Portsmouth or SCHRS ???

Eric, do you have a copy of the class rules? I looked online and didn't find them.

I sent you a PM

Bingo...

I would like to see SCHRS become the norm; however, as I stated earlier, not many folks are going to perform the gymnastics needed to get their boats in compliance should the have altered the sail plan etc... as they are the once or twice a year racers... And in our case many of them are Frankenboats.

I think this needs to be handled by each race committee noting on the NOR that you're using SCHRS for the rating system. And if you're not compliant with measurement to your modifications than a X% penalty will be applied until you can either a.) furnish a measurement certificate, or b.) measurements from your sail maker that can be plugged into the on-line calculator where an agreeable rating number can be assigned.

On another note, I agree, it really shouldn't be that hard to be in compliance. With most of the modifications that come into play are with sails many times going from a pin to a square top, getting the numbers from any sail maker shouldn't be that difficult. My question would be are the

reputable

sail makers of our community in tune with the SCHRS requirement for measurement? And, if so could/would they include a measurement sheet with the purchase of a new set of sails?

Here is the latest SCHRS to PY chart I could find: https://www.schrs.com/pylookalike.php

Here is a complete reference for Portsmouth Yardstick: http://www.ussailing.org/racing/offshore-big-boats/rating-rules/#1471969539173-9c4d8bd4-7aff

These sources should help a lot to rate different boats.

Ventucky Red,

The answer is yes. Glaser for example will include a F18 measurement form with their sails, they are certified class measurers on the F18 side and I would fully trust them to provide accurate sail area data to compute a SCHRS rating. Any of the lofts building A-Cat sails should also be capable of the same.

One issue with the SCHRS rating scheme is the mainsail area includes the mast. So you need to measure the mast area. That is pretty straightforward. It helps to look at the F18 measurement certificate which clearly outlines how to measure sails and the mast. The US F18 class website also has detailed photographs of sail measurement. Its about 1 hr for a 3 sail boat.

Jake,

I hear you, but applying DPN corrections to SCHRS doesn't work. We've played this game locally. Get your sail area if that is the change and run the calculator. It is easy because the numbers for almost every boat are readily available online, type those into the excel calculator and update the sail area. I do this for our fleet, maybe you can designate someone for your local fleet?

Eric,

Unfortunately SCHRS doesn't differentiate between pinhead or square top sails etc. They do have a sinking correction factor which I think you should use for the Isotope, and on the 2018 rating calculator this gives you a SCHRS number of 1.072, quite a bit slower than a 1 up F16 (1.041). Without this I get a number of 1.057, again relatively slower than a 1 up F16. I used a board depth below waterline of 0.56 m, the number for the Taipan 4.9 (which in stock configuration has very short and stubby boards). You didn't post a number from what I can tell, so that may be part of your ratings issue. Personally I feel the 1.057 number is a fair rating considering the following statement on the Isotope website:

The Isotope Catamaran is a registered Formula 16 boat!
The hulls meet the 16ft LOA requirements of the Formula 16HP class. The strong points of the Isotope are that its balanced helm allows it to out point any other catamaran to windward. An Isotope meeting the One Design class specifications can be raced as a single handed Formula 16 boat. An Isotope with a spinnaker can be raced with crew in the Formula 16 one up class.

If the hull doesn't plane, maybe the 1.072 number is fair, maybe. How does the boat sail compared against a 1 up Blade, Falcon, Viper or Nacra F16?

-Sam

I hesitate to resurrect this discussion, since I've already gone into details at https://www.catsailor.com/forums/ub... ds/%2Bschrs/Search/true/schrs#Post282859, but:

Really? Then what is LTM (length of top of mainsail) for?

SH (sinking hull) is

only for HC14, HC16, Prindle 14 and 16

. While I could get a fair number by claiming the SH adjustment, and omitting mast area from sail area, that would be illegal. SCHRS claims to produce fair handicaps without cheating.

Sorry, I inadvertently omitted VLB when transcribing numbers in my previous post. I measured VLB = 0.560 for the Isotope.

When the F16 class was first created, a number of existing 16 foot catamarans were grandfathered in, including the Isotope and the Hobie 16. Technically, both the Isotope and the Hobie 16 MAY race as F16 class boats. That doesn't mean that they actually are the same speed as a modern F16 design. If it did, then why does the Hobie 16 have a SCRHS rating of 1.193 rather than 1.050?

