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Shortening a Mast Extension?
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manuel



Joined: 08 Oct 2007
Posts: 1105

PostPosted: Tue Jan 26, 2021 10:51 am    Post subject: Reply with quote

I use mast tip extension to fine tune my downhaul tension especially right around the 27-30cm.

Super easy, cut off the tip of a broken mast top, use a wider part as a sleeve and just tape or epoxy the pieces together. Then electrical tape to hold the extension in place so it doesn't stay stuck in the mast luff sleeve.

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coachg



Joined: 10 Sep 2000
Posts: 3065

PostPosted: Tue Jan 26, 2021 7:03 pm    Post subject: Reply with quote

Here is a 42 cm HPL & 12 cm Chinook, both aluminum. Sail is a Naish 4.5 Force with 400 cm luff & recommended 400 RDM mast. Obviously I can't get 0 at the bottom so I have let a couple of cm out at the top.

With the HPL 42 cm extension you can see immediately how stiff the bottom is and how much more diagonally the lines are angled towards the mast than with the Chinook 12 cm extension. With the HPL the inner most line constantly pops off the pulley when down hauling. There is also much more friction with the HPL when down hauling. The other issue I have with the longer extension is that to rig the sail correctly I actually have to move the collar up 2 cm, thus letting out more at the top, to get the bottom set properly. You can see the difference in how the luff sits against the mast with the long extension vs how it sits off the mast with the short.

Bottom line the shorter extension makes the sail much easier to rig properly. You won't know until you try.

Coachg



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grantmac017



Joined: 04 Aug 2016
Posts: 924

PostPosted: Tue Jan 26, 2021 9:52 pm    Post subject: Reply with quote

Quite a few companies make 30cm extensions. Duotone makes the very excellent XT which works particularly well for slalom kit.
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ss59



Joined: 10 Nov 2016
Posts: 94

PostPosted: Wed Jan 27, 2021 4:12 am    Post subject: Reply with quote

coachg wrote:
Here is a 42 cm HPL & 12 cm Chinook, both aluminum. Sail is a Naish 4.5 Force with 400 cm luff & recommended 400 RDM mast. Obviously I can't get 0 at the bottom so I have let a couple of cm out at the top.

With the HPL 42 cm extension you can see immediately how stiff the bottom is and how much more diagonally the lines are angled towards the mast than with the Chinook 12 cm extension. With the HPL the inner most line constantly pops off the pulley when down hauling. There is also much more friction with the HPL when down hauling. The other issue I have with the longer extension is that to rig the sail correctly I actually have to move the collar up 2 cm, thus letting out more at the top, to get the bottom set properly. You can see the difference in how the luff sits against the mast with the long extension vs how it sits off the mast with the short.

The inboard tack pulley on the sail is in the identical position with both extensions, relative to the inboard-most extension pully.

Bottom line the shorter extension makes the sail much easier to rig properly. You won't know until you try.

Coachg

Isn't the variance in rigging between the HPL and the chinook down to the difference in the positioning of the pulley wheels on the two extension. The Chinook pully wheels are significantly further out from the mast than the HPL- you can see this before tension is applied. Isn't this the difference rather than the mast extension causing less flex in the (very stiff) bottom of the mast?
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coachg



Joined: 10 Sep 2000
Posts: 3065

PostPosted: Wed Jan 27, 2021 11:21 am    Post subject: Reply with quote

ss59,

It could be. I have a longer chinook extension that I could try but it is a U.S. base, not Euro so it doesn't get as low in the base. I'll compare the short Chinook U.S. with the long Chinook U.S.

Coachg
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westender



Joined: 02 Aug 2007
Posts: 1270
Location: Portland / Gorge

PostPosted: Wed Jan 27, 2021 1:53 pm    Post subject: Reply with quote

Mamero has idle hands. He should go ahead and cut the bottom off like he wanted to in the first place.
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isobars



Joined: 12 Dec 1999
Posts: 20128

PostPosted: Wed Jan 27, 2021 6:08 pm    Post subject: Reply with quote

I bought the biggest van Ford made in 1988, then spent two freaking years* converting it into a full-featured motor home designed (by me) expressly for chasing wind. Wiring looms inside the "bulkheads", hand-crafted oak cabinetry, a toy attic that held six boards plus masts and sails indoors, hot and cold running water, queen-sized bed, full galley, vented indoor 2Kw generator, complex custom security system, much more. Guests sitting inside had to look very closely to tell I had 6 boards and 6 complete rigs inside, and there were no outside tells that there was a fortune in WSing gear inside.

* It took two freaking years because everything was perfectly designed and executed. When I sold it 14 years and a couple of hundred thousand miles later, every modification I made still worked as I intended because my battle against wasteful perfectionism was only partially successful.

The one thing I did by eye, without using a buttload of tools and instruments, was cut a hole for and installing a BRIGHT driver-controlled floodlamp in the rear door for backing up safely (it was mere coincidence that nobody in his right mind tailgated me at night). That danged imperfect cutout, like a picture hung not quite right, was visibly off-kilter because after two years I was sick of perfection and just wanted to hit the road. It bothered me for years.

We should just let the poor man spend months shortening his danged extension the HARD way. He'll probably be happy with his choice right up 'til the minute he hangs water sports up for good and laments, "Damn. Wish I had spent that time windsurfing rather than reinventing that danged extension." Very Happy

Why is the van conversion story relevant? Because it taught me to just buy a Minnie Winnie and hit the road the next time.

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skyking1231



Joined: 10 Jul 2000
Posts: 260

PostPosted: Wed Feb 17, 2021 7:24 am    Post subject: Reply with quote

cut it..... think of the weight savings ! we are talking about shedding some grams here Very Happy jk
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d0uglass



Joined: 28 May 2004
Posts: 1278
Location: Bonita Springs, Florida

PostPosted: Wed Feb 17, 2021 12:26 pm    Post subject: Reply with quote

I cut a chinook rdm mast base from the top after it got bent. Just used a hacksaw. Works fine. Should be no problem chopping the top 10 cm off a 48 cm extension.
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isobars



Joined: 12 Dec 1999
Posts: 20128

PostPosted: Wed Feb 17, 2021 4:46 pm    Post subject: Reply with quote

To help get a nice straight cut, I put a hose clamp on the extension/boom/mast/etc. first and use it for a guide. Just make sure to cut on the intended side of the hose clamp.
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