Kitfox Aircraft Stick and Rudder Stein Air Grove Aircraft TCW Technologies Dynon Avionics AeroLED MGL Avionics Leading Edge Airfoils Desser EarthX Batteries Garmin G3X Touch
Results 1 to 10 of 15

Thread: KF 5 engine angle

Hybrid View

Previous Post Previous Post   Next Post Next Post
  1. #1

    Join Date
    Sep 2016
    Location
    Nevis, MN
    Posts
    11

    Default KF 5 engine angle

    Missing in my builders manual is the FWF section, which I assume discusses the engine angle with reference to the firewall.

    I'm mounting the Yamaha RX-1 with a C box, which turns a Left hand prop as does a 2 stroke Rotax.

    Best reference I have so far is zero angle up/down and 4 degrees to the left. Anyone have better info?

    Thanks,
    Brett

  2. #2
    Senior Member jmodguy's Avatar
    Join Date
    Jul 2014
    Location
    Carmel, IN
    Posts
    744

    Default Re: KF 5 engine angle

    The FWF section comes with the FWF kit that you get. I don't recall anything about engine offsets in the Lycoming FWF manual for my Series 5. Doesn't look like there is any offset by looking at it. Best bet is probably to call Kitfox and ask.
    Jeff
    KF 5
    340KF

  3. #3

    Join Date
    Sep 2016
    Location
    Nevis, MN
    Posts
    11

    Default Re: KF 5 engine angle

    Thanks Jeff, yeah visually looking at the original motor (subaru) I could not detect any angle either.

  4. #4
    Senior Member Wheels's Avatar
    Join Date
    Oct 2010
    Location
    Spokane Wa
    Posts
    420

    Default Re: KF 5 engine angle

    My model IV had a heck of a pull to the left so my right foot was falling asleep on long flights. (no trim tab) I added four spacer washers to the engine to offset the pull and had no effect. Maybe that trick works on bigger engines and props but in my experience the 912 is not affected by it.

  5. #5
    Senior Member
    Join Date
    Oct 2016
    Location
    Western Australian
    Posts
    218

    Default Re: KF 5 engine angle

    I'm just musing on theory here and don't know if this will work but where did you add the spacer washers? That's quite a gyroscope on the front of the engine, so I'd have thought you'd need to take into account precession when you're adding a 'force' by offsetting the thrust line.

    You want the engine to stop pulling to the left and so, effectively, you want the thrust to go to the right a bit. Since the 912 rotates clockwise (when viewed from the rear) I think you need to add the washers to the bottom mounts of the engine. This has the effect of 'pushing' at the bottom of the prop but then it precesses through 90 degrees to the left (in the direction on the prop) and so the force acts on the left side of the prop (viewed from behind) and takes away that boot full of right rudder.

    As I say, that's the theory but I'd be very interested to see if it works in practise and I apologise if I'm trying to teach anyone to suck eggs

    (PS: It's freehand circle, so no wonder it didn't join up properly. That and I can't draw)
    Attached Images Attached Images
    Last edited by PaulSS; 09-30-2017 at 10:06 PM.

  6. #6

    Join Date
    Sep 2016
    Location
    Nevis, MN
    Posts
    11

    Default Re: KF 5 engine angle

    Interesting discussion. But may I counter your theory here a little? (Although if that truly is a freehand circle, it is an impressive one indeed, and one that I could never match! So maybe I should keep my mouth shut!

    I agree that applying that force to the bottom would have an instantaneous effect like you diagram, but only in a dynamic sense (during the small amount of time when that force is applied). Except for momentary changes in pitch and yaw, we hopefully won't be changing engine angle "on the fly" (in the air), so I would respectfully argue that this line of reason wouldn't apply.

    I think that an angle adjustment to the right (or left for my ccw yamaha) is sometimes done for two reasons. 1. to vector thrust in the opposite direction that the engine torque is pulling (and creating Wheels right foot to fall asleep). And 2. Maybe more importantly to counter "P factor". Not the one we all get a couple hours into a x-counrty flight, but the one where the descending blade grabs more relative pitch in a high angle climb where the relative wind is at a negative angle to the line of thrust of the engine. That blade pulls harder and yaws the plane the opposite direction.

    Anyhow, all in good fun here! My recollections are from some college engineering and physics classes, so I won't claim there aren't some holes in the ideas described by me here!
    Last edited by MNsnowy1; 10-01-2017 at 10:06 AM.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •