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Homemade RC Glider

Old 07-23-2019, 09:04 PM
  #51  
quorneng
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aaindthu
You can run the cables through a guide tube but the servo and control horn should still be in the same plane or fairly close to it.
What is important is that when the servo is deflected the tension in the cables should tend to slacken rather than increase..
The trick with pull/pull cables is not to over tension them in the first place as apart from overloading bearings and hinges it will put an additional constant load onto the fuselage.
If you can keep the cables running inside or close to the surface of the fuselage any bending should not be an issue on a plane that is rigid enough to fly!
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Old 08-02-2019, 01:17 AM
  #52  
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the progress so far...

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I did not use the pull pull cable technique because... after 5 crashes in a row, I was hesitant to do
anything that's either complicated or that which is new to me. So I went with what i know - the regular push rods.

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Old 08-02-2019, 02:30 PM
  #53  
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That looks very neat.
I do wonder if you will ever actually need flaps other that to play with to see what happens.

ff I was doing it i would have kept it simple and used just 3 servos (ailerons and elevator) instead of six and put the elevator servo right at the back with a short direct link as you have done for the ailerons.
Such a linkage is significantly more efficient and gives a higher 'precision' than a snake and guess which control needs the greatest precision for accurate flight - the elevator!

As long as you have the CofG more or less in the right place it should fly and I suspect quite well too.
Do let us all know how you get on.
.
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Old 08-02-2019, 02:37 PM
  #54  
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That looks very neat although I doubt you will really need the flaps.

If I was doing it I would have used just 3 servo (ailerons and elevator) rather than 6 and placed the elevator servo right at the back with a short link as you have done for the ailerons.
Such a linkage is both more efficient and gives a greater 'precision' of movement and guess which surface requires the greatest precision for accurate flight - the elevator.

If you get the CofG something like in the right place it should fly and I suspect quite well too.
Do let us all know how you get on.
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Old 08-17-2019, 02:29 PM
  #55  
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My glider is ready to fly.
weighs 907 grams, and C.G is around 20% from L.E.
The 2m Wings are strong enough as seen from the wing load test
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I thought flaps would be useful to land the glider when slope soaring.
I've cut the 11 inch folding prop into a little less than 9 inch one. I've cut it myself with hand, and have no vibration kind of problem.
will fly it soon.

Last edited by aaindthu; 08-17-2019 at 02:52 PM.
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Old 08-17-2019, 03:56 PM
  #56  
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Good load test!
What made you decide to cut down the prop? At 11 inch was it drawing to many amps for the speed controller?
A 11 inch prop cut down to 9 is not quite as efficient as a true 9 if they have the same pitch.
Also a bigger prop run at lower power is significantly better at converting each watt into thrust. Unless you have to go fast big slow props are better.

Last edited by quorneng; 08-19-2019 at 12:05 AM.
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Old 08-17-2019, 06:03 PM
  #57  
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Originally Posted by quorneng View Post
Good load test!
At 11 inch was it drawing to many amps for the speed controller?
.
11 inch prop was creating torque problems for the motor. It was a learning experience for me from my previous glider.
that 11 inch prop made my previous glider to spin out of the sky. so, i cut it down to a 9 inch for my new design.
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Old 08-25-2019, 01:04 PM
  #58  
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The glider flew alright. But, it was too fast/heavy to be a glider and the wind was only making it worse. And I am a newbie.


I think the airfoil is to blame for its speed. It is a semi symmetric one. Throughout the maiden flight including the glide test, the flaps were down, but still it was flying so fast. It doesn't maintain altitude and likes to dive as seen from the video.

Sooo, I am going to build another wing, but a thicker one with a more slower and lift producing shape of an airfoil. I won"t be adding flaps this time.

I am looking forward to hear the opinions from the experts that you all are!! Thank you.

Last edited by aaindthu; 08-25-2019 at 01:21 PM.
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Old 08-25-2019, 02:18 PM
  #59  
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Well done!
To me that maiden flight looked fine given it is a home design! Was there much damage?
There are many things you have to get right for a plane to fly well, including the skill of the pilot.
Of course without knowing what control inputs you were making it is difficult to be exactly sure.

