow (209) hardener which will help with self leveling and better saturation.

if you used foam core you would not need the marine plywood layer.

i am sure u already know that re-coring a deck is NOT fun. do more research and make smart decisions and you wont be redoing the core in 5 years.

gl.


-steve

[Cheechako]

Originally Posted by Ujin

Zach, I did realize the difference in height. However, it was a thought. If 1/2 should take the bend then that would be the most efficient route. That's definitely good to know about 1/2 inch.

Is your ply ok now? if so.. don't put all that stuff over it, just dry it and reglass it properly. at least you can tell it's condition from underneath also, and it's been able to breath rather than sit in a core and rot with heat and humidity.

[DeepFrz]

I think Zack has given you a lot of great info.

Just remember that any hole through a deck that is not solid fiberglass needs to be sealed with epoxy. If your deck is mainly solid except for a few wet spots I would just repair the wet spots, scarf the new plywood into the old and then follow Zack's advise on covering. Remove every piece of hardware and ensure that every hole is sealed with an epoxy annulus. Make the annulus thick enough that when you tighten the hardware bolts the pressure wont compress the plywood.

[sneuman]

Originally Posted by ssanzone

while balsa is certainly, historically, the core material of choice, one should ask why they want an organic material in proximity to water...

decks are always subject to rotting because they 'lots' of holes into the core (deck hardware).

using a foam core will provide a higher threshold to the presence of water (via the aforementioned screw holes), be easier to work with / cut (form) to the size and shape of the replacement and provide better adhesion for the resin.

remember that poly wont adhere to epoxy so if 105 was there, bite the bullet, pay for the 105 and stick with it. when doing deck work, i would recommend extra slow (209) hardener which will help with self leveling and better saturation.

if you used foam core you would not need the marine plywood layer.

i am sure u already know that re-coring a deck is NOT fun. do more research and make smart decisions and you wont be redoing the core in 5 years.

gl.


-steve

Yes, yes, of course. But it's always a cost/benefit analysis. Divinicell (or whatever) costs waaay more. With a crappy plywood core, my deck lasted 30 years, even with 1,000+ tiny screw holes to pipe the water right in. So, recoring it with balsa, sans the screw holes (and with properly bedded deck hardware), I figure it will last for at least 30 years -- probably a lot longer. Either I or the boat (or both) will be long gone by then.

Just sayin'

[Ujin]

A quick note on holes in the deck, there are twice as many as necessary. All the deck hardware was pulled and repositioned at some previous point in time. And incidentally all the deck hardware that was remounted failed and was pull up by pv and holes left open.
Many of the original bolts were left in and the heads sheered off. Some of the holes had duck tape then glass over while others just glassed over. The areas of the deck that look the best have lots of grey wood.

So to scarf in a few places would get me by, but the framing is what I am most worried about by letting it go and getting a little at a time.

And to make the world more challenging the bulwalk where the glass turns up and should bond to is a rough mess. Under that edge of the decking, most of which has just fallen apart, is the clamp bonded to the hull to support the deck and the rub rail. The deck is through bolted to that clamp every few feet.

I don't want to think about replacement of that!

I posted on the balsa manufacturers forum for input on using balsa or foam over ply, but have not had a response as of yet.

Thanks for the idea of using slow resin for the levelling.

[Cheechako]

Someone correct me if I'm wrong, but I think poly will mechanically adhere to epoxy. like paint etc. But yes, it wont chemically bond like epoxy on epoxy. I don't think poly on poly necessarily chemically bonds together when done well after the original part has cured either. (like if you are replacing a bulkhead or tabbing in something in an older boat.) The resin required for a chemical bond cannot be finishing resin and must still be tacky for the chemical bond. It does stick well if done correctly though.