Choosing wood for a wood/glass Chris Craft Coho

I've returned. Earlier this year I made a post about possibly restoring a 32' lapstrake Sea Skiff that turned out to be too far gone to consider. I still swore that I wouldn't end up buying a fiberglass cruiser...

...but I did anyway. I purchased a '71 33' Catalina Coho Sedan for $620 a few months ago and had it transported to my marina's yard. I've joined the Chris Craft Commander (.com) board and they're quite helpful but they suggested I post back here (or the yacht world forums, I think, i dunno w/e lol). The Coho has large, hollow fiberglass box stringers tabbed to the hull like Commanders do but the cabin superstructure is wood instead and quite a bit of it needs replacement. The deck of the flybridge, the wood at the base of the windshields, the wood in the rear corners of the salon, the side deck cores, the piece that runs along the inside of the base of the side windows, some of the cockpit deck supports, the salon sole...it needs a lot of wood but I'm committed to doing it all, so no discussion required there I'll be removing the flybridge to replace the deck along with the plywood underneath it along the sides of the cabin structure. At least the top portion needs to go.

The Commander forum owner said I can use dimensional white oak to replace the mahogany due to its strength, rot resistance, and lower cost. I should stick with a fir based marine plywood for where plywood is needed. In exterior applications do you suggest coating with epoxy before priming and painting or is primer/paint sufficient? I've considered glassing the pieces over too. I've messed with wood and glass quite a bit when I restored my 19' Bayliner but that doesn't have any exterior wood.

There's a specialty lumber yard (LL Johnson in Charlotte, MI) that I know of and the Commander guys referred me to marine-plywood.us by Sandusky, OH and prices at either seem reasonable for what I need to do.

If you're curious this is the vessel in question.



Thanks guys

 

The wood would be luaun and not mahogany. It is commonly referred to as "philipine mahogany" as a trade name. You can use fir too which may be cheaper. Oak is not as rot resistant as many people believe. The hardness of a species is not in direct relation to its durability. For example, aromatic cedar is very rot resistant and also very soft. The boat is forty years old and would be in good shape if it had been maintained properly, so keeping it close to the original design is a good idea. Fir plywood is fine and depending on where it is used may need a coating or not. If you are only painting fir plywood, it has a tendency to check. A better solution, often used by Chris Craft is fir plywood with MDO. That is a paper like layer that keeps the wood from checking. It is usually used for outdoor billboards.

 

I would say you got a good deal. I would not use white Oak as using epoxy adhesive sometimes does not adhere well to WHITE OAK. For lumber replacement consider Cypress. It comes in all widths and thicknesses and is very ROT resistant, also not real heavy.
Sinker logs (100 Yrs. buried in mud) bring a premium price for flooring and panaling. Here are specs on cypress and I'll come back with a supplier link. http://www.connectedlines.com/wood/wood22.htm
http://www.cypressusa.com/products2.htm I am paying $2.60 a board foot + shipping. The top grade is Select # 1.
Straight grained and only some small pin knots It comeS rougH sawn so you either sand it or plane it. 1" UP TO 8/QUARTERS.

 

Menards has mahogany at very reasonable prices. There's one in Wyoming Mi, pretty close to you. Get on their web site and look at what they have. You can also special order a lot of other sizes that aren't in the store. Some of their stores are also stocking stores that have a bigger selection, others have less, but there's probably a store within driving distance that has what you need. Unfortunately they don't have marine ply.

Why use something tha CC didn't, the boat will be worth a lot more if you do it right. The cost of lumber isn't the biggest cost you are facing in a major rework, do it right and have something you can be proud of when you are done.

 

Thanks guys. The CC Commander admin that referred me to white oak said that it was originally used in the steam bent frames in Sea Skiffs but it sounds like I should stick to mahogany.

I'll check Menards. I was actually at the Wyoming location mentioned for Black Friday (woo hoo).

Is cypress commonly used in wooden boats? I have a good idea as to what wood is but I don't know much between species.

 

Cypress was used in the lower East coast in traditional wooden boats.

