[rebel-builders] Tail-spring bulkhead - FUS-30

[Ron Shannon]

Ben,

I did my FUS-30 doubler a couple of months ago, adding it on top of an
existing one. I know you had a nice wood jig for forming the bottom tail
bends. Once you have the tail bend in place, use of a plastic or Lexan
template gets very difficult, both on the existing fuse and on the newly
formed doubler piece.

I tried a bunch of methods, between my two attempts. One that didn't
work well was back drilling some of the middle (vertically) holes with a
long bit from across the fuse. It's hard to get straight (non-elongated)
holes if you come at the back drilling from any angle at all.

My recommendations:

1) Be sure that the new piece is solidly clamped on at the tail, and
bolted at the tailspring hole, through all maneuvers. Depending on how
big a doubler you're intending to make, I'd also recommend fashioning a
carpeted wedge of some sort to keep the forward bottom edge of the
doubler up tight on the fuse whenever marking and drilling. It's a lot
of work to reset this stuff over and over (see below) but worth it. My
doubler was intentionally oversize by about 1/4" (aft and top edges) to
3/4" (forward edges) until almost the very end. Finishing & sanding all
the edges was the last thing to do before the great epoxy chromate &
rivet-it-up adventure.

2) Work your way marking and drilling holes up one side at a time,
horizontally, i.e., across horizontal positions of rivets. You can keep
the existing bulkhead attached by clecoing a few places from the inside,
which will allow the new piece to get up close.

3) For the first 5-6 rows (horizontal) which are at the tight turn at
the bottom, use back markers inserted into the existing holes. As you
may know, those are small pins with points on them. You lay the doubler
over them, whack them with a mallet to make indentations on the inside
of the doubler, then take it off, drill, reattach (clamp, bolt & cleco),
mark the next couple, and repeat until you're blue in the face. :-)

4) After getting up about 5-6 "rows" I found it was most productive to
use strap locators, sliding them down between the fuse and doubler to
engage an existing hole, then just drill away from the outside. They
work very well, and at that point the pace can really pick up. Even so,
I had a few rivet holes in the existing fuse that got a little enlarged
here and there, so I up-sized a few rivets from 1/8" to 5/32", trying to
keep the patterns pleasing to the eye! :-)

BTW, I cut my elevator tube holes in the existing fuse piece before
starting the doubler. I thought it would be unduly difficult to cut them
through two layers at once. Then when I had the doubler drilled and
ready to go, I marked the elevator tube holes onto it from the inside. I
haven't yet riveted the doubler around the elevator tube holes -- that
will wait until after I fit the tube fairings.

The FUS-30 doubler took me a long time to get right -- the second time!
There are numerous annotated pictures of my progress in the Fuselage
section of the Gallery on my site (below). I'm pleased with the way it
came out. (http://tinyurl.com/ya7pbu) Not perfect, but pretty good, and
plenty strong. Let me know here, or off list or by phone if I can help
any other way. Good luck.

Ron
http://n254mr.com



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[Wayne G. O'Shea]

Ron....when you get the push pull tubes in and you know they clear the holes
(they will probably will need some minor opening..they always do) remember
to go back and drill around the oval cutout and rivet the two Fus-30's
together there. If it was me I'd have a lot more rivets in the flat surfaces
of that doubling Fus-30 as well, to really make them work as one unit.

Wayne

----- Original Message -----
From: "Ron Shannon" <rshannon@cruzcom.com>
To: <rebel-builders@dcsol.com>
Sent: Friday, January 26, 2007 12:17 AM
Subject: Re: [rebel-builders] Tail-spring bulkhead - FUS-30

Ben,

I did my FUS-30 doubler a couple of months ago, adding it on top of an
existing one. I know you had a nice wood jig for forming the bottom tail
bends. Once you have the tail bend in place, use of a plastic or Lexan
template gets very difficult, both on the existing fuse and on the newly
formed doubler piece.

