On 23 Oct 2003 11:48:25 GMT, Kevin Neave
wrote:

Hi folks,

In order to get the best performance from the gliders
we fly we need the C of G near the aft limit.


Well. maybe.

How much difference does this actually make?

As Robert Ehrlich pointed out in a earlier post at some point in the
normal operating range of speeds you probably want to organise zero
lift on the tail. Moving the C of G will move this point.

Or is it just perception ?

For example, If I add 60kgs of ballast to my Discus,
I should put 2kgs in the fin tank. How much drag penalty
will I incur by not doing so? Do I lose more by adding
tailballast & sacrificing stability than I actually
gain in reduced drag?

It is possible to calculate the induced drag produced by the tail
giving you 2 Kg of lift in either direction.
I'll let someone else do that this time.

You don't want to sacrifice so much stability that maintaining accrate
attitude becomes difficult or takes too much concentration.

I wasn't a believer in tail tanks until I flew an ASW20B with one.

Our BD4 goes noticeably faster with someone in the backseat or heaps
of baggage there and doesn't become unstable.

Mike Borgelt