My advice is to make any necessary repairs and move the balance point (CofG) forward by say 6 mm (1/4") as it looked to me like it was flying a bit tail heavy, hence the tendency to pitch up a bit on the glide and a lot more when under power.
Remember a nose heavy plane flies well enough but a tail heavy plane flies just once!
Do not use any flaps until you have it flying really well. When used they will effect the way it flies, likely pitch up, leading to a stall and a wing drop into a dive so only test them first time when you have lots of height!
Finally don't worry about it appearing to fly fast. At this stage all you want is it to fly in a controllable manner. It probably will be able to fly quite a bit slower but finding out is for later.
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Old 08-25-2019, 02:47 PM
  #60  
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Originally Posted by quorneng View Post
Well done!
To me that maiden flight looked fine given it is a home design! Was there much damage?
Quorneng,

Thank you.
Yes, the wing just snapped in two and the slender tail section broke separating the tailplane from the rest of the fuse.

I have changed my plans now, after watching the video again and again. I think I know what is wrong. I think a mere elevator up trim would have prevented this crash.
The glide angle of this glider is not straight with all the control surfaces at neutral position. It tends to glide with its nose pitching down. You can see that during the glide test, just after I launched it (with my right hand), it was pitching down, until I got my hand back on the radio and pulled the elevator up. Only after that, the glider pitches up and there was quite a lot of head wind that might have made it appear as if the glider is tail heavy. But it's definitely not, I am certain.
During the actual flight, again I think the headwind makes it look like its tail heavy.

So, I am just going to give it another try. with some up elevator, after gluing the broken pieces back.
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Old 08-25-2019, 10:59 PM
  #61  
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Fix it and continue to fly it.

Work on moving that CG around.
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Old 08-26-2019, 03:48 PM
  #62  
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Originally Posted by aaindthu View Post
Quorneng,

Thank you.
Yes, the wing just snapped in two and the slender tail section broke separating the tailplane from the rest of the fuse.

I have changed my plans now, after watching the video again and again. I think I know what is wrong. I think a mere elevator up trim would have prevented this crash.
The glide angle of this glider is not straight with all the control surfaces at neutral position. It tends to glide with its nose pitching down. You can see that during the glide test, just after I launched it (with my right hand), it was pitching down, until I got my hand back on the radio and pulled the elevator up. Only after that, the glider pitches up and there was quite a lot of head wind that might have made it appear as if the glider is tail heavy. But it's definitely not, I am certain.
During the actual flight, again I think the headwind makes it look like its tail heavy.

So, I am just going to give it another try. with some up elevator, after gluing the broken pieces back.
I'd listen to Quorneng and get the C/G right before trying to fly again.

The video shows a series of stalls and recovery, more up-elevator will only make these worse if the C/G isn't correct. Leave the elevator trim at neutral, you can always add trim up or down when in the air.

You'll also need a bit more speed off your hand launch. That will take care of the downward initial flight. Your launch otherwise looks fine with the glider level but see if you can get more thrust and maybe a bit more push. Ideally, your glider will fly on its own out of your hand but I don't think you have enough motor or prop for that.

Keep us posted. Your design has a lot of potential.
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Old 08-26-2019, 04:24 PM
  #63  
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AEAJR, Abuelo,

Thank you for your kind words.

I am fixing this glider... But sincerely, I don't think CG is a problem. I feel that the pitching up and stall is due to the combination of these three factors:-
1. Strong head wind.
2. I was pulling back the elevator stick to counter the downward glide angle.
3. Flaps were deployed all the time.

But I am definitely going to check the CG after fixing this glider and if possible I will show you a picture of this glider balancing itself at the point of CG.

Thanks again, will keep you posted.

