The Murphy Builders Site

Hi Wayne,
There is snow on the ground so I am making my annual trip to your website to
look at the photo of the Rebel on skis--got to keep motivated!

I couldn't find any reference for cost of skis. I am interested in
purchasing some, but obviously I am not in any rush. Could you get me some
pricing info. and then perhaps I can get on your waiting list--I understand
it's easier to make several skis at a time and I could just wait till your
next production run.

Ski flying will be new to me. You had mentioned in past posts that these skis
could land in deep powder and were wheel penetrating skis; how well do these
work on hard pavement? Do you drag the back of the ski? Is there a
replaceable rub block on the trailing edge of the ski? Do you put plastic
bottoms on all of them? How do they mount on spring gear? Should I use
longer bolts in the gear saddles to allow for future attachment of rigging?
I did install the aft attach point for the bungee gear to use if needed.

As tires are the primary shock absorption for the aircraft, how hard on the
airframe, is landing with skis as compared to floats? I am trying to figure
out how much to beef up the airframe from stock configuration for ski
utilization. At this time I do not plan on using floats. For reference, I
am using a Jabiru 3300 engine, weighing approx. 180 lbs., wooden prop, and
basically a very light weight airframe. Aircraft empty wt. is a big concern
to me and I am trying to build it as light as possible, but don't want to
compromise strength for ski use.

I was also looking at your firewall reinforcement plates. I am thinking this
might be overkill for my situation. I also noticed in the photo that you
install motor mount bolts with the nut behind the firewall. My manual shows
the nut on the forward side of the firewall. I am assuming this is to allow
the bolts to be changed as they don't appear to be removable if installed per
MAM. I plan on using NAS 4 bolts; are number 4 bolts removeable from the
back side? The bottom half of my engine mount does have cross bracing; the
top does not. I had even thought of installing a cross brace on the top half
of the motor mount itself as I don't have any mags back there. This cross
brace could be installed later if needed. The cross brace could even use the
top two motor mount bolts as an attachment point. Do you use ST31 or ST28
for the two piece cross brace recommended by MAM? Do you put the piece on
the front of the firewall under the mount? It would seem that this would
shift the thrust line, unless you shimmed the other three to match.

As always, thank you for your time and interest in supporting Rebel builders!
No rush to respond to this--just at your convenience. I know this is a lot
of questions, but I know you would be the person who might have all the
answers. Hope your recovery is going well and you are soon up to speed and
back out in the shop!

Thanks again,

Jim R254



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Yah! That @$#% snow is on the ground here too, but hope it goes away again.
Really want to get my re-honed cylinder broken in before I have to put the
skis on, as taxing on skis can really heat up an engine quick and don't want
that on my refurbed chrome cylinder. Every time in the last couple weeks
that I have been up to the 2 hour flight and have had her preheated/ready to
go, the weather closes in and negates that thought. Kind of like my internet
provider crashing last night 10 minutes before auction end on a Scott 3200
tailwheel , that I lost over $5 because I couldn't get back on line! Brand
new and went for $395US, compare from $549 at ACS to $659 Wagero! (Which one
of you buggers bought it out from under me!??!?!?!?)

There is no reference on our web site, of cost, for a set of my Fixed
Penetration skis for the Rebel as the price would be outdated by the time
someone wanted a set. There is not a huge demand for skis and I don't
assembly line build them as you are suggesting. They are a one set at a time
item and there is a lot of work involved in building a set and, depending on
which gear you have, on how to pick up pivots on each side. The spring gear
is easy as you can bolt a pivot stub on the inside using the 4 axle bolts
and a simple axle extension threaded onto the axle to pick up the outside.
The "bungee" gear system requires fabricating a pivot point that is dropped
below the axle block on the inside. This then requires a link on the axle
extension on the outside, to drop the pivot point down to the same height. I
"out sourced" these mounting items when I built my own skis in 1995 and they
cost me over $400 Cdn for the set, just for the pivot points and axle
extensions. An approximate cost for a pair of these skis, at the present
time, is around $5000 Cdn complete with rigging cables, pivot mounts,
plastic bottoms etc. I usually need the aircraft to take measurements etc,
because everyone of these Rebels seem to be different in some way on wheel
assembly! That could be worked around with digital pics and some careful
communication at each end! Sounds like a lot of money, but considering
Kheller was charging OVER $8000Cdn for a similar sized set for a Citabria in
1996, it's a great deal for a 100+ hours of labour and all the materials to
build them.

As for pavement, just landing as normal in the summer. I do like to slow her
down a little more than usual so I'm not slamming the skis tail down, but
they work great and the skis give you about 18 square feet more of "wing" to
allow a little slower flight. Just like Amphib floats, best of both worlds,
but no need to cycle the gear!!! You just have to watch when you land on a
wet runway and throw all the water up under the ski. The next landing in the
snow can be VERY interesting with the large icicle underneath! Requires FULL
power and FULL back stick to keep from going on your back, and it has to be
a "programmed" reaction or you're too late! On the tails of the skis I run a
snowmobile track idler wheel about 6 inches in diameter. I tried smaller
ones before, but they spin way to fast when you land at 40 MPH and fly
apart. The "boggy" wheels work great, as they are designed for the speed and
the load inside the skidoo track! I build my skis with just a hole through
for the tire. This can help create the above icicle problem and or mud
problems under the rear of the ski. If you are into mud quite a bit you may
want to have the ski cut out behind the tire all the way to the back so the
crap gets thrown clear. This does cut down on the ability to sit up on top
of the powder though and would require two "tail" wheels (one on each side)
instead of one in the center of the ski as I have done!

