MARINE PLYWOOD OR PRESSURE TREATED

[osprey170]

I need to replace a floor panel on my 170.  I've never done glass work before but it seems straight forward.  I was going to use a sheet of 1/2" plywood cut to the same dimensions as the old panel.  I was then going to get some polyester resin, coat the plywood, lay fiberglass cloth on this and coat with more resin.  Is this pretty much it?  Does the type of plywood really matter since it will be encapsulated?  Should I pay the extra $$$ and get marine grade?


The panel in the picture is the one I'm replacing.   :(
 

[RickK]

If it's just the panel and you're not going to be walking on it, 1/2" should be ok (is that what it is now?).  If it was the whole floor I would go 5/8".  (I have seen "marine grade plywood" at home depot @ $50+ a sheet and I think it was 3/4" - not sure why they call it "marine grade" though). I used 5/8" and resin coated it all around, especially the edges - that's strong enough.  Then I glassed it in and put glass bead non-skid on it (as I've posted before - search on "glass bead").  Some of the other members can comment on alternative materials that they've used.

[DEFIANT]

If you use plywood "AC" plywood is bonded with waterproof glue and will work fine.

[osprey170]

I've been doing some research and apparently marine grade plywood is used in boats because it is lighter than treated wood due to it not being treated with any chemicals.  It's also made with naturally decay resistant wood and with waterproof glues.

I'm still debating on the type of wood to use since a 1/2" sheet of marine grade costs $50 and I don't need the whole sheet.  I may go with plain ol AC as defiant suggested.

By the way Rickk half inch is what it appears to be now - with the fiberglass and resin build up I should end up with about 3/4 once done which should be very close to original thickness.  I was also thinking of glassing in a few support braces where I would normally stand to make sure it doesn't sag.

[Miguel]

Wouldn't those support braces end up supported by the gas tank?  Measure first.  If so, I wouldn't recommend them.

[DEFIANT]

I replaced all of the decking on the front half of my 222 CCP with 1/2" AC plywood 5 or 6 years ago. I used a double thickness in some areas. So far all is solod and good. It would be my choice if I were to repair another boat!

I understand the only differance between AC and marine grade is there are more filled knots in the AC. Well, there is also the differance in price!!!

[osprey170]

Defiant - Home Depot should carry AC plywood right?  I'm not a lumber specialist but I would think that all the wood would be clearly labeled correct?

Miguel - I was going to glue some 3/4" x 1 1/2" x (2" narrower than width of floor) strips crossways underneath the flooring.  I was going to use short screws to hold them in while the glue set and then glass around them.  I think this will add a great deal of support and should not touch the top of the tank.  I hav about 2" of clearance between floor and top of tank.  I agree with you about having wood touching the tank - I found out the hard way that it is a no no.

[DEFIANT]

Home Depot does carry AC Plywood. I bought two sheets for my transom rebuild there. It actually comes in weird thicknesses If I remember right I bought 15/32" and it cost around $25.00 per sheet.

[Anonymous]

Went to depot and they only had the thick stuff - found 7/16" at lowes.  Now I need to find some glass and resin - that stuff is hard to find around here without having to drive across the world.

[osprey170]

 Forgot to login - previous post is mine.

[DEFIANT]

I used West System Epoxy for both my deck and transom and would use it again!

It always takes more than expected. My transom job sucked up 7 gallons!

[warthog5]

Some thing's about plywood you should know in order to make a wise decission.

True Marine plywood is usually made of Douglas Fir.
Most of what you will find has a AB surface.
There are other type's of plywood that are designed for marine use. Meranti or Okume.
They are more expensive than Doug Fir.
Doug Fir will check if the panel is not covered with at least a thin covering of fiberglass. It will check if it is just saturated in resign and no glass.

Home Depot and Lowes here in Pensacola, Fl. used to carry 1/2in & 3/4in Doug Fir marine plywood and had a good price on it. They don't carry it anymore. This is because of 2 reason's. They didn't sell much of it, but it was partically their falt because it looked like crap and was all beat up.
There is another place in town that has 3/8,1/2 & 3/4 and it's good looking stuff. It also has a higher price tag.

With all the huricane's in the past year's the price of plywood has gone out of sight and quality has really droped of to being junk.

Most of the plywood in the home center's is Pine. Pine weigh's more than Doug Fir. That should be a consederation when using it in a boat. It all add's up.

When building a hull with plywood the wood is tortured into place, meaning that it is bent. Only a true marine grade plywood should be considered here. No void's can be tolerated.
Now with bulkheads and floor's it's not tortured, so a lesser grade can be considered. I personally wouldn't do it, but I'm a perfectionist. :)

With the diffrent grade's of plywood there are standard's. you would be wise to educate yourself of these standards before plunking your money down for substandard quality of material's.
Yes $60 to $80 for a sheet of plywood is a bunch of money, but in the overall scheme of building or repairing a boat it's nothing.

[Capt. Rick]

Noticed your gas clamps were both put on the same way.....The correct application for safety sake would be to have them opposing one another...eliminating the pinch caused at the screw.

[osprey170]

I didn't give it much thought when I put the clamps back on but what you say makes sense.  I'll probably have to go back in soon so I'll make changes then.

Thanks for the advice!