asymetric sheet angle

[simonfraser]

i am about to order a flat - code 0 - asymetric set on a prodder
what sheet angle should i go for?
the few web pics i have seen for this have the sheet projecting to above half way of the luff, not half way - which would be correct for a genoa ??
i will have the block for the clew on a athwardship traveller, but there is no fore and aft adjustment.
the sail angles are likely to be 80 - 40 aparent
many thanks for your input, Simon

 

[bilbobaggins]

"I refer the Hon Gentleman to the private reply I gave him just a few moments ago...."

/forums/images/graemlins/wink.gif

 

[William_H]

I would suggest the athwart ships adjustment is not as important as fore and aft adjustment. On a mono you would sheet from as far outboard as possible while on a tri the sheeting could be inboard a little.
The fore and aft sheeting is the critical bit. At any point of sail if the sheeting is too far back then you will see the top half of the sail falling off to leeward and not working well while if the sheeting is too far forward the top half will be pulled tight and working while the bottom half does not have enough sheet tension. So it is a matter of aportioning the sheet tension to top and bottom.
However as you sail further off the wind and ease the sheet you will want the sheeting point further forward to keep the top working.
Off the wind it is better to sheet further outboard as you can have the sheet tighter without stalling the sail while for closer to the wind a sheeting point further inboard enables sailing closer to the wind.
olewill

 

[Jonny_H]

If you want to get seriously into sail sheeting etc, try Lawrie Smiths "The Science of Speed", and numerous other books on sail refinement.

I think the above is the best 'short' answer your likely to get without going into a 'racer's' debate over twinning lines, jockey poles, tweakers etc (which I could start off for you, but as this is a cruising forum and I suspect your not out to win the round-the-island race ...)

Incidentally, I will note that the large asy's on dinghies and sportsboats (from experince 13ft - 25ft) all sheet the asy from just aft of the normal genoa sheeting position. Of course, this then depends how you want to sail - sail quite high and go for speed, or bear off and go for depth, you'll need to adjust both sheeting angle and tack line length accordingly.

Jonny

 

[Jonny_H]

Just another thought - maybe you'll get a more technical answer on a racing forum?

Try www.yachtsandyachting.com/forum - a good forum for dinghy and keelboat racers.

Jonny

 

[Swagman]

Hi Simon,
We've a Code 0 and no adjustable blocks either. I'd suggest you would not wish to sheet onto a conventional genoa block set inside the safety lines.
We use both our spinnaker brace (postioned on toerail 50% along hull) and our spinnaker sheet (on toerail almost at stern) and trim the sail by adjusting both.
Beating we need more pressure running aft, and reaching vica versa.
But having this radical angle trimming ability also helps (in fact vital) when you get around to furling the bloody things up.
Ours is maybe 150% and a lightweight fabric which in a blow require lots of downward angle to roll the top closed when furling. We found if we attempted to furl from the midpoint sheet angle, the head remained open and flapped away when the lower section was already fully furled.
Hope you understand what I've explained.......and do not underestimate the loads you'll get onto a bowsprit so make sure its man enough for the job.
Cheers
JOHN