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Homemade RC Glider

Old 09-26-2019, 11:21 AM
  #76  
aaindthu
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Originally Posted by quorneng View Post
Just out of interest is the battery in the cockpit or under the wing?
The battery weighs around 80 grams which is very light compared to bigger batteries. So I had to place it as forward as possible, to counter the weight of the servos in the tail.
So I put the battery inside the canopy which is quite forward from the wing LE.

I was thinking that a little nose heavy planes might fly better in windy conditions, especially when the plane is light in weight. My glider weighs 740 grams now and I thought
740 grams is very light for a 2m wingspan glider and therefore, I made it a little nose heavy intentionally. My plan is to trim the elevator to counter the nose heaviness, if any.
Hope this works.
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Old 09-28-2019, 12:04 PM
  #77  
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Hello,

That yellow glider flew but it does not turn at all, even with that big rudder.

What I think was wrong:- I built this glider initially for the 2200 mah battery. Then I found out it was too heavy and wanted to use 1000 mah battery which was lighter. But I had to move the wings backwards to get the CG right. This reduced the distance between the rudder and the wings. Therefore, the rudder no longer has enough "leverage" to turn the wing and roll it too.

I even cut some of the dihedral part of the wings and made it poly-dihedral, to see if that works. But that did not work.

But, now, now I know the electrical setup that I'm going to use beforehand. So I am going to build another glider.
I am going to build this one more beautiful than any of the glider above and this will fly.

I cannot believe this. I used to build a lot of big chuck gliders when I was younger and I did not even have internet at that time. I built it all by myself and I always thought that it would be easy to build an rc plane if only I had what I have now, the electronics.

But I am going to try again. This time, a beautiful aerobatic glider with aileron and elevator control only.

I am so sorry to keep dragging this build log without an end to it. I am willing to quit posting if this violates the community policies of the forum in any way. But i won't quit building though

Last edited by aaindthu; 09-28-2019 at 12:29 PM.
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Old 09-28-2019, 04:13 PM
  #78  
quorneng
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aaindthu
Most definitely keep building & posting!
It is worth remembering that long wing span gliders do not respond to rudder only commands particularly fast, there is simply too much inertia, particularly if you have an electric motor on the end of a long nose!
Even when the rudder has made the glider yaw your relatively slim fuselage has limited side area so the glider will tend to skid sideways rather than turn. The yawing motion and wing dihedral will make the glider bank but the relative heavy long span wings will only do so slowly.
You can see that much of your current design has conspired to make the glider slow to respond to rudder commands. I can assure you that full size high performance gliders don't turn well on a rudder only input either!

Ailerons are a much better solution if you intend to keep 'long' wings as even quite small ailerons placed out towards the wing tip will provide a positive bank action. With a slim fuselage 'bank' is a primary requirement to initiate a turn.
However using ailerons is not all 'sweetness and light' as particularly on long wings they can cause a yaw in the opposite way that you want to turn. This effect get more and more pronounced the more aileron you apply, however it is only a transient effect as once you have set the required bank and centred the ailerons the natural correcting effect of the fin will straighten the yaw and the glider will continue to turn normally. Remember also if you are turning with any sort of bank angle you will have to use some opposite aileron to get the wings back level again to end the turn.
So 'aileron only' turns are much more positive than 'rudder only' but their very effectiveness and secondary effects can cause problems (a crash!) if used excessively when flying low and slow - typically the final turn before coming into land in windy conditions!

In your case removing the weight of the rudder servo in the tail is probably wise to reduce the length of the nose but do use a generous fin to provide good natural yaw correction.
It would also pay to move the battery as close to the motor as possible to also reduce the nose length. In fact keep construction of the whole rear end as light as possible so it can be as long as possible even if it that means it becomes a bit 'delicate'. The better a plane flies the better are the landings.

I look forward to seeing how it turns out.



.
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Old 09-29-2019, 12:02 AM
  #79  
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Keep posting please. Your perseverance and how you work through problems is admirable. We enjoy watching you learn and grow.
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Old 10-02-2019, 07:43 AM
  #80  
aaindthu
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Thank you

Trying to build my next glider based on Swift S1 aerobatic glider......

I've done the basic fuselage :-
Click image for larger version

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Next, I am going to hollow out the fuselage between the wings and the tailplane without weakening the structure and then wings (2 meter span).
This glider will be powered by 3s 1000 mah battery (weighs 75 grams) and I am changing the motor and propeller as well.
I am going to use a 6 inch folding prop and a 2024 micro brushless motor (weighs only 20 grams).

