kite luff length

[chrislewns]

I wondered what the kite luff length is in relation to the distance between the top of the mast and the tip of the pole for other boats as my kite hoists quite tight on the luff.

[Graham Bridle]

These are measurements taken from my Hyde kite....

Luff length = 7.96m
Leach length = 6.27m
Foot length = 3.67m
Mid girth = 3.36m


mast rake must play a pretty big part in the luff tightness, and AD certainly has plenty of that !

[roland_trim]

The Fyfe cut is fairly flat. Using a kite very similar to Aunti's Fyfe we found the tighter we made it the deeper we could get the boat to head on the apparent wind (on BS both and the E5 when upright). Have not found a "too tight" setting yet, but there gets a point where it becomes crew and our mast head limited (mast is floppy).

The RS 800 kite seemed happiest with about a handfull of slack when set, but is  a much fuller shape and has bigger "shoulders".

[neal_gibson]

Usual thinking for luff length is distance from kite halyard block to pole tip then plus 10% for luff length of kite. is a good starting point  setting rake and caps tension before you measure is always a good idea.

[chrislewns]

That sounds like a good start Neal.  Currently my luff length is shorter by 400mm which makes it all look very flat.

[Will_Lee]

We started at 8% extra but every time we made it less the boat seemed to go better. We stopped at about 2%.

We did this by pushing out the pole, so the extra speed may have been to do with all the other things that changed as well: space between kite and main , kite sheeting angle etc etc

[chrislewns]

thats interesting because I have had a look at the pole and there is indeed quite a lot more that it can extend.  I spoke to the sailmakers at Norths and they maintain the pole needs to be as long as poss to get the most area out the front and away fron the other sails.  Incidently what is the limit for pole length?

[Stuberry]

There is no limit to the length of spinnaker poles, but they have to be able to be retracted to within 4300mm of the transom.

[Will_Lee]

Hi Chris,

When we raked the mast more we pulled the pole back in to keep the luff length the same. Could have put a strop at the top of the kite of course.

[chrislewns]

I remember that you said you had done this.  I think it is best to keep the head as close to the top of the mast as poss if not on it, the same goes for the tack on the pole as you then get a stable kite to fly.
The extra luff length does let you get more area when measured and I gather that it is  a bit of a struggle to get the 21sq m that is the max allowed.
I do know that other asy classes have gone flatter over time due to heating things up with the apparent wind angles so as is often the case in life a compromise must be sought!

[roland_trim]

it is  a bit of a struggle to get the 21sq m that is the max allowed.

The main struggle is getting exactly 21 sqm and a shape you like,

The second kite we made came out at 23sqm for and was then trimmed down. There has also been a fair variation in kites for SMODs when laid over each other. Welcome to the precise science of sails...