Choosing wood for a wood/glass Chris Craft Coho

Your experiences with checking on your old racer, Yellow, aren't a result of the wood species used, but the lack of maintenance of the surfaces. Most species will check to some degree given the right conditions, but meranti and okoume aren't commonly considered species known for checking. Now, if you leave them the sun, with limited protection and breached finishes, then you're going to have issues.

Okoume is light, bends easy and is strong for it's weight, but it rots easily. Meranti is stiffer and stronger, but doesn't bend as well, has a much more open grain that can check if loaded, it's heavier then okoume and has better rot resistance.

The choice of plywood depends on where it will live, the job it will do and other requirements. Two commonly available sheets are Aquatech, which is a BS-1088 sheet (the good stuff) and Hydrotech, which is a BS-6566 sheet and nearly as good as Aquatech, but cheaper. Both are meranti and the 6566 sheet is usually about 20% - 25% cheaper. The 6566 sheets often come with surface defects filled with a light putty, that can pop out if loaded or bent. These are treated in the fairing and smoothing process, so not a concern, unless desiring a bright finish. If you do want a bright finish, the BS-1088 sheet is the wise choice and the surface veneers are usually higher quality.

I've built entire boats from BS-6566 stock with few issues, as the Aquatech sheets are very good. These where painted boats of course. A 1/2" sheet of Aquatech is about $65 retail, while a Hydrotech sheets is about $85 retail, compared to $115 for a 1/2" sheet of Joubert BS-1088 okoume. An all Joubert BS-1088 sheet built boat will be about 20% lighter then an all meranti build, which is significant, but you have to pay for it. Much the same as a single skin 'glass build, compared to a foam cored or carbon composite 'glass build.

Simply put if you need light and strong, you have to toss more into the kitty. The same is true to a lesser extent if you want bright finishes.

 

Thank you for lall the input once again PAR. its nice knowing what options I can go with along with their advantages and drawbacks.

I do like knowing the technical info along with your personal experiences (to PAR and everyone else that has contributed)

From what I gather, I would be making a good decision to use douglas fir for the interior (cabinets, cabin sole, those panels at the top and bottom of the windows, etc. It would also be fine to use it for like my flybridge deck and cockpit deck panels, which will be glassed with epoxy and faired (havent decided on the final coating or texture yet)

Maranti would be good for my exterior cabin parts, such as the side window frames and those panels on the side of the cabin near the rear. These will be primed and painted (Interlux).

Are there any objections with the choice of materials in these cases?

 

Seems you've got a good plan, go for it . . .

 

I put in around 6 hours at the marina today and got the flybridge decking off. The beams look good despite the leaks through the deck and into the salon. Have to wonder what all this mahogany would cost new.

I'm getting a nice bonus from work next week which will be put toward the wood purchase.

Should I be concerned about some staining on a couple beams from water leaking through the deck? They're not compromised at all. Can I brush them with bleach as a precaution?

Its been suggested to me that wood that isn't exposed should still be painted but these beams have done alright for over 40 years without. Should I keep them bare? Should I paint them? I got thinking that they may have picked up the damp, nasty smell the boat has had and will linger even when all that was rotting has been replaced and painting should take care of that. Bilge paint was suggested.

Thanks again guys

 

There are three basic conditions that need to be present, for rot and other issues to ferment. A good design will deprive a structure of at least one of these conditions, which typically is good ventilation, so 40 years later, you have pretty good looking stuff. I have to admit, I've opened up a lot of structures, to find surprising results after a half a century too. This is nothing more then good thought processes at work, when the boat was designed.

As to paint, you can or can't, it's up to you. Bilge paint is nothing more than regular paint with a biocide in it. You can purchase a packet of poison and mix it into your paint (a real paint store product) to save a bit of money. Personally, I don't like to paint out of sight areas. It prevents you from seeing the wood and what's happening to it. If you get a leaking fastener, the wood will show a stain, but if it's painted, you will not see anything until the wood has rotted and deformed. This is why many older builds just used varnish or shellack in the bilge or under ceiling planks. A clear coat would be my choice for the area above, if for no other reason than to lock down smells. This is often the only way to make a fishing boat/yacht conversion possible.

 

That all makes sense PAR. What kind of clear coat are we talking? Do you mean like varnish or an automotive clearcoat?

 

When I say clear coat, I typically mean one of several options, unless I'm talking about cars, in which, as you've guessed, I'm talking about something else. Follow?

Simple varnish, Dutch oil and shellack as traditional, though modified varnishes and polyurethanes now are more common with two part polyurethanes not seen very often. The last boat I did was a clear LPU, but I was in "spray" mode and was using clear elsewhere too. After WW II boats I usually employ varnish, with shellack on pre-WW II boats.

 

Got it, thanks PAR. Reminds me of the pretty varnished bilge of a 30' CC Cavalier at my marina. Too bad these mahogany beams will be hidden by a deck and a headliner

 

Lexan headliner?

 

That would solve the problem. Wonder if I could use that above for some skylights...

 

Put some carlins around the opening(s) to carry the load and you could do it reasonably easily.

 

I got tearing into the salon more today...



The big mahogany beam below the windows is pretty rotten. We kind of discussed it but would it be alright to replace this with my own LVL made of douglas fir marine ply screwed (and perhaps epoxied) together?

 

That looks like a deck edge carlin, so it needs to be pretty tough. A laminate will work and epoxy will insure it has a pleasant life.

 

Still working at it. Is it logical to leave one half of the structure intact, just in case my extensive photo and written documentation leave me lost in putting the port side back together?

 

I wouldn't bother , just tear it out, so you have room to work. You'll remember well enough if you lose your documentation, assuming good disassembly prep (labeling).