normandouellette
Posts: 319
Joined: 3/12/2007
From: Laval,
QC, CANADA
Status: offline
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Fytrjok,
Flying at 850mb is thinner air and require longer takeoff and landing run. Definitely you have this against you. It would be hard to answer the question you asked before because you're alone up there! You certainly are able to tell us more about it. My opinion is that since you run the engine leaner than at sea level, you can increase the nitro level and fly your B-25 with 12 x 8 MAS 3 blades. You will increase the torque and run your engines with 20% to 30% nitro will enable you to increase fuel consumption and get that extra power on take off. The speed is not your problem since you fly at theorically the same airspeed, but up there means this bird fly at least 20% - 25% faster than at sea level for the same airspeed.."pressurewize". Take off fly is more or less the same. Landing this plane definitely requires better skills because 25% faster on the landing speed is not to be neglected and mistake are increased by the same. I see your runway is long and brakes would be a good idea on this plane at this height
I have seen your pictures and Kudos to you, you built it nice and certainly enjoyed it.
I just spent the last week-end doing maintenance on my B-25..and after 5 flights, fine tuning it and revising all snags I must have spent at least 60 hours. I'm confident it is ready to fly now.
For the noze strut, iI placed a rubber groomet to avoid a knock on the oleo.
It is also a good idea to verify the wood bblocks holding the servos of the ailerons and flaps to acertain that they are solid as mine were broken loose on 1 aileron and 1 flap, I also placed a 2 sided foam tape between the hatch and the servo , just in case.
I agree with you for the B-25, it is a nice model and requires a TLC and lots of maintenance almost like the real thing, it is a machine!
Cheers,
Normand
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All Forums >> RC Airplanes >> ARF or RTF >> RE: Top Flite B-25 ARF (Tecnical, tips, suggestions) 
RE: Top Flite B-25 ARF (Tecnical, tips, sugg... - 
Obviously, since I've flown this plane successfully in Denver we all know the 70's work! I'm running a pair of the OS Surpass FSII's (because I had a pair on hand) and they are certainly adequate with the right props. I'd be willing to bet that I will come to the same conclusions as you did re: optimum proppage. However, altitude effects planes and engines significantly as we all know. What you learned by experience, I am reinforcing. Up here (5280ft.) we generally power our models with engines at the upper range of the recommended specs. Since there was no "range" given for the B25 and you convinced me that 70's were sufficient...that's what I went with. After flying the B25 a 1/2 dozen times or so, I'd say 90fs would be the maximum at this altitude. I'm sure some will engineer a way to do that but not me! The 70's work fine and sound great! The plane flys very scale at 1/2 to 2/3 throttle with the 2 bladed prop. At sea level prop choice is not as critical and flaps are a bit more effective. I love taking my heavy metal to Warbird fly-ins at sea level! It's like flying on a big pillow. I've seen guys whose elevator usage would invert their plane in a heartbeat at altitude. I believe flying up here enhances a pilot's skills, not only in flying but in building light as well. Again, you did a great job developing this B25...if it flys great up here on 70 fs's it'll be magnificent at sea level! I will be testing the MAS 12/8's this weekend. I'm hoping they give me the same pull as the APC 13/8's. I'll also be testing the APC 13/7's and I'll bet these will be the best for this plane...but the 13/8's worked very well.
), any of these are good once set up I'd expect.