JC's Planes and Projects

Sig Wonder

I needed something small and fast building after I shelved my Phantom project. I was also moving into a house and needed to set up on a small building board until I complete my worktable. I bought this kit after watching a fellow club member fly his. Kermit's Wonder was smooth, fast, and quiet with its little OS .15 FP and I had to have one. I picked up some mini servos at a swap meet along with an OS .15 FP. Heck, all I needed was the kit. It has been a joy to build with no real problems. I did chuck the two enormous hunks of balsa that I was supposed to carve the wingtips from and just built some up. I just wish the kit was laser cut - then you could build them by the dozen! Radio installation was no problem except for many balance checks to make sure that no lead would be needed to get the proper CG. Cramming the recommended 4-oz Sullivan tank into the little fuselage was a chore. It is nearly an interference fit! Fortunately there are no signs of fuel foaming. I chose the Blue Angels version of the Wonder, but made the yellow starburst larger for better visibility. For a some scale effect I bought a small Sig canopy and trimmed it with yellow vinyl pinstriping. The canopy was affixed with Pacer RC56 glue.

Reflections: The Wonder is a success! It is definitely not for the novice pilot because of its speed and size. Straight-line speed is brisk, but not as fast as expected. This is obviously due to the APC 8x4 prop maxing out. An 8x5 would be faster and worth experimenting with. The 4-oz fuel tank is more than adequate - I was up for 15 minutes one flight and landed with a good reserve. The vertical on the plane is untested due to a nervous pilot and windy weather. A few full throttle pull-ups to the vertical were on the verge of breathtaking as the little plane shot skyward. This is where you wonder where your rudder is! Maybe this is why they call it the Wonder?

The Wonder Chronicles:

10/23/00 - Plane is complete and ready to fly! I actually came in under the weight of the prototype! That is a first! Well, it is mostly because I used mini-servos, battery, and RX. Hoping for good weather this weekend.

10/28/00 - I flew the plane three times today. I was a little blustery with 5-15 mph winds from the NE. I had my brother doing wind sprints all week in preparation for the launch despite his complaints about pain from recent arthroscopic knee surgery! Anyway, the little OS was fired up and tuned. The plane was handed over to the launcher, the throttle advanced, the "high-sign" given, and the plane given a running launch. It was pure excitement as the little Wonder just flew out in a nice climbing turn! It VERY rapidly gained speed and I quickly backed the throttle down to half or less. My brother returned to help me trim out a slightly heavy wing and a slight tendency to climb. After about three minutes is was flying "hands-off." The light plane handled the blustery conditions very well - but it would have been more enjoyable with less wind. I was a little worried about my selection of a Royal blue scheme. Fortunately, the yellow trim jumps out from the blue background and gave me an excellent perspective. After about ten minutes, I set up for a landing and killed the engine. The Wonder settled in for an almost "hovering" landing. Whew! It was the most exciting test flight that I have had. Make sure that you have a helper launch the plane for you on your test flight - I would have had my hands full doing the launching and trimming myself. Subsequent flights showed that launching the plane is no problem - a few quick steps and it is flying away. Not having rudders took some getting used to - especially in the breeze. Any crosswind will turn the best loop or Cuban-eight into a corkscrew.

11/5/00 - Got in four more flights. I noticed what I believe to be a thrust-line problem. Plane will dive from level flight when power is abruptly reduced. Solution is for more down-thrust.

11/8/00 - Shimmed in a little more down thrust. Hoping for some good weather to test.

12/3/00 - I have been unable to test the thrustline modification due to lack of good weather. I have added yellow strips to the bottom of the wing for visibility on overhead maneuvers. Note (6/10/01): I have since removed the additional down-thrust. The amount shown on the plans and built into the firewall has proved to be optimal.

6/2/01 - I have had the Wonder to the field once this season and it is a real hoot! I had a calm day and did burning low-level passes to rolling vertical pull-ups. It really gets the blood pumping and it is stable as a rock in the calm weather. I tried launching it myself one day and ended up cart-wheeling it. It was a botched launch mostly, but I wondered if I could not get more thrust from the little OS 15 FP. I ran across an article in R/C Report detailing modifications to hop up the little mil. I removed the mute from the exhaust and bored it out to 0.5 inches. I also drilled out the exhaust hole with a slightly bigger bit. I can't quantify the results because I never took any rpm readings, but R/C report found an extra 1800-rpm with these changes on an 8x4 prop!

My human catapult (my brother) claims that it has greater launch thrust. What I can be sure of is at least a 50% increase in fuel consumption. I ran out of fuel on the first two flights at eight minutes. I just could not believe it the first time, but got a little wiser on the second. I now have my timer set for 7 minutes. The increased fuel consumption is a strong indicator that the hop-up mods indeed work. I plan to try an 8x5 propeller to see if I can harness a little more of that horsepower.

6/10/01 - Flew the Wonder six times yesterday. I tried APC 8x4, 8x5, and 7x6 props. I liked the 7x6 the best and this is what I will fly. This prop gave the best combination of launch thrust and a straight-line speed. The Wonder and OS .15 FP continue to be a very fun combination. I did a test of the 270-mah battery pack after flying yesterday. I had 230-mah of capacity left! That micro radio gear does not use much current at all.

4/21/02 - Flew the Wonder four times yesterday. As always, it was a blast! I had forgotten how much fun this little plane is. This was the first session where I did all the launching myself. I had no problems. The present motor/prop combination gives excellent launch thrust with the plane powering away at a thirty-degree angle. I knocked the fins off on the last landing. Mostly it was just pilot error, but the elevator throw had a little to do with it. I fly on low rates with the plane under power. The concentrated prop blast will make the elevator and ailerons quite sensitive. When gliding or at idle the opposite is true and the plane can be sluggish. I forgot my technique of landing on high rates. That is what happens when you don't fly a plane for a year! Anyway, I touched down hot and she skidded sideways breaking off both fins. It will be a 15-minute repair job. If you are building a Wonder, I would suggest adding some triangle stock at the fin/stab junction for more strength.