>Dan,
>
>I've pulled this thought off the OTS thread because there's
>probably more info here that shouldn't be buried. You
>replied to my note regarding the S-1 Ringmaster and said
>that the OS 15FP would be the way to go, correct?
Here I go again, but...
The single best-flying Sterling kit Ringmaster I have ever flown or seen was somone's (whose name I unfortunately can't recall) box-stock S1 with a full opaque dope finish, powered by, {cringing} a box-stock 15FP with something like a 8.5-4 Master Airscrew. I didn't weigh it, but it was in the ballpark of 30 oz.
David Fitzgerald and I were out flying one day at the old Napa circle and this gentleman joined us. Had a full silkspan/dope job (Darrell Waltrip "Western Auto" #17 NASCAR colors) , a 15FP, and the classic +-60 degree, super-fast elevator motion. Of course, he flew it and it just about crashed at every attempted maneuver due to the weight and the "Insta-Stall" control setup. We got him to greatly narrow the handle spacing to get the stalls under control (down to about +-20 degrees, and some nose weight, as I recall), and then it flew pretty good. David and I, being big-time experts as we are. noticed this, and then we asked to fly it. Both of us were amazed at the performance, since we both knew for certain that the Ringmaster as an unredeemable dog. But this airplane, while not a really Walker Flyoff candidate, was at least pretty darn respectable. And what struck me about it was the remarkably consistent power.
This experience was what got me aimed towards trying to develop the 20FP for "35-sized" planes. I mentioned it to Ted, and before long the whole story of WAM "A" Stunt came to light, and the wheels began to turn - leading to the current situation and the 20FP setup.
Note that in the other thread, I noted that we had tried the 20 and the 15 on a Ringmaster. A 20FP, or a slightly-less-powerful Veco 19, will fly the Ringmaster faster than you want or need, or helps overcome the other problems. ringmaster S-1+Veco19+9-4 APC+62 foot lines = 4.2 second laps. Ringmaster S-1+20FP+9-4 APC+62 foot lines = 3.8 second laps. The 15 drops it right in the ballpark at about 4.5 seconds laps with am 8.5-4, with sparkling performance all around. I think it's the ideal engine for this airplane.
Of course, it's still a Ringmaster, and it will benefit from sensible weight reduction. But not too much. The superior performance with these engines, and keeping the controls to the stall limit will keep you from stalling it - but less tendency to stall means tighter turns, and tighter turns mean more load in the corners. And the Ringmaster wing structural design is somewhere between poor and dreadful. Excessive weight reduction and an inefficient structure don't go too well together, and it's very easy to shed a wing if you are not careful. Ted's superlight Ringmaster with monokote pulled in alarming amounts of dihedral in even round loops before it's untimely demise, and Davids outboard wing ( lightened by hollowing out the leading edge) broke off entirely and fluttered down at my feet during a contest one day. Point is, you don't have to, nor to you want to, cut away too much wood. It will fly fine into th upper 20's-low 30 oz range, and if you overdo the weight reduction you will end up with a balsa snowstorm.
The other thing to note is that the engine is so good it will trick you into forgetting what you are flying. The airplane with a 15FP or Veco 19 will do anything you can think of with ease. As soon as the engine quits, it turns back into a Ringmaster. David crashed both his and Ted's multiple times when he was fiddling around at the end of the flight with horizontal hourglasses, bolo loops, etc, when it unexpectedly ran out of gas. All of a sudden an airplane that will easily do half-sized square 8's can't execute a half-loop from 60 degrees to get upright.