How thin of plywood for a duck boat?

Question

how thin of plywood do i have to have to make it easy to bend( im building a duck boat) and also what kind of sealent do i have to have that is reletivly cheap

Answer 1

I would guess about an 1 inch is a good thickness. If it's too thin it will break easily. If it's too thick it will be hard to bend.

PS- Don't get cheap plywood, it tends to be kinda splintery (this will break easier.)

Answer 2

1/8" Marine Grade or some use ACX Exterior Plywood. It is said both use the same type waterproof glue. The difference is quality of the inside core. Marine grade uses better plugs for holes. You can use a 3"-4" Fiberglass tape for the seams. Polyester resin is cheaper than epoxy resin, and epoxy the best and may give you a little more work time. You can fiberglass all the outside , inside or both. But, you can go with the glass and just paint. Paint many types, some people just use Exterior House paint, some use oil based paint and some may go the expense of gel-coat. It really depends on what a person want to spend.

The link just for you to learn. I buy my fiberglass cloth and bronze nails on-line. My polyester resin I can get at most any Auto-Parts store. They not carry a large fiberglass cloth, but, they do have some. The first site is my fiberglass supply. I usually use 6 oz. cloth and not the Biaxial. The second site I use mainly for bronze ring shank nails. I use nails as much as possible as they cheaper than screws.

http://www.fiberglasssite.com/servlet/St...

http://www.epoxy5050.com/cgi-supplies/sh...

Here free plans for a JonBoat;

http://www.svensons.com/boat/?p=Utility/...

Click "Free Boat Plans" top left and there all kinds of plans.

Answer 3

Bendable plywood is very thin 1/8" or less and usually very expensive, since most of it only comes in marine grades, which you want anyway.   You have to provide duck boards (footing so you can get in and out without stepping through the hull if you don't build it up.)  You want polyurethane spar varnish also called marine varnish.

Answer 4

Went duck hunting ,long time ago( once ) in a boat homebuilt from plans.

Surprised to see it was only 1/8" plywood.

Marine grade or not...do not know.

As I recall it was bout 9' long w/ a wide beam & flat hull section.

It was reinforced w/ thin ,glassed in  ribs across bottom & had boards lengthwise to stand on.

Had a short enclosed foredeck w/ a small hatch for keeping things dry.

It was painted dull green inside & out & covered over w/ fiberglass cloth.

Fairly easy for 2 men to get off cartop.

Guess that's the reason for the thin ply & glass.

A 3Hp motor was more than enough.

Best regards

Answer 5

Really thin and bendable in conical form is 1/4" marine plywood. You will have to have a sturdy frame and this will not take a lot of pressure or banging about. Try maybe 1/4" for better results.  There is a sealant by 3M - 5200 which is white and waterproof. When that hardens it is an adheasive ans well as a watertight seal. It is NOT inexpensive but then, sealants are your life insurance when on the water, Right?  Never think cheap when building a boat. Youy life may depend on the quality of your work.  Framing for any boat using plywood can only be in one direction so the boat design must follow simple curves or conical sections.  Plywood can be curved like a cone or cylinder but it cannot bend in two direction at the same time.

Answer 6

Use 1/2" marine grade plywood for that project. You will need to be able to bend it a bit, but retain strength.  Plywood any thinner will be too flimsy, and anything heavier will be to stiff to bend.