The Murphy Builders Site

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From: "Morehouse, Daniel G" <DMorehouse@peacehealth.org>
To: "'murphy-rebel@dcsol.com'" <murphy-rebel@dcsol.com>
Subject: strengthening cabin/firewall
Date: Sun, 22 Nov 1998 09:45:26 -0800
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Hello!

FYI: I spoke with ... gosh forgot his name... at Murphy. He's the very
pleasant gentleman who has just recently replaced Dennis. Anyway it was
about strengthening the doorposts, etc. that we have been discussing a lot
recently on the board. Grant! That's his name. Now he said that he couldn't
condone all the reinforcements that have been suggested by the builders. He
felt that the likely reason for structural failure was hard landings. Also,
by reinforcing one would change the stress load in the plane causing failure
someplace else.


Happy building,
Dan
R280




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From: "Alister Yeoman" <yeoman@voyager.co.nz>
To: "Murphy Rebel" <murphy-rebel@dcsol.com>
Subject: Re: strengthening cabin/firewall
Date: Mon, 23 Nov 1998 08:32:45 +1300
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Hi Dan,

I think thats a pretty bold statement by Grant, ( I guess you are talking
about), I have only done 40 hrs in my Rebel with NO hard landings, But it
has been used on uneven surfaces ( that why I bought the Rebel, its
supposed to be an off airfield machine!) There is definately working
(smoking ) of the rivets up the door post which I am repairing at the
moment. In my opinion there are definately issues in the Spring gear
attachment and load distribution that need working through.

Alister


----------

From: Morehouse, Daniel G <DMorehouse@peacehealth.org>
To: 'murphy-rebel@dcsol.com'
Subject: strengthening cabin/firewall
Date: Monday, November 23, 1998 6:45 AM

Hello!

FYI: I spoke with ... gosh forgot his name... at Murphy. He's the very
pleasant gentleman who has just recently replaced Dennis. Anyway it was
about strengthening the doorposts, etc. that we have been discussing a

lot

recently on the board. Grant! That's his name. Now he said that he

couldn't

condone all the reinforcements that have been suggested by the builders.

He

felt that the likely reason for structural failure was hard landings.

Also,

by reinforcing one would change the stress load in the plane causing

failure

someplace else.


Happy building,
Dan
R280

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To: " (Murphy Rebel)" <murphy-rebel@dcsol.com>
Subject: Re: strengthening cabin/firewall
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Kind of puzzles me with the that thinking. What you seem to be saying is
that
it is okay to bend parts on hard landings. I remember one of the factory
Rebels
having bent skins just aft of the door openings. They beefed that area up
to
correct it. I don't think any of us are trying to redesign the airplane,
just
make it last. If skins have to be replaced every year as a result of use,
then
something is wrong. I don't see many skins wrinkled on Cessna's. We all
make
hard landings.

There is a problem in the Experimental manufacturing process that should be
considered. Manufacturers want the cheapest lightest possible. That is
what
sells airplanes. Face it, they are in business to make money. If you
compare
Cessna's with Rebels what are the differences. Price only? No there are a
lot
of design changes and they are definitely heavier as a result. Murphy
advertises "low price, rugged construction" yet we are bending the
airframes.
Why. I know of just a few that are being used in the way we all want to use
them, off airports. Beefing up these area's that need it are going to
become
more and more apparent as the off airport usage becomes more and more.
Floats
have been a great contributor in the strength indicator area. While Murphy
bent
2 firewalls and broke 1 windshield at Oshkosh, I heard of no other
airplanes
with problems. Might have been. Enlighten me if so. But don't ignore the
problems that might crop up because Murphy doesn't see your problem as a
problem. Remember that it costs a lot to make changes to a design that has
been
out for 8 years and the problems they recognize is an admission of "you
better
change this, it is not adequate". It is great that they do this. Other
companies don't.

