Lighten the glider

[Rick Masters]

Take off the top rigging cables, kingpost, luff lines and tips.You never get high enough to need them at Dockweiler.
Replace all cables with 1/16" cable.
Replace all tubing with carbon fiber thinwall.
Ditch the tires.
20-pound training glider!

[Frank Colver]

Without the top cables the glider would break on every hard landing. Especially with the other suggested mods it would take very little negative load to break it.

I learned this the hard way when my original design version of the Skysail didn't have a king post. First hard landing, no wheels, snapped it in half.

Better to have a training glider that can take the punishment that students will give it and need little downtime for repairs.

BTW - The sand wheels we use are very light.

Frank

[Rick Masters]

I wasn't thinking about a semi-rigid. Just a simple training glider. And I don't think carbon fiber is that easy to break.


Mysterious figure points toward kingpost area: "See. No kingpost! Told ya..."
Frank, was that you in the hat?    


"Dang! I forgot my wheels and kingpost. And carbon fiber hasn't been invented yet! I'm screwed..."

[Frank Colver]

The higher aspect ratio of today's gliders makes them also harder to ground handle without top wires keeping the wing from drooping and very loose lower cables unless the glider itself is designed very stiff, like the existing topless gliders. This need for a more ridged frame goes in the opposite direction from a super light frame design.

One can buy a lot of frame support with a few lightweight cables and kingpost and the slow flight of a big training glider even makes the drag penalty low.

One of Wills Wing concerns, when I was talking with them about a carbon Condor to reduce weight, was the susceptibility of thin carbon tubes to damage that could weaken them without anyone noticing.
Steve, the designer of the Condor, said that the flexibility of the aluminum tubes was part of the design and if I replaced them with carbon, which I was proposing to do, the handling and flight characteristics of the big glider would change for the worse, in his opinion. I can't fault him since in my opinion he designed the best basic beginner training hang glider in existence today.

I wish, when I was teaching myself to fly, I had had a Condo 330r to learn on and then progress to my Skysail. Learning on the Skysail was like learning to drive on a hot Italian sports car, but many bruises later I did learn to fly it. Good thing I was young and my glider was tough!

Frank

[Rick Masters]

I gradually progressed to ridiculously stiff gliders with double-sleeved leading edges.
It never bothered me. You learn to react sooner, sometimes with a bit more input. After a while, you don't even think about it.
I would encourage a competent tinkerer like you to try the carbon fiber for leading edges, crossbar, keel and kingpost, since you are not actually a novice, and see what you think.
Sail billow and shift is a much more important factor in handling at Dockweiler than essentially nonexistent leading edge flexing on your typical laminar low-wind days.
The angular momentum along the vertical axis will also decrease, which could actually provide an improvement in handling on such a large glider.
You may really appreciate the difference.
If it seems tight, you might try taking a bit of tension out of the crossbar.
Assuming you have 2-part LEs, you could use carbon fiber tubing between the nose and crossbar, and aluminum outboard.
Personally, I wouldn't bother, although it would be good to design the inner carbon LEs to accept the original outboard tubes, just in case.
I would think you could get it handling really well and be super light.

[Bob Kuczewski]

I gradually progressed to ridiculously stiff gliders with double-sleeved leading edges.
It never bothered me. You learn to react sooner, sometimes with a bit more input. After a while, you don't even think about it.

You've always been an exceptional pilot Rick!

[Frank Colver]

After pursuing my "carbon condor" project a couple of years ago I've dropped the idea from my to do list but I appreciate your suggestions, Rick.

Bill Watson had a carbon structures engineer friend pick out a weave and tubing diameter and wall that he said would be equivalent strength to the aluminum used on the condor. After much discussion with Mike at Wills Wing and where Steve looked at what had been picked and said it would not work and finding that WW had zero interest in helping with my "carbonizing" the condor project I decided to drop it.

Frank