Vans RV-G glider

Hmmm....

I was wondering if metal gliders have an L/D disadvantage
due to the metal, or because of the lousy rivets and
poor wing airfoil and draggy struts (of the SGS gliders,
for example).

Is it possible to make a retract gear metal glider with
flush rivets and a carry-through spar which would give
40:1 ratio, or is metal just a substance that won't
allow the shapes or fine tolerances needed to make such
a wing?

Vans seems to do an excellent job selling very high
quality kits with very nice wings (metal). I wonder
if they'd consider selling a Quickbuild glider kit?

"Mark James Boyd" wrote in message
news:3fa6166d@darkstar...
| Hmmm....
|
| I was wondering if metal gliders have an L/D disadvantage
| due to the metal, or because of the lousy rivets and
| poor wing airfoil and draggy struts (of the SGS gliders,
| for example).
|
| Is it possible to make a retract gear metal glider with
| flush rivets and a carry-through spar which would give
| 40:1 ratio, or is metal just a substance that won't
| allow the shapes or fine tolerances needed to make such
| a wing?
|
| Vans seems to do an excellent job selling very high
| quality kits with very nice wings (metal). I wonder
| if they'd consider selling a Quickbuild glider kit?

I believe there is a glider in the mind of their designer,
but there are other projects to be completed first
My memory (likely to be faulty !) tells me it was to be the
RV11.
Cheers, John G.

My Caproni A21S Calif is an all-metal side-by-side twoseater. Finish is in a
way that you don't see any rivets, L/D is 41.5.

You pay an additional 10% of strucrural weight increase for having it in
metal (comparison to a janus C model - about the same wing span, the same
airfoil and pretty exactly the same polar). In a serial production, the cost
of a Calif is *way* higher than the cost of a Janus (that's why Calif's are
no longer in production).

If you want higher performance, it would mean more aspect ratio and less
airfoil thickness - and then metal would get really heavy.

--
Bert Willing

ASW20 "TW"


"Mark James Boyd" a écrit dans le message de
news:3fa6166d@darkstar...
Hmmm....

I was wondering if metal gliders have an L/D disadvantage
due to the metal, or because of the lousy rivets and
poor wing airfoil and draggy struts (of the SGS gliders,
for example).

Is it possible to make a retract gear metal glider with
flush rivets and a carry-through spar which would give
40:1 ratio, or is metal just a substance that won't
allow the shapes or fine tolerances needed to make such
a wing?

Vans seems to do an excellent job selling very high
quality kits with very nice wings (metal). I wonder
if they'd consider selling a Quickbuild glider kit?

See: http://www.soaridaho.com/Schreder/


"Mark James Boyd" wrote in message
news:3fa6166d@darkstar...
Hmmm....

I was wondering if metal gliders have an L/D disadvantage
due to the metal, or because of the lousy rivets and
poor wing airfoil and draggy struts (of the SGS gliders,
for example).

Is it possible to make a retract gear metal glider with
flush rivets and a carry-through spar which would give
40:1 ratio, or is metal just a substance that won't
allow the shapes or fine tolerances needed to make such
a wing?

Vans seems to do an excellent job selling very high
quality kits with very nice wings (metal). I wonder
if they'd consider selling a Quickbuild glider kit?

(Mark James Boyd) wrote in message news:3fa6166d@darkstar...
Hmmm....

I was wondering if metal gliders have an L/D disadvantage
due to the metal, or because of the lousy rivets and
poor wing airfoil and draggy struts (of the SGS gliders,
for example).

Mark,

Depends what you mean by an L/D disadvantage. If all you care about
is max L/D, then sure you can make a metal (or wood) glider with a low
min sink and good L/D max. But if you want high performance at higher
speeds, then metal and wood start to show their disadvantages. If you
are willing to spend a LOT of time maintaining the wing surface
(filler, etc) then metal used to be competitive (see all the HPs,
etc). But Schweizer tried to compete with glass with the 1-35 (and
partially so with the 1-34) and failed - there is just no way to
economically get and maintain the laminar flow necessary.

During the 60s there were lots of attempts to make competitive metal
high performance (home-built, mainly) gliders, with mixed success.
Read Moffat's "Winning on the Wind"; he does some great comparisons -
an even thought that a combination glass/metal construction would be
optimum. But time seems to have proven him wrong, at least at
present, and at least at the upper end of the performance spectrum.

Now, for a fun to fly, sports class level glider, metal has it's
advantages, obvioulsly - as all those Blaniks prove!

And there is no way any metal plane is going to feel as nice to the
touch as a glass one, IMHO!

Kirk
LS6 driver and 2-32 fan

John wrote.
I believe there is a glider in the mind of their designer,
but there are other projects to be completed first
My memory (likely to be faulty !) tells me it was to be the
RV11.

Van flies a Ventus 2M, maybe he is conducting research?
JJ Sinclair

Earlier, (Mark James Boyd) wrote:

Is it possible to make a retract gear metal glider with
flush rivets and a carry-through spar which would give
40:1 ratio...?

Yes. All it takes is good attention to detail during construction. And
after that, it takes microballoon mix, primer, paint, and lots of
sandpaper and elbow grease, reapplied biennially or as necessary. The
old Sierra Press soaring books are rife with takes of re-refilling all
the dings, rivet dimples, and seams in the old HPs, Prues, Schweizers,
and Laister ships. Been there, done that, got the bondo-smeared
T-shirt.

I remain firm in my conviction that the most cost-effective way to
achieve the smoothness and fidelity to contour required to get 40:1
glide ratios is with female-molded composites. Dick V. knows this from
his soaring contest experience. It's not the only way, and it's not
the best way for everybody or every situation. But where (quantity
~3), it's pretty much the cheapest and least labor-intensive way.

It's why I'm spending a ton of money making full-size wing molds for
the HP-24 and its derivatives. I spent years messing around with
various sheetmetal and moldless composite schemes. And every path led
back towards female-molded composites in full-size molds. So I'm
making wing molds. Some say I've gone over to the dark side. But once
I finish the molds, these wing sets will darn near build themselves.

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com/hp-24

Why would anyone even consider building a metal glider when you can buy the all
composite Apis 13 or 15m kit with 400 hrs. build time. There is just no
reasonable way to duplicate the accuracy of a glass airfoil in metal. Were I
inclined to build a glider the Apis would be it.

JD

Laister LP-15 Nugget.. all metal wing, bonded like the Grumman's of old AA-5
etc.. no rivets showing.. reflex flaps.. SSA book says 36/1.. but it's old
technology..

BT


"Mark James Boyd" wrote in message
news:3fa6166d@darkstar...
Hmmm....

I was wondering if metal gliders have an L/D disadvantage
due to the metal, or because of the lousy rivets and
poor wing airfoil and draggy struts (of the SGS gliders,
for example).

Is it possible to make a retract gear metal glider with
flush rivets and a carry-through spar which would give
40:1 ratio, or is metal just a substance that won't
allow the shapes or fine tolerances needed to make such
a wing?

Vans seems to do an excellent job selling very high
quality kits with very nice wings (metal). I wonder
if they'd consider selling a Quickbuild glider kit?

The Peterson Javelin was built mostly out of metal and domed rivets.
The company carried out tests on the rivet shapes and reckoned there
was no difference between flush and domed. Furthemore they obtained
thier own 'cheap' rivets which they had FAI approved which saved them
a fortune.

The report can be found on the SSA website under the articles on
flight tests of various gliders.

Of course this relates to the 'then' technology, 'now' may be
completely different