Just wondering about F16 performance against the A’s solo but with jib and no kite?

Also why don’t they run jibs on the A cat? Thanks.. <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" />

Good help us all if the A's go to Spinnakers, wonder how their rating goes with a Spinnaker, lead weights attached to rating I assume!

http://www.webbo.dyndns.org/~sailing/spi/index.html

The A cats dont use jibs becouse the sailarea is used more efficiently in a taller main with higher aspect ratio = better performance upwind. Put in a reaching leg, and the jib will be good to have.

I guess a much lighter A-cat with larger sailarea and 2 feet longer hulls will leave an F-16 without kite behind at the top mark. But the F-16s are allowed to use a kite, so.. <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

There is a guy racing a Marstrom A cat with spinn. (exactly like the one in that picture) here in Florida, he only uses it for distance racing and he kicks butt. I wonder how it would do around the cans? There was some talk on the A cat web board about adding spins but most of them don't want the added cost and complexity, as well as the extra set up time.

Actually that article you link to says it really well.

... Here's the sad thing about adding a spi, you will LOSE speed upwind. ...

... Downwind ... Here's the great thing, you gain loads of speed now ...


He even gives a full scientific analysis using GPS track data, I quote :

"... In winds around 18 knots you are trapezing flat out using chickenline as far back as the hull streches, the speed is 18-19 knots and you sail 30° from a direct downwind course. The VMG (velocity straight downwind in this case) is around 15 knots! Compared this to wild thing without spi where you sail 45° from straight downwind course and have a VMG of 11 knots. This is 30% faster and a lot of more fun.

All this is based on actual sailing trips using gps track plots. The VMG speed I'm talking about is not peak speed, it is an average speed base on 1-2 Nm of sailed distance. The highest speeds I've seen so far is 19 knots based on 10 second average."


Adding spinnaker to these boats and the F16's is one of the most significant developments done this decade.

Wouter

Has there been done any research on why you go slower upwind with the spi gear on? The Tornado class noted the same thing when testing different configurations. The classic rig was a witch to beat upwind..

The spi gear adds weight, but is it really that significant? I dont think so. It must be the extra windage that really hurts upwind performance? Have anybody looked seriously on least windage solutions like airfoils shaped solid snuffers and telescoping bowsprits (not KISS, but faster perhaps).

Extra weight and drag of kite / pole annd wires, but also, I'd guess a fair amount is the Spi haylard messing the airflow over the mainsail.

I think Hakan said he looses about 2.5% upwind to other Marstrom A's

The correct answer to that question goes as follows :

When the total amount of sailarea is limited to a relatively small amount then it is most efficient to put it all in a mainsail of sufficiently high aspect ratio.

When the area in the mainsail is limited by itself (for some reason) but a higher total area is allowed then a mainsail + jib combo is quicker overall and often also upwind when the jib area is at least 20 % of the total. You point lower but go disproportionally faster.

When spinnakers come into play then having a jib is less advantagious then before as the true power of the jib lays on the reaching legs and downwind legs. Of course the spi will then take care of the downwind part leaving only the reaching parts and some additional performance on the upwind.

There are a few reports of spinnaker boats of identical make racing eachother where one is sloop rig and the other only has a main sail and still the sloop rig has better upwind performance although relatively minor.

So the whole point comes down whether you can add a jib to the orginal sized mainsail (=faster) or whether you have to take the jib area out of the mainsail (=slower).

The A-cat class rules are of the latter type and therefor you will not see any jibs on A-cats anymore. However, the F16 rules are of the first type and here the added performance of the jib is used to ofset the performance hit experienced by having another person on board. Overall it appears the F16's are pretty equal around the course when comparing both modes (1-up uni and 2-up sloop) with the sloops being slightly faster upwind and the uni's being faster downwind.

Wouter

Well then under Texel the A-cat will be rated faster then the F16 1-up again !

Currently the F16 is rated as the second faster singlehander available with only the M18 ahead of it. A-cats are rated 1 point slower.

Wouter

I had some quality computer time today, and read up on some interesting C-class litterature.

One was an article saying that upwind about 36% of total drag came from the platform moving trough the wind. One of the worst structures with regards to drag is circular tubes, so perhaps the spi halyard and extra rigging really are responsible for 2.5% performance loss to windward. Perhaps it's time to streamline those bowsprit stays and route the spi halyard down the forestay (or inside the mast)

Except for the A2 A-class, most hull designs look like they have not considered drag as they pass trough the air. The same for crossbeams (except those boats using wing-mast sections as beams). While I am thinking along these lines, I think I need to work on my own body so I can get a better aerodynamically shape to my "behind" <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

Rolf can you send me those articles ? I would really like to read them for the new info they may contain.


