SEN issue 1077 - 2 March 2007
- Category: Archive 2007
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SEN issue 1077 - 2 march 2007
Table of Contents
- F1Qs Performance - Schlosberg
- Lost F1J Correction - Halliday
- Re: F1Q performance - Gregorie
- 58th Annual Inter- Cities Meet - Shailor
- Address Updates
Yes, F1Qs have to spiral up - or climb with a wing's assistance!
In fact, the better F1Q models pitch angle does not exceed 70
It's difficult to draw conclusions from two flights, with an average
climb rate of 5.6 m/sec and a glide sink rate of 0.4 m/sec.
However, it's also clear that a 25-second motor run is excessive.
In the States, all the F1Q contests are run with a 20-second
motor run. At our next F1Q World Cup, which will be held at the
Nats on July 31st, the motor run will probably be reduced to 15
Dick Ivers has pointed out that reducing the battery weight will
not necessarily diminish performance. A lighter battery corresponds
to a smaller and lighter model. In Dick's words "I have a fairly
hot F1Q based on a Beschasny F1J wing. It's total weight is 368
grams. The battery is a Thunder Power Polite 910 mash 3S
weighing, 67 grams with connectors .... much less than the 90
Originally, when the FAI electric event were proposed, there was
also a mini event called F1R, with a lower battery weights. Some
of the F1Qs developed by the San Diego group, with fliers like
John Oldenkamp, might eventually become the nucleus of a
FAI mini event.
The robust performace of electric models is what attracts fliers
in the first place. The bottle neck at the moment is the lack of
off-the-shelf auxiliary components (front ends and pylon units).
Shorter motor runs are already here. But I'm absolutely against
changing the parameters of the event (maximum battery weights
for Nickel and Lithium based batteries) or solving future excess
performance before we have had enough time to understand the
Lost F1J Correction
Oops, sorry, I posted the wrong number for Kenny Oliver's lost F1J it should have been
916-3363-2017. If you could please correct it.
Beacuse of business travel etc it takes us a little longer to get address
chnages to the mailing list uno place.
Re: F1Q performance
I'd like to back up Tapio's F1Q performance figures with the following
An American friend, Bob Parks, has a WindDancer RC electric
, a Mark Drela design.
It is a 2m model, weighs 680 grams with a 146 gram LiPoly battery (which
gives about 240 watts output) and is powered by a 4:1 geared Hacker
brushless motor (I think its a B20L) fitted with a 10.5 x 8 folding
propeller. In 2005 he flew this with an altimeter installed and recorded
a 2700 fpm (13.76 m/s) climb rate.
At that climb rate an F1Q would reach 1125 feet (342 m) after a 25
second motor run and (at 0.35 m/s sink speed) would have a dead
air time of about 1025 secs (17 mins - 25 secs motor run plus 1000 secs
Bob's climb rate is a lot less than an F1C: in 1998 at Beja the good
F1Cs were getting to 160 m, measured with a laser range finder. Thats an
average climb rate of 32 m/sec over the 5 second run. A 90 gram battery
probably outputs less power than a 146 gram battery, but against that I
think an all-carbon F1J type model (1800 - 2000 mm span) could be built
to 400 grams, so these factors may cancel out. Adding 2% to an F1A's
weight raises its sinking speed by about 1% so I assumed that the
relationship would hold for a 33% weight increase and that an F1J's
sinking speed is the same as an F1A (0.3 m/s). Combining the two gives
the 0.35 m/s I used to calculate still air time.
If you split the difference between Tapio's and my examples (to average
the weak and gorilla batteries in the two models) you still get an
estimated 270 m climb height and a dead air time of around 13 minutes.
58th Annual Inter- Cities Meet
The Detroit Balsa Bugs will be hosting the 58th Annual Inter-Cities Meet on
May 25, 26 and 27, 2007 at the AMA field in Muncie, Indiana. This is both an
America's Cup and National Cup contest. On Friday, the 25th, there will also
be an FAI qualifier to accumulate points towards the program. Any persons
wanting a flyer, please contact me and I'll send one via email.
Thanks, and hope to see you there!