Hi Cata.  Your big challenge is the disparity in speed between the Optimist and the others.  In practice, you may be better off running a pursuit race.  The start times are easy to calculate for only three classes and the link on the page you reference gives good examples on how to run a pursuit race.  I recommend using a patrol boat to record positions when the race time expires.

A pursuit race doesn't really help with the big disparity in times. If the optimist has a 30 minute race the fastest boats might have 15. What I suggest is best is to run average lap racing. With this you have plenty of short laps and count them, and if the oppie does 2 laps and the 420 5 then you multiply the oppies time by 5/2 before scoring. Most handicap capable scoring systems can do this for you, or do it yourself with a spreadsheet, whatever. 

Setting up. Ideally you want the majority of the slowest boats to do at least 3 laps, because otherwise wind changes and other odd events can produce unsatisfactory results. You also want the boats to start and finish on the same line, and go through the line on each lap. So you need to set a course that is a suitable length and has the line as required. A quadrilateral with the line about 100metres to windward of the leeward mark is a pretty safe choice, but provided the slow boats get 3 laps in you can make it as complicated as you like. 

Running the race. Depending on how many boats you have you can start everyone together or in classes/bands. I'd be inclined to send 420s off first, then Lasers then Opppies at two minute intervals, but really doesn't matter, just get the start times. Don't bother to set a number of laps, you want then to race until you hoist the S flag. It's a good idea to record the time of every boat through every lap if you can. 

Finishing. You get better at this with practice, but in an ideal world you want the majority of each fleet to finish after the same number of laps be it 3 for Oppies, 6 for Lasers, 7 for 420s or what. So you watch the leader in each fleet, and shorten the course in front of one. You then finish every boat the next time it comes through the line. 

Results. Sailwave or whatever will automate this, but basically you now have a list of elapsed times for each boat with a number of laps against each one. Convert elapsed times to seconds, not forgetting to apply an offset if the starts were staggered. Look at the results for the boat that did most laps, and make a note of that. Multiply each boats elapsed time by the max laps, and divide by the number of laps they actually did. No need to do this for boats that did the max laps. You now have a list of times that each boat would have achieved had it kept sailing at the same speed for the max laps. Divide each time by the handicap figure and multiply by 1000 and you have corrected times. Now sort them and of course lowest time wins. You don't use the times you recorded on each lap, they are just a reference if something goes wrong. Giving the RC the task of recording times means they are less likely to miscount someone's laps. 

This is how a lot of UK clubs run races for handicap fleets with widely varying handicaps. The knack is picking the shorten course point so as many as possible in each fleet do the same number of laps. Note that you don't have to finish fast boats before slower ones. 

Cata,

Can you tell us a bit more about the event.

I assume you want boats of all classes to compete against one another on handicap.  PY should do that just fine.  I don't think 'disparity' should be an issue except that if you have multiple races the fast boats will be hanging around waiting for the Optis to finish before you can start the next race.  If only 1 race, this is not a problem.

IMHO average lap racing and finish in place are too complicated.  Use 1 start, one course and one finishing line, then correct the times using the PY.

Average laps, 3 laps for Optis, 30 minute race time, that's 200m legs.  That's not a race that's a starting and Mark rounding drill.

Thanks for your comments Jim, Graham and John.
As you have seen, I don't know the subject......so i need a simple way.

STEP 1
For example if I use this method that John says:
  "Use 1 start, one course and one finishing line, then correct the times using the PY."

@John Allan

STEP 2
And then i can study the other methods @Graham Smith and @Jim Champ

THANKS YOU SO MUCH
Cata

Cata

Your easy approach to thisbis a triangle or trapezoid course with the committee boat 1/3rd way up the beat.

You set everyone off together.

You could laps and time the race.

You either manually calculate a average lap time or let some software sort it, then adjust for the handicap.  Something like Sailwave will do the calcs for you

I've run mixed fleet dinghy racing for juniors several times and had very satisfactory results with an average lap time approach:-
1) Everyone starts together and does the same course, short enough for the Opies (smallest boats) to do a couple of laps 
2) Finish everyone crossing the line after your chosen time - say 20-25 minutes (ideally when the lead Opie is coming up to the end of a lap)
3) Calculate everyones corrected time using PY formula 
4) Divide corrected time by number of laps each individual did to get average lap time & thus ranking.

I think Sailwave can do this for you otherwise I've built spreadsheets to do the job myself.
Good luck - perfectly acceptable for club racing IMHO

If you want to do a pursuit you can quickly estimate suitable start times in your head.

Take the PY no and knock off the last digit. Round up or down based on last no.
That number will be a 1 hour race in half minutes. A 1200 PY would give a 120 half minutes which is 60 minutes or 1 hour.
For half hour race divide by 2 twice.

A Topper at 1364 PY would be 136 divide by 2 = 68 divide by 2 = 34 minutes start time.

A laser at 1100 PY would be 110 divide by 2 = 55 minutes for 1 hour race or 55 divide by 2 = 27.5 minutes for half hour race.

We do pursuits using a clever box a member built which gives count down in half minutes.

We sometimes do a handicap race in the morning and calculate average lap times. Using that we can calculate suitable times for an afternoon pursuit race on a personal handicap basis. It's even simple to give the slow boats one or two laps start plus a personal pursuit start time to make the start sequence much shorter.

We have a start finish line by the committee boat but place the last mark of the course behind it. They start at the line  but we do individual lap times as they round that mark and they are not required to go through the start/finish line each lap. 

