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18m Nationals weight restriction at Seminole



 
 
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  #21  
Old March 10th 18, 12:31 AM posted to rec.aviation.soaring
[email protected]
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Default 18m Nationals weight restriction at Seminole

On Friday, March 9, 2018 at 5:47:44 PM UTC-5, Andrzej Kobus wrote:
On Friday, March 9, 2018 at 5:31:24 PM UTC-5, Andy Blackburn wrote:
On Friday, March 9, 2018 at 4:50:41 PM UTC-5, Andrzej Kobus wrote:
On Friday, March 9, 2018 at 3:27:50 PM UTC-5, Andy Blackburn wrote:
On Friday, March 9, 2018 at 11:35:06 AM UTC-5, Andrzej Kobus wrote:
On Friday, March 9, 2018 at 11:05:04 AM UTC-5, Andy Blackburn wrote:
"The approach you suggest would have conferred an advantage to the specific glider you are flying that is not part of the philosophy or rules of the FAI 18M class"

Andy, I can't believe what you wrote, did you read it before you sent it? Did you write it in the name of the Rules committee or is it your own opinion?

What advantage would I get, if I fly at the same wing loading as an ASG-29?
You must be kidding the 18M class weight restriction is 1320 lb. By limiting the weight you are handicapping me more than you are handicapping an ASG-29. On the east coast the optimum wing loading is around 10 lb/sq foot. You let the ASG-29 fly with that wing loading while handicapping me to 9 lb/sq foot. If not for the restriction I would be able to fly at the optimal wing loading. How is that fair? It seems to me the competition should never have been allowed to be held at an airport that can not handle the requirements of the 18 m class. Hopefully this is the last time Seminole is awarded a FAI class competition.

Hi Andrzej,

Thanks for your thoughts.

This was exhaustively analyzed and debated over a period of weeks, not a knee-jerk decision. I did supporting analysis, but the waiver request was from the contest organizers and approved by the SSA Board. Feel free to blame me as I support the approach taken and I meant exactly what I said above.

There were three approachers considered:

1) Fixed wing loading
2) Fixed MTOW
3) Fixed % reduction in MTOW from max certified

The criteria were basically twofold:
1) Address as directly as possible the concerns related to takeoff distance over an obstacle
2) Minimize any alteration to the existing relative performance differences across glider types - that is, minimize handicapping by glider type.

The maximum certified wing loading of gliders flying in 18M Class under the rules a

HpH 304S - 10.4 lbs/sf
ASH-31Mi - 10.8 lbs/sf
JS1C-18 - 11.0 lbs/sf
Ventus 3 - 11.3 lbs/sf
ASG-29 - 12.3 lbs/sf
JS3 - 12.4 lbs/sf (none signed up as of this writing)

Without any weight restrictions, the ASH-31 and JS1 would fly at close to 1.5 lbs lower maximum loading that the ASG-29 and JS3 and about half a pound lighter than the Ventus 3. A percent weight limit preserves the proportionate max wing loading differences but reduces the absolute differences by the amount of the % reduction. Setting a weight limit closes that gap to closer to 1 lb/sf and a wing loading limit totally eliminates it - effectively handicapping the higher wing loading gliders. To answer your specific question, handicapping most of the gliders other than yours gives you a benefit that you wouldn't otherwise have. I can see why you would prefer this as it would help you compete under strong conditions in particular.

However, there is nothing in the letter or the spirit of the rules governing 18M class (unlike Sports Class or SGP racing) that says we should handicap the performance of gliders - quite the opposite. People in non-handicapped classes purchase gliders for the specific design and performance tradeoffs of that design and have a right to expect that those choices wouldn't be deliberately diluted through changes in the rules. Motor gliders present some unique challenges because the designs represent an inherent tradeoff in wing loading range to accommodate a motor. That's the choice you make when you buy a motorglider - there are some benefits and some tradeoffs.

The other point is a wing loading limit doesn't purely address the takeoff distance challenge. It allows gliders with more wing area to fly at a higher MTOW, making them less safe in terms of takeoff distance due to higher rolling friction on soft ground, slower acceleration under the same thrust, etc. I can take you through the calculations if you like. Restricting takeoff weight is the clearly preferred safety option - it most directly addresses the takeoff distance challenge and does a decent job not changing the competitive capability differences across gliders (actually a % MTOW reduction does slightly better, but does less well on simply addressing the takeoff distance requirement).

