Energy management

The perennial contest finish argument is always entertaining.
May I, as an ignorant bystander, ask a related question
without being strafed too much ? If a finisher has
the energy for a fast low pass and then pullup to a
safe pattern, how much time along the course was spent
to acquire that energy to be dissipated after the task
is over ? Seems to me that there must be some points
loss involved, even if it's small. Except of course
for someone who is sure he has won by a large margin
and will get his 1000 - but even then, there is a points
gain for all the other competitors.

Ian

Ian,

That's the question I posed in an earlier thread, and the answer (from
Andy) is that pilots consider it safer to bank a little extra altitude
in that last thermal before starting final glide, rather than risk
starting a final glide that's marginal, and then hitting sink, and
then finding nothing (or something very weak). This makes more sense
if you consider that thermals tend to be both stronger and farther
apart late in the day. In short it's just a risk management exercise.

I've read about some top pilots who believe in starting final glide
early (i.e., before having it), and "bumping" home, but this tactic
doesn't seem to have much of a following among the pilots I fly with.

Unlike how to cross a finish line as part of a landing pattern, the
topic of final glides has quite a bit of coverage in racing reference
materials...

~ted/2NO

On Feb 13, 1:07 pm, "Tuno" wrote:
Ian,

That's the question I posed in an earlier thread, and the answer (from
Andy) is that pilots consider it safer to bank a little extra altitude
in that last thermal before starting final glide, rather than risk
starting a final glide that's marginal, and then hitting sink, and
then finding nothing (or something very weak). This makes more sense
if you consider that thermals tend to be both stronger and farther
apart late in the day. In short it's just a risk management exercise.

I've read about some top pilots who believe in starting final glide
early (i.e., before having it), and "bumping" home, but this tactic
doesn't seem to have much of a following among the pilots I fly with.

Unlike how to cross a finish line as part of a landing pattern, the
topic of final glides has quite a bit of coverage in racing reference
materials...

~ted/2NO

To add a bit to Tuno's reply, it also depends a bit on the terrain
surrounding the finish. If there are miles of open fields surrounding
the finish, then one can (and really should) cut his final glide a bit
closer to the optimum. OTOH, at places like Turf, where the last 10
miles are totally unlandable tiger country, you better have enough
energy banked to make the finish no matter what!

Then, you need to get rid of that reserve of energy - speeding up gets
back a few of those seconds "wasted" climbing above the ideal final
glide height.

Which probably explains all those high speed finishes at Turf, eh,
Tuno? Works for me...

IMO, that's where one of the subtle traps of the "500ft at 1 mile"
finish creeps in. With all that pad, one is really tempted (and for
good racing reasons) to cut his glide real close. Then, when you get
to the line a bit too low to make it, you now have to decide if you
are going to try to pull up over it or take the penalty of a rolling
finish. Not an insurmountable decision, but it comes at the end of a
long day, you are tired, dehydrated, etc (does that sound familiar).

Bottom line - pilot in command is responsible for the safe conclusion
of the flight. Period. No excuses.

Kirk
66

All excessive speed that's left means spilled time... When you plan to
finish at 500' it's faster to leave early and make a (McReady) slow
glide to the finish line than to make a fast and low dash, which only
causes excessive drag. Of course it's very boring to ease back at 500'
instead of screaming alone with the crops hitting you're fuselage..

On Feb 13, 5:54 pm, "J. Nieuwenhuize"
wrote:
All excessive speed that's left means spilled time... When you plan to
finish at 500' it's faster to leave early and make a (McReady) slow
glide to the finish line than to make a fast and low dash, which only
causes excessive drag. Of course it's very boring to ease back at 500'
instead of screaming alone with the crops hitting you're fuselage..

No disagreement, but if you need to carry some extra altitude for
safety (typically 500 to 1000 extra feet out here in the US SW), it is
faster to convert that altitude to speed when you realize that you
have the finish made safely. With a 500' at one mile finish, you want
to finish at 501 ft, and whatever speed that gives you. With a 50'
finish line, you would want to descend gradually and just hit 51 ft at
the line. While it sure is fun running in in ground effect (just
don't do it over people or things!) it isn't faster, at least with US
50 ft finish rules, since you would have to pull up to get across the
finish.

But as you say, diving down into ground effect specifically to extend
a glide will not help - better to just glide at L/D max to ground
effect, then float as long as possible. This is due to the energy
loss in the dive due to the pushover, pullout, and higher parasitic
drag at higher speed. Difference is small, but measurable.

Kirk
66

"J. Nieuwenhuize" wrote in message
ups.com...
All excessive speed that's left means spilled time... When you plan to
finish at 500' it's faster to leave early and make a (McReady) slow
glide to the finish line than to make a fast and low dash, which only
causes excessive drag. Of course it's very boring to ease back at 500'
instead of screaming alone with the crops hitting you're fuselage..


Traveling the final mile by trailer is pretty slow too. If you have ever
come up a little short on final glide due to increased sink, you might
change your mind.

