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Feb 02, 2017, 07:54 AM
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Wing profile for a 3D printed solar glider


Hello everyone, I've been flying rc planes and UAV's for a few years now and want to build a solar plane with a friend. The plan is to 3D print the wing section that wil be holding the solar panels, and encapsulate eerything.
However I have no experience in RC sailplanes and am not sure about which wing profile would be the most appropriate.
From the informations I gathered, a common airfoil is from AG35 to AG37, the plane would be around 4 meters wingspan and wing sections must be at least 40cm large, one other key factor is that the thicker the airfoil profile will be, the harder it will be to lay down the solar panels as they are not very flexible and extremely fragile.

Do you think AG35/37 is a good choice or something better could be used ?

Clement
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Feb 02, 2017, 08:32 AM
Registered User
What does the mission profile look like?
Feb 02, 2017, 09:20 AM
Aurora Builder
Good luck. 3D printing the wing will be very heavy and isn't good structurally. Take a look at the Supra plans for an idea on structure, airfoils etc.
Feb 02, 2017, 12:00 PM
Registered User
Yah forget 3D printer, you need an open structure with carbon ribs to handle the weight and keep the light coming into your cells. Perhaps you need a special profile with a flat extrados for 60 % of the chord. I remember to have seen such type of profile, but where
Feb 02, 2017, 12:09 PM
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Quote:
Originally Posted by alexis aguttes
Yah forget 3D printer, you need an open structure with carbon ribs to handle the weight and keep the light coming into your cells. Perhaps you need a special profile with a flat extrados for 60 % of the chord. I remember to have seen such type of profile, but where
How about posts 26 and 27 in this thread?
Feb 02, 2017, 12:55 PM
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Hi, thanks for so many answers,

Quote:
Originally Posted by Cap_n_Dave
What does the mission profile look like?
The mission is to fly as long as possible, the number of solar cells that we plan to use should provide us 250-300W so enough to charge the 6S battery when it's really sunny, using an 18" prop with 300kv motor I guess we're aiming at a 20-30knts cruise speed.


Quote:
Good luck. 3D printing the wing will be very heavy and isn't good structurally. Take a look at the Supra plans for an idea on structure, airfoils etc.
I know it would be easier to use carbon or balsa but it is part of want we want in this project, of course we're only printing the ribs (word I was missing in my english vocabulary yesterday) and not the entire wing sections, incorporate the panels with those ribs and encapsulate the whole thing. I didn't calculate exactly how much of a difference in weight it would make with balsa but the solar panels are already pretty heavy altogether.
Am looking at the supras plans, thanks for the tip.

Clement
Feb 02, 2017, 01:40 PM
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What type solar panels are you using? Are they flat? Are they flexible at all?

If they cannot be bent, I would design the wing section around the flat solar panels and assume it is part of the wing skin behind the high point (thickest section) of the wing. At 4M in span, I think CNC foam makes more sense. Then you could bag the wing in fiberglass, leaving a depression for the panels, then glue the panels into their recesses. Either way, for maximum efficiency, you will need to design the wing sections using software.

If the panels can be bent, maybe you could use the Supra section, increase the span and chord, and put the panels along the skin in areas to match the top skin curves. In this case, I think I would also recommend a foam core wing, bagged in glass.

Sean
Feb 02, 2017, 01:43 PM
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http://www.hyperflight.co.uk/product...=super-ava-pro

This model is almost 4M in span.

Sean
Feb 02, 2017, 03:17 PM
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Quote:
Originally Posted by sporter
What type solar panels are you using? Are they flat? Are they flexible at all?

If they cannot be bent, I would design the wing section around the flat solar panels and assume it is part of the wing skin behind the high point (thickest section) of the wing. At 4M in span, I think CNC foam makes more sense. Then you could bag the wing in fiberglass, leaving a depression for the panels, then glue the panels into their recesses. Either way, for maximum efficiency, you will need to design the wing sections using software.

If the panels can be bent, maybe you could use the Supra section, increase the span and chord, and put the panels along the skin in areas to match the top skin curves. In this case, I think I would also recommend a foam core wing, bagged in glass.

Sean
Hi, they are indeed bendable by a few degrees to lay down nicely on the wing, I'm considering all options so thanks for your input, I didn't even know about foam CNC but I guess that using such a machine for 1 plane would be much more expensive than just buying a 4m glider.
Feb 02, 2017, 05:05 PM
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I think you are on to something. Just but the glider, and retrofit with motor, battery, speed controller, solar panels, etc.

Sean
Feb 02, 2017, 05:16 PM
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Quote:
Originally Posted by sporter
I think you are on to something. Just but the glider, and retrofit with motor, battery, speed controller, solar panels, etc.

Sean
Did you mean buy ?
I know I could buy a glider and fit the panels, it would be easier and maybe cheaper (not sure since I already have the 3d printer) but it's kind of our challenge to build it using 3d printed ribs, I did the math and the 70 ribs would weight around 800g(1.8 pounds) for 5m wingspan. I'm not sure if that'a lot compared to pre built rc gliders ? They look heavy from the informations I gathered but can't find weight just for the wing sections.
It would be a great project to 3d print it and we are ready to loose a little bit of performance for it, but obviously we want a plane and not a brick.

Actually our initial plan was to buy the AETHER from hobbyking but we figured it would be a much more interesting project to 3d print most of the airplane

Clement
Last edited by clementt; Feb 02, 2017 at 05:27 PM.
Feb 02, 2017, 06:37 PM
Wayne Wimbish
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Suggest that you buy or build something like this with an open structure. Place the solar panels internal in the wing and cover with clear covering. That way you still maintain full airfoil integrity and full light transmission. By buying something commercially available you don't have to spend time reinventing the wheel.

http://www.espritmodel.com/pulsar-4e...plane-arf.aspx
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Feb 02, 2017, 07:31 PM
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Yes. That's what I'm saying also. Buy one, remove some of the covering, place the panels on the ribs, and re-cover with clear covering. It would fly great.

Sean
Feb 02, 2017, 08:04 PM
Wayne Wimbish
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Sean,

We're on the same page. I just skimmed the thread before my post and missed yours. Super Ava Pro would be a great choice too.

Wayne
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Feb 02, 2017, 08:08 PM
Wayne Wimbish
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Clementt,

800g for ribs is half the weight of a normal 4m model. You will want to save weight due to the added weight of the solar cells. I don't see how printed ribs will help with this project.

Good luck,
Wayne
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