Open- or FAI-Class? What class is faster?

[Fox9]

Since the attachment limitation is set to 512 kB (thanks to the responsible) flighttracks with little more than 2 hours flighttime can be published. Therefore you can find in the attachment a flight (which is surely improvable) with the ASW27 over a 250 km triangle. The question is, if an open class plane like Nimbus or ASW 22 is faster by same task and weather conditions like an ASW 27, LS 6 or Ventus. Let's make a practice test and publish your flighttracks.

Fox9

[triffid]

Since the attachment limitation is set to 512 kB (thanks to the responsible) flighttracks with little more than 2 hours flighttime can be published. Therefore you can find in the attachment a flight (which is surely improvable) with the ASW27 over a 250 km triangle. The question is, if an open class plane like Nimbus or ASW 22 is faster by same task and weather conditions like an ASW 27, LS 6 or Ventus. Let's make a practice test and publish your flighttracks.

Fox9

Depends if you get to fly at VNE full of water with no slow start and no slow finish, ie short flight peak of the day good modern 15mt should win, add in long stretches close to terrain and weak thermals Oen should win

Regards
MW

[Fox9]

Hello triffid,

It is a normal triangle of 250 km. You can find it in the default-tab of freeflight. The thermals are strong, the width ist narrow. It's not a good idea, to fly with vne (I suppose vmax). You can look in the trackfile for more information. In my flight I achieved a speed of 121 km/h.

Fox9

[Miguel BM]

The faster planes is 15m class. In Condor, you will adquire a maximun V med in thermal course, about 158 km/h with a MC +5.0 m/s (full ballast)
This speed only will reach over ideal coditions and with all thermals in your route and with a MC +5.0 m/s.
This speed will reach with very strong thermal (and no variation) and thermal helpers ON, to go for the next strong thermal without course desviation.

In fact, you will mantain about V med 130 - 140 km/h with a realistic MC +3.0 / +3.5 m/s and no thermal helpers.
With a Nimbus 4 (faster open class), you will mantain 125 - 130 km/h (full ballast and same conditions). (MC theory)

In real life, its very difficult to mantain more than 120 km/h in more than 500 km triangle, because the thermal conditions will change a lot over your route.
Also, in real flight, you will reach a line cloud over a convergence and make lots of km without circling thermal and make a faster medium speed, but Condor dont simulate convergence line of clouds.

Some FAI records examples:
FAI record on speed over a triangular course of 500 km is 158.43 km/h for 15m class (LS6-C) and 187.13 km/h
for OPEN Class (ASH-25), both in New Zealand.

Best regards

[Fox9]

Hello Miguel,

You are right. At high speed, the 15m-Class is better then the open class.
The open class has small advantagees in the climb rate. My question concerns
the 250 km triangle in the attachment. I have flown it with the ASW 27 and
ASW 22 (both with 50 % water ballast). In the attached picture you can see
the tracks and the barogram (Red=ASW22, Blue=ASW27). On the right the result
of both flights are summarized. The unit of the speed v ist km/h, the unit
of the average climbrate mCR is m/s. Therefore in this special case I think
that the answer is clear, although every flight is as random result within
a certain bandwith.

I was surprised by the superiority of the ASW 22 in the climbrate. I don't
know, if it is so in reality. In comparison with the ASW 27 circling with
the ASW 22 was more comfortable (in the Condor-Sim). That may be one reason
for the good climbrate.

Fox9

[TimKuijpers]

My analyse of this picture is that you were flying faster by the end of the race.
First leg is too slow for an ASW27 with good weather,
While the other legs the ASW27 had beatn the ASW22.
If you could send me the files, I will look at it with help of seeyou,
This will probably give me more details of both flights.

And about the nice thermalling with the ASW22,
in RL you can't easily roll into a thermal when you are in the lift,
you will have to begin the turn before you had hit the thermal...
If you set your ratio of Rudder and Ailerons completely to the left, it will be more like RL.
This is also a factor where the 27 will (probably) beat the ASW22

[Fox9]

We can make a long theoretical discussion, but I think it's the best
way to find out, is to fly the task with both planes. That was my original
intension, when I made this topic.

Fox9

[TimKuijpers]

Ok, but the first thing you learn in phisics class is that you have to compare with equal circumstances (spelling?).
What you did on the first leg with the asw27 is that you turned way more then you did with the 22.
Think this made the 27 loose.
There is some point where the 27 becomes better then the 22,
You wan't to take this into practice, but you will have to fly with Mc3, Mc4, and Mc5
Then you know id the polars are right.
But could you still send me the IGC files?

[Fox9]

Hello Tim (and all others),

In the attachment you can find the IGC-files of the ASW22 and ASW27 flights
and the flightplan (is identical for both flights except the plane type). The water
ballast for the ASW22 was 120 kg and for the ASW27 95 kg, that means 50%
of the maximum.
People with StrePla, SeeYou or a similar program can evaluate the flights and
find out, why the ASW22 was faster. Also you have the oppertunity to make
your own flights.

Best regards
Fox9

[kaleu]

Hi,

I looked at the flights and in my opinion the main reason for the "defeat" of the ASW27 was that you didn't get the thermals at the beginning of the first leg and so became too low in a area where you flew very fast and with many good thermals in the ASW22. A second reason is that the you seem (as you said) not to feel comfortable with the ASW27 while thermaling. It seems that you didn't get the thermals correctly and again and again flew outside the thermal in parts of the circle.

But I also think that you flew a much better way with ASW27 on the last leg so I think the ASW22 aslo could've been faster with a better way on the last leg.

[Fox9]

Hello Kaleu,

Comparing the 2 flights you must consider the altitudes
at the begin and end of a leg. The difference dAlt are
shown in the flight summary. On the 1. leg, dAlt of the
ASW27 is 1205 m and 512 m for the ASW22. That means, the
ASW27 is about 700 m higher then the ASW22 when turning
the 1. TP. Therefore the difference of the speed
(ASW27: 103 km/h, ASW22: 130 km/h) to a great part is
due to the additional altitude of the ASW27.
On the following legs the ASW27 can profit from the altitude
at the 1. TP. Therefore the ASW27-Speed are higher. But the
complete flights shows, the ASW22 was faster.
In my eyes the mainly point is the better climbrate of the
ASW22. Take a look on the polares in the attachment. The
average speed (the point where the tangent crosses the
v axes) of the ASW27 at a CR of 2.1 m/s is 107 km/h, the
average speed of the ASW22 at a CR of 2.6 is 110 km/h.

But all theory is grey ....! The great advantage of a
simulator is, that everybody can make the flights under the
same conditions and so find out what plane in this special
case is faster. I wait for your flighttracks or IGC-files.

Best regards
Fox9