On the final lap they must go through the line so we raise a flag and give a hoot as they pass the mark behind the line. That removes rules problems with S/F lines in the course.

Basically we can finish a race at any time but carefully plan when. We want to finish the lead boat first but if we have a slow boat with a long lap time we will finish them first.

How often in a fleet race is the first boat and the second boat more than 30s apart?

For this reason I'm a fan of to the second pursuit races.   You wouldn't accept a handicap race where the finishes are recorded as 'aboit 20 minutes'

If your pursuit is 30mins, to 30s segments become even more significant. 

I'm also a firm believer that the race should end at the stated time, not when the lead boat then crosses the line. So the finish line is effective "dropped" directly in front of the road boat and preferably moved backwards through the fleet as quickly as possible...

Thank you very much to everyone who is helping me with this very interesting topic.
I read carefully every line you write to me.
I want to ask you some very simple questions:

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N°1
In case of "pursuit race"
"The start times are easy to calculate for only three classes"

Can you @Graham Smith give me an exaple for Opti, Laser & 420 ?
I can get the PN of each class in the list but I don't know,  how to use the FORMULA.....which formula ?

Optimist:      1635   /     -7
Laser 4.7:     1210  /      2     
420:              1100  /     -5
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@Jim Champ
@Richard Jones
@John Allan
@Calum Polwart
@Andrew Wise
@Calum Polwart

For a standard 30minute race duration (Oppie does 30minutes), others chase you'd be looking at: (according to DSRC app)

Oppie starts first
Laser starts 7m 54s later
420 starts 9m 55s after Opi start 

The maths should be something like:

ThisHandicap
----------------------  x race duration in seconds
SlowestHandicap

Tells you how many seconds later they should be able to do it in

So
1100/1635 x (30 x 60) = 1211

Race is 1800s so they start 1800-1211 later... 589s later, 9mins 49s

Notice a 6s difference... I suspect that's a rounding thing! 

Richard's approach is not to make the race 30m for the optimist but for a fictitious boat that sits somewhere in the PY range I think. 

So he is saying:
1635 becomes 164/4 = 41minute race
1210 becomes 121/4 = 30.25min race
1100 becomes 110/4 = 27.5 min race.

It's quite a neat way to do the maths and means the race stays ~ 30min even if the oppi doesn't show up. But it does mean the Oppi is actually doing 41m! Slower, younger sailor suffers?

If I set exact starts on DSRC with 41m race duration - I get laser 10m 48s later - seems to match, 420 13m33s after Oppi again seems to be right.

My only question for Richard is how he that handles race timing. Do you do 5-4-1-0 for the Oppi or do you publish a race time day "Race will.start at 14:30:00 exactly." Which is presumably the time for a PY1200 boat and then tell people to start earlier or later?  RC need to be bang on the money with their course etc being all sorted. But you can't control for an external thing like weather... I can only imagine 1 HR postponement being the only practical solution...  Unless you have a big clock on the committee boat...

THANKS TO ALL FOR THE HELP !!!
Next Friday we will do the first regatta at school.
I'll tell you !!

@Graham Smith
@Jim Champ
@Richard Jones
@John Allan
@Calum Polwart
@Andrew Wise
@Calum Polwart

Hi Callum and Catalan.
We use a modified 5 2 1 0 start countdown for the slowest boat. 
The race will be scheduled at say 2.00pm. The RC will have set the course up, anchor the RC boat etc then come ashore in the safety boat to  mark up the course board, collect race sheet etc. They often put the slowest boat class and start number on the course board  so everyone knows. They will have a look round, make sure most are ready and have a word with the slow boats to let them know they are going to start.

Then they go to the already set up RC boat and when the slow boats are there will start the count down with flags etc. The race will then start.
Its up to the faster boats to launch and go out in time.

The start box we use has a large screen approx 4 feet x 2 feet so is visible from a large area. RC enters the slowest boat start number, the box adds on the 5 minutes and starts counting down. If that count down starts at 140 (half minutes) it will keep counting and hooting down to zero then hoot and flash lights and display END.   Hoots automatically end at 100 (50 mins) to please neighbours.

The start box and screen sit on a trolley which also has all the RC equipment. It can sit on the end of the pontoon and we can use 2 pontoons as a start line so can have pursuit races with no RC at all. This happens a lot. It can also be placed on a rotatable frame on top of the RC boat roof so yes, everyone can see it from the start line. There's also a repeater screen outside the club house displaying the number. 

Our half minute system actually only has a 15 second max discrepancy due to the round up or down. When you wee its based on PYs there is a massive variation in how accurate PYs are for all venues, conditions and sailors cheque book size etc.

I mentioned the modified 5410 start. We use a 4 2  go sequence. It lets us get classes away at 2 minute intervals
4 HC class flag up
2 P flag  and Laser flag up
0 HC flag down and start. Solo Flag up 
+2 Laser flag down and start
+4 Solo and P flags down and start
etc....

We use 5410 for opens etc.

If our start box doesn't work we do the flags and use a manual hoot. We hoot for every start number change and call out the new number until the last boat starts.

You could do this for the Oppis and perhaps do the flag and hoot count down again for for the 420s etc. due to the large gap

This is a race in our club in 2019....was so funny !!
The picture is close to the finish line.
The wind was blowing at 7 kts and at the finish line  it dropped to 3 kts

This is the Excell i'll use next time for PURSUIT RACE