> What is your opinion on gap seals for a IV?

I really have no opinion on gap seals for a Lancair IV wing.
I can say that I prefer to hand fly most of the time, and don't
like the feel of aileron control drag caused by mylar gap seals.

> The ones used on gliders??

There area few different types of gap seals on gliders.
The most common, or at least the most visible are pre-curved
mylar strips adhered to the wing and sliding on the control surface.
Sometimes the strip and its adhesive is recessed into the wing surface.
The one on the bottom probably does more to reduce leakage as it is
held tight by the pressure difference.

BTW, that's the pressure difference between the top and bottom of the
wing - the difference which creates lift. The gap seals may also
have to deal with leakage from inside the wing if there are holes
in the drag spar or where the pushrod passes through.

Another type of gap seal uses a fabric seal hidden between the
fixed and moving surface. The prevents flow from the high pressure
side to the low pressure side.

Which type of gap seal is appropriate depends on many things,
including....
- the airfoil
- wing construction
- location relative to turbulent transition
- the mission
- risks of control interference
- cosmetics
- how much you feel like doing the considerable work to get a good seal