I just don't get it? I made split flaps for my TF At-6. They wouldn't close all the way and the
servo would hum. So I through away the bell cranks and put a servo in each wing. They still
hum. So now I am working on my P-40 and thought I would give it another go. I ensured that
all my hinges were exact, each less than 1/16 from the top of the flap. Each flap moves freely. I
used bell cranks as per plan, hooked up one servo and guess what? They close but the servo
hums. So now I am just pissed. I mean I consider myself to be an above average builder but why
does everyone else seem to make this work? I am thinking of buying a higher torque servo, i.e.,
76 oz. of torque compared with 30 oz. I have now. Think this will stop the humming?


Thanks, SVX

if it is humming after the flaps are down or up it meanstheservo is stilltrying to move but there is no where to go as the flaps have reached their stops.reduce the servo travel in the transmitter or if not an option in the linkages.when does the servo hum?

What kind of servo are you using? Some coreless servos will hum even with a minimum weight load. Try holding up the flap with you finger appling very light upward pressure so there's no weight load on the servo.

please turn the airplane upside down in a cradle and cycle the flaps? still hum? then take off the servo arm from the servos and see that the flap nests in the flap space with out effort , does it stick up just a little? then fix the hinges to allow the flap to lay in the cutout without effort!
yes you can have too much flap volume set in the flap channel on your radio. I think also you do not have enough servo torque even with 2 servos for the flaps, since they are intended to be used at 45degrees of angle at high speeds , I have seen flaps blown back in the airstream because of lack of enough servo torque.
tom

Thanks guys. Well after another afternoon of tinkering I think I might have it. I did a little
adjusting at the horn, took the amount of movement down in my radio etc... I am using a Futaba
S3004 but I think that I will upgrade. The flaps on this thing are huge and I think you’re right
that once airborne they will fold back. I'm still not sold on using bell cranks, however when I am
all finished all the linkages will be hidden and the bottom of the wing will be as smooth as the
top.
Dust

Hey,

Which P-40? Is it the TF? Did they ever make a giant one?

When you have the flaps up fully closed the servos should not hum. You can prevent the servos from having continious load by making sure that the servo horn is parallel with the control rod when the flaps are in the up position. Do the same when with down postion and you will have a strong setup and not eat up your RX batteries. Basically you need to account for the amount of servo travel as the flap's horn travel. Make sence?

Makes sence, and I think that I am pretty close only the bellcarnak is slghtly off 90 degrees (as per plan) I still hate split flaps....need to build a Mustang

I am scratch building the P-40 from a Brian Taylor plan. He does have a giant scale P-40 but not sure if the plan is available for that one.


Thanks guys, Dust