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dumb ?: threading downhaul line mast extension
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B737



Joined: 27 Mar 2009
Posts: 181
Location: Jersey Shore

PostPosted: Sat Mar 31, 2012 7:38 pm    Post subject: dumb ?: threading downhaul line mast extension Reply with quote

okay back to sailing one oh one for me...
this problem is starting to bug me, im assuming im threading the downhaul line incorrectly...

i start out with this...
which looks all well and good, lined up...





then once i down haul it all the way the line slips halfway off the last roller on the sail. sails fine but i can see where my lines are chaffing and risk snapping. anyone else have this problem?



in real life its worse than the photo, the downhaul line is riding on the edge of the pully right before it enters the cleat.

I tried another way where the line goes from the chinook attachment knot on the base, directly down into the adjacent mast extension pully then back up, instead of to the sail first, but when i do it that way i dont have enough wraps on the sail pulleys.

this thread is going to get very confusing Smile

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coachg



Joined: 10 Sep 2000
Posts: 1995

PostPosted: Sat Mar 31, 2012 8:03 pm    Post subject: Reply with quote

It may just be an optical illusion but in the second photo your extension looks bent.

How long is the extension? I had the same problem with my Naish 4.5 Force which has a luff of 400 & rigs on a 400 mast. When using a 28 cm RDM extension set to 0 there was so much extension shoved up into the mast that the bottom of the mast wasn’t bending correctly and the downhaul line kept sliding off and binding at the same spot yours is. I fixed the problem by getting a 10 cm extension so there is only 10 cm shoved up into the mast instead of 28. Now the mast bends properly and it rigs nice & clean.

Coachg
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kmf



Joined: 02 Apr 2001
Posts: 319

PostPosted: Sat Mar 31, 2012 8:08 pm    Post subject: Reply with quote

Here is the correct method.
http://vimeo.com/5426810

KMF
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johnl



Joined: 05 Jun 1994
Posts: 1160
Location: Hood River OR

PostPosted: Sat Mar 31, 2012 8:33 pm    Post subject: Reply with quote

Hmm, I must be getting old. It looks fine to me. That is as fine as it will get given the equipment. The width of the pulley on the sails is narrower than the pulleys on the extension. So the closer they get, the more they don't align. Similar to a bicycle chain and why you don't shift when you are in the extreme outside gears.

Unfortunately the video shows the pulley on the sail 90 degrees to the pulley you use. So I'm not sure what that video will show you since it doesn't really apply.

You can also put the knot on the extension on the inside and route the line to the outside, but I don't think that will help you at all...

I would say if you are that worried about it, change the extension length and don't downhaul it flush.


Last edited by johnl on Sun Apr 01, 2012 10:42 am; edited 1 time in total
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B737



Joined: 27 Mar 2009
Posts: 181
Location: Jersey Shore

PostPosted: Sat Mar 31, 2012 9:32 pm    Post subject: Reply with quote

thanks gents

i wasnt sure if it was maybe normal or not given the configuration. it just didnt seem right to me...

the extension is a 36cm ext in a 400cm mast, i suppose i should be using a stubby ext for base setting this low...

in the photo its hard to tell but the line is forcefully against the side of the sail pulley...

when i searched the web for 'how to thread downhaul' all that came up was stuff about sail blocks that were 90 degrees from what mine is... the ones that are parallel rig up fine.

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jingebritsen



Joined: 21 Aug 2002
Posts: 2399

PostPosted: Sun Apr 01, 2012 4:27 am    Post subject: Reply with quote

the straps of the tack foot are slightly asymmetrical. a pretty minor amount of shifting the block around within its straps, and a few beach side extra rigs may resolve this. most noticeable in the fully down hauled pics.

if the minor shifting and stretching measures don't seem to work, add a glob of ding stick to the long side part of the block. doubt you'll have to bother, but it's the next step, right?

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isobars



Joined: 12 Dec 1999
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PostPosted: Sun Apr 01, 2012 8:34 am    Post subject: Reply with quote

JohnL's geometry observation is spot on and unavoidable; you've got a Chihuahua trying to hump a Mastiff. Either get a 4-pulley sail block or a narrower (all steel) extension block. I initially assumed you were rigging a 10.0 meter race sail, which would explain the need for three full wraps. I once wrapped my 6.2/460 tack (using two sail grommets; the sail has no pulleys) three times out of curiosity, and even with low-friction Spectra downhaul line it didn't seem to decrease downhaul effort significantly over the two-wrap method.

If there are no narrower extension blocks on the market, I'd suggest switching to Spectra line (it cuts DH effort noticeably), using two wraps rather than three, using a longer DH line so you can straighten your legs and back more for better leverage and less risk, and working on your DH technique and/or strength. Think about the difference between lifting a heavy barbell off the floor, with both your legs and your back bent significantly. That's WORK, and it's risky, and it's like DHing with a short line which leaves you all scrunched up near the pulleys. Now picture lifting that same barbell up from a low table, with your legs, back, and arms almost straight; that same barbell feels much lighter now, and your back maintains its proper slightly concave arch, your legs are doing all the lifting, and they are almost straight; no deep knee bends. Like that you could lift a barbell twice as heavy, or lift that same barbell with one hand, with much less risk to your back and knees.

Downhauling a 400-sized sail needn't require both hands, let alone three wraps, if you get everything else right.


Last edited by isobars on Sun Apr 01, 2012 11:36 am; edited 1 time in total
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U2U2U2



Joined: 06 Jul 2001
Posts: 3056
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Sun Apr 01, 2012 9:16 am    Post subject: Reply with quote

no not dumb

the look of your rigging seems fine to me.

the pulley seems a-ok so far as alignment.

My contribution is get that white slippery line, that costs like twicw as much but will last a really long time

my 2 ˘

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jingebritsen



Joined: 21 Aug 2002
Posts: 2399

PostPosted: Sun Apr 01, 2012 9:58 am    Post subject: Reply with quote

the last pic with the red arrow shows it best. notice how the lowest tack foot strap is slightly longer. makes the the hard and fast sewn in block shift toward the cleat. makes the line crawl up that pulley. getting slippery line without the jacket would help, but may not allow a burnt end. get out your whipping kit to keep the line end from unraveling.
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kmf



Joined: 02 Apr 2001
Posts: 319

PostPosted: Sun Apr 01, 2012 10:32 am    Post subject: Reply with quote

Like isobars, I use spectra line. Dale Cook recommended it, so I tried a length on one of my mast bases, and went OHHHH! Now it's the only line I use for down haul. It is smaller than the blue stuff, rigs smoother, and lasts longer. Try it.

KMF
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