What about 4x8 house siding

[afreegreek]

the best thing you can do is buy MARINE GRADE plywood... almost every plywood failure is directly related to the adhesive used to lay it up and the quality of the glue line.. exterior grade is not much better than interior grade for a number of reasons I won't get into because everyone on this site should get busy on the net and learn about plywood themselves..

people say the extra $30 -$40 a sheet is too much money, they want something cheaper and they buy that.. then they run around looking for the $200 a gallon miracle sealer to make it work.. well it won't work.. if sealing exterior ply with paint or epoxy worked they'd use it to build boat with now wouldn't they? it's not the wood getting wet that causes problems... it's glue line failure that does. buy marine grade ply and paint it, finish it, clad it, with whatever you want.. no problems even if you have a few leaks..

[Moho]

While I absolutely agree with the marine grade being far superior, and having done the research myself. You have to keep one thing in mind.... We're not building boats. We're building little houses on wheels. Everyone always compares what we're doing to building for marine applications, when that isn't what we're doing at all.

I think Bob Henry's examples are prime canidates for this. He used a decent product (T1-11) at a good price, sealed it with a decent product (typical deck sealer) at a good price and ended up with a structure that is lasting quite well, 14 years for plywood exposed to the elements is a great life. I think the one thing to keep in mind is also the environment the teardrop is exposed to. If you live in the rainforest, T1-11 would not be a good choice. I'd go for marine at that point.

I believe this thread was started as a cost effective solution for constructing a teardrop and Bob proves the point well. It will work, will it survive a great flood and be able to be used a a boat when the trailer capsizes? Definately Not.

Always keep in mind everyones budget and application varies. Take my example, I am building a 5x10 trailer, 5 foot tall. The sheets of 3/4" marine for my application would have been almost $300 per sheet in my area, sorry I'll pay $150 for ALL the plywood and $200 for sealer and take my chances rather than paying $1200 for four sheets of marine grade.

[StandUpGuy]

the best thing you can do is buy MARINE GRADE plywood... almost every plywood failure is directly related to the adhesive used to lay it up and the quality of the glue line.. exterior grade is not much better than interior grade for a number of reasons I won't get into because everyone on this site should get busy on the net and learn about plywood themselves..
...

Marine grade plywood and exterior grade plywood use the same adhesive. The difference between the two is mostly the wood used. In a boat you need not only waterproof glue but also hull strength. You get that by voidless plys and more layers.

[hoytedow]

The other major difference between marine and exterior grade plywood is the presence of voids in the latter. In moist conditions or not properly sealed this will lead to distortion of the plywood(bubbles or raised areas). Exterior will work well if well sealed.

[afreegreek]

the best thing you can do is buy MARINE GRADE plywood... almost every plywood failure is directly related to the adhesive used to lay it up and the quality of the glue line.. exterior grade is not much better than interior grade for a number of reasons I won't get into because everyone on this site should get busy on the net and learn about plywood themselves..
...

Marine grade plywood and exterior grade plywood use the same adhesive. The difference between the two is mostly the wood used. In a boat you need not only waterproof glue but also hull strength. You get that by voidless plys and more layers.

most marine ply uses the same adhesive that some exterior grade plywood uses... true but almost meaningless... about equal to saying two boards joined by a dot of glue every 6 inches is equal to a full width, full length glue line because they are both Titebond II

[48Rob]

about equal to saying two boards joined by a dot of glue every 6 inches is equal to a full width, full length glue line because they are both Titebond II

Is there that much difference in the method used to glue the different types of plywood?
Not arguing, just want to know.

Rob

[Oldragbaggers]

about equal to saying two boards joined by a dot of glue every 6 inches is equal to a full width, full length glue line because they are both Titebond II

Is there that much difference in the method used to glue the different types of plywood?
Not arguing, just want to know.

Rob

Most of the research I've done seems to support the idea that it's not the glue, which is essentially the same glue, it's the plies that are being glued together that are the problem. In marine plywood the plies are solid sheets of real wood, no voids. The "other stuff" can have plies that are actually chopped up filler and other stuff besides sheets of solid wood, (and the face ply is much thinner than the face ply on the marine plywood). This is what makes for the voids. Voids means areas where nothing is being glued to nothing. This means that they can be more susceptible to fracture or cracking or separation. In a boat that has contant stresses on the hull this could definitely lead to failure, which is probably a bigger problem than the issue of moisture which can be addressed with various coatings.

But do our teardrops encounter any of these extremes of stresses in normal use? That's the question in my mind? How much stress does road travel actually put on the skins of our trailers? It's not like pounding against the waves I'm sure, but.....

