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Prop, Motor, ESC, Battery Combination formula??

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  • Prop, Motor, ESC, Battery Combination formula??

    Hello.

    I am in the process of replicating my son's old Sig Kadet Mark II out of $ Tree foam, as I still have the plans that I built the original Kadet from around 25 years ago!!
    The original balsa and lite ply kit, weighs 5 pounds - according to the specifications that are published by SIG Manufacturing.
    I am hoping that my foam replica will come in at around 3 1/2 - 4 pounds.
    So my question is this: Does anyone know of any "secret recipe" for selecting a prop, motor, esc, battery combination, based on the weight of a plane? The plane will just be used for some slow and relaxing nostalgic flying. It will not need to hover or climb vertically or whatever!!
    Any help with this matter would be helpful!!

    Thank you.

    Jim

  • #2
    The standard "secret recipe" is:
    100 watts per pound

    The closest weight and span ARF similar to the Kadet Mark II that I would recommend utilizing it's power set up is:
    https://www.motionrc.com/collections...0mm-dy8971-pnp
    Warbird Charlie

    ScaleTech OV-10 Bronco; HSD A1 Skyraider(in rehab shop); FlightLine: F7F-2D, P-38 Allied Green, Sea Fury; FMS 1400: P-40B, P-51 Marie, F4U Olathe, F6F, T-28, P-40E, 1500 Razor, 1700 F4U and a Fox glider; Freewing: A-10 Artic Thunder(100+ parts to rise again), A-6, P-51 Iron Ass; VQ: P-39, JU-52; LX PBJ-1(B-25); Dynam: ME-262, FW-190, Waco, Catalina; Phoenix Spitfire; Maxford Antonov AN-2; Starmax L-4 Grasshopper; Eflite 1100 T-28 float; Tech1 P40;

    Comment


    • #3
      Thank you OV10 for sharing your "Secret Recipe" for this endeavour!! That is certainly a big help!! I shall use that info and I also want to thank you for your "research" concerning the Motion R C Dynam Primo V2 power set-up. As an aside, that plane looks like a "fun, sit in my lawn chair, no thought needed - hardly....., lol....., relaxing kind of plane," too. Hmmmmm........, maybe some time down the road, that one may find a home here!!!!!
      This is such a nice website full of such friendly people!!

      Thank you again for your help.

      Jim

      Comment


      • #4
        When I build an ARF, I go to MRC, find an airplane of similar weight, wing span and type, then buy the electronic setup from "spare parts". Usually FMS. This has worked great for me for years. Doc

        Comment


        • #5
          Hello DoctorMike!

          That sounds like some excellent advice also and similar to that offered by OV10 (above)!!
          OV10 recomended using the power system from a Dynam Primo V2 with a 57" wingspan and a weight that I hope will be close to my finished Kadet MarkII. Looks like the "bottom line" here is that if one can find a similar size, weight and type of plane, then there is no need to reinvent the wheel here and just "use what they did." It seems to me that both of you are on the 'same page' with your methods to accomplish this goal!!
          Oh, I have a Dynam Corsair from MRC and I do enjoy it. They are a good place to do business with!!
          So thank you DoctorMike for disseminating the sound advice here! You have a good bedside manner too!! Jim

          Comment


          • #6
            Well, thanks, corsair! Doc

            Comment


            • #7
              There is a handy tool out there in InternetWorld - called eCalc. You will find it at: www.ecalc.ch

              While not specifically built around weight, that is an integral component of its' design determinations. It has proven itself (to me, at least...) to be a decently reliable and very reasonably accurate predictor of motor/ESC/battery performance.

              You can use it for free, but selection of components is intentionally restricted. Buying into the program is cheap and provides a much broader selection - well worth a couple bucks.

              Highly recommended. Check it out.

              Comment


              • #8
                Hello PikeStuff!

                That really looks like a very nice and handy program. Thank you for sending the link to me. I will check it out further and learn how it works, cost and whatever. It will be interesting to see what it can do. Thank you again!!

                Jim

                Comment


                • #9
                  I went to Hobbypartz and to Hobby King and looked at different types of motors. It is very frustrating trying to buy a specific motor. I have a little 650mm rc warplane P51 (budget plane made of balsa). I want to buy something to install and fly as a backup fun plane. Throw in the passenger seat, few lipos and go.


