Tbolt65

I built a Top Flite Gold Edition P-47 with an O.S. 91 Surpass 4-stroke a number of years ago and am now overhauling all my planes having been out of the hobby too long.

I built her heavy at 13# - Robart retracts, full cockpit and pilot, after-market fiberglass cowling, onboard digital ignition system (resulting in need for two battery packs).

My recollection is that although she flew well straight/level, loops were difficult. I have two questions I hope someone can help with:

1. What's the best prop to use given the setup? I believe the last I tried was a 15x6. I think going to an 8 will increase top speed but the theory says takeoffs longer and less acrobatics.

2. The two battery packs weighed 13 oz. I can reduce that a lot by using a single 'C' size NiCad for the ignition (1.2V) instead of the 6V packI used before. Since ignition is on only when throttle is below 1/4, I think that'll still give me at least 3 flghts between charges. What do you think?

Thanks in advance for any suggesitons!

Tbolt65

Fidelity101

My Feedback: (13)

It doesn't look like your question has been answered. Have you figure it out yourself? I have a NIB OS 91 Surpass 2 for my TF P-47 and I was going to start construction soon. I was also thinking of converting the engine to ignition to improve reliability...or even going with a Saito 125 for more power as I like my planes slightly overpowered.

Tbolt65

I never got an answer but I ended up converting an Ultra Stick I had to 20cc DLE gas (which I love) and took the Saito 150 and installed it in the Thunderbolt. Only had to increase cowl opening for the Saito muffler so converting was easy. Now I've got plenty of power - the OS91 Surpass was under-powered given the weight on my plane. If you're running a 4-stroke inverted then I suggest having an onboard ignition system. I do love the plane. Enjoy the building process!!