A for instance on cost of construction. Did you know that from the tailcone
to
the firewall the side panels can be cut from one piece of 48" wide material?
But Murphy chose to use 5 separate pieces. Why? Could it be cost? I
replaced
those 5 pieces with one piece of .025 material and what a difference in
strength. No seams either. Also the "waist" that is created right behind
the
door post. That is a difficult transition of metals and created a weak
point
that I found on the ground loop. I asked about that area when originally
building and was told that it was strictly a cost factor. The molds for the
bulkheads would have to be made for that one rib and not a consideration.
Running stringers from the square area to the tailcone and attaching these
stringers to the rib completely removes the "waist" and really streamlines
the
airframe. Yes, it also allows the forces from a hard landing to be passed
and
shared full length of the airframe, but isn't that better than a bent
airframe?

Just thoughts I have had and built into my airframe as a result of
misfortune.
I feel I have a better airplane as a result.

Just so you understand though, I am glad Murphy designed it like they did
and I
have all the respect for them in the world. Daryl has come to look at the
changes I have made over the years and has been very kind in his critic of
them. If there is something he doesn't like, he tells me. If there is a
problem he can see coming up, he tells me. Just remember that condoning a
change for one airframe because of one problem makes for a real problem for
the
manufacturer as far as a business standpoint goes. Don't expect them to be
very
receptive.

Dave Bangle

"Morehouse, Daniel G" wrote:

Hello!

FYI: I spoke with ... gosh forgot his name... at Murphy. He's the very
pleasant gentleman who has just recently replaced Dennis. Anyway it was
about strengthening the doorposts, etc. that we have been discussing a lot
recently on the board. Grant! That's his name. Now he said that he

couldn't

condone all the reinforcements that have been suggested by the builders.

He

felt that the likely reason for structural failure was hard landings.

Also,

by reinforcing one would change the stress load in the plane causing

failure

someplace else.

Happy building,
Dan
R280

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Subject: Re: strengthening cabin/firewall
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Morehouse, Daniel G wrote:

Hello!

FYI: I spoke with ... gosh forgot his name... at Murphy. He's the very
pleasant gentleman who has just recently replaced Dennis. Anyway it was
about strengthening the doorposts, etc. that we have been discussing a lot
recently on the board. Grant! That's his name. Now he said that he

couldn't

condone all the reinforcements that have been suggested by the builders.

He

felt that the likely reason for structural failure was hard landings.

Also,

by reinforcing one would change the stress load in the plane causing

failure

someplace else.

Happy building,
Dan
R280

What happened to Dennis at MAM?

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To: <murphy-rebel@dcsol.com> (Murphy Rebel)
From: Bob Patterson <bob.patterson@canrem.com>
Subject: Re: strengthening cabin/firewall
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Date: Tue, 24 Nov 1998 10:04:17 -0500


Hi Alister,
I'm inclined to agree with Grant concerning the 'mods' - he's
likely echoing Darryl's thoughts about 'ad-libbed fixes'. (Not to
deny that you have a real problem there - and I'm sure a fix WILL
be found.)

If anyone is in doubt, send a drawing along to the factory - they
HAVE included builders ideas into the production kits BEFORE, and
likely would again - IF they were valuable...

They have ALSO seen some "brilliant" fixes - like sawing through
and disposing of the wing stringers to make it easier to fit welded
aluminum tanks !!! ("Cessna used them, so they MUST be better than a
wet wing" !!!) The stringers, of course, are VITAL to the proper
distribution of loads through the wing & fuse....

<SOME> of the ideas I've heard for "strengthening" certainly
have raised comments from engineers along the lines of: "an extra row of
rivets on the skin" "- Great ! - might as well have an arrow saying 'tear
along this line' " !!
I'm not really sure about those brackets at the base of the door
post - I've never seen a problem in that area, but extra holes in the
corner wrap worry me. (Lots of epoxy chromate between the parts might help
distribute the load, easing the load around those holes ....)
Several people have asked about a "V" brace from the wing roots
to the firewall - "Cessna needs one, so they MUST be good" !!! Sure,
just like "Cessna uses spring gear, so it MUST be good" !!! ;-)
Cessnas need the 'V' brace because the fuselage twists & flexes
MUCH more than the Rebel. Of course, if you fly into big enough waves,
or sideslip into the ground (both have happened !),you can get the Rebel to
twist, too - but if the waves are THAT big, the Cessna would be <breaking>
!!

