Update: Nov `98
"WHIRL".. a small .10 -.12 powered direct servo rotor controlled Autogyro
Jim Baxter
15% larger than the "Minnie", this model weighs 20% less (less than 25 ounces) and has a disk loading about 10% lighter...
Realizing that a ½ A engine (in this case a .061 Norvel) , would not handle this attempt at a lighter ½ A model , it was deemed necessary to install an OS .10 engine and modify the tail which proved unsuitable for this relatively large
rotor (for such a low powered model )...
An autogyro this small and light will not be flyable in a very strong wind... While it will probably be controllable in a
good breeze of 5-10 kts., landing it without breaking it would be a real challenge, thus it will not be flown in winds over about 5-7 Kts.
Note... the two top photos show the modified version, with the new tail mounted aft a few inches.. The bottom photos are of the original model... Select a photo and click on it to see the larger, easier to view photo.
Click on the photo on the right for a virtual -full-sized- photo of the flex hub on this model...
A little flight test history......
March: First try: Engine not running well, prop too large, and it simply sat there after a hand launch and would not pentrate a wind of 5+ kts.
March: Second try (after a little tuning of the engine, but still not very strong?) It still would not penetrate a wind of 5 kts... and when it started to turn right and downwind I virtually lost control and dinged it. Surprise! Almost no damage!
Some engine work and possibly a different prop needed... These Norvels seem to need that special plug they advertise...? My prediction that it would not fly in much of a wind seems to be holding true, unfortunately.
April: Attempts to keep it airborne and stable with the Norvel have been unsuccessful. Engine will be changed to a .10 and the tail modified.
May: The original tail was removed, and a small Suitcase Minnie style tail installed and moved aft about 6 inches... (see top photos above) The power was upgraded to an OS .10, and ultimately an ASP .12, and the model is now flying very well, and will eventually be re-designed to include a new tail design and location....
Fall 1998: Final flights completed, the model was deactivated so the radio, engine, etc., could be used in a newly designed
version of this model....
FINDINGS: The basic design was certainly stable, but too large for a small ½ A engine, but fine for .10 to .12 power.
The very high aspect ratio (16+) blades were satisfactory, however certainly not exceptional. I believe a ratio closer
to 12 would perform better on this model. Based on this experiment, it appears [to me] that the maximum rotor size for most ݪ A engines is approximately 32 to 33 inches... Anything larger seems to create a rotor drag just too much for the tiny engine to overcome.
rev..11-18-98..jb