The Murphy Builders Site

In scanning the manual (from early 90s) I see a comment that has not been mentioned that I can recall about the reason for moving the firewall back for the heavier engine. The reason stated is to shorten the moment arm to reduce loads on the cabin structure.
Wayne, I don't recall you mentioning any reinforcements that specifically address this aspect. Have I missed something?
Thanks
Peter.

Well Peter! There is the double pitched row of rivets up the forward door post (with the top 3 or 4's pitch left as is but upsized to 3/16") that I have recommended since the winter of 1996 FOR ANY ENGINE INSTALLATION (well before MAM put out the "float fix" bulletin after a couple aircraft, including the factory Elite, were damaged at Osh and something had to be done officially then). I can show you the pictures of why I started doing this in 1996, next time you are over, but I'm not going to post them! Lets just say that the original rivet pitch (with an O-235 engine) didn't hold up to one ski, 2 G landings on ice!!!! Like I keep telling you guys/gals I am rarely offering "theory" and/or calculated loads. I am passing on specific things that I've found necessary, to keep the thing together, from proven "destructive testing". In support of MAM, for their lack of offerings on some of the stuff that has been found necessary to reinforce the Rebel over the years, MAM doesn't hold onto their airplanes long enough to see most of this and I have yet to see Robin screw up a landing either!!!!

I really don't buy the "shorten the moment arm to reduce the loads on the cabin structure" bull. If the O-235 was supposed to be fine at the original engine position, the O-320 isn't going to make a big difference. The weight difference in engines is only about 30 pounds. If we were talking moving the engine in a foot maybe, but not 3 inches.

In a (-)2.5 G (ouch!) landing that is only 75 pounds extra load (less than one extra RV1410 rivets shear strength). I am not going to try to figure out the load values difference on the rivets at the top of the door post by moving the engine in 3" to 36.5", from the original 39.5", but will only say it's not going to make a big difference structurally (changes c of g significantly, but not load on door post rivets that are in "shear"). If you have added the float fix doubler at the top of the post, or have done the double staggered row of rivets up the door post (so the "guillotine" effect can't get started at the top of the door post and shear all the rivets out right down to the wing strut attach fitting!) you will be fine. I can state this with confidence only because I have tried the same "testing" on my Rebel, with the extra rivets up the door post and an O-320 engine, and have determined that this type of "landing" is now a NDT (non-destructive test) instead!!!

'night,
Wayne G. O'Shea
www.irishfield.on.ca

----- Original Message -----

From: Peter Cowan/Lexy Cameron (cowcam@pipcom.com)
To: murphy-rebel@dcsol.com (murphy-rebel@dcsol.com)
Sent: Wednesday, December 26, 2001 9:49 PM
Subject: Firewall position


In scanning the manual (from early 90s) I see a comment that has not been mentioned that I can recall about the reason for moving the firewall back for the heavier engine. The reason stated is to shorten the moment arm to reduce loads on the cabin structure.
Wayne, I don't recall you mentioning any reinforcements that specifically address this aspect. Have I missed something?
Thanks
Peter.

G'day Wayne !....(and a Very Merry Christmas & New year to you and the "tribe" as well ! :-)

I have just read with great interest , THIS e-mail stating to "double row and stagger" the rivets up the door post
/ hinge as this is "standard practice since '96 "....Got to admit , I hadn't heard of it either ! :-(......I'll have a sticky at the plane whilst I'm out there tomorrow (it lives a bit over an hours drive away from home )

I have a single row of 1/8" rivets down that joint (as per the plans...as I have not been told any different)....should I

1) Replace them all with 3/16" ?

OR

2) ADD another row,(of 1/8" rivets) staggered to the first ?

Also, I just noticed today, some small cracks at the bottom of the tailcone (down below the bottom Rudder
pivot)...... ( I have 85 hours to date and 169 landings), ...I know that there has been some talk of this area having a "doubler skin" fitted....but I was hoping to "get away with not having to do it" as I fitted a real SPRING on the tailwheel...which has lots of "give" and allows the tail of the plane to move around "a bit"...NOT like the solid / unmovable hunk of aluminium that was supplied with the kit.

Should I fabricate a doubler from .032" 6061 T6.....or thicker....and / or from something stronger , say 2024 T3
(and what do I do with the small cracks already in the tailcone... (about 3/8" long), apart from stop drilling them ?)

