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 Post subject: slightly bent mast
PostPosted: Tue Oct 07, 2008 11:39 am 
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Location: Tri-Cities, WA
I installed a new mast a couple of years ago after a wind storm flipped my H17Sport while on the beach. Over the course of these 2 years the new mast has develope a broad bend in the mid section of the aluminum extrusion. The mast has never been dropped and is stored with the bolt track down eliminating these as possible reasons for the bend. I sail the boat hard in fairly heavy wind with a 8:1 downhaul. I've tried to get the bend out by locking down the mast horizontally at the base with the bend facing up and put a padded support under the bend with a bucket containing several bricks hanging from the mast at the tang for over a month. This did bot take out the bend. I'm leary of applying heat. Any suggestions????? :?: :?


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PostPosted: Wed Oct 15, 2008 1:25 pm 
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Joined: Mon Jul 25, 2005 8:20 pm
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Location: Campbell, CA
I would take a methodical approach to A.) quantifying the amount, direction and center of the bend. and B.) apply force in incrementally increasing amounts, measuring the result at each step.

If you have bending "off the 90" or a twist, you will probably have trouble restoring it. In any case you will need a lot of force: I suggest an archery bow approach using a cheap ratcheting come-along winch capable of a ton +/-, securing it to each end of the bent aluminum, and then a suspending member (i.e. the archer's "arrow") about a foot or two long located at the center (highest spot) of the bend.

Put the winch and suspender/member on, removing all cable slack. Measure and mark inch graduations on the cable leading to the entry of the winch, using a felt pen, so you can measure and record the increased shortening of the cable with each new try.

Pull in a few inches of cable, release, check, and repeat. Keeping the suspending member stable may require some sort of clamping affair, but I think this approach is sound but my main concern is kinking at the bend center. Just take things very slowly and watch out for adverse changes(wear safety goggles, and keep people away).

Good luck - and post pics!

Peace,

Dan Peake
2003 H17SE


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 Post subject:
PostPosted: Fri Oct 24, 2008 2:56 pm 
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Thanks Dan. I think I'll give your solution a try next spring if my long term, over the winter, approach doesn't work. The bend is pretty much in the center of the extrusion with no twist to it. My winter plan is to lay the mast flat with a sandbag under the bend (bend up). Place a couple more sand bags on the base and place another sandbag on the tang at the comptip interface. Monitor weekly and see if time and pressure will solve my problem. (maybe a month wasn't enough time, on my previous try). I'll post a pic once I have it set up. I'm still trying to sneek in a couple more sailing trips this season (made it out sailing 35 days this season so far). 8)


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 Post subject:
PostPosted: Tue Oct 28, 2008 3:47 pm 
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Location: Santa Cruz
I see you're using an aftermarket sail. Could it be that you're putting loads on the mast that it wasn't designed to handle? Sounds like the extra loads from the 8:1 downhaul are compressing the mast vertically then the extra power in the middle of the sail is causing it to bend. The reason I ask is that I saw a newish diamond wire break on an 18 with an aftermarket sq top this summer. Not the bolt, the wire. Never seen that before. What say you?

Does your halyard cleat at the top OK?

J


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 Post subject:
PostPosted: Thu Oct 30, 2008 2:32 pm 
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Location: Tri-Cities, WA
Surf city, all looks fine on the mast with the exception of the bend.


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 Post subject:
PostPosted: Thu Oct 30, 2008 10:04 pm 
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Location: Campbell, CA
35 sails this year - that is great! You've got me (and most people) beat - I'm probably at 30, next year it's 52!!! and at least five races.

You want to sail next spring/summer, so I suggest you measure things in a month to see if progress is being made. If after a month you observe no change, then try a different approach. But don't wait until Spring!

In my experience, tempered / annealed aluminum extrusions do not flow or sag slowly over time (think of commercial jet plane wings.)

Using characters to make my point; with a length of aluminum if you have a | and you want a ( you need to bend it to C , after which it will immediately flex back to a ( . In addition, when this permanent bending is happning, sudden and adverse molecular structural changes are occurring (hardening of the metal [brittle]).

If these masts were to bend slowly over time, with the forces of several sand bags, plane wings and boats masts would not be able to use this material. Sand bags as the chosen bending force is fine if you use enough of them, but if permanent bending is happening, it's happening now, not over months. And I believe once a mast is bent, even if bent back to its original form, the original strength it had can not be cost-effectively restored.

Tricky stuff. good luck.

Peace,

Dan Peake
2003 H17SE


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 Post subject:
PostPosted: Thu Oct 30, 2008 10:37 pm 
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Location: Santa Cruz
fastcat wrote:
Surf city, all looks fine on the mast with the exception of the bend.



