RC India

For this project my aim is to build a glider which can carry a digital camera for aerial photography but above all it should be backpackable so that I can take it with me on hikes or on my bike.
I have started my build from scratch today. The design is based on a uav I saw on discovery. The wing is elliptical with a 2 meter span and max chord of 12 inch. The fuse is 50mm pvc tube. CF tubes for wing and tail boom are all 8mmx6mmx1000mm. The wing tips are glued together with plastic tube. Two 6mmx25mm CF rods are used as joiner for the wings. The wings are held together by tension in the bow string which also gives it a smooth polyhedral like profile. Finally there will be a piece of fabric stretched between the elliptical frame to form the wing.
I am planning to keep it under 1500 grams and powering it with Turnigy AerodriveXp SK 35-30 1100Kv motor swinging a 11x5 prop.

Wow!!! Innovative stuff after a long time!
All the best! keep us posted. 

Nice approach.. can't wait to see the finished product.. :thumbsup:

Thanks ujjwaana & medicineman1987, lets see how it turns out.

Glad to see such a thread here :thumbsup:

Teaser. Do you plan to keep a 'Flat Profile' planform of the wing aerofoil ? if so, the wing loading would be very high as such planform would not provide good lift.

Thanks anwar!
@ujjwaana
It will have a triangular airfoil, more on it here (http://www.rcindia.org/beginners-zone/basic-aerodynamics-for-rc-flying/msg41576/#msg41576). You'll get a better picture as the build progresses  :)

Right now i am stuck because i am not able to find good string for the bow. In the pictures above i have used a metal wire but i have to replace it with a string. I bought three deferent types of strings, one was not strong enough and the other two just stretched out due to the tension from the CF bow  >:(

ok i get it, great  :D, was looking forward to this. all the best for the maiden

Good one... tuned in to this thread.

All the best for the build and maiden

BTW, I have made a design of foldable delta wing sometime back. It should be back-packble as well. Will post some details later on.

-Ismail

All the best for your built.
Very Innovative....    {:)}

Great to see this thread. {:)}  Watch out for that weak area in your last photo.  :thumbsup:

Great Innovative  build , this should be a great FPV platform

Did you try Kevlar String for Tennis Rackets?
http://cgi.ebay.com/GSs-Dura-Match-19-Kevlar-Aramid-tennis-string-1-set-/130395008092?pt=LH_DefaultDomain_15&hash=item1e5c25ec5c

You may well get these in good sports stores, for a little more price. The best feature of Kevlar is that they do not stretch.

Any local supply of kevlar in sports shops? Don;t think it makes sense to buy a new racquet and stripping off the strings ;-)

Thanks for the inspiring comments guys!
@izmile would love to see your foldable delta design, if possible please post some details here.
@ujjwaana Good idea!! i'll check local sports store for kevlar string today itself. Thanks for the pointer.

Good to see something innovative. All the best for the project.
How about using the pull pull wire for the tension? Will it work? Even the catgut used on badminton racquets should be pretty stretch proof and strong enough. If you need more strength you could use the tennis one. These should be availble at shops which restring the racquets you do not need to buy a new racquet and destring it.

Ujwanna
With respect to your post at #5,
Whether one chooses a  flat plate or any other aerofoil, wing loading will not change based on the aerofoil chosen   

Great Stuff Amit..Would like to see it, try to get it at pancard if possible..

All the best.

Will post it later on. I have not made the plans yet. Further, I don't want to bias your design.

Got hold of some tennis racquet gutting, not kevlar but still doing the job pretty well.
Attached is a picture of my plastic tube joint for wing tip. Can you guys suggest a better way of dong this ???

By design itself this carbon bow type frame may not be a great idea. Preferably, instead of tension'ing the carbon tunes so much at the tips you could bend them lesser and have balsa or foam blocks at the wing tips. The CF tube ends could be housed inside these blocks (at a lesser angle and the blocks themselves could be shaped to the ellipse you want.

In any case don't you first need build the wing frame with ribs and spars and then attach the LE and TE tubes??

