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.

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

snip
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.


Google for "naca airfoils"
Regards,

Bruce Nichol
Talon Computer Services
ALBURY NSW Australia

http://www.taloncs.com.au

If it ain't broke, fix it until it is....

I assume you have the old board to use for a pattern of the cross section.

I know that white oak would be difficult to shape by hand plane or any of
the power tools you mention.

For my 3" thick plywood rudder, I use a 4" disk grinder fitted with a
special wood carving wheel. This is a steel disk with chain saw teeth on
it's edge. Very aggressive cutting, so go slow and careful..

The PacNW wood carvers use these along with their regular chainsaw tip to
carve detailed statues.

Just rough out your board shape and finish with the plane or belt sander.


--
My experience and opinion, FWIW
--
Steve
s/v Good Intentions

"Toller" wrote in message
...
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'd go for the power planer. A good one can take away 1.5mm (1/16") in one
stroke, which means you can take away half of the thinkness of your blank in
16 strokes.

Meindert

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.


Use your table saw as a shaper by sliding the blank sideways over
the blade. It will leave concavities, a hollow ground shape you can
refine more easily. A well made slide jig should provide a reagulare
shape and remove most of the unwanted material.

Don't be afraid to drill a few bolt holes in your saw top to hold
special jigs, or use eccentrics to hold in guide slides.

Cut strips to sit in grooves able to slide, lay ply on top, pin with
brads, screw together from other side. with saw, route grooves the
other way, make side slider jig. Screw on a fence to enable milling.
Terry K

You can make transverse saw cuts and take out the wood with a chisel. Then
clean up with a plane or whatever. Dont' go all the way in with the saw
because the wood will not cut out smoothly. Practice on scrap first.
If you can figure out some way to do it with a power saw it allows you to
set the depth of cut.
--
------------------------------------------------------------------------------
William R Watt National Capital FreeNet Ottawa's free community network
homepage: www.ncf.ca/~ag384/top.htm
warning: non-FreeNet email must have "notspam" in subject or it's returned

"Toller" writes:

snip

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.

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

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.

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.

A WRC blank should be light enough to handle on the table saw.
Cut grooves to a depth that just 'touches' the future profile.
Use a power plane to remove material almost down to the future
profile and then continue with a hand plane and long board sanding.

Have someone calculate how much carbon you need and then use a
router to cut out some material from the WRC board so you can add
the carbon without ruining your profile.

More on boards at:
http://hem.bredband.net/b262106/Boat/dagger.html

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

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

I'd go with Martin's recommendation of materials. A white oak board, while
maybe stable, will be too heavy to handle.
Google for a NACA foil design program.
For shaping it, I'd use a router as the shaping tool. Make a slotted
'bridge' which will guide a router over the victim. The bridge can run
either the long way or cross-ways. If the bridge runs the long way, it can
be straight but rest on curved templates at the ends of the board. If the
short way, the bridge must be curved, but it will run on straight guides at
the edge of the board. I'd favor the short curved bridge, which will flex
less.
"Schöön Martin" wrote in message
...
"Toller" writes:

snip

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.

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

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.

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.

A WRC blank should be light enough to handle on the table saw.
Cut grooves to a depth that just 'touches' the future profile.
Use a power plane to remove material almost down to the future
profile and then continue with a hand plane and long board sanding.

Have someone calculate how much carbon you need and then use a
router to cut out some material from the WRC board so you can add
the carbon without ruining your profile.

More on boards at:
http://hem.bredband.net/b262106/Boat/dagger.html

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

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

toller,

I have been watching this thread, but did not have time to write until
today. There seems to be a a multple of questions here and some
interesting thoughts among the responses.

First, If you glued the damaged board with epoxy and glassed also with
epoxy, there is no reason it will not last as long as the mohogan holds
out - that may be quite some time.

Mohogany is a relatively light wood, but not that light. You will pick
up probably 10-12 pounds. It was probably choosen for it's rot
resistance and the ease of working. It is a very dimensionally stable
wood which is why it is so valued by pattern makers.

By "cut the corners off" I am guessing that you mean the long edges. If
that is the case, we need to ask more questions here.
Are you going to make this cut the entire length of the blank?
If yes, just be sure you have pusher sticks handy and a friend to catch
the plank and trim as they come out of the saw. The second cut will be
much more exciting the than the first because of the small support area
left on the trailing edge.
If no, you still need the friend, but not the pusher sticks. Plus now
the operation has a new twist because sawblades only cant one way. In
one direction, you will have to start the cut as a pocket cut and saw
out of the blank, and the other you have to stop in the blank. There is
only one safe way to do this. Shut the saw down and then retract the
blade. You will have to finsh the cut by hand.

As to the actual section, yes, you can get there with the power plane
and belt sander (look up supergrit belts - effective prices). If the
boat is a class of any kind, the class site probably has the section
available. If not, you probably want a modified four digit. I own code
for this, but I do not know if it is available on the web - search.

Cutting guide reference slots is not a bad idea, you will have a lot of
wood to hack off before you get close to the sand-to-shape phase. You
might consider doing that before you even "cut the corners off" because
it will be easier to handle the blank then.

Thinking is the Cheap thing to do.

Matt Colie (I have been at this way too long)

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.

On Sat, 17 Sep 2005 11:45:10 -0400, Matt Colie wrote:

snip
Cutting guide reference slots is not a bad idea, you will have a lot of
wood to hack off before you get close to the sand-to-shape phase. You
might consider doing that before you even "cut the corners off" because
it will be easier to handle the blank then.

Well put. This was what I intended to describe but your command of
the English language is clearly superior.

I recommend Western Red Cedar (or similar light wood) for two reasons:
1) Easier to handle both while building and on the boat.
2) Easier to work on than oak.

I have shaped plugs out of MDF-blanks this way. A plug for a rudder
1.8 m long and with a 30 cm cord took only one evening to shape.
Painting, wet sanding, rubbing and polishing took much longer.

Thinking is the Cheap thing to do.

Indeed :-)

Here are some more ideas on shaping foils if you don't want to
make molds.

* Strip planking using 6-8 mm thick WRC strips. Use external frames.
Glass+epoxy inside, join halves and don't forget that you need
a good structural member running down the middle of the foil.
The exterior will need some final shaping, then add carbon as
needed and wrap in glass and epoxy. Potentially lighter than
the massive board for big boards but more work and less robust.

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