Very few people have mentioned doing anything about the panel
between the bottom of the door and the bottom of the fuse - THIS <IS>
an area I've seen flexing & bowing, to the extent that it can be hard
to close the door ! If you're still building, I'd remake this plate
out of .032, AND add some pieces of wing stringer or ST-31 vertically
between the base & the door frame. By now, I hope everybody is using
..025 or .032 ST-31 for the door frames, instead of the old .016 stuff ...

I agree that hard usage has shown up some problems, but certainly
<SOME> of these problems will go away when the structure is firmly BONDED
TOGETHER with the EPOXY CHROMATE supplied WITH THE KIT !!! Brush it on
both sides, and put the pieces together WET .... Without this bonding,
ALL the load is carried by the RIVETS - greatly increasing the shear load
on them. Lots of epoxy can be very helpful between skins and door post,
and ALL OVER the corner wrap overlap area.

I am surprised we haven't heard more about the suggestion for
an additional row of 3/16" rivets staggered up the door post - has
anyone asked the factory directly about this ???

I still feel the Rebel is basically a great little airplane.
It has a FEW spots that need beefing up, IF you're giving it a hard
workout - but then, what airplane doesn't !! If you try to build an
aircraft so strong & rugged it'll NEVER need structural maintenance,
you MAY have a little trouble getting it off the ground !! :-)

....bobp

--------------------------------orig.--------------------------------
At 08:32 AM 11/23/98 +1300, you wrote:

Hi Dan,

I think thats a pretty bold statement by Grant, ( I guess you are talking
about), I have only done 40 hrs in my Rebel with NO hard landings, But it
has been used on uneven surfaces ( that why I bought the Rebel, its
supposed to be an off airfield machine!) There is definately working
(smoking ) of the rivets up the door post which I am repairing at the
moment. In my opinion there are definately issues in the Spring gear
attachment and load distribution that need working through.

Alister


----------

From: Morehouse, Daniel G <DMorehouse@peacehealth.org>
To: 'murphy-rebel@dcsol.com'
Subject: strengthening cabin/firewall
Date: Monday, November 23, 1998 6:45 AM

Hello!

FYI: I spoke with ... gosh forgot his name... at Murphy. He's the very
pleasant gentleman who has just recently replaced Dennis. Anyway it was
about strengthening the doorposts, etc. that we have been discussing a

lot

recently on the board. Grant! That's his name. Now he said that he

couldn't

condone all the reinforcements that have been suggested by the builders.

He

felt that the likely reason for structural failure was hard landings.

Also,

by reinforcing one would change the stress load in the plane causing

failure

someplace else.


Happy building,
Dan
R280

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From: "Morehouse, Daniel G" <DMorehouse@peacehealth.org>
To: "'murphy-rebel@dcsol.com'" <murphy-rebel@dcsol.com>
Subject: RE: strengthening cabin/firewall
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Hello folks!

I just spoke with Grant yesterday about these topics. I don't have the float
fix doc (again :-( seems it got trashed in my computer 'fixing'), but I
got the impession that we were to add one rivet between the existing row on
the door posts, making twice as many rivets in a single row.

I also mentioned a suggestion I'd seen on this board: adding SS rivets. He
wasn't too fond of that at all. The SS rivets would not smoke (a warning
sign) but instead would tear through the aluminum skin. No warning sign of
increased fatigue.

What I plan on doing in this area is using the 025 corner (originally
intended for the bottom firewall corner) for the top firewall corner;
fabricating 032 corners for the bottom fw corner; overlapping these corners
as well as the door post brace (if any of the dp brace was designed to be
trimmed) enough so an extra row of rivets could be used; will also look at
reinforcing the rolled panels behind/below the door and the side panel
itself (thanks for that info, Bobp).

Cheers,
Dan
R280

----------
From: Bob Patterson[SMTP:bob.patterson@canrem.com]
Reply To: murphy-rebel@dcsol.com
Sent: Tuesday, November 24, 1998 7:04 AM
To: murphy-rebel@dcsol.com
Subject: Re: strengthening cabin/firewall


Hi Alister,
I'm inclined to agree with Grant concerning the 'mods' - he's
likely echoing Darryl's thoughts about 'ad-libbed fixes'. (Not to
deny that you have a real problem there - and I'm sure a fix WILL
be found.)

