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

Posted by
Rod


Users avatar

Posts
392
Registered at
2010-06-24 22:30:48
2013-10-11 21:46:48 - Re: Performance loss
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.
Posted by
kroppyer


Users avatar

Posts
347
Registered at
2010-02-05 15:25:55
2013-10-11 21:59:21 - Re: Performance loss
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 ---
Posted by
A2


Users avatar

Posts
347
Registered at
2009-10-26 00:39:42
2013-10-11 22:41:35 - Re: Performance loss
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
Posted by
kroppyer


Users avatar

Posts
347
Registered at
2010-02-05 15:25:55
2013-10-11 22:59:14 - Re: Performance loss
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 ---
Posted by
Rod


Users avatar

Posts
392
Registered at
2010-06-24 22:30:48
2013-10-12 13:49:52 - Re: Performance loss
What is " PI "????
If it breaks, it's not strong enough--if it doesn't, it's too heavy.
Posted by
hmm


Users avatar

Posts
118
Registered at
2011-11-03 13:35:22
2013-10-12 14:00:08 - Re: Performance loss
Rod said @ 2013-10-12 13:49:52:
What is " PI "????
PI = 3.141592...

Probably that is because dTWA is in radians.
Posted by
Rod


Users avatar

Posts
392
Registered at
2010-06-24 22:30:48
2013-10-12 15:35:10 - Re: Performance loss
Complicateder and complicateder---"Radians"?
If it breaks, it's not strong enough--if it doesn't, it's too heavy.
Posted by
A2


Users avatar

Posts
347
Registered at
2009-10-26 00:39:42
2013-10-12 15:41:15 - Re: Performance loss
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
Posted by
hmm


Users avatar

Posts
118
Registered at
2011-11-03 13:35:22
2013-10-12 15:44:54 - Re: Performance loss
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".


Posted by
Rod


Users avatar

Posts
392
Registered at
2010-06-24 22:30:48
2013-10-12 21:44:29 - Re: Performance loss
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:

Great Nicobar to Marion Island 2025

The Adventure Continues – Leg #6 of the RWW Series.
We’re setting sail on the next stage of the RWW Series: a 4,400-nautical-mile passage from Great Nicobar to Marion Island. This demanding leg will test endurance, strategy, and seamanship at the highest level. As part of the 2025 Ocean Championship, this marks the ninth legendary challenge in the series — and one of the most exhilarating yet. The race will be contested aboard the Archer 78’ ketch, a vessel built to push sailors to their limits across the vast Indian Ocean.
PRIZE: SMPF
Race #1900
INFO by brainaid.de
Archer 78 PARTICULARS    
WX Updates:
0430 / 1030 / 1630 / 2230    
Ranking: OCQ3 - RWW - OCCH - SUPSOL - SYC
Race starts: Sep 01st 11:00 Registration Open!
▶ Flash
GO TO RACE

SSANZ Triple Series 2025 - Race 3

Welcome to the grand finale of this year's SSANZ Triple Series! The stage is set for the Lewmar 50, a thrilling 39nm challenge tracing the southern shores of the stunning Waiheke Island, pushing out to Tarahiki before the sprint back to Islington Bay. Expect fast legs, tactical battles, and no shortage of drama as our SOLers take on the waters in their Young 88s, lining up once again against the talented IRL members of the Young 88 Association. With the series on the line and everything still to fight for, it all comes down to this final race!
Race #1934
INFO by brainaid.de
Young 88 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
SSANZ - SYC
Race starts: Aug 29th 21:15 Registration Open!
▶ Flash
GO TO RACE

Red Eye - Myth of Malham 2025

In 1947, Hugh McLean & Sons of Gourock, Scotland built a radical racing yacht for John Illingworth, soon-to-be Commodore of the RORC, to a design by Laurent Giles. With a masthead rig, giving her ‘free’ sail area per the rules of the time, and short overhangs reducing pitching, Myth of Malham went on to win The Fastnet that year and again in 1949, and to compete in numerous Admiral's Cups. In 1958, in honour of the yacht, the Myth of Malham race was conceived - a mini-Fastnet to the first lighthouse on a rock west of Cowes, Eddystone, rather than the second, to be held in non-Fastnet years. IRL this year it has been raced already, but this stops us not from “Red Eye” racing its online 230nm in Fareast 31Rs, leaving how to deal with the Isle of Wight open to your own discretion.
Race #1847
INFOby brainaid.de
Fareast 31R PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC - RED
RACE CLOSE: Monday,
September 1 at 2300 UTC.
Race starts: Aug 25th 12:00 Registration Open!
▶ Flash
GO TO RACE

Africa by Sea 2025 - Maputo to Mogadishu


The fifth leg of our exploration of Africa By Sea takes us north along the length of the Continent’s succulent sub-tropical and tropical Indian Ocean coast. Much fought over by traders and colonists both well-before and after a Portuguese expedition under the command of Vasco da Gama first sailed there from Europe back in the 16th century, it is yet to be properly explored as a yachting destination. With plenty of islands off- and inshore, small and very large, there is much to interrupt your 1900nm voyage and visit in your Swan 65, from Maputo to Mogadishu! Race #1858
INFOby brainaid.de
Swan 65 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC - ABS
RACE CLOSE: Saturday,
September 6 at 2300 UTC.
Race starts: Aug 20th 17:00 Registration Closed
▶ Flash
GO TO RACE

Go to race archive

SYC Ranking

  1. Sailonline Yacht Club Member WRmirekd
  2. Sailonline Yacht Club Member vida
  3. Sailonline Yacht Club Member CriticalHippo
  4. Sailonline Yacht Club Member KaSToR
  5. Sailonline Yacht Club Member rafa
  6. Sailonline Yacht Club Member Kipper1258
  7. Sailonline Yacht Club Member Sax747
  8. Sailonline Yacht Club Member BRENTGRAY
  9. Sailonline Yacht Club Member CollegeFund
  10. Sailonline Yacht Club Member FreyjaUSA

View full list

Series

Mobile Client

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

The mobile client