FES in Contests

I enjoyed reading the article by Francois Pin over on the Soaring Cafe about his experience racing the Alisport Silent 2 Electro at Moriarty last year..

I would think that having a "bullet proof" propulsion system would give a significant competitive advantage over a "pure glider" by allowing one to significantly stretch the "safety envelope". Think low saves, flying over unlandable terrain, crossing large blue holes, etc.

I doubt that this advantage is reflected in sailplane handicaps. (Note that Francois believes that the FES drag is near nil.)

I know this has been discussed in this forum OLC. However, sanctioned contests are another kettle of fish.

Comments?

Lou

On Thursday, February 13, 2014 12:34:33 PM UTC-5, MNLou wrote:
I enjoyed reading the article by Francois Pin over on the Soaring Cafe about his experience racing the Alisport Silent 2 Electro at Moriarty last year.



I would think that having a "bullet proof" propulsion system would give a significant competitive advantage over a "pure glider" by allowing one to significantly stretch the "safety envelope". Think low saves, flying over unlandable terrain, crossing large blue holes, etc.



I doubt that this advantage is reflected in sailplane handicaps. (Note that Francois believes that the FES drag is near nil.)



I know this has been discussed in this forum OLC. However, sanctioned contests are another kettle of fish.



Comments?



Lou

Nothing is "bullet proof". It is just an illusion.

Actually a recent study has found hat the FES propeller has a significant, measured impact on performance (2-4% depending on average flying speed). The FES should have a considerable handicap over pure in, for example, the Lak17a or b with FES vs non FES. The US handicap committee has done nothing to address this. Smells funny to me. Clearly a big propeller in the nose airflow is not equal to not having a massive propeller? Only thing for sure is THAT IT IS NOT THE SAME PERFORMANCE. Yet the handicaps are the same?

On Thursday, February 13, 2014 2:20:41 PM UTC-6, Sean F (F2) wrote:
Actually a recent study has found hat the FES propeller has a significant,
measured impact on performance...

Provide the data, Sean.

Not my job. Isn't that what the handicap committee does?

On Thursday, February 13, 2014 4:00:38 PM UTC-5, Sean F (F2) wrote:
Not my job. Isn't that what the handicap committee does?

Handicap committee evaluates data but does not generate it. As well designed as the propeller appears to be, I would think the 4% described is really high. Maybe Sean can provide a link to this data that he apparently has seen. I would agree that it certainly does not help performance.
It is also possible that the HC committee took no action for the simple reason that no one asked them to.
UH

On Thursday, February 13, 2014 3:00:38 PM UTC-6, Sean F (F2) wrote:
Not my job. Isn't that what the handicap committee does?

They evaluate. If you have a link to the actual data, it would be much appreciated. I have seen the video of a couple of the flights (one with and one without the prop installation), but have not been able to find the polars. The committee cannot work with a statement of "2 to 4%". They need hard data to review.

So, please forgive my first response. If you can provide data in the form of polars, sink rate tables, or some such, or even a link to actual data, it would be appreciated. You seem to have a better knowledge of where this can be found than I, as I have looked and could not find actual data. If I have actual data, I can help in getting it to the right people for review.

Help appreciated,
Steve

CHECK OUT THE VIDOES ON THIS THREAD: https://groups.google.com/forum/m/#!...ng/QIeXikPEkaY

I agree 4% is pretty high...but clearly it is not exactly equal performance from an aerodynamic perspective. Seems like an easy thing for the handicap committee to act on. The FES owners are trading some performance for convenience and safety (avoiding land outs, etc). Nobody likes to start with a significant disadvantage in any form of competition.

As a pseudo engineer, there is significant square edged frontal area exposed to the airflow right at the nose. In addition a gap between the spinner and the fuselage in a high pressure area of the nose. Then you have 2 complex curved 18 inch propellers laying against the nose aft. At 80-100mph+, that must be killing the gliders performance. At 70 it surely cannot be helping. It also probably damages the flow over the wing root area, especially at low speed and higher AoA.

I will start some research into getting the study results in detail. I have have already sent a few emails. In the meantime look at the videos I posted last summer in the link above.

I think at least a 1% handicap is warranted. Something! Not a huge amount of these gliders in the market, but there are 20 or so and several new Lak17b FES in the US and Canada. The handicap is affecting the decision to convert gliders in some cases. Not just Laks but the usual suspects.

That said, maybe the aero impact is balanced out by the 60-80 lbs of added weight in batteries, etc? Is that the case? I'm not really sure how handicaps are formulated in terms of modifications, wing loading, etc.

Yes, I am thinking about converting my Lak17a to FES someday....

Flying to Florida as I type.... :-)

Sean

I train a lot of engineers within our company. I find more important for them to know what they don't know rather than what they do know. This keeps us out of a lot of trouble. Although some can't wrap their mind around the simplicity of this lesson. Pseudo Engineer is a new one. Sounds like something needed in the Thailand tourist industry. I bet the curriculum was interesting.

Rather than checking out the videos (link didn't work for me, but I have seen the videos of the tests being conducted), you can check out the SSA Website. If you do, you will see the LAK-17B-18 FES does have its own handicap number, and it is different than the LAK-17B-18. The difference is in line, in both weight delta and handicap delta, to the LAK-17A-18 to the LAK-17AT-18. The delta for either is .01.

That said, you may want to look and see which way, and then look harder for that data from the Akaflieg.

Have fun at the GP this weekend, Sean. Wish I could be there to fly with you guys.

Steve