WHY NOT A ROUND TAIL SKI?
We could call it a Bowlski!
2013/02/22
After our lake freezes, I
leave the wheels on as long as the depth of snow allows. Only when there is too
much drag on the wheels do I get the skiis out. I only have straight skiis,
unfortunately, or I could put them on sooner. Without a tail ski, the Rans
easily handles a foot of snow with the tail wheel but power to taxi is quite
high, sometimes over 4000 rpm.
A few years ago, I
experimented with some different shapes for a tail ski. Some people modify a
shovel and I tried that. Then I realized that for maximum maneuverability the
tail needs to swing either side and occasionally be pulled backwards so why not
a round ski? With that in mind I came up
with a stainless steel bowl that works very well. With it, turning was easy
because the bowl allowed the rudder to move the tail to one side or the other
with minimal resistance.
A problem did arise on glare
ice with little snow when the bowl just slid far too easily and directional
control was inadequate. To fix this I added a very small dual blade “skate” on
a shaft which was connected to the rudder. With this enhancement, steering was
as good as on pavement with a tail wheel.
Here are all the parts:
The bowl is about 18” in
diametre and about 6” deep. To support the flat centre section I cut a disk
from 3/8 ply and a length of 2x6 to sit on top. The 2x6 was drilled to take the
˝” steel shaft with the “skate” welded to the bottom and a bolt on steering arm
up top. A 3/8” threaded rod and U bolt
bracket bolted to the tail spring enabled the top of the bowl to be set
parallel to the aircraft centre line..
All assembled, it looks like
this with a lexan cover to keep the snow out:
And here it is installed:
Now, in the same conditions,
taxi power is 1000 rpm less and with much more maneuverability.
Weight is high at 9.8 lbs but
most of the metal fittings could be made out of aluminum instead of steel to
save a few lbs. And the 2x6 could have some lightening holes. On the S-7S it is
on, the additional tail weight is actually a plus for the CG position. Of course one of its nicest features is the
price: $20 should get you a pretty good bowl.