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Homemade RC Glider

Old 06-11-2019, 01:08 PM
  #26  
aaindthu
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Yes, Mr. Jools, you are right. These wings are definitely not strong enough.
So, I am going to glue 3mm thick balsa strip on top of each wing. That should make it strong enough.
Thanks,
Aaindthu

Last edited by aaindthu; 06-11-2019 at 01:57 PM.
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Old 06-11-2019, 01:32 PM
  #27  
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Originally Posted by quorneng View Post
Just a crude test but with every thing, including the battery, in place does the wing feel strong enough to allow it to be lifted just by its wing tips? If it can the wing should be adequately strong enough to do a loop without breaking.
So I did the test with two batteries, esc and motor in place. Because the glider is not finished yet and it is likely to end up heavier when finished I used two batteries for this test(one 3s/2200mah, and 3s/1000 mah,) even though I will be using only one for flying.

The wings flex, but not too much. Looks okay to me.

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I have glued 3 mm thick balsa strips along each wing, but only on top of the wing.
I will do the same on the bottom wing as well. I don't feel any significant increase of weight due to the balsa strips.

Last edited by aaindthu; 06-11-2019 at 01:58 PM.
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Old 06-16-2019, 01:58 PM
  #28  
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tried to make a clear plastic canopy out of coke bottle, but didn't work.
So, I'm making a foam canopy. I'll put some paper mache over the canopy and around the edges and cover it with black tape, that should look good.

I've also elongated the nose to get the CG right.
Almost complete.
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Old 06-17-2019, 12:05 AM
  #29  
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aaindthu
Your wing load test looks quite adequate to me and should allow gentle aerobatics.
There is nothing wrong with "adjusting" the length of the fuselage, within reason, to get a suitable CofG position.
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Old 06-23-2019, 12:18 PM
  #30  
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Phew !! So this is what the glider looks like now.
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I had to shorten the nose back to the original length. The elongated nose messed up the proportions of the glider and it looked very odd, like half glider and half private jet

To bring the CG forward, I reduced the weight in the tail section by narrowing the fuselage and by reducing the distance between the tail-plane and the wings itself.
But still, the CG is somewhere around 40-50 percent of the chord.
I have no choice but to add ballast, just a little bit.
I have also increased the wingspan by 30 centimeters on each side of the wing, just have to glue the balsa strips in the same fashion and
conduct that load test again.

Also, the flaperons are no longer full length and it should reduce the roll sensitivity and improve the stall characteristics when deploying flaps.

Last edited by aaindthu; 06-23-2019 at 12:39 PM.
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Old 06-24-2019, 12:26 AM
  #31  
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aaingthu
That looks quite impressive.
Adding wing span and reducing the fuselage tail length at the same time can lead to handling issues. How significant will rather depend on how much 'reserve' stability there was in the first place.

Careful doing a load test. As the wing root is unchanged the ultimate strength of the wing will be reduced directly in proportion to the increase in span.

Whilst the stall characteristics are important so is how it recovers from a stall, particularly when the plane is close to the ground!
The safest combination is normally outboard ailerons and separate inboard flaps. This layout means the inboard wing is likely to stall first and the ailerons still remain effective.
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Old 06-25-2019, 01:15 AM
  #32  
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Yes, the wings flexed a lot.. even the aluminium rods were bending. So, I glued one more aluminium rod in between the already glued 2 rods. Now, there are three aluminium rods.
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Load test :-

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Last edited by aaindthu; 06-25-2019 at 04:33 AM.
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Old 06-30-2019, 07:35 AM
  #33  
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The glider is ready for maiden flight.
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Here are the specs:-

Wingspan ------------------------ 2500 mm
A.U.W ----------------------------- 1240 grams (or) 43.74 oz (yes it's heavy)
Wing loading -------------------- 0.255 gram/sq.cm (or) 8.378 oz/sq.ft.

And I got the CG right without any ballast by making a "special" room for the battery which is very forward into the fuse.
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And yes, 1.24 kg is heavy. But, compare it's wing loading with that of a proven design, like the E-flite, Mystique.
Wing loading of Mystique ---> 10.9 oz/sq. ft https://www.horizonhobby.com/mystique-29m-arf-efl4905
So, the wing loading of our glider is less and I could really see the difference when I did the "glide test".
My glider (with a slight camber) glides really nice and slow. I could even use the word "floater" to describe the way it glided.

So, I am all set to make the maiden flight. (next weekend )
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Old 07-08-2019, 04:50 AM
  #34  
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I launched it. crashed it. fixed it. launched it again. crashed it again. Now I am fixing it again. LOL.

I gave it too much angle of incidence. So much that I first thought that it was tail heavy. Now I am fixing it again.

I will launch it again. Hopefully this cycle ends there.
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Old 07-08-2019, 11:00 PM
  #35  
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You certainly are determined mate. Good luck. Keep the spirits up.
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Old 07-09-2019, 12:54 AM
  #36  
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aaindthu
Are you sure what is happening is just down to the angle of incidence?
Could also be related to the position of the centre of gravity.
Or even some unwanted flexibility some where.

