RingMaster Thrust Line

[Motorman]

Did the original S1 Ringmaster have the thrust line higher than the wing? I built from a modern kit and I couldn't figure out why it wanted to go up better than down with the thrust line square on bench trim. Then I realized the engine is higher than the wing so what looked square was actually up thrust lol.


MM

[Scott Richlen]

But if the engine thrust line is higher than the wing center-line wouldn't that create a downward rotational force?   

[pat king]

The thrust line on the original Ringmaster S1 was 1/4" (.250) above the wing centerline and 1 3/32" (1.0938) below the horizontal stabilizer centerline. The Sterling P-51 has the thrust line 1.425" above the wing centerline. The Sterling Yak 9 has the thrust line 1.98" above the wing centerline.
Pat

[Chris McMillin]

Yes, it does.

But if the engine thrust line is higher than the wing center-line wouldn't that create a downward rotational force?   

[Fredvon4]

I now have three RMs two are traditional S-1 profile versions...one of them a ARF from Mike Griffen and one a kit from Pat Johnston

The one varient is aCore House Rugged Stunt Trained form Phil Cartier with RM(ish) tail feathers

In each of the three I built Zero rudder and zero engine off-sets

Two of the three (PJ kit not finished and maidened yet) only need fuel tank adjustment and a slight LO/CG shift to fly well

I have read about 1 to 2 degrees of out side thrust and perhaps 1 to .5 degrees down

Mine are zero zero

I tend to think...straight build, proper CG, Proper LO rake is more key than any rudder or engine offsets

There are many planes with the thrust line above or below wing CL as well as stab /elev above, in line, or below wing CL

 I will let the experts of each different stunt plane configuration debate the engine thrust line

IMO , for the S-1 Ringmaster, it seems to me that zero zero zero is a workable set up IF the wing is true, and the stab /elevator and rudder are all square and or 90 degrees true

[Gary Mondry]

I offer you these, from an S-1 kit from the 1990's, I'd guess.  While I have several different contemporary S-1 plans that show the thrust line raised, I don't see it on the die crunched fuselage blank.  (I hope the photos didn't lose too much in re-sizing).  Barry Baxter's plans show the thrustline coincident with the wing centerline.  Reach your own conclusion.

Gary

[pat king]

The 1/4" dimension is the average from 5 Sterling S1 kits. I believe that the dimensions of the steel rule dies that were used to cut kits changed every time the dies were rebuilt or replaced. I know that the die cutting of many old kits that have full size plans do not come close to matching the plans. It seems that the dies were made so that the parts sort of looked like the drawings. Having made CAD drawings of old airplanes and boats from the kit parts I can tell you that many of those die cut parts would not fit together without modification or give a decently shaped model.
Pat