Sloop v uni

Were you Uni or two up? The jib gives the back side of the main a 'turbo boost' vs. sailing Uni, which is supposed to be offset by having less weight (no crew) on the Uni.

I've found in very light air, I'd rather have that turbo boost (with a very light crew, say, 100 lbs.) than go Uni. But in 10knots, a Uni should be able to keep up with the sloops, going upwind.

Uni.

Racing against Terry & Kris, I stayed with them in the 1st race (light air) but in the 2nd the wind picked up to 10-11.

My thinking is that the A class has done an awful lot of experimenting with mast/sail comibnations. Not so much experimenting with the F16 uni.

Did you happen to notice Kris picked up three 3rds at GYC? What, she's been driving a year now?

I guess it is -as you said- just you. It is because you said that with more wind the sloops are faster than you.
As Timbo said you need the

turbo

jib in light winds, once you are fully powered (e.g. trapezing) you should be equal or better as uni in upwind conditions . Well, in theory. An uni is more difficult to sail. If you bear away too much the flow around the first sail stalls and you have in case of an uni no power (first sail = main) and in case of a sloop just a bit less power (just the jib(=first sail) stalls, but not the main).
The good news is that you don't need to buy new sail(s) but just a few tell tales and sail more often to learn not stalling the sail.

Cheers,

Klaus

I'm confused Klaus. Let me state it differently.

I sail uni (mostly). After about 10 knots of wind the sloops are able to sail better upwind. Is any one else experiencing this? If so what are you doing to minimize it?

Stretch out, lower down, and get out on your toes while trapezeing. Leverage, downhaul, sheeting and steering with wind/waves does the rest. That is, unless the game have changed while I have been in my workshop.

The uni F16 is as fast or faster than the sloops upwind in medium breeze. So with 10knots you should have no trouble living with the sloops.
The Achilles heel for the uni F16 is boat handling in anything above 15knots. However upwind in this level of wind the two modes are still fairly even.

That sort of fits in with what I've always believed. I'd read years ago that physics favors the uni or

cat rigged

boat upwind because the jib tends to bring the bows down.

As soon as a sloop pulls 2 strings, a cat will not keep up. That has been my experience in f16s and Taipans. 2 on the wire and they truck upwind.

Is there a physical law describing this situation? Something designers hang their hats on?

What about the A class? Does anything go to weather better? Oh, and the C class comes to mind.

I'm pretty sure that things have moved on somewhat more than the Stealth rig and that the latest Viper and Falcon rig is certainly better than even a view years ago right across all wind spectrums. Certain top Viper sailors are quoting that they can fly a hull in anything over 6 -7 knots dual, which if you then use the extra righting moment, means the uni can no longer really compete at any level with the sloop, either upwind or down, light wind or strong.

In saying that having now sailed an A for a season, I would say that the A rigs are certainly more suited for the singlehanded F16, there certainly is a quantum leap between the Stealth rig ( set up as a sloop sail with more powerful bottom section maximising the jib, minus jib )and the A rig I have ( much more even spread of power over the sail )

As an experiment I'm just about to put the A rig on my F16 to fully understand the differences. If the A rig is so much better then could we allow the A rig into our rules for solos, there are plenty of stiffer older masts and good quality well researched and tested sails about at good prices now that the fashion for bendy fore and aft masts are all the fashion in the A's.

The alternative is, as we often discussed before, allowing the Uni to sail with a blade jib.

Any science to go with all this? My own observation says an A class will beat any F16/18 to the weather mark given equal sailors.

I'm not sure the A class is the king as much as people say any more, certainly from the handicap racing I did last year I would say that the A , F16 and F18 are all pretty equal. The F boats certainly have had a lot of sail and rig development these last few years whilst that gain was some years ago with the A's. One only has to look at the way the F18's handicap is dropping to see that this is backed up with results ( even Macca was whinging about this recently in one of his posts ).

<img src="<>/laugh.gif" alt="laugh" title="laugh" height="15" width="15" /> We have some A class sailors you'd have to see to believe!

I see the top of the F16 fleet competitive with the top of the F18 fleet but don't get to see them start with the A class enough to make a judgement.

Ok...wait a minute, the A Cats are 70lbs. (160) lighter than the F16's (230) and they have a taller mast, so of course they are going to go upwind better.

I pass them all going downwind however!

As far as putting the A Rig onto the F16, that would be very interesting to see. What is their total mainsail area vs. ours?

And adding the jib to the F16, sailed solo, is a lot of fun in light/medium air. That's how I sail it at home, not at a regatta of course. But not sure how it would be with more sail area up high, as with the A cat main. In light air it would be great, but how about in a good blow?