Perhaps you are discovering some of the issues in building your own design.
The important bit is learn what is 'poor' so next time it can be 'better'.
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Old 07-09-2019, 05:39 PM
  #37  
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Originally Posted by quorneng View Post
aaindthu
Are you sure what is happening is just down to the angle of incidence?
Could also be related to the position of the centre of gravity.
Quorneng,

Yes, I am certain.
I did not measure the exact angle of incidence though. But, I could easily see that angle with a simple method, by standing at a distance from the glider with a ruler in hand so that the glider appears smaller in size and within the length of the ruler. I aligned one end of the ruler with the chord line of Horizontal stabilizer and saw the other end of the ruler intersecting the chord line of the wing. The angle was obviously too much.

But I fixed it again, just waiting for the weekend.

Last edited by aaindthu; 07-09-2019 at 06:01 PM.
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Old 07-10-2019, 11:38 AM
  #38  
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aaindthu
You may well be right.

Within certain limits the incidence of the wing to the airflow determines the speed at which the wing generates sufficient lift to carry the weight of the plane.
However the centre of lift generated by the wing changes with its incidence so the position of the CofG has to be changed to maintain a constant flight speed.
So within limits either too much incidence and/or a CofG too far back will generate exactly the same flight path as you describe.

Just be careful you don't remove too much of the incidence between the wing and tail or it will not fly at all!
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Old 07-15-2019, 04:47 AM
  #39  
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The glider glides very nicely. But the moment I give some throttle, it spins out of the sky and falls. I think there is an issue with thrust line.

But I am done doing repairs on this model. I'd rather build a new one. This time, a high wing, conventional tail (no T-tail), and a one-piece wing that will be attached with screws.
Conventional in-board flaps and outboard ailerons.

I will post again with my new glider.
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Old 07-15-2019, 10:45 AM
  #40  
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aaindthu
If it becomes uncontrollable as soon as thrust is applied I would suspect wing flexing coupled with motor torque is the problem. To do this just because of a thrust line issue it would have to be a long way out.

A one piece wing sounds a good idea. I would also suggest you keep the wing span to wing chord (its aspect ratio) to about 6:1.
Broader wings may be a bit less efficient but are much less prone to flexing issues and are considerably stronger for their weight.

This may not look much like a high performance glider, high wing and a pusher, but it is nevertheless pretty efficient.
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Its relatively broad wing is strong and light.
It glides nicely and thermals well too (I don't have access to any slopes!)
It also carries a pretty big battery so can stay up under power for a longer than I ever want to fly!
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Old 07-15-2019, 11:26 AM
  #41  
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Quorneng,

As you have mentioned, the problem could be motor torque because I remember now, I noticed that the prop spinner was heavy for my 2212 motor. It's a 11 inch prop.
So, I will give this glider one last shot with a smaller prop. I almost hacked this glider to rip off the electronics from it. Thank you for saving this glider.
I am also working on a R/C Trainer 2.0. (with better foam than the previous one and definitely better looking), will post it too, when finished.

Thanks,
Aaindthu

Last edited by aaindthu; 07-15-2019 at 07:04 PM.
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Old Yesterday, 01:05 PM
  #42  
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aaindthu
You will have to decide if your glider is worth saving.
What is the kV of your 2212 motor?
The lowest kV version I can find is 1000kV and an 11 inch (is it 11x6?) prop is rather too big for even that one . It is likely over loading the motor and of course will also create more torque.
A 10x4.7 is recommended..
The weight of the folding prop is not necessarily a problem if you need the weight up front anyway although unless well balanced its weight can cause motor vibration issues.

If you can manage the reduction in weight I would go for a fixed 10x4.7 just to get it to fly. It you close the throttle before it lands the chances are it wont break.
This one, with a prop adaptor, weighs just 16.3 g (0.6 oz),
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If there is a question about the plane's stability, launch without power and then add it gradually.seeing what happens before adding any more. If it glides as well as you say it should be able to maintain height on just part throttle.

Last edited by quorneng; Yesterday at 10:52 PM.
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Old Yesterday, 10:35 PM
  #43  
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Originally Posted by aaindthu View Post
Quorneng,

As you have mentioned, the problem could be motor torque because I remember now, I noticed that the prop spinner was heavy for my 2212 motor. It's a 11 inch prop.
So, I will give this glider one last shot with a smaller prop. I almost hacked this glider to rip off the electronics from it. Thank you for saving this glider.
I am also working on a R/C Trainer 2.0. (with better foam than the previous one and definitely better looking), will post it too, when finished.

Thanks,
Aaindthu
Hi You dont need a 11" prop for a 2 meter glider, thats way way to big, when i was flying 2 meter gliders, I would use a COX 049 engine with a 6x4 prop to get the glider in the air, when the fuel ran out, I would just catch thermals and fly for quite a while, I had the engine on a power pod strapped to the top of the wing, it worked great, that was my Rc Trainer, Also make the rudder wider, gliders need a big rudder as they fly slow, use a 7x6 prop on your glider, that will be more than enough, Take care and have fun, Chellie

since you like to build, here are a few of my Plans
https://www.wattflyer.com/forums/showthread.php?t=55444
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