DG Differences...

On Apr 16, 8:50*pm, "noel.wade" wrote:
Thanks All,

On the flaps vs. no-flaps argument, I guess it would be best to use a
hypothetical situation:

Imagine you have cloudbases that are 3000' to 4000' AGL.
Terrain is somewhat mountainous, but the cloudbases rise with the
terrain (20 miles east of the airport you might have 7000' - 8000' MSL
bases over a 5000' MSL mountain).
The lift is maxing out between 4 knots and 6 knots, with a lot of 2 to
3 knotters mixed in.
The Cu are 4 - 6 miles apart.
Winds are 5 - 10 knots, with the best soaring areas downwind from your
home field (so you face a mild upwind glide home).
Your total "window" for soaring is a 5 hour period during the day when
conditions are going to be generating lift.
The lift is workable from 1000' AGL to cloudbase, but staying within
1500' of cloubase seems much more comfortable.

This is a pretty typical "decent" soaring day in Western Washington.

So the question for you flapped pilots is: *Would you be pushing your
speed up enough in this situation to actually be using your flaps?

...Assume you're trying to do good cross-country flying - not super-
agressive contest-like flying, but also not just puttering around
within 15 miles of the airport either.

Thanks!

--Noel

Hi Noel,

As others are pointing out, forget about the "glide performance" or
speed issues between two similar vintage glass ships with and without
flaps. I fly in similar conditions at a club where we have probably
30 glass birds of mixed vintages and performance. There is a very
direct correlation between the impressive flights and impressive
pilots; there is almost no correlation between impressive flights
and flaps.

Since you've already absorbed the importance of trailers and automatic
hookups etc, the one thing I would consider in the flaps/no-flaps
debate is the off-field landing capabilities. So, the better question
to be asking yourself is whether you are going to be "pushing" a bit
such that you are making a few more off-field landings each year. In
other words, are you going to become a more aggressive XC pilot. As
Eric Greenwell mentions, there's probably nothing out there that beats
an early model 20 with landing flaps for shoe-horning into tight
fields. By comparison, my old LS-4, though very forgiving, couldn't
quite get into as small of a field as a 20, plus it suffered from the
achiles heel of LS gliders - a puny undercarriage.

One other huge factor is instruments. If ship "a" has a modern
panel (say a Cambridge 302 plus PDA, good pneumatics, a Becker or
Filser radio) while ship "b" has older stuff (say an M-Nav,
questionable TE compensation, and an old Terra radio), the better
panel will almost certainly add more to your XC performance, not to
mention the resale value of the glider.

Finally, if you really want to "do the numbers", a 5% increase in
performance for a flight that would have taken 4 hours means you save
maybe 12 minutes.... Is that really going to mean a significant
difference in the ability to achieve long distance XC flights? I
doubt it.

My 0.02.

Erik Mann
LS8-18 (P3)

Nobody mentioned the obvious yet: If you're not after pure performance,
the "feel" of a glider will be far more important than 5% performance.
Some pilots just like flaps, others just hate them. You may prefer "the
feel" of one glider, an other pilot may prefer "the feel" of a different
glider. Go fly both and decide which one you prefer.