Dual Elevator Servos - Servo Extension Question

[Keith Black]

Regarding placing servos in the stab, the location I was planning on placing my RX (just behind the wing tube) would require about 44 inches of servo extension between the RX and each stab servo. What problems/risks does it present in having extensions this long? 

The only extensions longer than 36" that my local hobby shop sells are 48", but these have a built in filter. I really don't want to use a filter unless absolutely necessary, it will add weight. Is it really necessary to filter runs longer than 36"? What other considerations should be made with long runs?

Any input would be appreciated.

Thanks,
Keith

  ----- Original Message ----- 
  From: Morton 
  To: discussion at nsrca.org 
  Sent: Friday, March 21, 2003 11:35 PM
  Subject: Dual Elevator Servos


  Keith,

  I have been very happy with 2 digital programmable MCV2 micro servos mounted on their sides inside the stab of my Viper 202. I originally had the MCV2 superflat (11 mm) servos which worked fine, but I  liked the quicker speed and power of the micros, and they were still only about 1 oz each. I like the short positive nearly frictionless connection to each elevator half (MK ball bearing clevis). They have held up very well and I had no problem matching the throws. I didn't even use the programming feature, I just plugged each servo into a different channel and mechanically matched them as close as possible. One possible advantage could be that you could have each servo work independently with ailerons if you wanted to. I do that on my fun fly plane and it works great (I am thinking for a multi-purpose AA plane).
  I mount the servos on their sides to a light ply and balsa sandwiched rectangular plate. I use the outer balsa layer to exactly match the curve of the airfoil. I then cut a hollow plywood rectangle that will support the servo in the stab. The width of the plywood rectangle (donut)  is such that 1/2 will be under the balsa stab sheeting and 1/2 is used to support the servo plate, the center is cut out for the servo. I then use a router to create a box for the servo and mounting plate into the foam core before sheeting in the stab. Glue in the plywood rectangle and sheet the stab normally. I then drill a hole in each corner to attach the servo plate. I later added an access hatch  in the bottom of the fuselage to help fish the servo wires and extensions. Send me a message and I will e-mail pictures if you like.

  Ray Morton

  Keith Black wrote:

putting servos in the stab halves
    

This is exactly what I had initially considered on my Aries so my removable
stab would be easier to remove. Essentially they would be like small main
wings.

However all the feedback that I received seemed to indicate that this was a
bad idea due to extra weight, possible differences in throw over time, etc.

I'd like to hear pros and cons from others that use used this technique.

Thanks,
Keith

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.f3a.us/pipermail/nsrca-discussion/attachments/20030403/068c063a/attachment.html