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  1. Aeroplayin

    Build log: Redwing RC 76" MXS-R STOJANOVSKI SCHEME

    Sure.... the way to start is the weight of the plane, then we'll add the battery and motor weight, and figure out the power you personally can settle for. I'm not familiar with the DM4330-400Kv on 6S, but I know the Motrolfly DM4330 with other winds well. Are you saying that you have 6S...
  2. Aeroplayin

    Extreme Flight 76/83" MXS

    Thanks Ryan. The pull-out really helps me make some comparisons. That pull out was just about the same as my 10S setup with the 21x10 Falcon electric beech (E-1) and the A60-7S on the 78 Extra gas version converted to electric, so about 13 pounds 10 ounces. But I'm getting a little more...
  3. Aeroplayin

    Extreme Flight 76/83" MXS

    That sucks, and I'll have to remember that if I ever think about doing it again.
  4. Aeroplayin

    Build log: Redwing RC 76" MXS-R STOJANOVSKI SCHEME

    Sorry, but I followed the 'mentioned' link from an email and though it was for the 76/83 EF MXS... so the thrust to weight, and Watts per pound, were based on the projected AUW of that plane with the motor and battery weight I mentioned. I don't know what the weight will be for this plane, but...
  5. Aeroplayin

    Build log: Redwing RC 76" MXS-R STOJANOVSKI SCHEME

    If it's a real 270Kv, then at 3.7 volts per cell, the 8S setup seems to be a decent match. Sometimes they just round up or down the value, so running it unrestricted (prop off) for a few seconds at WOT with a Castle log on it will give you a better Kv to deal with. With a 21x10 prop on 8S...
  6. Aeroplayin

    Extreme Flight 76/83" MXS

    Thanks, Ryan. Nice write-up. For pull-out, you may want to try the Vess 21A if the engine can swing a little more D. The weight and the higher D/P ratio will help, especially if the engine can spin it up a little faster and stay running. The problem will then remain top end speed, but that...
  7. Aeroplayin

    Extreme Flight 76/83" MXS

    Can you elaborate on "plenty of power"? I hear that a lot and it has not always worked out for me.
  8. Aeroplayin

    Extreme Flight 76/83" MXS

    I know some guys like Matt have not had good luck with Greyhound, but I sent three planes in the same BIG box along with other goodies to a friend in TN for $63 which included $300 in insurance, but you have to go to the terminal to drop off and pick up. The tracking was strange, and it may not...
  9. Aeroplayin

    Extreme Flight 76/83" MXS

    BTW Matt... your A60-8S with the 21x10 electric beech Falcon will easily do 2.5 lb-ft on 12S because it only takes 6665 RPMs, and we've seen as much as 6680 after the high voltage is bled off the batts. It's about 3.2 HP. So as far as measured RPMs in a static position, all of these engines...
  10. Aeroplayin

    Extreme Flight 76/83" MXS

    Pitch speed is the velocity the plane would travel in a solid medium, like a screw through wood per each revolution, taking into consideration the pitch angle and RPMs. MPH = (((Pitch in Inches / 12 inches) x RPMs) x 60 seconds) / 5280 ft Also, power in torque is the factor that typically...
  11. Aeroplayin

    Extreme Flight 76/83" MXS

    What I mean by "But the AUW has to be right too or the power is meaningless." is that I really don't want to go to silly power levels with the 50cc power options and give up the flight characteristics of a perfect cube loading (IMO) that I love about the other EF planes I have.
  12. Aeroplayin

    Extreme Flight 76/83" MXS

    Something important to consider. I don't know the weights of the 20 and 21 Mejzlik and Falcon CG props but I'm going to use the 103g I have for the 20x10 PJA, which is probably off, but.... A 20x7 Mejzlik requires 3275 Watts-out at 9100 RPMs, which is 4.4 HP. I don't believe it either...
  13. Aeroplayin

    Extreme Flight 76/83" MXS

    I don't have the plane (yet) but with Matt and Ryan contributing some time to put some numbers together, we have a pretty good approximation for wing loading and cube loading. For the e-version weights and the wing specs, I would come in at 12.88 pounds with the A60-8S and 2x 6S 3300's...
  14. Aeroplayin

    Need Assistance In Motor Selection Please!

    I think the 6.6:1 ratio for 2800 is actually 368, so to get the Kv of the motor that will deliver 425 Kv at the prop, you need to multiply by 7.6... thus 2975 Kv. So this is how you can figure out the Kv you need at the prop, then do the math to figure out what real motor Kv you need or which...
  15. Aeroplayin

    Need Assistance In Motor Selection Please!

    To help things along, Frank, here is the online calculator I programmed that Gary was referring to. http://rcwebclub.com/PropEngine.aspx If to calculate the gear ratio into the Kv, it will help you. For eample... put 16 in the prop diameter field, 8 in the pitch field, the geared Kv (or for...
  16. Aeroplayin

    Need Assistance In Motor Selection Please!

    My suggestion would be to do the calculations or ask someone who understand the difference between geared and direct drive. Since two of your criteria are to fly for 30 minutes and achieve 40 mph, geared motors give you the ability to gain a lot more efficiency out of bigger props. If you ever...
  17. Aeroplayin

    Need Assistance In Motor Selection Please!

    That's the motor I would have suggested if I were going to start suggesting motors. Motrolfly is one of my two favorite motor brands because they are light, run cool, run hard, and run long. And of course, there's Ken's support. If Ken could wind a custom 650 for a reasonable price, it would...
  18. Aeroplayin

    Need Assistance In Motor Selection Please!

    Yep, and if we're not getting 250 Watts per pound and about 1.8:1 thrust to weight, we're not happy. But for scale planes and park flying, a lot less power is needed. If I remember correctly, a full scale plane, including the huge 747, operates at a 1:3 thrust to weight. So for a park flyer...
  19. Aeroplayin

    Need Assistance In Motor Selection Please!

    Although I've never tried it personally, I'm convinced that as long as you have a runway long enough to achieve takeoff speed, you can probably get an airplane in the air with a 1:3 thrust to weight. The values in grams after the motor is probably the motor weight, and thrust will typically be...
  20. Aeroplayin

    Need Assistance In Motor Selection Please!

    Funny stuff... WCL is 2.8. The 3D planes we're flying are all between 7.5 and 9.0. :cool: Anyway... I think I can scale down the math, so here we go. At 16 oz, we can start as low as a 50% thrust to weight ratio, and a 100% would be better, but more than your application requires. This means...
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