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 Post subject: Shrinkage
PostPosted: Wed Jun 12, 2013 4:35 pm 
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Joined: Tue Jul 19, 2005 6:29 pm
Posts: 1891
Location: High Point, NC
Here's one for the Islanders to consider...

The mast/sail bag on my Tandem Island is about 4 inches longer than the mast. Everything fits nicely, with room to spare. At least here in the shop.

Between the time I bag it up, and drive to the local lake where I normally sail (about 15 to 20 minutes tops) the bag will have shrunk and the end of the mast is exposed from the bag. I'd say it's about an inch shorter than the mast length. It will stay this way all day and to my arrival back here at the shop, at which point I generally removed the bag in order to allow the sail to dry.

The next time I bag the mast, the bag is again 4 inches longer than the mast.

I have checked several times to make sure I'm not putting the TI mast in the AI mast bag (I'm not and have them clearly marked). This shrinkage is consistent regardless of the season or the weather.

It's not a big deal and I understand nylon of that length will have some expansion and contraction, but 5 inches of difference, every time out regardless of temp, humidity, etc., really has me dumbfounded.


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 Post subject: Re: Shrinkage
PostPosted: Wed Jun 12, 2013 5:34 pm 
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Joined: Thu Aug 16, 2007 2:25 pm
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Location: Central Coast NSW Australia
Yep, happens to both my AI and TI bags.
One of the great mysteries of life!


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 Post subject: Re: Shrinkage
PostPosted: Wed Jun 12, 2013 6:03 pm 
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Joined: Thu Oct 04, 2012 5:41 pm
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Location: Aussie living in San Diego, CA
When I saw the title of the post I thought it was about something else... :lol:
Anyway I have to say that I have been noticing the same thing and I spend a few minutes each time after sailing looking at the mast, looking at the bag and fiddling with it at an angle to try and make it fit, scratching my head and going home! Must be an explanation but so far its eluding me.

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 Post subject: Re: Shrinkage
PostPosted: Wed Jun 12, 2013 6:35 pm 
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Location: High Point, NC
Well, at least this assures me that I'm not crazy. Not completely, anyway.


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 Post subject: Re: Shrinkage
PostPosted: Wed Jun 12, 2013 9:26 pm 
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Location: Long Island NY
Don't ask a woman ...


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 Post subject: Re: Shrinkage
PostPosted: Thu Jun 13, 2013 3:53 am 
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Joined: Sun Apr 17, 2011 3:57 am
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Location: Fairfax, CA USA
I am so glad that this has been brought up. I don't get it either. Sometimes the bag is the proper length, sometimes too short.

The latest attempt at theory is a bit convoluted, and i am having trouble verifying.

I posit that the mast bag is actually too short. Here's why:
We all know that the clothes dryer can actually transform and teleport socks to become clothes hangars in your closet. I believe there is a third transient and unstable form of transformation. That third form is locked in an quantum entanglement with the mast bag. As the sock is being transformed into a hangar, the third form is an unstable intermediate state. When that third form decays, it releases energy that lengthens the mast bag, AND this increased energy completes the teleportation of the third form, in order to reach the stable "hangar state" there is a consumption of energy which due to the quantum entanglement consumes energy from the mast bag, which again shortens the bag to its stable "too short state".


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 Post subject: Re: Shrinkage
PostPosted: Thu Jun 13, 2013 8:41 am 
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Joined: Thu Oct 04, 2012 5:41 pm
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Location: Aussie living in San Diego, CA
now why didn't I think of that? :lol:

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 Post subject: Re: Shrinkage
PostPosted: Fri Jun 14, 2013 2:19 pm 
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Makes sense?


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 Post subject: Re: Shrinkage
PostPosted: Fri Jun 14, 2013 3:32 pm 
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Joined: Sat Nov 05, 2011 1:58 am
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Location: Forster, NSW, Australia
Here is my "left field" suggestion... When exposed to the heat of the sun, the bag doesn't change size, but the air inside the mast does, and expands the joint between the two halves, increasing the overall length. Is there a prize? :mrgreen:


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 Post subject: Re: Shrinkage
PostPosted: Fri Jun 14, 2013 4:02 pm 
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Location: High Point, NC
I keep the downhaul taut on my mast, so I don't think the two parts are separating. Remember, we're talking about a couple or three inches or more. Plus, the mast isn't airtight.

Something else is going on here and I think it's related to the bag.


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 Post subject: Re: Shrinkage
PostPosted: Fri Jun 14, 2013 7:08 pm 
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Location: Florida
My sails fit the canvas bags when bag is wet or at least damp. Let the bag sit all day in the sun or in a hot car and it gets bone dry and then the sail no longer fits. The shrinkage is a couple of inches and caused by the fabric shrinking. Like putting a wet sweater in a dryer. Even hair will change length with humidity I believe that is how some hygrometers measure humidity.


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 Post subject: Re: Shrinkage
PostPosted: Fri Jun 14, 2013 8:29 pm 
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Joined: Thu Jul 07, 2011 12:57 pm
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Location: Delaware Coast
I can attest to the fact that the sail/mast isn't changing sizes. I carry mine in a PVC carrier like the one shown below. I made it as short as possible and the end of the mast is always in the same place inside the tube ... winter/summer/dry/wet.

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 Post subject: Re: Shrinkage
PostPosted: Sat Jun 15, 2013 3:24 am 
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Location: Central Coast NSW Australia
Yakaholic wrote:
My sails fit the canvas bags when bag is wet or at least damp. Let the bag sit all day in the sun or in a hot car and it gets bone dry and then the sail no longer fits. The shrinkage is a couple of inches and caused by the fabric shrinking. Like putting a wet sweater in a dryer. Even hair will change length with humidity I believe that is how some hygrometers measure humidity.


I'm with Yakaholic on this! 8)


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 Post subject: Re: Shrinkage
PostPosted: Sat Jun 15, 2013 4:31 am 
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My bag never gets wet. The mast fits when the bag is bone dry. By the time I get to the water, and the bag is still dry, the end of the mast is sticking out of the bag. It stays that way until I return and then the next day it has returned to original length.

Funny thing - the bag for my AI mast doesn't seem to do this.


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 Post subject: Re: Shrinkage
PostPosted: Sun Jun 16, 2013 9:36 pm 
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Joined: Thu Oct 04, 2012 5:41 pm
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Location: Aussie living in San Diego, CA
OK so yesterday I went out sailing at the Hobie cat regatta (yes we got invited as special guests by the association) and when packing up I noticed the usual "mast won't fit in the bag" syndrome. So I took a few minutes to make it fit and in the process I noticed that I could stretch the Hobie sail bag about an inch or more to close the bag around the mast. I concluded that the bag must stretch around the mast and when we take the mast out the bag shrinks to its normal size just like a bungee. 2" stretch is only 1% and I would think that is not unrealistic amount of stretching. Although this stretching does not explain Tom's bag which grows longer when the mast is not inside :?

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