Things that went wrong from the first glider :-
My first glider had too much angle of incidence and too much torque from the motor due to big propeller size...
Second glider had negative angle of incidence of the wing and was a little tail heavy...
Third glider did not turn ...
The first two gliders were also little bit on the heavier side....
So, I am just being careful this time while building....

Last edited by aaindthu; 10-02-2019 at 08:45 AM.
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Old 10-02-2019, 12:03 PM
  #81  
quorneng
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aaindthu
That fuselage look very nice.
Careful how you hollow out the rear fuselage. The foam you are using looks fairly weak so it will be a balance between strength and weight. Any weight saved close to the tail is far more useful!
Is that the final size of the tail plane and elevator? It looks rather narrow and of limited area.
Whilst the weight penalty of a high aspect ratio wing may be acceptable and necessary for 'performance' the same weight penalty in a tail plane is more serious.
It can be structurally more efficient to use a broader shorter span for a given area. As RC models have to be flown in a much smaller space and make tighter manoeuvres than full size it is normal to give them proportionally bigger tail and control surfaces.
Models are less aerodynamically efficient than full size so the penalty for over size surfaces is proportionally less significant. Having good control response and stability tends to increase the life of the model.

This 3 view is of a full size wooden glider that had a high performance at the time.
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Notice that compared to the high aspect ratio wing the tail plane is relatively short and stubby. Note also the very generous size fin and rudder.


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Old 10-02-2019, 04:09 PM
  #82  
aaindthu
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Quorneng,

I am using this picture of the Swift glider for reference :-
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Even this glider has a short tail plane compared to the wings.

I have a print-out of that picture and I use it make the dimensions proportional for a 2 meter span glider. Accordingly, the size of the tailplane.
I think the tailplane size will look reasonable and proportional once I make the wings.

Here is the planform view of the stabilizer of my glider:-
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Old 10-02-2019, 11:10 PM
  #83  
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aaindthu
Fair enough.
Just make sure the tail plane and fin are strong and rigid enough to support their relatively big control surfaces.
Remember the full size has the benefit of being an epoxy resin glass fibre structure.
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Old 10-13-2019, 01:05 AM
  #84  
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Sorry for the delay - just ran out of foam.

The wings are done, just have to install the servos.
The wing is reinforced with 3mm balsa strip glued in the form of an inverted 'T-beam' along the 2m span wing.
Click image for larger version

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This reinforcement made the wing super-strong, even though the vertical and the horizontal sections of the 'T beam' are not in contact. They're glued along the top and bottom of the wings separately.
Click image for larger version

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The epoxy resin container that I used for load-test weighs 678 grams. I expect the total weight of the glider to be less than 600 grams.
And the wing weighs 178 grams - without servos.

Also, the glider and the tailplane looks proportional now
Click image for larger version

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Old 10-14-2019, 12:43 AM
  #85  
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aaindthu
That looks very professional.
Balsa reinforced foam can be very effective. Light and strong as you have found. Good load test!
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Old Yesterday, 05:57 AM
  #86  
aaindthu
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Originally Posted by quorneng View Post
aaindthu
That looks very professional.
Balsa reinforced foam can be very effective. Light and strong as you have found. Good load test!
Quorneng,

Thanks! I made some progress....
Installed the servos and made tape hinged ailerons.. and made a gap in the fuselage for the wings to fit.
Click image for larger version

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The weight of the plane as of now - with just the 3 servos, wing, fuselage and tailplane is 365 grams. I added the battery, the motor, the receiver, ESC etc. to the weighing scale and the weight comes to 572 grams.
I am going to use a micro motor turning a 6-inch folding prop.
And I am using the thin copper coil that can be found in the windings of electric motors for the servos, instead of cables to save weight. Will keep you posted of my progress.

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Old Yesterday, 12:38 PM
  #87  
quorneng
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aaindthu
Those ailerons look good.
I am not sure you will actually save much weight using solid on the servo as their wires are a small diameter already. Much of the weight comes from the servp connectors if you use ready made extensions.
When using solid wire the insulation 'varnish' must be carefully scraped off, not as easy as it sounds, and the joint really must be soldered otherwise you will get poor connections.
Any connections you make must be insulated unless you can positively keep the wires separated and the joint fully supported. Solid wire joints will quickly fracture if it flexes at all. Always keep a short length of flexible cable leading to the rx plug for the same reason.

Nice to see the design developing.
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