TOP FLITE Stinson SR-9 / Master’s Workshop Project Flight Report

TOP FLITE Stinson SR-9 / Master’s Workshop Project Flight Report

More than a few months (and a whole lot of dismal, gray winter weather) has passed since I shared with you the final Master’s Workshop column installment on building the Top Flite 100” span Stinson SR-9. It turns out that I have been involved with this project – working on it more or less regularly – for just about three years. As you might expect I have become somewhat attached to it, and not a little protective as well. (I can hear the voice from the back row now, suggesting that “If I’d built that I’d hang it up in a safe place and never think of risking it by trying to fly it.”)  I have those thoughts too, but a long time ago I made a deal with myself. “If I’m going to build all these prodigious scale airplanes…and write about them in print and on line…I owe it to everyone involved to FLY them, too. So, if it comes out of my shop, it’s going into the air.” With all that said, I was not in any big rush to take this model out to the field just to see air under the wheels for a few minutes…everything had to be right before I’d accept the risk.

Well, it was worth waiting for. The Top Flite 1/5 scale Stinson SR-9 is a winner. On a low, scale-airspeed pass down the runway, this airplane will have you wondering “Is this how it was like, back in 1939?” Let me tell you all about it. Note: ALL the photos in this presentation were taken by my good friend Gary Ritchie.

Remember all those shots of this project on the bench as it came together (slowly), with the promise that it would someday turn into a real airplane? This is what all that was all about. Except that the trees might be too big to be in correct scale, this would seem like the time I would be asking you, “Wanna’ go for a ride?”

 

All the work I put into getting the landing gear properly aligned and those classic ‘30’s wheel pants to fit just right was worth it. This airplane ground handles perfectly (for an antique taildragger). With full “back stick” (up elevator) ALWAYS while taxiing…just as I always did flying full scale old-time tailwheel airplanes…this Stinson exhibited NO tendency to nose over in any of that grass, even going downwind.

 

What…ME look a little bit tense with anticipation? You’d better believe it. Even after all my years of flying RC scale airplanes, anytime I have a new one lined up at the end of the runway, paused at that moment when there are no more excuses, I have all the all those fleeting thoughts of bad things that might happen just like everybody else.

 

Over the next five seconds I learned a lot…she hesitates just a bit and lumbers as the power comes up. There’s very little P-factor/precession pulling to the left…the rudder corrections I’m using could be due as much to bumps on the runway. She accelerates, but not very fast. As she passes the midpoint of the strip I realize she’s probably not going to lift on her own, so I ease in a little “up” stick pressure

 

…and she unsticks herself from the grass and settles into a really convincing scale-like climb-out all by herself. By the way, the manual in the kit said this airplane will want some “up elevator” pressure to lift off. Right away I think, “She’s kinda’ slow”, and then I realize”… that’s the way she’s supposed to fly.” In the same instant it’s clear that this airplane has settled into a safe, stable climb without any more help from me.

 

She flies great! I ended up with a 22×14 wood prop…cleaned up a bit from the way it came out of the box…being turned by my AXI 5230-24 motor running on 8S (2 Venom 4S 5000 25C packs in series. This is exactly what it appears to be…the airplane is in like it’s on rails level flight at a bit over half throttle. The impression of scale speed (the full scale job would be hitting about 90 to 100 mph now) is excellent, as is the feel of the airplane, solid and stable with no sign of wanting to wander off heading.

 

Back to a ground shot. There’s no way to appreciate how big that 100” span wing really is until you see it all assembled, ready for action.

 

In the air that wing is even more impressive. On a low pass close overhead like this you can’t help feeling the presence and mass of this airplane.

 

Just like everything else, the flaps work as advertised. Per the manual, I set up about 1/16” of down elevator trim compensation mixed to full flap (about 40 degrees) using the capabilities of my Airtronics SD-10G radio. At about 25% power this gives me a smooth transition into a slightly steep (nose down) glide without any increase in airspeed. For added scale effect I am using the “Servo Delay” feature of the SD-10G transmitter to slow the flap extension/retraction time to about 5 seconds. That looks impressive on the ground and gives me flap extension in the air with no sign of bounce or pitch-up.

 

Just another low pass for the joy of it. This time I’m closer to full power. The airplane doesn’t go much faster that way, but it is a little more responsive to control inputs.

 

Same pass. You can see by the trees that photographer Gary Ritchie had to pan a bit to frame the airplane on this shot. By the way, I’m able to do a nice “scale” pull-up at the end of a pass like this without having to go all the way to full throttle.

 

Back home. This is a BIG, impressive airplane. After only a few test-and-trim flights, it has met all the expectations I’ve been building up over the three-odd years I’ve been working on it. By the way, none of that intricate detail on the dummy engine, working doors, scale strut fairings, etc. broke, fell off or otherwise did anything bad. I’m gonna’ keep her!

(By the way, my friend Randy Smithhisler, an experienced E-power scale builder and competition flier, is working on one of these things too. Our plan is to get them out at the field together … I’ll keep you informed.)