[SamKellner]

Keeps me out of the pool halls and beer joints.

F

[Red]

Keeps me out of the pool halls and beer joints.
F

Yeah, Rick. you need to reconsider this.

Would you want all the pool hustlers being flat broke, and no beer left for anybody to drink?

[Frank Colver]

Here is the design as it currently evolves, showing batten lengths & a more accurate sail trailing edge as it would actually end up. Area has dropped to 278 sq ft.

I managed to get Condor 330 batten outlines into my AutoCAD drawing platform, using several techniques. Now I have scaled them down to patterns I need for the 1/5 scale model. Remember that I'm just using the front camber curves of the Condor design. It works so well on that big bird why not? I've never seen another HG with such a mild stall break.

Frank

Basic Trainer, sail & battens design.jpg (324.29 KiB) Viewed 7052 times

[wingspan33]

Frank, here's a thought for you -

Once gliders had floating cross tubes the large keel pocket became unnecessary. This is so since the sail billow shifts easily from one side to the other by way of the floating cross tube(s), so why include the redundant keel pocket? Keel pockets were very useful up until the floating cross tube came along because the pocket helped facilitate billow shift.

The floating cross tube, even with a tight keel pocket in the sail, still allows one LE to shift inward while the other shifts outward relative to which side of the sail is most loaded. I hope you can visualize my point.

Eliminating the (large/tall) keel pocket also makes the sail easier to build. The keel tube does then have to be higher at the trailing edge which will change the dimensions of the rear upper and lower wires. But the higher keel tube can also make the flair authority better.

I can attest to this last bit after owning a WW Duck. It had a good sized keel pocket and when fully flaired the washed out tips were still actually flying. This made the glider very likely to "WHACK!" since, while the central section of the sail was truly stalled, the wing tips still wanted to "lift". Hence the nose dropped and, BANG, whack time.

WW's next glider, the HP, had only a minimal keel pocket with a floating cross tube. The flair worked better because the tailing edge of the sail could be "dropped" further which, in turn, rotated the defined tips to where they too would be stalled on landing flair. The HP landed much better than the Duck.

So, I think your training glider would do fine without a tall keel pocket. The sail could be easier to make with equal roll control and the flair authority might be better.

[Frank Colver]

Thanks for that info. I thought that because the gliders I've seen since I got back into this were still using both floating CS and deep pocket, that either one by itself must not be enough. Also by virtue of my short span I'll have more roll authority.

However the keel pocket will still have to accomodate my center batten with its front camber and some reflex ear the back end.

Interesting about the tips still lifting with the center stalled causing the nose to drop to a "whack" landing. Mike Mier, when I was discussing my design with him, said that one of the problems with the current gliders was that the tips stall before the center and he said that my truncated tips would eliminate that tendency. If the tips stall first it can cause a tip to drop suddenly or a flat spin which is the characteristic of the Alpha and probably others. It's interesting that he sees early tip stall as a detriment but you found it to be a problem with landing if the tips didn't stall first. I can understand both viewpoints.

My tip twist will help, but the bottom line is to actually see how this design behaves. It's a big departure from what is being flown and the hang glider common configuration pretty much moved out of the wide chord, short span, Rogallo without a high cambered airfoil, directly to the relatively high aspect ratio sail wing with defined camber (cambered battens) of today's gliders. Nobody was interested in a stubby, low aspect ratio, high cambered, flex wing because it would have a worse glide ratio.

If my Basic Trainer works, nobody is going to set any distance records with it. I take that back - with a low sink rate and a tight circling ability give it a day with small diameter thermals, closely spaced, a favorable wind, hmm............................... Oh, wait, this is a training glider used on low hills and beach dunes only.

Frank

[Rick Masters]

Those chrome molly leading edges are looking better and better!
We may be on to something.

[Frank Colver]

SCALING CONDOR 330 RIB BATTENS TO RIB POSITIONS ON THE BASIC TRAINER.

Today, using AutoCAD LT, I scaled 330 rib #1 into each rib position length on the basic trainer (BT). If I was going to make each batten custom I would use these scaled layouts. However, I want to use Condor 330 battens as they are, except for length. This means using the same camber in the front of the batten and the rest of the 330 battens are nearly straight. These are not airfoils that continue to curve throughout their length so I can make them any length.

So, after scaling the Condor 330 #1 rib (center rib is the same as #1) to each BT rib position I then compared each one to any of the full scale 330 rib patterns to try and find close matches between the stock 330 ribs and the required BT ribs. I want to use WW Condor 330 ribs because they already have the bending forms. Here is what I came up with in getting close matches to standard 330 rib battens.

Basic Trainer rib positions:

Center use 330 rib #1 pattern.
#1 use 330 rib #1 pattern.
#2 use 330 rib #2 pattern.
#3 use 330 rib #3 pattern.
#4 use 330 rib #3 pattern.
#5 use 330 rib #3 pattern.
Diagonal tip batten use flat.

For the 1/5 scale model I'll use these same 330 rib patterns scaled down by 1/5 ( 2.4" = 12")

What a difference between doing the Skysail ribs in 1971 and this project. In '71 I made a 35mm slide photo of the airfoil I wanted to use and then projected the image onto picnic table paper taped to a wall. I moved the projector position to get each rib size scaled to its position in the wing and drew the outline with a felt marker.

Moving right along folks,
Frank Colver

[Frank Colver]

Here's a photo of the model frame with the rib battens set in position.

Frank

BT model frame with batten ribs.JPG (378.34 KiB) Viewed 6935 times

[magentabluesky]

Frank,

I like your ideas on a short span, low aspect ratio, large area, Basic Trainer.

My suggestion is to use a “Tapered Fiberglass Rod” transition from the leading edge to the tip.

With a properly engineered “Tapered Fiberglass Rod” you can control (relax) sail tension for the billow shift. The “Tapered Fiberglass Rod” will be more resilient to tip dragging in the landing flair. The rounded tip will be more efficient aerodynamically. There will be less mass out at the tip for faster roll and yaw response.

A “Tapered Fiberglass Rod” will eliminate all the bracing at the leading edge cross bar junction, simplify.

I like it!

Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away.

[Bob Kuczewski]

My suggestion is to use a “Tapered Fiberglass Rod” transition from the leading edge to the tip.

I like this idea.

• Light weight span extension.
• Curved tips.
• Natural sail tensioning.

If it can't be worked into this design, it's worth keeping in mind for future revisions.