Does anybody really believe that 45 years of marine engineering, including the advent of computer modeling, CNC manufacturing, and the addition of spinnakers has yielded no difference whatsoever in boatspeed? I don't.

I haven't raced directly against against a Blade, Falcon, Viper, or Nacra F16. They've always been in

A-Fleet

whereas I sailed in

B-Fleet

. The times I have sailed on the same racecourse, the A-Fleet boats were definitely faster. I have raced several times against Hobie 16s (1- and 2-up), Hobie 17s, and Hobie 18s. The Isotope is definitely faster than a Hobie 16, perhaps a little more than the US Portsmouth handicap indicates. Although US Portsmouth rates the Hobie 18 faster than an Isotope, I was often able to beat some H-18s around the course. I'd be willing to race boat-for-boat against a H-18. To claim that a 1-up Isotope is as fast as a 1-up Goodall Viper (which carries a spinnaker larger than the Isotope's main and jib combined) however, is ridiculous.

Eric,

We can move this conversation over to the other thread if you prefer. I will briefly answer some questions here.

1) LTM = is length of the top of the mainsail as you state, so it does factor in and my apologies on misspeaking on that front.

2) I'm not sure the sinking hull correction applies only to H14's and H16's. I would have to dig into that more. Will probably knows the answer off the top of his head.

3) So I used the same VLB. I would have to look at the formulas directly but I don't believe SCHRS distinguishes between short stubby Tornado-like centerboards and narrow, high aspect ratio F18 like daggerboards beyond this number, i.e you could build a boat with very high VLB but super big chord and be slow.

4) I was quoting the Isotope class website, NOT the F16 class website when making that statement. I'm not arguing your point that 45 years of technology hasn't made a significant impact on boat speed, because it has, but the Isotope manufacturer is claiming the boat as a fantastic trainer for the Tornado (same statement made by the F16 class) and they are the ones claiming the boat performs as good or better than an F16!!!!

5) When looking at the SCHRS numbers, one big thing sticks out to me in general, and that is platform and sailing weight matter a healthy amount to the final number. I would weigh your actual platform if at all possible, as I suspect it is heavier than the 113 kg you have quoted (even the Blade F16's aren't really there). That could drive you back to a more 'fair' number.

6) SCHRS may not be creating a perfect number for your boat in a long downwind race, but take a look at the Taipan 4.9 numbers. I'm referencing that as I believe it is pretty similar to the Isotope in many ways (including design age). The big thing is they race without the jib in solo mode. Add the jib in and you drive the number from 1.097 to almost half, or 0.980. That may need some looking into on the SCHRS side as I doubt the boat is actually twice as fast with a jib as without.

Hopefully we can resolve your issue, and I'm okay with it being public because it is important for others to see the process and become familiar with it.

Direct quote from the SCHRS calculator:

Sinking Hull (Only for HC14, HC16, Prindle 15 and 16

.

Please let's distinguish between marketing hyperbole and reality.

Yes, SCHRS places a large performance factor on platform weight. Yes, the Isotope Class Rules specify a minimum weight that is unrealistic. 275lbs would be a more reasonable number, and I understand that most Isotopes weigh at least 280. Rather than trying to get a rating for MY PARTICULAR ISOTOPE, I was trying to get a rating for the class, and SCHRS uses the Class Rules for that. I can contact the manufacturer to try to fix the class rules. A 1.1% change in minimum boat weight yields a 2% change in rating. In racing against other sailors who weigh 25 pounds less than I do, I don't see that large a speed difference on the water.

According to sailboatdata.com, the Tiapan 4.9 was designed in 1982. The Isotope was designed I'm 1962 - hardly the same design age. Please note that the Tiapan 4.9 was also billed as an F16 class boat but it does not carry the F16 rating. The Taipan 4.9 Solo has an SCHRS rating of 1.097. I'd be quite happy with that rating for an Isotope.

That's a point I've made before which has fallen on deaf ears. If I were to take a 40sqft jib off the Isotope altogether, and add a 188sqft spinnaker (the standard F16 size), then the Isotope SCRHS rating would go from 1.050 to 1.108. That's right - add 148sqft of sail area (a 58% increase) and the boat gets 5.5% SLOWER!

