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Homemade Slope Soarer - Build log

Old 09-19-2018, 08:59 PM
  #1  
aaindthu
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Default Homemade Slope Soarer - Build log

Hi !

I am going to build a slope soarer out of HD foam. It is a rudder and elevator only design with 2m wingspan, powered by 4 x AAA size batteries.
I am going to use spring pull system for the elevator and the rudder.
Here are the basic structure of the fuselage and the wings.
For reinforcing the wings, I am going to put paper mache (again) but only at the leading and trailing edges of the wing, to reduce weight.
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I also noticed that similar RES gliders have a large rudder. So I am going to do the same in my glider and give it a big size rudder for better maneuvering.

Last edited by aaindthu; 09-27-2018 at 07:41 AM.
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Old 09-20-2018, 01:12 AM
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I am not sure that you realize just how much pressure goes on the wing of a HLG when you are launching it. It has to be VERY strong or it will just fold up. Ask me how I know.
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Old 09-20-2018, 05:39 AM
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Originally Posted by Panther View Post
I am not sure that you realize just how much pressure goes on the wing of a HLG when you are launching it. It has to be VERY strong or it will just fold up. Ask me how I know.
I have seen from youtube videos that many gliders are launched using bungee launching system or winch system. And I know I was astonished at those wings during launch that can withstand so much pressure from pull of the winch/bungee chord.

But neither of the above methods are seen here in India. I am going to simply toss it into the winds coming from the Bay of Bengal into the Marina Beach, chennai.

I have also seen gliders pulling "high G" turns. I know it requires really stiff wings.

I still believe multiple layers of paper mache can still do it. Paper mache can be very strong.

Last edited by aaindthu; 09-20-2018 at 05:55 AM.
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Old 09-20-2018, 10:29 AM
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I have to take my hat of to you ... you know how to push the boundaries ...

You proved your 'trainer' flies ... and I could not believe how packing case foam could survive those first sorties ...

Now I am all watching this latest venture !

If it was me ... I would be looking at a bamboo or white wood spar set into the wing ..

Nigel
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Old 09-20-2018, 01:31 PM
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Originally Posted by solentlife View Post
I have to take my hat of to you ... you know how to push the boundaries ...

You proved your 'trainer' flies ... and I could not believe how packing case foam could survive those first sorties ...

Now I am all watching this latest venture !

If it was me ... I would be looking at a bamboo or white wood spar set into the wing ..

Nigel
I'm really flattered. thank you !
Will keep you posted on my progress.

Aaindthu
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Old 09-20-2018, 06:51 PM
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aaindthu
Wow! You have set yourself quite a structural challenge!

Your trainer wing had a relatively thick wing with a low aspect ratio (span to chord) of 6:1?
Your glider wing has a much aspect higher ratio of at least 10:1
For a wing of the same area and section the bending forces at the wing root rise by at least the square of the aspect ratio so compared to your trainer wing the glider wing will have something like 3 times the bending force at its root (36 to 100).
The glider will likely be a bit lighter but you can see the problem. The higher the aspect ratio the more important it becomes to vary the strength, and hence its weight, along the wing to meet the loads it has to carry.

My suggestion would be to vary the amount and the position of the paper mache from root to tip, maybe something like this.
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The top and bottom paper mache panels efficiently handles the bending loads which reduce out towards the wing tip. The paper mache areas on the leading and trailing edges are more for 'protection' than adding much to the wings overall strength.

I will follow your project with interest.
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Old 09-21-2018, 02:32 AM
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Originally Posted by quorneng View Post
aaindthu
Wow! You have set yourself quite a structural challenge!

Your trainer wing had a relatively thick wing with a low aspect ratio (span to chord) of 6:1?
Your glider wing has a much aspect higher ratio of at least 10:1
For a wing of the same area and section the bending forces at the wing root rise by at least the square of the aspect ratio so compared to your trainer wing the glider wing will have something like 3 times the bending force at its root (36 to 100).
The glider will likely be a bit lighter but you can see the problem. The higher the aspect ratio the more important it becomes to vary the strength, and hence its weight, along the wing to meet the loads it has to carry.

My suggestion would be to vary the amount and the position of the paper mache from root to tip, maybe something like this.
Attachment 186972
The top and bottom paper mache panels efficiently handles the bending loads which reduce out towards the wing tip. The paper mache areas on the leading and trailing edges are more for 'protection' than adding much to the wings overall strength.