I can see why you would have preferred a wing loading limit as it would have benefitted you by reducing the wing loading gap you'd otherwise have faced versus other gliders, but it's not the job of the Rules Committee (or the organizers or the SSA Board) to change that differential for you - particularly if it does a less good job at addressing the primary safety objective.

These issues are not simple to address as there are many moving parts. We attempt to maintain a safe and fair competitive environment consistent with the letter and spirit of the rules, but clearly different alternatives to addressing specific challenges will affect different gliders and pilots differently. Our attempt here is to minimize the changes in the competitive differences between gliders. I'm very comfortable this does the best job of all the alternatives, none of which is 100% perfect. The perfect solution is a longer runway, but that wasn't a realistic alternative.

Andy

Andy, your reasoning is completely flawed because on the east coast no one flies with wing loading of 12. You so called solution allows some glider to fly at optimum wing loading for the east coast while handicapping higher wing area gliders. I hope you can understand that. If the contest was held in Uvalde your reasoning would have been justified but not at the location the contest is going to be held. I hope you can admit this.

The other point is a wing loading limit doesn't purely address the takeoff distance challenge. It allows gliders with more wing area to fly at a higher MTOW, making them less safe in terms of takeoff distance due to higher rolling friction on soft ground, slower acceleration under the same thrust, etc. I can take you through the calculations if you like.

Again, you could take the weight 1150 divide by the highest wing area glider and establish weight for each of the 4 or 5 types that would never exceed 1150.

I can see why you would have preferred a wing loading limit as it would have benefitted you by reducing the wing loading gap you'd otherwise have faced versus other gliders

Wrong again! I was not disadvantaged on the east coast because I could not use a higher wing loading on the east coast anyway. Once again no one flies on the east coast with wing loading of 12. Your west coast 18,000 cloud bases experience with wide thermals does not translate well to making rules on the east coast.


Andrzej,

Your proposed solution is to set the takeoff weight for your glider suitable to meet the takeoff requirement and then put an additional (and unnecessary to the safety goal) weight reduction on other gliders with less wing area. It's not in the spirit or letter of the rules to force other gliders down to an artificially reduced wing loading. If they can take off at a higher wing loading and you can't because your glider is heavier, it's not up to the rules to equalize that any more than it is the job of the rules to equalize it in a situation without a runway limitation.

It did not escape anyone that on any given day the optimal wing loading may be anywhere across a range of possibilities depending on conditions - or that average thermal strength is generally lower in the east than the west. The issue is should we impose an additional wing loading reduction on other gliders with less wing area than the heaviest ones flying even though there is no reason to do it from a takeoff perspective?

I appreciate that you may have the view that the optimal wing loading in Florida is no more than 9 lbs/sf and that suits you and your glider, but there are many other gliders and many other pilots as well. For instance a JS3 would be forced to take off 200 pounds lighter than an ASH-31mi to meet 9 lbs/sf. When faced with the requirement of limiting weight for safety purposes, there's simply no rationale in the rules for imposing additional restrictions beyond what's required for safety.

If you'd like to introduce a proposal that we impose a maximum wing loading in 18M class as a general rule we could certainly survey the pilots and see if there is broad agreement, but it's not in the rules now. These decision need to be made based on a consistent set of principles, not what suits one person or another or one glider or another.

Andy Blackburn
9B


Andy, so far you failed to understand the other side of the argument. You are saying "It's not in the spirit or letter of the rules to force other gliders down to an artificially reduced wing loading." I am asking, is it in the spirit of the rules to force my glider to an artificially low wing loading? I hope not, but that is what you are doing. If you can force me to such unreasonably low wing loading why can't your force the other gliders.

You are trying to preserve the perceived advantage that ASG-29 would have due to its ability to load to around 12 lb/sq foot. The problem with that is that at the location of this contest this advantage does not exist, so you in fact legislated it.

I am very surprised that this decision was made without polling pilots or any discussion. The rules only talk about dry contest or FAI limit. I did not think this option even existed.

Andrzej
One less pilot flying contests


There was a strong suggestion to poll the pilots in order to see what their opinion was. I really wanted to know who would object to each of the options enough to not participate. This suggestion was not adopted.
I did not agree with what was adopted as I believed a wing loading limit would be most fair to all. In the end a consensus in the RC and strong position on the part of the organizers prevailed.
I really appreciate that SL was willing to host the event.
FWIW
UH
Ads
  #22  
Old March 10th 18, 01:33 AM posted to rec.aviation.soaring
Bob Kuykendall
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Posts: 1,225
Default 18m Nationals weight restriction at Seminole

Once again, an RAS thread for which the correct answer is "Sawzall."

