Cat cut tarp ridgeline wrinkles

Felt tip marker to show how to align, then pins, pins and more pins in the hem region. Then sew under tension.

Cheers

Thanks Roger! You rock!

Good idea from Roger, a little different take on this:

Use whatever marker works – felt pen or a “dressmaker’s marking pencil” which is chalk I believe, from the fabric store

Lay out a line on both pieces of fabric where you want the first row of stitches.  Be meticulous.  I like to tape the 4 corners and pull to take out slack but don’t stretch it.  Measure twice…

I prefer hand stitches to pins, but that’s somewhat arbitrary.  Maybe every 2 feet or so.

When you’re sewing, make sure that first row of stitches goes through the middle of the line on both pieces of fabric.  As I feed the fabric through, I’ll hold the next hand stitch, pull, and apply just a bit of pressure.  The two pieces of fabric tend to slip relative to each other so when you get to the next hand stitch, they’re no longer aligned.  Practice.  When you get the technique correct, the two pieces of fabric will still be aligned at each hand stitch.

When you do the second or third row of stitches to complete the flat felled seam it’s easy to keep everything aligned.

I think those wrinkles are just aesthetic, won’t make any functional difference.

This is all amateur sewing technique.  Professionals want to quickly do the seam and don’t have time to do all this fiddling.  Maybe use a walking foot machine or something.  I vaguely remember my mom sewing patterns and there are these little triangles cut out on the fabric and the triangles on the two pieces of fabric are supposed to line up.

A few thoughts:

MLD uses a triple stitch in that photo.  Maybe running one more seam down the center of yours would reduce wrinkling?

If you just make your seam narrower, there will be less area for wrinkles to form in so they will be less prominent.  After making the initial seam, trim the free edges shorter, so you don’t need to create so tall a flap with the second seam to trap them.

A felled French seam lands off center.  The second stitch in the process is the one that defines the geometry because it’s where the two panels part.  The third stitch, the one that holds the flap down, lands to the side of the true ridge line. If you center your guy points between the two stitches, you’re actually off center.

Maybe every 2 feet or so.
I am paranoid. I use a pin every 2 inches.
Yes, it makes for slow sewing, but the results are worth it.

Cheers

Hey all, thanks for the very thoughtful responses. I went ahead and made another. For the ridge line seam I did the first two stitch lines as normal. Before sewing the third I applied a thinned silicone seam sealer mix and bonded the flap down along the ridge line. Let it sit for a few hours with cardboard on top weighted down with books. I then ran it through the sewing machine. I think it actually came out great! I took the picture while it is set up for seam sealing (with a too thin sealant).

Having sewed a number of shelters over the past 45 years, in various fabrics, with seams ranging from very nice to wrinkly as hell, and having used those shelters in all sorts of weather, I’ve had poles break, stakes pull out of the ground, have ripped stake loops out while digging out of the ice, but I have never experienced a seam failure. So while I try for a nice looking seam I would not sweat it.

Thanks Paul! That is very reassuring to hear.

In addition to basting stitches or pins…   For these slippery silicone fabrics (where I am trying hard to keep things aligned)  I have often “glued” the edges together before sewing.  While a thin smear of regular silicone will work,  it takes a long time to set up.  I now use  Permatex Flowable Silicone Windshield and Glass Sealer (1.5 oz tube).  This formula sets up pretty quick… Maybe two hours or less.  I daub on small spots (or a thin line) and use spring clips to hold in place until it sets up enough to handle.  I have occasionally constructed an entire seam this way and did the sewing afterwards.  I’ve never had a problem sewing through the sealer.

+1 to Paul – it’s just aesthetic

gluing, weighting down, waiting to cure takes too long, not needed, in my opinion

Please understand the wrinkles can not be avoided given it’s the physical properties of the fabric, give this is a tapered tarp with felled seam and the ridge line is neither 0/90 nor 45 degrees….