Posted for Robert R Pastusek <rpastusek@htii.com>:

Hans wrote:

Hi all ,
I am thinking of adding winglets on Lancair 4 , I will not be going above 12k
feet due to oxygen , will I gain any cruising speed at 12000ft or bellow ?
Looking forward to your suggestions,

Hans,
The IV/IV-P will definitely slow down with the addition of winglets. I have
them on my IV-P (N437RP) and I believe they improve the landing
characteristics-specifically stability-a bit; and the Australians required
them for high altitude (FL 200 and above?) cruise stability. The down-side is
that they add drag to a very efficient, low-drag wing while in cruise mode,
slowing the airplane down. At least one of our Lancair builders has done some
"side by side" flight testing with/without winglets and posted this
information to the LML in past years, My own experience with was from some
side-by-side flying with Bob Wolstenholme early in my flight test period.
...not scientific at all, but his airplane, without winglets and a 3-blade
prop (I have and MT 4-blade) was definitely faster (5-10 KIAS) in cruise with
similar engine power settings... K
I asked my wife about deleting them and building some regular tips...she says
NO...they are sexy!  So they will stay, and I will follow the faster airplanes
a bit in trail...  J
My two cents...
Bob