sealing wood

[computeruler]

i wanna build a cheap boat out of plywood but i cant afford marine grade plywood or firberglass cloth so i want to know whats the best way to seal it and make it water proof other then that

[BHOFM]

Porch and floor paint! Lots of it!

[duluthboats]

The importance of marine grade plywood has more to do with strength and uniformity than its resistance to water. It is often necessary to fiberglass with epoxy, cheap plywood to make up for its deficiency.

Gary

[BHOFM]

Lumber yard plywood has voids that can get water in them
and cause all the problems!

however, if you just want a cheap boat, build it and paint
the crap out of it and it will last a few years if not left
in the water for long periods of time!

I have built many weekend project boats and had them in
the water the next weekend and they lasted longer than
we thought they would and all they had was 3 or 4 coats of
good old porch and floor paint! Inside and out! Sealing the
edges of the ply is very important, we used tigerhair body
filler most of the time!

If you want a boat for a life time of enjoyment, do not
read the above statement!

[alan white]

i wanna build a cheap boat out of plywood but i cant afford marine grade plywood or firberglass cloth so i want to know whats the best way to seal it and make it water proof other then that

Paint each part before assembly, three coats porch and deck enamal, use a polyurethane or polysulfide caulk on all faying surfaces, fill all edge gaps with same, and maintain, maintain, maintain. You'll get some decent mileage out of it.

[Trevlyns]

Have a look at this thread (http://www.boatdesign.net/forums/showthread.php?t=23206&highlight=ethylene+glycol) and read up a bit on ethylene glycol.

[eponodyne]

1/4" birch underlayment ply is very low void and is glued with waterproof glue (for use in bathrooms). I make kiteboards out of the stuff. It is not at all rot-resistant so sealing is a given, but also a no-brainer.

MDO is also available, but I don't know how many thickness options there are. Many boatbuilders are using MDO to good advantage; the paper facing takes either glue or paint uncommonly well.

Ethylene glycol is one option; borax is another, just as effective, probably cheaper. Simply dissolve borax crystals in hot water until it will take no more (saturated solution) and swab on the surface needing protection. Rot fungus spores will not be able to live in this environment.

[PAR]

Anti freeze (ethylene glycol) isn't especially effective, because the glue lines don't permit much penetration into the interior veneers.

MDO comes in 3/8", 1/2" and 3/4" (maybe 1" too), but lacks the veneer count to be particular strong, though it is long lived and easily paintable.

The low buck route is paint and care. If you keep it dry, covered and out of the direct sun ashore, then you'll get some service out of the puppy.

[computeruler]

so for the borax do i put that on before or after i paint

[computeruler]

so hows this sound first use some anti freeze stuff or borax? which is better? and then use this everdure and paint?? should that give me good results?

[Trevlyns]

Here's another useful publication which should help you

Best!

[computeruler]

thanks so was what i put good? should i use borax or antifreeze first? then uverdure and then paint it?

[computeruler]

or what about using some sheetmetal? would that be even better?

[rwatson]

Sheetmetal by itself or over the wood ?

[PAR]

Good construction techniques, good material selections, full ventilation of all enclosed spaces and keeping the boat clean will do as much for the life of the wood as any topical wood preservative.

As a rule, preservatives (regardless of what they might be) are applied to raw wood only.

You can try a home made brew if you want. It's your money and boat. If in a few years you notice rot or other issues, then how much have you saved by using a home mixed concoction.

Sheet metal over the wood will work fine, IF you can guarantee moisture can't get between the metal and wood. This will likely involve epoxy and vacuum bagging the sheet metal down during the cure. Of course you'll then have to contend with the metal corroding, which will lift it free of the wood and the problems begin, not to mention the weight it will add to the boat.

Use the best materials you can afford, then take good care of it and you'll get the best service your material choices will permit.

[Butch .H]

PAR the boat I am repairing had aluminum tredplate over the deck.The fore deck was Oregan Pine and the aft deck was ply. The whole lot rotted away

[PAR]

Movement in boats can't be avoided, unless they're designed (and built to the plans) specifically to address movement. This movement pretty much guarantees that at some point, fasteners, glue lines and adjoining elements will work apart enough to permit moisture to get in between. Once this happens (usual out of sight until the worst is visible) the downward spiral of decay begins.

It's this reason that most of the old boat builders left their bilges and interiors finished bright. This way they could see when rot started to form or if a fastener was loose and staining the wood, etc. and they could get at it before major surgery was necessary.

[Petros]

The least expensive way to build is by skin-on-frame, like the way traditional native kayaks were built. I have built 8 kayaks this way using salvaged and remilled lumber, most cost about $50-60 in out-of-pocket costs. I use 9 oz raw nylon fabric (the most expensive part, about $30 worth), and then sealed with polyurethane floor finish or oil based paint. It is held together with small wood pegs and lashed joints; strong, light, flexible, inexpensive and fast to make. Even if you paid retail for everything used it would still cost less than $150 in materials. It also comes together faster than most construction methods because there very little fitting of parts together. Wood rot is seldom an issue since there are not many places to trap moisture, especially if you hang it in a garage or shop for storage. It is also a very light weight way to build, most of my kayaks weigh around 20 lbs.

I built a 14 foot sloop using this kind of construction for about $35 using all salvaged wood and supplies. I built it for a local $50 sail boat race where most people built crude rafts out of junk. We won of course since I built a real sailboat (some even accused us of cheating since the boat looks so good). It uses Tyvek house-wrap sails and a spinnaker made of disposable plastic tablecloths I got from a wedding we went to (I helped them clean up and saved them from the trash can). It uses a heavy plastic skin, but if you can find a cheap source of a fine weave synthetic fabric it should work fine. The whole sailboat weighs only about 100 lbs, I can carry on the roof of my Toyota Tercel without a rack, just a foam pad to protect the roof paint.

Even if you use ordinary 1/4 cdx plywood to build your boat you can wrap the hull in painted fabric. You wrap the outside of the hull tightly in fabric (hold in place with marine staples or wood strips at the gunwale) and paint it with an oil based paint. It will make a fine durable and waterproof hull without having to caulk any joints. Cotton fabric works too, but it will rot sooner than synthetic fabric (it should last several years, and then you just recover it).

Here is my daughter and I in Puget Sound with on first launch. Below you can see how it was built.
http://i269.photobucket.com/albums/jj48/petros58/Sailboatfirstlaunch.jpg

http://i269.photobucket.com/albums/jj48/petros58/50boatconstruction020.jpg

[BHOFM]

Some details of the mast construction please!

Beautiful work on the frame!