Thread Tools
Jul 07, 2019, 02:58 PM
EP 3D Flyer
feda's Avatar
Quote:
Originally Posted by Gluehand
My intention with these experiments is to (try to) create a formula for an ultra "clean" wing, with a good self-stability without any "tabs" or extra features.....eventually I may even try to do away with the tip fins (playing around with dihedral).
Reasons: Aesthetically....and the challenge in itself....

Your "ultra clean" wing is a wing without vertical surfaces? Similar to a Horten wing?

To me, the wing twist of a flying wing is like the decalage of a conventional plane. It gives the flying wing pitch stability, but at the same time creates drag.

You found the 8 degrees of twist is best for your flying wing. Does that mean that amount of twist gives your just-enough stability? More would make your wing less efficient; and less won't produce reliable flights?
Sign up now
to remove ads between posts
Jul 08, 2019, 05:46 AM
Registered User
Gluehand's Avatar
Thread OP
Quote:
Originally Posted by feda
Your "ultra clean" wing is a wing without vertical surfaces? Similar to a Horten wing?
If possible without vertical surfaces.......or at least reduced to a minimum.......
Yes, something like a Horten wing....

---------------------------------------------------------------------------------------------------------------------------------

Quote:
Originally Posted by feda
To me, the wing twist of a flying wing is like the decalage of a conventional plane. It gives the flying wing pitch stability, but at the same time creates drag.
Yes, the twist is the decalage, and obviously it creates a certain drag, but not overly so when the twist/CG/airfoils are sorted out. That's the price of stability.

---------------------------------------------------------------------------------------------------------------------------------

Quote:
Originally Posted by feda
You found the 8 degrees of twist is best for your flying wing. Does that mean that amount of twist gives your just-enough stability? More would make your wing less efficient; and less won't produce reliable flights?
Initially we found that using a flat bottomed airfoil all the way out required an unrealistic amount of twist, and still the stability wasn't really satisfying.....pitch stability was critical, not least with speed variations....this felt like a dead end.

The first encouraging leap forward happened when we tried the combo with a flat bottomed root section gradually turning into a symmetrical section at the tip.
A great difference...!...this enabled us to work with more "sensible" twist angles.
However, lower twist angles still didn't provide the required pitch stability....at 6 and also 7 a flat and stable glide was possible to acheive with a smooth and slow launch in windless conditions, but with increasing speed due to e.g. a harder launch or a small headwind gust, the wing flipped over, nose up or nose down, with no self-recover....just "stopped flying"...
Too sensitive...!

At 8 all suddenly changed...! As the CG was sorted out, we could launch this wing briskly or soft, and when launching straight up, it recovered by itself turning into a flat and nice glide, finding its own speed, just like any properly trimmed model...! So with this configuration, I would say the stabiility wasn't "just enough"....it was great...

Out of curiousity we also weighted the wing down a bit, to emulate a future micro-rc-equipment. A somewhat shorter glide of course, but the stability remained...!

Of course we also cut a 9 wing, but all we experienced was more drag and no improvements whatsoever....i.e. we reverted to the 8 wing, calling it the "winner".......

Note, I don't claim to have "invented" anything unique.....the universe of variables is infinite, and I'm sure a similar result would be acheiveable with other airfoils, twist angles etc.
I guess we just found a "lucky" combination, useable as a platform for further experiments, and I'll stick to it for a while to see whether these learnings could find a practical use......somehow......




Below: The 8 "winner" of these tests.........not made to "concours de elegance" criteria......

.
Last edited by Gluehand; Jul 08, 2019 at 06:26 AM.
Jul 21, 2019, 09:31 AM
Registered User
Gluehand's Avatar
Thread OP
Hello,

I have yet to cover my "adjustable" wing mentioned above (why is the covering part always such a hump to get over...?), but hopefully soon....

In the meantime (I note there's a lot of "meantime" here...) a bit more on the "tailless" theme...
Browsing in the Swedish magazine "Hobbyfolk" 3/1949, I found an interesting description, deriving from no less than Emmanuel Fillon, on a 2m tailless glider, which instead of reflex tabs or twist, is based on a pair of trailing edge "slats" with an inverted Clark Y section....
Watch it below:

Last edited by Gluehand; Jul 21, 2019 at 11:03 AM.
Aug 09, 2019, 07:13 AM
Gots me a good used Hobie Hawk
Steve Corbin's Avatar
When I was designing the Sling Wing folding-wing flying wing catapult glider I tried all kinds of things.

One thing that worked really well was reversing the taper, instead of a wide root chord and narrower tips I made swept-aft flying wings with the tips wider than the root.

Instead of twisting in washout or reflexing the tip trailing edges I treated the gliders like a canard design, and lowered the root area trailing edge like a flap.

Most of my designs used a sweep angle in the 12 to 16 degree range, as measured at the leading edge, They often were roll stable even with several degrees of anhedral, or "negative dihedral" if you prefer that term. Some interesting stunts were possible when extra anhedral was added and a lot of decalage in the form of lowered root trailing edge and raised tip trailing edge. The result being negative lateral stability combined with heavy positive pitch stability----the glider would roll to a steep bank and then point straight down, pick up speed and then nose up sharply. It would then roll as it was pitching to perform a wing-over, and it would repeat this, usually alternating left and right wing-overs all the way down. It was my only experience with a free flight glider alternating back and forth the turn direction, although of course I was familiar with the typical right-left or left-right powered-to-glide patterns we so often use in free flight.

The glider performed these manuevers in part due to it's having minimal directional stability, which allowed it to have sustained oscillations in yaw. The yawing motion coupled with the "extra" cathedral produced the rolls, and the large decalage kept it constantly trying to nose up, it was always seeking a stable condition but never finding it. Anyone fascinated by the mechanics of flight would appreciate observing and analyzing the flight pattern.


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion What are these cameras and are they any good? hamael Aerial Photography 5 Sep 05, 2017 12:01 PM
Discussion Are are some true but funny fun airplane facts MarkF Electric Ducted Fan Jet Talk 4 Dec 24, 2016 08:44 PM
Discussion Are there any UNIVERSAL CVD that can fit into any 1/8 truggy ? Anthology5251 Off-road Cars 5 Sep 27, 2016 12:55 AM
Discussion $150 or less FPV goggles. Do any that are not complete junk that exist any where? Bradcc402 FPV Talk 7 Apr 03, 2016 07:21 PM
Question Mobius are sooo fragile - are Runcam HD's any better? Kahnx Australia 12 Oct 16, 2015 03:04 AM