For mounting the check cables I wouldn't play with your spring gears saddle
bolts. You could rivet/bolt a forward attach bracket, for the check cable
and tension bungee or spring, to the forward door post/fus-11/70 area or
remove the gear saddle fairing in the winter and mfg a bracket that clamps
over the gear leg stub between the saddle and the main gear attach bolt. The
rear check cable could come up to this same point or, for less tripping when
getting out, attach to the bungee gears rear drag brace attach fitting that
you installed.

They say if you are ever going to damage you aircraft you will do it on
skis! God knows I did and that's were some of the reinforcing suggestions
come from but, that said, it is the BEST fun you can have with your Rebel!!!
Everything white is a runway!!!! Yes, the tires act as a major item in shock
absorption when flying on pavement, but the spring gear legs or bungee/die
springs are doing their part in this also. If flying penetration skis and
landing on a hard pack or ice covered lake, you are back to the tire doing
their job. In snow, it's like landing in a bunch of feathers! If you do most
of the previously discussed upgrades on the list you will be fine. I'm still
flying with .020 door sills and the stock Fus-25's and 26's. If you all have
your jaws back up in place now, to continue reading, I will add that they
are getting puckered and wrinkled to the point where pretty soon I will have
to bite the bullet and listen to my own advise and swap them out. It's just
the paint matching the holds me off until it really has to be done and why I
keep telling everyone to do these upgrades! Most aren't theory, they are
suggest at the "expense" of my own personal experience!

Jim, I would rather you went overkill and did my plates (or similar with
your own material), then have you kill your aircraft with the firewall
buckled and mounts pulled together. I didn't think they were really
necessary with the light 912 engine either but, after seeing a firewall
after the prop loss on a "pals" Rebel, I've since changed my mind. I don't
know what picture you looked at, that gave you the idea I installed the
mount bolts with nut inside the firewall (as all I have done have the nuts
outside, but may not be a bad idea with the newer two piece engine mount
fittings (that I hate!). The old one piece fittings were nice as the bolt
just slipped in. The new ones require installing the bolt prior to bolting
the fittings together. Either way that you install the bolt it's in tension,
so shouldn't matter. Just easier to verify the nut is still safetied when on
the engine side! Your use of the NAS4 bolts sounds okay (160,000psi vs
125,000psi AN's). The 912 mount just used AN4 bolts and to really scare you
the Zenair CH701 uses AN3 bolts to hold the motor mount on the airframe!! If
you have enought "meat" on you mount bushings diameter, I would just go up
to the 5/16 AN bolts that the Lyco mount uses for piece of mind!

I've only done the MAM "float fix" channel on one new fuselage, at the
request of the customer, using .032 (same as ST-28) in combination with my
plates. Yes I took it right to where it sits under the engine mount. There
is enough flex in the mount arms that I don't think this .032 under one arm
will change the thrust line significantly. If you were worried about it you
could just buy three AN970 penny washers in the "L" version, that should be
.032 as a normal one is .063, and slip them under each mount arm. Or just
make a shim from .032 sheet to be sure they are all the same.

Enough bla-bla-bla from me, hope that helps you out!

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

----- Original Message -----
From: <Jims170A@cs.com>
To: <murphy-rebel@dcsol.com>
Sent: Sunday, December 16, 2001 11:38 AM
Subject: skis / Rebel

Hi Wayne,
There is snow on the ground so I am making my annual trip to your website

to

look at the photo of the Rebel on skis--got to keep motivated!

I couldn't find any reference for cost of skis. I am interested in
purchasing some, but obviously I am not in any rush. Could you get me

some

pricing info. and then perhaps I can get on your waiting list--I

understand

it's easier to make several skis at a time and I could just wait till your
next production run.

Ski flying will be new to me. You had mentioned in past posts that these

skis

could land in deep powder and were wheel penetrating skis; how well do

these

work on hard pavement? Do you drag the back of the ski? Is there a
replaceable rub block on the trailing edge of the ski? Do you put plastic
bottoms on all of them? How do they mount on spring gear? Should I use
longer bolts in the gear saddles to allow for future attachment of

rigging?

I did install the aft attach point for the bungee gear to use if needed.

As tires are the primary shock absorption for the aircraft, how hard on

the

airframe, is landing with skis as compared to floats? I am trying to

figure

out how much to beef up the airframe from stock configuration for ski
utilization. At this time I do not plan on using floats. For reference,

I

am using a Jabiru 3300 engine, weighing approx. 180 lbs., wooden prop, and
basically a very light weight airframe. Aircraft empty wt. is a big

concern

to me and I am trying to build it as light as possible, but don't want to
compromise strength for ski use.

I was also looking at your firewall reinforcement plates. I am thinking

this

might be overkill for my situation. I also noticed in the photo that you
install motor mount bolts with the nut behind the firewall. My manual

shows

the nut on the forward side of the firewall. I am assuming this is to

allow

the bolts to be changed as they don't appear to be removable if installed

per

MAM. I plan on using NAS 4 bolts; are number 4 bolts removeable from the
back side? The bottom half of my engine mount does have cross bracing;

the

top does not. I had even thought of installing a cross brace on the top

half

of the motor mount itself as I don't have any mags back there. This cross
brace could be installed later if needed. The cross brace could even use

the

top two motor mount bolts as an attachment point. Do you use ST31 or ST28
for the two piece cross brace recommended by MAM? Do you put the piece on
the front of the firewall under the mount? It would seem that this would
shift the thrust line, unless you shimmed the other three to match.

As always, thank you for your time and interest in supporting Rebel

builders!

No rush to respond to this--just at your convenience. I know this is a

lot

of questions, but I know you would be the person who might have all the
answers. Hope your recovery is going well and you are soon up to speed

and

back out in the shop!

Thanks again,

Jim R254

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