Send them to wouterhijink(at)hotmail.com

Thanks,

Wouter

The extra drag of the spinnaker snuffer system is what led Nacra to move the whole thing to the mid pole setup, as the Blade has. The original I20's all had the big hoop at the end of the pole and the entire spinnaker was hanging under the pole, if there were any waves the entire mess was soaking up water upwind, gaining weight of course. So they went to the mid pole system. For a long distance race, they used a skinny pole and tramp launched the spinnakers so there would be as little drag out there as possible. Marstrom went to the Snail snuffer system, to get the entire spinnaker out of the wind and water.

On the Uni vs. sloop thing. Back when a bunch of us in Florida all had Nacra 5.5's, there were several of both Uni and Sloops racing. The guys saling the Uni (solo, no jib) would usually beat the sloops to the windward mark, especially in light air. They could point higer and without the extra weight of the jib/bridal foil/crew, were lighter and beat us downwind too. Of course one of those guys was a several time National 5.5 Uni National Champion, he is now racing a Nacra A2. I asked him about adding a spinnaker, he said, "Why? It's fast enough the way it is and I don't want to spend an extra 30 minutes setting it up and taking it down."

It was then I started thinking that the small extra sail area of adding the jib, (54 feet?) did not add enough power to compensate for the extra weight of the crew. The only time the sloops would go faster than the Uni's was when it was really blowing and the Uni's were overpowered but the sloops weren't.

But when you add the coplexity of the spinnaker, the crew becomes vital for a good set, douse and of course trimming the spinnaker downwind. I would expect the sloop crews to be faster upwind in a blow as well, as long as the crew isn't too heavy for the wind strength. In light to medium wind, the F16 solo with spin. should be faster than the sloop, as long as the skipper can set and douse the spinnaker without giving up too much speed while doing it.

On the drag thing, you will notice that all the Olympic Tornado racing crews wear the streamlined pull-overs over their life jackets/trap harneses, just to reduce the drag of clothes flapping in the wind. <img src="http://www.catsailor.com/forums/images/graemlins/shocked.gif" alt="" />

Those 'streamliners' the crews wear are to minimize the risk of snagging a line on the PDF/trapeeze gear. I dont think there is much you can do about parasitic drag from the crew. Unless somebody really can make my day and prove that a pear shaped body is ideal for catamaran crews <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

Wouter, I read a lot of articles/webpages the other day. I think those numbers for platform drag was from a web forum. I'll see if I can find the link again.

While Marstrom has a snail on his unirig designs, he has a brand new hard integrated snuffer/pole design for the Tornado this year. The design looks remarkably similar to what Lovell & Ogletree had on their boat, and has 4 advantages over other designs that I can see:

• It keeps the water out.
• It is more streamlined.
• It acts somewhat as a jib endplate.
• It is stiffer, for less dynamic losses in puffs.

I guess you can't really put a snail on a boat with a jib.

Obviously he didn't race in open class fleet with spinnaker boats. That spinnaker sure it faster around the course, no doubt about it.

30 minutes setting it (spi) up and taking it down ? Nonsense, you just have to work out the right sequence. You really don't need more then 5 minutes either way and then I do it all singlehanded. I can do it faster if I want. Some are even leaving the spi inside the sock and remove it together with the pole before trailering. Leaving the retrieval line attached. When building up the boat they fit the pole with 4 quick knots and then flip the boat to run the retrieval line/halyard up the mast and they are ready to go.

But I found that alot of people are just plain stubborn and stick to their old slow routines. But there is absolutely no need for that.

Wouter

I have yet to see a hard snuffer tube that works as intended and their have been enough people trying.


how about the advantages

-1- It keeps the water out.

Not a problem with a decent soft snuffer. Just have the sock made of lightweight sail laminate like pentex or mylar.



-2- It is more streamlined.

Hard snuffers tend to be larger in diameter as the head of the spi can get jammed and while the soft snuffer can locally expand the hard snuffer can't.



-3- It acts somewhat as a jib endplate.

Right ! Having the jib foot angle down toward the mast takes care of any issues here.



-4- It is stiffer, for less dynamic losses in puffs.


Not a problem with the soft snuffer as the snuffers don't do diddly in the way of pole stiffness and sorts.


There are a few simple reasons why the soft snuffer remain so popular.

They don't break (hard ones do !)

They don't have sharp edges when they break (glass and carbon hard snuffers have)

They are cheap

They allow the snuffer to set itself to the bundled up spi that is pulled in allowing easier doucing

They are lighter in weight

They don't seem to suffer from any performance hit that isn't also linked to hard snuffers.

They are alot easier when trailering the boat.


I dare say that marstroms new snuffer will not be any different from the hard snuffer that came and went before

Wouter

..

The results are at www.catamaranracing.org/results/commodores_06.htm - There's no internal link yet, we're a little behind on updates ...

Just to keep everybody informed, here are the results ordered to elapsed time.

Lets chalk this one up as another example of where the F16's hang with the A's around the course.

Doc (Eric) and Paul are doing very good stuff over there in California !





Wouter

I dont think this paragraph is fair nor reasonable.
Wouter you were instrumental in limiting or banning all these in the F16.. The exception is the weight clause.

Sounds like your initiatives are the ones you are upset about..
S...