Aaindthu

Last edited by aaindthu; 08-26-2019 at 04:59 PM.
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Old 08-28-2019, 07:40 PM
  #64  
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Bear in mind that how a plane flies is not only effected by the CofG but also the angle of incidence of the tail plane relative to the wing. It is normally set at a small negative angle to the true airflow to the wing. Too negative and the plane flies as if the elevator is permanently a bit up and needs a forward CofG to compensate. Too little negative will require the CofG to be moved back but this can then lead to control and stability issues.
Setting up a home design to fly is not easy, setting it up to fly well and efficiently, as might be required for a glider, is rather more difficult.
Keep trying. It all counts as experience.
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Old 09-02-2019, 01:27 PM
  #65  
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I couldn't fly this weekend because of the rains.

This is what I did to my glider - I gave the wing some positive angle of incidence. I noticed from the crash video that the wing had a negative angle of incidence. So I glued some foam in between the wing and fuselage area and now the glider has some positive angle.

And one other modification to make it fly better is to use a smaller battery (3s 1000mAh) instead of 2200 mAh.

Now, it has a better glide angle. So Now, it should fly on its own out of my hand - as Abuelo put it.
it weighs 895 grams with the smaller battery. And the CG must be at the right-ish place, because otherwise it wouldn't have glided nicely in the first place.
And I have also taped 2 numbers of 5mm thick nuts and bolts to the battery to keep the CG around the safe zone.

I was so eager to fly it, but it was raining. Waiting for the weekend now. .....
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Old 09-25-2019, 05:23 AM
  #66  
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Any progress?
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Old 09-25-2019, 09:00 AM
  #67  
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Originally Posted by Abuelo View Post
Any progress?
Abuelo,

That glider crashed again (sigh). I think it was just too heavy. So I'm building another glider.

But, I'm very confident about this one. It is very light weight at 700 grams and controlled by rudder and elevator only. Flat bottom airfoil with 2m span, it has dihedral
and I placed the wing back close to middle of the fuselage to add nose weight for the small 1000 mah battery.

This should fly very nice and gentle. I just hope it doesn't rain this weekend. So sorry for keeping silent

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Old 09-25-2019, 01:02 PM
  #68  
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aaindthu
Oh! Dear, bad luck.
Any pictures of the new one?
I presume it has a motor.
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Old 09-25-2019, 04:20 PM
  #69  
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Guess I will have to build a more sophisticated glider for later....
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Old 09-25-2019, 08:07 PM
  #70  
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Originally Posted by aaindthu View Post
Attachment 187647
Attachment 187648

Guess I will have to build a more sophisticated glider for later....
Looks good.

Where is the center for gravity?
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Old 09-26-2019, 01:25 AM
  #71  
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Looks like a winner this time.
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Old 09-26-2019, 06:16 AM
  #72  
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Originally Posted by Don Sims View Post
Looks like a winner this time.
Don Sims,

Thank you!
I hope I do it right this time... atleast.

Aaindthu
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Old 09-26-2019, 06:22 AM
  #73  
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Originally Posted by Abuelo View Post
Looks good.

Where is the center for gravity?
Abuelo,

Thanks.
So, I know I messed up the CoG before. So I made the nose longer to get the CG right.

Here is a makeshift CoG calculator - just poked two screw drivers into blocks of foam and made the glider to sit on them, straight and level.
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Old 09-26-2019, 07:09 AM
  #74  
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Originally Posted by quorneng View Post
aaindthu
Oh! Dear, bad luck.
Any pictures of the new one?
I presume it has a motor.
Quorneng,

Yes, bad luck.
I should have never used 2200 mah batteries for this. Otherwise, the previous planes would have flown just fine.
And yes, this new glider has a motor. It is basically the same "setup" as the previous one.
Only this has 1000mah battery which is less than half the weight of the 2200 mah battery, and hence a longer nose to keep the CG right.
Here's the picture:-
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Thankyou
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Old 09-26-2019, 10:09 AM
  #75  
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The important bit about the position of the CofG is how far back from the leading edge it is usually expressed as a % of the width of the wing.
25% is considered a safe point. It looks like yours is currently a bit far forward.
If the CofG is less than 20% it will have to fly much faster than it needs to so will it will feel like it is trying to dive into the ground.
However a bit forward of 'ideal' is much safer than too far back. The saying is "Forward CofG may fly poorly, a rearward CofG will fly once!"

Just out of interest is the battery in the cockpit or under the wing?
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