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1. 07:02 AM - Note to 650 plans builders Re: top skin dimensions (lwinger)
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| Subject: | Note to 650 plans builders re: top skin dimensions |
I'm at the point of making and installing my top skin. 6-B-21 calls out dimensions
along the center line of the top skin where it intersects with the three
bulkheads. My experience showed those dimensions to be wrong. They were too
close together to maintain parallell bulkheads. Yesterday i followed up with
Travis at ZAC and he was very helpful. The plans show the angle of the middle
bulkhead at 84 degrees, but show no angle on the baggage back and aft bulkheads.
On the other hand, all three have a bottom flange set at 84 degrees, which
would imply that they should stay at that angle. Travis agreed that they were
intended to be parallel, but recognized that the dimensions on the plans for
the top-to-top locations didn't sound right. He physically measured on the
650 made by Zenair that they keep in their shop, and it agreed with the plans.
It turns out that this is because Zenair made the prototype aircraft, put their
top skin on, liked the way it looked and then measured the distance off the
plane, not from predetermined calculations. In reality, the baggage back bulkhead
on the Zenair 650 sits at 82 degrees --- and everything still works! So
the distances on the plans will produce a back-tipping baggage back bulkhead.
In CAD, Travis calculated that the dimensions from aft to middle should be
646.5mm and from middle to baggage back should be 875.2mm. That should maintain
84 degrees on all bulkheads. Having said that, he indicated that all that
really matters is that the top skin fits and looks nice, and that the baggage
back bulkhead is somewhere near 84 degrees. Obviously the point in space created
by the front edge of the top skin as it relates to the canopy (installed later)
is not hyper critical.
--------
Larry Winger
Tustin, CA
Plans building 601XL/650 with Corvair
Control surfaces and wings complete
Fuselage 98% complete
www.mykitlog.com/lwinger
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=227073#227073
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