Mahogany vs White Oak

[gonesail]

same thing with maple .. it turns dark. i would go with time tested and beautiful teak.

[FloridaWriter]

Originally Posted by 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.

There are many kinds of wood you can use for your drop boards and the coamings (cockpit backrests). None of it will “turn dark” as it is being called here as long as the wood is protected by varnish or another finish (Cetal, bristol Finish, etc). Most types of wood turns dark where that finish lifts or is broken and water gets under it. This will happen with mahongany just as much as it will happen with oak or a domestic wood. Once that dark water stain happens the only way to get it out of the wood is by serious sanding to reach unstained wood below it or bleaching it--but beaching is sort of ify at best. Teak will not turn black in that way—there is enough oil in the wood fibers to protect it. However, eventually even bare teak if not cared for will deteriorate and rot.

Ipe. Tigerwood and other exotics are less money per board foot than teak, but significantly heavier than either teak or mahogany. For the coaming boards, they must bend to fit the slight curve of the cockpit. It would be extremely difficult to bend ipe to that slight curve and have the fasteners hold securely (it would take a car jack at least to force the bend). I would think tigerwood might be as difficult to bend as ipe.

Another issue that you will find with lumber is that you really need 11” wide rough cut boards for the coamings and it will be difficult to find that width unless you start with a much thicker board and have it planed down. (Alternatively, you could have narrower boards joined together to make up the width you need.)

That being said, you could use most any domestic hardwood for the project, it depends more on cost and on the color of brightwork you want for your cockpit: oak, maple, birch are all blond woods, whereas walnut or cherry would be a darker color, more similar to teak or mahogany. You could also stain a blond wood to get the more of the mahogany or teak color; however staining means that if you have to sand out a ding you will also be sanding thru the stain and the stain will have to be repaired as well as the finish.

Regardless of the wood, just keep a proper finish on it so water doesn’t get to the bare wood. The epoxy encapsulation mentioned earlier in this thread is an excellent means of thoroughly protecting the wood—as long as you use several coats of epoxy—I don’t recommend thinning it myself—I use it full strength—and several / many coats of a UV protected finish like exterior varnish.

Another alternative would be to use an HDPE type composite material. Starboard is a brand name for it (http://www.jfreeman.com/panels.html), but it is white and normally textured in color and finish. It is UV stable, and relatively strong. You can drill it, machine it, etc, but you can’t paint it. It is generally indestructable. Starboard coamings would look nice with the B29 I think and the cost is reasonable.

Finally if you wish, I will be replacing my mahogany coaming boards in the next few months and I can sell them to you. They are in excellent shape, finished in varnish and would be a drop in fit for your cockpit.

Good luck with your project,

[SV Perelandra]

Hi all, I'm a new member to this forum, but have been reading and enjoying posts for some time.

I believe that the AC refers to one side of the sheet being "A" grade, and the other being "C" grade.

Looking forward to becoming more active in the discussions, now that I'm signed up!

[fullkeel2]

Hi David its Chase good to see you on the board.
It would be great to get my hands on the combings from your boat but I think shipping them to San Francisco would cost and arm and a leg.
What do you think about the exterior AC plywood idea? I would love to get my hands on some seaboard HDPE but don’t know where I could get a good deal on it in the Bay Area, if anyone does please let me know.
I am going to be installing the Monitor wind vane that has been sitting in my kitchen and the turn blocks that will hold the control lines for the tiller will most likely need to be mounted to the cockpit combing so I want them to be very strong and the existing cracked ones needed to be replaced anyway.

[MABell]

...He is referring to the grade of the face.
"A" grade is sanded and has no defects or "plugs"
"C" grade is rougher and will have plugs - maybe even be made up of several pieces.
And to preempt the next question, they are not the same on both sides because in most applications, only one side shows.

[FloridaWriter]

Hi Chase,

These folks are in Tacoma and will cut any size to your specification. They also have different colors of Starboard and different textures: Plastic Supply, of Tacoma, WA

Plywood might work for the coamings, but you would have to encapsulate them in epoxy and probably paint them to boot. If you used 3/4 inch plywood they would certainly be strong!

How is the seahood project going?

[Pete7]

We have 3/4" ply wash boards which are capped with a hardwood, type unknown. Now 20 years old with lots of coats of varnish on them and I see no reason why they shouldn't last another 20 years. I plan to make a temp set this summer so I can bring the originals home to re-varnish.

Now what I do have is 10 tonnes of Horse Chessnut felled on the railway line behind our house, drying out slowly. If I could just think of a good use for it I would liberate it

Pete

[FrankZ]

Originally Posted by Ram

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

AC would be how the plywood is graded. See here.

[roverhi]

One way to grade Plywood is by the finish of the exterior ply. A is for clear without blemishes, B has more blemishes and but no voids from busted out knots etc IIRC, and it goes down the line with C being pretty rough with some voids from busted out knots, and being basically swiss cheese. AC plywood has one side that's good and one that isn't so pretty. AC is usually the best grade your neighborhood lumber yard sells. AB will give you two decent sides and would be my choice, if I could find it, for anything that will have both sides visible. This grading system doesn't grade the interior plys so there are interior voids with the surface graded plywoods. All exterior plywood uses the same glues as marine plywood. Marine ply is usually AA, both face veneers perfect, and very limited if any voids in the interior plys. So with marine ply, you are paying for the interior of the plywood. If you can find it and can pay for it, Bruynzeel (sp) is the Rolls Royce of plywood. It has thinner plys, more layers for the same thickness, and fine quality wood throughout. It's damned pretty plywood.

There is a big difference in the quality of plywood in spite of the grading system. Bottom trolling lumber yards typically have crappy plywood that is significantly poorer quality, poorer face sheets and LARGER interior voids than the same graded plywood from better lumber yards. Not always the case but you typically get what you pay for.