FES in Contests

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

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

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

On Thursday, February 13, 2014 6:42:22 PM UTC-5, Steve Leonard wrote:
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

I saw a German test somewhere a few months ago which showed handicap in the range of 2% if I could only remember where the document was located. It was a good technical paper. Maybe someone has a link.

On Thu, 13 Feb 2014 13:30:23 -0800 (PST), "Sean F (F2)"
wrote:

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

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

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

Sean

The referenced video indicates that Idaflieg has the data you need to
resolve this issue.

Suggest an interested party contact Luka Znidarsic at LZ Design
(www.front-electric-sustainer.com)

The video seems to indicate the manufacturer participated in these
tests, he would be a likely first contact for release of the Idaflieg
data.

Bob

In article "Sean F (F2)" writes:

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 Lak=
17b FES in the US and Canada. The handicap is affecting the decision to co=
nvert gliders in some cases. Not just Laks but the usual suspects.

Perhaps it shold be a inverse handicap, as the motorglider pilots are often
more willing to head off in directions where a landout would be a problem.

Since they have less risk involved in their choices, they should receive less
benefit. Sure, they don't win the day if they start the engine, but they don't
landout in the rocks, either.

( For the common argument that one should not depend on the engine - if folks
never depended on a sustainer, then they would not be buying them. )

Alan

On Friday, February 14, 2014 4:06:02 AM UTC-5, Alan wrote:
In article "Sean F (F2)" writes:



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 Lak=

17b FES in the US and Canada. The handicap is affecting the decision to co=

nvert gliders in some cases. Not just Laks but the usual suspects.



Perhaps it shold be a inverse handicap, as the motorglider pilots are often

more willing to head off in directions where a landout would be a problem.



Since they have less risk involved in their choices, they should receive less

benefit. Sure, they don't win the day if they start the engine, but they don't

landout in the rocks, either.



( For the common argument that one should not depend on the engine - if folks

never depended on a sustainer, then they would not be buying them. )



Alan

Would you really put your life at risk going into unlandable terrain hoping your engine is going to work (regardless if it electric or internal combustion)? If you think this way I suggest you stay away from engines or your life might be cut short.