Purchasing the
correct skis is an important decision for getting the most fun out of
winter flying.
Answering a
few simple questions can make ski selection much easier, especially if
your plane falls in the overlapping area between the large and standard
ski weight recommendations, or if you think you might like to go outside
the recommended ranges to enhance flight performances for your region's
common snow conditions.
1. What type of flying do you
want to do? Do you fly aggressive aerobatics, or just like
to relax and do some slow touch and go's.
2. What kind of snow conditions
are most likely in your area? ...Cold and fluffy, or
dense and wet? Sparse and grassy, or will you be standing
atop 3 feet of ice on a frozen lake?
3. How much power and lift
does your plane have? Do you have a big engine with large wing area
and high lift, or do you have moderate power and a small wing area?
4. How much does you plane weigh?
5. How fast will your plane be
traveling?
Carefully assess you answers from the
above questions with these facts in mind:
-
Larger, heavier, planes taking off
in deep wet snow will benefit from more floatation on the
snow given by larger skis, and need more power to perform well
in it, (remember water, weighs over 8 pounds per gallon
and wet snow ,may collect on the skis during takeoff! At least until you can
roll it over and dump it off.).
-
In Contrast, light planes on very
cold, hard packed snow, need less power than they do in
the summer to take off, since cold air generates more
lift, more power from your engine, and friction is
virtually eliminated. Therefore smaller skis are perfect for
these conditions.
-
Remember, Fast planes
flying extreme maneuvers are more affected aerodynamically
by larger skis than slow planes flying gentle maneuvers. So if
performance in the air is preferred to performance in the snow,
smaller skis would be the better choice.
-
Note: MMP acknowledges that water
floats have been known to be used in the winter. While they
certainly can be used on snow, you will inevitably pay the
penalties of very poor aerodynamics, and weight gain, and suffer
almost certain permanent damage to the floats from the ice. Ice
is rock hard, and often sharp as glass, and temperatures make
plastics and foam brittle.
Proper installation
of the MMP Snow Skis is important for maximum performance:
1. MMP Snow Skis should always
be installed parallel to the wing! Due to the leaf spring
design, if they are installed with the tips nose high, it will
cause the springs to influence the airframe into a nose-down
condition on takeoff and landing. It will also cause
unnecessary trim changes! They are self centering skis, NOT free
floating bungee skis, and should not be installed nose high.
2. The only exception is the nose
gear ski on tricycle configurations. Due to the spring coil in
most nose gears, the nose gears themselves, tend to flex
rearward. When this happens the ski tends to rotate slightly
nose down, reducing flotation. So a slight nose up installation of the
nose ski ONLY, is desirable.
3. IMPORTANT! A tail ski is not
recommended (or supplied) as it can easily grab snow and ice and
tear the rudder off of the plane, and that is a bad thing. The tail
wheel will provide ample steering, and the rear of the fuselage will
provide the minimal flotation that is necessary on the snow.
4. CLEAN and DRY! Your axles NEED to be
CLEAN and DRY when the skis are installed! The set screws are
relying on a tight, slop-free, friction fit to hold the skis tightly
on the axles. Oil reduces friction. 'Nuff said. Therefore,
fuel and oil dripping, and soaking, on nose gear axle is something
that can undermine the skis otherwise premium performance! Remove
any wheel and axle lubricant before installing skis as well!
5. Make very certain that your
AXLES ARE TIGHT! Use of (5/32") axles with a larger
mounting stud nut is highly recommended when using aluminum or
fiberglass landing gear. If the ski holds tight, but the axle spins,
you have undermined the design!
6. The set screws are soft stainless
steel and will deform slightly to the contour of the axle, this
helps them to grip the axle. So do not back the screws all the way
out after they have been installed on an axle, or you can damage the
threads in the lock block. Don't over torque the set screws.