[rollintent]

Balancing material cost against expected usefull lifetime has been my biggest struggle by far. Construction method or technique has never been a problem there are a lot of proven ways to get a quality result in that arena. Bob's experience with T-111 seems very reasonable to me after all. Let's look at it this way, a parked camper does a pretty good impression of a house in a lot of ways. Granted not all ways but a lot of ways. I am in Kansas and well maintained t-111 can last a long time on houses here. It seems to me that one of the hardest tests would be towing a trailer in the rain wich may only happen one out who knows how many trips. Here again I'm sure it depends how many miles anyone tends to go at a time. So, to meet my objectives I believe I can cover the surfaces, that take the brunt of a trailer being towed in the rain (front and roof) with some kind of impermeable material like EPDM or alluminum, etc. As I have learned in the case of my dog box, the vertical side walls have held up very well even when I used an interior grade of plywood with a coat of primer and a couple coats of exterior latex, leading me to believe that an exterior plywood with due care in finishing and sealing will meet my objectives. Even if I use common sealants that would never approach boat building quality.

Some of you guys are very impressive craftsmen and I am envious of a lot of the builds on here, believe me. Maybe I'll be ready for a high end project some day. But for now my goals are having a solid, useful trailer, and keeping cost well under what I could buy a commercial teardrop for and not spending a lot of time looking for harder to come by materials. I suspect there are not a lot of boat building supply businesses in Kansas.

Thanks for all the input from everyone.

[H.A.]

.

[48Rob]

Looks like a fun way to go camping!

Rob

[afreegreek]

about equal to saying two boards joined by a dot of glue every 6 inches is equal to a full width, full length glue line because they are both Titebond II

Is there that much difference in the method used to glue the different types of plywood?
Not arguing, just want to know.

Rob

Most of the research I've done seems to support the idea that it's not the glue, which is essentially the same glue, it's the plies that are being glued together that are the problem. In marine plywood the plies are solid sheets of real wood, no voids. The "other stuff" can have plies that are actually chopped up filler and other stuff besides sheets of solid wood, (and the face ply is much thinner than the face ply on the marine plywood). This is what makes for the voids. Voids means areas where nothing is being glued to nothing. This means that they can be more susceptible to fracture or cracking or separation. In a boat that has contant stresses on the hull this could definitely lead to failure, which is probably a bigger problem than the issue of moisture which can be addressed with various coatings.

But do our teardrops encounter any of these extremes of stresses in normal use? That's the question in my mind? How much stress does road travel actually put on the skins of our trailers? It's not like pounding against the waves I'm sure, but.....

except for Kayaks and other small boats almost no marine ply is used for making hulls.. it is almost alway used for decks, bulkheads, walls, cabins and cabinetry..

so called plywood hulls are not made using 4x8 sheets they are made with layers of veneer laid over moulds.. aka Cold Moulding

[Oldragbaggers]

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[afreegreek]

except for Kayaks and other small boats almost no marine ply is used for making hulls.. it is almost alway used for decks, bulkheads, walls, cabins and cabinetry..

so called plywood hulls are not made using 4x8 sheets they are made with layers of veneer laid over moulds.. aka Cold Moulding

Actually that is incorrect. You should check the Glen-L site. You will see many boat plans there, everything from dinks to fishing boats to sailboats built using sheet plywood and then usually skinned with fiberglass. While it may not be common for production boatbuilders to build this way, it is a very common and accepted method for homebuilders and there are many patterns available from several companies that utilize sheet ply for boat hulls, both the stitch and glue method as well as plywood over frames.

actually it is correct... those markets combined wouldn't support the marine ply industry for one day out of a year.. sure they exist but they don't even account for a rounding error in industry production.. just like homemade teardrops don't occupy the third decimal point in the travel trailer industry.. they are statistically insignificant..

[doug hodder]

I agree....while I'm certainly no production boat or tear builder I've built several of both. Home/ shade tree builders aren't supporting the bulk of the marine grade ply industry. However, having also worked in the sign industry for a number of years....my option would be to go with the MDO ply on a non aluminum clad tear, unless it's a woodie. Marine grade ply isn't necessary on a tear, but on the boats I've build, I do use it on the hull. Done both fir and mahogany. I believe that the 1088 BS certified ply does have an anti-fungicidal thing in the glues. Not sure if the regular exterior does.

What marine grade ply does have is a thicker exterior veneer and in the mahoganies as opposed to many of the other veneered plys, gives you a chance to not sand through it, unless you get carried away. Doesn't really matter if it's going to be covered with aluminum or painted, but on a woodie to be finished "bright"...that's what I've done. I get the thin stuff, and laminate it to a regular ply substrate...it's just for the grain and color. FWIW. Doug

[Oldragbaggers]

Deferring to intelligence and experience.