firewall plates and floor stiffness, and Elite mods in gener

[N.Smith]

Hi All

I agree fully with what's been said about extra stiffening being a good idea
in the nose area.

Wayne has very kindly provided all the paperwork I needed to get British
approval to fit his firewall plates, and I've used cherrymax rivets in the
door posts to beef up against the shear problem. I've done the thicker
FUS-452 change, and working on the 2 extra witches hat sections for under
the forward floor as shown in the achieves at the moment.

I guess it's most critical for float operations in choppy water (but since
that's likely to be common ground for me it's worth the bother getting it
right at the build stage).

Thanks to all for the ongoing input to the project - still a long way to go
but at least it looks like an aeroplane now :-)

Nigel
745E



-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com]On Behalf Of
Alan Hepburn
Sent: 05 June 2005 13:11
To: rebel-builders@dcsol.com
Subject: Re: firewall plates and floor stiffness, and Elite mods in
general.


** Check your subject, does it still reflect the message? **

Mike/Wayne:

On the double floor, the front has a lip which is riveted to the firewall
right across, so that will beef up the firewall quite a bit. But to be
safe, add the plate as well by all means. The fore/aft stringers are 5/8"
square - same stuff as you use for the doors.

Jack Wiebe did a neat thing on his Elite. The winshield (FUS-460) shelf
sticks out far further than it needs to, so he bent the front edge back so
it meets the firewall at an angle, and riveted it right acoss the top of the
firewall. That results in a triangular section which adds a lot of strength
for no extra weight. The windshield shelf, BTW, does not support the
windshield - just the front of the fiberglass cuff that goes round the front
of the windshield. If the winshield itself actually went beyond the front
of the firewall (and you could probably install it that way), you'd need
some stainless in that area.

Wayne: I've been told that with the shorter nose on the Elite the rivet
shearing shoul not be as much of a problem as long as I stay out of
whitecaps. Also, the thicker corner wraps should distribute the stress
better. I'll think about it. It would be an easy fix as you say.

I've now dug out the manual, so I can quote part numbers. The side skins
are FUS-425 R&L, the corner wraps which need to be thicker are FUS-10. The
thicker replacements are FUS-452. The forward floor skin to get the cutoff
angle for FUS-5 is FUS-420 (though to be fair to MAM my manual does show the
front of the cutoff as 5/8"). The part where it says to "Drill the four
outside holes at the end of the forward FUS-5 carry through to 7/16" "
refers to the holes for the AN3-20A bolts that hold the bulkhead together,
not the ones for the bolts that secure the gear saddle. These holes are the
ones that I suggest drilling in the rear FUS-5 only, then install the bolts
back-to-front. Much less weakening of a key area this way, especially after
the crush blocks are in place. I believe the crush tubes are supposed to
fit inside FUS-5. In my case, I used crush blocks which are not the full
size of the FUS-5 cross section, but are 5/8" for and aft dimension, and
about 2" laterally. I can't quite remember, but that was probably because
they'd have had to be machined to clear the bolts/nuts.

Mike, on the Elite the instructions get progressively less useful now you
are into the fuselage. You really have to think things through to
completion and see if what it says makes sense. In some details, like
placement of the instrument panel, I doubt if the prototype even looked like
a kit Elite. You'll see that when you try to rig the elevators, for
example. You have to hack about 3 1/2" off the stick to get it to clear the
panel. I think the prototype must have had a Rebel panel, which is much
more angled at the outer ends, so they could get adequate forwasrd stick
before it hit the panel. The top view diagram in my manual even looks like
a Rebel panel. The less dished panel is probably a result of the shorter
nose. I think they built the prototype with a Rebel panel and found they
had very little room for avionics, but maybe I've got it all wrong. Anyway,
something has to change abou these sticks. And once you shorten them, you
don't have enough straight stick to accommodate a grip, so I had them send
me a couple of steel Moose sticks with only one bend completed, then cut the
top ends off and welded them, resulting in just enough straight stick to
take the grip. Another good idea, from Ralph Baker this time, is to lop the
flanges off the right control column bearing CC-38 and replace them with
angle stock, then bolt the angle to the CC-38. That way, you can easily
remove the column later if you wan to do anything major under the panel.
And BTW, don't install the elevator stop CC-67 until final rigging of the
elevators is complete - one of the last things you do. Leave a number of
rivets holes out in this area so you can place CC-67 where you want it and
not be constrained by existing rivet locations. I wasn't smart enough to
think the latter part through, but it would have been easier if I had!
These little changes just go on and on. Like the extra fore and aft ST31s
under the baggage compartment floor, and all the extra structure you need in
the cabin roof if you use the stock flap handle mechanism to stop buckling
in the area of the flap reversal bellcrank.

BTW, anybody who is planning on using Montana 2200 floats - the rear
spreader is a full bay ahead of the MAM 1800 position, so one of two things
has to happen. You either install Montana's rear float attach hard points
at the aft end of the door sill, or provide some fore-aft bracing for the
MAM hard point (details if anybody interested). The Montana hard points
have to be installed during constuction of the floor if you want to avoid
taking the whole floor apart.

Well, that's enough for now.

Al





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