New Plywood Helm - Help!

[ozmike]

Am making a new helm station to hold, instruments, switches etc and a new gear lever on the stb side, made a mock up first, and am now building out of 12mm marine ply, all joins were mitred to make a strong join, have glued (Epiglue, 2 part epoxy glue) and screwed with 40mm stainless screws.but no screws on angled joins, I was going to sand everything then coat with a 2 pack penetrating epoxy inside and out, prime then paint white. My question is will the joins be strong enough and not crack or should I put a layer of glass over all joins and fill and feather out if yes fibre or cloth?

[Laidback]

How about running a thickened epoxy fillet on the inside joints ?
A wooden tongue depressor the only tool.

[ozmike]

If I could just do that, it would save a lot of work on the outside, when you say "thickened epoxy fillet" does that have a fibreglass fillet in it as well, am just concerned I will get it all finished and hairline cracks show up, but was not sure that it may be going overboard glasing the outside!

[Laidback]

The unit is not very large and once in position, presumably won't move. The thickened fillet shouldn't need additional reinforcement, what with 12 mm ply and the joint seams already epoxied and screwed.

[cburger]

If it was my project and I wanted the job to last I would glass the entire unit with something like Dynel cloth, shoot with multiple coats of a Duratec high build primer, sand fair and smooth, then spray gelcoat or a quality two part paint. The issue with just plain wood is that the constant expansion and contraction will alway open up small voids, then water gets in, and you can figure out what happens next. Two layers of Dynel will be suficient
to stabalize the panels and reinforce your joints all at the same time. Additionally all end grain on the ply should be thoroughly epoxied to prevent water intrusion there, two coats minimum, I prefer three.

If you need to see some pics of this type of work let me know.

CB

[bob kingsland]

I think I would go one step further... a good sized thickened fillet on all the inside corners, then take a router and put a generous 1/4 round on all the outside corners, and then proceed as cburger has suggested, except I probably wouldn't gel coat... just the 2 part paint of your choice.

Good luck.

Best, Bob http://www.sv-restless,com

[San Juan Sailor]

If you don't glass the outside you will get cracks at the joints. Cracks allow moisture intrusion which makes for more expansion which makes for bigger cracks and it only gets worse.
I made some v boards for my San Juan 24 years ago out of jatoba and every year they would get cracks in them and the finish would go to hell no matter how many coats of varnish I would apply. Last year I glassed over the exterior and put five coats of Epifanes on them. Haven't touched them since, they still look perfect. The lesson here is- wood always moves.
Dan

[ozmike]

Thanks everyone for the advise, will do as you suggest, better safe than sorry would hate to have to redo it, will post more pics of my progress, its 8am over here so better head off to the slipway and get some materials.

[s/v Jedi]

Hmmm... how about doing the router job as explained by Bob and pull a mold of that so you can do a proper fiberglass version?! Seems like the perfect project to start with fiberglass and the end result will be near perfect and last forever.

ciao!
Nick.