Looking at things a different way, if you sail an F16 class boat single-handed with main and jib, rather than main and spinnaker, SCHRS says it will be more than 5% faster. According to SCHRS, jib area is 9 times more important than spinnaker area. That makes no sense whatsoever. If it were true, then nobody would use a spinnaker at all!

You guys are either being idealist, argumentative, or you've never met a casual sailor that does one or two regattas a year on a franken boat. There's nothing wrong with taking what the relative % rating hit in Portsmouth for any of the modifiers and applying it to get some sort of roughly approximated SCHRS number so a casual sailor can pay your regatta entry fee and have a good time with everyone else. While we're taking everything so seriously, we're not noticing how utterly unattractive it is to an outsider.

Eric,

The issue with how jibs are rated is a serious one and has been taken up with the SCHRS international committee, so your concern is not falling on deaf ears. One note on this subject is jib area is working for you upwind and downwind, so it is possibly twice as effective per area unit of spinnaker. That is unlikely really the case but it is a possible explanation as to where the number is coming from.

The weight penalty is a peculiar one, we will dig into that as well. I will say that at the top of the F18 fleet, 25 lbs easily results in the 2% change noted. There is a very detailed paper regarding this that was recently published including the statistics to support this.

Unfortunately at the moment there are a number of different F16 ratings (every manufacturer has one that isn't just the published F16 rating). I'm not quite sure what the solution to this is. If you have measured weights for the Isotope fleet and can generate an average, that would be more than fair I believe for the SCHRS rating.

Jake,

I was trying to be idealistic, because our local fleet did as you are suggesting for 2 years and it doesn't result in a 'fair' rating per SCHRS (see the jib vs. spinnaker area issue above). If your fleet is okay with this, then go for it. I just kindly suggest setting up a fleet SCHRS focal point that can generate ratings for the frankenboats given basic input data for future events. That is what we do locally-I run the ratings as I volunteered, it is fast for me, and my number doesn't change (F18's have been 1.000 for a while now). I will kindly generate numbers for other boats if they can provide the input data, or if I am at an event and not fixing the bottom of my daggerboards, I will help measure. I will see what I can do to become an approved measurer.

Sam,

Once you do become an

approved measurer

let me know what needs to be done as this is something I may want to do...

With that, the calculator and the other instructions that are online will work as much of the data has already been done... that is some one with a Prindle or Dart 18 shows up with a new square top all I need to do is go to the rating table, plug in the known data, then the new data for the sails (CM & CJ) and get a number.... easy peasy lemon squezzy right?????? Wrong!!!!!!!

The problem I had last year was that some sailors were not able to get the required measurements from the sail makers.. Even with my new sails for the P18 from Whilewind, Chip almost choked when I sent him the chart below noting that he didn't have the time to do this.. In the case of the Dart 18 sailor he noted the Glasser was not able to do this asw well... which was suspect to me, but that is another story..

I am going to try and messure my new sails and will send you the messurements to see if they

jive

with mine..

More to come

The computer does not spit out those numbers. Gotta be measured by hand. I am sure they can measure them for the customer. Its just another $75 charge.

That depends on the software Bacho. I don't really see how you can design class legal sails in a software package that doesn't give you sail area. I would bet good money that North, Quantum's and Doyle's in-house software gives you sail area, as does Smart Azure but I could be wrong. All my wing design tools generate area...now, the final product? That could still be different than what you drew for a myriad of reasons that you know waay more about than me.

Why Glaser can't provide this, I don't fully understand. They can measure F18 sails so they definitely can measure other class sails...but they should be providing the area. Its frustrating to me because we are working on a Nacra Inter 20 rules re-write locally that doesn't change the sail area but opens up the builder options, yet Glaser won't tell us the area of the sails they have built for the class (that we would like to make sure fit within the rules).

Ventucky Red, this is a helpful link: http://usf18.com/measurement-tips-and-pics/

I would also download the F18 measurement template. It has all the math built in for the diagram you have.

Mr. Google is not helping me here.... do you have a link or can you send me the spreadsheet?

http://www.f18-international.org/documents/measurement-forms/

The software certainly spits out a SA number, buts its not the same number that you will arrive at measuring by hand as shown above. They can be different for a number of reasons, some of which I do not fully understand yet myself. If they gave you a number from their computer, its not a number likely to be recreated when someone attempts to measure that sail by hand.

