An \"offshore\" asym, use and design


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Dick
Dick
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Alchemy’s “offshore” asymmetrical spinnaker
When we bought Alchemy, a Valiant 42, it came with a ¾ oz 1670 square foot asym in a North Sails sock. This was ok for coastal sailing, but we (almost all our sailing is doublehanded, husband & wife) found it too large for offshore, not forgiving enough for wind changes, and a bit scary to handle in swelly offshore type conditions. Chris Wentz of ZSails designed and made us an 1.5 oz, 1200+ sf asym and put it in an ATN sock. We use this asym all the time as it is easy to work and figure we sail anywhere from 10-25% more a year than we would have otherwise, mostly sailing when we would have motored. We have 8 years with this sail and have been very happy with it.
The following is how we made the sail work for us.
Dick & Ginger Stevenson, s/v Alchemy
Observations:
1.   Over the first few years we had this asym, I kept track and worked out we sailed about 20+% more than we would have otherwise. An additional 10+% was spent with more satisfying speed and comfort than the resulting slatting/slapping of working sails being asked to take you downwind.
2.   Alchemy’s “offshore” asym
a.   Large enough to have up in 5-6 knots true wind speed
b.   Very forgiving; we have had it up for long periods with true winds in the 20s.
c.   Larger sail would be faster in light winds, but we care mostly about moving acceptably in light winds (ie not motoring) and a bit extra speed is not all that important as long as we are moving
d.   Not so scary when things go a little pear shaped
3.   1.5 oz cloth
a.   Seems to hold shape better when seas are a bit sloppy
b.   Seems to allow for better shape airfoil when going to wind
c.   May not fill so well in the zephyrs
d.   May collapse more easily when you outrun your wind
e.   But is much more forgiving in higher winds. We have used it in winds in the 20+k true
4.   Set up
a.   ATN sock preferable to old sail’s North sock
i.   Just generally works better, better design details
b.   Sock furling benefits from a block on the deck
i.   Allows you to pull into the deck when socking the asym with pennant
1.   I and others have been lifted off the deck socking a sail in conventional manner when it catches a puff ½ way down, filling and catching the foredeck crew by surprise
ii.   Some people recommend a ratcheting block which I have but have never really used as such
c.   We use an ATN tacker to hold the tack near the headstay
i.   North product for same function (with old sail) was of cloth and abraded stitching on the jib
ii.   The ATN Tacker is of smooth formed plastic, less abrasive
iii.   Our sailmaker wants the tack of the asym not to be restricted to the forestay but we like what feels like added control from doing so
d.   A 4-1 block & tackle gives control to the tack of about 4 feet (ATN Tacker slides up and down easily)
i.   Sail benefits from luff tension adjustment
1.   For us this is best done from the tack
2.   If adjusting halyard tension need to watch over-tensioning and having a splice get stuck in the throat of the sheave when tension unloads (see below)
e.   A full-release-under-tension snap shackle to the tack allows blowing the tack when pulling the sock down is hard/impossible otherwise
i.   The sail essentially streams downwind and socking is easier
1.   Rarely necessary, but really helpful in a pinch as it unloads the sail in an instant
f.    Asym sheets
i.   We have 2 medium to heavy weather ½ inch sheets of polyester
1.   They soak up water like a sponge and become very heavy
a.   Makes things very difficult in light conditions where the sheet dips into the water
2.   We will replace sometime soon (see below)
ii.   We have one ¼ inch Sta Set X lite Spectra
1.   Bought for light air use, but which we use all the time even into medium air
a.   Does not soak up water, a surprisingly big advantage
b.   Much lighter (even dry) so does not collapse the sail in light airs
c.   Strong enough for almost all times we use the sail
i.   So we use this sheet a lot
g.   Asym halyard
i.   If you use a shackle, tie it on with a knot, a buntline hitch is my choice
1.   A splice may/will get pulled into the throat of the sheave at the mast head making lowering the sail impossible without someone going up the mast. This will not happen with a knot.
2.   Shackles are undependable enough that I am considering doing away with it and just tying the halyard to the head with a bowline
a.   May make hard to hoist high enough??
ii.   I am not racing so I do not mind a bit of give in my halyard (not so jib & main) to absorb gusts so I have a conventional polyester double braid. It also takes a knot well (the aforementioned buntline hitch for the shackle).
h.   Hourglassing
i.   Only happened once to us
ii.   Seems more likely in light air DDW (dead down wind) with swell or shifty winds
iii.   Use a “singlehanders” spinnaker net
1.   Pull jib clew out 6-8 feet or so (to staysail) and fix sheets firmly amidships
a.   If hourglass occurs (less likely with the jib cloth in the way) rolling up the jib loosens the asym and allows untwisting the hourglass
i.   I look with envy at bow extension poles for the tack, but have no experience
j.   I have played with using the whisker pole for the clew, but generally have been happy without
i.   Seems too complicated and prone to problems
ii.   Might try on a light air passage
iii.   Dousing mainsail often gets the asym clean air
k.   Find way to use easily
i.   On Alchemy the asym lives on a shelf in the forepeak.
1.   This allows the sail to be ready to go below decks but protected
2.   Opening a hatch allows sail to be hoisted right from the forepeak
3.   Dousing goes right down the hatch in its sock ready to go again
a.   Our forepeak cushions have a waterproof cover when we are offshore (which is the only time we bother to put on the waterproof covers) so a wet sail can be brought down the hatch without worry
b.   Putting back on shelf can be done whenever as the sail is immediately out of the way and free from spray etc.
i.   Offshore, the sail may just stay like that for long periods. Ready to go but out of the way
4.   No reason a bag could not be fixed below the hatch when storage is in a bag rather than a shelf
5.   Pointing/use
a.   Often with not a lot of distance to go, we just hoist the asym without the main
i.   Below 140 degrees the main blankets the asym (depending on tack placement)
ii.   With set up described we never need the main to blanket the asym to douse
b.   We can & do carry the asym up to 70 (sometimes 60, depending on wind strength and sea state) degrees AWA
i.   In light air this is very powerful and we get almost hull speed in 6-7 knots true and sail ok down t 3-4 k true
1.   More wind and the boat just gets overwhelmed unless very careful handsteering (something rarely done on our boat) is done and over 8-9 knots TW we will go almost as fast with a lot less unnecessary excitement with the jib.
c.   DDW the sail does just fine unless there is a big swell from the side, even to the point of sailing by the lee a bit (again small seas)
d.   With 2 sheets attached (we often use only one sheet if we think the wind is predictable), gybing the asym around the forestay is very easy
e.   On a displacement boat we are unconvinced that tacking downwind is faster (actually we are convinced it is not faster) than heading straight to destination so we always try to sail our course
6.   Design
a.   Not sure what in the design allows such close sheeting.
i.   Certainly the 1.5 oz allows for a stiffer leading edge and the sail to stand up better
ii.   The adjustable tack height also contributes
b.   Little is more annoying than a skirt which gets wet with salt water when dousing and just as you wish to store it
i.   Design so skirt at full hoist stays out of water even on a rolling boat
ii.   Always pull sail up full hoist (to keep out of water)
1.   Make tension adjustments at the tack
2.   This means you do not have to play with halyard tension
Dan Coate
Dan Coate
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Dick: Just reading this after your reply to my Parasailor post. Thanks so much. VERY helpful. Hazel James came with an lighter-weight asymmetrical, I’ve got a shorter downwind passage soon (BVI to Florida) and will play with it on that passage based on your recommendations, then look into getting more of an offshore asymmetrical made. Thanks again.
GO

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