On Sun, 18 Sep 2005 10:53:39 +0200, Martin Schöön wrote:

[snip]

* Central structural member made from WRC+carbon laminate. Foil
shaped from foam cut by hot wire.

If you go this route, consider having the core cut by the folks at
flyingfoam.com. They are in business to cut wings for RC gliders and
airplanes, but a core is a core.

Cover in glass+epoxy laminate.
Note, this time the laminate is structural.
My current boards were build like this some ten years ago.
They are 2.5+ m long and has a 44 cm cord. New they weighed
12 kg each.

/Martin


--Mac

On Thu, 15 Sep 2005 22:11:16 +0000, 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.

Several people have suggested finding NACA foil software. If you don't
want to do that, I would be happy to calculate the coordinates for you and
post them here. I would need to know the desired thickness of the foil
(at its thickest point), and the chord length (fore and aft extent of the
daggerboard).

I am assuming that the daggerboard is basically rectangular when viewed
from the side.

--Mac

"Mac" wrote in message ...
[snip]
If you go this route, consider having the core cut by the folks at
flyingfoam.com. They are in business to cut wings for RC gliders and
airplanes, but a core is a core.

--Mac


http://philsfoils.com/ is reported to do this sort of thing for dinghies and multihulls.
Probably cost-justified only if you're serious about racing.

On Thu, 22 Sep 2005 09:42:15 -0400, Jim Conlin wrote:


"Mac" wrote in message
... [snip]
If you go this route, consider having the core cut by the folks at
flyingfoam.com. They are in business to cut wings for RC gliders and
airplanes, but a core is a core.

--Mac


http://philsfoils.com/ is reported to do this sort of thing for dinghies
and multihulls. Probably cost-justified only if you're serious about
racing.
[snipped HTML]

Cool, I didn't know about philsfoils. But I don't think that flyingfoam is
very expensive.

I got a quote from them once, but I don't remember the details. Then
again, I don't have a lot of free time, so what seems reasonable to me
might seem expensive to others.

--Mac

On Thu, 22 Sep 2005 03:44:33 +0000, Mac wrote:

Several people have suggested finding NACA foil software. If you don't
want to do that, I would be happy to calculate the coordinates for you and
post them here. I would need to know the desired thickness of the foil
(at its thickest point), and the chord length (fore and aft extent of the
daggerboard).

Or go he http://www.ae.uiuc.edu/m-selig/ads.html for free section
coordinates.

/Martin

I bought a good 3.5" power planer and cut it down in 30 minutes. I used a
belt sander to smooth the lines out, and a router table to radius the front
and back.

Tomorrow I will see if it fits. (the boat is 30 miles away, with no
electricity) Since oak is 40% heavier than mahogany and the finished oak
board is only 20% heavier than the mahogany board, I must have made it
thinner than I intended; but since oak is also 50% stronger than mahogany,
that shouldn't matter.

It may not be a perfect mathematical airfoil, but it is pretty close to the
(unpracticed) eye.

.. I must have made it
thinner than I intended; but since oak is also 50% stronger than mahogany,
that shouldn't matter.

maybe, maybe not. if it's too thin for the slot it can vibrate while
sailing. you can always build it up with a fibreglass coating to make it
fit better. with wood you can always take more off, but you can't put it
back on. that's what fibreglass is for, although it makes the product heavier.

--
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"William R. Watt" wrote in message
...

with wood you can always take more off, but you can't put it
back on.

A carpenter is a whittler who knows when to quit.

Ed

"William R. Watt" wrote in message
...

.. I must have made it
thinner than I intended; but since oak is also 50% stronger than
mahogany,
that shouldn't matter.

maybe, maybe not. if it's too thin for the slot it can vibrate while
sailing. you can always build it up with a fibreglass coating to make it
fit better. with wood you can always take more off, but you can't put it
back on. that's what fibreglass is for, although it makes the product
heavier.

I was thinking that myself, but I am unsure about the technique. I have
done fiberglassing, but not on something like that.
Would it be reasonable to staple the glass in place, and then apply the
epoxy; while working on waxed paper?

In article ,
"Ed Edelenbos" wrote:

"William R. Watt" wrote in message
...

with wood you can always take more off, but you can't put it
back on.

A carpenter is a whittler who knows when to quit.

Ed

a "journeyman" is a guy who knows how to fix his fux ups.

if wood is going near water, it needs several coats of epoxy. read
directions about application and secondary bonding. fiberglass cloth is
imbedded in wet epoxy using paint brush and squeegee. see directions for
weight of cloth and radius of corners glassed over. second and third
coats of epoxy/filler yield smooth surface and built up(squared) corners.
good luck.