1-34 Rudder

Roy Bourgeois wrote:
Eric:

I think we are really saying the same thing - just focusing on different
effects.

I'm pretty sure you are saying shorter arm, smaller rudder, and I'm
saying shorter arm, bigger rudder!

If you pick up the tail of a long fuselage glider and rotate it
around it's wheel 360 degrees on the ground, it will take you longer than
when you do the same with a short fuselage glider - because the radius of
the circle you must walk is different (and you need more steps with the
long fuselage glider). Or, you could change the speed of your walk (which
is what changing the rudder size does).

This is not a good analogy: in a steady turn, all the pieces of the
glider rotate at the same rate (revolutions per minute). Some of the
pieces are moving _faster_ (knots) than other pieces, especially the
inner and outer wing tips. That's why it doesn't take longer to "walk
the tail of the glider around" - you walk faster if you are farther from
the center of the circle. On a percentage basis, you aren't much
farther: perhaps a foot or two out of 150 feet or so.

But it isn't in the steady turn that the 1-34 has a problem, it's during
the entry to the turn.

This is why the 1-34 seems slow in
rudder response.

I've never flown one, but I'm pretty sure it isn't _slow_ in rudder
response, it just doesn't have enough rudder force to counteract the
adverse yaw from the ailerons when they are applied to turn.

Unless I've really missed something (it happens!), the "under ruddered"
comment only applies to the transient turn entry phase. In other words:
full aileron, full rudder, but the nose moves opposite the turn. This
isn't related to the speed at which the tail moves around, because
initially, the tail movement is in the wrong direction. As it settles
into the turn, the ailerons are moved opposite the turn until you have
some "top aileron", the amount of rudder is reduced, and everything is OK.

It is about the longest fuselage ever put on a 15m ship.
Now, there are many other reasons why a designer may want a long fuselage
(particularly stability) - but the reasons selected by the 1-34's designers
(I pass on whether they were the "best in the world") were not particularly
good ones, and once they abandoned the idea of the 17m wing they should
have shortened the fuselage (as they did with the later 1-35 and 1-36).

I still don't understand how rudder power is improved by shortening the
tail boom, andI still don't understand why the best sailplane designers
in the world haven't seized on the idea of making the tail surfaces
smaller AND making the boom shorter.

This comment addresses the orginal poster's question about "improving"
the rudder: Wil Schuemann told me the way to avoid this problem is by
using less aileron, not by making a bigger rudder. Less aileron, less
drag from the ailerons (drag is what the rudder is compensating for);
less drag = good. Not as pleasant to fly, but more efficient.
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Eric Greenwell
Washington State
USA