Al's Thistle

Thistle #2

Update 1/11/2002

Put it in the scrap bin - it's kindling. Tried to fly about 6 times at the CRRC fly in today, but the RFFS was not narrow band enough and every time I flew the flight ended up with a nasty radio hit of some sort. Eventually I pounded the airframe into submission and knocked a coil off one of my Selman actuators. I'll build some airframe for this radio I can fly alone - the receiver can't handle operating with other transmitters running near it.

Update 12/4/2002

Flew indoors at the 495th Squadron club meeting. Their meeting hall is a church function room, approximately 30'x60' with spectators furnature, etc. on the perimmeter. The Thistle flew great, but the room was a touch small for the speed it wants to fly at. This weekend in the gymnasium should be great!

12/2/2002 - Thistle #2 is created

This is the second plane I have built for my RFFS-100 receiver. This is the Jim Duckworth design, scaled up to 112%. Made from balsa. Uses 2 Bob Selman magnetic actuators and a 145 mAh Kokam LiPoly cell. Awaiting my next indoor flying session for the maiden flight. Here are the stats:

Thistle #1

While surfing about the net looking for R/C plans I also looked at many free-flight model pages. One design that struck me as really interesting was the Thistle originally designed by Jim Duckworth but built and described by Martin Greforie. The construction looked similar to D.J. Aerotech's "Roadkill Series" so I figured I'd scale it up and make the appropriate changes to convert it to RC using the D.J. powerplant and building techniques similar to their profile kits.

I built my Thistle with a 21" wingspan and a 4" Chord. Tail and elevator surfaces were enlarged to allow for hinged control surfaces. I mounted one servo just inboard of each boom on the underside of the wing and ran the control wires along the booms. One boom for elevator, one for rudders. Rudders are tied together with a piece of .03" piano wire. I also reinforced the bottom edge of the center fuselage pod with some 1.3mm carbon fiber rod so that it could handle the additional landing weight. Small rudder extentions were added under the booms and tailskids secured to them made from 1/8" x 3/16" balsa.

The airframe is done and all the avionics are mounted and tested. Receiver and ESC are mounted with velcro for easy use on several airplanes. The battery, a Rayovac 9v NiMh fits in a slot under the wing. Friction from it's velcro patch (attached to all my batteries) holds it in place. I'm hoping this battery is light enough. I may have to go to a smaller NiMh pack.

Maiden flight didn't go so well. Again, I tried to push the envelope with the wind. Also I had WAAAAAAYYY to much throw in the controls (like 45 degrees each way). After getting some advice from DJ Aerotec on control throws on their Roadkill mustang (15 degrees) I realized my problem.

I did get some controlled flight, but lost control quickly when trying any maneuvers. I will build this again, fun plane, easy build - about 3 hours time total. Next version will have a 24" wingspan, only 3 ribs outboard on each wing and a different pylon setup, something a little more durable, possibly some foam core laminated with 1/32 balsa. Will have to think on it. This is a workable solution. Maybe a biplane configuration would get the wing loading down to reasonable levels?

Update July 9, 2001

Chris O'Riley has taken the Thistle and got it airborne! Read more about his success at RC Microflight

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