(G.A. Seguin) wrote in message om...
(Diederik) wrote in message . com...
At our gliding club we have a ls-4 which has exactly the same problem,
although it only manifests itself at high speed. I think it is
resonance of the air inside the fuselage (almost the same as blowing
on a bottle or a organ pipe). We haven't looked for a solution jet.
Would like to know if anyone has...

Hi,
My LS6b has the same problem if I do not tape the horizontal/vertical fin gap.
Or if I do not seal the square opening on top the elevator.
S6

Ditto on my old LS4 and my LS8. I now have a piece of .040 clear
plastic film permanantly taped (hinged) in front of the access opening
as a cover. After the stabilizer is completely threaded on, the cover
is taped on the remaining three sides. Makes a nice, smooth surface
and allows you to see that the stabilizer has been locked down during
the critical assembly check. Common blister-packs for food make a
good source of the clear material (I think mine came from a package of
Proscuitto).

Also, I had low density foam all around the top of the stabilizer to
prevent airflow up into the tail; IIRC, my LS4 was completely free of
any howling, even at high speeds.

Erik Mann
LS8-18 (P3)