RC India

.....thought I'd start my 4th SW entry with a proof of flight video of a Hand Launched Flying Wing Thermal Glider.

 https://www.youtube.com/watch?v=41YQyxktG7Q

 

 

....start of the build. Its a hand drawn TLAR airfoil to suit the thickness of the available foam.

Span: 1m
RTF : 194 grams
Wing loading : 2.60 opsf.

The video shared here is not the longest flight. Out of the 50 or so flights, there were a few in the 25+ sec range and 1 in the 40+ sec range.

It is possible to make this even lighter - sub 2opsf....next project.

wire cut foam wings.....

unable to post pics  ???... says 200kb max size !...trying....

Sir,
What's the estimated height (giving a 20sec flight)?
If it is only 20ft, it means the sink rate is only 1ft/sec. Thats fantastic.
Try running before throwing, to get better height.
If that doesn't help, add ballast.
If nothing else, at least you'll be able to establish a relationship between wing loading and sink rate!

I believe that there's no point in going below 3.5oz/sqft (Must have learnt that from Dr Mark Drela...) as it compromises launch height.

Or try tip/discus launch.
Let me try to locate Saikat sir's comment on seeing my FF TLG video...

Found it!
http://www.rcindia.org/kites-trains-free-flight-and-all-others/for-the-5th-sweepstakes-first-model-k-k-iyer/msg181515/#msg181515

I share your surprise, Iyer Sir. The results were way beyond my expectations ! Its a floater for sure and would perform far better with a proper MH 45.

.....there were several flights far better than this. It easily launches upto about 40 feet.....and then stalls. One launch was about 50+ feet....

.....also I read that tip/discuss launch for such gliders in the past did not work too well, although its tempting to try.

As regards ballast, I added a small stone right at CG and felt the sink was way faster.

of course this would not be the only video  ;D

.....while looking at it long and hard, I realized it was standing still on the launch skid on the bottom. All my windows and door were open, so there was a current of air through the room....had to shoot this.

https://www.youtube.com/watch?v=gHzx-GHpXks

Note:

1. Towards the end of the video, notice the numbers changing on the scale display.
2. The Wing has a warp - equal on both sides....looks like a gull wing.
3. The case is a perfect container for my weighing scale. Keeps its surface safe  ;D
        

Sir,
Anyone can stand on one leg on top of a FULL case of Vatisit69?, as your experience would have shown.
Vat matters is can they do it vhen its empty...
Wing sweep 69degrees presumably.
Aaargh!
(Admin please delete, after a while, as beyond the usual scope of RCI  matters...)

 a boring video of ill-prepared hot wire attempt. results are apparent. Cut 3 cores...1 ok, 2 error, 3 ok.

wire snap at 00:40

https://www.youtube.com/watch?v=LMx8uS1RqBQ&feature=youtu.be

@bmblb
You are truly the "Wing" expert on the forum I have been fortunate to be to your workshops and amazed at your builds. Great job. Looking forward to join you for the next flight of this beauty at the flying field

...the pleasure has been entirely mine, Sir.

THIS ONE is a DREAM !

https://www.youtube.com/watch?v=-RXr6EKl2Gk

 ???.....I could upload a pic on the other thread....but for this, I get the same error....unable to upload screen shot as well ....all file sizes are 1MB +....also tried one at a time  ???

Hotwire video is marked 'private'  ;D

oops ! published. i will take it off in a few days....one more item in the checklist for hot wire cutting!

.....the last few HLG builds, although encouraging....were equally frustrating...and after a few flights, I gave up.

 If at all I have come close to experiencing the joy of HLG/Thermal plane, it would be this one !

 It is now about 120 + launches old  ;D ( last few launches from this morning).

....added some weight first at the nose and flew in mostly calm air....with some gusts once in a while.  And then moved the same weight closer to the CG - it flies better this way (as Iyer Sir had suggested).

 a few improvements such as a better airfoil, reduced drag, more experimentation on CG would make it a far better flier.

 Yet to fly in really sunny weather.....

some pics.....

the build itself is quite simple - two wing halves joined together with a spar at CG line (this is optional depending on the foam - the one I used was old and floppy and in addition to the spar at CG, has spars running from root to tip at 1/3 chord.) Taping gives the required strength.

On the bottom, I pasted a 2in wide 3mm coro and hollowed out some foam for the battery, Rx and BEC (converted from an old shorted ESC). It is best to have all wires concealed - I was in a hurry and hence used the egg shell as a hatch. I have now widened the cavity for more space and taped as best as possible for a smoother airflow.

NOTE: The coro sheet is essential. One, it holds the halves together and gives the strength when the foam is hollowed out. Also useful to install the launch skid and a bungee hook if need be. Eliminating this is not a good idea.....card board, balsa would also do.....coro is better.

You can use the flutes to insert lead shots/wires for CG  ;D

Fins are 2mm coro, elevons from 3mm depron and generous amount of taping.

some more pics.....

a better pic of the warp in the wing !

I used an electric iron to TRY and remove the warp - but unsuccessfully. Set the iron on 'Wool', have an old T shirt between the wing and the iron initially and run your hand over the wing with he T shirt....you will get the hang of it when you try ! After some time, when I saw no results, I ran the iron directly and twisted the wing every which way possible - including pressing a thick paper cylinder to make a depression just ahead of the TE in order to give it a bit of 'reflex' - does'nt retain the shape for long though.

 The tape shrinks and seals up leaving you with a really tight/stiff wing ! BUT if your wing is true and straight, this is NOT necessary as it may only result in a warp.

 Ensure taping is uniform on both sides.

.....thinking of adding a bungee hook. CG is at spar and unless I modify the hook, thats where it would end - is it too far ahead ??

....also notice the skid.....it was parallel  ;D

....a close up of the skid....as no videos are yet available to share  :-\

...some learnings on launch style too - best results experienced with hard LEVEL launch with about 3-4 mm reflex. Also, change in ballast as little as +/- 6 grams resulted in noticeable difference in flight, max. alt. Launches pointing slightly up, results in kind of a stall/dive - and 'leveling out' just at the peak helps squeeze a precious second or two....hard launches pointing up results in a tight, fast loop and leveling out just as it exits helps retain the alt, and longer glides.....the control surfaces could be a bit more.

 wind, naturally makes so much of a difference and a wide range of experimentation is available to be explored such as CG location, +/- ballast (WL) , launch types, throws, airfoils, sweep angles and the terrain itself.

....with no promise of sensational maneuvers, it is largely a solitary pursuit ....and even short footage are to be cherished. Here's a short video ;D ;D

https://www.youtube.com/watch?v=p20p_XR7Q_k

 Rahul Roy(rahulroy31) from Pune was kind enough to courier me printouts of the airfoil I had requested as the same could not be exported to Word/PDF to be emailed (and after failed attempts at installing profili with his help). He reconfirmed the specs with me before printing and the courier arrived (with copies !!) within 48 hours !

 Rahul - :hatsoff:

 Despite the decent templates and my previous practice, I messed up 3 sheets of 40 mm foam !

 here are some pics :-\


 

Flight pattern improving with each launch... {:)}
Time for a HiStart now!