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-   -   Backwinding main (https://www.boatbanter.com/cruising/46482-backwinding-main.html)

prodigal1 July 21st 05 07:10 PM

Jonathan Ganz wrote:

Ummm... isn't the hull speed 1.34x(sq.root of waterline)? So that
would be about 7 kts. Are you surfing or own a multi?


yes grasshopper, your math is correct and no I'm not surfing and no it's
not a multi

How did you arrive at the 8-10 kts?


well first we put up the main... sorry, couldn't resist
knotmeter, verified against gps, flat water on the windward shore, winds
25 gusting 35

There is some kind of voodoo involved in the design of this hull. The
older versions (like mine) of this hull design have a spoon entry, keel
longer than it is deep, with flattish, almost scow-like aft sections.
It's just friggin spooky how fast this thing can be. I can keep pace
with just about any cruising sailboat up to about 38'. Two years ago I
kept pace with a boat over a 22nm stretch going flat out downwind with
only the main wung out. He beat us into Killarney by about 1000m. It
was a 65' Hallberg-Rassy registered in Basel, Switzerland that was doing
the swee****er seas on its way around the world. The skipper of that
beautiful boat came over to see just what it was that he couldn't shake!

See fer yerself

http://www.clic.net/~dcooper/hinterh.../specside.html

the one pictured is the "newer" hull shape with a more upright entry and
a fuller aft section above the waterline. The shape below or the
profiles at the different stations are similar enough to be unchanged
from the earlier marques.

Jonathan Ganz July 21st 05 07:20 PM

In article ,
prodigal1 wrote:
Jonathan Ganz wrote:

Ummm... isn't the hull speed 1.34x(sq.root of waterline)? So that
would be about 7 kts. Are you surfing or own a multi?


yes grasshopper, your math is correct and no I'm not surfing and no it's
not a multi

How did you arrive at the 8-10 kts?


well first we put up the main... sorry, couldn't resist
knotmeter, verified against gps, flat water on the windward shore, winds
25 gusting 35


Funny guy... :-) Well, I was just trying to figure out how you
circumvented the laws of physics.

Looks like a great boat.

See fer yerself

http://www.clic.net/~dcooper/hinterh.../specside.html


Maybe it's the skipper...


--
Jonathan Ganz (j gan z @ $ail no w.c=o=m)
http://www.sailnow.com
"If there's no wind, row."


Roger Long July 22nd 05 01:56 AM

I guess maybe I don't want to know a lot mo) I thought the main
was in great shape because the foil sections look just like I'm used
to on airplanes. Now I can see that it's pretty aged. It isn't too
bad though. The maximum draft is at about 30% of the chord. There is
a pocket at the foot and nothing farther than about a foot from the
boom responds to outhaul tension.

OTOH, cunningham, another swig on the backstay and jib halyard,
traveler amidships, moving the sheet blocks back just a foot, and
easing the sheet for three more inches between spreader and sail makes
a dramatic difference. Speed length ratio of 1.22 in 10-12 knots of
wind and tacking to what was on the beam. That's good enough for
cruising. She'll point up higher with only a little speed penalty but
lots of backwinding.

The backwinding is different on one tack than the other. I think
that's a function of the weather cloth on the genoa effecting the
leach shape differently when it's to windward than when it's to
leeward. Another strike against roller furling sails.

--

Roger Long





Jere Lull July 22nd 05 02:22 AM

In article ,
"Roger Long" wrote:

Our boat seems to go well with the 140 genoa just touching the
spreader tips and the foot along the lifelines. Is this too tight to
expect a smooth main? By the time the wind is strong enough that I
need to ease her in the puffs, the main is often completely depowered
and flogging, even with the traveler nearly amidships.


That sounds about right though our boat & sails prefer a couple of
inches off the spreader, so your sheet blocks might be a bit too
forward. What do your telltales say at the luff?

I've found that our masthead rig works best by concentrating on the
jib/genny. When in doubt, the main is primarily there to balance the
boat.

I flatten our main with outhaul, halyard and cunningham most of the time
and start reefing it at about 12-15 knots. Main first and only
reluctantly jib. Under the conditions you describe, I'd prefer to switch
to the working jib and inboard sheet tracks, but I have the same
difficulty in switching sails.

BTW, I often bring the traveler up past centerline, sometimes even the
boom, to allow the upper main to twist off on the puffs. (our boom is
very heavy) I have streamers on the batten ends and don't let more than
one or two break.

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/

[email protected] July 23rd 05 09:22 PM

The backwinding is different on one tack than the other. I think
that's a function of the weather cloth on the genoa effecting the
leach shape differently when it's to windward than when it's to
leeward. Another strike against roller furling sails.


That's one possibility but it could be mast/rig tune also. If you can
get a good sail maker out on the boat, they can show you a lot. You
will also get a sales/sails pitch of course but that is to be expected
and may even be the right answer. There are basically two possible
reasons for excessive backwinding (a little when close hauled is OK):
Either the mainsail shape is too full or the jib draft is too far aft,
possibly even hooked. A main that is too full can usually be recut if
it is not too far gone and good use of sail controls such as
cunningham, halyard tension and outhaul can also help. If you have a
bendy mast, a little mast bend will flatten the sail but you need to
add more cunningham/halyard tension to get the draft back forward. If
the genoa is the primary problem the solution is different. Make sure
you do not have excessive headstay sag, that adds fullness and moves
the draft aft. Make sure the cars are not too far forward. If the
sail is basically in good condition and all else fails, have your
sailmaker recut with some extra leach hollow.



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