The Murphy Builders Site

Hi everyone,

I bought a partially completed Rebel kit 2 years ago and am just now
finally able to work on it. The previous builder built the fuselage per
plans, but apparently "routinely" disconnected the aft fuselage section
(Bulkhead A rearward) from the forward cabin for space reasons. When I
first sent pictures 2 years ago to Wayne for his opinion (sorry I clogged
your inbox Wayne!) he astutely remarked that the two halves may be
difficult to mate.

Well, Wayne was right (no surprise there!). Last night I finally tried to
mate bulkhead A with a near-complete forward cabin and the roof and side
skins matched perfectly....but the entire row of rivet holes in FUS-39
however, was off by about 4 mm. I'm perplexed at how this might have
occurred given that FUS-39 is followed immediately by both FUS-24s. I can
only imagine the former builder left the two "disconnected" for too much of
the cabin build sequence, messed up the positioning of F and door sill
bulkheads, and riveted FUS-39 to these two without cross referencing to
bulkhead A.

Right or wrong (and in part to simply kick-start myself into the build) I
decided the best/easiest fix was to replace FUS-39 entirely (cabin floor
only had channels...no second skin). I didn't have the 5/16 edge distance
typically prescribed in the plans to salvage FUS-39. So last night I got
underneath the plane and drilled out about 60 rivets and popped the skin
off (1.5 hours work). While I wait for some 0.020 sheet to arrive, I
thought I'd get all your opinions on what I've done, and plan to do next...

1) cut an approximate size replacement skin.
2) back-drill the two rows of rivets (connecting to bulkhead F and door
sill bulkhead in the cabin) through original sheet into new skin, cleco-ing
all the way.
3) tilt back fuselage (cabin and tail-cone still connected) so bulkhead A,
F and quarter-bulkhead all lay flat on the table and (selectively) cleco
the new skin through cabin bulkheads and table.
4) Back-drill through bulkhead A through new skin into table.
5) level fuselage for riveting
5) Trim and finish-prep skin.
6) Rivet in place

The only drawback I can see to my plan is the fact that I am relying on the
existing connection between FUS-24 and top skin to dictate the relative
angle between the tail cone and cabin. This seems counter-intuitive to me,
knowing that FUS-39 and FUS-24 were the first skins to attach to the
tailcone in the build sequence. How do I know the angle is correct? Is it
sufficient to ensure all bulkheads are 90 degrees to one another?

Does anyone think I should finish off the tailcone before attaching? The
aft assembly (FUS-29s, FUS-30, horizontal bulkhead,etc) all still need to
be done. I'm wondering if it might be easier to finish off before
attaching to cabin.

I've got pictures if anyone's interested.

Thanks for your help!

Rob
Rebel 786



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Hi Rob
Your plan sounds reasonable -- but maybe I'm over simplifying your problem
to only being misaligned holes in the bottom skin Fus-39, and replacing
that is pretty simple. Use of whatever holes are correct in the removed
Fus-39 is good. It will be a little difficult to match drill out through
existing bulkhead holes that are already #30 without widening them. Maybe
others have tips on this.

As for getting the right angle between the two fuselage sections, the most
straight forward answer is to see if things line up per MAM Figure 12.10.2
and the associated directions. I don't understand from your description
that Fus-39 is a factor in this angle though. As per the the MAM 12.10
directions, the angle is defined by the bottom holes in Fus-26 lining up
with holes in the uprights (Fus-4). Granted, those directions are based on
a different build sequence than you have, but I'd try to reverse engineer
what you have to make sure it agrees with those directions. If helpful,
some of my pictures during that phase are at
http://mae.ucdavis.edu/ransom/Murphy/2007/0705/

As for the tailcone finishing (Fus 29, 30, doubler, etc), I see no problem
whether it is done before or after joining the front fuse sections.
However, I would think it easier to do beforehand because the whole aft
tail section can be flat on the table (assuring it is straight) without the
front cabin section sticking up high with required blocking to support it's
weight.

Hope this helps,
-Ben/ 496R

On 12/4/2008 5:15 PM, schaumr wrote to rebel-builders:

Hi everyone,

I bought a partially completed Rebel kit 2 years ago and am just now
finally able to work on it. The previous builder built the fuselage per
plans, but apparently "routinely" disconnected the aft fuselage section
(Bulkhead A rearward) from the forward cabin for space reasons. When I
first sent pictures 2 years ago to Wayne for his opinion (sorry I clogged
your inbox Wayne!) he astutely remarked that the two halves may be
difficult to mate.

Well, Wayne was right (no surprise there!). Last night I finally tried to
mate bulkhead A with a near-complete forward cabin and the roof and side
skins matched perfectly....but the entire row of rivet holes in FUS-39
however, was off by about 4 mm. I'm perplexed at how this might have
occurred given that FUS-39 is followed immediately by both FUS-24s. I can
only imagine the former builder left the two "disconnected" for too much of
the cabin build sequence, messed up the positioning of F and door sill
bulkheads, and riveted FUS-39 to these two without cross referencing to
bulkhead A.

Right or wrong (and in part to simply kick-start myself into the build) I
decided the best/easiest fix was to replace FUS-39 entirely (cabin floor
only had channels...no second skin). I didn't have the 5/16 edge distance
typically prescribed in the plans to salvage FUS-39. So last night I got
underneath the plane and drilled out about 60 rivets and popped the skin
off (1.5 hours work). While I wait for some 0.020 sheet to arrive, I
thought I'd get all your opinions on what I've done, and plan to do next...

1) cut an approximate size replacement skin.
2) back-drill the two rows of rivets (connecting to bulkhead F and door
sill bulkhead in the cabin) through original sheet into new skin, cleco-ing
all the way.
3) tilt back fuselage (cabin and tail-cone still connected) so bulkhead A,
F and quarter-bulkhead all lay flat on the table and (selectively) cleco
the new skin through cabin bulkheads and table.
4) Back-drill through bulkhead A through new skin into table.
5) level fuselage for riveting
5) Trim and finish-prep skin.
6) Rivet in place

The only drawback I can see to my plan is the fact that I am relying on the
existing connection between FUS-24 and top skin to dictate the relative
angle between the tail cone and cabin. This seems counter-intuitive to me,
knowing that FUS-39 and FUS-24 were the first skins to attach to the
tailcone in the build sequence. How do I know the angle is correct? Is it
sufficient to ensure all bulkheads are 90 degrees to one another?

Does anyone think I should finish off the tailcone before attaching? The
aft assembly (FUS-29s, FUS-30, horizontal bulkhead,etc) all still need to
be done. I'm wondering if it might be easier to finish off before
attaching to cabin.

I've got pictures if anyone's interested.

Thanks for your help!

Rob
Rebel 786

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