Oz Report
Volume 6, Number 2589 am, Friday, December 13 2002
https://OzReport.com
"Toto, I have a feeling we're not in Kansas anymore."
- In this issue:
Lanzarote Tove in Deniliquin The Top Twenty Aero’s down tube drag Birds in paradise Garmin 76 M2 Harness? Sydney Hang Gliding Club meeting
Lanzarote
Thu, Dec 12 2002, 5:00:00 pm GMTGordon Rigg writes that Bob Biaer won the meet.
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Tove in Deniliquin
Thu, Dec 12 2002, 5:00:01 pm GMTOliver "Olli" Barthelmes|Tove Heaney
Oliver Barthelmes «oliverbarthelmes» writes:
Here a shot of Tove’s efforts to prepare the Oz Open in Deniliquin:
2 topics in this article: Oliver "Olli" Barthelmes, Tove Heaney
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The Top Twenty
Thu, Dec 12 2002, 5:00:02 pm GMTGerolf Heinrichs|Oleg Bondarchuk|Paris Williams|safety
Oleg Bondarchuk «aerosint» writes:
The idea to have a race for the top twenty or whatever pilots from my point of view is not the best one. I'll try to explain why.
Hang gliding competitions still attract people to compete by giving them the possibility of making their own decisions and their own mistakes and still have a chance to win or enjoy the flight at least by flying on their own. It used to be a pilot's choice of taking a start time they wanted to take according to their own strategy or their readiness for flight.
If top twenty guys would start at a certain time there will be the rest of the field with them taking the same start time. I don't think many pilots would take a different start gate. Almost all if not all of them want to be with the lead gaggle to learn something new from the top pilots.
If top pilots are spread out from each other in time then all other less experienced pilots will have a possibility to start, let's say, with Manfred or with Gerolf if he would decide to start 15 min. later, or with Paris 30 min. later, or with someone else.
In our case there will be 100 or 150 gliders in one thermal above the start circle and some thermals after the start. There is no reason to invent such a complicated system, we can simply make a race with only one start time and there will be the same result - all pilots in one gaggle. It is possible to give up safety, making it a sacrifice to the nineteen top pilots and give them a chance not to loose Manfred as a lead for them, but I don't think many pilots would like this idea.
I hate gaggle flying, especially above the start gate and I know that many people do hate it as well. Yes, it would be great to watch it but I don't think it would be fun to be in that gaggle. I'm in doubt what type of skill it is necessary to have to be able to stay in such a gaggle and I don't know how many own decisions one of the nineteen pilots needs to take when having Manfred in the same gaggle from the start all the way to the goal line.
4 topics in this article: Gerolf Heinrichs, Oleg Bondarchuk, Paris Williams, safety
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Aero’s down tube drag
Thu, Dec 12 2002, 5:00:03 pm GMTRon Gleason «xcflying» writes:
Have you seen this? http://www.justfly.com/gliders/stalkeruprightcharts.htm
Sounds interesting and I would like to understand more. I wonder how the ATOS C compares?
I tried the URL, but while the page was there it didn’t really work that well. GW sent me the charts that were missing and the table of the data:
Source Data for Charts |
||||||||
Length |
Uprights chord, b, m |
S upright, m |
Cd |
Cd*S upright |
Speed, m/s |
Upright drag force, kg |
Delta, % |
|
AEROLA Carbon |
1.48 |
0.069 |
0.10212 |
0.03 |
20 |
|||
Wills Wing |
1.48 |
0.076 |
0.11248 |
0.035 |
0.0039 |
20 |
0.097 |
29 |
Bautek |
1.48 |
0.053 |
0.07844 |
0.08 |
0.0063 |
20 |
0.154 |
105 |
Finster Walder |
1.48 |
0.049 |
0.07252 |
0.357 |
0.0259 |
20 |
0.637 |
745 |
For 120 kg take off weight, 72km/h speed,15 glide ratio, glider drag force is |
kg |
|||||||
If glider with AEROLA carbon uprights at speed 72km/h has glide ratio |
15 |
|||||||
with WW uprights you will have glide ratio |
14.9 |
|||||||
with Bautek uprights you will have glide ratio |
14.7 |
|||||||
with FW uprights you will have glide ratio |
13.2 |
I am trying to get more information from G.W. I really question the nominal 15:1 glide at 45 mph.