I tried a bunch of methods, between my two attempts. One that didn't
work well was back drilling some of the middle (vertically) holes with a
long bit from across the fuse. It's hard to get straight (non-elongated)
holes if you come at the back drilling from any angle at all.

My recommendations:

1) Be sure that the new piece is solidly clamped on at the tail, and
bolted at the tailspring hole, through all maneuvers. Depending on how
big a doubler you're intending to make, I'd also recommend fashioning a
carpeted wedge of some sort to keep the forward bottom edge of the
doubler up tight on the fuse whenever marking and drilling. It's a lot
of work to reset this stuff over and over (see below) but worth it. My
doubler was intentionally oversize by about 1/4" (aft and top edges) to
3/4" (forward edges) until almost the very end. Finishing & sanding all
the edges was the last thing to do before the great epoxy chromate &
rivet-it-up adventure.

2) Work your way marking and drilling holes up one side at a time,
horizontally, i.e., across horizontal positions of rivets. You can keep
the existing bulkhead attached by clecoing a few places from the inside,
which will allow the new piece to get up close.

3) For the first 5-6 rows (horizontal) which are at the tight turn at
the bottom, use back markers inserted into the existing holes. As you
may know, those are small pins with points on them. You lay the doubler
over them, whack them with a mallet to make indentations on the inside
of the doubler, then take it off, drill, reattach (clamp, bolt & cleco),
mark the next couple, and repeat until you're blue in the face. :-)

4) After getting up about 5-6 "rows" I found it was most productive to
use strap locators, sliding them down between the fuse and doubler to
engage an existing hole, then just drill away from the outside. They
work very well, and at that point the pace can really pick up. Even so,
I had a few rivet holes in the existing fuse that got a little enlarged
here and there, so I up-sized a few rivets from 1/8" to 5/32", trying to
keep the patterns pleasing to the eye! :-)

BTW, I cut my elevator tube holes in the existing fuse piece before
starting the doubler. I thought it would be unduly difficult to cut them
through two layers at once. Then when I had the doubler drilled and
ready to go, I marked the elevator tube holes onto it from the inside. I
haven't yet riveted the doubler around the elevator tube holes -- that
will wait until after I fit the tube fairings.

The FUS-30 doubler took me a long time to get right -- the second time!
There are numerous annotated pictures of my progress in the Fuselage
section of the Gallery on my site (below). I'm pleased with the way it
came out. (http://tinyurl.com/ya7pbu) Not perfect, but pretty good, and
plenty strong. Let me know here, or off list or by phone if I can help
any other way. Good luck.

Ron
http://n254mr.com



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[bransom]

Ron,
Thanks for the detailed tips on this. My only fuss now is a matter of
patience -- I had visions of actually completing Fus-49 (last week), but I
guess I'll hold on that and get into fitting up the Fus-30 doubler. I'll
even weigh the possibility of doing the elevator tube holes too. This
section is much more challenging than I expected, but I guess now after
seeing the tips from you and others it doesn't seem too bad. By now I have
a LOT that is still just clecoed, including the fuselage sub-floor, inside
corner wraps, Fus-29s, etc. I'm getting a little thristy for actually
putting in a frickin rivet and calling something complete. :) Looking
forward to a warm wknd and not too many obligations, so I might get good
progress this wknd.
-Ben

Ben,

I did my FUS-30 doubler a couple of months ago, adding it on top of an
existing one. I know you had a nice wood jig for forming the bottom tail
bends. Once you have the tail bend in place, use of a plastic or Lexan
template gets very difficult, both on the existing fuse and on the newly
formed doubler piece.

I tried a bunch of methods, between my two attempts. One that didn't
work well was back drilling some of the middle (vertically) holes with a
long bit from across the fuse. It's hard to get straight (non-elongated)
holes if you come at the back drilling from any angle at all.

