"Bob Kuykendall" wrote in message
om...
Earlier, "Bill Daniels" wrote:

The panel has to be .125" 7075 because
it is a structural member. This is
NOT easy stuff to cut.

The last time is did this, I used a milling
machine with a fly cutter to
make the instrument holes. Now all I have
is a drill press. The tools that
I would need to buy to do this simple job
will cost more than the job
'should' cost from a CNC or waterjet shop.

I really like the results I get from waterjet and laser cutting, but
when I'm doing a onesey-twosey job I often find that it takes longer
to do the CAD layout than it does to just hack it out in the shop. And
I'm one of the guys who thinks that CAD/CAM has put high-performance
sailplane development within the reach of ordinary people like me.

Sure, the hand-laid parts of mice and men go oft awry. But somehow I'm
just not into the whole "one perfect part" thing. I prefer to have one
servicable part, and if it works OK the next one or dozen will benefit
from the experience. That's pretty much how Dick Schreder operated
through the 1960s: he'd dive into the shop in the winter, roll out a
new sailplane in the spring, win a Nationals in the summer, and then
spend the fall taking the ship apart and tracing its bits on paper to
make the drawings and plans.

I disagree about the difficulty of workage of 7075. I do a lot of work
with 7075-T6 up at the HP shop, and I think it is lovely stuff to
drill, cut, and sand. Its hardness makes for very nice, smooth cutting
with long soft chips. Nothing at all like that nasty, sticky 6061-T6
which so often yields broken drills and triangular holes. The key is
to keep the speed up.

In fact, one thing I've had good luck with is using a $16 suicide
cutter (one of those adjustable single-point things) to cut 4" or so
holes in 7075-T6 up to 1/4" thick. I get best results when I cut
half-way through, flip the piece, and then cut through from the other
side. And of course, I always use it with a pilot drill or pin, and
the workpiece is always clamped securely to the drill press table.

I've also had good luck using ordinary black carbon steel 2-1/4" and
3-1/8" hole saws from the local hardware store to bore instrument
holes in 2024, 7075, and 6061. I also use hole saws on 4130 steel, but
for that I use the bimetal kind.

I've got an old PZL airspeed indicator that I use as a guide for the
mounting holes; I put that in the big hole and then pilot-drill the
mounting holes. The PZLs tend to be on the big side, so when one of
those fits in a hole I'm relatively confident that a Kollsman or D^2
instrument will go in.

As for getting stuff economically waterjet or laser cut, you'll
eventually find a shop that you like. When I have mass quantities to
do, I shop it out with the http://www.mfgquote.com web site. I've
found a couple or three reasonable shops that way. If you do that,
though, you have to look carefully at the terms of the various
proposals. Some of those guys bury their minimum price deep in the
text of their proposal, so you don't notice until you get the bill for
your onesey-twosey job that it's actually about twice what they bid.

Thanks again, and best regards to all

Bob K.
http://www.hpaircraft.com/hp-24
:full fuselage shell molds!:

Bob, that's a nice write-up. I appreciate it.

However, I've found a shop that will laser cut the panel for $70 including
the metal. Since I don't have the 'suicide cutter' or hole saws, that looks
like a good deal.

The CAD thing is pretty easy for me. I scanned the old panel for the
outside dimensions and then carefully drew up the four different instrument
holes I needed. (80mm with the altimeter cut out, 80mm plain, 57mm plain
and 57mm with the 7:30 notch for the clock.) I just pasted them on the
panel and moved them around until I had what I liked.

I then created a photo realistic panel by photographing the instruments I
planned to use and pasting the photos into the holes using the CAD program.
I tried various panel colors before settling on the traditional flat black.
I'll have the panel black anodized after I dry fit it into the glider to
insure all the little holes are drilled.

Now I need to find a stick grip with switches to control the Microair 760
and the B50. Any ideas?

Bill Daniels