The Murphy Builders Site

Something doesn't make sense there...I've never had one with a gap. Take a
measurement from the inside fin post to the inside front attach along the
lower rib channel of the fin. I'll try to do the same with one I have here
tomorrow.

Wayne

----- Original Message -----
From: <bransom@dcsol.com>
To: <rebel-builders@dcsol.com>
Sent: Sunday, November 05, 2006 10:22 PM
Subject: [rebel-builders] verticle fin to Fus-43 problem

I found trouble when hoping to mate the verticle fin to Fus-31 (horizontal
bulkhead) and Fus-43. MAM is missing here IMO, in that it says to keep
Fus-43 flat with the use of a piece of plywood -- no problem there -- but
doesn't say anything about getting the forward/backward angle of Fus-43
correct. Result is that the rear flange of Fus-31 doesn't reach the fin
post, and in addition, the fin front bracket doesn't fit flat on Fus-43.
Rear picture: http://mae.ucdavis.edu/ransom/Murphy/10 ... _0510c.JPG
Front picture: http://mae.ucdavis.edu/ransom/Murphy/10 ... _0509c.JPG

On mine, this can be corrected by angling Fus 43 just enough so that the
top moves only 1/4", maybe 5/16" forward. That's a pretty small distance,
so the angle -- or really, the distance back to the top of Fus-43 --
should
have been measured. Unfortunately, I will need to replace the Fus-29
skins
to re-do this. Frustrating.

Anyone else have similar problems here? Did I miss something obvious?
-Ben/ 496R



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Ben,
It looks like you just need to angle the fin back a little and everything
will line up. I don't see the Fus-30 tailwrap in your pictures. That should
part of the joining process. I Did it while everything was still clecoed to
the table. With the Fus 30 clecoed down in a few places on the bottom you
can pull the sides up around the fin spar and horizontal bulkhead.
Jesse

From: bransom@dcsol.com
Reply-To: <rebel-builders@dcsol.com>
To: rebel-builders@dcsol.com
Subject: [rebel-builders] verticle fin to Fus-43 problem
Date: Sun, 05 Nov 2006 18:22:25 -0900

I found trouble when hoping to mate the verticle fin to Fus-31 (horizontal
bulkhead) and Fus-43. MAM is missing here IMO, in that it says to keep
Fus-43 flat with the use of a piece of plywood -- no problem there -- but
doesn't say anything about getting the forward/backward angle of Fus-43
correct. Result is that the rear flange of Fus-31 doesn't reach the fin
post, and in addition, the fin front bracket doesn't fit flat on Fus-43.
Rear picture: http://mae.ucdavis.edu/ransom/Murphy/10 ... _0510c.JPG
Front picture: http://mae.ucdavis.edu/ransom/Murphy/10 ... _0509c.JPG

On mine, this can be corrected by angling Fus 43 just enough so that the
top moves only 1/4", maybe 5/16" forward. That's a pretty small distance,
so the angle -- or really, the distance back to the top of Fus-43 -- should
have been measured. Unfortunately, I will need to replace the Fus-29 skins
to re-do this. Frustrating.

Anyone else have similar problems here? Did I miss something obvious?
-Ben/ 496R



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FWIW I recall bending the forward brackets a bit on the fin and the
stabilizers to match the bulkhead. You can get a bit of bulkhead
movement (at the top) by drawing the rivet holes out to 1/8 (from #40)
with a small round file of course. Think I might even have filed a few
out to 5/32". I don't really understand why you'd need to replace
Fus-29 bottom skin. I'd consider a spacer on the rear or front of the
horizontal bulkhead before anything that drastic.

Other thoughts that you are probably aware of:
I ended up removing the top skin forward of the fin until after the
controls were installed. Just don't crawl back there with weight on the
tailwheel unless you support under the rear fuselage.

I also put a piece of stringer material side to side on the bottom of
the horizontal bulkhead just behind the 3 bellcrank cutouts to minimize
flexing of the horizontal bulkhead and binding of the bellcrank in its
delrin bearings. The elevator cables pull down on the bellcrank.

Guys have been talking about zero fin offset lately. I'd still put about
a 1/2" offset in though if you know which way your prop is going to turn.

And then there is the tailpost to horizontal bulkhead doubler bulletin
when you get this sorted out.

Ken

bransom@dcsol.com wrote:

I found trouble when hoping to mate the verticle fin to Fus-31 (horizontal
bulkhead) and Fus-43. MAM is missing here IMO, in that it says to keep
Fus-43 flat with the use of a piece of plywood -- no problem there -- but
doesn't say anything about getting the forward/backward angle of Fus-43
correct. Result is that the rear flange of Fus-31 doesn't reach the fin
post, and in addition, the fin front bracket doesn't fit flat on Fus-43.
Rear picture: http://mae.ucdavis.edu/ransom/Murphy/10 ... _0510c.JPG
Front picture: http://mae.ucdavis.edu/ransom/Murphy/10 ... _0509c.JPG

On mine, this can be corrected by angling Fus 43 just enough so that the
top moves only 1/4", maybe 5/16" forward. That's a pretty small distance,
so the angle -- or really, the distance back to the top of Fus-43 -- should
have been measured. Unfortunately, I will need to replace the Fus-29 skins
to re-do this. Frustrating.

Anyone else have similar problems here? Did I miss something obvious?
-Ben/ 496R

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Thanks for the input. Wayne, the measurement on mine is 22" from the line
8" up on the fin post to the middle front face of the bracket that ties to
Fus-43. Measurement is more like 22 1/4" if going to the top of the
bracket (right under the fin leading edge). I know this 1/4" variation
sounds fudgy but the measurement line is a diagonal and going to the top of
that bracket instead of the center or bottom makes makes a difference. I
also measured the distance up from the bottom of the tail post to the
bottom "rib" of the fin, and that matches plans exactly. (I didn't make
the tail pieces, so if I could blame the previous owner for something, that
would be a little easier (kidding), but no, everything I've checked matches
MAM.

Ken, as you suggest, I think I probably won't have to replace the bottom
Fus-29. And in fact, I'm toying with the possibility that I can still use
the same top Fus-29 if the top of the Fus-43 bulkhead can be moved forward
enf to trim off the bad holes in Fus-29 and leave edge distance for correct
holes. I kind of doubt this possiblity tho. Also, yes, I've been known to
nudge a #40 hole into a #30 and better location myself -- a useful trick.

I doodled a quick bmp picture last night to help show what I think is going
on here. Maybe I can make <a
href=http://mae.ucdavis.edu/ransom/Murphy/10 ... em.JPG>web
links</a> here.
Angling the top half of Fus-43 forward approx 1/4" (measured at the top) is
enough to take out the 1/2" gap at the fin tail post.

One more thing, is ~ 1/16"- 1/8" gap about right for the space between the
fuselage skin (Fus-29) and the bottom of the verticle fin leading edge?
-Ben




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