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Forum LockedDodger and sewing shrinkage

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Sue2 View Drop Down
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    Posted: 14 March 2016 at 9:52am
Okay, I have watched the Sailrite "Build your own Dodger" DVD and am ready to start my dodger, but have one significant fear:
The pattern is made with durascrim that does not stretch, and is cut to exactly the size I need the finished dodger to be.  However, based on experience, when sewing Sunbrella, especially long lengths of it, the stitching causes the fabric to "shrink."  I am afraid of cutting large pieces of expensive Sunbrella and vinyl window, only to find out that my finished dodger is an inch short.  That would be a tremendous waste of time and money.  What can I do to prevent this?

-Sue
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MattGrant View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MattGrant Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2016 at 10:00am
I would agree with you if this were something like a long mainsail cover where the needle pucker would cause a potential issue. But most dodgers are small enough that any shrinkage will go unnoticed and in fact will help to create a nice tight top.

Make sure you use a 6 to 8 mm stitch length and do not over tension the stitch.
Best Regards,
Matt Grant
Sailrite
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Tejas View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tejas Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2016 at 5:11pm
Here's a link to a pdf on the prevention of seam pucker. Briefly, the document describes three causes and solutions:
1. Tension pucker
2. Feed pucker
3. Displacement pucker

The link is to a cached file. I've tested the link, but if it doesn't work for you send me a PM and I'll send a copy of the pdf.

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwjTtdKDicHLAhVGRCYKHT4iDiYQFggcMAA&url=http%3A%2F%2Fwww.amann.pl%2Fpobierz%2Fprzemyslowe-nici-szwalnicze.html%3Ftx_abdownloads_pi1%255Baction%255D%3Dgetviewclickeddownload%26tx_abdownloads_pi1%255Buid%255D%3D265%26no_cache%3D1&usg=AFQjCNFeFwt_nN2Mj32Uvv6nCuVY3kM7eQ

Edited by Tejas - 14 March 2016 at 5:12pm
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Tejas View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tejas Quote  Post ReplyReply Direct Link To This Post Posted: 15 March 2016 at 8:00am
Here is another link on managing pucker. I'd forgotten about it yesterday.

http://www.coatsindustrial.com/en/information-hub/apparel-expertise/seam-puckering

Here's a direct link to the cached pdf mentioned yesterday.

http://www.amefird.com/wp-content/uploads/2010/01/Minimizing-Seam-Puckering-2-5-10.pdf

The Coats article mentions feed pucker. I'm not sure, but I think that a cause of feed pucker could be a mismatch of feed dog timing with the needle -- that is the feed dog moving the material while the needle is still in the fabric. I think that a way to test for this problem would be to unthread the needle and using the hand wheel, "sew" a piece of stiff paper for about an inch. The needle holes should be the shape of the cross section of the needle -- slightly oval. If the needle holes are longer, the feed dog might be moving the material while the needle is still in the material.

BTW, doing the same test above but "sewing" in reverse should be a test that feed in reverse is correct if the reverse needle holes match the forward needle holes.

Edited by Tejas - 15 March 2016 at 8:42am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sue2 Quote  Post ReplyReply Direct Link To This Post Posted: 15 March 2016 at 3:37pm
Thanks, Matt, for the advice.  I tend to use a smaller stitch, so I will be sure to adjust to using a longer stitch.  The biggest issue I have is the upper tension on my LSZ-1 seems to be dependent on whether the thread is pulling from the upper or lower end of the spool.  Makes no sense, I know, but when I tug on bobbin and upper threads to check tension, sometimes the upper seems to "stick" and I see it is coming off the spool at a bottom end wrap.

Thank you, Tejas, for some very interesting articles! I plan to read up and check my machine before sewing.  The top panel of the dodger is over 10 feet long, and shrinkage can add up. It's an art, an I hope to master it someday.

-Sue
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tejas Quote  Post ReplyReply Direct Link To This Post Posted: 15 March 2016 at 6:00pm
Originally posted by Sue2 Sue2 wrote:

The top panel of the dodger is over 10 feet long, and shrinkage can add up.


Sue, I've also had problems with pucker, especially sewing binding, webbing or Boat Blanket. That's why I searched for articles on pucker. To better understand the impact with my machine, I cut several 4" x 60" pieces of material, sewed seams, hems, webbing and binding, and measured the shrinkage.

For example with 6 mm stitch length:

Hem -- no pucker
Binding over raw edge -- 1" loss
Webbing over raw edge -- .5" loss
Binding webbing sewed over raw edge -- 1.25" loss

Changing the stitch to 8 mm resulted in less pucker.
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Sue2 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sue2 Quote  Post ReplyReply Direct Link To This Post Posted: 20 March 2016 at 10:00am
Ah, boat blanket! This may explain why the fender covers I cut way oversize just barely fit when I am done. Boat blanket is so stiff, it is hard to see the pucker in a fender cover shape.

-Sue
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tejas Quote  Post ReplyReply Direct Link To This Post Posted: 20 March 2016 at 10:18am
The pucker experience with boat blanket was binding the edges of a companionway cover made with Sunbrella on top and and boat blanket on the underside for insulation. The resulting pucker left insufficient length to attach snaps that matched the male studs already attached to the boat. Since the cover was just big enough for the companionway, I ended up sewing binding to the underside with snaps on the ends to span the distance.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sue2 Quote  Post ReplyReply Direct Link To This Post Posted: 20 March 2016 at 2:31pm
Well, darn it. I decided to practice on a sail cover I am making.  Sewing a hem along the bottom edge (145" long), I lost 2" on one piece, and 1.5" on the other.  This is using 6mm stitch (apparently the longest a LSZ-1 machine will do). The tension is nicely balanced top and bobbin, but it's still puckering.  When I lay out one half of the sail cover, the bottom edge is now a curve, not straight.  It's downright maddening.

-Sue
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Tejas View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tejas Quote  Post ReplyReply Direct Link To This Post Posted: 20 March 2016 at 4:14pm
I did worse sewing a zipper on a jib cover, about 480", and the zipper half on one side ended up much shorter than on the other side, even though I'd used seam tape. Unpicking and resewing with 12' apart match marks on both sides solved the problem.
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