Facebook

Login

Support Sailonline

If you haven't already - join the SAILONLINE YACHT CLUB!

Please also consider making a donation - all amounts are greatly appreciated!

Board » Technical Discussion » Performance loss

Page: Previous 1 2 3 4 5 6 7 Next Last

I have been exploring the rate of recovery of "perf" after a gybe of 270 degrees at a speed of 25-26 knots. The rate of recovery is linear, but has two components. It required 20 minutes to recover, but for the first 16 minutes the rate of recovery was 0.4% per minute. For the last 4min, the rate was0.74% / minute.
After a gybe of 180deg, at the same speed, it required 23 minute, at a rate of 0.52% per min for the first 15.5 min, and then a rate of 0.90% / min for the last 7 minutes.
I can see no reason for either the greater loss for the lesser turn, or for the changes in recovery rate that were observed.
I will continue to collect data.
As Alice said, "This is getting curiouser and curiouser!"
p.s. I think it was Alice (of Wonderland fame,) but I'm not certain....

--- Last Edited by Rod at 2013-10-11 21:48:54 ---
If it breaks, it's not strong enough--if it doesn't, it's too heavy.
This peace of code does not include performance recovery.

As far as I can tell from this code, it doesn't matter if you gybe from twa=155 to twa=-155, or from twa=175 to twa=-175. performance is in boat gybe half you boat speed.

What is possible (what I believe hmm did) is to change course to twa=179 (slow) then gybe to best VMG (low performance loss because low boat speed.

With the tall ships you might be able to tack with almost no performance loss: you're sailing with twa=70, change course to twa=(about)50, so that you boat speed is (almost) 0. Then tack to twa=-70 (no extra performance loss). I'm not sure whether 10 seconds with speed=0 is better than a little more performance loss.

This makes me think... tall ships can sail backwards.. tacking when you're speed is negative should increase performance according to this code. In the most extreme case you could sail with -0.373 kts backwards, tack an have a performance of 100.19%. It's quite possible that there's something in the performance recovery code that prevents the performance from exceeding 100%.

EDIT: Currently trying these things.. I'm wrong on at least one point: it the boatspeed *after* the tack/gybe that determines performance loss.

EDIT:
There are still weird things going on. In the tall ships race, there's not enough wind to go "fast" backwards. I was not able to get performance above 100% It might be possible to speed up de performance recovery (with the negative speed trick), but I can't measure that now (I can only do a 0.02% increment).
I noticed something weird with speeds <= 0. Somehow, if you tack, and your speed after the tack is smaller of equal to 0, your performance is 100% immediately. When you change course (don't tack or gybe) to an angle with a boatspeed smaller or equal to 0, your performance recovers very fast. Has boatspeed something to do with performance recovery? That would explain why fast boats have slow recovery.

--
It's not that one of these things would make you any faster, but while discovering how SOL works, we might find some things that do make you faster. These performance things might be very interesting for practice racers (like me) :)

--- Last Edited by kroppyer at 2013-10-11 22:10:37 ---

--- Last Edited by kroppyer at 2013-10-11 22:27:13 ---
Ok so if its the speed after the G/T then could the flat turn gybe that hmm did at Digby be 1st to just do a change sign at 179.99 then go to VMG ?
None so blind
Yes, at this point I think something like this happened:
twa=145
twa=-179.99 (speed: 17.3 kts, perf.: 91.35%)
twa=-145 (no additional perf. loss because perf<93%)

===(edit)===
Let me add a "translation" for those not familiar with programming.

Now e is a percentage (0-100%), boatspeed is in knots, dTWA is positive difference in course, in degrees (I believe dTWA was in radians in the original code).

---
If (tack or gybe (twa changes sign))
then
e = 100 - boatspeed/2
else
e = 100 - dTWA*180/(25*PI)
end

perf = perf*(e/100).
---

There is something with the recovery though, sometimes the performance loss is very low or not even noticeable. I think this is because recovery is very fast when boat speed is low.

--- Last Edited by kroppyer at 2013-10-12 08:09:20 ---

--- Last Edited by kroppyer at 2013-10-12 08:11:23 ---
What is " PI "????
If it breaks, it's not strong enough--if it doesn't, it's too heavy.
What is " PI "????
PI = 3.141592...

Probably that is because dTWA is in radians.
Complicateder and complicateder---"Radians"?
If it breaks, it's not strong enough--if it doesn't, it's too heavy.
I found this graphic that I snagged in the past that was posted here in the Forum. Unfortunately I don't know who provided it but it does relate to Boat Speed recovery.

The url where it was linked from is no longer valid but this is the defunct location.

http://farm3.staticflicker.com
(space added)
/2357/2063504228_33f768fe40.jpg

By looking at the graph axis labels 'e' stands for efficiency in the formulas that are under discussion.

