Spinnakers seem to be a bit a black art to get the best out of them, my question is has anyone come across a good tuning guide that descibes what is the best shape etc. <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

Good one. I think you should contact your local sail maker and make sure to ask for the performance guarantee <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

Wayne,

What kite are you currently using?

It depends on the cut of the kite.

By this I mean the following

1, how much depth does the kite have and can this be manipulated using halyard tension. Generally deeper kites can be flattened by letting off some halyard, but luff projction plays a part
2, how much luff projection does the kite have; the only way to show how luff projection effects the trim is to put the kite up on the beach and play with sheet and halyaard tensions and watch that happens to the kite, it's shape, AND where it sets
3, how much leach curve is there.
4, How much return there is in the leach
5, how much twist there is in the kite


and also the weight of the boat being driven and if you trapeze down wind

Generally flat kites (such as the current Piggot kite which we worked on) gives more speed, but is harder to trim, so it can feel "difficult" but you are getting plenty out of it; BUT you have to keep the air flowing and so drive it hard.


Come to Rutland this weekend and we can have a chat over a drink or 11.... <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

I get conflicting messages about how tight the luff tension should be. In the end I go with what the sailmaker says (figure of all the opinions, that should be the one you pay attention too). The sheeting angle should point to a point on the luff about 1/3 up from the tack (once again, sailmaker told me this and may or may not be unique to my spin cut). Some people don't like telltales on their spins, but I do. Trim the spin so it is on the verge of collapsing and/or the leeward tale is flying. The only way to get speed out of a spin is to be really agressive at trimming or driving. If you have the opportunity to have someone crew for you who really pays attention to the constant trimming of the spin (or concentrate on it yourself) then you will fly. Compare that speed and feeling to when sailing with less attention to the trimming.
I get much more confused these days about how the main is supposed to look downwind. <img src="http://www.catsailor.com/forums/images/graemlins/confused.gif" alt="" />

As per all sail makers, they all offer a "first mark " guarentee which I would guess once you reach the first mark ( upwind of course ) the guarentee runs out.

More seriously if you trawl the internet there are plenty of main tuning guides written by some pretty good sailors, haven't yet found a similar assymetric spinnaker guide. <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" />

Scooby, the spinnaker is a GP same as your one.

As a newbe and non-techy, I sail mostly by feel. We have found that in lighter air we let the halyard down about a foot and pull it tighter in heavy air. I hear that you don't want a pretty spin..like it is going to colapse but that has never really worked for me. I asked one of the top sailors in our area and he said to fly the tell tales. It has been great adivise and works well. I fly them right on the edge...loser not tighter. PTP is right..having a crew to constantly work the spin is the best. I saw the spin and work the jib along with it for the most speed. As for the driving angles and that I have no idea because I don't drive.

I think listening to your sailmaker is excellent advice. If one is able to fault or better ones sailmaker, perhaps it is time to switch sailmakers or become a sailmaker <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

Sailing to our telltales is what we have always done. Sailing without telltales but to the luff curl is not so good in my experience. We set up our spi the same way in all conditions, but how hard we sheeted it differed a lot depending on how fast we went and what angles we aimed for. The latter is part of why some teams are blindingly fast while those who sails as two individuals on the same boat are slower in my opinion.
Not much hard facts there I am afraid. One piece we were always looking for was the switchover from "low and slow" to "fast and high". We found that in very low winds it paid off to not try and build so much virtual wind but sheet the spi loosely and go deep. At a certain point, we could sheet in a bit and build enough virtual wind to get better VMG.

Simon,
I would say that it is easier to make a spi with a flat cut deep by trimming it than making a spi cut deep flat by trimming it. Agree?

OK, tight luff then and drive it hard - I've gone for about 1/4 of a turn of the hand when you grab the luff.



yes. 100%

My older Goodall spin worked best with 1/2 turn of the hand "looseness" of the luff.

My newer Glaser spin works best with a tight luff--hard to even turn the hand 1/4.

The older one was easier to keep flying.

The newer one has a narrower sweet spot but is "hotter."

Photo of the newer one attached, but wind was light.

GP Sails have been very helpful and are very knowledgable sailors offering good advice and in discussions think that I'm heading along the right route to getting the best out of the sail.

However being from an engineering background it would be a bonus to find any articles with pictures of well set spinnakers or discussions on the merits of for example tight and slack luffs which there seems to be differing opinions on. On the GP spinnaker just tightening the luff 50mm made a big difference on the range of wind angles it liked. Do we tighten it further and what would the repercussions be ?.

Having only sailed with this sail a few times, there is a real learning curve and I guess experimentation is the key. <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" />

I guess the photo didn't stick; try this:

http://www.flickr.com/photos/cornerofthefield/2599587836/

Point is, every spinnaker cut is worked a bit differently, but you know when you're in the zone!