Does this exist-- program to generate speed-to-fly table?

Here's what I want to do:

Input a minimum-sink-rate data point plus one or two other data points to establish a polar curve for a particular glider.

Have a computer program spit out a table showing the best airspeed to fly for variometer readings (not netto) of 200 fpm down, 300 fpm down, 400 fpm down, etc up to 1500 fpm down, for 0 mph headwind, 10 mph headwind, 20 mph headwind, and 30 mph headwind.

I only want to consider the best glide over the ground, not the best cross-country speed. I.e. a MacCready ring setting of zero.

This is to make a handy paper MacCready ring thing (but not moveable, and only a half a circle not a full circle) to tape around the vario of rented, borrowed, or club gliders. The arc will have three sets of numbers around it, corresponding to the 0 mph headwind, 10 mph headwind, 20 mph headwind, and 30 mph headwind cases.

Does such a program exist?

One speed-to-fly-explanation website says that "A really desperate pilot should set the ring to zero to maximize the area to be searched for a thermal.. ", so I guess I am a really desperate pilot, to be requesting such a thing...

S

I don't know of such a program, but you might want to rethink your approach. It doesn't take into account areas of sink or the effects of a headwind.

I suggest you read Reichmann (or maybe it was Cochrane) for his discussion on why 0 MacReady is never the right value unless the air is void of all motion.

I have an excel spreadsheet that does what you want. Mine gives a table of speed to fly at three different wing loadings. I can send you the excel file but it was not designed for others to use. Alternately you can send me info about your glider and I can set it up for you and send it back.

Tim

If you use XCSoar, it provides a Speed to Fly info box.

On 6/9/2015 11:04 PM, Tim Taylor wrote:
I have an excel spreadsheet that does what you want. Mine gives a table of speed to fly at three different wing loadings. I can send you the excel file but it was not designed for others to use. Alternately you can send me info about your glider and I can set it up for you and send it back.

Tim

--
Dan Marotta

The Speed to fly functionality of the ClearNav vario works pretty well for giving you a speed to fly number based on the current conditions. I don't constantly chase the number it displays, but it is a good number to work off of.

SF

On Wednesday, June 10, 2015 at 9:07:21 AM UTC-7, SF wrote:
The Speed to fly functionality of the ClearNav vario works pretty well for giving you a speed to fly number based on the current conditions. I don't constantly chase the number it displays, but it is a good number to work off of.


Somehow, suggesting a ClearNav (or even XCSoar) to someone who is talking about making paper speed rings for club gliders doesn't seem reasonable, but I guess I'm behind the times.

For the original poster, Paul Remde has an good assortment of soaring related spreadsheets he

https://www.cumulus-soaring.com/soar...ring_files.htm

In particular, polar6th.xls does pretty much what you want. There is also this web app:

https://www.stolaf.edu/people/hansonr/soaring/spd2fly/

Marc

On Wednesday, June 10, 2015 at 12:36:34 PM UTC-4, wrote:
On Wednesday, June 10, 2015 at 9:07:21 AM UTC-7, SF wrote:
The Speed to fly functionality of the ClearNav vario works pretty well for giving you a speed to fly number based on the current conditions. I don't constantly chase the number it displays, but it is a good number to work off of.


Somehow, suggesting a ClearNav (or even XCSoar) to someone who is talking about making paper speed rings for club gliders doesn't seem reasonable, but I guess I'm behind the times.

For the original poster, Paul Remde has an good assortment of soaring related spreadsheets he

https://www.cumulus-soaring.com/soar...ring_files.htm

In particular, polar6th.xls does pretty much what you want. There is also this web app:

https://www.stolaf.edu/people/hansonr/soaring/spd2fly/

Marc

Agreed, I believe the OP stated this was for club ships and/or "just hopping in for a flight". Thus, may not have access to much more than basic instruments in these cases.

On Tuesday, June 9, 2015 at 11:06:13 PM UTC-5, SoaringXCellence wrote:
I don't know of such a program, but you might want to rethink your approach. It doesn't take into account areas of sink or the effects of a headwind.

