After playing around with my spinnaker pole and the mast on the water [eg the tension on the wires /bending of pole and mast] I was wondering two things that I believe/hope you all can help me with:

Q1: why is the spi- pole fixed to the center line of the boat and can not move to wind/lee ward side. would it not give you far more "reach" if pole is to move windward?

Q2: why is the mast for/aft position fixed and cannot be changed while sailing- is there no benefit?

pls help me out.. [before I start making devices that will allow me to do these things]

Q1 : Having the spinnaker on the lee side of the boat (relative to centreline) really cuts down on the leehelm that you get. Placing it more to windward (relative to the centreline) will therefor increase leehelm. In short, you may well upset the balancing act in forces on the rudders.

Additionally the flow on the luff side of the spi needs to clear the jib/mast/mainsail. By placing the spi more to windward you are closing off this slot. We all know that a jib that is too small will backwind the mainsail and make the baot feel bound up and slow.

Also it is too cumbersome and costly for too little gain.

Q2 : Benefits are to small on a bouy race course and the adding of a spinnaker negates much of the need to rake your mast forward or straight up for optimal performance. In short to cumbersome and costly for too little gain.


There is one golden rule on spinnaker boats : Simpler is faster !

On spi boats systems must be simple and work very well otherwise the gains are fully negated and you are better off without them.

System to gybe the spi pole and rerake the mast while sailing do not satisfy these criteria.

Greg goodall ones told me that during training for the F18 worlds in 2004 they found that each second of delay in setting and powering up the kite they would lose 10 mtr distance relative to the other boats. How many seconds do you need to rerake the mast and gybe the pole to windward at each gybe ? Do you think that the extra boatspeed is large enough to overcome these initial losses of about 100 to 200 meters ?

Wouter

Wouter,

thanks for the explanation, so if i understand correct....

Moving the pole windward in combination with a different cut for the spi and/or jib might be worth it. [but mainly on long distance- if seconds are lost] If the system would work without extra seconds los it will be worth on bouy racing as well.... correct?

Mast - don't mess with it; basicly

I don't know really, putting the spi pole on the centerline has noticeable slot size (between its luff and the mast/jib luff) advantages. You don't want this to be closed off to much.

I personally don't really see the advantages of putting the spi to luff, What do you think are the benefits ?

Wouter

Moving the asym spin tack to windward is a trick done on bigger multis (F-boats) for lighter air and heavier air, where driving the hot angles to make the spin work doesn't always pay off. Moving the tack to windward makes the sail work a little more like a symetrical, allowing you to drive deep. Something some of the f boats seem to have figured out when sailing in those conditions against monos with symmetrical chutes. While they're sailing hotter angles faster, the monos are killing them by driving deep. Would this pay off on smaller lighter boats? Maybe not so much in heavy air, but in light stuff it just might. The thing would be to drive deep with things bagged out.

Being able to move the asym tack to the lee would definitely help in trying to carry the spin at higher angles than normal.

For a bouys course this would definitely be more hassle than it's worth, especially one design. But, on a distance race...

What boat are you sailing?

Tiger Mike

Thank You for attempting to think "Outside the Box" allthough I hate the term as it is usually applied, sometimes it makes sense. Just because It hasn't been done doesn't mean it can't be done. It might not make a big difference, but winning by a tenth of a sec. is still a win. Every little bit helps, potentially!!!! If the downside doesn't override the upside.

It HAS been done before, and shown to not be effective for bouy racing.

I'm sailing a Nacra F18 . Since Round Texel I'm wondering about this, first +/- 15- 20 km were Spi-able. we needed to tack right above the island because we could not go deep enough [to the wind that is]. I was thinking about using two "spreaders" horizontal be to move the spi pole

Stilleto 27's use a cable between the bridle mounts on the hulls to move the kite windward and leeward to great effect. I have seen an articulating spinnaker pole on a gulfstream 35 also used to great effect. We were able to carry the kite about 10 deg higer and also able to run off significantly more. On small cats though, I doubt they would be helpful. The apparent wind should never get close to aft of the beam.

If we follow the "...its been done before..." we all need to pack up and go home.
I think the spin to windward is an area worth visiting again. As boats get lighter and faster, and Spreachers get flatter, the ability for the Main to greatly enhance the Spin gets possible, and the geometry of moving the tack to good effect becomes viable.
Attaboy from me, for what it is worth.
By the way, while blade jibs acting as aircraft type "slats" have been around, has anyone seen a "slat" or blade jib in front of a spin? Seems like that is where it belongs to keep the lee side air stuck to a spin. (Yes, Wouter, that is theoreticaly not how a slat works (high velocity air sticking), but it does work...)

Good point, while I personally don't see an advantage worth persue right away I'm all for some real life testing. But not on my boat as I have a jib and strut that go all the way down to the spi pole. So who else is going to take this up.

Wouter

When I was thinking early on about fitting a kite to the cat I wondered why a catamaran would need a spi pole at all particularly my 430 given that the mast at 50% of hull length. This puts a sail rigged at the bows a generous distance in front of the mast. I wondered if I set the sail from a guy rigged between the hulls, I would have a spi of sufficient and usable dimensions. The other thought I had was, if rigged this way, it would be possible to have the tack adjustable athwartships which I thought may be of some advantage. I reasonably thought [in my mind] that the further to windward the luff was set, within reason, the better the boat would point. I'm not exactly sure why I felt this would be the case, but I did. Logos?

Well it remains a thought as I went the traditional way.

I think it'd be worth trying but I ain't gunna do it cause I've just about had enough of spi development for the moment.

Kenneth,
Moving the spi pole to windward:- I tried this around 10 years ago. At the time it seemed to give me the same speed with a lower angle.
However, the current spinnaker shapes have you going so fast that you are just wasting time adjusting things like this.

The sooner you can get motoring with the kite up the better.

Maybe it could provide a benefit in distance racing.

I wouldn't bother with it around the bouys.

Regards,
Phill