I will follow your project with interest.
Quorneng,

I know I completely understand what you mean. But this foam is different from my Trainer plane foam. This is a high density (HD) foam board and it's a bit heavier than the Trainer plane foam much stronger than the other foam.

Stronger, but still requires some reinforcement.
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Old 09-21-2018, 06:25 AM
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Thought I will work on the fuselage first.
And I have cut rooms for the battery holder (removable) and the receiver and glued the two servos in place.
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I have already tied a very strong thread to the servo horn and they run through a small piece of empty ball-point pen refill. The thread also runs through a piece of empty ball-point pen refill at the tail section of the fuselage.
The piece of ball-point pen refill acts as a guide for the thread.
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Old 09-21-2018, 11:48 AM
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aaindthu
That all looks very neat and should work well.
Love the use of the 'available' materials!
I have used ball point 'inners' myself. You can actually permanently bend them in really hot water so they can work as a guide round a corner as well.

Also be aware that a spring return control system means the servo is 'pulling' and thus drawing some current all the time so watch the battery life.
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Old 09-21-2018, 12:24 PM
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Its also worth remembering that many models in the past used braided wire as control runs. It gave not only pull but push as well.

Nigel
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Old 09-24-2018, 05:58 AM
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Now, to make the spring pull system, I took the spring from a ball point pen and bent it into the shape as shown.
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I glued empty ball point pen refills/inners along the rudder and elevator hinges as shown in pictures with epoxy glue.
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Then I simply inserted the ends of the spring into the ball point pen inner and taped the hinges. Already glued control horns and made a small hook with metal wire to tie the control line coming from the servos.
Click image for larger version

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It is working well.

Then, for the wings, I took some broom sticks and glued it the same way as I did with the Trainer plane.Name:  002 (2).JPG
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I also did a gliding test with this glider, now that it's almost complete.
It covered quite a distance and flew straight. Now the wing weighs a mere 81 grams. The wing was also stiff and straight while gliding, but I am going to put one more broom stick at the centre of the wing. And I need to make a battery hatch and that's it.
Probably we'll go to the beach next week. Can't wait
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Old 09-27-2018, 01:22 AM
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Here's how my glider finally looks like
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Flying weight is 284 grams (including 4xAAA size batteries)
I am going to fly my glider on Saturday in Marina beach, Chennai.
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Old 09-27-2018, 01:54 AM
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Hope you put a few more rubber bands on it first.
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Old 09-27-2018, 05:29 AM
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Originally Posted by Panther View Post
Hope you put a few more rubber bands on it first.
Panther,

I do not understand what you mean??
did I put too many rubber bands??
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Old 09-27-2018, 06:18 AM
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No. You will need about double what you have in the photo. Otherwise the wing will lift and it will be a disaster. If you had a heavier battery you would need more than that.
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Old 09-27-2018, 06:30 AM
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Originally Posted by Panther View Post
No. You will need about double what you have in the photo. Otherwise the wing will lift and it will be a disaster. If you had a heavier battery you would need more than that.
Now I understood what you mean.
You are right, it could be a disaster. I agree with you.

I will put two more rubber bands parallel to each other.

Thank you for pointing out
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Old 09-27-2018, 06:33 AM
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It sounds like you plan to take it slope soaring using the lift created by wind coming into a wall or dune or cliff. I have done a lot of slope soaring.

https://www.youtube.com/watch?v=pqbXbJDR6Jc
https://www.youtube.com/watch?v=Ez3GFq8xMEc

How Slope soaring works
https://www.rc-airplane-world.com/rc-slope-soaring.html

When you say Hand Launched Glider in the USA, this is what we mean:
https://www.youtube.com/watch?v=c3M38WP6Wk8
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Old 09-27-2018, 07:33 AM
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Originally Posted by AEAJR View Post
It sounds like you plan to take it slope soaring using the lift created by wind coming into a wall or dune or cliff. I have done a lot of slope soaring.

https://www.youtube.com/watch?v=pqbXbJDR6Jc
https://www.youtube.com/watch?v=Ez3GFq8xMEc

How Slope soaring works
https://www.rc-airplane-world.com/rc-slope-soaring.html

When you say Hand Launched Glider in the USA, this is what we mean:
https://www.youtube.com/watch?v=c3M38WP6Wk8
Thanks a lot for the links. Very informative.

BTW, sorry for the misleading title.

