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Trimming old sails for DH
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ittiandro



Joined: 22 Nov 2009
Posts: 251

PostPosted: Mon Aug 26, 2019 12:48 pm    Post subject: Trimming old sails for DH Reply with quote

I have bought a 2nd hand NP Garda sail 6.2 m2. I donít know the year it came out but I believe it is an old sail, still in incredibly good condition and a very good look, though.

As I look at it, the design is quite different from todayís sails, and probably not as efficient, but I bought it because of the excellence of NP products and also because I believe that the difference in technology between older and newer sails , although very significant, can be wholly appreciated mostly by demanding performance seekers , but not by the run-of-the-mill windsurfer, like myself for whom leisurely cruising rather than speed or planing are the main priority. ( Besides, I donít need to spend $ 800 for a sail, just to cruise around)
Having said this, I'd like to be able to trim this sail as best as I can within the constraints of its design, particularly DH and here is where I need some help..

Modern sails, can be DH for more or less wind power by visually referring to the leech tension above the boom : typically, it is recommended to give a strong enough DH to pull the batten away from the mast on the upper part of the sail, ie a loose leech down to the boom, with a flat upper shape to spill the wind effectively. The upper leech tension can then be tweaked by adjusting the DH, while the bottom shape can be tweaked by increasing and decreasing the Outhaul.
Unfortunately, this visual reference is not possible with the Gardaís design, because the sail remains tight leeched from the tip down to the boom, no matter how much DH and it doesnít look to be designed for spilling the wind from the top.
I have a 460 cm 65% c.c. carbon mast and I have rigged the sail on my yard, experimenting with various DH, and with the mast extension at 42 cm. The lower shape looks good ( it can be increased or decreased with the Outhaul) but the upper leech remains as taut as aÖviolin string, even with the mast extension at 42 cm. It might loosen up with a stronger DH, but I donít know if it is designed for it. Also, I wouldnít like to snap the mast.

If anybody is familiar with the Garda, Iíd like to have comments and suggestions.

Thanks

Ittiandro
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dllee



Joined: 03 Jul 2009
Posts: 4604
Location: East Bay

PostPosted: Mon Aug 26, 2019 1:30 pm    Post subject: Reply with quote

NP's cheap sail, circa '86-90, no loose leech.
Rig full and baggy for light breeze.
Add downhaul to tighten luff sleeve for powered planing conditions.
Outhaul set so sail is almost touching inside of boom when sail is pressured.
6.2 Garda has windrange of modern rec 7.0, except at the very low end, where sheer size matters, so arguably, MORE efficient and waaay lighter, and more durable.
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isobars



Joined: 12 Dec 1999
Posts: 19325

PostPosted: Mon Aug 26, 2019 1:34 pm    Post subject: Reply with quote

I don't know about the Garda in particular, but many sails from the '80s and '90s sound like your description and emphasized one feature lacking in some of today's sails: low end (as in early planing) power at the cost of high end (overpowered) stability... a great asset for the objectives you seek. I think you found a big bang for your buck, and it doubles as an excellent foiling sail if you ever get into that.

But a near-foot-and-a-half extension for a 6.2 on a 460? Really? That sounds really strange, assuming you're DHing the sail pulley-to-cleat and have a non-adjustable or fully-shortened top fitting. I've probably just forgotten what mast I rigged my barely used 1980s Gaastra 5.7 well-named Power Foil on.
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dllee



Joined: 03 Jul 2009
Posts: 4604
Location: East Bay

PostPosted: Mon Aug 26, 2019 1:57 pm    Post subject: Reply with quote

1985-89 3 cams 5.7 rigged on 15'1" with 4-7" extension depending on exact year.
Elastic luff clouds the issue.
Rig to spec printed on foot of sail.
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ittiandro



Joined: 22 Nov 2009
Posts: 251

PostPosted: Mon Aug 26, 2019 2:53 pm    Post subject: Reply with quote

isobars wrote:


But a near-foot-and-a-half extension for a 6.2 on a 460? Really? That sounds really strange, assuming you're DHing the sail pulley-to-cleat and have a non-adjustable or fully-shortened top fitting. I've probably just forgotten what mast I rigged my barely used 1980s Gaastra 5.7 well-named Power Foil on.


Thanks Isobar

It is probably 39 cm because I am a few cm short of the cleat. I gave that extension in an attempt to loosen he leech, but if it is too much and the sail is not designed for a loose leech, anyway, I'll try less extension. How much , roughly? Less than 39 cm?

What do you mean by adjustable or fully shortened top fitting?

Ittiandro
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dllee



Joined: 03 Jul 2009
Posts: 4604
Location: East Bay

PostPosted: Mon Aug 26, 2019 3:25 pm    Post subject: Reply with quote

Read the specs printed on the foot of the sail and sailbag.
Heed.
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ittiandro



Joined: 22 Nov 2009
Posts: 251

PostPosted: Mon Aug 26, 2019 5:39 pm    Post subject: Reply with quote

dllee wrote:
Read the specs printed on the foot of the sail and sailbag.
Heed.

The only specs are for the luff and boom length. No reference to an approximate extension length for the DH.
True, the extension length for the DH can vary depending on the wind conditions, but not more than a few cm. If at 42 cm, the extension is too long, as Isobar thinks, it would help to have the spec for the recommended length.
This is why I asked.

Thanks

Ittiandro


Last edited by ittiandro on Mon Aug 26, 2019 6:11 pm; edited 1 time in total
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dllee



Joined: 03 Jul 2009
Posts: 4604
Location: East Bay

PostPosted: Mon Aug 26, 2019 5:45 pm    Post subject: Reply with quote

OMG......
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WNDZRFR



Joined: 28 Mar 2000
Posts: 86
Location: Greater East Bay Area

PostPosted: Mon Aug 26, 2019 5:56 pm    Post subject: Reply with quote

I'll bite... What are the luff and boom lengths printed on the sail?
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ittiandro



Joined: 22 Nov 2009
Posts: 251

PostPosted: Mon Aug 26, 2019 6:15 pm    Post subject: Reply with quote

WNDZRFR wrote:
I'll bite... What are the luff and boom lengths printed on the sail?


Luff 490 cm, boom 190 cm. Do you mean that we can infer the basic extension length I have to give?

Thanks

Ittiandro
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