Circular bellcranks- Pro's and Con's

[M Spencer]

ducted sPLIT SYMETRICAL WING AT CENTERSECTION , AND PULLEY / CABLE CONTROL SYSTEM .
Says it won N Zs first aerobatic comp. 1952 .

TAURANGA in those days wasn't a stuck up pack of conceeted inebriate snots , nor was Mt Munganui plagued by juvenile versions .

SEE the previous page for a picture of the PLAN ; av a fag mate .

[M Spencer]

If someones inclined to knock one together , could do a photocopy of this drg. wonder if anyones gotta plan for it .

[Chris Wilson]

As someone suggested, a fully linear system throughout the full range of control motion would require not only a circular bellcrank but also that circular handle someone previously mentioned and a pulley system rather than control horns to drive the flaps and elevators. 
Ted Fancher

And the the circular handle being always rotated around 'its' centre and not the centres of the wrist, elbow or shoulder etc.

[Trostle]

If someones inclined to knock one together , could do a photocopy of this drg. wonder if anyones gotta plan for it .

Like the Aeromodeller article states, this won the NZ Nationals in 1952, so voila, it is OTS legal.  This has been on my list of OTS candidates for years.  I only have a very fuzzy set of full size plans and would really like to get a clean set.  With an OS 20 or 25, this should be interesting.

Keith

[Chris Wilson]

Try a search here Kieth, I am not a member so can't give you a direct link to it but it should be there.

http://www.hippocketaeronautics.com/cl_sport.htm

[Steve Helmick]

From one of Ted's posts: "One last comment, David Fitzgerald, who built a couple of his early morphed Imitation/Excitation ships with the circular BCs after his return to competitive stunt following his Air Force tour of duty told me he thought he was less able to precisely control the  flight path under low tension maneuvers--the wingover in particular--citing the increased sensitivity around neutral due to the circular crank.  Being sort of a neanderthal myself I was never sensitive enough to detect the difference."

It seems to me that the circular BC would be either less sensitive around neutral, or the same in the wingover, since both are essentially at neutral through the straight parts of the WO. That would be comparing a 3.5" conventional BC to a 3.5" radius CBC. Comparing a 3.5" CBC to a 4" conventional BC wouldn't be fair, at least not with the same handle spacing. If you narrow the handle spacing to match the 3.5" CBC, then you'd lose some precision for sure.

Regarding the OH8's, oversize is often caused by flying them upwind (which reduces line tension), by geezer pilots who can't bend their neck/back enough to look straight up. I still intend to try and practice flying them facing downwind after entering from upwind. If the breeze is light enough I have entered the OH8's from downwind and exited upwind, with no apologies. Yes, it's legal.

I believe Ted once wrote that he used to enter from upwind, and turned to face downwind during the OH8's, but changed to facing upwind because that's the way everybody else did it. Apparently, I need to do a lot of dry flying to get used to the concept of doing the OH8 facing downwind, because when I've tried it, I got confused and almost crashed.    Steve