And a necktie. Can't forget the necktie.
  #23  
Old March 10th 18, 05:15 PM posted to rec.aviation.soaring
Dan Marotta
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Posts: 3,335
Default 18m Nationals weight restriction at Seminole

The one thing about all of this that sticks in my mind is Andy's
original post where he listed as one of the determinants, "sandy grass
runway".* Did everyone forget that?* Higher weight with a fixed tire
footprint means sinking deeper into the ground resulting in higher
rolling friction (drag).* And don't fortet the limited field length,
fixed tug power...* It makes perfect sense to me.

On 3/9/2018 3:42 PM, Tango Eight wrote:
Andy: AK has a legitimate gripe. At Seminole, he had the expectation of flying at rough parity for reasons he's laid out and that any reasonable E. Coast pilot concurs with. An 1150 gross weight limit gives a significant advantage to the 29s and JS-3s **in this environment** that does not exist otherwise.

AK: I agree with Dave, you should go fly.

Rules Committee should reconsider this.

T8


--
Dan, 5J
  #24  
Old March 10th 18, 06:06 PM posted to rec.aviation.soaring
Andrzej Kobus
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Posts: 503
Default 18m Nationals weight restriction at Seminole

On Saturday, March 10, 2018 at 11:15:06 AM UTC-5, Dan Marotta wrote:
The one thing about all of this that sticks in my mind is Andy's
original post where he listed as one of the determinants, "sandy grass
runway".* Did everyone forget that?* Higher weight with a fixed tire
footprint means sinking deeper into the ground resulting in higher
rolling friction (drag).* And don't fortet the limited field length,
fixed tug power...* It makes perfect sense to me.

On 3/9/2018 3:42 PM, Tango Eight wrote:
Andy: AK has a legitimate gripe. At Seminole, he had the expectation of flying at rough parity for reasons he's laid out and that any reasonable E. Coast pilot concurs with. An 1150 gross weight limit gives a significant advantage to the 29s and JS-3s **in this environment** that does not exist otherwise.

AK: I agree with Dave, you should go fly.

Rules Committee should reconsider this.

T8


--
Dan, 5J


Dan, no one disputes that the take off weight needs to be limited for this location.
Establishing the maximum weight for a safe take off and then determining the weight for each type of a glider to establish a common wing loading for all participants would be the only fair way to resolve this problem. In such case no one would fly above the safe weight and everyone would be allowed to fly at the same maximum wing loading to ensure a fair contest.
In this case a small minority got screwed by the organizer and a few pilots who pushed for this arrangement. No wonder contest participation is dropping.
  #25  
Old March 10th 18, 11:22 PM posted to rec.aviation.soaring
Tom Kelley #711
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Default 18m Nationals weight restriction at Seminole

On Saturday, March 10, 2018 at 2:25:48 PM UTC-5, Ron Gleason wrote:
On Saturday, 10 March 2018 11:47:36 UTC-7, Andy Blackburn wrote:
On Saturday, March 10, 2018 at 12:06:08 PM UTC-5, Andrzej Kobus wrote:

Dan, no one disputes that the take off weight needs to be limited for this location.
Establishing the maximum weight for a safe take off and then determining the weight for each type of a glider to establish a common wing loading for all participants would be the only fair way to resolve this problem. In such case no one would fly above the safe weight and everyone would be allowed to fly at the same maximum wing loading to ensure a fair contest.
In this case a small minority got screwed by the organizer and a few pilots who pushed for this arrangement. No wonder contest participation is dropping.


Hi Andrzej,

I'm sorry you feel like this doesn't work for you. I assure you there is no conspiracy to screw the minority of pilots flying big-wing motorgliders. We did think about and analyze this issue with some care, including the issues you raised. Any approach we pick is going to have its own idiosyncrasies. You are quite correct that on a contest day where the thermals are never stronger than, say, 2.5 or 3 knots, the thermals are narrow and there is no streeting, it is unlikely that anyone will be likely to ballast up enough for the small-wing gliders to take advantage of their wing loading advantage and therefore a wing loading limit would do no harm to the competitiveness of these gliders.