Any help will be gratefully received

Thanks

Rick & Wendy in OZ
541R

----- Original Message -----
From: Wayne G. O'Shea (oifa@irishfield.on.ca)
To: murphy-rebel@dcsol.com (murphy-rebel@dcsol.com)
Sent: Thursday, 27 December 2001 15:15
Subject: Re: Firewall position


Well Peter! There is the double pitched row of rivets up the forward door post (with the top 3 or 4's pitch left as is but upsized to 3/16") that I have recommended since the winter of 1996 FOR ANY ENGINE INSTALLATION (well before MAM put out the "float fix" bulletin after a couple aircraft, including the factory Elite, were damaged at Osh and something had to be done officially then). I can show you the pictures of why I started doing this in 1996, next time you are over, but I'm not going to post them! Lets just say that the original rivet pitch (with an O-235 engine) didn't hold up to one ski, 2 G landings on ice!!!! Like I keep telling you guys/gals I am rarely offering "theory" and/or calculated loads. I am passing on specific things that I've found necessary, to keep the thing together, from proven "destructive testing". In support of MAM, for their lack of offerings on some of the stuff that has been found necessary to reinforce the Rebel over the years, MAM doesn't hold onto their airplanes long enough to see most of this and I have yet to see Robin screw up a landing either!!!!

I really don't buy the "shorten the moment arm to reduce the loads on the cabin structure" bull. If the O-235 was supposed to be fine at the original engine position, the O-320 isn't going to make a big difference. The weight difference in engines is only about 30 pounds. If we were talking moving the engine in a foot maybe, but not 3 inches.

In a (-)2.5 G (ouch!) landing that is only 75 pounds extra load (less than one extra RV1410 rivets shear strength). I am not going to try to figure out the load values difference on the rivets at the top of the door post by moving the engine in 3" to 36.5", from the original 39.5", but will only say it's not going to make a big difference structurally (changes c of g significantly, but not load on door post rivets that are in "shear"). If you have added the float fix doubler at the top of the post, or have done the double staggered row of rivets up the door post (so the "guillotine" effect can't get started at the top of the door post and shear all the rivets out right down to the wing strut attach fitting!) you will be fine. I can state this with confidence only because I have tried the same "testing" on my Rebel, with the extra rivets up the door post and an O-320 engine, and have determined that this type of "landing" is now a NDT (non-destructive test) instead!!!

'night,
Wayne G. O'Shea
www.irishfield.on.ca

----- Original Message -----

From: Peter Cowan/Lexy Cameron (cowcam@pipcom.com)
To: murphy-rebel@dcsol.com (murphy-rebel@dcsol.com)
Sent: Wednesday, December 26, 2001 9:49 PM
Subject: Firewall position


In scanning the manual (from early 90s) I see a comment that has not been mentioned that I can recall about the reason for moving the firewall back for the heavier engine. The reason stated is to shorten the moment arm to reduce loads on the cabin structure.
Wayne, I don't recall you mentioning any reinforcements that specifically address this aspect. Have I missed something?
Thanks
Peter.

Hi Wayne,
I agree with your comments, but I am curious. I wonder if another contributing facter to moving the firewall back was that Murphy ran into a crashworthiness or other limitations imposed by FAR, Part 23 or JAR-VLA. I am pretty sure they designed the Rebel to meet or exceed these requirements even though it is not a certified airplane. Hiscocks book talks about extra considerations in the cabin structure including higher load factors and G forces. He also talks about using higher factors for limit loading in the structure in this area so the airplane designer/manufacturer seeking certification can avoid doing drop tests. I also think that Murphy originally designed the Rebel for a Rotax engine and a gross weight of 1450 lb. Going to an 0-290 might have been pushing the limit of their design envelope necessary for certification. The 0-320 must be right on the edge. Moving the firewall back 3 inches must really help expand that envelope because MAM allows an 0-360 engine and an airplane gross weight of 1800 lb. Also, I can see a conservative designer (Darrell???) thnking soorer or later someone who is an 0-320 kind of guy is also going to bolt on a contant speed prop just to make life difficult for the designer. And just gotta have that 20 lb vibration damper on the nose ...etc etc. I really appreciate your thoughts and contributions to this forum. I am learning a lot from your enlightened experience and learning is a big part of the fun for me.
- Chuck Skorupa -
Elite taildragger SN 500E

----- Original Message -----
From: Peter Cowan/Lexy Cameron (cowcam@pipcom.com)
To: murphy-rebel@dcsol.com (murphy-rebel@dcsol.com)
Sent: Thursday, December 27, 2001 5:15 AM
Subject: Re: Firewall position


