While I am all for weight savings, reducing the amount of servos in this example doesn't really save any weight. A Hitec HS-85BB servo weighs .67 oz. each, 1.34 oz. per pair. One standard servo on either the starboard or port side for rudders weighs more than a pair of HS-85BB,s but does save some money. Modifying the stab to accommodate an HS-125MG and routing the wire is a bit of a headache. The single HS-125MG weighs .84 oz. as compared to (2) HS-85BB at 1.34 oz. but the HS-125MG is 6" farther behind the CG so I'm not so sure there is much if any weight savings there either. I personally wouldn't trust a single HS-125MG to handle the elevator as it is a mini servo and has the same torque rating as a single HS-85BB. I do agree with keeping the powerplant on the light side, seems the OS .55AX is a pretty good choice for the money.
patzane, Stick Jammer has reinforced my observation that to listen to a single source rarely provides you with the best solution to your questions, lol...
Thanks, Stick Jammer!
To focus upon any single aspect of a project without considering the entire picture, can be misleading. I fly standard servos on all my aircraft with the exception of my Goldberg Sukhoi and Kaos 90. I'm a sport flyer, fly weekends as a rule and don't compete. In my world, hanging 4-standard servos behind the engine doesn't compute. I spent $125 on the Bobcat. If I can't use the equipment I have on hand, I'll spend abit additional to get that item or two. The HiTec MG125 is a classic example. Torque on the 125 is similar to standard servos that I own and as I've never experienced a failure using them, I have confidence that this one will perform in similar fashion. The only way I'll know that is to fly the airplane and see. So in my world, without buying the lightest, torque-E-ist and smallest footprint servos out there,($$), using the one HiTec 6" behind the CG rather than 2 standards in each boom, does save me weight. Total ADW, (all-up dry weight) is my goal. Wing loading should be as light as possible. Balance does play a role in this as adding lead to the nose contradicts my aim. So hanging the one servo further back does present it own unique situation.
I acknowledge that there are better, faster AND lighter solutions to flying the Bobcat. I'd be a fool to think otherwise.
My post is but one of many...
PM