The challenge is there is no guarantee that even an east coast contest in Florida in late spring will produce consistently sub-3-ish knot lift. The other issue is the effects of wing loading on achieved cross-country speed are asymmetric with lift conditions. On weaker days the difference of 1 lb/sf (9 vs 10) in terms of cross country speed is much smaller than on stronger days. Therefore a weight limit will create a small differential in speeds (0.25-0.5 mph) on weak days (2 knot climbs) and a wing loading limit will create a bigger speed differential (2-2.5 mph) stronger days (4 knot climbs). Basically, weaker conditions are closer to the ballast/no ballast crossover point so the overall performance effect of a pound in wing loading matters much less than on stronger days. In addition, if thermals are tight then the effect on stall speed and turning radius figure quite prominently when we are talking about a difference of 1 lb/sf. The charts on the attached link illustrate this graphically.

https://drive.google.com/open?id=1Gm...SaJjaLkgzmTqJz

If we were willing to get quite complex we could implement a wing loading limit on days when the lift is forecast to be 2.5 knots or less with no streeting and a weight limit on days when the lift is forecast to be stronger. That of course is hard to manage and it would be better to have a system that is consistent regardless of venue or weather. That, IMO, is a weight limit. IT's what was imposed at the Open Class Nationals at Nephi IIRC. It's also more robust in not upsetting the established design differences across varying conditions, though obviously nothing is perfect.

I'd encourage you to go and fly, the magnitude of any impact is likely to be far less than a couple of unneeded turns in a thermal - unless days turn out to be really strong, in which case you'd be spotting the small wing gliders a few miles an hour regardless.

I hope that helps.

Andy


Andy, there were no weight limits at Nephi for the Open Class in 2016. The only limitation(s) we had was which tow plane(s) could tow open class gliders due to their use of Schwitzer (sp?) tow hooks.

A question a bit off topic but relates to contests at Seminole. To start, I fully support any organizer placing site specific limitations for the sake of safety. For the 18M Nationals, have not reviewed the SGP, a 1150 pound limit will be used, OK, but in reviewing the current fleet of gliders flying this week at the Seniors there are 5 Arcus M's (empty weight 1212 pounds, 3 Duo's with an empty weight of 925 pounds and DG1000's at an empty weight of 915 pounds.

For consistency are the ARcus M's at the seniors self launching only, are the Duo's and DG 1000's only flying with a single person weighing less than 225 pounds? Just wondering why the weight issue for one contest but not for all contest at the same site.

Thanks, Ron Gleason


As in past Seniors, all the 20 Meter ships are gridded at the very rear(back of) of the grid.

With the 18 Meter Nationals, we will have much less runway length available..

No contest day today 3/10/2018. Boxed it tonight as next few days along with a formal announcement happening tonight at dinner.

Best. #711.


  #26  
Old March 11th 18, 01:47 AM posted to rec.aviation.soaring
Dan Marotta
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Posts: 3,335
Default 18m Nationals weight restriction at Seminole

Andrzej,

That sounds quite fair to me but this is the first time I recall hearing
that proposal.

Dan

On 3/10/2018 10:06 AM, Andrzej Kobus wrote:
On Saturday, March 10, 2018 at 11:15:06 AM UTC-5, Dan Marotta wrote:
The one thing about all of this that sticks in my mind is Andy's
original post where he listed as one of the determinants, "sandy grass
runway".* Did everyone forget that?* Higher weight with a fixed tire
footprint means sinking deeper into the ground resulting in higher
rolling friction (drag).* And don't fortet the limited field length,
fixed tug power...* It makes perfect sense to me.

On 3/9/2018 3:42 PM, Tango Eight wrote:
Andy: AK has a legitimate gripe. At Seminole, he had the expectation of flying at rough parity for reasons he's laid out and that any reasonable E. Coast pilot concurs with. An 1150 gross weight limit gives a significant advantage to the 29s and JS-3s **in this environment** that does not exist otherwise.

AK: I agree with Dave, you should go fly.

Rules Committee should reconsider this.

T8

--
Dan, 5J

Dan, no one disputes that the take off weight needs to be limited for this location.
Establishing the maximum weight for a safe take off and then determining the weight for each type of a glider to establish a common wing loading for all participants would be the only fair way to resolve this problem. In such case no one would fly above the safe weight and everyone would be allowed to fly at the same maximum wing loading to ensure a fair contest.
In this case a small minority got screwed by the organizer and a few pilots who pushed for this arrangement. No wonder contest participation is dropping.


--
Dan, 5J
  #27  
Old March 11th 18, 02:22 AM posted to rec.aviation.soaring
Andrzej Kobus
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Posts: 503
Default 18m Nationals weight restriction at Seminole

On Saturday, March 10, 2018 at 7:48:03 PM UTC-5, Dan Marotta wrote:
Andrzej,

That sounds quite fair to me but this is the first time I recall hearing
that proposal.