Thanks for that Wayne.
I wasn't expecting an engineering analysis of the front end just your thoughts and experiences on what extra weight has done in that area. You see my Mazda Rotary is going to be a little heavier than the 0-320 so just looking ahead to possible issues.
Peter

Well Peter! There is the double pitched row of rivets up the forward door post (with the top 3 or 4's pitch left as is but upsized to 3/16") that I have recommended since the winter of 1996 FOR ANY ENGINE INSTALLATION (well before MAM put out the "float fix" bulletin after a couple aircraft, including the factory Elite, were damaged at Osh and something had to be done officially then). I can show you the pictures of why I started doing this in 1996, next time you are over, but I'm not going to post them! Lets just say that the original rivet pitch (with an O-235 engine) didn't hold up to one ski, 2 G landings on ice!!!! Like I keep telling you guys/gals I am rarely offering "theory" and/or calculated loads. I am passing on specific things that I've found necessary, to keep the thing together, from proven "destructive testing". In support of MAM, for their lack of offerings on some of the stuff that has been found necessary to reinforce the Rebel over the years, MAM doesn't hold onto their airplanes long enough to see most of this and I have yet to see Robin screw up a landing either!!!!

I really don't buy the "shorten the moment arm to reduce the loads on the cabin structure" bull. If the O-235 was supposed to be fine at the original engine position, the O-320 isn't going to make a big difference. The weight difference in engines is only about 30 pounds. If we were talking moving the engine in a foot maybe, but not 3 inches.

In a (-)2.5 G (ouch!) landing that is only 75 pounds extra load (less than one extra RV1410 rivets shear strength). I am not going to try to figure out the load values difference on the rivets at the top of the door post by moving the engine in 3" to 36.5", from the original 39.5", but will only say it's not going to make a big difference structurally (changes c of g significantly, but not load on door post rivets that are in "shear"). If you have added the float fix doubler at the top of the post, or have done the double staggered row of rivets up the door post (so the "guillotine" effect can't get started at the top of the door post and shear all the rivets out right down to the wing strut attach fitting!) you will be fine. I can state this with confidence only because I have tried the same "testing" on my Rebel, with the extra rivets up the door post and an O-320 engine, and have determined that this type of "landing" is now a NDT (non-destructive test) instead!!!

'night,
Wayne G. O'Shea

Hi Peter !

There have been several structural reiforcements incorporated
into the Rebel since the 'early 90's' ....

There was some merit in moving the engine back when the original
corner wraps (FUS-10) were only .020 - this was <barely> adequate for
the O-235's weight, IF you were very careful not to dent them. Now that
they've increased to .025, and finally .032, they can handle the extra
loads much better. When you add in the 'floatfix' mods, you have a LOT
more strength than before. There are many of us who feel the extra
leg room, improved visibility, and easier windshield installation of
the 'standard' engine position outweigh any strength or handling concerns.
There is also the advantage of flexibility in engine choice at any time.
As always, though - it's your choice !! :-)

.....bobp

-----------------------------------orig.--------------------------------
At 09:49 PM 12/26/01 -0500, you wrote:

In scanning the manual (from early 90s) I see a comment that has not been

mentioned that I can recall about the reason for moving the firewall back
for the heavier engine. The reason stated is to shorten the moment arm to
reduce loads on the cabin structure.

Wayne, I don't recall you mentioning any reinforcements that specifically

address this aspect. Have I missed something?

Thanks
Peter.
<!DOCTYPE HTML PUBLIC "-//W3C//DTD W3 HTML//EN">
<HTML>
<HEAD>

<META content="text/html; charset=iso-8859-5" http-equiv=Content-Type>
<META content='"MSHTML 4.72.3110.7"' name=GENERATOR>
</HEAD>
<BODY bgColor=#ffffff>
<DIV><FONT color=#000000 face="Bookman Old Style" size=2>In scanning the

manual

(from early 90s) I see a comment that has not been mentioned that I can recall
about the reason for moving the firewall back for the heavier engine. The

reason

stated is to shorten the moment arm to reduce loads on the cabin structure.
</FONT></DIV>
<DIV><FONT face="Bookman Old Style" size=2>Wayne, I don't recall you

mentioning

any reinforcements that specifically address this aspect. Have I missed
something?</FONT></DIV>
<DIV><FONT face="Bookman Old Style" size=2>Thanks</FONT></DIV>
<DIV><FONT face="Bookman Old Style" size=2>Peter.</FONT></DIV></BODY></HTML>

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G'day Wayne

Do you recommend the extra rivets on a standard Rebel with a Rotax 912.
It will not be used on skis or floats. (Not much ice or water where I live!)



