Conference vmszoo::rc

	Hello again this is one of the two follow up's that I told 
you I would write. This one will be on the attachment of the tail
dragger skis to a tail dragger plane.

	There many methods that can be used however I have seen only two 
that are simple and problem free. The first is the solid mount method.
This is done on sheet aluminum gear.  Using a bolt,lock nut and two 
washers you attach the ski to the sheet metal gear. On either side of 
this bolt two holes are drilled to take 1/2 inch # 4 sheet metal screws.
Make sure that when you install the two screws that when the plane is at 
rest the wing is set at a couple of degrees positive incidence. This 
will help in the take off and landings.
	The second method is a flexible attachment method. This can be 
done on either the sheet metal or on wire landing gear. To start you 
will need a piece of music wire app. 36 inches long. From this wire cut
two pieces app. 5 inches in length. Approximately half way down the 
rearward slope of the axle support drill a 1/8 inch hole perpendicular
to the ski. Insert one of the 5" pieces of wire. The fit must be snug.
If the fit is at all loose insert some epoxy glue into the hole followed 
by the wire. Now with the place placed on the skis and the wing set at a 
slight positive incidence determine where a cross-member of 1/8" wire 
must be attached to the landing gear to come in contact with the front
surface of the 5" wire.  If your using sheet metal gear then a hole will 
need to be drilled in the gear. If your using wire gear then the 
cross-member will need to be wired and soldered to the gear. When 
installed this cross-member is used to absorb pressure exerted on the 
tails of the skis. Now that the wire work is done you are almost 
finished. Using a rubber band weave the rubber band around the 5" wire 
and the cross-member to tie these two together. This will keep the tip 
of the skis from rising up as the plane is flying. They will also add
flex to the skis in the event that you came in on the nose during
landing.


							Tom

	This is the third of a series of articles on snow flying and
the use of skis. The first two covered the construction and installation
of a set of skis for a tail dragger. This article will cover construction
and installation of skis for a trike gear set up.
	The construction of skis is similar to the previously described
method. The only changes are in the ski length and the location of the
mount for the landing gear. For a .40 sized ship a ski length of app.
12"  for the main gear and 9" for the nose gear seem to work best. 
Although the surface area is greater than with the two tail dragger
skis the reason is due to where the majority of the load is positioned.
The location of the landing gear mount is moved to the center of the ski.
and the hole for the axle is lowered. The axle hole should be no more 
than 3/4 of an inch off of the ski. This is done because the remaining
part of the mount is used to secure the ski in a similar manor that the
rigid mount was secured on the tail dragger set up. For wire gear that 
extends straight downward and for the nose gear we use a Carl Goldberg
landing gear strap. This is not the normal flat strap but rather one
that has a molded hump in it. This hump fits over the wire. Secure 
the main skis at a couple of degrees position incidence. The nose gear
is secured at about 15-25 degrees position. When the plane is set down 
on the snow the nose gear will sit flat. 
	If your plane is set up with metal main gear then a combination
of the Goldberg strap for the nose and the rigid mount of the tail 
dragger set up for the mains can be used.
	The only other gear set up is required when the main gear is 
made of wire. The axle part of the gear is installed through the ski
mount and secured with a wheel collar. This is followed by the 
installation of a heavy duty nose gear steering arm secured vertically.
To this arm is attached a Servo lock collar(This is a brass or steel
fitting that is secured to the servo arm. They have a 1/16" hole in them
where a push rod is typically inserted and a locking bolt of the top
to hold the pushrod securely). At the front and the rear of the ski 
center support drill a 1/16 inch hole parallel to the axle thru the 
center support. You will need a piece of 1/16" music wire. Place a right
angle bend in the wire. Make sure that sufficient wire is available to 
pass the wire thru the hole and then be secured by a 1/16' wheel collar.
Place a 1/16 " wheel collar on the wire and then pass the wire thru
the Servo lock collar. Install the wire into the 1/16"hole and secure it 
on the opposite side with a 1/16" wheel collar. Place another 1/16" wheel
collar on the wire and then measure, bend and cut the wire so that it 
passed thru the second 1/16" hole. Secure this end with a wheel collar.
Now using the two 1/16 wheel collars on the wire adjust the ski so that 
is rests at a positive incidence. This second method is a bit tricky and
can be eliminated by bending the main gear so that there is a vertical 
surface to secure a Goldberg strap.


		       ------
                       ____  \
                           \  \
                            \  \
                             \  \
                              \  \
                               \  \
                                \  \
                                 \  \
                                 |  |<------Bend Flat into wire.
                                 |  |_______
                                 |_________|


	Which ever method you choose I'm sure you will enjoy the flying
rather than looking out a window on those winter days and wishing the
snow would melt. For the beginner it is actually easier to learn how 
to land in the winter months. The density of the air enhances the glide
of the planes and reduces the likelihood of a stall.Another benefit is
that there is no defined landing strip so you literally can land just
about anywhere.

							Tom

I have this set of aluminum skis that I broke the plastic axle mount
off of.  Form what I can tell everybody breaks that off.  I would like
to fix it permanently.  Someone once told me that I should get a 
Carl Goldberg aluminum landing gear mount and use it in place of the
plastic.  Sounds good - ever since I have kept a watchful eye out for
one of these and I have never seen one or seen one advertised.  Rather
than chasing this further I thought I would ask our panel of experts.

What is the right way to fix these cheap skis.

P.S.  I know - I was the one who said Floats make better skis than Skis.
      My view now is Floats make better skis than skis that pivot.  If
      you secured skis like you did floats then that would seem to be best.

              _!_      
Bye        ----O----   
Kay R. Fisher / \     

================================================================================

    Kay,
    
    	I asume that the ski itself is made of aluminum amd that there
    is some type of mount made of plastic??
    
    What I would do would be to remove the plastic mounts and throw
    them away. Find a piece of scrap hardwood blodk app. 1" thick
    and cut two triangular axle blocks out. The drill two holes threw
    the ski and countersink these hole on the snow side of the ski.
    Use two flat head screws to secure the block to the ski.
    
    
    					Tom

    Dan, I'd be careful. You want to keep the ski tips from digging
    in but not so bad as to add to much drag. What I've seen work best
    is a kind of preloading. drill a hole in the mointing block down
    close to the ski but not so close that you can't get a wheel collar
    on the axle. Slide the landing gears axle threw the block and attach
    a wheel collar. Now with all three skiis on thw plane place a 1/4"
    thick stick under the curve of the ski and then attack a goldberg
    strut strap to secure the strut to the block. Goldberg makes strap
    for landing gear that are molded to fit around the strut. Use a
    1/4" stick under the two mains and a 3/8-1/2" stick under the nose
    wheel strut. When the plane is at rest the ski and strut will flex
    so that the ski is flat on the snow but with a little throttle the
    nosewheel will get light and won't dig in. Don't forget to wax the
    skiis.
    
    
    Tom

    I had some I made for a Sr. Falcon
    
    Mains were 18 " by 1.5" and had a stump that stuck up out of the center
    to fit the landing gear wire. I user 1/16th" music wire sticking out
    from the Fuselage and attached to the front of the ski with fishing
    line. This was set to keep the front of the ski up about 10 degrees
    when relaxed and the wire bowed when on the ground. This prevented
    "Digging in". The nose gear was 3" wide by about 8" long and had 3
    strips of 3/16th" square spruce running down it for "blades or
    runners". I used a bungie cord on this since it had to turn. I think
    the rudder was more effective than the runners on the nose ski. This
    was all done by trial and error 15+ years ago and the rule of thumb I
    used was that it had to keep the plane on top of the snow and just get
    off the snow as fast as you could. Worked for me years ago.
    
    Send me Email if you want more specifics,
    
    Jim

    Mine were for a scratchbuilt .049 control line job.  They were about
    6" long and an inch wide for the mains, and 3" long for the
    taildragger skid.  No "runners" or edging, just flat bottomed balsa
    with a sculpted nose block to keep them from digging into small
    hillocks.
    
    They pivoted at roughly the halfway point, and there were rubber
    bands pulling the skis up at about a 30 degree angle when off the
    ground and flying.  The skis had some aero drag but not enough to worry
    about in this application.
    
    -----
    
    Getting the plane unstuck was no problem; snow skis don't have to
    have a 'step' like water floats do.  Just light the fire, and give
    it "up" when it looks like it'll fly.
             
    	-Bill

    One thing I didn't mention but .2 reminded me of with "small hillocks".
    Don't walk on your runway as the boot holes are treacherous. Besides,
    maybe we won't have to worry about snow skis this winter ;^}

    Yesterday Santa brought the Daca Torq Skis I ordered a week ago. (On
    sale at Tower the rest of this week.)  These are aluminum skis designed
    to replace the wheels on 4 mm or 5/32 axles.  The design looks pretty
    good; positioning is done by a 1/16th torque rod extending from a block
    secured to the axle.  Do you want the details, Bob?
    
    Unlike the round wire used for the landing gear of the PT-40, the
    main gear of the Kadet II is sheet aluminum; a cantilevered bolt 
    is used for an axle. These skis can mount on such a bolt, but it
    would seem to be better to adapt the skis to mount directly to the
    sheet stock instead.  Has anyone done this?  Comments?

    I ran across some neat skis over the weekend. They were made from a
    hardwood rail with a hole for the landing gear wire (maybe 3/8" by 8 or
    10") with a piece of vinyl siding (the stuff you put on the outside of
    a house) on the bottom. The front of the rail was rounded up and the
    siding curved up with it so it wouldn't dig in. One such unit per
    landing gear leg, the one for the nose gear is shorter than the ones
    for the main gear. It looked like it would work pretty good and it's
    certainly cheap. 

    Joe's in Londonderry (S&H Hobbies) had them for about $8 per set (tri
    gear only) but they just can't be all that hard to make from scratch.

                     !
                   --+--
G. Schrader     o___<0>___o
                  *  *  *

    Re: .4
    
    You still need to have something to keep the front of the skis above
    horizontal. I had a beautiful takeoff with my first set and was
    thrilled to see it lift off and be airborn when all my friends were
    shivering at home. I was glad that they were home as I came in to land
    with the ski noses pointing about 45 degrees down :'0 Made a mess of my
    trailing edge as it completed the 135 degree rotation back to
    horizontal. I like the idea of using siding scraps but wonder what you
    would use to glue it onto the frame.
    
    I used fishing line and music wire stuck out from the fuselage towards
    the front of the skis. In front I used both a rubber band for a bungie
    and fishin line to limit the travel to 0 through 30 degrees above
    horizontal.

re  Note 811.4, Daca Torq Skis 

    "..... positioning is done by a 1/16th torque rod ....."

and   re  Note 811.6, 

   "You still need to have something to keep the front of the skis above
    horizontal. "

I'm confused.  The torque rods are there only for that purpose.  Are you 
saying that they are not good enough?  Were the skis you used Daca?  I 
have no experience with ski-equipped flying, but I can imagine what you 
were saying when first you realized that the skis were a problem.

    Sorry. .6 should have referenced .5 not .4 as I stated. I didn't see
    anything in the siding note that indicated something to keep the nose
    of the ski up. 1/16th is what I used and I can go back and laugh at the 
    2 rear wing sections being taken out on that first attempt (I wasn't 
    laughing then though).
    
    Twisting? Mine weren't wide enough. I ran the square spruce down them
    to keep them from fluttering. (from other discussions, maybe you could
    just laminate some carbon fiber top and bottom) I had a lot of fun
    using those skis. Just got to be careful when the long grass starts
    popping through and setting up trip wires to snag them. I've also heard
    of people using flying boats and pontoons too.

< Note 811.8 by TYCHO::REITH >

    These didn't have anything but the skis and rails but you're right, some
    additions would have to be made to make them work right. What cha want
    for $8 anyway? 8^)

                     !
                   --+--
G. Schrader     o---<0>---o
                  *  *  *

    There's what appears to be a good article on building, mounting
    and using snow-skis in the latest issue of Model Aviation.  Had
    I any use for them, this looks like a good/simple route to go.
    You might want to read this article.    

      |
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

    There is another way- I have been flying off the snow for years
    with my Gee Bee floats. All I do is remove the water rudder and
    fly. I have been using the large version on a 40 OS 2 stroke with
    a 50 inch span. They work very well on both snow and water.
    
    
            Bob
    

    Hi, been on vacation for a week. I just wanted to add that I have
    an article of ski construction if anyone is interested?
    
    
    Tom T

    Out of the box as shipped, the Daca skis have problems on the Kadet II.
    
    First, the axle hole on a ski is only 1/2 inch above the ground.  When
    you simply replace the wheels with the skis, the 10x6 prop has too
    little clearance.  The OS 40 engine tried to make its own clearance,
    mowing the snow as it taxied, but that seemed unfair to the model; we
    hand launched.  Flying and landings were perfect except that, 
    
    Second, near the end of the landing runout the nose ski broke through
    the slight crust.  The landings were dead-stick, so it wasn't a matter
    of the prop breaking the crust or causing down drag. The penetration
    seemed to be the result of pressure loading, not grass snagging, but
    there may have been irregularities in the snow surface contributing to
    the break.  It did happen at the end, long after the ski had been
    running on the surface --- once 3 feet before termination, once at 10
    feet.  The main gear always stayed up.  The nose ski may have to be
    more wide than the current 2 3/16 inches, and 
    
    Third, the method of setting the pitch angle of a ski is not very good,
    although the torque rod mechanism for allowing pitch variation is fine.
    The problem is in the attachment/clamping/pitch-setting of the ski on
    the plane.  The ski is designed to simply replace a wheel; two set
    screws jam the mounting block onto the existing axle to set the nominal
    pitch angle.  The accidental torques applied during handling are beyond
    what one should expect from two set screws on a 5/32 axle without a
    flat spot, but a flat spot would itself predetermine the pitch angle. 
    
    I intend to fix the clearance problem by replacing the plastic mounting
    bracket with much higher balsa block.  For pitch maintenance I'll use
    something close to the music-wire-from-the-fuselage technique.