Forums > Land Yacht Sailing Sail making

mast bend for luff...

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Created by greenE > 9 months ago, 12 Jun 2013
greenE
47 posts
12 Jun 2013 4:37PM
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hiya,ive read somewhere that windsurfers use a 30kg weight to test mast curv/luff, my question is;- as i understand it windsurfers have more downhaul forces than landyachts? and as the mast will be stiffened up for the first 600mm or so,how much weight would you put onto it to test curve for luff recut? being as i havnt built my chassis yet i cant rig the mast up and give it downhaul to see,ive tried making the luff template to cut luff but id rather measure the mast curve and cut to suit it ,any ideas guys? cheers,greenE

greenE
47 posts
12 Jun 2013 4:42PM
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landyacht;- in your thread you mention 'lay the pocket flat,max width should be 240mm', do you mean open up the pocket flat? because mine is (cant remember of top of my head, but if it were opened up flat it would be max circa 40cm)

i guess you mean lay it flat doubled as it comes off the sail?

Test pilot 1
WA, 1430 posts
12 Jun 2013 8:12PM
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landyacht
WA, 5921 posts
12 Jun 2013 8:32PM
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greenE said..

landyacht;- in your thread you mention 'lay the pocket flat,max width should be 240mm', do you mean open up the pocket flat? because mine is (cant remember of top of my head, but if it were opened up flat it would be max circa 40cm)

i guess you mean lay it flat doubled as it comes off the sail?


with a 5.5m class 5 sail the pocket max layed flatand doubled over is 120mm ,so 240 mm opened up. But dont forget to add on 15mm each side for the seam.
regards the mast curve measuring . I use 30 kg ,on my masts, that way I can derive the same mast curve number that they use. .I look out for masts with IMCS numbers of 25 and higher. my cl 5mast has a IMCS of 35

greenE
47 posts
12 Jun 2013 10:10PM
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ok pocket mystery explained,thanks. my mast is a fibrespar 460 25/25 seems pretty damn stiff but what do i know searching for something to stiffen up the first 600-700 mm at the moment, or should i use bit longer piece being as the mast is 25/25 and your using 35's with how long a stiffener?

greenE
47 posts
13 Jun 2013 4:43AM
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im just about to trim the pocket,im unsure exactly what to do,now as it lays flat on the floor it is wide at the bottom and tapering to the top, looking at some of your pictures it looks as if you have cut the pocket straight like a tube(not tapered). or is it because the sails not hauled in tight?

Chook2
WA, 1249 posts
13 Jun 2013 10:12AM
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Hi, some of the sails particularly "Gaastra" have VERY wide middle sections on the mast pockets (tapering down to a very narrow "pin top" tip) to accommodate the batten cams and zips, on the bottom 3 or 4 battens.

I take this into allowance trimming the sail, so the front edge of the template matches the front edge of the mast pocket. (I do this so the cams will fit back in and I don't have the hassle of retrimming the mast pocket.)

If you have already finished off all the batten reinforcing at the front, just trim the pocket parallel to suit and run a cigarette lighter up all the edge to stop it fraying.

Hope this helps.

landyacht
WA, 5921 posts
13 Jun 2013 9:24PM
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greenE said..

im just about to trim the pocket,im unsure exactly what to do,now as it lays flat on the floor it is wide at the bottom and tapering to the top, looking at some of your pictures it looks as if you have cut the pocket straight like a tube(not tapered). or is it because the sails not hauled in tight?


the untapered pockets are class 5 spec pockets. on my minis i make a tapered pocket. If you dont have any ally wood suitable for a base, look for a broken windsurfer mast top. My IMCS 35 mast are all ally tubing , not carbon. but I recon you could make one with windsurfer masts

greenE
47 posts
15 Jun 2013 3:19AM
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ok thankyou for your help ,v69 thread arrived today,going to get stitching tomorrow ;-)



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"mast bend for luff..." started by greenE