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Fin offset 1/2" or 3/4" or more?

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hibbs

Fin offset 1/2" or 3/4" or more?

Post by hibbs » Fri Feb 17, 2012 8:34 pm

I am going to use a 140 hp LOM with a Warp drive on my Rebel. I am
about to offset the fin. My old manual says 1/2", the new manual says
3/4". I plan to offset 3/4" unless someone has experience that says
even further offset is needed?

--
Best Regards,

Scott Hibbs
hibbs@pacifier.com
Rebel 300R
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hibbs

Fin offset 1/2" or 3/4" or more?

Post by hibbs » Fri Feb 17, 2012 8:34 pm

I have had feedback from a couple of people I respect. I will either
put in no offset or 1/2" at most. Thanks for the help gentlemen, this
is quite a forum.

BTW Wayne, I performed the Service bulletin 080520Reb today, thanks for
the effort there.

Now to decide how to route the fuel lines. I am tempted to drill a 1/2"
hole in the center of the FUS-5 carrythroughs to run a single line
forward under the floor. I have asked Murphy for some formal advice on
that idea.

--
Best Regards,

Scott Hibbs
hibbs@pacifier.com
Rebel 300R
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Wayne G. O'Shea

Fin offset 1/2" or 3/4" or more?

Post by Wayne G. O'Shea » Fri Feb 17, 2012 8:34 pm

--------------------------------------------------------------------------
Your following message has been delivered to the 170 members of
the list murphy-rebel@dcsol.com at 19:21:19 on 10 Dec 2000.
--------------------------------------------------------------------------


Scott, there are huge amounts of "argument" over this already in the
archives!

In my experience with all the ones I have flown, the ones with NO fin offset
fly perfectly straight (in cruise) with hands off the stick and feet flat on
the floor. On two of them (Howard's and Bob's) I pegged the wings in place
when the holes were still undersize and using a digital level determined how
much (if necessary) the full size holes needed to be offset to make sure the
two wings were exactly the same in regards to angle of attack, as you can't
adjust them after you have drilled the attach holes to final size like you
can on a Cessna. Therefore there is not a "low" wing helping to make up for
what offset WASN'T put into the fin mounting. Some builders have carefully
jigged (and used bolts in) the 9 - 3/16th holes that attach the fin so it
can be moved a half inch from the position you chose, by unbolting and
drilling 3 more holes if you find you are turning left or right, OR want to
change to an engine that turns the other way!. (you also would need to make
new fin to stab fairings though, once you move the fin).

FWIW, my personal Rebel turns left and my fin <IS> offset by a 1/2" to the
left. This is when I learned to be a little more leery of factory holes,
etc, on something as critical as an non-adjustable wing attach fitting, as I
found that my wings did not have the same angle of attack after being
mounted! It still stalls straight ahead, like a roller coaster ride (mush,
fly, mush, fly), and has no bad habits so I just riveted a trim tab on the
right flaperon. I used a piece of my first moulded windshield, from when I
found out the hard way that the door post needed a double rivet row to hold
it together, that actually had the right curve in it to work perfectly and
the bonus is that it won't slice someone's head open if they walk into it!

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

----- Original Message -----
From: "hibbs" <hibbs@pacifier.com>
To: "Murphy Rebel Builders List" <murphy-rebel@dcsol.com>
Sent: Sunday, December 10, 2000 5:28 PM
Subject: Fin offset 1/2" or 3/4" or more?

I am going to use a 140 hp LOM with a Warp drive on my Rebel. I am
about to offset the fin. My old manual says 1/2", the new manual says
3/4". I plan to offset 3/4" unless someone has experience that says
even further offset is needed?

--
Best Regards,

Scott Hibbs
hibbs@pacifier.com
Rebel 300R
*---------------------------------------------------------------------------
--------*
*---------------------------------------------------------------------------
--------*

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Bob Patterson

Fin offset 1/2" or 3/4" or more?

Post by Bob Patterson » Fri Feb 17, 2012 8:34 pm

Finally got my email working again .... sort of !!

FWIW, Scott, I'd go with NO offset - it will make it easier
to install fairings, mount the fin, and ... possibly later, change
over to a different engine should the need arise .

There's lots of discussion about this in the archives, and
I know that the former V-P Engineering at DeHavilland decided to
build HIS Rebel without any offset, and it flew just FINE !!

Please keep us posted on the performance, CofG location, etc.
with the LOM engine - there were several builders here who were very
interested in using it a few years ago ...

......bobp

---------------------------orig.---------------------------------------
At 02:28 PM 12/10/00 -0800, you wrote:
I am going to use a 140 hp LOM with a Warp drive on my Rebel. I am
about to offset the fin. My old manual says 1/2", the new manual says
3/4". I plan to offset 3/4" unless someone has experience that says
even further offset is needed?

--
Best Regards,

Scott Hibbs
hibbs@pacifier.com
Rebel 300R
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---------*

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