Hey Guys...nice thread...let me add my experiences to it. Dave uses a YS140 in his Super Cub, and it has awesome power. I have opted for the Saito 150, (spinning an APC 16-8 prop), just because I had one available. I had to cheat a little when centering the 150 in the cowl. It is actually off center by a very tiny fraction of an inch...not even noticeable...the Dave Brown spinner lines up just about perfectly with the cowl, and the guys at the field congratulate me on getting it lined up right on center. The other cheat I did to obtain motor clearance inside the cowl, was to file down the ribs on one of the Saitos rocker arm covers. It was an easy job to do with a sander, and then I repolished it to look more natural. I have now gotten a good business card thickness of clearance between the cover and the cowl. Only one needed to be done. I figured it's only a cover...cheap and replaceable..and so I took a chance...and it worked out well. Balance is an issue with this plane. I have found it to be very forgiving of an imbalance, but best to follow Daves instructions on CG location. The manual shows the Rx battery nicely mounted next to the Rx. Well forget that. This Cub comes out way tail heavy. Plan on it ahead by putting your battery way forward, (I use a big 6 volt battery), under or alongside the fuel tank, and add your on-board-glow battery up there too. I had to do this, and also I deleted 2 of the 3 tail assembly leaf springs to save tail weight, but still had to add an unthinkable 16 ounces...yep one full pound of lead right onto the motor mount, in order to achieve the recomended CG balance. Now let me add that I flew the first three flights without any lead weight up front, but the planes tail saged down and it was obviously out of balance. I knew it beforehand, but hateing to add dead weight, I though I'd give it a try first. Now, after spending a good bit of time correctly setting up the proper CG, (4 3/8 inch aft of the LE), I have yet to give it a check flight, but weather permitting, tomorrow will provide me with that opportunity. For balancing, Dave hangs his Super Cub from the ceiling on wires connected to the wing mounting bolts. A very handy idea. Much easier than messing around with a modified Great Planes balancer. Those wing securing bolts had to be somewhere and so Dave thoughtfully placed them on the CG. How nice! The Saito 150 has all the power you need to fly Cub like, including mild aerobatics. I'm running standard Omega 15% fuel, but I will try the Saito recomendation of 30% heli mix next time out. I do not need the extra power, but I am told that the heli fuel will bring RPMs up while actually lowering head temperatures.
I installed a 16 ounce fuel tank and got three 10 minute flights out of it, with fuel to spare. Bear in mind that I am flying it Cub like, very scale, very slow. Not much high throttle at all. A flying buddy powered his with an OS120 four stroke with good results. Roll rate is incredibly slow, almost scary, but then it is a Cub...not an Extra. She is a floater, and without a good CG balance youll have to push her down to land. Flaps really slow things down and do require some down elevator mixed in to keep everything nice and level, otherwise she'll balloon quite dramatically. When installing the aileron hinges, do not try for a close gap. Inserting the hinges too far will only cause insufficient aileron up travel as the ailerons will strike the overhanging wing top sheeting. Do be sure you have the prescribed aileron throws before bonding the hinges in place. I used Hitec 5625 digital servos because I like the precise centering and the strong fast authority, but Dave assures us that any reasonable (70 in/oz) servo will do the job well. The real fun I get with the Cub is doing those lovely, slow touch and goes, and flying the circuit at a very low altitude, and very slowly. It looks soooo real. I have been using the stock Saito muffler, exiting the bottom center of the cowl. It was an awful trick getting that to fit, and I will soon be removing that muffler and replacing it with the Saito Flex-Pipe with a pressure tap for the fuel tank. I am quite happy with my Cub, and I'll post a follow up after I fly a few more check out flights. In closing, let me say that in light of the need for so much balance weight up front, I am looking to replace the Saito with a gas motor. It'll swing a bigger prop....more torque and less speed...and the fuel is cheaper. I just have to find one to fit inside the cowl.
Bye for now, and happy Thanksgiving.
Jim