This is not definitive but it is a start
None so blind
Attachments
Rod, you know you have a computer in front of you which has the ability for search for information?

Whether you like it or not, simulating the performance requires mathematics. And if you want to understand that, you should be aware of some basic mathematical terms like "pi" and "radian".

The answer is the first hit google gives you for "radians".


I know Pi and radians, but is it necessary for the calculation? It's a long time since I did a lot of math, and I'm sure many SOLers don't even remember as little as I do about how to manipulate radians in an equation. I will persist......
If it breaks, it's not strong enough--if it doesn't, it's too heavy.

Page: Previous 1 2 3 4 5 6 7 Next Last

Please login to post a reply.

Races

Next Race: 00d 00h 00m


Current Races:

Christmas(W) to Christmas(E) Island 2024

Two waypoints, start and finish, and between them 5827 NM of two oceans. Not much time if we want to sit at the Christmas Eve table. You will need to maintain an average speed of over 10 knots, so prepare your 90ft well and choose the best of the many possible routes. Hands up everyone who knew there were TWO Christmas Islands?! OK, maybe you have sailed this Sailonline course before... but it's time to get ready for the 2024 challenge of a reversed race, starting in the Indian Ocean, racing to the Christmas Island in the Pacific! It also marks the conclusion of our prestigious Ocean Race Championship 2024. Please have fun! Fair winds!
PRIZE: SMPF
Race #1868
INFO by brainaid.de
90ft Monohull PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: OCQ4 - OCCH - SUPSOL - SYC
Race starts: Dec 02nd 11:00 Registration Open!
▶ Flash
GO TO RACE

The Beagle in Mauritius 2024


And west, forever following the sun, the Beagle went once more to next explore Australia, but since online we already regularly race the length and breadth of that wee dinkum continent’s coasts, we will delay launching our Tall Ship Class B until the Beagle reaches Mauritius, which she did on 29 April 1836. Darwin explored the island and its coral reefs extensively. We’ll better that by sailing some 450nm to Reunion and back, for a better appreciation of this remote archipelago, inhabited mostly by descendants of French and English colonists and Indian convicts and political prisoners.
Race #1757
INFOby brainaid.de
Tall Ship Class B PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SVF - SYC
RACE CLOSE: Saturday,
December 7 at 2300 UTC.
Race starts: Nov 27th 13:00 Registration Open!
▶ Flash
GO TO RACE

Kapiti Chetwodes Race 2024


For only the second time in SOL history, we have the pleasure of inviting you to the Kapiti Chetwodes Race, held in the Cook Strait region. Organised IRL by the Royal Port Nicholson Yacht Club from Wellington in New Zealand. The approximately 160nm long route, full of turning points, will take us from the bay at RPNYC around the islands of Somes, Kapiti and Chetwodes and back to the finish line at RPNYC. We have only a 26 ft Albin 79 yacht at our disposal. All this means that we will have a lot of fun, so fair winds!
Race #1864
INFO by brainaid.de
Albin 79 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
ARQ4 - ARCH - SUPSOL - SYC
RACE CLOSE: Monday,
December 2 at 2300 UTC.
Race starts: Nov 25th 17:00 Registration Closed
▶ Flash
GO TO RACE

Nassau to Bodo 2024

Prepare for the grand finale - the 6th and concluding leg of the RTW challenge, an odyssey from Nassau in the Caribbean to Bodø in Norway. Embracing a journey of 4000 nautical miles, this leg promises an exhilarating 18-day voyage. It also heralds the November installment of our prestigious Ocean Race Championship. Embark on a voyage of a lifetime, where prowess, tactics, and camaraderie unite in the pursuit of triumph. We eagerly await your presence at the starting line! May the winds be ever in your favor.
PRIZE: SMPF
Race# 1866
INFO from brainaid.de
Swan 65 PARTICULARS
WX updates:
0430 / 1030 / 1630 / 2230
Ranking: OCQ4 - OCCH - RTW - SUPSOL - SYC
RACE CLOSE: Friday,
December 6 at 2300 UTC.
Race starts: Nov 11th 11:00 Registration Closed
▶ Flash
GO TO RACE

Go to race archive

SYC Ranking

  1. Sailonline Yacht Club Member WRmirekd
  2. Sailonline Yacht Club Member FreyjaUSA
  3. Sailonline Yacht Club Member Vida_Maldita
  4. Sailonline Yacht Club Member CriticalHippo
  5. Sailonline Yacht Club Member rafa
  6. Sailonline Yacht Club Member Kipper1258
  7. Sailonline Yacht Club Member Satori
  8. Sailonline Yacht Club Member Sax747
  9. Sailonline Yacht Club Member CollegeFund
  10. Sailonline Yacht Club Member QMaxx

View full list

Series

Mobile Client

SYC members have the benefit of access to our mobile/lightweight web client!

The mobile client