How to prevent delamination of plywoods?

[mikeschn]

Kayak Builders, wooden boat builders...

For those of you that have seen the de-lamination of my giant teardrop, you understand why I am asking this question...

I am planning on building an Optimized Winter Warrior for my next build. But I keep getting stuck on the materials...

If I build with pine, and cover it with aluminum, there are many screw holes where water can get in. So aluminum doesn't seem like a good choice.

If I build with plywood, does it have to be marine plywood, or can I use interior plywood? What can I protect the plywood with to prevent delamination?

Canvas?
Fiberglass?
Filon?

Notice I've been suggesting membrane type products to cover the plywood, but Filon wouldn't cover the endgrain of plywood.

So that leaves canvas and fiberglass. I could use 4 oz fiberglass and several layers of resin, seems to me that would seal the end grain of plywood. At that point, can I use interior plywood, or must I use marine plywood?

And what about canvas? Would it seal the endgrain of plywood?

Your thoughts?

Mike...

[Shadow Catcher]

Marine plywood is the Rolls Royce of plywood
" Marine plywood is manufactured from durable face and core veneers, with few defects so it performs longer in humid and wet conditions and resists de-laminating and fungal attack. Its construction is such that it can be used in environments where it is exposed to moisture for long periods. Each wood veneer will be from durable tropical hardwoods, have negligible core gap, limiting the chance of trapping water in the plywood and hence providing a solid and stable glue bond. It uses an exterior Water and Boil Proof (WBP) glue similar to most exterior plywoods. Marine plywood is frequently used in the construction of docks and boats. It is much more expensive than standard plywood: the cost for a typical 4-foot by 8-foot 1/2-inch thick board is roughly $75 to $100 US or around $2.5 per square foot, which is about three times as expensive as standard plywood. Marine plywood can be graded as being compliant with BS 1088, which is a British Standard for marine plywood. There are few international standards for grading marine plywood and most of the standards are voluntary. Some marine plywood has a Lloyd's of London stamp that certifies it to be BS 1088 compliant. Some plywood is also labeled based on the wood used to manufacture it. Examples of this are Okoume or Meranti."
As I have said the exterior of Compass Rose is Filon.
What does Camp Inn Use? I know Lefty Originals is using 3/4 marine triple coated with urethane.

[rowerwet]

my TD is covered with canvas that was put on wet with porch and floor paint, before I got to that step used the same polyurathane construction adhesive to fill the small channel I left at the top of the wall/edge of the roof joint. then I sanded the adhesive into a nicely radiused corner. the canvas for the roof I trimmed off flush with the sides, then I cut the sidewall canvas so it was about 1/4" to 3/4" folded over onto the roof, the edge was "pinked" to allow it to follow the curves. I plan on putting a strip of aluminum on the top outside edges of the roof panel to hide the overlap. I also overlapped the cloth under each edge to completely seal the end grain of the ply. same thing with the doors and windows.
I wasn't planning on a shiny finish anyway, for cheap it can't be beat, however it will take many layers of something or one thick layer to cover the texture of the canvas drop cloth I used to cover the walls. A finer more expensive grade of canvas, or any other fabric that will take paint wouldn't have the texture and pills a drop cloth does.

[RAYVILLIAN]

I did basically like rowerwet except I sealed the plywood with marine epoxy than put the material on with bullseye 123 latex primer which has to be washed off your hands with paint thinner after it dries. I did the material on the sides first and lapped it over the roof 1/2 to 3/4 inch and cut it off flush at the roof line when I did the top than covered it with 2 coats of oil base porch paint.

