Lynn Matteson
Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan
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 Posted: Sun Feb 01, 2009 3:13 pm Post subject: Ski report/snow conditions |
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Last week I had a "ski tuck" due to the bungees not being set to a
high enough initial tension. This week I cut 2" from them and
reinstalled and test flew them yesterday and today, and could not
get it to happen again. Admittedly, I wasn't really giving it what
could be considered an acrobatic test, but I made some (weak) dives
and pull-ups, and couldn't get the ski, or skis, to drop or tuck. I
even flew in bumpy-bangy air. I had made a tension check before and
after the shortening, and I picked up about 8 pounds of tension per
cord, or 16 pounds per ski.
I flew today to test the condition of the snow. Last week when I
tried to leave here to go to Oshkosh, the snow was so wet and heavy
that I could not get over 20 mph on the takeoff roll. This was after
2 days of above freezing temps...34-36 degrees F. Today, the
conditions were the same...overnight of over freezing, and 34 F when
I took off. It took a bit of coaxing, but I got up alright, and
landed at 4 different snow-covered grass strips. It was the same at
all strips...a bit longer than normal (most ski takeoffs take more
runway, I've read), but doable. When I stopped for lunch, I parked in
my own tracks, then 30 minutes later just rocked the plane a bit
before fire-up, firewalled it, and away I went, taxiing to the
runway...slowly. I used up about 1100 feet of a crosswind, no-tracks
runway before giving up and trying it on a snowmobile-trodden runway
into the wind. It still took about 300 feet before it got off the
ground due to the sticky snow conditions.
An article I had read (National Research Council of Canada) talked
about "snow friction" in this way:
"Early in the tests, it was found that sliding resistance and
adhesion were far more dependent upon snow conditions than on the
design of the ski. Further, the skiing quality of the snow changed
continually and it was not unusual to observe marked changes taking
place in less than an hour. The publication notes that there are
times when the sliding resistance of aircraft skis is so great that
it is impossible to reach flying speed."
I'm having a blast test-flying my skis, and seeing first-hand how
some of the writings that I studied while building them have merit.
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062, 605 hrs
Sensenich 62x46
Electroair direct-fire ignition system
New skis done and flying
do not archive
On Feb 1, 2009, at 5:17 PM, Lynn Matteson wrote:
| Quote: |
The "grass catcher" is the problem with either the "X" or the
"Z" (or "S") method of applying tape...whether you apply the tape
from "under the front to over the back" or vice versa, there will
always be a wedge of space that wants to collects debris. It's just
harder to get out of the "X" method. That's why I've contented
myself with the "over the front to over the back" method....yes
it's aerodynamically dirty, having a space underneath that can eddy
air, but have we a really "clean" plane otherwise?
Your diagrams are very understandable, Noel...good job. Lost
Saturday? : )
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062, 605 hrs
Sensenich 62x46
Electroair direct-fire ignition system
New skis done and flying
On Feb 1, 2009, at 1:57 PM, Noel Loveys wrote:
> Sunday afternoon and I can visualize the X system easy now...
> Friday nights
> not the best night of the week for me;-).
>
> I agree the X system allows for a light hinge on a model but a
> place for
> grass and leaves etc. To catch in the "Real thing".
>
> What I was thinking at first was a couple of pieces of say 2 1/2
> inch tape
> sewn right down the middle and then one half of each tape doped to
> the
> stabilizers with the other halves just finished to match the
> plane. They
> should be stiff enough to seal the gaps in flight. I'll attach a
> couple of
> rough diagrams... emphasis on the term rough!
>
> Noel
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_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM |
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