Hey all, thanks for all your suggestions. I found these guys on amazon, and price seems ok for marine grade ply (includes shipping):
http://amzn.to/2of2Ink
http://amzn.to/2of2Ink
Marine plywood
- Thread starter Volkswatson
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- marine plywood
Part of the problem is that I don't know where to look. I'm sure that it is here somewhere. There are lots of boat builders in the area. They have to get it from somewhere.
I went with Starboard because I knew where to get it quickly & permanently-rot-proof seemed like a good feature for a material that was being used to replace rotted pieces that I assume began as marine grade ply. If I had realized before hand that the Starboard was both heavier & less rigid, I may have reconsidered my choice. With a small amount of extra bracing, the rigidity can be put back. The extra weight is in the 15-20# range for the whole project, so the difference is not catastrophic. It's just not high performance. If this was a race boat, I would worry about that a little more.
Totally agree with Will on the use of solid wood. if it is going to be getting exposed to standing water or exterior then don't use plywood of any kind. The advantage of cabinet grade plywood on a boat is the lack of voids in the internal plys. We have all seen that "soft spot" in a piece of construction plywood where there is a void under the top or bottom layer. Not a problem if you are not caring about appearance (something always cracks the top layer right at the void) because it is getting covered up with something but that does not happen much on a boat
Wow, that's pricey! But it looks like the norm. I'm lucky to have a local lumber supply that stocks Marine fir plywood. Boat building has deep roots in our neighborhood which makes it worthwhile for them to stock it.
I used 3-4 sheets of 3/4" Fir Marine ply when I built a cockpit for my boat two years ago. I needed the structural strength of the 3/4" for a monocoque build that would stand alone to build and install. I paid less than 100 per sheet.
The only place I glassed is the cockpit well. There I applied cloth and epoxy and finished the well sides for paint. The rest of the Marine plywood is covered in decking. I designed the cockpit with dryness in mind.
What ever you build in your boat, keep that in mind. If water can get below onto anything wood, there's nothing you can do to prevent the inevitable water intrusion damage. You can only slow the damage down.
Ha! Thanks, Will. I consider myself a B wood worker. I have friends that put me to shame. But I am a good 'noodler', when it comes to stuff like this (that comes from a lifetime of home design/building). When you are doing the work, it's amazing how many ways you'll find to make it easier!O M G ! Tom.
You're a woodworking god.
- Will (Dragonfly)
The forensic work of that project taught me a lot about what wood holds up inside a boat, and what doesn't. I agree with you, if you can use solid wood in place of plywood, do it! Unfortunately, plywood is the only option in many cases.
50 + years of various areas of water intrusion showed, clearly, the results as I took the old cockpit apart. All fiberglass boats don't fair much better in this regard. Many leak like sieves (from above), after a few decades.
Solid wood vs plywood, they each have their strengths. The trick is knowing what they are and when each is better for one job or another.
Esp. in boat building.
- Will (Dragonfly)
Esp. in boat building.
- Will (Dragonfly)
Just don't make the mistake I made - using solid wood where fittings go through it that exert force along the grain. My H23 has small bulkheads (sort of like wood shelf supports) that are there solely to attach the chain plates, as the 23 does not have cabin separator bulkheads lined up with where the chain plates have to go. Water intrusion from the deck had rotted out the original plywood (which did not look like marine grade to me when I removed it). I tried solid poplar - and stupidly even aligned the grain vertically. After about 2 seasons the strain pulling along the grain split the poplar. I ended up replacing with exterior grade ply with an added layer of 1/8 luan where the 3 bolts attach the chain plate to the wood. I did glass the edges with epoxy, and now that I sealed the chain plate slot through the deck with butyl rubber it should last (well, longer than me at least).
That is not to say your application requires any such strength.
That is not to say your application requires any such strength.
If you are not going to use marine plywood you might want to look at Masonry plywood, it is designed to be used over and over again building concrete forms and has much better waterproof glues in it than regular plywood. its a bit more expensive than regular plywood, but nothing like Marine grade.
Keep in mind, marine grade plywood is about the void free core and the waterproof glue. It will rot as quickly as any wood, solid or composite. The waterproof glue just keeps it from designating and the low void core makes joinery better. That's all.
- Will (Dragonfly)