Regards


Ian Donaldson

Thanks for that Wayne.
I wasn't expecting an engineering analysis of the front end just your thoughts and experiences on what extra weight has done in that area. You see my Mazda Rotary is going to be a little heavier than the 0-320 so just looking ahead to possible issues.
Peter

Well Peter! There is the double pitched row of rivets up the forward door post (with the top 3 or 4's pitch left as is but upsized to 3/16") that I have recommended since the winter of 1996 FOR ANY ENGINE INSTALLATION (well before MAM put out the "float fix" bulletin after a couple aircraft, including the factory Elite, were damaged at Osh and something had to be done officially then). I can show you the pictures of why I started doing this in 1996, next time you are over, but I'm not going to post them! Lets just say that the original rivet pitch (with an O-235 engine) didn't hold up to one ski, 2 G landings on ice!!!! Like I keep telling you guys/gals I am rarely offering "theory" and/or calculated loads. I am passing on specific things that I've found necessary, to keep the thing together, from proven "destructive testing". In support of MAM, for their lack of offerings on some of the stuff that has been found necessary to reinforce the Rebel over the years, MAM doesn't hold onto their airplanes long enough to see most of this and I have yet to see Robin screw up a landing either!!!!

I really don't buy the "shorten the moment arm to reduce the loads on the cabin structure" bull. If the O-235 was supposed to be fine at the original engine position, the O-320 isn't going to make a big difference. The weight difference in engines is only about 30 pounds. If we were talking moving the engine in a foot maybe, but not 3 inches.

In a (-)2.5 G (ouch!) landing that is only 75 pounds extra load (less than one extra RV1410 rivets shear strength). I am not going to try to figure out the load values difference on the rivets at the top of the door post by moving the engine in 3" to 36.5", from the original 39.5", but will only say it's not going to make a big difference structurally (changes c of g significantly, but not load on door post rivets that are in "shear"). If you have added the float fix doubler at the top of the post, or have done the double staggered row of rivets up the door post (so the "guillotine" effect can't get started at the top of the door post and shear all the rivets out right down to the wing strut attach fitting!) you will be fine. I can state this with confidence only because I have tried the same "testing" on my Rebel, with the extra rivets up the door post and an O-320 engine, and have determined that this type of "landing" is now a NDT (non-destructive test) instead!!!

'night,
Wayne G. O'Shea

Ian, If you are not painted yet I would definitely do the extra row of rivets. If you are painted, see how well your left over paint is brushable over a rivet head. I find most paints flow well, by brush, over the rivets and stay on for about 2 years before needing a touch up. If you (have more patience than me) brush prime the rivets, then paint and you would probably be even better. Theoretically the 912 would have about half the need for rivets in the door post, as the Lyco's, but after seeing the damage done to a 912 Rebel from just a prop loss, I would add anything that us Lyco drivers are using from the door posts forward!

Regards,
Wayne G. O'Shea
www.irishfield.on.ca

----- Original Message -----
From: allsure (allsure@iprimus.com.au)
To: murphy-rebel@dcsol.com (murphy-rebel@dcsol.com)
Sent: Thursday, December 27, 2001 7:45 AM
Subject: Re: Firewall position


G'day Wayne

Do you recommend the extra rivets on a standard Rebel with a Rotax 912.
It will not be used on skis or floats. (Not much ice or water where I live!)



Regards


Ian Donaldson

Question for Wayne for the benifit of many,
I have a single row of 1/8 dia Avex rivets all the way up the door post. Instead of replacing these with 3/16 dia, what are your thoughts on using 1/8 dia Cherry structural rivets?
Rick D.
"Wayne G. O'Shea" wrote:

