Mahogany vs White Oak

[fullkeel2]

I need to replace my washboards, companionway frame that washboards go into, and the cockpit back boards/back rest (I am sure this is not the proper name) on my Bristol 29. I was thinking that I would use white oak as it is half the price of mahogany. A wood worker suggested I should really only use mahogany or teak but that really busts my budget. Anybody have any other ideas? I was going to finish the wood with several coats of the two part Bristol finish because I am under the impression it is the most durable finish.

[MABell]

In my various little boat projects, I attempted to use White Oak on a couple projects. Found that no matter how well you varnish the wood, the grain turns black (mold or mildew?)
This was dry wood, varnished promptly after install.
Don't know why - just what I experienced.

[slowshoes]

Yep - white oak will turn black. Better to pony up the money for mahogany or teak.

[fullkeel2]

what about marine plywood or just outdoor grade plywood.

[CharlieCobra]

Ply will delaminate after a short time. There are valid reasons why Teak or Mahogany are used...

[David_Old_Jersey]

Originally Posted by CharlieCobra

Ply will delaminate after a short time. There are valid reasons why Teak or Mahogany are used...

Given the time and effort involved to make & fit the companionway frame I would go for the Mahogany on the basis that you will only ever need to do the job once - as said, a reason why a quality wood like mahogany is used, apart from the looks.

But on the washboards I would settle on using ply - have seen 'em last well given some regular TLC. In any event no reason why you can't "upgrade" to solid wood at a later date (money & inclination permitting).

[Ram]

Im doing a rub rail on a boat and was thinking marine plywood also because of the cost, how long would you expect to get out of that??

[fullkeel2]

thanks for all the great responses. Now let me take this in a completely different direction. Are there any millable plastics that both sold in large enough lengths ie 1 foot by 6 foot and are structurally strong enough for this application?

[CharlieCobra]

Ram, it depends on the shape, how it's fastened etc. If ya use ply, be sure to coat the crap out of it with Penetrating Epoxy, especially the end grains. Then coat it with a medium viscosity epoxy, followed by a good paint because UV tears epoxy up in short order.

[Boracay]

I converted to the WEST way a few years ago and now I epoxy encapsulate (using generic 5:1 epoxy thinned 30%) every piece of wood that has the remotest chance of getting wet, followed by a couple of coats (more is better) of single pack UV protected polyurethane vanish on everything exposed to sunlight or that might get seen.

So far, not a trace of moisture in the wood.

The black would be mould so using International Everdure as the epoxy could help.

[Ram]

Originally Posted by CharlieCobra

Ram, it depends on the shape, how it's fastened etc. If ya use ply, be sure to coat the crap out of it with Penetrating Epoxy, especially the end grains. Then coat it with a medium viscosity epoxy, followed by a good paint because UV tears epoxy up in short order.

that sounds like good advice thanks-

[roverhi]

AC exterior plywood holds up very well especially if you seal the edges with varnish or epoxy. We had a temporary companionway board made out of 1/2" AC exterior plywood. Since it was temporary, we didn't put any finish on it, just left it as we cut it from a larger piece. It was light and simple to use so we just kept using the plywood and left the expensive, pretty acrylic hatch boards in a locker. Used the AC plywood for the 10 years we owned the boat. It was pretty beat up when we sold the boat but still going strong.

Think I'll save the teak hatchboards on my new, to me, boat for formal occasions and use a piece of AC for everyday use. May paint it this time so it looks better. I'd use Marine Plywood but it's too damned expensive and don't have a use for the remainder of a sheet.

Acrylic plastic (plexiglass) makes good hatchboards but it's heavy and scratches easily if it's not handled with care. It comes in many thicknesses. We used 3/4". Had a plastics shop cut and rabbet out the overlap.

[Thermal]

The black in the oak is not mold, its tannin. Not a problem except that it looks bad. Look around for a wood called ipe, its as weather resistant as teak, but harder and heavier and a bit harder to work, but often sold as decking for around $8 a board foot as opposed to $30 for teak. Another alternative is goncalo alves aka "tigerwood", slightly less weather resistant but very beautiful, and also around $8-10per bf.

[slowshoes]

[QUOTE=Thermal;413399]The black in the oak is not mold, its tannin. Not a problem except that it looks bad.

I never knew that's what that black was when oak goes black. I used white oak in an project in an old boat of mine, and it turned black in spots despite many coats of varnish. I initially thought it was rot, but when I stripped off the varnish and probed around, I found the wood was perfectly sound. No amount of bleaching or sanding got rid of the black though - now I know why.

[Ram]

Originally Posted by roverhi

AC exterior plywood holds up very well especially if you seal the edges with varnish or epoxy. We had a temporary companionway board made out of 1/2" AC exterior plywood. Since it was temporary, we didn't put any finish on it, just left it as we cut it from a larger piece. It was light and simple to use so we just kept using the plywood and left the expensive, pretty acrylic hatch boards in a locker. Used the AC plywood for the 10 years we owned the boat. It was pretty beat up when we sold the boat but still going strong.

Think I'll save the teak hatchboards on my new, to me, boat for formal occasions and use a piece of AC for everyday use. May paint it this time so it looks better. I'd use Marine Plywood but it's too damned expensive and don't have a use for the remainder of a sheet.

Acrylic plastic (plexiglass) makes good hatchboards but it's heavy and scratches easily if it's not handled with care. It comes in many thicknesses. We used 3/4". Had a plastics shop cut and rabbet out the overlap.

Never heard of "AC" plywood what oes it stan for?