Thanks for the help tg.
Inserting another smaller diameter plastic tube in the outer tube has solved the problem for now. If this doesn't work i might go the balsa block way.
The LE TE tubes and a string is all there is to wings, no spars or ribs whatsoever  :P

Wow! I was assuming this to be a regular built up wing. Forget what I said in earlier comment. I've got a similar (40 inch wing span) glider made of rip-stop nylon and CF rod but much smaller than yours. It flies best in almost nil wind conditions and is free flight. And like yours the wing dihedral is formed by strings that pull the wing halves upwards and connect to a pod attached to a CF fuse.

What do you plan to cover the wings with.

I am planning to use that silver car cover fabric commonly found nowadays, however initial tests will be with newspaper covered with packing tape. Can you post a few pics of your free flight glider.

Sure, will post tomorrow.

Here the pics of my glider, reinforced with CF rods and tubes. The LE and TE are cracked owing to transport mishaps and needs to be fixed. I'll post the assembled glider later this week.

The pics shown are (1), tail, (2) fuse with wing mount and tail fin, (3) close up of wing mount, (4) wing. The wing is mounted on the mount and there are strings on the wing that hook to the mount forming a curvy wing. The nose of the fuse is clad in rubber and can be opened to position an iron ball for balance.

Thanks for posting the pics tg. Thats a very nice design! The wing mount is giving me some new ideas already :)

The wing mount is shaped to an air foil but the airfoil of the wing is flat otherwise. Same for the tail. Will post a few more pics.

More pics. (1) tail with the slot for the elevator, (2) close up of the nose with rubber shoe (3) reverse of the wing, the spars are CF rods (2mm) that are attached to the LE and TE rods.

Actually, this is a glider-kite that I had purchased long back for ~$10 but is pretty good if you have a slope to fly it from and don't mind hiking up and down after each throw. :giggle:

some progress finally..
Replaced the carbon fiber tail boom with PVC tube, little heavier but with much less flex.
Installed most of the electronics.

Added a coro tail for test flights. This will be later replaced by a CF and fabric arangment similar to the wing.

may i suggest something ?

yes please!

Re=ρVL/μ. 'Re' is called the Reynolds number, a dimensionless ratio of Inertial Forces to viscous forces in a fluid reaction. ρ is air density, V is the fluid velocity L is the length in question and μ is the dynamic viscosity, forget rest of the equation and look at only 'length (L)', when you apply it mathematically at a zero chord (L= zero) Re is zero. At zero Re, stall speed is zero and so is the stall α, which means the tip and area near is forever in stalled state,  Re increases as the chord increases, and so does the stall speed and the stall α, which also increases slowly. In fact last 20% of the double bow wing tip will not produce any usable lift. on the contrary it will produce more drag and add to the weight. But I understand you want it to be man-portable and want to keep the design simple isn't? there are two options
(a) have the last 10% chord bending backwards to form a finite chord when you tighten it (you can break it and and put a mechanical stop to prevent from bending further, something like the retract)
(b) you can rig it in a manner that when you taut it the tips crank to form a kind of Tip Fence (Like the tip of a easy star). both of which will highly enhance your lift, directional stability, dynamic lateral stability and reduce the span.

My personal opinion, take it with a pinch of salt, you are more wise than me as you are producing it hands on.  ;D all the best  :thumbsup:

Thanks for the tip augustinev.
Now that i see it, i also feel that a huge chunk of the span is getting wasted. Still i cant figure out a simple way of fixing this.
The plane weighs 910 grams right now with all the electronics and a 2200 mAh battery, the fabric will add extra 60 grams. So i think it is safe for a test flight. However i'll need all the lift i can get out of that span as i'll be adding a 150 grams camera to it.
May be i can attach an extra aluminium tube angle to both tips. Got to put some thought into it... 8-)

Trapeze planform with a taper ratio of 0.4 to 0.5 can be looked at, shouldn't be too hard. ran some simulations on your model, math model with zero tip chord failed. I put some arbitrary small tip chord, results are different every time, my experience, you will have hard time balancing her laterally, she WILL wing drop easily, be careful during steep turns and landing, :thumbsup:

Yes, thats what i am thinking about.
And thanks for running the sim, now i know what to look out for :)

Wings made from newspaper covered with packing tape.
ps: I need two servo extensions for this bird, can anyone(pancard club flyers) bring two extension tomorrow so that we can test this bird.

