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.

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

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.

AK, just curious. How much does your 31MI weigh?
The handicap reference weight for a 31MI is 1189. Are you below that? Is the handicap table wrong?
If I read the safety notice correctly, the weight limit is not 1150lbs.
Gliders that weigh less than 1150 can only add water up to 1150lbs.
If a glider weighs more than 1150 dry, then it Is allowed to fly at the higher weight, but no additional ballast allowed.
Sounds like some heavy motorgliders might get an advantage.

While some heavy gliders are allowed to fly from the very back of the grid at the Seniors in March, there did not seem to be any discussion here about the density altitude difference between March and May when the 18m is scheduled.

Nice of SLGP to host the event. Would have been nice if it were earlier when the density altitude would be better or if another venue had stepped up.

On Sunday, March 11, 2018 at 10:16:04 PM UTC-4, wrote:
AK, just curious. How much does your 31MI weigh?
The handicap reference weight for a 31MI is 1189. Are you below that? Is the handicap table wrong?
If I read the safety notice correctly, the weight limit is not 1150lbs.
Gliders that weigh less than 1150 can only add water up to 1150lbs.
If a glider weighs more than 1150 dry, then it Is allowed to fly at the higher weight, but no additional ballast allowed.
Sounds like some heavy motorgliders might get an advantage.

While some heavy gliders are allowed to fly from the very back of the grid at the Seniors in March, there did not seem to be any discussion here about the density altitude difference between March and May when the 18m is scheduled.

Nice of SLGP to host the event. Would have been nice if it were earlier when the density altitude would be better or if another venue had stepped up.

I am very light, but I would be 10-15 lb over the 1150 lb limit, which brings a good point that it would not be safe for me to take a tow, according to the organizer. This means I would be forced by the organizer to self launch, nice! It seems the organizer is not able to fulfill his obligations to host an 18 m class, even with this restriction.

It would be interesting to hear more specifics on what is planned. The big issue seems to be launches on rwy18. Rwy36 has a nice runoff area and plenty of fields north of the airport. South is mostly trees. For the Seniors, they stage some of the heavy gliders off the end of runway 18 and push them one by one on to the grid after the others gliders have launched. Perhaps the plan is to accommodate a handful of heavy gliders that way. That plan would certainly not work for all of the 30+ gliders that have signed up..