DLG style slope soarer

by apnewton | December 5, 2014 | (9) Posted in How To

The design for this lightweight aerobatic slope soarer was inspired by a DLG or discus launch glider. I wanted an ultra light sloper that would fly in very light winds and on small slopes.

Plan, specs, materials list, build and flight videos below.

There are a few unusual design features in this build.

Rudder and elevator are operated by a pull line acting against a torsion spring glued into the hinges. This means there are no pushrods along the tail boom and servos can be mounted well forward in the fuselage pod.

Torsion springs bent from 0.4mm SS wire

The trick is to make a torsion spring strong enough to operate the control surface against the airflow but not so strong as to overpower the servo. The 0.4mm SS wire provided as pushrods for the Versus DLG turns out to be perfect. 

Glueing down the torsion spring on the elebvator hinge line. ID card plastic reinforcement.

Tensioning the pull line. (150lb Kevlar kite line)

 The Armin style wing is 6mm depron covered with 43 micron iron-on document laminating film (sometimes called "New Stuff" by the RC community)

More glue needed here (So I discovered on a hot day!)

This is a great aerobatic sloper and will work in anything over 5kn on a decent slope. In 10kn it will work on any slope. In 20kn it's very exciting but takes some skill to stay in control.

Dimensions (Sketchup file available)

SPECS

Wingspan - 1.5m (65") Armin wing

Length - 104cm (38")

Flying weight (500mAh LiPo) - 410g

Ailerons

Elevator

Rudder

TGY 9018MG servos x 2 (elevator and rudder)

HXT900 servos x 2 (ailerons)

 

MATERIALS

6mm depron

43 micron laminating film

60 micron clear packing tape

2 x Skyshark P4X spars (7.6mm x 820mm)

- Wing spar 820mm

- Tail boom 700mm

150lb Kevlar kite line (pull line)

0.4mm SS wire (torsion springs)

Soft packing foam (nose cone)

4mm CF rod (wing tie down bars)

 

Overview and build video

Aerobatics in 10kn

Gliding on a 4m rock slope (dihedral wing)

 

VERSION 1.1 adjustments

After extensively testing VERSION 1.0 (above) a few issues showed up. The cut-out ailerons meant there was only a small amount of hot glue holding the sub trailing edge of the wing together. On a hot day the glue let go and the wing opened up along the aileron hinge line. I needed to reglue and tape along that area. At the same time I extended the ailerons to the wing tips for better aerobatic performance.

Due to constant pull from the springs the rudder servo started to lift out of position. Extra foam bracing and glue was added around both servos.

LINKS

Bulk Depron - http://www.tradewarehouse.com.au/more/depron-foam/white.html

Skyshark P4X spars - http://www.kitesandfunthings.com/ProductInfo.aspx?productid=SSP4XCAM0

New Stuff iron-on film - EZload laminate - GBC Australia

Blank ID cards - Ebay http://www.ebay.com.au/usr/y2store?_trksid=p3984.m1439.l2754

 

Newton Airlines blog (Plans) - http://newtonairlines.blogspot.com.au

Website - http://anewton.net 

 

UPDATE 21st Dec 2014. More aerobatic action with full span ailerons and some beach level sand skimming.

COMMENTS

alibopo on December 7, 2014
Great build. The torsion springs are pretty inspired. Just curiosity, but I wondered if you had any problem with overheating due to the servos always being on-demand? Though I suppose all the forces are pretty minimal compared to a powered aerobatic model. Probably no different to a plane that needs some down or up elevator to maintain level flight.
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apnewton on December 7, 2014
The servos are buzzing most of the time but they can take it without any problems.
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dav on December 8, 2014
Just beautiful
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ttprigg on December 11, 2014
Great Build! I would love to see the sketch-up file. I think I am going to make one. I built a MIMI DLG (RC-Group Forum) and I figured out the torsion springs at that time (In that case, the end of the spring is inserted in to the end of the balsa. It did not split the thin balsa but I was worried. Your solution adds weight but alleviates that problem.) What I could not figure out was how to secure the string to the servo arm. Your solution is terrific. I tried to put a servo-screw into the end of the arm. To get it tight enough to hold, I would also change the setting,,, then it would slip... a real mess. I will be adding you detail to that build. Wondering if you think that the MG servos would be required on the elevator and rudder. I am cheep and I have the hexatronic 9g's "in-stock".... Also, I am going to try to use the DTFB with the paper pealed and the "New Stuff" applied. I'll post the results. Do you have a thread on the forums?
Thanks again for a great article! 5-stars -
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apnewton on December 11, 2014
Thanks ttprig. The only servos i have tried for spring pull are Dymond D47 (on a Versus DLG) and TGY9018MG on this sloper. Give the 9gs a go and let us know how it goes. Email me at apnewton at gmail for the sketch up file.
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RCElement on December 7, 2014
Very good job! I'm working on a simular concept. Making a dlg bird style plane from foam.
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28th St. Air on December 11, 2014
Another excellent presentation. very inspiring.
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Beardman on May 15, 2015
Great job! The torsion spring is just ingenious! Thanks for sharing!
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DLG style slope soarer