On Thu, 15 Sep 2005 22:11:16 GMT, "Toller" wrote:

My mahogany dagger board was damaged when I bought the boat used. I glued
it with epoxy and put some fiberglass around it and it has held up for a few
years, but I don't think it will last.

I bought some 8/4 white oak on ebay for almost nothing (100bf for $1.25),
and figured I will build a new daggerboard while I had something intact to
copy.

The blank is 44" long, 2" thick, and 15" wide. It weights 35 pounds.
I originally intended to cut the corners off on my table saw, but it is so
heavy that it doesn't seem particularly safe.
So, I have been going at it with my 3" belt sander and my 2" power planer.
Both would work, but they would take hours and hours of work.

Any suggestions for a good way to shape my blank into an airfoil shape?
I am thinking of buying a better planer, but hope someone here will be
resourceful.

I congratulate you on eliciting a wonderfully practical, innovative,
and helpful thread. Even the most radical contributions ("Don't use
oak!") were well-meant. Notice that suggestion of using a wood carve
blade in a circular saw? Wow! Wood propeller carvers use a router in
a kind of copier frame, profiling an existing fair copy of the blade.
I notice the respect given to mahogany on the traditional end, but
also the foam core glass or carbon approach at the leading edge end.

Iobserve in passing that the center board on the SouthCoast 22 I am
preparing, is a hefty chunk of iron - its weight so low down is of
course desirable - but that has a wind up hoist.

Brian Whatcott Altus OK

You can make transverse saw cuts and take out the wood with a chisel. Then
clean up with a plane or whatever.

That's an interesting idea that none of the woodworker I spoke to thought
of.
I will try it out on some scrap.

Question: Is this a massive plank or quarter-sawn strips glued together?
If it is a massive plank you should count on it warping.

It is two pieces (both 2" thick) glued together. I don't need it until next
spring. I can get it close, leave it for a few months, and then finish it.
Would that help?

This is probably the wrong answer but I actually mean this:
Use the oak for something else. Buy some light wood like Western Red
Cedar and shape a board. Add unidirectional carbon for bending
stiffness and strenght. Sheat in glass-epoxy and paint.

Oak is about 50% heavier than mahogany, but I actually want the weight, so
that is not a problem. Besides, it is free and the cedar would be about
$50.

Toller wrote:

Oak is about 50% heavier than mahogany, but I actually want the weight, so
that is not a problem. Besides, it is free and the cedar would be about
$50.


What you are describing is a disaster guarenteed to happen.

As someone suggested, use the oak for something else.

Might even barter it for some good foam, but these days, good white oak,
even 8/4 is cheap compared to foam, even Divinycell.

Cover the foam with some 17 oz double bias and epoxy.

SFWIW, the above describes how my rudder will be built.

Lew

What you are describing is a disaster guarenteed to happen.

Why?
The mahogany board weighs 15 pounds. The oak board should weight about 23.
Even if I hadn't just lost 7 pounds, what severe problems will the 8 pounds
cause?

I am not being argumentative; I concede I don't know anything about boat
building, and little more about sailing. But I have sailed this with my 95
pound son in it, and it is fine (if a little sluggish); why would 8 pounds
of board matter?

Toller wrote:
What you are describing is a disaster guarenteed to happen.


Why?
The mahogany board weighs 15 pounds. The oak board should weight about 23.
Even if I hadn't just lost 7 pounds, what severe problems will the 8 pounds
cause?

I am not being argumentative; I concede I don't know anything about boat
building, and little more about sailing. But I have sailed this with my 95
pound son in it, and it is fine (if a little sluggish); why would 8 pounds
of board matter?




It is not the added 8 lbs although rudders are designed to be as light
as possible.

It is that this is not a good application for white oak.

Now if you quarter saw that 8/4 stock, you can make some very nifty trim
for tha boat.


Lew

"Toller" wrote in message
...
What you are describing is a disaster guarenteed to happen.

Why?
The mahogany board weighs 15 pounds. The oak board should weight about
23.
Even if I hadn't just lost 7 pounds, what severe problems will the 8
pounds cause?

I am not being argumentative; I concede I don't know anything about boat
building, and little more about sailing. But I have sailed this with my
95 pound son in it, and it is fine (if a little sluggish); why would 8
pounds of board matter?

Without looking at the board and reading the grain, it is near impossible to
tell what it will do. Not knowing how old it is and how it was dried
muddles things further. I don't think the weight is a concern. I would
think warping, bending, settling, etc. of the board is the potential (big
word there) cause for concern. A guaranteed disaster? I hardly think so.
A likely disaster? Nah. It is yours, the board is free. The penalty will
be to redo it. Go for it, it might just work!

Ed

"Toller" writes:

Question: Is this a massive plank or quarter-sawn strips glued together?
If it is a massive plank you should count on it warping.

It is two pieces (both 2" thick) glued together. I don't need it until next
spring. I can get it close, leave it for a few months, and then finish it.
Would that help?

Some but I think it will warp sooner or later anyway. A good
epoxy seal helps slow the process. But as someone else stated:
Without being able to see your blank and how the grain looks it
is very hard to be anything but rather vague about this.

This is probably the wrong answer but I actually mean this:
Use the oak for something else. Buy some light wood like Western Red
Cedar and shape a board. Add unidirectional carbon for bending
stiffness and strenght. Sheat in glass-epoxy and paint.

Oak is about 50% heavier than mahogany, but I actually want the weight, so
that is not a problem. Besides, it is free and the cedar would be about
$50.

I would say your troubles with the white oak is more about
handling and working on it in your workshop than all-up weight
on your boat. You will spend a lot more time shaping your oak than
it takes to shape cedar.

Oh, I almost forgot. It is my experience that oak and epoxy coats
don't always work well together.

--
================================================== ======================
Martin Schöön

"Problems worthy of attack
prove their worth by hitting back"
Piet Hein
================================================== ======================

There is no need to worry about making a daggerboard, centreboard, or
rudder out of solid wood. Visit your nearest sailing facility and look at
all the centreboards, daggerboards, and rudders made of solid wood. The
fact that your board is glued up means it will not warp. You can look at
the end grain to see which way the two pieces are oriented. Put a couple
coats of polyurethane varnish on it and refinish it every few years.

I've never put epoxy resin on oak but peope who have say it's only
necessary to sand the surface of teh wood to roughen it up a bit. Oak
contains tannin, and acid, and acids dilute epoxy rdeucing its bonding
strength. One way to clean up epoxy resin that has not cured is to use
vinegar, lemon juice, or some other mild acid.


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