Hartley Falbaum
DG800B "KF" USA

"Ian Cant" wrote in message
...
The perennial contest finish argument is always entertaining.
May I, as an ignorant bystander, ask a related question
without being strafed too much ? If a finisher has
the energy for a fast low pass and then pullup to a
safe pattern, how much time along the course was spent
to acquire that energy to be dissipated after the task
is over ? Seems to me that there must be some points
loss involved, even if it's small. Except of course
for someone who is sure he has won by a large margin
and will get his 1000 - but even then, there is a points
gain for all the other competitors.

Ian

It appears that nobody has answered Ian's actual question (imagine that?)

The height gained in the pullup is equivalent to the total energy excess and
the "efficiency" of the glider in the conversion. Figure 90% for an open
classser, and about 85% for a current 15m ship (yeah, it's a W.A.G.) so if
the glider gets 600' on the pullup and has 85% efficiency, he had 705' of
total energy excess. If the last thermal was 4kt, then it took 1.76 min
extra to climb. If points are about 8/ min, then it cost about 14 points! If
running a street it gets a lot more complex as the streets are not uniform.

It is seldom so simple, as, unless the air is dying ahead, one must have the
power of prophecy to tell what is really going to happen.

Hartley Falbaum
DG800B "KF" USA

The most effecient way to do it and loose the least amount of points.
Fly your normal inter-thermal speed on your final glide, get rid of
the saftey margin, fly it right down to the deck, put the gear down
and land. Straight in finish, Nimbus 3 1 mile out at 75knts 150ft agl
(maybe less). That is by far the MOST effecient way to do it, dont
give up any points.

However if you break the glider because you hit a little sink..well
then you just give up the contest. Personally I can make mistakes
myself without hurting anyone. Went to the NHRA winter nationals last
weekend, Top Fuel guys blow up engines on each run, some get more than
3 seconds before fire starts comming out of places its not supposed
to. If we had pit crews like that, then I might do final glides like
stated above. Since we dont, i'll put in a saftey margin, put in a
faster final glide speed and "burn off the altitude" at the end when I
know I got it made.

On 16 feb, 23:40, "HL Falbaum" wrote:
"Ian Cant" wrote in message

... The perennial contest finish argument is always entertaining.
May I, as an ignorant bystander, ask a related question
without being strafed too much ? If a finisher has
the energy for a fast low pass and then pullup to a
safe pattern, how much time along the course was spent
to acquire that energy to be dissipated after the task
is over ? Seems to me that there must be some points
loss involved, even if it's small. Except of course
for someone who is sure he has won by a large margin
and will get his 1000 - but even then, there is a points
gain for all the other competitors.

Ian

It appears that nobody has answered Ian's actual question (imagine that?)

The height gained in the pullup is equivalent to the total energy excess and
the "efficiency" of the glider in the conversion. Figure 90% for an open
classser, and about 85% for a current 15m ship (yeah, it's a W.A.G.) so if
the glider gets 600' on the pullup and has 85% efficiency, he had 705' of
total energy excess. If the last thermal was 4kt, then it took 1.76 min
extra to climb. If points are about 8/ min, then it cost about 14 points! If
running a street it gets a lot more complex as the streets are not uniform.

It is seldom so simple, as, unless the air is dying ahead, one must have the
power of prophecy to tell what is really going to happen.

Hartley Falbaum
DG800B "KF" USA

I did. Fastest final glide is always glide at McReady, and pull out
all the speed, so stalling, while crossing the finish line. If you
assume a minimum finish height this is way more efficient then
screaming along and probably not thát much unsafer.

Thankyou, KF and all others. Am I correct to summarize
that there is a handful [or two, or maybe three handfuls]
of points to be lost by finishing low but with enough
surplus energy to pull up into a pattern rather than
finishing with minimum safe energy at any altitude;
that a safety margin should be carried right down to
the final few moments; that a straight-in and land
[either a rolling finish or after minimum-permitted
altitude finish] tactic on the remaining runway ahead
is the most 'efficient' provided it incurs no penalty;
and the balance between points grasped and safety and
showmanship is entirely at each pilot's discretion
?

Thanks again for the education,

Ian




At 22:42 16 February 2007, Hl Falbaum wrote:

'Ian Cant' wrote in message
...
The perennial contest finish argument is always entertaining.
May I, as an ignorant bystander, ask a related question
without being strafed too much ? If a finisher has
the energy for a fast low pass and then pullup to
a
safe pattern, how much time along the course was spent
to acquire that energy to be dissipated after the
task
is over ? Seems to me that there must be some points
loss involved, even if it's small. Except of course
for someone who is sure he has won by a large margin
and will get his 1000 - but even then, there is a
points
gain for all the other competitors.

Ian

It appears that nobody has answered Ian's actual question
(imagine that?)

The height gained in the pullup is equivalent to the
total energy excess and
the 'efficiency' of the glider in the conversion. Figure
90% for an open
classser, and about 85% for a current 15m ship (yeah,
it's a W.A.G.) so if
the glider gets 600' on the pullup and has 85% efficiency,
he had 705' of
total energy excess. If the last thermal was 4kt, then
it took 1.76 min
extra to climb. If points are about 8/ min, then it
cost about 14 points! If
running a street it gets a lot more complex as the
streets are not uniform.

It is seldom so simple, as, unless the air is dying
ahead, one must have the
power of prophecy to tell what is really going to happen.

Hartley Falbaum
DG800B 'KF' USA