If anyone is in doubt, send a drawing along to the factory - they
HAVE included builders ideas into the production kits BEFORE, and
likely would again - IF they were valuable...

They have ALSO seen some "brilliant" fixes - like sawing through
and disposing of the wing stringers to make it easier to fit welded
aluminum tanks !!! ("Cessna used them, so they MUST be better than a
wet wing" !!!) The stringers, of course, are VITAL to the proper
distribution of loads through the wing & fuse....

<SOME> of the ideas I've heard for "strengthening" certainly
have raised comments from engineers along the lines of: "an extra row of
rivets on the skin" "- Great ! - might as well have an arrow saying 'tear
along this line' " !!
I'm not really sure about those brackets at the base of the door
post - I've never seen a problem in that area, but extra holes in the
corner wrap worry me. (Lots of epoxy chromate between the parts might help
distribute the load, easing the load around those holes ....)
Several people have asked about a "V" brace from the wing roots
to the firewall - "Cessna needs one, so they MUST be good" !!! Sure,
just like "Cessna uses spring gear, so it MUST be good" !!! ;-)
Cessnas need the 'V' brace because the fuselage twists & flexes
MUCH more than the Rebel. Of course, if you fly into big enough waves,
or sideslip into the ground (both have happened !),you can get the Rebel
to
twist, too - but if the waves are THAT big, the Cessna would be <breaking>
!!

Very few people have mentioned doing anything about the panel
between the bottom of the door and the bottom of the fuse - THIS <IS>
an area I've seen flexing & bowing, to the extent that it can be hard
to close the door ! If you're still building, I'd remake this plate
out of .032, AND add some pieces of wing stringer or ST-31 vertically
between the base & the door frame. By now, I hope everybody is using
.025 or .032 ST-31 for the door frames, instead of the old .016 stuff ...

I agree that hard usage has shown up some problems, but certainly
<SOME> of these problems will go away when the structure is firmly BONDED
TOGETHER with the EPOXY CHROMATE supplied WITH THE KIT !!! Brush it on
both sides, and put the pieces together WET .... Without this bonding,
ALL the load is carried by the RIVETS - greatly increasing the shear load
on them. Lots of epoxy can be very helpful between skins and door post,
and ALL OVER the corner wrap overlap area.

I am surprised we haven't heard more about the suggestion for
an additional row of 3/16" rivets staggered up the door post - has
anyone asked the factory directly about this ???

I still feel the Rebel is basically a great little airplane.
It has a FEW spots that need beefing up, IF you're giving it a hard
workout - but then, what airplane doesn't !! If you try to build an
aircraft so strong & rugged it'll NEVER need structural maintenance,
you MAY have a little trouble getting it off the ground !! :-)

....bobp

--------------------------------orig.--------------------------------
At 08:32 AM 11/23/98 +1300, you wrote:

Hi Dan,

I think thats a pretty bold statement by Grant, ( I guess you are talking
about), I have only done 40 hrs in my Rebel with NO hard landings, But it
has been used on uneven surfaces ( that why I bought the Rebel, its
supposed to be an off airfield machine!) There is definately working
(smoking ) of the rivets up the door post which I am repairing at the
moment. In my opinion there are definately issues in the Spring gear
attachment and load distribution that need working through.

Alister


----------

From: Morehouse, Daniel G <DMorehouse@peacehealth.org>
To: 'murphy-rebel@dcsol.com'
Subject: strengthening cabin/firewall
Date: Monday, November 23, 1998 6:45 AM

Hello!

FYI: I spoke with ... gosh forgot his name... at Murphy. He's the very
pleasant gentleman who has just recently replaced Dennis. Anyway it

was

about strengthening the doorposts, etc. that we have been discussing a

lot

recently on the board. Grant! That's his name. Now he said that he

couldn't

condone all the reinforcements that have been suggested by the

builders.

He

felt that the likely reason for structural failure was hard landings.

Also,

by reinforcing one would change the stress load in the plane causing

failure

someplace else.


Happy building,
Dan
R280

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