I purchased a PIK 20D which had top mylars. They were in good shape so
we just put some safety tape on them. The ship did not circle very well
because you couldn't slow up without hearing the separation on the
airfoil and feel the stall mush. I decided to put mylars on the lower
surface. Internal seals seemed impossible because the ailerons and flaps
have to move side ways to assemble. After Eastern Sailplane installed
the lower seals the ship performed much better. I had also installed new
push rod seals for the flaps and ailerons both at the root and the
outboard exit.. With its new configuration I could circle much slower,
about 43-45 kts with 8 degrees of flaps. Previously the ship needed to
fly at 47-50 kts. I finally settled with 6 degrees as the best setting
for average thermals here in Ohio. My theory was that the lack of lower
seals was allowing higher pressure air to go right up through the wing
escape through by pushing up the top seals and spoil the laminar flow
aft of the flaps & airelons. With the lower seals being pressurized an
pushed into the gap they created a much better natural seal. My
thermalling was much improved and I was able to stay in a gaggle with
much later glass without having to fly faster and have a larger diameter
circle. Weaker thermals were usable. I finally got the performance
expected. I can't remember if we used the 25 mm or the 30 mm mylar but
we chose the smallest tape possible. There is considerable stress on the
tape when the flaps are lowered for landing but good preparation and
safety tape will do the job. I recommend you have a professional install
them. We used a "Monocote" heat shrink model aircraft application iron
to improve the adhesive seal where delamination was taking place in a
few stops. It is a small iron with a Teflon coating. I glad you asked a
question I could help with. Please e-mail me directly or call if you
want to chat. REMOVE "NOSPAM" from my address to respond.
culverflyer wrote:
any first hand experiences? i am considering some for my 20
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