However, MMP skis are designed with satisfaction as the primary
design parameter, and things just happen sometimes. So if you do snap off a lock
block screw, these skis have been designed with enough material so
that the screw can be extracted, and if the threads are damaged in
doing so, they will accommodate an oversized set screw. (They are
designed to be repairable. MMP feels more things should be designed
that way!)
7. If your plane falls in a weight
range where you prefer using 1/4 inch axles, the MMP skis are
designed to accommodate
being carefully oversized to match the 1/4 inch axles. BE CAREFUL,
and make as close of a tolerance fit as possible. Sloppy
over-sizing of the axle holes is a perfect way to reduce the
tight friction fit required to hold the skis tightly on the axles!
How Cold Is It
outside today?
Why Does It Matter?
Engine performance, flight performance,
and personal performance are all affected drastically by the outside air
temperature!
Engine Starting. Getting an
alcohol engine started in temperatures below freezing can be the
biggest challenge of winter flying, but there are some good tricks:
1. First,
use a higher nitro-methane percentage in your fuel.
2. Second, use propane to get
the engine started. To do this you can carry a small propane torch,
or propane soldering iron with you. Simply open your carburetor and
turn your propeller while letting the propane fumes enter the
engine, thus, priming the engine with propane and with fuel too.
Then, start the engine as you normally would. Often it will run for
a while and quit.
3. Repeat the process. This
can take 3-5 cycles to generate enough heat inside the engine before
it will run solely on the alcohol fuel. Older cans of
WD-40 used Propane as the propellant and therefore can be
sprayed into the carburetor to prime the engine as well. The benefit
of this method, is that it lubricates, and loosens any sticky oil
inside the engine as it primes, making it easier for the starter to
turn the engine. Ether, or other starting fluids should be
avoided as they dry the internal engine parts. Ether
and starting fluids do
not react with a platinum glow plug very well either.
For whatever unscientific reason,
24 degrees Fahrenheit seems to be the dividing point between "Stubborn",
and VERY Stubborn starting engines.
4. Your engine will need to be
Tuned Richer. Cold air is more dense and requires
more fuel. Opening your needles slightly before you even
try step one is a good idea. It will need to be tuned richer anyways, so
go ahead and open the needle 1/4 or 1/2 a turn before you even try
and start it (at least the first time you go out), and don't forget to richen the idle mixture too!
5. Your engine WILL make more
power than usual, however will usually produce less RPM due
to the dense air loading the propeller. This defies you senses, but if
you listen to the propeller barking in the cold air, you will
realize you are making some serous power!
6. Restrain your plane. Pound a
screwdriver into the ice and tie your plane down! Skis are slippery!
...'nuff said!
Equipment and
Airframe Performance.
This
is some very good, and very important information here!
1. Cold destroys battery duration.
Cold Ni-cad batteries don't last as long. Period. Check your
battery voltage before each flight!
2. Most coverings get brittle
in the cold. Ice chunks can do damage, inspect your
covering frequently. Snow skis can shoot ice chunks, just like car
tires can shoot rocks. (Remember tidily winks?)
3. Nylon wing bolts become fragile
in the cold. Keep them in your PANTS pocket (it is
warm in there), (note, NOT your jacket pocket, it is cold in there),
until you are ready to install them. Carry spares. They
usually break off at the head, during installation if they are
frozen, because the holes in your wing are never drilled
exactly square to the head. They will not flex if they are
frozen! However, once they are in place, they seem to take a set,
and are fine for use. Don't twist them to check them later, they do
break on removal as well sometimes.
4. 10% less control throw in cold
dense air is recommended. Cold air is dense, you will
have LOTS of power, lots of lift, and
LOTS of control authority. Adjust to taste.
5. Nylon or plastic control rods and
clevises;...NEGATIVE. Replace all of them with metal ones!
(see " Nylon Wing Bolts" above.)
People Performance!
Hear me now, or hear me
later!
