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PostPosted: Wed Jun 27, 2012 7:10 am 
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Dropped the mast de-rigging, it bent the mast 8' up from base, small bend, can fix that, but left a good size dent in mast where it landed on rear crossbar, my question; do dents kill the integrity of mast? Is it a big toothpick for the Jolly Green Giant or a flag pole or can it be used for casual sailing, no big winds? Thanks. [url]Image[/url]


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PostPosted: Wed Jun 27, 2012 11:38 pm 
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The mast looks like scrap metal to me. Probably a matter of time for it to fail, and I wouldn't trust it.


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PostPosted: Thu Jun 28, 2012 4:12 am 
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+1

I wouldn't trust that at all.


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PostPosted: Thu Jun 28, 2012 6:19 am 
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If you plan to Sail at over 90knots per hour, or if you are going to hold the weight of the San Francisco Bridge with it, DON`T USE IT !!!!!
Otherwise, I don`t see it will cause you to sink an Aircraft Carrier or kill a couple of almost-extinct Manatees if it bends completely while sailing.
I say go sailing, unless you are afraid of "Life not being Perfect" !!!!!

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Every second that passes cannot be recovered, so make good use of every one of them that you have left.


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PostPosted: Thu Jun 28, 2012 7:19 am 
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Joined: Thu Dec 20, 2007 1:33 pm
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Location: Southern California
I have spare mast from a 78 H16 you can have for free.

You will have to come to Los Angeles to pick it up.

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1979 Hobie (sold)
1983 Hobie 16 Hawiian Sunset (sold)
1981 Hobie 16 Tequilla Sunrise - still own
2008 Hobie 16 (currently sailing the crap out of this boat)
1977 Super Sunfish
John


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PostPosted: Thu Jun 28, 2012 8:14 am 
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John, sure like to take you up on the offer!
On the technical side of stress and bending, is there a lot of stress 8' up from base, isn't most of it nearer the top or around the mast tang? How about a support slipped into mast from base? Finding a mast around here at a reasonable cost is almost impossible. I'll be taking it sailing when it's not 107, let you know how that turns out.


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PostPosted: Thu Jun 28, 2012 8:59 am 
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Location: Jersey Shore
sailthis wrote:
On the technical side of stress and bending, is there a lot of stress 8' up from base, isn't most of it nearer the top or around the mast tang?


YES, there is a lot of stress 8 feet up from the base. The mast section between the mast base and the shroud tang acts like a beam which is supported at both ends. Maximum bending moment occurs roughly at the midway point which, in the case of a H16, would be approximately 8 feet up from the base. This is why larger boats like H18s & H20s have spreaders/diamond wires which are located roughly at the mid point between the mast base and the shroud tang.

Anything larger than a dent the size of a quarter, and I would not trust the mast for more than putzing around in light wind.

sm


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PostPosted: Thu Jun 28, 2012 9:57 am 
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Well, at 60, puzting around in light winds on a 75 acre lake is all I can do anyway, thanks all.


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PostPosted: Thu Jun 28, 2012 3:34 pm 
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I agree that that is where the stress is focused, but also by that logic, the mast spreaders are designed to prevent left to right flex, not aft. I think that yes, this mast is weakened, but as long as you don't crank down on the mainsheet in an attempt to get it to touch the rear cross bar, most of the stress is not going in that direction.

Of course, the safe answer is to replace it, and sail at your own risk...free advice is worth what you pay for it.

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1979 Hobie 16 "Orange Crusher"
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PostPosted: Fri Jul 27, 2012 11:52 am 
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On the technical side of stress and bending, is there a lot of stress 8' up from base, isn't most of it nearer the top or around the mast tang?


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PostPosted: Sat Jul 28, 2012 7:45 am 
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Location: Jersey Shore
alannmorriss wrote:
On the technical side of stress and bending, is there a lot of stress 8' up from base, isn't most of it nearer the top or around the mast tang?


Maximum bending deflection will occur roughly at the midway point beween the two support points. For a mast, the support points are the mast base and the mast tang, so the midway point would be roughly 8 to 10 feet up from the base. Another way of looking at it would be to consider a beam supported on both ends (like a floor joist), as you add weight to the beam it continues to deflect until it snaps in the middle. The mast is similar to this only turned up vertically.

The mast tang area also sees a lot of load because the section of mast above the tang is essentially a cantilever.

sm


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