Dan

On 3/10/2018 10:06 AM, Andrzej Kobus wrote:
On Saturday, March 10, 2018 at 11:15:06 AM UTC-5, Dan Marotta wrote:
The one thing about all of this that sticks in my mind is Andy's
original post where he listed as one of the determinants, "sandy grass
runway".* Did everyone forget that?* Higher weight with a fixed tire
footprint means sinking deeper into the ground resulting in higher
rolling friction (drag).* And don't fortet the limited field length,
fixed tug power...* It makes perfect sense to me.

On 3/9/2018 3:42 PM, Tango Eight wrote:
Andy: AK has a legitimate gripe. At Seminole, he had the expectation of flying at rough parity for reasons he's laid out and that any reasonable E. Coast pilot concurs with. An 1150 gross weight limit gives a significant advantage to the 29s and JS-3s **in this environment** that does not exist otherwise.

AK: I agree with Dave, you should go fly.

Rules Committee should reconsider this.

T8
--
Dan, 5J

Dan, no one disputes that the take off weight needs to be limited for this location.
Establishing the maximum weight for a safe take off and then determining the weight for each type of a glider to establish a common wing loading for all participants would be the only fair way to resolve this problem. In such case no one would fly above the safe weight and everyone would be allowed to fly at the same maximum wing loading to ensure a fair contest.
In this case a small minority got screwed by the organizer and a few pilots who pushed for this arrangement. No wonder contest participation is dropping.


--
Dan, 5J


That was the original proposal before some folks decided to change it.
  #28  
Old March 11th 18, 03:52 PM posted to rec.aviation.soaring
Tango Eight
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Posts: 635
Default 18m Nationals weight restriction at Seminole

On Saturday, March 10, 2018 at 5:22:37 PM UTC-5, Tom Kelley #711 wrote:
along with a formal announcement happening tonight at dinner.


Help me Obi-wan Kenobi, you're my only hope. Do tell.

T8
  #29  
Old March 11th 18, 04:49 PM posted to rec.aviation.soaring
Tango Eight
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Posts: 635
Default 18m Nationals weight restriction at Seminole

Dan,

Here's the short summary from a tow pilot & dude with an old 15m ship and no skin in the game.

As tow pilots, we all get that gross weight on the back end of the rope is what matters, everything else is in the noise. No one suggests that the SLGP guys don't have a good handle on what they can tow, so we're good with an 1150 # max gross.

Let's consider two specific gliders only, the ASG-29 and ASH-31Mi.

Absent any restrictions, the numbers a
ASG-29, 1320 # gross, 11.7 psf.
ASH-31, 1389 # gross, 10.9 psf.

This wing loading difference will be important at Moriarity, but not at Seminole. Wing loading above 10# just won't get you any benefit at Seminole except on some crazy unicorn of a day.

Put in a flat restriction at 1150# gross. What happens is this:
ASG-29, 10.2 psf
ASH-31, 9.0 psf

At Seminole, the 29 pilot doesn't care. He wasn't going to fly heavier than 1150 *anyway*. The 31 pilot has a wing loading disadvantage on strong day.

That's what AK is ticked off about.

What's been suggested is to go with the 1150# max for the glider with the largest wing area (probably the ASH-31), then restrict all other types to the same (in this case 9 psf) maximum wing loading.

The other thing one could do is move anyone that wants to fly heavier than 1150 gross to the back of the grid. That's what I'd recommend.

Hey Andrzej... I think I'd like to go fly the 18s... since you won't be using your glider... :-).

best,
T8
  #30  
Old March 12th 18, 01:40 AM posted to rec.aviation.soaring
Tom Kelley #711
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Posts: 273
Default 18m Nationals weight restriction at Seminole

On Sunday, March 11, 2018 at 10:52:43 AM UTC-4, Tango Eight wrote:
On Saturday, March 10, 2018 at 5:22:37 PM UTC-5, Tom Kelley #711 wrote:
along with a formal announcement happening tonight at dinner.


Help me Obi-wan Kenobi, you're my only hope. Do tell.

T8


T8, the formal announcement was a rest day on Monday. We flew today, Sunday, score's are up on the SSA site along with daily reporting. Hearsay...one took off and chute opened in the cockpit, several relights along with landouts. Starting late (me) was a bad idea. Several flew most of the day below 3,000 msl. Some wishing they would of been able to do that.

Next fly day, Tuesday 3/13/2018.

Best. #711.
 




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