Hi Fred,
I built my XS mono with a regular Rotax 912S and followed the manual
precisely with regard to alignment of the engine to the fuselage. I also
fitted the cowl and spinner with great care. Once flying, I found that I
had at least 1/2 a ball or more of skid in straight and level flight. I
fixed this by adding one washer to the top and bottom engine mounts on
one side. The result, of course, is that the spinner is now out of
alignment with the cowl if you look carefully. I chose to leave it like
that although another option is to correct with a rudder tab. Anyway,
the moral is that even when you try hard it may not come out right.
As far as vertical alignment is concerned, I would be surprised if a 0.2
degree misalignment such as you describe can not be trimmed out with the
normal elevator trim tab operation.
Cheers, John
ORIGINAL MESSAGE
From: Fred Klein <fklein@orcasonline.com>
Subject: Europa-List: propeller shaft alignment w/ cowl
Gentlemen,
As per previous posts, I'm installing a MPEFIed Sube derivative engine
and have made my cowls from Alex Bowman's molds. I'm presently
confronting an issue common to the stock engine installation and am
looking for some counsel.
I've adhered to the build manual w/ regard to P factor offset, and my
prop shaft at the flange is spot on the fuselage centerline; however,
it is about 1/4" high. I'm confident that I can lower it by adjusting
the thin washer count at the intersection of engine mounting frame
with the europa mounting frame.
With the fuselage secure in its cradle and my smart level reading zero
deg. at the port door sill, my reading of the vertical face of the
prop flange is 89.9 to 90.0 deg., depending on the weather, or time of
day (who knows?).
I've noted the caution in the manual to ensure that the plane of the
prop flange is 90 deg. to the waterline. And I'm aware that raising
the prop flange to center it within the cowl prop opening will affect
its verticality...perhaps by as much as 0.2 degrees.
As a matter of superficial aesthetics, I'd like to center everything
up...at the same time, I'm leery of conceding that the plane of the
prop flange will be "off" by this amount...so my questions are:
- Would 0.2 degrees off from true vertical of the plane of the prop
flange be within acceptable limits?, and,
- Would anyone comment on their experiences in addressing this issue?
One of my mantras has been, "I can only strive to achieve
perfection"...that's fine enough overall, but I'm sure there are
individual aspects of our build where perfection is both achievable and
mandatory.
Fred
|