I just changed the title into "Home made Slope Soarer". Thanks
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Old 09-27-2018, 11:50 PM
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aaindthu
That looks the business.
From pictures the Chennai beach looks rather flat. Does it have any reasonable 'slopes' anywhere along it?
For continuous slope soaring you need a slope that is steeper than the gliders glide angle and is tall enough that it deflects a volume of air upwards that is big enough for the glider to able to manoeuvre within.
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Old 09-28-2018, 05:38 AM
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Quorneng,

I was wondering about the same. I thought the winds blowing parallel to the ground alone are enough to lift a glider. Is a slope must for soaring??

I always had the idea that winds alone are sufficient to lift a glider no matter the angle of wind with respect to the flat land.

What about dynamic soaring? Can I do that?

Please advise. Thanks

Aaindthu
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Old 09-28-2018, 06:39 AM
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Originally Posted by aaindthu View Post
Quorneng,

I was wondering about the same. I thought the winds blowing parallel to the ground alone are enough to lift a glider. Is a slope must for soaring??

I always had the idea that winds alone are sufficient to lift a glider no matter the angle of wind with respect to the flat land.

What about dynamic soaring? Can I do that?

Please advise. Thanks

Aaindthu
As outlined in the link I provided earlier, when the wind blows and hits a barrier it has to go up and over creating a pressure zone. This is best when the wind hits the barrier/slope/hill at a 90 degree angle, directly into the hill. If you get 10 degrees to the left or right the lift drops off dramatically.

The slope/hill/barrier doesn't have to be very big. I have slope soared with my very light wing loading discus launched gliders using 2 foot dunes.

How to slope soar
https://www.youtube.com/watch?v=MxaBfHYnP9c

Slope soaring
https://www.youtube.com/watch?v=B2WdIXyzFD0
https://www.youtube.com/watch?v=Rn_koNkd_k8&t=7s


Slope soaring on a very small slope
https://www.youtube.com/watch?v=y311gXQaHnw


The speed of the wind and the height of the hill combine to create the lift. How much you need to fly the glider is based on the wing loading of the glider.

Dynamic Soaring? Not likely with that glider. Dynamic soaring is usually done with gliders specially designed for the stress. You also need a specific geography in order to do dynamic soaring.

https://www.youtube.com/watch?v=B2WdIXyzFD0
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Old 09-28-2018, 06:59 AM
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Originally Posted by AEAJR View Post
As outlined in the link I provided earlier, when the wind blows and hits a barrier it has to go up and over creating a pressure zone. This is best when the wind hits the barrier/slope/hill at a 90 degree angle, directly into the hill. If you get 10 degrees to the left or right the lift drops off dramatically.

The slope/hill/barrier doesn't have to be very big. I have slope soared with my very light wing loading discus launched gliders using 2 foot dunes.

How to slope soar
https://www.youtube.com/watch?v=MxaBfHYnP9c

Slope soaring
https://www.youtube.com/watch?v=B2WdIXyzFD0
https://www.youtube.com/watch?v=Rn_koNkd_k8&t=7s


Slope soaring on a very small slope
https://www.youtube.com/watch?v=y311gXQaHnw


The speed of the wind and the height of the hill combine to create the lift. How much you need to fly the glider is based on the wing loading of the glider.

Dynamic Soaring? Not likely with that glider. Dynamic soaring is usually done with gliders specially designed for the stress. You also need a specific geography in order to do dynamic soaring.

https://www.youtube.com/watch?v=B2WdIXyzFD0
I was going to try and achieve something like in the fourth video link - like micro sloping. Flying to and fro perpendicular to the direction of the wind.
I wish I put ailerons, but now it's too late. I am going to try it with rudder elevator setup. Will it work ??
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Old 09-28-2018, 07:09 AM
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I have sloped my rudder/elevator gliders many times. Wonderful experience.

Just remember that you ALWAYS turn away from the hill.
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Old 09-28-2018, 07:36 AM
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Originally Posted by AEAJR View Post
I have sloped my rudder/elevator gliders many times. Wonderful experience.

Just remember that you ALWAYS turn away from the hill.
I will remember that. Thank you
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Old 09-28-2018, 11:22 AM
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aaindthu
I am not sure your glider will be able to fly like that one in the fourth link.
It is a super efficient glider that is cable of flying very efficiently in quite a strong breeze (22 kts) and I expect the pilot was also pretty skilled as well.
My guess is you will need a bit more of a slope and with a bit less wind for your glider to be able to do the same.
The big advantage of slope soaring in the wind off the sea is that the air is not disturbed (the sea is very flat!) so the glider is not upset by any turbulence but be warned there are some extra aerodynamic difficulties when manoeuvring very close to the ground surface.
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