Well Peter! There is the double pitched row of rivets up the forward door post (with the top 3 or 4's pitch left as is but upsized to 3/16") that I have recommended since the winter of 1996 FOR ANY ENGINE INSTALLATION (well before MAM put out the "float fix" bulletin after a couple aircraft, including the factory Elite, were damaged at Osh and something had to be done officially then). I can show you the pictures of why I started doing this in 1996, next time you are over, but I'm not going to post them! Lets just say that the original rivet pitch (with an O-235 engine) didn't hold up to one ski, 2 G landings on ice!!!! Like I keep telling you guys/gals I am rarely offering "theory" and/or calculated loads. I am passing on specific things that I've found necessary, to keep the thing together, from proven "destructive testing". In support of MAM, for their lack of offerings on some of the stuff that has been found necessary to reinforce the Rebel over the years, MAM doesn't hold onto their airplanes long enough to see most of this and I have yet to see Robin screw up a landing either!!!! I really don't buy the "shorten the moment arm to reduce the loads on the cabin structure" bull. If the O-235 was supposed to be fine at the original engine position, the O-320 isn't going to make a big difference. The weight difference in engines is only about 30 pounds. If we were talking moving the engine in a foot maybe, but not 3 inches. In a (-)2.5 G (ouch!) landing that is only 75 pounds extra load (less than one extra RV1410 rivets shear strength). I am not going to try to figure out the load values difference on the rivets at the top of the door post by moving the engine in 3" to 36.5", from the original 39.5", but will only say it's not going to make a big difference structurally (changes c of g significantly, but not load on door post rivets that are in "shear"). If you have added the float fix doubler at the top of the post, or have done the double staggered row of rivets up the door post (so the "guillotine" effect can't get started at the top of the door post and shear all the rivets out right down to the wing strut attach fitting!) you will be fine. I can state this with confidence only because I have tried the same "testing" on my Rebel, with the extra rivets up the door post and an O-320 engine, and have determined that this type of "landing" is now a NDT (non-destructive test) instead!!! 'night,Wayne G. O'Sheawww.irishfield.on.ca

Rick, you do not replace ALL the rivets with 3/16, just the 4 at the top that are too close together to double pitch! The rest get double pitched and stay 1/8". Either well dipped RR5404 stainless or RV1410's. The Cherry rivets are a nightmare if you ever want (should I say have) to take them back out. Also, an RV1410 is about 0.6 the strength of a solid rivet, so 2 of them are 1.2 the strength of a solid (or Cherry). So you are better to use the extra set of RV1410's to keep everything looking the same, easy to work with and 0.2 stronger!

Wayne

----- Original Message -----
From: Rick DeCiero (rsdec1@star.net)
To: murphy-rebel@dcsol.com (murphy-rebel@dcsol.com)
Sent: Thursday, December 27, 2001 12:58 PM
Subject: Re: Firewall position


Question for Wayne for the benifit of many,
I have a single row of 1/8 dia Avex rivets all the way up the door post. Instead of replacing these with 3/16 dia, what are your thoughts on using 1/8 dia Cherry structural rivets?
Rick D.
"Wayne G. O'Shea" wrote:

Well Peter! There is the double pitched row of rivets up the forward door post (with the top 3 or 4's pitch left as is but upsized to 3/16") that I have recommended since the winter of 1996 FOR ANY ENGINE INSTALLATION (well before MAM put out the "float fix" bulletin after a couple aircraft, including the factory Elite, were damaged at Osh and something had to be done officially then). I can show you the pictures of why I started doing this in 1996, next time you are over, but I'm not going to post them! Lets just say that the original rivet pitch (with an O-235 engine) didn't hold up to one ski, 2 G landings on ice!!!! Like I keep telling you guys/gals I am rarely offering "theory" and/or calculated loads. I am passing on specific things that I've found necessary, to keep the thing together, from proven "destructive testing". In support of MAM, for their lack of offerings on some of the stuff that has been found necessary to reinforce the Rebel over the years, MAM doesn't hold onto their airplanes long enough to see most of this and I have yet to see Robin screw up a landing either!!!! I really don't buy the "shorten the moment arm to reduce the loads on the cabin structure" bull. If the O-235 was supposed to be fine at the original engine position, the O-320 isn't going to make a big difference. The weight difference in engines is only about 30 pounds. If we were talking moving the engine in a foot maybe, but not 3 inches. In a (-)2.5 G (ouch!) landing that is only 75 pounds extra load (less than one extra RV1410 rivets shear strength). I am not going to try to figure out the load values difference on the rivets at the top of the door post by moving the engine in 3" to 36.5", from the original 39.5", but will only say it's not going to make a big difference structurally (changes c of g significantly, but not load on door post rivets that are in "shear"). If you have added the float fix doubler at the top of the post, or have done the double staggered row of rivets up the door post (so the "guillotine" effect can't get started at the top of the door post and shear all the rivets out right down to the wing strut attach fitting!) you will be fine. I can state this with confidence only because I have tried the same "testing" on my Rebel, with the extra rivets up the door post and an O-320 engine, and have determined that this type of "landing" is now a NDT (non-destructive test) instead!!! 'night,Wayne G. O'Sheawww.irishfield.on.ca

Hi Rick !

The extra, staggered row of 1/8" rivets down the door post is
probably well worth the effort now, rather than the pain later.

