mgnostic

Well after spending the summer getting my kid moved to Colorado and visiting family on the west coast and upteen other things I finally got back to the Staggerwing. It always leaves me curious when a build thread leaves me hanging without some conclusion to the story. An additional issue with the airplane was that the phenolic engine mounting plate started coming apart. This was most likely due to age. Luckily this airplane has an actual firewall that is far enough forward and substantial enough to bolt on a plastic engine mount. Some airplanes with beam mounts don't. The hardwood beams are far enough apart to fit a Dave Brown engine mount between them. I did add a layer of reinforcement to the firewall since it is only 1/8th plywood. I was able to maintain right thrust. I left the beam mounts since they tie the structure together and they are also part of the cowl mounting points. I also added a Hitec gyro on the rudder in an effort to correct the swing on takeoff. Although I haven't yet replaced the landing gear I think it makes a contribution to the swing on takeoff. You can see the gear legs deflecting when the aircraft swings. I think stiffer wire will help this. After the changes to the engine mount I had to adjust the throttle servo endpoints to get a proper idle. After an abortive attempt followed by a glow plug change and retuning of the engine one of the other fliers held the plane while I ran it up to full power. He let go of the plane and it was able to build up enough airspeed for the tail to have authority before it could start to swing. The gyro definitely seemed to make a difference. With a healthy glow plug and full power the plane reached flying speed reasonably quickly and climbed out with a good enough rate of climb. Although it had mostly been trimmed out on the first flight it still needed a few clicks of aileron and rudder to go in a straight line. Although not as fast as a clean sport plane it still has a good turn of speed for a .40 size biplane. Although conservatively balanced it still seemed a little touchy in pitch. It could probably use some exponential on the elevator. The airplane seemed to generally track well and I didn't notice any porpoising, even at lower speeds. Stability around the roll axis is generally neutral. This is as expected given that the upper wing has no dihedral and the lower wing has about a scale amount. The roll rate was reasonable and easily managed. I haven't explored rudder authority yet. The rudder is a little on the small side but aside from the problems on take off, nothing stands out so far. The big surprise on trying to land was the degree to which this airplane carries speed and floats on the landing attempt. Out of caution I came in a little high and hot and it just sailed right on past me. On the second landing attempt I tried lower and slower and it still glided farther than I expected. Out of concern for fuel (rightly so !) I went ahead and followed through with the landing. It settled down smoothly but tripped in the grass and stood on its nose. No damage done. So, it's no trainer but, especially once you get it off the ground, it is a flyable plane. It is certainly not the most difficult thing I have ever flown. It was a rewarding build and I think a laser cut version would be better both in terms of finished weight and fit of the parts. It makes an attractive model and you aren't going to run into one at the field very often.

FlyerInOKC

My Feedback: (6)

Good looking bird, congratulations!

mgnostic

Another couple of flights on the Staggerwing. One modification that I made recently was to bend up a new set of landing gear legs. The stock wires tended to roll under, exacerbating any tendency for the plane to ground loop. This along with the gyro mentioned in earlier posts has really helped the takeoff habits. The airplane still doesn't handle grass particularly well and I I had to do it all over again I might push the landing gear mounts forward up to the leading edge. The first take off was pretty smooth. The airplane likes to have a bit of a run to build speed. Once the tail comes up it is about like any other tail dragger. The second take off was kind of hairy. A cross wind pushed the plane to the side of the runway and a bump pushed it into the air before it was really up to flying speed. At one foot of altitude and full throttle it wanted to drop a wing until it built enough airspeed to continue the takeoff. I think an attempt to horse this airplane off the ground would result in a snap roll if you weren't up to flying speed. Once the airplane has some speed it will climb out with authority. At speed the rate of climb is quite good. At full throttle the airplane seem surprisingly fast for a .40 size biplane, especially for one with a radial cowl on the front of it. I throttled back and the airplane seems comfortable flying around the pattern at 1/2 to 2/3 throttle. I climbed to altitude and tried a couple of stalls. They were pretty benign with perhaps a tendency to drop the left wing a bit before the right. I haven't tried any spins yet. The airplane loops respectably well. That shouldn't be really very surprising given that there is a fair amount of flat bottomed wing. The rudder is relatively small but seems to have good authority at flying speed. Turns are easily coordinated and it is even effective enough to hold the plane for a few seconds of knife edge flight. N.B. Staggerwings really don't like to knife edge. It will do it but it won't be happy about it. The roll rate is just okay. It gets the job done but you wouldn't ever call this a pattern plane. Some planes seem to roll better with a little rudder added in but it doesn't seem to make much difference with this one. I suppose if you felt the need you could add ailerons to both top and bottom wings. I was surprised to find that for an airplane with a flat bottom wing, it tools around inverted quite nicely. Landing are still a challenge. It wants to flat a long way in ground effect and if it rolls off the edge of the runway it is going onto its nose. It might not ever be my "go to" airplane but like the full scale staggerwing it is unique and once you get a feel for its quirks it is a very flyable airplane.

buzzard bait

Pretty airplane and a very nice, detailed report. Thanks and congratulations,
Jim

FlyerInOKC

My Feedback: (6)

Thanks for the info Matt!

