[Bob Kuczewski]

Single surface airfoils like the one you sketched above, come with some disadvantages:

• The sharp front edge makes for a sudden transition into stall → hardly recoverable
• The airflow on the underside separates long before the top side → inefficient
• No space for a spar

---<)kaimartin(>---

You are absolutely correct on the first 2 counts.       

On the third count, there is plenty of space for a spar ... out there in the airflow.      

[Frank Colver]

Ah, Tyvek! We were in the very beginning of modern hang gliding, 1971 / 72 and using sheet polyethylene for "Rogollo" sails when Dupont came out with Tyvek. It looked fantastic for sail material. I inquired about purchasing some and the reply was that I would be required to buy a train car load minimum. Needless to say, the Tyvek idea was dropped quickly!

Of course times are different now, and every time I walk past the Tyvek supply in Home Depot I'm reminded of those "old days" in hang glider materials design.

BTW - I wasn't the only one who used "Rain For Rent" aluminum irrigation tubing for my leading edges (on the Skysail). Roy Haggard, among others, comes to mind. The Rain For Rent dealer, out in Perris CA, got so concerned about liability with their tubing being used for hang glider construction that we started to come up with other reasons why we were buying the pipe. It sure fit our budget at the time.

Yes, that glider in my icon picture has a "Rain For Rent" leading edge (2" OD, 6061-T6, don't remember the wall thickness).

Frank Colver

[KaiMartin]

Ah, Tyvek! We were in the very beginning of modern hang gliding, 1971 / 72 and using sheet polyethylene for "Rogollo" sails when Dupont came out with Tyvek. It looked fantastic for sail material. I inquired about purchasing some and the reply was that I would be required to buy a train car load minimum. Needless to say, the Tyvek idea was dropped quickly!

I used tyvek for a few medium sized kites in the nineties. The material was sold by the local kite store. From this experience I'd not recommend tyvek for the sail of a standard flex wing. I is much much more prone to stretching than rip-stop nylon at the same weight.

---<)kaimartin(>---

[wingspan33]

I've seen homes where the Tyvek wrapping was not quickly covered over with siding and after a good amount of sun time it was beginning to tatter. I don't think it likes UV rays.

I've thought about making wind socks out of the stuff, though.

[KaiMartin]

I've seen homes where the Tyvek wrapping was not quickly covered over with siding and after a good amount of sun time it was beginning to tatter. I don't think it likes UV rays.

True.
Tyvek is made of Polyethylene (PE). This polymer is known to be damageable by UV radiation.

---<)kaimartin(>---

[JoeF]

I've not any experience with
FULLARTICLE

Tyvek® UV-Protected Soft Structure Style 1460C

Tyvek® Style 1460C is part of the tough, durable Tyvek® sheet products family, but also has an ultraviolet (UV) inhibitor that gives it an extended outdoor life. Used in a variety of applications where drape, hand, and soft feel are of prime importance, Tyvek® Style 1460C is a proven shield from the sun, blocking 98% of the sun's damaging ultraviolet rays. With this UV inhibitor package, Tyvek® Style 1460C is uniquely suited for outdoor covering applications. The UV inhibitor is designed to extend the life of Tyvek® 1460C in applications where it is exposed to the sun.

[reluctantsparrow]

REason I thought of tyvek is windsocks and tell tales. I have made them out of old hang glider sails, strips of nylon, strips of dacron, surveyor tape of course, and Tyvek and the tyvek windsocks, streamers, and telltales last a long time.
I put up a northwing windsock in my yard one year and it was tatters the next year.
I put up tyvek wind streamers when I lived on a ranch on the backside of Dog Mountatin with its own airstrip and the tyvek lasted two seasons.
I know it sews easily because the PCT hikers (pacific crest trail) are making their own tents, tent footprints, and other gear from tyvek these days.
the Tyvek on the farm next to ours has been uncovered by siding for the entire three and 1/2 years I have lived at my present location.....I will walk over there tomorrow and see how its holding up.

[Dayhead]

I was writing as a critic on the Otto 45 thread, and I thought this may be a better place.

The basic outline for my design-in-waiting is a straight wing with a close-coupled tail, I just love looking at Otto's design and "imagineering" what it could have evolved into.

My design will have a main wing spar located at about 30% of the chord, but out in the far wingtip area it will end up much further forward, so that as loads increase due to turbulence or from maneuvering the tip area will twist and vent the extra load. This is in keeping with my desire to make the glider as light as possible.

When we strengthen a glider we add weight. Present HG designs are advertised as having been tested to carry a load rated in the US in pounds, I think it's around 1200 lbs. They aren't certified to a certain G load, but for the sake of argument let's call it 6 G's.

It seems to me that a hg capable of creating 1200 lbs of lift would weigh more than one that can only pull 600 lbs.

So my idea is to build a structure that vents extra loading past the 2G limit. I don't have any need to exceed 2G's in normal everyday soaring.

The wing will be made using materials that can bend a lot without breaking. Perhaps a spar with carbon caps and a flexible foam core would work.

The goal will be to have an airframe that maintains it's desired shape up to about the 2 G point, then as the G loading goes higher the wing bends in such a way that outboard dihedral and twist, or washout if you prefer, increase dramatically, to the point where the glider simply can't pull any more G's.

The radical distortion will increase drag greatly, rapidly slowing the glider. When the load experienced by the wing is reduced sufficiently it will return to it's regular shape.

So an engineer of such materials will be needed to make the spar so that it is stiff enough to maintain shape up to the 2G limit, and then start twisting and bending radically as loads increase.

It seems to me, an admittedly uneducated guy, that this would be one way of reducing glider weight.

I remember having a conversation with one of the Wills boys back in I guess '79 or '80 about the truck testing of HG's. He said that while testing the Raven for positive loading the airframe distorted so much that they had trouble overcoming it's drag enough to reach their goal. He said that based on his observations, the Raven probably could not be broken under positive G load while flying. Supposedly a pilot simply couldn't reach the breaking point because, while on the way there, the huge distortion would slow the glider rapidly.

Perhaps the spar could be built in such a manner as to be "preloaded", in a similar way as our leading edges in our current designs are, by pushing them into the "luff curve" sewn into the sail. This would allow the spar to maintain a desired shape up to a predetermined load, then suddenly begin distorting after that.

This would likely prevent aerobatic flight, other than rolls and wingovers anyway.

I'm looking forward to hearing from you guys about this, as weight reduction is foremost on my mind, second only to safe splat.

Steve

[Frank Colver]

"Official" notice: I have dropped the "Carbon Condor" (converted WW Condor) project.

Frank Colver

[Bob Kuczewski]

"Official" notice: I have dropped the "Carbon Condor" (converted WW Condor) project.

Frank Colver

Sorry to hear that ... but the non-carbon version is still plenty of fun to fly.  

I hope to see you next week at the Sunday Funday Frank!!!