Centerboard Wood

[trial1]

I am in the process of building a centerboard for an O'day Daysailer - I plan on using a wood core wrapped in fiberglass. My question is regarding the type of wood for use as the core. I know a lot of people use Sitka spruce, cedar, and mahogany but beyond that, I still feel somewhat in the dark.

For the Cedar, are people using spanish or aromatic?
For the spruce, is this the same as construction grade spurce (i.e. grade 2 +) or can you find knot-less Sitka?

Also, would a grade 1, quarter board red wood be an appropriate substitution for any of the above?

Thanks for any help.

Trial

[Raggi_Thor]

I think you can use any kind of wood as loong as the fiberglass is strong enough to keep it stable.

[PAR]

Wood cores are as bad as steel cores under 'glass, for use in a centerboard. It's just a mater of time before the board gets a ding and lets moisture seep in and swell the wood. The result is a not pleasant, many times jamming the swollen thing inside the case, splitting it as well.

This is a time when inert materials should be strongly recommended, solid 'glass, HDPE, aluminum, foam core or other material that isn't going to change dramatically with moisture gain. The same is true of rudder blades.

[CapKos]

I have a 42 years old boat (she is as old as I am). The CB is build from mahogany ply as well as the boat. I have no problems with that. Please note that the fastening is with galvanized nails, no epoxy or glass.

[PAR]

I'm not saying it isn't done or that good examples don't exist, but that there are far better materials that don't have issues at all, like HDPE. I'm glad you've had such good fortune with your 40 year old board, but this is easily the exception, not the rule for that material.

[CapKos]

Hi Par,
What is HDPE? I’m agreeing with you that should use the best materials available, but imagine a nice looking classical wooden boat with aluminum deck for example . Seriously, the CB case (not the board) takes very strong torsion forces and coating with epoxy/glass will not be the best. The clots will certainly crack and then will rot even faster. However how to attach/bound aluminum plates to the wood?

Concerning my boat, there is neither magic here nor good fortune. Simple the boat was well build by good materials and correctly maintained during the years. If you forgot Your boat in the harbor for several years she will rot and eventually sink, but if correctly maintained could last 100 years or more.

All the best,
CapKos

[PAR]

HDPE is High Density Poly Ethylene, a plastic that is perfect for a number of things, rudder blades and center/daggerboards in particular. I use it to help solve several different issues.

You boat sounds like it's had good care and low hours of service in it's long life. This makes things live longer then average and is currently, a not often seen bit of seamanship.

No one except the fish will see your board. Both the case and board have to tolerate high twisting loads in use. It makes no sense to me, to use a product that will eventually fail from the tasks it's expected to perform.

Aluminum can easily be bonded to wood or 'glass products. Certainly, some boats require less then ideal materials, but given the choice . . .

[trial1]

An recommendations on sources of HDPE? Basically, where do you find the stuff?

[windjammer56]

HDPE sounds very interesting. Do you buy a raw sheet and shape it with some kind of sander. Or, would you make a mold and pour it in?

[frosh]

HDPE is readily available at stores that specialize in selling foam. It has lower stiffness and ultimate strength characteristics than woods so needs more reinforcing. I have used Western Red Cedar for lightness a few times, and 2 layers of epoxy glass all over, and with care do last a very long time. Also they look really good clear finished. This timber is really easy to plane and sand. This is also how you can shape the HDPE (very messy and unpleasant) or make templates and use a hot wire cutter. If you make the core from foam and havnt reinforced enough it may snap suddenly without warning in medium to strong winds.