Anyways, if you want Glaser or anyone else to fill out that chart, they will need 2 people and half an hour with the sail in their possession to get these numbers. Thats why they charge $75 extra for a

certified

F18 sail. IMO, the certification only says that on X date the sail measured X when measured by approved methods.

There are several different prescribed sail area measurement systems and some classes had their own that varied. Sails can be designed to work within a particular system to have a little more real world sail area and still measure in. The measurements are all just an approximation of area taken at a few reasonably practical points. The sail area generated from the software used to design a sail will be different from a sail that's measured manually...and to measure in to any rule, the sail needs to be measured per the prescribed method. I seem to remember that F18 originally had a slightly simpler, self prescribed, sail measurement procedure and that they adopted the ISAF method when they become a fully fledged ISAF class. Both systems would come up with a different number for any given sail and neither would match the software number. A sail measurer is usually listed/recognized with the class they're measuring for and some classes require some level of sailing organization certification to be a measurer. You may also be recognized by one class and not another. In order for Glaser to measure a class sail, he has to learn the measurement method (assuming SCHRS is different) and actually perform the measurement...if it's not a system that he (or Pease) will use often enough, I can see why he would have chosen to not offer the service.

That said, the Nacra 20 sails? I can probably guess why nobody would want to get involved with those numbers! Political football that probably has a pattern of variation in a distinct path...but I can only guess.

(BTW, Bacho has been designing sails in various software packages from low budget to high end and I've helped produce a few - I was also an F18 sail measurer for a while).

When my in laws redid their kitchen, the counter guys did the measurements by laser.. I wasn't there, but my FIL (who was an Apollo project rocket surgeon for both Rockwell and Grumman) told me it was pretty slick... they had some pretty odd angles along with an island that had an arched side (leech) and the finished product fit like a glove right down to the mm when they installed it...

I am wondering if this technology could work for us?

This is a very interesting thread, and brings out a lot of really great points.

As Jake said, there are different levels of regattas, and managing handicaps should be taken as seriously (or not) as the level of regatta. But, you run the risk of alienating anyone who does take it seriously when you start to bend rules. Finding the right balance, and setting the expectation/tone (communication!!!) is the key.

If we move to a new system, or even just start seeing more handicap racing, it will put more emphasis on getting the ratings right before racing. Unless you have a dedicated volunteer (or team), don't expect much to happen on Saturday morning of a weekend regatta, in terms of settling numbers.

But, we've all been to regattas where someone has clearly been allowed to break a class rule, just to get the regatta numbers up. Whether racing OD or handicap, this is not a problem if handled well (communicate well with the legal boat owners, and don't start letting the whole thing turn into frankenboats over time), and as long as the illegal boats don't win.

Mike

That makes a lot more sense Bacho. Not an easy nut to crack given those limitations.

The reason that sail measurement methods and computer design softwares differ in sail measurement reading is because the software is using advanced math (derivation, etc) and getting a very accurate sail area figure. It is also taking into account the entire surface area that is formed by the 3D shape that you don't get when you lay a sail flat on the ground. Physical sail measurement methods generally use a series of defined triangles to approximate the sail area as well. Also, because sails aren't straight line triangles, but the prescribed measurements are, the result of a physical measurement is only an approximation of sail area - but not the actual sail area. The accuracy of a sail measurement system is correlated to the number of measurement points and since it's impractical to have (for instance) 3,000 measurement points, most systems make a compromise in the number of measured points vs. the accuracy of the result. However, if there isn't enough accuracy with the measurement system, the door opens to sail designs that work around the system and stuff sail area into the sail in ways that the measurement system cannot measure. It's all a balance in practicality, accuracy, and keeping things in check.

Jake,

I got all that. The biggest issue is with classes that don't have or use a prescribed sail area measurement system. I recommended the F18 one because it has a reasonable degree of accuracy, there are step by step instructions and a form that does all the math for you once you've done the measuring. Is it the best system? Probably not. Will it get the job done for SCHRS? Most likely.

I thought F18 had adopted the standard ISAF measurement method when they became a recognized class. I'm pretty sure the A-cat uses that system...would probably need to research a bit. Either way, I agree that the F18 system is pretty thorough with a well thought out form.