My recommendations:

1) Be sure that the new piece is solidly clamped on at the tail, and
bolted at the tailspring hole, through all maneuvers. Depending on how
big a doubler you're intending to make, I'd also recommend fashioning a
carpeted wedge of some sort to keep the forward bottom edge of the
doubler up tight on the fuse whenever marking and drilling. It's a lot
of work to reset this stuff over and over (see below) but worth it. My
doubler was intentionally oversize by about 1/4" (aft and top edges) to
3/4" (forward edges) until almost the very end. Finishing & sanding all
the edges was the last thing to do before the great epoxy chromate &
rivet-it-up adventure.

2) Work your way marking and drilling holes up one side at a time,
horizontally, i.e., across horizontal positions of rivets. You can keep
the existing bulkhead attached by clecoing a few places from the inside,
which will allow the new piece to get up close.

3) For the first 5-6 rows (horizontal) which are at the tight turn at
the bottom, use back markers inserted into the existing holes. As you
may know, those are small pins with points on them. You lay the doubler
over them, whack them with a mallet to make indentations on the inside
of the doubler, then take it off, drill, reattach (clamp, bolt & cleco),
mark the next couple, and repeat until you're blue in the face. :-)

4) After getting up about 5-6 "rows" I found it was most productive to
use strap locators, sliding them down between the fuse and doubler to
engage an existing hole, then just drill away from the outside. They
work very well, and at that point the pace can really pick up. Even so,
I had a few rivet holes in the existing fuse that got a little enlarged
here and there, so I up-sized a few rivets from 1/8" to 5/32", trying to
keep the patterns pleasing to the eye! :-)

BTW, I cut my elevator tube holes in the existing fuse piece before
starting the doubler. I thought it would be unduly difficult to cut them
through two layers at once. Then when I had the doubler drilled and
ready to go, I marked the elevator tube holes onto it from the inside. I
haven't yet riveted the doubler around the elevator tube holes -- that
will wait until after I fit the tube fairings.

The FUS-30 doubler took me a long time to get right -- the second time!
There are numerous annotated pictures of my progress in the Fuselage
section of the Gallery on my site (below). I'm pleased with the way it
came out. (http://tinyurl.com/ya7pbu) Not perfect, but pretty good, and
plenty strong. Let me know here, or off list or by phone if I can help
any other way. Good luck.

Ron
http://n254mr.com

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[Ron Shannon]

Wayne, as I described, the elevator tube holes were cut on the
underlying original fuse skin first, with the tubes & elevators in
place, so they should be fine.

I copied the rivet pattern from the picture of this design of FUS-30
doubler in the archives that Bob P. was recommending, particularly the
new "X" rivet pattern in the aft portion, and tying into several rivets
of FUS-89. It's quite solidly tied to everything, but as you suggest,
perhaps it could use even more.


Wayne G. O'Shea wrote:

Ron....when you get the push pull tubes in and you know they clear the holes
(they will probably will need some minor opening..they always do) remember
to go back and drill around the oval cutout and rivet the two Fus-30's
together there. If it was me I'd have a lot more rivets in the flat surfaces
of that doubling Fus-30 as well, to really make them work as one unit.

Wayne

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[Ron Shannon]

Ben,

I know what you mean. My build was complicated "just a little bit" when
I decided to change the tailspring from the stock MAM "club" to a
modified Champ spring, because....

The tailspring clamp spacers have to set the correct height for the new,
"must have" tailspring, the spacers set the height of the TS-3, which
has to be at its "final" height to get correct lengths for the
stabilizer tubes, which have to be right in order to mount the stabs and
actually have working elevators to check deflections when cutting the
elevator tube holes, and....

I can verify it's not real efficient to do all that in one order first
(like, per the manual) then have to redo most of it again in a different
order, for a new tailspring, all while coordinating the FUS-30 doubler
job. I ended up making at least 3 sets of stabilizer tubes, or was it 4?
I lost track. I'm pretty sure the last set is the best though, so far. :-)

Ron


bransom@dcsol.com wrote:
...

By now I have
a LOT that is still just clecoed, including the fuselage sub-floor, inside
corner wraps, Fus-29s, etc. I'm getting a little thristy for actually
putting in a frickin rivet and calling something complete. :)

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