What bent it?
J


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 Post subject:
PostPosted: Mon Nov 03, 2008 1:16 pm 
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J, as to what bent the mast - I do not know, but can speculate. I sail a wide spot of the Columbia River called Wallula Gap (Lake Wallula above McNairy Damn). As with Columbia Gorge, cliffs climb from each shore and create a funnel effect with the wind. Though unlike the Gorge the wind does not blow directly upstream, but at a bit of an angle. Because of that angle when pointing upwind you have long (sometimes very long) and short reaches between tacks. During mid summer the temperature is usually in the 90's and sometimes over 100F and due to thermal's can blow very hard on a regular basis (20-25+). Also, I sail fairly agressively in high wind with a square top sail, a 8:1 down haul and a 7:1 mainsheet. SO for the speculation: Combine black mast, hot weather, high wind, long unidirectional reaches (ie uneven mast loading) usuing a squaretop sail with tight downhaul/mainsheet has put the bend in the mast. :roll: :?:


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 Post subject:
PostPosted: Tue Nov 04, 2008 10:34 am 
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fastcat wrote:
J, as to what bent the mast - I do not know, but can speculate...usuing a squaretop sail with tight downhaul/mainsheet has put the bend in the mast.


That's what I was getting at.


H17's playing in rough conditions on SF Bay:
Image

Image

J


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 Post subject:
PostPosted: Tue Nov 04, 2008 6:55 pm 
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Location: Campbell, CA
Hi Jeremy,

I love that pic - H17 pics don't get a lot better than that one! I think that guy was cutting through some ferry wake at the Tiger/17 Nationals event in 2006.

Peace,

Dan


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 Post subject: Bent Mast
PostPosted: Mon Nov 10, 2008 11:50 pm 
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hi, i think you said you put a new mast on a few years ago, Maybe the mast had a bend from new, even if just a little, or maybe when you were setting up the mast someone decided to swing of the back while it was down. i have a h18 and when i set up to lift the mast, it sits on a bracket near the rear crossbar, after i put the pin through,, there is a lot of mast hanging over the back, if not supported at the end and someone applied downward force at the end, it would proberly put a bend in the mast, i know why would you do that,,,some people wouldn't realise that swinging of the mast while its down would do any harm. i know my girlfriend would'nt. I hope that you get it sorted out. Cheers Pepsi1234 :wink:PS LOVE The pics with the bridge in the background.


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 Post subject:
PostPosted: Tue Nov 11, 2008 10:16 am 
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Location: Jersey Shore
Quote:
Also, I sail fairly agressively in high wind with a square top sail, a 8:1 down haul and a 7:1 mainsheet.


Since you're obviously not racing that rig, at least not one design, maybe you should consider installing a set of spreaders / diamond wires on the mast. Probably wouldn't be difficult and would give some level of insurance against bending/breaking the mast. I would think H18, H20, or Tiger spreaders would work. Just a thought.

sm


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 Post subject:
PostPosted: Tue Nov 11, 2008 5:19 pm 
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Location: Tri-Cities, WA
srm, Ive considered the spreader wire idea, but am concerned that the comp tip would then take a greater share of the load and possibly fail.

pepsi12w, when I first got the mast I checked it out very carefully and it appeared OK. My first inclination about the bend was just what you said, that the mast bend was a result of hanging over the end of the rear crossbar while stepping. My first cure attempt was to hang the mast over the rear crossbar (padded) as if stepping, but with the bend up. After a couple weeks of no results, I even put a bucket of 6 bricks hanging from the thang for a couple more weeks. Still no effect. I would think if the relatively short time it takes to step the mast put the bend in, then the month of time I tried to streighten it in a similiar fashion should have worked. This time I'm supporting both ends of the alum extrusion, bend up, with a 70 lb bag of sand on the bend. I'll check it every few weeks over the winter.


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 Post subject: Bent Mast
PostPosted: Tue Nov 11, 2008 7:56 pm 
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its hard to know what's going on there, did the mast come from Hobie or after market, Did it come complete with tangs ex fitted or was that done
later when you received the mast. does the mast affect performance, Has the mast got the bend right near the tang that holds your diamond wires.
if so can you move this tang above the bend thus relieving the force applied
in that area. Hmmmm :wink:


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 Post subject:
PostPosted: Fri Mar 13, 2009 12:07 pm 
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Location: Tri-Cities, WA
Well, by mid February very little changed, so I upped the anti and added three 1 cu ft bags of steer manure to the 70 lbs of sand (you can guess what I call this phase of the fix). I checked last week and there appears be a slight change for the better. Time will tell. Mean while I’m sewing up a new comp tip cover to replace my previous sun rotted one (doin its job). My previous cover was duck cloth (cotton canvas) and lasted 5 years, the new one will be out of polyester pack cloth and should last much longer. :wink:


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