1. Check the wind, and temperature.
Cold, dense air generates more lift. More importantly,
the cold wind has a greater effect on your plane in
the winter. If your skills, or airplane, are limited to 20 MPH
winds in the summer, then your threshold should be reduced to about
16-17 MPH when it is below freezing!
2. The best tip for gloves! 2 pairs
of gloves! The first pair should be a medium weight Thinsulate
cloth, or woven, gloves with rubber "grippy dots" or "grippy
stripes" to grip the transmitter, with holes or slits cut in the
thumbs, which allow you to feel the transmitter sticks
directly, and still allow you to feel the rest of your fingers.
The kind with the fold back finger tip covers tend to get caught in
propellers. A second pair of warmer "standing around" mittens are
nice to have with you as well.
3. While necessary to wear,
REMEMBER THIS! Bulky jackets, and gloves, both like to catch in
spinning propellers. Be careful and aware. The engine starts
drawing air through the propeller, and it will try and suck your jacket in
with it. We didn't call old fashioned external carburetors on
vintage snowmobiles, "Scarf Suckers" for no reason! Same goes here,
but propellers are far more dangerous!
4. Boots and snow pants, or bibs,
may not look as casual, but standing in prop-wash, and
standing, and kneeling down, on frozen water, is COLD. Wear them
both, even if it seems toasty outside while loading your plane up.
That will soon change when you get out on the snow and in the open
wind! Landing a plane while shivering and doing a
snowman dance is LESS than optimum.
5. Glasses, vision and fogging!
The Sun is low in the sky, and the sky is grey,
and contrast is very low. Consider applying a temporary
yellow, or orange stripe at locations of needed visibility such
as the leading edge of the wing. Wearing quality UV
rated-Polarized sunglasses is a must. However, fogged
glasses are NO GOOD! If the wind is blowing in your face, when
looking up as your airplane leaves the surly bonds of earth, the
steam from your breath will
produce instant fogging of your glasses! As an avid
snowmobiler, I can say that aside from triple pane prescription
goggles, nothing is a cure-all for fog. However, a
coating of good quality car wax on both sides of your
eye-glasses is the best resistance I have found to fogging lenses.
They will still fog a bit, but they will clear quickly when they are
waxed, if you turn your head slightly to the wind. If you forget to
polish your eye glasses with wax BEFORE you go flying, the
ensuing fog will remind you! Then you will hand your transmitter to
your buddy who does not have fogged glasses, and when he looks up,
his will fog too! (Are you with me here!?)
6. Rubber-neckers! A few small,
orange, "Sports Cones" from Toys R' Us, or Target, or
wherever, placed to mark off a landing zone on a
frozen lake is a VERY WISE idea. Every single rubber-necking
snowmobiler, X-country skier, dogsledder, ice fisher, 4-wheeler, and
hiker WILL come to watch. They will ALWAYS stop in the
middle of your landing zone to watch. They simply don't
get it. Trust me on this one! (Snowmobilers like to race planes for
some reason, they always lose to a YS 1.40, but they never stop
trying, and without cones they will not stop going back and forth,
and will be right where you want to land when you run low on fuel.)
Give ignorant people some form of a clue where to stay away from! I
have seen it all on the frozen lakes.
DO NOT!!!!
Repeat
DO NOT!!!!
- DO NOT ...Pour fuel
on your engine and light it on fire to warm the engine!
(Don't laugh, this really
happens!!!)(OK laugh, but DON'T do it!) Unless you want to
roast marshmallows over your burning airplane!
- DO NOT ...Stand on the
bare Ice! Any "Body English" You use during flying
can translate quickly into the dreaded "Penguin Flop".
Instead, seek a spot with some
form of traction to stand on, AND STAY THERE until the plane
lands!
Don't forget to have a blast!
Creativity Counts!
Yes, we know, ...burning donuts on the
bare ice is fun!
Sincerely, MAIDEN Model Products.
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