Oh, and are you going to run your spinny off that A cat mast? I think if you keep the mainsheet tight, it might survive...or not!

And thats exactly why we all think the A is just so good, the standard of sailor across the A class is top drawer, unlike most other classes.

The F18's with the demise of the Olympic status of the Tornado, has suddenly become the pinnacle of crewed boats and with the increased R & D by the manufacturers due to more competition within the class, has made significant leaps ahead both in design and crew competance.

But they are very different boats attracting very different sailors, one has finesse and efficiency like a F1 the other brute horsepower like a hotrod.

My betting with world class sailors on both, they both would be pretty equal at the first mark.My betting that with future development such as the new generation of boards, and a weight loss diet ( which the F18's are going to be forced into by the new F17 unless they want to see crews moving over class ) will see the F18 ahead in a relatively short time.

<img src="<>/cry.gif" alt="cry" title="cry" height="15" width="15" /> WAIT A MINUTE! THIS IS MY THREAD!

Tim you don't pass them ALL going down wind!

And how about all the work the A class has done on masts and sails? How can the rig we use, F16s, work equally well for sloop and uni? If nothing else there is a weight difference.

Without changing any rules, I'm guessing there is a better mast/sail combination for uni sailors.

Weight is not everything and as hull dynamics in the water are improved, the heavier boat with much larger sail areas, can defy the predicted drag in the water. The SCHRS revision this year has begun to take this into consideration and has revised the way light boats are penalised.

I've already run the A rig on Bitsa albiet with a different sail and it was a much nicer boat to sail. There's not much differnce in sail area 13.95 v 15 sqm

Theres not much difference in mast height 8.5m v 9.3 m and the F16 platform is wider and hulls heavier, so probably pretty even from a Uni point. The jibs power is much lower down and has less efect on RM but and the big but, gives much more drive over the lower part of the main.

Mmmm you might be right there but the early masts such as mine were much stiffer than the latest. If you find me crying over a broken mast then you can say

told yah so

<img src="<>/smile.gif" alt="smile" title="smile" height="15" width="15" />

There have been some guys who did put spinnys on their A cats, not sure if they put a stiffer/stronger mast on first, I doubt it, and their spinnys were probably smaller than the 17sq.mtr on the F16.

Dont't forget the A cats hulls, in addition to being lighter, are two feet longer, (that's 12.5% longer) and I think that makes a speed difference as well as the taller/larger main, going upwind.

If you want to spend the time and money to do the reserach, design, and experiment with it, I'm sure you could find the

Perfect Combination

for a mast/sail combo. But who has that time and money?

Only the A cat guys!

I know. I would like to understand the physics a little better. Maybe a designer will come along that can shed some light on the subject.

FWIW.... I just finished my first regatta in CRAM. I have never raced against any A cats before and I was surprised I was able, to a large extent, keep up and point with them upwind. I was not able to get them all downwind. I got a decent number of them. The A cat sailors in this bunch are no slouches. I used to think that 2up was the only way to go, but I am not sure anymore. I like sailing solo better anyway.
Btw, CRAM is a great bunch of guys. I look forward to sailing with them this summer.

Hope you can make it to Racine in August. We have 6+ F16s and growing in CRAW. A bunch of us will likely also make it to Captain Jack's in Muskegon.

I'll probably be at Caseville, Muskegon, and possibly another one.

Not sure I will be able to make it over to that side. already pushing my luck with the wifey. I am doing Bay City June 2,3 and NCYC 23,24. Caseville on July 21, 22 is a possibility

An A Class is a lot quicker than an F16 or F18 upwind. They sail about the same speed as a T with more height. The A does have the extra waterline length and the design is all about low weight, low drag and low displacement. Everything from the rig to the hulls are optimised for this. Don’t forget that most F16 uni's are a compromise between sloop and uni hull design. 2 feet shorter, 32 kg heavier and a shorter rig.

As for downwind, the new A's are now keeping up and even beating F18s downwind. It is not just the curved boards, but the stiff hulls, flexible (fore and aft) masts and incredibly powerful mains that are allowing these boats to trap downwind. Whilst you are setting your kite, they are shooting of in the sunset trapping downwind, not that you will be anywhere near them when they turn around the top mark.

p
The physics are simple to explain, but opinions are all over the place. It all comes down to what you believe the most.

Theoretically, a sloop boat is faster then a uni allround, that is when considering everything else equal. However, most boat also differ from eachother in several important aspects and that makes comparisons problematic.

