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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
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Senior Member
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.
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Re: KF 5 engine angle
Thanks Jeff, yeah visually looking at the original motor (subaru) I could not detect any angle either.
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Senior Member
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.
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Senior Member
Re: KF 5 engine angle
This might be apples and oranges, but I built my engine mount for my currently flying Model IV. Doing some preliminary research, I was told by a trusted source - the who part escapes me now - that there was no offset. I had the typical right rudder needed effect which rudder trim took care of.
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Re: KF 5 engine angle
It is all good fun and, as I said, just me trying to expound some theory
I understand the P Factor argument and absolutely agree that the best way to deal with this would to be to add rudder trim or at least a trim tab and set it for cruise conditions. Likewise, I get the dynamic thinking and, again, agree this solution would not suit all flight regimes; it would really only suit one combination of RPM and speed (which would account for torque and P Factor) but I would suggest that be set for the cruise where the problem seems to lie.
In that way I agree with the dynamic theory BUT I would suggest the permanent 'offset' would work for a particular RPM and speed mentioned above and postulate the next bit of theory:
Imagine you're in you're taildragger (as all light aircraft should be ) and there is an infinitely long runway. You add your take-off power and then ease forward on the stick. Just for the sake of argument, let's 'freeze' those dynamics at 40kts because things will clearly change as we accelerate but I'm suggesting a solution only for a cruise speed set up, so am taking just one speed on the take-off. As we all know that force we apply to the stick translates to a forward force on the top of the propellor arc which then precesses through 90 degrees to the right (on our 912), causing the aircraft to yaw to the left (just like Wheels cruise set up). At 40kts we'd still need to maintain the same forward force on the stick to keep the tail level and so everything is balanced as we whizz down our infinitely long runway.
Now imagine that we've fitted a device which can push the engine mount bolts forward and move the mount itself. I reckon that if the bottom bolts were pushed out there would come a time when the 'force' of the redefined thrust line and the precession that I've described in my initial post would equal the force of the stick being pushed forward and, correspondingly, reduce the rudder required to counteract it and adding washers to the bottom mounts would have the same affect.
I suppose this would, in addition, always help counter the torque of a clockwise-spinning engine but you'd better be ready with the left rudder when you take off the power to land
Anyway, blah, blah, blah, theory is (sometimes) fun but fit a rudder trim tab
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Re: KF 5 engine angle
Yep, no one engine angle will solve all situations! I'll need to add a rudder trim tab!!
But fwiw I did put a couple degrees left engine angle in while fabricating the yamaha mount... just in case my theory is right, er I mean left...
If that doesn't work maybe ill mount a 912 up there with the yamaha. More power and the counter rotating thing should balance everything out LOL!
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Senior Member
Re: KF 5 engine angle
That was FUN!!! To answer the question, We added the washers (of no effect) to counter the thrust vector (to no effect) on the upper upper left and lower left of the engine (as viewed from aft.) I"m a farmer. lucky I can fly at all.
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