Ahoy, I'm hoping to make a wooden cap around the combing on my
cockpit. The combing top is about 3" wide and kind of an elongated
horseshoe shaped arc which measures 16 feet in total length. I started
by tracing flooring paper, then transferring that to eighth inch ply
scrap, then 3/8" wood in 2 foot sections checking each stage. The
curve is always off even on these short runs. Significantly off. Any
suggestions? I built two wooden curved sliding cabin hatches and the
cap rail sides and tops without any real problems but this is giving
me grief.
Thanks as always.

I guess there's a reason why you cannot simply lay your cap stock
directly on the combing and trace onto the stock. Have you tried
spiling? In my work as a furniture maker and cabinet maker for boats I
have had good success with spiling very large pieces to fit very uneven
curves.

My method is to use pieces of 1/8" ply, wide enough to lay my pointer
stick on and temporarily fastened together to lay in a conveniently
close approximation of the curves in question, marked so they can be
put back together exactly the same way. My pointer stick has notches
cut on one edge so that I can easily trace it's location and just as
easily lay it back in the exact location later. I then use the pointer
stick to point off points along the curve in question.

I then take everything apart and re-assemble it back in the shop, lay
the pointer stick back in the various positions such that the end point
will lay on my patterm stock. Mark all the points, connect the dots and
ta daa I've got the curve. With a little care this method works
surprisingly well.

The trick is to have a pointer stick that is thin, about 2-3 " wide and
about 12" or so long with 3 "V" cuts on one edge. When you trace the
position of the stick on your 1/8" ply material you may not be able to
get all the "V" cuts to lay on the ply but you will likely have enough
to recreate the location. The stick can lay over previous positions and
often does, but the "V" cuts allow for easy re-location. Keep your
pencil sharp and the point up against the edge when marking your
locations and locating your points.

Let me know if you have any questions.

On 4 Oct 2006 07:26:17 -0700, "Todd" wrote:


I guess there's a reason why you cannot simply lay your cap stock
directly on the combing and trace onto the stock.

I tried that first. The stock kind of rocks a little as I change body
position and my pencil changes angle as I draw anyway. I probably just
need more practice. Plus by the time I make an imperfect band saw cut
and try to sand it all true things have gone south.

Have you tried spiling? In my work as a furniture maker and cabinet maker for boats I
have had good success with spiling very large pieces to fit very uneven
curves.

My method is to use pieces of 1/8" ply, wide enough to lay my pointer
stick on and temporarily fastened together to lay in a conveniently
close approximation of the curves in question, marked so they can be
put back together exactly the same way. My pointer stick has notches
cut on one edge so that I can easily trace it's location and just as
easily lay it back in the exact location later. I then use the pointer
stick to point off points along the curve in question.

I then take everything apart and re-assemble it back in the shop, lay
the pointer stick back in the various positions such that the end point
will lay on my patterm stock. Mark all the points, connect the dots and
ta daa I've got the curve. With a little care this method works
surprisingly well.

The trick is to have a pointer stick that is thin, about 2-3 " wide and
about 12" or so long with 3 "V" cuts on one edge. When you trace the
position of the stick on your 1/8" ply material you may not be able to
get all the "V" cuts to lay on the ply but you will likely have enough
to recreate the location. The stick can lay over previous positions and
often does, but the "V" cuts allow for easy re-location. Keep your
pencil sharp and the point up against the edge when marking your
locations and locating your points.

Let me know if you have any questions.

I read your post 3 times. I think I get it now. Thanks very much.

ray lunder wrote:
On 4 Oct 2006 07:26:17 -0700, "Todd" wrote:


I guess there's a reason why you cannot simply lay your cap stock
directly on the combing and trace onto the stock.

I tried that first. The stock kind of rocks a little as I change body
position and my pencil changes angle as I draw anyway. I probably just
need more practice. Plus by the time I make an imperfect band saw cut
and try to sand it all true things have gone south.


Sometimes I use a couple of bags of lead shot on top of my stock to
hold it in place in difficult situations. Sash weights may work as
well. I know what you mean about holding your pencil straight. I've
shaved a flat face on one side of the graphite point and wood leading
to the point so that I can have a positive surface to steady the pencil
with on occassion. I also keep a supply of short stubby pencils handy
for difficult spots.

You may be able to fine tune the curve once it's mounted onto your
combing, either temporarily of permanently, by first applying masking
tape to the combing to protect it from scratches and then sanding your
work piece with 80g sandpaper to within a hair's breadth, then going to
finer grits. You can sand the masking tape almost through if your
careful, w/o scratching the surface below.

On Tue, 03 Oct 2006 03:07:27 -0700, ray lunder
wrote:

Ahoy, I'm hoping to make a wooden cap around the combing on my
cockpit. The combing top is about 3" wide and kind of an elongated
horseshoe shaped arc which measures 16 feet in total length. I started
by tracing flooring paper, then transferring that to eighth inch ply
scrap, then 3/8" wood in 2 foot sections checking each stage. The
curve is always off even on these short runs. Significantly off. Any
suggestions? I built two wooden curved sliding cabin hatches and the
cap rail sides and tops without any real problems but this is giving
me grief.
Thanks as always.


I suspect that you are capturing the cross section area of the
coaming/cap perfectly well, but you are losing the variation in
curvature, so that the result does not match.

One way I suppose of holding on to the varying slope is to make
a thin ply cap in multiple copies and to glue them up in situ, to
capture the slope.

You won't be thrilled by this approach - ply is not a solid cap to the
eye.

Supposing that you cannot place the cap stock in position to
trace the outline (which seems unlikely) there is a gruesome
alternative: measure the profile, then measure the slope every
few inches, and make a pattern of the coaming on wihch you
can make the cap.

Brian Whatcott Altus OK

On Tue, 03 Oct 2006 03:07:27 -0700, ray lunder
wrote:

Ahoy, I'm hoping to make a wooden cap around the combing on my
cockpit. The combing top is about 3" wide and kind of an elongated
horseshoe shaped arc which measures 16 feet in total length. I started
by tracing flooring paper, then transferring that to eighth inch ply
scrap, then 3/8" wood in 2 foot sections checking each stage. The
curve is always off even on these short runs. Significantly off. Any
suggestions? I built two wooden curved sliding cabin hatches and the
cap rail sides and tops without any real problems but this is giving
me grief.
Thanks as always.

For templates first I use pieces of cardboard trimmed to size and
tacked to the original with dots of hot melt.

Then I glue thick cardboard on top using big blobs/lines of hot melt.
The whole lot can then be pulled off the original quite easily.

For tricky shapes and £££ material I'd use the template to cut out a
sample piece in thin hardboard to check all is well.

cheers,
Pete.