(JJ Sinclair) wrote in message ...
Al wrote..
The Ventus Strut is pushing up.
Part of the preflight on my Ventus B is to push down on the inboard flap
both sides to feel the gas strut pressure.

So, what is the purpose of the air strut?
JJ Sinclair


I believe the flap / spoiler-drive mechanism on the Ventus a/b is more
or less identical to the Mini Nimbus / Mosquito solution. Last winter,
I and my co-owner, replaced the gas struts on our Mini Nimbus C. After
spending a few hours studying the finer details of this clever
arrangement I dare say that the struts do indeed have a purpose.

There are two struts involved, one of them is (as far as I can figure
out) used to balance out the forces in the spoiler handle and ensure
locking of the spoilers in their in and locked position. This strut
will work against the movement of the spoiler-handle for the first
part of the spoiler deployment, and then change into working to
further open the spoiler. As Mini Nimbus drivers knows, the forces in
the spoiler handle will immediately after unlocking them be very low,
you may even have to hold them back for the first 1 / 4 of spoiler
travel. After this the force will increase as also the flaps will be
deployed. The gas strut will, to some extent, limit the force
variations during spoiler operation. I would assume that this is also
true for the early Ventus models. The spoiler-flap operation on our
Mini was improved after replacing the strut.

The second gas strut is there to push the flaps up against a stop. The
position of the stop is altered with the flap handle. If you push the
flaps downwards, the gas strut is compressed, and when you release it
will spring back against the stop, which is -7 to +8 degrees depending
on flap setting. This is clever! When the spoilers are deployed, they
will after initially opening some 30 degrees, catch on to the flaps
and rotate these to (I believe) 60 degrees. The flaps will during this
operation be pushed away from the stop and the gas strut will be
compressed.

The result, for those not yet acquainted with gliders equipped with
this very efficient and easy to use arrangement, is that for the first
part of the spoiler deployment, only the spoilers will open. After
approximately 1 / 3 of travel the flaps will also start to drop
increasing the effect of the spoiler. When fully deployed, the flaps
will be at 60 degrees, and you will be hanging in your straps viewing
the runway from the same perspective as the HP pilots describes.

Well, this was probably impossible to understand, at least for those
who haven't looked inside a Mini Nimbus, Mosquito or early Ventus.

After flying the Mini for a couple of seasons I really like this
system. The steep approach angles it enables means safer landings over
masks. The only downside is that the glider will float some in the
ground effect if you are carrying to much speed. Not a lot, but more
than say a LS-3 or some other glider with big conventional
Shemmp-Hirth brakes. I would assume that the float effect is still a
lot less than for gliders with only flaps.

We bought our struts directly from Schemmp Hirth, they were not at all
expensive and the delivery was swift. At least one of the struts have
some custom made fittings that will save you some work of you get them
from SH.

Happy soaring
Jan Larsson
Sweden

Ps. The website of my club
http://www.flygklubben.bojn.net/