A doubler of FUS-30 made of .032 6061 T-6 should be more than
adequate. Be sure to rivet to the horizontal bulkhead next to the
stabilizer at the top, as well as up the rudder post, and at several
places over the cone. It is important to use lots of Polyfiber Epoxy
primer between the 2 pieces, to help bond them together, as well as
prevent water from getting in there. We've been recommending this
doubler since the first Rebel was completed in Ontario - they ALL
need it !

Hope those ferocious fires we're seeing on TV are well away
from where you are !

....bobp

------------------------------orig.----------------------------------------
At 05:07 PM 12/20/01 +1100, you wrote:

G'day Wayne !....(and a Very Merry Christmas & New year to you and the

"tribe" as well ! :-)

I have just read with great interest , THIS e-mail stating to "double row

and stagger" the rivets up the door post

/ hinge as this is "standard practice since '96 "....Got to admit , I

hadn't heard of it either ! :-(......I'll have a sticky at the plane whilst
I'm out there tomorrow (it lives a bit over an hours drive away from home )

I have a single row of 1/8" rivets down that joint (as per the plans...as I

have not been told any different)....should I

1) Replace them all with 3/16" ?

OR

2) ADD another row,(of 1/8" rivets) staggered to the first ?

Also, I just noticed today, some small cracks at the bottom of the tailcone

(down below the bottom Rudder

pivot)...... ( I have 85 hours to date and 169 landings), ...I know that

there has been some talk of this area having a "doubler skin" fitted....but
I was hoping to "get away with not having to do it" as I fitted a real
SPRING on the tailwheel...which has lots of "give" and allows the tail of
the plane to move around "a bit"...NOT like the solid / unmovable hunk of
aluminium that was supplied with the kit.

Should I fabricate a doubler from .032" 6061 T6.....or thicker....and / or

from something stronger , say 2024 T3

(and what do I do with the small cracks already in the tailcone... (about

3/8" long), apart from stop drilling them ?)

Any help will be gratefully received

Thanks

Rick & Wendy in OZ
541R

----- Original Message -----
From: Wayne G. O'Shea
To: murphy-rebel@dcsol.com
Sent: Thursday, 27 December 2001 15:15
Subject: Re: Firewall position


Well Peter! There is the double pitched row of rivets up the forward door

post (with the top 3 or 4's pitch left as is but upsized to 3/16") that I
have recommended since the winter of 1996 FOR ANY ENGINE INSTALLATION (well
before MAM put out the "float fix" bulletin after a couple aircraft,
including the factory Elite, were damaged at Osh and something had to be
done officially then). I can show you the pictures of why I started doing
this in 1996, next time you are over, but I'm not going to post them! Lets
just say that the original rivet pitch (with an O-235 engine) didn't hold up
to one ski, 2 G landings on ice!!!! Like I keep telling you guys/gals I am
rarely offering "theory" and/or calculated loads. I am passing on specific
things that I've found necessary, to keep the thing together, from proven
"destructive testing". In support of MAM, for their lack of offerings on
some of the stuff that has been found necessary to reinforce the Rebel over
the years, MAM doesn't hold onto their airplanes long enough to see most of
this and I have yet to see Robin screw up a landing either!!!!

I really don't buy the "shorten the moment arm to reduce the loads on the

cabin structure" bull. If the O-235 was supposed to be fine at the original
engine position, the O-320 isn't going to make a big difference. The weight
difference in engines is only about 30 pounds. If we were talking moving the
engine in a foot maybe, but not 3 inches.

In a (-)2.5 G (ouch!) landing that is only 75 pounds extra load (less

than one extra RV1410 rivets shear strength). I am not going to try to
figure out the load values difference on the rivets at the top of the door
post by moving the engine in 3" to 36.5", from the original 39.5", but will
only say it's not going to make a big difference structurally (changes c of
g significantly, but not load on door post rivets that are in "shear"). If
you have added the float fix doubler at the top of the post, or have done
the double staggered row of rivets up the door post (so the "guillotine"
effect can't get started at the top of the door post and shear all the
rivets out right down to the wing strut attach fitting!) you will be fine. I
can state this with confidence only because I have tried the same "testing"
on my Rebel, with the extra rivets up the door post and an O-320 engine, and
have determined that this type of "landing" is now a NDT (non-destructive
test) instead!!!