Looks cool..  :thumbsup: :thumbsup: Let us know how she flew.

hi, great looking model, you did not indicate about the flex earlier, if your are going to fly with this amount of flex should not be an issue, spanwise flow will be minimized. will be highly stable and easy to fly, initially don't do steep turns and wing over , take it from there, all the best, eager to know the outcome. :thumbsup:

Have you actually flown this - ?

It will tip stall very easily

Saikat, my suspicion too, see rep #34 and #36

Yes - read .... and concur -

It fact I see now that said model does not have ailerons - will
be unflyable unless you have the CG very forward.

Control will be marginal at best

good idea, why don't you try increasing the boom length and reduce the elevator and rudder size (Keeping the elev and rud power same by increasing the moment arm)

conversely, what the heck, go ahead prove us wrong. :thumbsup:

Thanks for the comments guys and sorry for the late response!
I'm absolutely not worried about failure right now, I'll be happy to get back from the field even with half the electronics :) it's an experiment right!
About the boom, thats the longest I can go right now without making it tail heavy.

Finally got a chance to maiden it today. And guess what "It flies" :)
The plane was tail heavy, so had to tape a wrench to the nose :o to get the CG right.
The flight was easy, not any noticeable bad characteristic except for the nose tipping up which can be easily corrected by adjusting thrust angle. I am sure this thing can haul a brick if it has to ;D
Now I am planning to build a new fuse for it. Anyways check out the video.
http://www.youtube.com/watch?v=BDpHSC7ehbI
Edit: initially the plane was tail heavy after taping the wrench it became nose heavy.

It was great to see this baby fly..Great work Amit..

 :goodjob:

Nice one -

learnt something today

Thanks Atul, I'm glad you guys were there for the much needed motivation ;)
Thanks saikat.

Excellent flight and nice to see home made plane fly so well.

SunLikeStar

gr8 vid, actually, feeling a part of it,our discussions on KFm2 , to tip stall to everything, actually the flex did it all, full credit to the flex and you , gr8, compliments, nose hvy will get sorted with fuse, i guess :thumbsup:

there is still a little tendency to wing drop (Just before the landing), also check your static lateral balance, i think she is port heavy. see if you can round the wing tip somehow, importantly keep the flex, don't loose it. gr8,

Thanks for the compliments tg.
@Augustinev, All discussions were worth it, thanks for all your help man! Yep the new fuse is for correcting the CG part and for a new foldable tail.
..the wing drop seems to be because of over correcting the heavy nose by elevator. But i am planning to do the round tip thing soon, that should resolve this problem.

Great flight... and congrats on the new model.. keep experimenting.. {:)} {:)} :thumbsup: :thumbsup:

Thanks izmile :)

New tail for the bird  :P

SLS

Which is this servo, Multiplex ? or is it the HK 9 gm servo with a red tape   :giggle:

a few points for consideration

1. In this servo arrangement the push throw will be less than the pull throw, you will have to correct for it in the Radio.
2. when the servo is pushing the control surface the wire may flex, seems to be a cycle spoke, so should hold.
3. after a couple of flights it is worthwhile checking the horn, especially the base of it.
4. Where is the Bevel cut ? is it below, if not cut it it, will decrease control friction (I am sure you have already done it, just checking).

Like i said gr8 build :thumbsup:

 :thanks:
It good old HK 9 gm  ;D
1. Did not pay much attention to that, will have to check it pre flight.
2. Yes its cycle spoke, no flexing at all.
3. Will try to secure it with small screws  8-)
4. The bevel cut is in place :thumbsup:

one other thing, both the servos are on one side it might yaw right and pitch down and right cater for that

 ??? servos are on either side of the boom.

Starborad side of the fin and the top right of the tailplane ???, that section i am talking about of the empennage

ohh.. you were talking about how the V-tail would behave. I thought I've done something wrong.

Wait a minute... you did not notice it was a V- tail !! did you  :giggle:

A video is worth 10K words :)
http://www.youtube.com/watch?v=lHl7J6tMfd0

no !! silly me  :banghead: thought the other tailplane is not in view lol. sorry

New motor mount and 10x6 folding prop.

will u be flying this plane this weekend? plz fly it on sunday,i will b there!

I'll be flying it tomorrow. Dont worry, I'll bring it on sunday also.. if it survives   :thumbsup: