SKI'S -- Suggestions--LONG article!

SKI'S -- Suggestions--LONG article!

Post by dgamb.. » Sun, 24 Dec 1995 04:00:00



        Since so many pilots responded to my post about skis, (my
mailbox runneth over! hehe) I decided to post some suggestions  to
this group for those who may be interested.

        Some background;

        I struggled with ski design for years till I came up with this
 setup , and will share the setup with a few cautions. Some of the
 "details "  ARE   EXTREMLY IMPORTANT!.   IF  you deviate even
 a little bit they will not work nearly as well as they should !!  Some
things have been tried and tried again only to come back to these
design details. (and yes, I was serious about my Wayfarer climbing
 snowbanks, done it many times)

        For MOST FUN.........................

        The Model :

        Should be taildragger - don't even consider a trike gear if
you will be in soft snow!

        Should have an exposed engine (removing cowls, small
screws, spinners etc. in freezing weather to tighten a carb -----
 GRRRRRRRRRR!)

        Use a GOOD tail ski !!   --- It is NO FUN  trudgeing through
2ft of snow to turn a model that won't handle (turn) on the snow .
 --Not to mention how your tracks ruin the runway for yourself and others.

        Use a model that can be completely assembled in the
 warmth of home. (*** bands, wing struts, small screws,-------PAIN !  )

        Model should be .40 size or larger, smaller planes
 (with smaller skis) just don't handle snowmobile tracks, footprints
(snowbanks :)  )   as well.  My fav is a .60  powered Wayfarer (48"
biplane, -fits in my station wagon fully assembled)

        Leave the tuned pipes home! -   Temp and density altitude
 are probably VERY different from when the pipe, prop and fuel etc.
 were set up--    just more friggin in the cold!

        Use (several  <G> )  WOOD props!   Plastic props at 13,000
 rpm in -15 C (!)  (shudder! )

        Watch your batteries- - they will last about 1/2 the normal use
 time at freezing temps.

        OTHER HINTS :

        You are now flying in an enviroment considered hostile to
 humans  -- don't fly alone !

        Wear boots with deep tread - slipping, falling and putting
 your hand into the prop is no fun, (nor is sitting on your plane) !

        Run the after run oil out of the engine at home (engine will
 start easier when warm than cold with that heavy oil in it.)--- then go
 to field.

        WD  40 is good starting fluid! Has propane in it .
----------------------------------------------------------------------------------

        For those who have my drawing............................

        -- DO NOT OMIT----!!!!!

        -- The square portions on the brass runners,  Your model
 MUST NOT be able to slide backwards on ice/crust.   Tail feathers
 DO NOT slide into frozen snowbanks well !  (trust me on this one! )

        --The brass axel bushing.   The hardwood will swell when it
 gets wet (it will!)  and seize on the axel without this insert.

        --The screws!   Don't depend on the glue joints alone to stay
 while you are thrashing these skis across ice ridges at 30 mph !
Some epoxies get brittle in cold temps.

        --The white topside paint.  Dark colours get warm in the sun
--- melt snow underneath --wet snow freezes to skis.  GRRRRRRRR !

        -- The forward control cable.  You MUST prevent the ski
from tucking under if the *** band breaks (carry spares)     AND
 the length of this cable IS CRITICAL to you models ability to  cross
 footprints and snowmobile tracks.  SET THIS CABLE LENGTH AS
PER THE DRAWING -It MUST come tight PRECISELY as the  tail
ski comes down to a 3-point attitude !!!

         MORE--------

        The axel position MUST be  back  at least 50% of the length
 of the flat portion of the ski. 50 % is the absolute minimum !!!!   I have
been able to operate in soft powder snow where the skis sank till the
 bottom wing rested on the snow,  prop in the snow, and these skis
 "climbedup and out" for take off .  This WILL  NOT work with the axel
further forward .

        DO NOT USE  cross country ski wax!!!!!!  This stuff is designed
to "stick"  and "slide" and " stick" it will !!   The best I have found is
Johnsons Paste Floor Wax  -  not very common now -  was used in the
 past to kill and cripple people  on wet tile floors. Very good in the
"slide " category.

        Use steel u-control leadout wire for control cable, crimp and
solder in small brass tube to connect ends. It gotta be STRONG ! Perfect
 still makes this- "B-C" size, stranded cable.

        Rear control cable is adjusted to control the "toe up" in level
flight  of 3-5 degrees.

        *** bands are light weight --- just strong enough to raise the
 "toes"and keep them up in flight.

        NOW................

        I KNOW they are heavy and draggy !   BUT-  I consider it a
pain to***around with riggin on a nice summer day -  I can't print
 what I think about it at  -10 C.!  These ideas are acollection of many
 trials and errors, and the input of many people over several years.
 Last winter there were two of us at our field with this ski design, rigged
 EXACTLY as shown. The snow had a thin crust. :(   We flew several
flights, crossing tracks, broken crust, drifts and ridges with little
problem without failures. (Other model was a 60 Ace Bingo)  Five other
 planes were disabled rather quickly- two never got up, two requiring
extensive repair after a ski hooked the crust and tore the LG out of the
 model.  Another had our same skis, but broke the ski  after hooking the
crust (he had omitted the  screws! - epoxy glue joint failed-  we DO
 save our good 'poxy for motor mounts don't we?) My skis are a
 DOUBLE thickness 2x 1/16 ply and are VERY rugged.

         Whoooo - this got long ! -   hope this may be of help to those
 who would like to try! Comments and suggestions very welcome!!

        BTW -- can send plans if UR mailbox will handle   2 .bmps,
 760 k each . Open under "Paintbrush."