How to trim an asymmetrical spinnaker?

[dougweibel]

I have a 44' catamaran with a 4' bowsprit and a cruising asymmetrical spinnaker in a snuffer. I have not had a spinnaker on a previous boat. I have been having good success launching, retrieving and flying the spinnaker but I get the feeling I'm leaving a lot of performance on the table for lack of knowledge on how to trim it properly. Basically I just play with the sheet, and the tack line to a much lesser extent, to try to keep the sail full and stable.

My tack line is adjustable, but if there is much pressure in the sail I have no good way to do so at present as there is no purchase on it, just a clutch. I'm sure I could rig a couple blocks to take it to a winch if it is worth the effort.

Can someone enlighten me a bit and perhaps help me get from beginner to intermediate in terms of sail trim?

[Calif.Ted]

You want to keep the foot close to level, very low on the beam and raised as you go deeper, that's the "in a nutshell version". The video I'll attach has some good explanations and visuals but they don't get to trim until minute 9 if you want to fast forward thru the rigging part.
https://www.youtube.com/watch?time_c...ature=emb_logo
And you are absolutely right, there's a big advantage to good trim.

[barnakiel]

It depends on what cut the sail has.


As a very very very (=too) general rule:


- trim so that the luff is close collapse but not collapsing,
- except that in very deep angles trim so that max sail is out of the shadow of the main.


the pole square to the wind.


b.

[Calif.Ted]

He's probably not using a pole on an asymmetric cruising chute.

[Lazerbrains]

Originally Posted by barnakiel

the pole square to the wind.


b.

Most people don't use a pole with an asymmetrical - that's kinda the point of them.

[barnakiel]

Originally Posted by Lazerbrains

Most people don't use a pole with an asymmetrical - that's kinda the point of them.

Spinnaker in the thread title.


Not a kite, Not an assymetrical down wind sail.


A spinnaker.


By this I understood an asymmetrical spinnaker, as per thread title.



Q: If you are flying an assymetrical sail of the bow, how do you pull it away from under the main?
A: You square the pole with the wind....


EXCEPT ... for some very racy designs (like the assymetrical sail in some J-boats).


Please note that J-boats kites (built I think by North) are asymmetrical primarily in respect of max depth distribution, so that they pull themselves to the windward when you ease the sheet - no need to pull them out from under the main with a pole (a spinnaker pole).


Images:



assymetrical spinaker, pole, regular boat:
https://keyassets.timeincuk.net/insp...6/IMG_4116.jpg


asymmetrical sail for off the wind sailing, racing boat:
https://www.northsails.com/sailing/w...-2016-1200.jpg



Cheers,

barnakiel

[dougweibel]

Ted - thanks much.

Barnakeil - Catamaran, no pole. I could fly the tack from the upwind bow but I'd rather use a single setup and not be rigging differently for somewhat different points of sail.

[slug]

Similar to a Genoa

Sheet Leed aft Closehauled

Sheet leed forward reaching

Put some Tell tails On the sail and you will Learn sheet angles fast and understand how much To Deflect the sheet leed

And remember... always maximum...full hoist.on the halyard

[barnakiel]

Originally Posted by dougweibel

Ted - thanks much.

Barnakeil - Catamaran, no pole. I could fly the tack from the upwind bow but I'd rather use a single setup and not be rigging differently for somewhat different points of sail.

Guys and girls: sorry!


The cat part did not catch my eye. I have just paid for a quick reading course and now I know I should have ticked the 'with understanding' box too!


Stupid barnakiel. Apologies to all readers.


b.

[Cpt Mark]

Originally Posted by dougweibel

Ted - thanks much.

Barnakeil - Catamaran, no pole. I could fly the tack from the upwind bow but I'd rather use a single setup and not be rigging differently for somewhat different points of sail.

A bit more work. You run 2 lines on each of the port/starboard bows. Each bow now has a tack line and a clew line. This allows for a lot of adjustability as you sail.

[meirriba]

Some simple rules:
Halyard all the way up.
Coser to the wind: more tension on the tackline, more tension on the sheet. You may find a barber line on the working sheet to be beneficial when going upwind.
Going off wind, loose tackline, loose sheet, free the barber.
You may find going on broad angles, that it will be better to keep the main closer to boat's center than you think, to avoid blocking the assy.
I hope your spi sheets go from the clews far back to blocks near the sterns and not through the jib travelers!

[sailcrazy]

Following

[FabioC]

As other have said, the asymmetric is trimmed by keeping the luff on the verge of collapse (you ease the sheet and then bring it back when the luff starts curling to keep the sail on the verge).

Generally speaking, you do not play with the tack line too much, but it is very useful if you have the tack line on a winch, so you can ease it and trim it when needed. The asymmetric puts a lot of pressure on the tack line, even in moderate wind, so unless you have it on a winch, it is hard or impossible to trim it while the sail is flying. If you cannot trim it, you should not ease it either.

Depending on the cut of the sail, you may have to ease the tack line couple of feet going downwind in order to stabilize it. That is often the trick that allows you to fly the sail efficiently at deeper angles. On my boat, I also ease the tack line during inside jibes, to give a little more room to the sail to pass in front of the forestay. Of course, in a takedown, blowing the tack line before easing the halyard makes it much simpler to bring the sail in in a controlled fashion.

[dougweibel]

Merriba - Yes, my sheet goes to a block far aft. I have already learned about hauling the main closer to centerline from my Code 0. That has been very helpful in lighter winds when the foresail won't tolerate loosing pressure to the main. If using a barberhauler are you attempting to pull the sheet down or in?

Fabio - Can you elaborate on blowing the tack line - do you mean easing considerably or letting it completely loose?

[CassidyNZ]

My asymmetric “spinnaker” (I know it as a gennaker) has a non-adjustable tack line onto the anchor roller bracket that sets the tack a little way above the pulpit. I’m not sure that I understand the benefit of having this line adjustable.

I agree that the best draw from a gennaker is when the luff has a slight tendency to curl inwards. I used to fly my spinnakers (tri-radial, radial head) exactly the same way.

Your sheets should be long enough so that, when gibing the bag, you can let it all the way out the front of the boat and bring it in on the other side.

As far as gathering it in when dousing, it’s hard to beat a dousing sock to control the sail. Also much easier to wrestle it back into the sailbag.