Solar-powered model planes

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Martin
Posts: 744
Joined: 16 Feb 2018, 14:11
Location: Warwickshire

Solar-powered model planes

Post by Martin »

Not really retro so it's in the general chitchat section. I suppose there are some vintage designs that might lend themselves to solar conversion: that would be no worse than converting an old i.c. design to electric battery operation - something that most of us accept nowadays.

Mike (Ralkbirdy) came up with this present design - prototypes really - but they fly really well.



I assisted with the on-board power controller. This is just an Arduino that takes the motor output from the receiver and passes it on to the speed controller.

The Arduino monitors the available voltage from the solar cells and throttles the motor back quickly if the voltage begins to fall below the ideal level. So if you do a loop and the solar cells are facing down, or the sun suddenly disappears behind a cloud, then the motor is automatically slowed down, or even stopped, so as to always keep enough power back to run the radio and servos. You can hold the plane upside down a few inches off the ground when it's cloudy - and there is still enough power to operate the radio and servos, so there's no need to worry about losing radio control.

The solar cells used are about five inches square. Each one makes about 0.6 volts, so with ten in series you have 6 volts to work with. The no load voltage varies hardly at all from cloudy to full sun, but the brighter the light falling on the cells, the more current can be drawn from them - up to about 4 amps in direct sunshine. Maximum power occurs when you draw enough current to pull the voltage down to about 85% of the no load value - so about 5.1 volts with a ten-cell setup. If you shop around you can get the cells for about a pound each if you're prepared to buy about thirty of them. AliExpress is one source. The Sunpower C60 cells are nice and a little more rugged than some other cells (slightly bendable but still eggshell thin and fragile). If you're buying, look for cells that are advertised as 'tough' or similar.

Mike is now working on a twelve cell design and I'm sure he'll be happy to share the details if anyone is interested in building a similar model.
Attachments
solarRegulator.zip
2018-Aug-12 Added feature to only sample solar voltage for first 10 secs.
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Last edited by Martin on 12 Aug 2018, 17:44, edited 3 times in total.
Ralkbirdy
Posts: 44
Joined: 25 Feb 2018, 13:10

Re: Solar-powered model planes

Post by Ralkbirdy »

Clwyd Queen is a 1956 free flight glider/if power plane, it is essentially a typical flying wing. These planes are an evolution of this, putting the motor at the front, building with Depron and adding solar cells for power. Should interest Shaun with his knowledge of Depron and Phil as it has an Arduino based electronics.

https://outerzone.co.uk/plan_details.asp?ID=1877
Ralkbirdy
Posts: 44
Joined: 25 Feb 2018, 13:10

Re: Solar-powered model planes

Post by Ralkbirdy »

Having repaired the Panasonic microwave door switch, time to do some building for my Solar Clwyd Queen.

I use 3mm AeroDepron, it comes in sheets 1250mm long, trim to 900mm. Then cut 2 sheets of 900x360mm, then divide to give 200mm root and 160mm tip. These 4 wing blanks then need to have the tips cut to 15 deg.

I used to use PVA but the AeroDepron is not gluing well, I found that Superphatic was best, so first time building a complete plane this way. The spar is 7mm spruce from a diy store, the leading edge is 3mm balsa strip, about 8mm. Weigh down and wait a while.

Cut 4 wing blanks.
Cut 4 wing blanks.

Glue the leading edge and 7mm spar.
Glue the leading edge and 7mm spar.
Ralkbirdy
Posts: 44
Joined: 25 Feb 2018, 13:10

Re: Solar-powered model planes

Post by Ralkbirdy »

Add 6mm balsa joiner, 3mm balsa to help align when joining.
Add 6mm balsa joiner, 3mm balsa to help align when joining.
Sand leading edge inline with the spar.
Sand leading edge inline with the spar.
The wing is constructed on aluminium bars which hold it straight and keep the skins together with clothes pegs.
The wing is constructed on aluminium bars which hold it straight and keep the skins together with clothes pegs.
Run some Superphatic down the LE, spar and trailing edge, smooth out, add top skin, clamp with pegs with another aluminium bar.
Run some Superphatic down the LE, spar and trailing edge, smooth out, add top skin, clamp with pegs with another aluminium bar.
Place in the sun to dry.
Place in the sun to dry.
Ralkbirdy
Posts: 44
Joined: 25 Feb 2018, 13:10

Re: Solar-powered model planes

Post by Ralkbirdy »

