Trends in spi design

If I am reading correctly you are saying that the spinnaker luff is longer than the distance from where the head connects to the mast and the end of your pole are. I do not think mine is that way as I like to keep a really tight luff. I think 2.5% longer would make too loose a luff while sailing. I do slack it a bit for light or heavy air. If I read this wrong then forgive my post.

The girth of my spinnaker is not at the minimum 75%. As I recall it is closer to the 80%. I remember, when measuring it, that there was a fair amount given up to that number. The foot of the sails are getting smaller with the trend towards higher aspect chutes. Maybe the higher girth number is to assure that the spinnaker is still large enough, 21 sq meters for the Formula 18s.

Later,
Dan

You got it right.
I was suprised too since in the early time I remember that the trend was to have shorter luff (than the max halyard to end of pole distance) to give crews more

room

to tune the leading edge of asymetrics.
However if you check the Tornado class rule you find that the maximum hoist is set at 8,18 m from mast base and the max allowed luff of the gennaker is 9,15 m.
This let me suppose that the gennaker luff is quite a bit longer than the distance from max halyard to end of pole.
Take a measure on yr boat and let us know.
Perhaps we all will be surprised

The 9.15m luff is shorter than the distance between the end of the bowsprit and the pully at the top of the mast.

The measurement I remember for the Tornado spi setup, is 9100mm from the block at the mast to the bearing surface on the pole. If the spi is buildt to 9150mm, you have 50mm of 'surplus', but I doubt that the sailmakers dont take a small amount of stretch into the equation and buildt the luff a tad shorter (can try measuring the luff on my Gran Segel spi tonight as I already have it in the basement).

BUT, from looking at pictures of current designs in the F-16 and F-18 class, it looks like they are sailing with a luff set up or designed looser than in the Tornado class. 2.5% might be right for those.

Tight mate,.....

We use to hoist the kite on land, grab the luff and give only 1/4 turn with the fist. Now we are running it tighter and looking for next to zero twist.

Steve, I also think a tighter luff is faster. Studying photos of current F-16 and F-18 spis show a somewhat loose luff, much more so than the T. But I think it also depend somewhat on what angles you are going to sail, and how fast. If I was going into the F-18 for competetive sailing, I would buy my spi from Gran Segel in Malmø and set it up with a tight luff.

For the other question Catfan asked. You can not go below 75% and still measure in as a spi under most rules, but going much above 75% give you trouble with the leech and shape at the speeds/angles cats sail. Current trend is higher aspect ratio and more efficient sails with less sailarea and chord.

Guys,

It doesn't help to understand if something's changed in spi design to speak of tight luff or a loose luff.
Please let's stick to the numbers.
Please Rolf take the time to measure the luff of yr Gransegel asymmetric.
Are you sure about the 9,10 mm distance between max hoist and end of pole?
Apparently it seems to me a little too much.
Please follow my argument:
since the max hoist is set at 8,18, we can estimate the distance between max hoist and pole attachment to the main beam at 8,30 m. Now square root of (8,30x8,30+4,00x4,00)= 9,21 m with the pole parallel to the ground.

Please Dan and Tornado Alive do the same (i.e. take the measurements) on yr F18s.
The distance between max hoist and pole attachment in F18 catamarans is very close the Tornado's (as per the F18 class rule max hoist is set at 8,15 m), however the pole lenght should be a little less.
From the examination of the pics F18 spi apparently have a shorter luff but I would not trust much into pics.
Please check also the girth of yr F18 spis.
Thanks

P.S.
Incidentally are you aware of Gransegel spis on the boats of WORLD CLASS F18 crews?

Sorry mate, boat is de-rigged and de-beamed ready for the trip up to the Worlds. As of this weekend, you wont here from me for the rest of the month. <img src=

alt=

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Whilst there are none better as far as Tornado kites, from what I have heard, they have not got the shape right for the F18s as yet. Anyone out there running Gran Segel F18 Kites ?????

As for luff tension, like I said I run mine tight. Minimal twist if you grab the full with your hand..... Under load though it will not look quiet so tight as you have a bit of flex from the pole, stretch from the sail cloth and halyards.

Steve, have a good time at the worlds! I'll be rooting for you and Macca on the Blade! Wish I had the money to go down there with the family for a break in our abysmal winter.

The Gran Segel guys in Malmø are really poor at marketing their products. As far as I know, the only good reference they have on F-18 spis is a victory in the Archipelago race with Will Sunnucks at the helm.

I'll try to measure my Gran MK-4 tonight.. It's something I should have done a long time ago. The 910cm was the current setting in 2004 amongst the pros. With this setting, you could twist the luff about 45deg with your fist before it was tight. We used 910cm, but tightened the luff line to move draft a bit forward. We could not twist the luff much at all, and that was fast downwind if you could 'wild thing'.

Take a look at these pics, from Mike Dobbs (username Tornado here) photoarchive. These are from the Miami OCR and T NA's, and demonstrate quite clearly how thight the luff is set on the Tornado these days.

http://i5.pbase.com/o6/30/7530/1/73986543.uVpshoTo.IMG_3883.jpg
http://i5.pbase.com/o6/30/7530/1/73986546.GbLur4SS.IMG_3887.jpg

I beg all the ownwers of Tornado and F18 cats who usually make posting on this Forum to provide us with their measurements
Thanks

I'm 5'8

tall, have a 33

waist, and weigh about 175lbs.

I am 6' with a waist of 34" and weigh 175 lbs.

8"

Just measured the luff of my old (like 2004) Gran Segel spi. Did it twice with a 1 meter long stick, so there is a margin of error there, but not significantly large. Luff was measured to be 897 and 900cm long. I also re-checked my source for distance from block to block, and it's 910cm with 1-2cm slack when fully hoisted.
Hmm, something smells fishy here. I'll try to get a longer measuring tape and measure it again with some tension in the luff.

Thanks Rolf.
However it would be interesting to have other Tornado's and some F18's data (for sure the F18 class is the other most developed catamaran class with regard to spi design).
Therefore I invite all of you to post the requested measures (luff of their spis, max halyard to end of pole distance, mid girth to foot).
Two of them can be found easily in yr measurement certificate.
The data provided by Jake, Dlennard and pitchpoledave are interesting only for a certain kind of guys.

Just checked my latest measurment certificate.

Kite luff = 8.665 meters

Thanks Tornado Alive
In order to estimate the max halyard to end of pole for the Capricorn, do you know the lenght of yr pole?