I suggest you read Reichmann (or maybe it was Cochrane) for his discussion on why 0 MacReady is never the right value unless the air is void of all motion.

Sink or headwind is exactly what I want to take into account, that's the whole point! Was I unclear on the original post?

If you are trying to race along at an optimal cross-county speed then there's room for all kinds of nuanced discussions around how the basic MacCready theory falls short but if you are just trying to make the flattest possible glide toward the next thermal, given the existing sink and headwind, I don't think there is much rocket science to it is there? Draw the tangent line tothe polar curve, starting at the appropriate point to take into account sink and headwind.

But sure I'd be interested to read anything for more illumination, can you give titles as well as authors?

Anyway, I wrote a program to do exactly this years ago (and it also spit out the corresponding values for non-zero MacCready settings) but I don't have access to it now... someday I will resurrect it but it might be many months before I can tackle that.

S

On Wednesday, June 10, 2015 at 1:43:44 PM UTC-5, wrote:

Sink or headwind is exactly what I want to take into account, that's the whole point! Was I unclear on the original post?

As a matter of fact, your initial post was not clear. You said you wanted to know the best speed to fly for a variometer reading of 200 feet per minute down (not netto). Well, what is the air doing then? You could be flying 60 knots or 120 knots to get a variometer showing 200 feet per minute down (not netto), depending on what the air is doing. Or, you may not ever be able to get the variometer to show that little down. If the word "Not" slipped in there unexpectedly, your question becomes more clear. And that is what I assumed you meant.

No real need for a computer program to make this table. And I would make a simple table. It is not a ring you place around a variometer. You have the polar, you know the theory, you drew the lines, why not just type up the table?

Best L/D, no wind, for air going down 100 feet per minute is the line from the zero horizontal speed, 100 foot per minute vertical speed (on the opposite side from your polar), tangent to the polar. You can see the speed you should fly (tangent point), and the L/D you will make good (basically, horizontal speed divided by vertical speed). Headwinds move the origin point of your line towards your polar, tailwinds move the origin point away from your polar. For L/D with headwind or tailwind, you have to subtract or add, respectively, wind speed from or to flight speed to get ground speed to calculate L/D.

Can I ask why you want to make a program to create something you can create in less than 10 minutes, including time to type it up? The program won't likely save you much time in making the chart for a second, third, or fourth plane, as you still have to find the polar, pull data from it, enter it into the program, see that the polar it draws sort of matches what you see from your data source, and then trust the results. And if you make a ring, what happens when you go to a glider with a different number of degrees between each 100 ft/min increment in lift or sink?

My advice would be to make a simple table, not a ring. Put it on card stock and encase it in plastic (waterproof it). Tape it to the panel when you fly.

Just my 2 cents worth. BTW, I could have made a couple of those tables in the time I have spent typing this. :-)

Steve Leonard

True, but I have a copy of XCSoar on my Android phone and it's always
with me...

On 6/10/2015 12:43 PM, Charlie M. (UH & 002 owner/pilot) wrote:
On Wednesday, June 10, 2015 at 12:36:34 PM UTC-4, wrote:
On Wednesday, June 10, 2015 at 9:07:21 AM UTC-7, SF wrote:
The Speed to fly functionality of the ClearNav vario works pretty well for giving you a speed to fly number based on the current conditions. I don't constantly chase the number it displays, but it is a good number to work off of.

Somehow, suggesting a ClearNav (or even XCSoar) to someone who is talking about making paper speed rings for club gliders doesn't seem reasonable, but I guess I'm behind the times.

For the original poster, Paul Remde has an good assortment of soaring related spreadsheets he

https://www.cumulus-soaring.com/soar...ring_files.htm

In particular, polar6th.xls does pretty much what you want. There is also this web app:

https://www.stolaf.edu/people/hansonr/soaring/spd2fly/

Marc
Agreed, I believe the OP stated this was for club ships and/or "just hopping in for a flight". Thus, may not have access to much more than basic instruments in these cases.

--
Dan Marotta