 

Oh, and can plywood replace planks? The cabin structure is actually dimensional rather than ply, my bad.

 

Yes, you can replace planks with ply.

 

Are there any advantages or drawbacks? From my knowledge plywood would be considerably stronger

 

On large flat panels you can sometimes reduce the framing size and increase spacing. There are less seams and therefore less likelihood of leaks. It is cheaper and faster to work with.

 

Are there advantages/disadvantages to using mahogany versus cypress? Mahogany prices through Menards aren't bad I suppose (checked online).

If its plywood thats going to be completely glassed are there reasons why I shouldn't just use building grade pressure treated ply? As I understand it it shouldn't be used indoors due to the chemicals in it

 

Mahogany is what CC used on their boats because it is light, strong, reasonalby rot resistant (better than most other light wood) and finally (and probably most importantly) because it looks rich when it is bright finished.

If you are going to paint it you can use lots of differnt kinds of wood, but if you are going to bright finish it, you will add a lot of value to the boat by using mahogany.

I wouldn't use anything but marine grade ply any place that could get wet.

 

In Michigan cypress is hard to get and expensive.

 

Plywood has two basic advantages, neither of which is strength. First it's much more dimensionally stable, compared to solid timber, especially hardwoods. Second it can cover a 32 square foot area in one shot. As far as strength, solid lumber is stronger longitudinally, but weaker across the grain. Plywood is heavier for the same thickness then solid lumber, but is used because it's dimensional stability and large panels can be supported.

If plywood is used externally on your boat, you'd be best advised to encapsulate it and sheath it in 'glass. It's just the prudent thing to do if you want it to last and be water proof.

Mahogany was used extensively, because it use to be fairly readily available (still is to a degree) and it has several good physical attributes about it, particularly it's looks under varnish and it's reputation, especially among women.

I wouldn't use cypress in anything other then structural elements. It tends to check and has other issues, which don't lend themselves well to trim work.

Marine plywood is the wise choice, though costly. Once you have a sheet of good marine plywood, compare it to the usual construction grades found at Lowe's/Depot and you'll quickly see why it costs more. You can get away with construction grades in out of the way locations, like inside cabinets, lockers, floor boards, etc., but if it's in the weather or part of the planking, you'd be foolish not to use marine grades here.

I'm familiar with your model boat and it has several common areas that should be inspected. The hull shell to deck interface is a tabbed shelf and it often rots out, which causes the deck fasteners to pull free, letting water into the deck too. You've likely discovered this. The best thing you can do is strip the super structure from the boat, make a new shelf, decks and cabin opening carlins, then reinstall the super structure if it's salvageable.

From your description, it sounds like you need to rebuild if not just replace the cabin sides, windshield framing and all of the decks. It usually easier and less costly to use the old pieces as a pattern for a replacement, rather then try to "restore" the old stuff.

Be careful with your species selections as each has specific physical properties, some better suited for certain things. Point in hand is white oak for Sea Skiff frames (ribs). They use this because they're steamed to shape, which mahogany doesn't do very well, but white oak does very well.

 

Thanks for the extra info guys.

I mostly used marine ply for my Bayliner and I definitely agree that its of better quality than typical construction grade stuff. No voids, cut out knots, more plies...1/2'' PT plywood at Lowes looks a lot like a piece of burnt toast put in the microwave for 5 minutes (a joke at my marina).

I plan on pulling the flybridge, for sure. The deck up there seems to have been bare plywood that was varnished over. The varnish is mostly peeled off and the deck has been wet for a while and is semi rotten along with at least a couple support beams in the headliner. I haven't torn into the superstructure much yet but I know for sure that the deck to cabin side caulking is bad and has let a lot of water in, rotting out the core in many places. When standing on the swim platform and looking down the decks you can see plenty of nasty bumps and dips in it. I'm hoping the "shelf" as PAR described is ok...I've looked up there and see what you mean.

As far as the exterior wood I'm willing to glass/fair/gelcoat (or paint).

Anyone know why they used a wooden cabin on a glass boat when they were already making all glass Commanders and their wooden hulls had glass cabins?