'night,
Wayne G. O'Shea
www.irishfield.on.ca

----- Original Message -----
From: Peter Cowan/Lexy Cameron
To: murphy-rebel@dcsol.com
Sent: Wednesday, December 26, 2001 9:49 PM
Subject: Firewall position


In scanning the manual (from early 90s) I see a comment that has not

been mentioned that I can recall about the reason for moving the firewall
back for the heavier engine. The reason stated is to shorten the moment arm
to reduce loads on the cabin structure.

Wayne, I don't recall you mentioning any reinforcements that

specifically address this aspect. Have I missed something?

Thanks
Peter.
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<DIV><FONT size=2>G'day Wayne !....(and a Very Merry Christmas & New

year to

you and the "tribe" as well ! :-)</FONT></DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT size=2>I have just read with great interest , THIS e-mail

stating to

"double row and stagger" the rivets up the door post</FONT></DIV>
<DIV><FONT size=2>/ hinge as this is "standard practice since '96 "....Got to
admit , I hadn't heard of it either ! :-(......I'll have a sticky at the plane
whilst I'm out there tomorrow (it lives a bit over an hours drive away from

home

)</FONT></DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT size=2>I have a single row of 1/8" rivets down that joint (as

per the

plans...as I have not been told any different)....should I </FONT></DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT size=2>1) Replace them all with 3/16"&nbsp;&nbsp; ?</FONT></DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT size=2>OR</FONT></DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT size=2>2) ADD another row,(of 1/8" rivets) staggered to the first
?</FONT></DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT size=2>Also, I just noticed today, some small cracks at the

bottom of

the tailcone (down below the bottom Rudder</FONT></DIV>
<DIV><FONT size=2>pivot)...... ( I have 85 hours to date and 169 landings),

...I

know that there has been some talk of this area having a "doubler skin"
fitted....but I was hoping to </FONT><FONT size=2>"get away with not having to
do it" as I fitted a real SPRING&nbsp; on the tailwheel...which has lots of
"give" and allows the tail of the plane to move around "a bit"...NOT like the
solid / unmovable hunk of aluminium that was supplied with the

kit.</FONT></DIV>

<DIV>&nbsp;</DIV>
<DIV><FONT size=2>Should I fabricate a doubler from .032" 6061 T6.....or
thicker....and / or from something stronger , say 2024 T3</FONT></DIV>
<DIV><FONT size=2>(and what do I do with the small cracks already in the
tailcone... (about 3/8" long), apart from stop drilling them ?)</FONT></DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT size=2>Any help will be gratefully received </FONT></DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT size=2>Thanks</FONT></DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT size=2>Rick & Wendy in OZ</FONT></DIV>
<DIV><FONT size=2>541R</FONT></DIV>
<DIV>&nbsp;</DIV>
<BLOCKQUOTE dir=ltr
style="BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px;

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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color:

black"><B>From:</B>

<A href="mailto:oifa@irishfield.on.ca" title=oifa@irishfield.on.ca>Wayne G.
O'Shea</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
href="mailto:murphy-rebel@dcsol.com"
title=murphy-rebel@dcsol.com>murphy-rebel@dcsol.com</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Thursday, 27 December 2001
15:15</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: Firewall position</DIV>
<DIV><BR></DIV>
<DIV><FONT face=Arial size=2>Well Peter! There is the double pitched row of
rivets up the forward door post (with the&nbsp;top 3 or 4's pitch left as
is&nbsp;but&nbsp;upsized to 3/16")&nbsp;that
I&nbsp;have&nbsp;recommended&nbsp;since the winter of 1996&nbsp;FOR ANY

ENGINE

INSTALLATION (well&nbsp;before MAM put out the "float fix" bulletin after a
couple aircraft, including the&nbsp;factory Elite,&nbsp;were damaged at Osh
and something had to be done officially&nbsp;then). I can show you the
pictures of why I started doing this in 1996,&nbsp;next time you are

over, but

I'm not going to post them!&nbsp;Lets just say that the original rivet pitch
(with an O-235 engine)&nbsp;didn't hold up to one ski, 2 G landings on

ice!!!!

Like I keep telling you guys/gals I am rarely offering "theory" and/or
calculated loads. I am&nbsp;passing on specific things that I've found
necessary, to keep the thing&nbsp;together, from proven&nbsp;"destructive
testing".&nbsp;In support of MAM, for their&nbsp;lack of offerings on

some of

the stuff that has been found necessary to reinforce the Rebel&nbsp;over the
years, MAM&nbsp;doesn't hold onto their airplanes long enough to

see&nbsp;most

of this and I have yet to see Robin screw up a landing
either!!!!&nbsp;</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT>&nbsp;</DIV>
<DIV><FONT face=Arial size=2>I really don't buy the "shorten the moment

arm to

reduce the loads on the cabin structure" bull. If the O-235 was supposed

to be

fine at the original engine position, the O-320 isn't going to make a big
difference. </FONT><FONT face=Arial size=2>The weight difference in

engines is

only about 30 pounds. If we were talking moving the engine in a foot maybe,
but not&nbsp;3 inches.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT>&nbsp;</DIV>
<DIV><FONT face=Arial size=2>In a (-)2.5 G (ouch!)&nbsp;landing that is only
75 pounds extra load (less than one extra RV1410 rivets shear strength).

