Rag and tube construction and computer models?

Stealth Pilot wrote:


1300lb auw (well actually 590kg with an empty weight of 362kg.
empty cg moment arm is 214mm.

See, THAT's the problem with the metric system...

Is that supposed to be mm, or cm ???

millimeters.

Also, where is your datum for this measurement?


214mm is a tad over 8 3/8" back from the only datum used on the
tailwind :-)
recall that it will always have a pilot added to the empty weight and
you dont actually fly with empty fuel :-)


Actually, 1425 is the GROSS. If yours is that heavy without pilot
and fuel, then yes, maybe you'll have a 600 pound load on the tail.

Please recall that I was talking about straight and level flight.
Pull G's and the load goes up.

But 75 pounds S&L load still shouldn't make 650 pounds at 4 Gs.

Look. how about a reality check?

Have your bright boy check to see how much the stab spar will bend
at 650 pounds load.

crumber nunch away. I'll bet you get close to 65lbs as the maximum
download.

(just remembered where my number comes from. future son in law is
doing his commercial studies, worked the numbers with a few
guestimates where there are no aerofoil data. aerofoil data is what's
needed.)
Stealth Pilot

On Sun, 11 Apr 2004 14:16:32 GMT, Richard Lamb
wrote:

Stealth Pilot wrote:


1300lb auw (well actually 590kg with an empty weight of 362kg.
empty cg moment arm is 214mm.

snip

Actually, 1425 is the GROSS. If yours is that heavy without pilot
and fuel, then yes, maybe you'll have a 600 pound load on the tail.


you've lost me totally there.

590kg and 362kg are the measured weights of the aircraft, full to the
gunnls and empty. they are not the downloads.
65kg download was the worst case calc at cruise and max auw as I
recall.
at 4g we could say that it is the equivalent of 4 people, 2 a side,
standing on the elevator spar. it might deflect a little but I think
it is feasible.
the tube concerned is 1 1/8" dia by 65 thou wall thickness.

Stealth pilot