Physics,

A sloop rig can always fly MORE sailarea then a uni-rig. On anything but an upwind leg where angle of attack is important the boat with more sail area wins (assuming equal aspect ratio's, luff length and tipheight). Fitting a spinnaker to boat versions reduces this performance gap. Making the sloop boat clearly favoured on a reach and leaving the conclusion still open on the upwind. Downwind is pretty equal now.

On the upwind leg the balans may turn either way or hang flat depending on the details of the design. Sloops point lower but get more drive low in the rig and are easier to not stall, an inexperienced crew can get more performance out of a sloop then a uni. More drive means more speed and if that speed compensates for the lower sailing angle then both boats have equal vmg which is what makes you reach topmark first. F16's are counting on that particular aspect to a large extent. However it does assume that both rigs have rerceived sufficient or equal amount of development. It is probable that sloops have reached alot more development over the years them uni and lots of sailors are soloing their sloop rigs which is some drawback on performance.

The jib is not a hinderance on the upwind leg as many will claim. It does smooth out the flow over the main and will have it producing drive more consistantly , especially when the rig is moving about in waves or when the wind fluctuates. Also, the jib can operate well as surprising low angles of attack because of the interaction with the main. In affect the jib is in the updraft zone of the mainsail and does not nearly need as much AoA as a single sail does. the hit on pointing ability is therefore rather limited. A unirig needs an apparant windangle of about 20+ degrees where a sloop rig needs about 26+ degrees. Assuming as sloop sails at 45 degrees to the wind and a uni at 39 degrees then the uni rig gets 10% more saildrive. 20% additional sailarea will speed the sloop up sufficiently to equalize vmg , 15 sq.mtr times 20% = 3 sq.mtr where the F16 jib is 3.7 sq.mtr.

Do you understand the balancing act now ?

Ofc ourse other smaller factors are also at play like righting moment etc but I leave these out of the discussion for now.

Righting moment is however important and that is in my opinion the largest factor in creating difference performance between sloop and uni f16's (text above refers only to sloop en uni boats in general with all else equal).

Basically I banked on the uni being faster downwind then the sloops here becaus of lightweight and ability to fly sooner and sail deeper. With an optimized uni sail the loss on the upwind will be limited and subtracting these from one another will go a long way to equalize both F16's but of course never fully. In sub trapeze conditions I expect the uni to be slightly faster and in big wind to be slightly slower, in the medium stuff it is a fine balancingact.

That is the theory and consult Marchaj, Bethwaite, Ganty and other books for the details.

First point of call for any solo sailor is however to buy a dedicated uni sail for his F16 if he wants to race often that way. It needs to be latter all over and fuller in the part where he jib flies. It may also have a leech that opens more easily to spill air (at a lower righting moment level). All things a sloop main will not have. This alone will go a significant way in getting max F16 solo performance. The rest is learning how to sail it properly since their is no jib to help you trim the main or point.

Agreed but that has taken nearly 30 years of development. There is now quite some development going on with the F16's, we are starting to opitimise the boats for weight and drag. With an extra 1M in the main and 3.7 in th jib and only 1 1/2 ft shorter we should be fairly equal if not ahead as the hull drag is optimised better. The learning curve of the A will benefit us greatly and will shorten ours.

Yes off into the sunset for the first 75 metres and then the F18's and F16's are up and running faster and lower, it doesn't take long before you can reel the A's in. On short course racing its normally pretty even by the time you get back to the start. At a recent handicap race where the A's were starting, it was noticed a ShadowX with the new large kite ( virtually a F16 ) could reel in the No 2 in the European A Class downwind enough to handicap out as winning the race. That Shadow sailor is a very good sailor but is he comparible in skill ?

The other thing to contend is that very few people can trapeze downwind consistantly sucessfully on an A, you only have to look at race reports where the worlds best all have spills of some kind, sometime in an event. On an F boat most people can trapeze downwind under spinny, it is a far far easier skill to learn for some reason.

Not dissing the A's, they are a wonderful boat, very refined and lovely to sail, but I think they may well be knocked off the top perch fairly soon, by any of the F16, F17 and F18's once developed a little more, being more than an equal match.

Thanks Wouter.

I've been wondering how 'fast' it would be, if you took the current 'hot' A Cat hulls, chopped a little off the front and back, chop a little off the mast, add a spinnaker and maybe some 'corrector weights' to get it up to F16 min wt. specs, then raced it Uni, ie. zero jib hardware.

I think it would be an interesting experiment...but expensive, more so, if it didn't work out to be at least as fast as one of the 'Stock" F16's.