mgnostic

This airplane continues to be a bit of an experiment in progress. Two major changes that I have made are adding in a couple of degrees of toe-in on the landing gear and moving the CG back about 3/8 of an inch. The toe-in seems to have helped the ground handling quite a bit. The CG is now about a 16th of an inch behind the line shown on the plans. Most of the CG change was accomplished by moving the flight pack battery from just behind to firewall to lower rear wing mount. I also trimmed off the engine mounting beams since they are no longer used. In post #91 I mentioned reducing down thrust and when I changed to a plastic engine mount I just installed the engine square to the firewall. I'm thinking this was a mistake. What I am noticing now is that there is a notable nose down pitch change when I pull back from high throttle setting to idle, as though the thrust is holding the nose up. The thrust line is almost exactly between the wings and I don't think it would be as much of an issue with a symmetrical wing but my understanding is that flat bottom wings are more sensitive to thrust angle. The 40 year old plastic in the cowl has developed a few cracks so I'm going to be working on the nose anyway. I think I will add a smidge of down thrust to see what happens. I did add about 15% exponential to the elevator and that seems to make it fly in a little more relaxed manner.

buzzard bait

The stab/elevator is always slightly negative to the wing, aerodynamically (on some planes, it is positive as designed and built, but down wash from the wing puts it at a negative angle aerodynamically). This is necessary for the plane to be stable in pitch. The more speed, the more the stab pushes down, so the nose rises. You can reduce it, but you can't eliminate it. Downthrust counter-acts that effect.

One thing that reduces it is to move the CG back. Then the force on the stab/elevator doesn't need to be as different from the force on the wing in order to maintain level flight. So just the fact that you moved the CG back helps.

With a flat bottom airfoil the center of lift shifts more with angle of attack than it does with a symmetrical airfoil, so that is factor working against you, as you said. I'm pretty sure your plane will do better with added down thrust.

Congratulations, quite an accomplishment building and flying that plane, it looks great.

Jim

mgnostic

Thanks BB, I didn't have to get too far into this build to know that it was going to have its challenges. There is a maxim that scale planes are never really finished, the build is just finally abandoned. I suppose that is true of airplanes that get a lot of modifications. Part of the satisfaction in this plane comes from the ongoing tweaks that have improved its flyability. Lots of build threads end with the maiden flight but airplane really isn't quite finished yet. I bought this kit from the local laser cutter after he was done using it for templates for a short kit. It would be interesting to build one of his short kits with his considerable improvements in fit and material and my running modifications all incorporated from the beginning. One think I would definitely change would be to re-engineer the wing mounts to use dowels in the front. A lot of the wing is already sheeted so I think I would just skip the cap strips and just sheet the whole thing. It will never be a trainer but i think there is a plane in there that the average pilot could enjoy. My current build is a G-S Products Stinson SR-6 kit. One of the magazines give it "Best Scale RC Kit of the Year" back in the late 80s. It really is well done to the point of being a bit over-engineered. Most of the parts appear to have been hand cut and the fit and finish is exceptional. There are some pre-shaped parts that must have been expensive to produce. This airplane dates to a time when a .40 size plane was still viable as a precision scale model. The reason for bringing the Stinson up is that both it and the Staggerwing are 1930's cabin planes and both kits kits are roughly the same scale and are powered by .40 size engines. Although is has a considerably more scale outline and more scale detail I suspect that the Stinson will be a much less challenging flier.
I will probably post occasional updates on the Staggerwing, at least until I get tired of working on it.

buzzard bait

I'll follow along. Small scale models are a special challenge.

Jim

mgnostic

I added some down thrust to the Staggerwing's engine today. I used a 1/16 inch shim under the engine mount to get about two degrees down thrust. It seems to have made a substantial improvement. Throttle changes seem to have less impact on the aircraft's pitch and it doesn't want to zoom as much at full throttle. It also seems to unstick a little easier at take off but that may be more a result of improving directional control on the takeoff roll. I added in 25% exponential on the rudder and the plane has straightened out a lot on takeoff. In retrospect I think I was wrong in thinking that the relatively small rudder was being ineffective at low speeds and I was in fact over-controlling. Live and learn.

TCampbell

Matt, your choice of subjects is right up my alley. I have collected several versions of Staggerwing plans with the hope of building one someday. I also have the G-S Products Stinson Reliant SR-6 kit. Any chance you've documented your build on it somewhere?

Keep the reports and pictures coming here, love to see them
Tim

mgnostic

Thanks for your interest. I haven't done much to document the SR-6. It has been built in between and around a couple of other projects. I will say that it has been an easier and faster build than the Staggerwing. It has a high parts count but fit of the parts has generally been very good. The instructions are clear but it would have been nice to have more illustrations. I would suggest that you read the instructions all the way through and stick with the documented procedure. There are some places where there is a temptation to do the next obvious step but if you do it will get in the way of other assemblies later in the build. I have the wing, tail surfaces and most of the fuselage framed up and am about to start sorting out servo placement. I haven't started with any of the "golden panel" material yet. Although it is a relatively small model at 1/8 scale, the fuselage is laid out such that there is room for a lot of cockpit detail. If you have any specific questions about the SR-6 just ask and I will answer as best I can.
Back to Staggerwings, Lazerworks.com has short kits for at least two versions of the Staggerwing.

ToddModel

Hi Folks-- I've resurrected an old Aristo-Craft Giant Beechcraft G17S Scale biplane model with 45" wingspan and I think I have all parts and blueprints. Not sure if I still have any other instructions-- does anybody know if there was any other instructions that came with the kit? I haven't built a model in several decades, but now is the time to get back into it. Let me know if there are any instructions I may be missing!

Thank you!

Todd

mgnostic

There is a 23 page manual. it's not great but it does have several isometric drawings that are helpful. If you will PM me with an email address I will send you a copy of the manual.