Decolage (sp?) refers to the angle of the stab relative to the wing. since
almost all glass sailplane kits(what I fly mostly) have the wing root molded
into the fuselage ,I don't concern myself with the Datum or such. All that
does is determines how the fuse is carried relative to the wing, remember
the hobie Hawk, with its seemingly nose down attitude. This is of more
importance in power planes when you have a thrust line to deal with.
Remember, every airfoil has the speed that it "likes" or performs best at,
Trimming tail plane incidence to suit this cruise is something I find a lot
of pilots don't do. To a degree this can be a preference as well. CG
adjustment is another way, but as you observed can lead to other problems if
moved to far or worse behind the aerodynamic center of the plane.
I am sure there are others who could explain it more completely.
john
John Derstine
E-mail; [EMAIL PROTECTED]
Scale Soaring: http://www.Geocities.com/~scalesoar
-----Original Message-----
From: Michael Imsic [mailto:[EMAIL PROTECTED]]
Sent: Sunday, November 14, 1999 6:38 PM
To: John Derstine
Subject: RE: [RCSE] DG-600. CG
Hi John. You state that thermal planes generally have a negative 1.5 to 2.5
deg. incidence. What bout the wing, is that then set to zero relative to
the datum line or positive something?
Kindest regards
Michael
Michael Imsic
Melbourne, Australia
ICQ 3481522
> -----Original Message-----
> From: John Derstine [mailto:[EMAIL PROTECTED]]
> Sent: Monday, 15 November 1999 6:31
> To: [EMAIL PROTECTED]
> Cc: RCSE
> Subject: RE: [RCSE] DG-600. CG
>
>
> Gary:
> If you like the way it flies, why are you doing a dive test/ It is an over
> rated test(in my opinion) that is dependent on the tail plane
> incidence AND
> CG. In other words only useful if you understand the relationship between
> Decolage and C.G.and usefull if you pre determine your prefered
> cruise speed
> at a chosen angle of tailplane incidence. It gets somewhat muddy
> after that,
> and I don't pretend to understand all the math. Often quoted and generally
> misunderstood in my book.
> So if you like it, fly it, and don't worry about the dive test.
> In case you want to play with this some more. a thermal scale
> ship generally
> has a tailplane incidence of between 1.5 & 2.5 degrees negative(trailing
> edge up/leading edge down).Fly the plane until you are
> comfortable with the
> speed at which it flys in neutral trim and adjust the incidence so the
> elevator is at neutral when it is flying at that speed. All this is given
> that the C.G. is somewhere close to correct. I would guess around 30% for
> the 600, but there are of course many factors which can affect
> this. then do
> the dive test to fine tune the C.G.
> Remember one affects the other and unless you are having a
> problem with the
> glider, I would't bother.
>
> -----Original Message-----
> From: Gary and Tracy Humphrey [mailto:[EMAIL PROTECTED]]
> Sent: Sunday, November 14, 1999 12:16 PM
> To: [EMAIL PROTECTED]
> Subject: [RCSE] DG-600. CG
>
>
> I have been flying my new DG-600 trying to figure out the CG. The plane
> flies totally mushy with the CG at about 35% back, but when I add weight
> the plane comes alive, penetrates better and doesn't want to tip stall.
> Now heres the catch when I do a dive test the plane wants to pull out
> quickly indicating that there is to much nose weight. If I keep adding
> weight I am afraid that the elevator will die. Thanks Gary
>
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