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Luff and boom specs
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skyking1231



Joined: 10 Jul 2000
Posts: 80

PostPosted: Mon Jan 21, 2013 2:30 pm    Post subject: Luff and boom specs Reply with quote

wanted to know form others how accurate do you find these numbers to be.

some of my sails are pretty accurate. However the other day i was rigging my 3.7 for the 1st time, which has a luff of 374 and boom of 137cm. I rigged it on a 370 mast with my extension +6cm for a luff of 376 and had it downhauled all the way. And it seemed that it could have used more downhaul. Also the boom @ 137 was not enough at all. I had to set it to 139 and then went with 141cm (according to my boom). My 370 mast is actually 370.5 cm measured. I didn't measure the actual boom length to see if the markings are correct. If I measure the boom...do you mesure from the inside of boom clamp or from the mast to clew?
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keycocker



Joined: 10 Jul 2005
Posts: 3538

PostPosted: Mon Jan 21, 2013 2:49 pm    Post subject: Reply with quote

The printing on sails has to be ordered early. Often the sail isn't quite tweaked yet and the numbers can very far off.
Ignore them
Rig correctly by looking at the sail.
Measure later if you are curious. Most folks lose interest once the sail is rigged right.
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zirtaeb



Joined: 03 Jul 2009
Posts: 2444

PostPosted: Mon Jan 21, 2013 3:07 pm    Post subject: Reply with quote

As said, the printed specs are for the prototype sails, not for the real production sails.
So use the #'s as a rough guide.
Set it there, but TUNE the sail correctly, and write down those specs.
It's not science, it's ART.
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skyking1231



Joined: 10 Jul 2000
Posts: 80

PostPosted: Mon Jan 21, 2013 3:11 pm    Post subject: Reply with quote

yeah... i guess i was getting either too lazy or dependant on numbers and wanted to be spoon fed.

i'll use the numbers as a starting point...then go from there.

thanks
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DanWeiss



Joined: 24 Jun 2008
Posts: 1979
Location: Connecticut, USA

PostPosted: Mon Jan 21, 2013 5:53 pm    Post subject: Reply with quote

skyking, the most accurate way to measure is as follows:

DH: Take the length of your mast, including any top fitting and add that to the extension length which itself is measured from the bottom of the mast to the aft-most corner of the pulleys. Only this way can you avoid deviations in printed adjustment and different methods of measuring to get to those printed numbers on the extensions.

OH: measure from the back of the mast to the front of the clew ring. That's most common, because there always is a clew ring but not always the same extension of reinforcement behind it.

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boardsurfr



Joined: 23 Aug 2001
Posts: 597

PostPosted: Mon Jan 21, 2013 6:02 pm    Post subject: Reply with quote

The numbers also depend on the mast you're using. When we replaced an old 100% Gaastra RDM 400 mast with a new 100% Maui Sails RDM, the downhaul settings changed by 4 cm (for a Manic 4.5 sail).

The Gaastra mast was a few years old, and had seen a lot of use. It died of old age, breaking while lying around on the beach (rigged and in the sun, but September morning sun in MA, with temps in the 60s). The Maui sails mast that replaced it was about as close as you can get in bent curve, both are hard top. The Gaastra Manic sails we use the masts for still work beautifully with the MS mast, but the numbers are quite different.
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skyking1231



Joined: 10 Jul 2000
Posts: 80

PostPosted: Mon Jan 21, 2013 10:31 pm    Post subject: Reply with quote

That makes sense with the outhaul....

Now that i think about it i will have to double check my adjustable top on my 3.7. I know it is pretty tight, but maybe it slipped or moved a cm or two.
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jingebritsen



Joined: 21 Aug 2002
Posts: 2501

PostPosted: Tue Jan 22, 2013 6:01 am    Post subject: Reply with quote

to complicate stuff even a bit further, some component brands are way off on their dimension markings. double check those figures. also, have a sharpie available to mark the proper settings on the foot of the sail. makes it easier for you and any other user.
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DanWeiss



Joined: 24 Jun 2008
Posts: 1979
Location: Connecticut, USA

PostPosted: Tue Jan 22, 2013 1:16 pm    Post subject: Reply with quote

skyking1231 wrote:
That makes sense with the outhaul....

Now that i think about it i will have to double check my adjustable top on my 3.7. I know it is pretty tight, but maybe it slipped or moved a cm or two.


That's a good idea. Also, nylon straps can stretch when wet, as does most DH and OH line.

To clarify, do not rely on the printed distances on any piece of windsurfing gear. You need to actually measure the mast using a tape, and do the same with the base extension adjusted to where you think it should be, then downhaul and only then get a true measure of the total, adding your measured mast length plus the distance from the bottom of the mast to the sail's DH pulley. As John I says, extension brands use very different reference points when calculating distance for printing the measurements on the tube. See difference, for example, between Chinook and Maui Sails extensions and what 10cm actually measures on each.

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cgoudie1



Joined: 10 Apr 2006
Posts: 1333
Location: Killer Sturgeon Cove

PostPosted: Tue Jan 22, 2013 1:27 pm    Post subject: Reply with quote

I might also add that, over time, sails (even the latest designs) do stretch,
and that will also change the settings. You should always rig by how the
sail looks, not by what's printed on it.

-Craig
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