I am

not going to try to figure out the&nbsp;load values difference on the rivets
at the top of the door post&nbsp;by moving the engine in 3" to 36.5",

from the

original 39.5",&nbsp;but will only say it's not going to make a big

difference

structurally (changes c of g significantly, but not load on door post rivets
that are in "shear").&nbsp;If you have added the float fix doubler at the

top

of the post, or have done the double staggered row of rivets up the
door&nbsp;post (so the "guillotine" effect can't get started at the top

of the

door post and shear all the rivets out right down to the wing strut attach
fitting!) you will be fine. I&nbsp;can state this with confidence
only&nbsp;because I have tried the same "testing" on my Rebel, with the

extra

rivets up the door post and an O-320 engine,&nbsp;and have determined that
this type of "landing"&nbsp;is now a NDT (non-destructive
test)&nbsp;instead!!!</FONT></DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT face=Arial size=2>'night,</FONT></DIV>
<DIV><FONT face=Arial size=2>Wayne G. O'Shea</FONT></DIV>
<DIV><FONT face=Arial size=2><A
href="http://www.irishfield.on.ca">www.irishfield.on.ca</A></FONT></DIV>
<DIV>&nbsp;</DIV>
<DIV>----- Original Message ----- </DIV>
<BLOCKQUOTE dir=ltr
style="BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT:

0px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px">

<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color:

black"><B>From:</B>

<A href="mailto:cowcam@pipcom.com" title=cowcam@pipcom.com>Peter

Cowan/Lexy

Cameron</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
href="mailto:murphy-rebel@dcsol.com"
title=murphy-rebel@dcsol.com>murphy-rebel@dcsol.com</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Wednesday, December 26, 2001

9:49

PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Firewall position</DIV>
<DIV><BR></DIV>
<DIV><FONT color=#000000 face="Bookman Old Style" size=2>In scanning the
manual (from early 90s) I see a comment that has not been mentioned that I
can recall about the reason for moving the firewall back for the heavier
engine. The reason stated is to shorten the moment arm to reduce loads on
the cabin structure. </FONT></DIV>
<DIV><FONT face="Bookman Old Style" size=2>Wayne, I don't recall you
mentioning any reinforcements that specifically address this aspect.

Have I

missed something?</FONT></DIV>
<DIV><FONT face="Bookman Old Style" size=2>Thanks</FONT></DIV>
<DIV><FONT face="Bookman Old Style"
size=2>Peter.</FONT></DIV></BLOCKQUOTE></BLOCKQUOTE></BODY></HTML>

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Wayne,
Thanks for the clarification. I am now hoping for summer first flight.
Rick D.

"Wayne G. O'Shea" wrote:

Rick, you do not replace ALL the rivets with 3/16, just the 4 at the top that are too close together to double pitch! The rest get double pitched and stay 1/8". Either well dipped RR5404 stainless or RV1410's. The Cherry rivets are a nightmare if you ever want (should I say have) to take them back out. Also, an RV1410 is about 0.6 the strength of a solid rivet, so 2 of them are 1.2 the strength of a solid (or Cherry). So you are better to use the extra set of RV1410's to keep everything looking the same, easy to work with and 0.2 stronger! Wayne

http://www.irishfield.on.ca

Greetings, All.

Update and a question.
Update.
Working hard on the cabin area of the Rebel now. Sills in place, and it
looks like next is the roof install. I have taken note of the mods to up the
size of the sills, and other parts in this area (I always forget the darn
numbers).

The question about the firewall is this: While not yet quite ready to
install it just yet, I am considering reversing it as others have done to
get the firewall lip to the inside and to have a smooth outlet for air
coming off the engine. But I am wondering, does reversing the firewall
effectively move the engine position forward the depth of the flange? If
so, does this have a noticeable effect on the cg? We plan on using a Lyc
O-235, and would really hate to have to put some weight in the tail for c of
g reasons.
So there is the question.

Thanks.

Tim Hickey
R808




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