Tip fins are 220x110 3mm cut in half and shaped, elevons are 600x90 3mm Depron, cut to 40mm root 50mm tip.
Tip fins are 220x110 3mm cut in half and shaped, elevons are 600x90 3mm Depron, cut to 40mm root 50mm tip.
The controller, is an arduino, a Pololu 3.3v voltage regulator and a 1-2s Racestar controller.
The controller, is an arduino, a Pololu 3.3v voltage regulator and a 1-2s Racestar controller.
Martin will add details about the arduino sketch and function, the power supply is a 3.3v Pololu regulator, plenty of power with some servos. You need a dedicated 1-2s Esc. Racestar tattoo 8a blheli.

http://www.hobbytronics.co.uk/d24v5f3-3 ... -regulator

https://www.banggood.com/Racerstar-Tatt ... rehouse=CN

The motor and prop are quite specific, you need to identify what voltage you are working at, 12 panels about 7.2v with about 4A, so 28W. The motor / prop combination needs to get this current at this voltage, for 10 panels a 2208 motor with 1800kv and a 6x4 prop should work well. I am going to try out some larger motors for my 12c model.
FBMinis
Posts: 55
Joined: 25 Feb 2018, 17:59

Re: Solar-powered model planes

Post by FBMinis »

Thank you for sharing the details and techniques of your construction process, they are invaluable for a beginner like myself.
Ralkbirdy
Posts: 44
Joined: 25 Feb 2018, 13:10

Re: Solar-powered model planes

Post by Ralkbirdy »

20180629_161348.jpg
20180629_165033.jpg
I use a lot of glass cloth, the 3mm Depron elevons are not very stiff, so I have added glass cloth to the underside, and the upper side has 60% covered by glass cloth which is used as the hinge. The glass is stuck down with acrylic varnish, I get mine from Wilkinsons. The wing join will have glass cloth top and bottom and the solar cells are fixed and then covered with glass cloth. The wing tips where the fins attach have a band added.


Simple box fuselage, holding the motor to the wing and covering up the Rx, ESC, and arduino controller.
20180629_165953.jpg
Ralkbirdy
Posts: 44
Joined: 25 Feb 2018, 13:10

Re: Solar-powered model planes

Post by Ralkbirdy »

Wing joined together with balsa joiner and glass cloth top and bottom.
Wing joined together with balsa joiner and glass cloth top and bottom.
I got these cells to try,  very brittle and you need to solder top to bottom. The the top connection is too thin and breaks when soldering, easy to get, cheap and no good.
I got these cells to try, very brittle and you need to solder top to bottom. The the top connection is too thin and breaks when soldering, easy to get, cheap and no good.
Sunpower C60 cells are all blue on top, goes to black with glasscloth, and have an array of contact strips on the back. This my damaged one, you can see a crease in a corner, but they still work fine.
Sunpower C60 cells are all blue on top, goes to black with glasscloth, and have an array of contact strips on the back. This my damaged one, you can see a crease in a corner, but they still work fine.
Sunpower C60 cells are best, they can be difficult to get, but ebay currently has a reasonable supplier in the UK.

https://www.ebay.co.uk/itm/SOLAR-CELLS- ... eTa9i4PNbA

https://www.ebay.co.uk/itm/SOLAR-CELLS- ... eTa9i4PNbA

I have ordered 25, so will now wait a week to fit the cells.
User avatar
Mike_K
Posts: 669
Joined: 16 Feb 2018, 06:35
Location: Hertfordshire

Re: Solar-powered model planes

Post by Mike_K »

What a great project and thanks for sharing it with us.

Having seen Mike's flying wing at Ponty and having now seen the video of the flying wings in action, I've been inspired to order all the bits you've listed to have a go myself. I'm certain I'll be asking you a few questions in the next few weeks! Solar powered fly-in next?

Thanks

Mike
Ralkbirdy
Posts: 44
Joined: 25 Feb 2018, 13:10

Re: Solar-powered model planes

Post by Ralkbirdy »

It is really pleasant flying in the sun without any concern about how long you have been going for, no battery to go flat or to charge, just pick up and fly away. They are quite light weight so will have to see how they cope with more wind. This 12 cell plane should have much greater flexibility. I tried the 1800kv motor and a 6x4 prop gave about 4A so should be fine. I have had a number of 2212 1,000kv motors but they seem to have disappeared, so have ordered some more 1,000kv and 1,400kv motors coming. I am looking to use an 8x4.5 Graupner CAM folding prop.
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