                  Some of the motors do say .32 .40 etc, but not many of them. On the ESC is no problem, follow amps specs, connectors, but w the motors is difficult.

                  Comment


                  • #10
                    I am using the sigplanes page, and more or less following their recommendations.

                    Comparing the airplane I have to a similar one, wingspan, weight, etc. Its just difficult when there are tons of motors online...

                    Comment


                    • #11
                      Originally posted by crankestein View Post
                      I went to Hobbypartz and to Hobby King and looked at different types of motors. It is very frustrating trying to buy a specific motor. I have a little 650mm rc warplane P51 (budget plane made of balsa). I want to buy something to install and fly as a backup fun plane. Throw in the passenger seat, few lipos and go.


                      Some of the motors do say .32 .40 etc, but not many of them. On the ESC is no problem, follow amps specs, connectors, but w the motors is difficult.
                      Look at Heads Up RC I remember them listing motors with specs plus info like what size planes they were best in according to weight and performance. When I first started in electrics they were my go to source for everything.

                      Comment


                      • #12
                        Ryan@Motion/ryram:

                        What have you done?

                        I got about $200.00 in the shopping cart... lol and debating if I click the proceed to checkout.

                        That is one nice website, thank you, makes life so much easier on brushless electric setup to get.

                        If anyone has any coupon codes, let me know.

                        Once again, ty, definitely added to my favorite links.

                        Comment


                        • #13
                          Hello everyone,

                          This post will almost certainly broadcast my lack of knowledge on setting up power systems for electrics, but when you need answers, you go where the experts are. I have almost fished putting together the Motion RC F7F Tigercat. In setting up the electronics, Everything seems to be working as it should, with one small exception: The motors are running backwards. So now I am the proud owner of a fancy new Grumman table fan. Any ideas? Reverse thrust was not a feature on this particular production aircraft....

                          Comment


                          • #14
                            Welcome to the forum Jim!

                            . Go into your servo menu on your transmitter and reverse the direction on channel 3 which is your throttle channel, and that will fix the problem.

                            Roy B.

                            Comment


                            • #15
                              Thanks Roy!

                              I just couldn't imagine it would be that simple.

                              Happy landings,

                              Jim M

                              Comment


                              • #16
                                Originally posted by boomer108 View Post
                                Welcome to the forum Jim!

                                . Go into your servo menu on your transmitter and reverse the direction on channel 3 which is your throttle channel, and that will fix the problem.

                                Roy B.
                                I hate to differ on this, that will only reverse the throttle lever and not the rotation of the motors. To reverse the rotation there are two ways to do this, one is to go into the esc setup and do it with the transmitter or on each motor switch two of the wires around. R
                                AMA 424553

                                Comment


                                • #17
                                  Originally posted by RRHandy View Post

                                  I hate to differ on this, that will only reverse the throttle lever and not the rotation of the motors. To reverse the rotation there are two ways to do this, one is to go into the esc setup and do it with the transmitter or on each motor switch two of the wires around. R
                                  Your are right Handy I was thinking with my head in my ***. Thanks.

                                  Roy B.

                                  Comment


                                  • #18
                                    Kudos on detecting the servos were reversed. There are tons of videos on YT of crash take offs just because the pilot never checked all its controls.


                                    Had a guy the other day at the field, rudder and elevator reversed, and he did not know why the plane plane would not take off and hit the deck.

                                    Comment


                                    • #19
                                      Originally posted by crankestein View Post
                                      Ryan@Motion/ryram:

                                      What have you done?

                                      I got about $200.00 in the shopping cart... lol and debating if I click the proceed to checkout.

                                      That is one nice website, thank you, makes life so much easier on brushless electric setup to get.

                                      If anyone has any coupon codes, let me know.

                                      Once again, ty, definitely added to my favorite links.

                                      I went ahead and clicked proceed to checkout, I feel so dirty, !

                                      Comment


                                      • #20
                                        Back in my earlier RC years, I thought I could just reverse the throttle channel. With the throttle down, I plugged it in...My plane jumped off the table at full throttle!!! Yeah, just reverse 2 wires on the motor. Doc

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