Marine Ply

[greenchicken]

Hi,

Is Marine Ply preferable to baltic birch considering I will be painting the entire thing anyway?

[rdkng07]

Hi, I've used marine ply to build a boat, nice stuff. The premise behind the marine ply was that it is for the most part void free. You can't have voids when you're bending plywood over building forms, not to mention a potential failure at sea. Plus of course, it's not likely to delaminate.

I'm considering doing a build, but I probably won't be using marine ply. I've not completely ruled it out, but there are allot of materials that will work fine for a teardrop if properly built and protected from the elements. Having said that, I found marine ply really nice to work with and I don't think you can go wrong using it.

[tony.latham]

Baltic birch is solid. No voids. The stuff I get here in the middle of nowhere you can throw in a bucket of water and it won't delaminate. Dry it out after two weeks and nothing has changed.

My next build will be fiberglassed and then covered with a bed liner. I would hesitate to jump from raw wood to paint.

Tony

[Woodbutcher]

I have never used Marine Ply on any of my builds. All I have used for areas that show is cabinet grade plywood. I have used exterior plywood for floors.

Back in 2012 I did a test. This is a cut off from my build. It is 1/4" mahogany plywood. There are 2 coats of Rust Scat. This is the base without any color added.



I did not finish side 2. Then I left this scrap test piece out in the yard for 1 year. The plow guy even buried it in the snow pile during the winter. It still looked good in the Spring. So if the rain , sun and snow can't ruin cabinet grade plywood that is out in the weather for a year, your teardrop that is taken care of should be just fine.

Front side.


back side NO FINISH.

[edgeau]

My whole build was Marine ply. But even with that there seem to be some suppliers that are better than others. I went with that because I made skiffles for the kids to ride behind the ski boat several years ago and they are still going strong with absolutely no finish applied. Raw ply in and out of the water regularly and no delamination. Must be 4 or 5 years now.

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[Kaz]

I used baltic birch all around the camper. poly the inside and rustoleum on the outside. Planning on repaint this winter, four years old and as good as the day she rolled out of the garage. Like a wooden boat it's a labor of love. I was told by the place I bought my baltic birch from that it is not made with waterproof glue.

[swoody126]

the above suggestions used to be sound advise and would work quite well

sadly in today's world where $$$/profit drives all industries some of the materials we can source today are no longer created w/ the best bonding agents

for strictly interior work that Baltic Birch plywood is GREAT

some of the stuff avaiable today is assembled w/ water "resistant" glue instead of water "proof" glue :-(

IMHO Marine Plywood or at the least exterior stamped plywood should be used on ALL exterior surfaces(painted/sealed/undercoated or not)

water intrusion and standing inside sheet materials is certain death to the wood

the swelling of the wet fibers pulls against the glue eventually separating the plies while rot invades

the only way to insure that doesn't happen is complete(all surfaces AND edges) encapsulation w/ fiberglass set in epoxy

i know there are some here on this forum who will not agree

the question is really how much labor are you willing to invest in a project that is doomed from the git go from using materials assembled w/ potentially inferior glue?

i have seen too many projects waste away because the builder economized when sourcing materials

had the builders invested in the good stuff those projects would still be quite viable

sw

[noseoil]

I used 3/4" exterior plywood for the skeleton frames, 1/8" baltic birch for the interior & exterior skins, & then put 2 coats of polyurethane on it prior to skinning with .040" aluminum. No problems so far & it's still good. The bottom of the deck got 2 coats of urethane, followed by 2 coats of Henry's white roof coating. Inside it was 2 coats of urethane before the mattress was put in.

This seems to be sufficient so far & the only problem I've had is at the hinge where I didn't do a proper job of sealing due to my out-of-sequence on the hinge. I had to lift it up to install some nuts for the wire runs from the solar panel. The fault was mine, not the material's used. Once the hinge was re-set with new sealant, there were no leaks & everything is nice & tight.

[Andrew Herrick]

A boat builder might spend $120 on a 4x8 sheet of Okoume plywood; a residential contractor might spend $12.75 on a 4x8 sheet of OSB. Both, oddly enough, can go the distance in the proper environments.

Obviously, true marine plywood is a pleasure to machine, assemble and finish. You can't go with it. If you don't want to spend a fortune on Okoume marine plywood, and you don't want the weight of Teak, then meranti Hydrotek is an excellent compromise of cost and performance.

With that said ... I don't use marine plywood unless I have to. Dagnam, that stuff gets expensive. Russian - not Chinese - Baltic Birch is made with an exterior glue and less than a handful of voids per sheet. It's the standard for teardrop construction, and many Baltic Birch shells have decades of use under their belt. It's great stuff.

Commodity ACX and BCX plywood is Exterior Exposure 1 rated and is an acceptable choice for a plywood shell. It should be very carefully finished, however, with attention paid to sealing all the edges. It's not particularly attractive, either. Many of those panels have Douglas Fir veneers, which will check if left exposed. Others have paper-thin Radiata Pine face veneers, some of which will disappear after only one sanding!

Some builders use cabinet-grade interior-only plywood for the shell. To me, this is a risk. Cabinet-grade plywood from a lumberyard usually has an MDF or particleboard core, which is COMPLETELY UNSUITABLE for exterior construction. Veneer-core interior plywood, unfortunately, is often at the cheap end of the spectrum ($40-$50 a 4x8 3/4 sheet). It's quite a shame, actually. Unless you're lucky enough to live in an area where it's easy to special-order plywood from big manufacturers like Roseburg and Columbia, the choices are often slim. Anyhow, back on track .... interior-grade panels work - until they don't. You don't get the forgiveness inherent in an exterior-grade plywood.

Since you plan to paint the exterior, I'd go with Baltic Birch or ACX plywood. You don't want the telegraphing of a B- or C-grade panel, and unless you like spending money, I can't imagine marine plywood will improve the build. Take your savings and splurge on a higher quality paint