The Murphy Builders Site

Hi Ryan !

Certainly, running a Finite Element Array computer simulation is another
way to evaluate changes in airfoil design - however, the simulation is only
as good as the programming, and the experimental test data used to feed
the program. I believe there was considerable wind-tunnel testing done
to gather data for the Beaver and Otter wing - and the improvements brought
to that wing by the Barron STOL kits are well documented. I don't know if
the Beaver is an exactl 4415 airfoil, or whether it, too, was modified.

The Rebel wing airfoil and the Moose airfoil are identical - ribs being made
on the same dies AFAIK. The airfoil, according to Mr. Murphy, from his
seminars at S n F, is a modified 4415 - the modification, as I recall, was to
slightly flatten the bottom surface, for easier construction. The Moose
airfoil does not change shape consistently throughout the length, though,
like the Rebel does, with flapperons, in landing and takeoff configurations.

From my recollections of conversations with Angus, the McKenzie cuffs
are "scaled" from the Beaver design, and the Moose cuffs are exactly the same
shape, just longer, and in more sections.

You have hit on one area that most likely accounts for some differences
in the relative effectiveness of the cuffs on the Moose vs the Rebel - the
round-engined Moose is very nose-heavy, and, according to Mr. Barron,
would greatly benefit from similar thrust-line modifications to those he has
done on the Beavers !

I agree that the McKenzie STOL kit may not be absolutely the optimum
shape for all configurations of the Rebel and Moose, but it certainly works
well enough on my Rebel, and I'd be loathe to pay .... say, $50k extra ....
to have it optimized further ! ;-^) :-)

I can understand the reduction in stall speed on the Moose, with the
new Murphy tips - they increase the wing span, and area. Because they
also increase the aspect ratio of the wing, a small increase in cruise
speed is logical, as well. A very worthwhile addition to the Moose !

Since the VG's work so well for you, and cost so little - I'd have to agree
that they look like the cheapest, easiest solution. As you said, that's
what's so great about homebuilding - everybody gets exactly the aircraft
they want !! :-)

.......bobp

-------------------------------orig.-------------------------
On Sunday 09 January 2005 12:27 pm, Ryan Mowat wrote:

Wayne and Ken,

The CNC rolls in the Kelowna area that do the Barron Cuff is the company
that I sent the cross section drawing of the Moose wing to for analysis.
Basically the design that needs to be done to optimize the cuff performance
with the plane can be done on computer Finite Element Analysis (FEA) rather
than wind tunnel experimental work. However, final aircraft flight testing
should also be done to verify FEA results. I understand that the Rebel
cuff was a good educated guess and that it works really very well - it may
be close enough and further FEA beyond the first guess for the shape may
not be necessary. The MOOSE application is different. The so called Dave
Barron cuff for the Moose has never been engineered - just a guess was done
- and my belief is that this guess of the shape for the moose is not
optimal - further engineering could be done on its shape and extent of
droop. The beauty of experimental airplanes is that you can spin a cuff
off and try it if you like, but my approach would be to have proper FEA
done before I go the the trouble of flight testing. The basic concept is
sound and I believe the fellows in Kelowna have the expertise to do it
correctly if someone was willing to offer a moose for a test bed.

I was told by MAM that the airfoil on the Moose is a modified Beaver
airfoil - I have not verified this myself, but I understand a slightly
different airfoil was choose to increase cruise speeds - maybe someone at
MAM could provide specific details unless they consider it a technical
secret. I have made my own Cross Section CAD drawing of my wing and it
would not be hard to compare it to other airfoils if someone was
interested.

I have spoken to both pilots of the Cuff installed MOOSE aircraft and my
conclusion based on their test flight descriptions was that the cuffs that
they have installed are not optimized to the extent that I would put them
on my MOOSE. There are other factors to consider when looking at the cuff
installation - i.e. wing attachment angle and engine thrust angle, these
also contribute to the performance of the cuff.

I have offered my Moose to the guys in Kelowna but have never followed up
with them because it flys so nice now.

Ryan Mowat.



On Sun, 9 Jan 2005 12:06:47 -0500, Wayne G. O'Shea wrote

I have no input for VG's or the Mckenzie cuff...but Ryan this "not a
true design" comment has me baffled. The McKenzie cuff is being
rolled on the same CNC rolls by Dave Barron as the Beaver cuff that
costs mega bucks more. The "it is just a spin off from the Rebel or
Beaver"?? The Moose wing is identical to the Rebel wing...just three
feet longer and they are both copies of the Beaver airfoil for all
intensive purposes.

Cheers,
Wayne

----- Original Message -----
From: "Ryan Mowat" <rmowat@forge-industrial.com>
To: <rebel-builders@dcsol.com>
Sent: Sunday, January 09, 2005 12:45 AM
Subject: Re: VG's - Rebel

Bob,

I understand that the McKenzie Stol Kit for the Moose is not a true

design

for the actual Moose wing - it is just a spin off from the Rebel and

Beaver

ideas with no engineering analysis. I have sent in a CAD drawing of
the wing cross section to the fellows in Kelowna with the intentions of

having

a

real design completed and installed on my plane. However, after

installing

VG's and new MAM wing tips I have really no reason to - the plane flys

great

now. I would suggest installing VG's before leading edge cuff on a

Moose -

the price is good and they tape on for trails and once your happy you
can glue them down for good. I installed the wing tips first and found
great stability improvements, 6 knots stall reduction at gross and if I
wasn't seeing things a 1-2 knot top speed increase. Then I installed
the VG's,

and

got another 5 knots reduction. My moose on floats stalled at 57 knots
at gross before the wing tips and VG's - At 57 knots I figured I'd kill
my

self

on a water landing with engine out - very heavy nose. With tips and
VG's stall is down under 45 knots at gross and I have done engine-out
test on wheels - works fine. In ground effect I am off the water under
50 knots

now

and about 12 sec compared to 19 sec (Sea level, gross, 20 C).

I think there is one Moose with the so called McKenzie cuff in Vernon
and one in Phonix with both VG's and Cuff installed. The guys in
Alaska were trying to come up with a cuff - any updates?

Ryan Mowat



On Sun, 9 Jan 2005 00:01:08 -0500, Bob Patterson wrote

recommendations

such

a

asked

placement

improvements

does

say

placement

is

from

something
The

:
:-)
:

wind-

disaster

!

couldn't

McKenzie

made

for
possible

and

in

wrote:

Do

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