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Notes

I am currently re-designing and building the Carbon Dragon into an aluminum structure (fabric covered)  and adding a Giant Scale Model Aircraft Engine of a reported 20 hp and 10 lb weight.  It probably will be 15 # all up.  I had planned to keep the same platform and weight and so far I am on target for weight at 350# gross.

 http://www.homebuiltairplanes.com/forums/showthread.php?t=24732
<http://www.homebuiltairplanes.com/forums/showthread.php?t=24732>

I am finishing up the construction of the tail and the next step is detail design of the boom/pod structure.

I plan to have spoilers in the wing located and sized from one of Jim Maupin's other gliders the Woodstock.

I plan to eliminate the spoiler/drag brake in back of the pilot's head.

Talking and reading there seems to be some doubt as to the need for the flaps. It certainly would be less complicated and less weight to not have them.

I have been told by another builder: "The first flap setting does give a few MPH slower stall, the other three settings are pretty useless. The negative setting actually decreased my glide slightly when I tested it in smooth air. Mick at Wallaby said if he built another one he would build with ailerons and no flaps. "

Bill said you might have some insight into the answer to that question.

Do you think the flaps necessary and effective?

Donald Berliner
Medford NJ.

Dan Armstrong wrote:

Hi Don,

I am glad to answer your question and your project sounds interesting.  Here are a few thoughts:

- Your idea of putting the spoilers in the wing sounds really good.  The central spoiler was not as effective as regular spoilers and caused a noticeable nose down trim change.  Jim added the central spoiler after the glider was flying and the flaps proved to be ineffective as glide path control.  The central location of the spoiler was an easy modification to an existing glider.  I flew the test flight of the spoiler on the day that the glider was transferred to Gary Osoba, so I only have that one flight to judge how effective the spoiler was.

- The glider will fly just fine without flaps, with a small reduction in both climb and penetration performance.  We flew the glider mainly from auto tows and had noticeably better climb performance with the flaps down.  One flight was behind a slow ultralight towplane and the flaps were required to fly slowly enough to stay on tow.  When towing behind a faster towplane,  it was useful to put the flaps up 5 to 10 degrees. The glider trimmed faster and also had lower drag at faster airspeeds.  If you don't have flaps, the reduction in performance would likely be about 5 to 10 percent, if the flaps were flown to best effect.  If I built a Carbon Dragon,  I would separate the flaps and ailerons and actuate them like an HP-18 sailplane.  I would make the spoilers as you suggested.  This would allow very steep and slow approaches with excellent glide path control. My plan would obviously be heavier and far more complex than your plan.  Your plan will work just great.

Best of luck with your design.  I have fond memories of flying the Carbon Dragon and working with Jim Maupin and Irv Culver.

Regards,

     Dan