In the mean time I asked Steve Pearson at Wills Wing about the claims made in the charts, especially as they are compared with the WW down tubes. He wrote:
It's impossible to make any kind of informed decision about the relative performance of the Stalker downtubes based on the published information. The link that you forwarded doesn't have any wind tunnel test data, and there's no indication that they even retested our section. Without a side by side comparison in the same tunnel, over a wide angle of attack and Reynolds number range, the information is completely speculative.
It's trivial to design a section that has better performance than the Slipstream at 20 m/s, at low angle of attack, without any other constraints. In fact, any number of NACA sections will do the job. Our wind tunnel tests show that the Slipstream performs 10% better and matches the Stalker's claimed Cd by simply sanding of the trip. The problem is that doubles the drag at lower speeds.
We're not always gliding at 45 mph and (unless you're flying a Swift) you're nowhere close to 15:1 at anything much beyond best glide speed. The advantage of the Slipstream profile is not the minimum drag coefficient at high speeds, but the extremely wide angle of attack range--especially at lower Reynolds numbers--with low drag coefficients. Would you trade.1 point better L/D at 45 mph for.5 point lower L/D at 30 mph?
Another important consideration is the structural performance (column strength) of the tube. Most of the drag advantage in the Stalker calculations is based on smaller size. Obviously, a smaller Slipstream tube would also have less drag. A lower strength tube is probably desirable for the smaller (non structural) rigid wing control frame. I'd be surprised if the new Atos composite downtubes don't have less total drag than a Slipstream also, but there's no chance that they could meet our structural standards.
As far as I know, our carbon bar is the only bar that has been certified on a flexwing. The Talon 150 was load tested to a 3 sec average load of 1700 lb and a peak load of over 2400 lb at 70mph with a Slipstream bar, without failure.
Finally, there's the issue of demonstrated performance. Manfred and many other top comp pilots from Icaro, Moyes, and even Aeros have flown with the Slipstream bars for years and (as you know) the 1st two 400 mile flights were Slipstream equipped.
I'm certainly not suggesting that it's not possible to design a better profile than the Slipstream--it's been out for 4 years and we even published the wind tunnel results http://www.willswing.com/articles/Article.asp?reqArticleName=MeasureDTs - -but there's more to it than making a couple of bar charts in Excel.
Find out more about this at OzReport.comOzv5n40.htm.
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Birds in paradise
Thu, Dec 12 2002, 5:00:04 pm GMTParis Williams
This Rosella is standing on one of the gliders on the porch of the house where Curt, Paris, and Bo are staying in Otford near Stanwell Park and eating very nicely out of my hand without pecking at all. It just picks up the sunflower seeds, cracks them open, eats the seed and goes on to the next one.
1 topic in this article: Paris Williams
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Garmin 76
Thu, Dec 12 2002, 5:00:05 pm GMTBetinho Schmitz|Curt Warren|Garmin 76
Curt Warren has reported that he has modified his Betinho instrument pod to handle the Garmin 76. Pictures soon.
3 topics in this article: Betinho Schmitz, Curt Warren, Garmin 76
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M2 Harness?
Bretton Woods|harness
Bretton Woods «brettonwoods» writes:
Do you know whether or not m2, maker of the Cigar harness, is still in business? Their web page is not functional.
2 topics in this article: Bretton Woods, harness
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Sydney Hang Gliding Club meeting
Thu, Dec 12 2002, 5:00:07 pm GMTStephen Hocking|TV|Sydney HG Club
Stephen Hocking «nswhga» writes:
Monday night, Dec.16, 7pm, Ned Kelly Room, Endeavour Hotel, Botany Rd (cnr Bay St), Botany. Last meeting of the year. Servery, bar, coffee, TV, the lot.
3 topics in this article: Stephen Hocking, TV, Sydney HG Club
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