Gary

[Roly Nelson]

Mike, I can offer my suggestion regarding end grain plywood. When I built my woody 10 years ago, I was cautioned to use nothing but quality exterior or marine plywood. So, I went to Lowes and bought the cheapest Lauan 1/4 inch plywood they had. After 10 years and 30,000 miles, I have no delamination anywhere. Perhaps that is because I have no exposed endgrain plywood, because all of those areas are covered with overlapping pine trim member, glued and screwed in place. 3 or 4 initial coats of Spar Varnish sealed it all up when I drove through the rain while attending the 10th Dam Gathering at Lake Shasta. Since then, I brush on a brand new coat of the stuff every Spring and so far it has held out the water amazingly well. Having to do it over again, I would have chosen a higher quality plywood, simply because it looks better and perhaps both sides would be equally pleasing to the eye. I am a fierce advocate for plenty of glue, lots of screws and wooden plugs to cover the screw heads. Hey, it works for me in Calif, I hope it works for you in beautiful Mich. (been all over the lower and UP during our RV excursions, checking out dozens of your lighthouses.)
Roly ~~ the li'l ol' woody TD builder....Me. Pushing 80, still going strong. Planning on my 100th b-day in my TD

[bohemian]

The quality is remembered long after the price is forgotten, so build your teardrop with the best materials...

Wayne

[Wobbly Wheels]

Mike, I built a canoe that I later put a deck onto made from ripped strips of 1/8" doorskin. I made it out of scraps and didn't need or expect it to last more than a couple seasons. I glassed only the seams and deck and everything else got a flood coat of epoxy. I then painted it with some leftover General Paint's 'marine enamel' - a pretty common find on any hardware store shelf.
I think this will be the 8th summer for it, though I do need to repaint it this year.

Epoxy and paint...maintain the coating. UV will break down epoxy so it needs to be covered with something opaque to keep the sun off it.
I have some marine ply (D Fir) for an upcoming dory build - it was $75 Cdn for a sheet of 3/8 and weighs quite a bit more than than the 3/8 ext ply I used for the floor of the trailer. I would have used this for the trailer floor instead of the exterior, but since I'm using epoxy I didn't see an advantage good enough to justify the extra cost of replacing the marine ply.
For a boat ? Definitely
For my trailer build ? Nah...epoxy and gooey black stuff will seal it well enough.

[linuxmanxxx]

If your exterior outside shell is sealed and waterproof then the plywood type shouldn't matter. I use aluminum glued on the exterior straight over luan and since I use a complete coat of waterproof glue to bond the aluminum I have essentially sealed the luan with just the glue. I then use the flexible trim moulding and use pl premium polyurethane glue which is also waterproof to glue and seal the moulding on the corners. Then I seal the moulding edges with a layer of clear silicone and the final result is a completely waterproof exterior coated over just basic water resistant luan using the 3M 30NF neoprene water based glue. The aluminum never oilcans since the glue is flexible and flexes with the expansion and contraction of the aluminum siding. No need to use screws and puncture the aluminum unless you have a lap which I just overlap metal with front most metal or top most on top and lapped backwards or downwards to provide better leak protection for wind travelling over the surface or natural runoff of water on the camper. Lapping it I use the same glue to adhere it and then silicone the seam and use a short piercing metal screw on roof laps if you have much bend in the metal to keep it laying down ( I have to do this on my 12" radius I build on front of all my campers. I then coat the whole roof with the white elastomeric siliconized roof coating with a 10 yr rating and I have a nice looking camper that is completely sealed from the elements.

Silicone is your friend Mike use it liberally where you want to prevent any water penetration.

[schaney]

For plywood kayak and Explorer Box building I have used marine grade Okoume plywood with no problems. I have a sample piece of plywood that has been out in the weather for over four year now with Durabak on one side, all other sides including the edges unfinished. It shows no signs of delamination.

[mikeschn]

So there is hope... either seal it from the weather completely, or use marine plywood.

I'm going to test the theory on the Weekender II build, by using sandy ply from Home Depot.

The weekender II is going to be a quick and simple build, covered with fiberglass and resin.

I'm going to leave it out in the elements, as a test. The Optimized Winter Warrior will have to be next year, once I have some more answers...

Mike...