Completing the Mock Felled Seam after hot hot knife cutting/welding of the components together prior to sewing the seam. "The sewing of the seam and tab back-stitching can be completed with the work staying under the sewing machine pressure foot."
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Hot knife welding as preparation for easy tent seam sewing

Hot knife welding is a simple preparation for easy seam sewing for DIY backpacking tents.

I have a more detailed post on hot knife cutting and welding for tent making, but the welding function may get lost in all the other details. Consequently, I thought a short dedicated post would be valuable to describe and focus on the welding function of the hot knife as it relates to the easy preparation of tent Mock Felled Seam (sic Lay Flat Seams) for backpacking tents.

Hot welder cutters, are we are spoilt with choices?

For far too many years I have used scissors to cut fabric to make my pyramid tents. “I put off getting a hot knife for far too long.” There are so many similar hot knife cutters available online. Many are designed for use with 110V so my choice was more limited because I needed a 240V model with an Australian standard plug. There are so many blades to choose from. I chose the KS Eagle Hot Cutter with the ‘arc-style’ blade. The blade shown has proven to be very versatile and as is my usual wont, I have modified it a little to make the blade blunter.

A hot cutting knife with fast response heating trigger and fully adjustable power setting. "A joy to use!"
A hot welder cutting knife with a fast response heating trigger and fully adjustable power setting. “A joy to use!”

Hot knife welding while cutting instead of pinning

I was delighted with the easy cutting function of the hot knife. That is described in the ‘longer post‘. While using the hot knife for cutting, I discovered to my delight that if two or more pieces of fabric (many synthetic fabrics) were laid on top of one another and cut together (or finely trimmed), they would end up neatly welded together. I immediately recognised that such welding made the fabric layers behave as one piece of fabric when starting to sew Mock Felled Seams (or similar). Furthermore, if a fabric with a bias cut edge was to be sewn to a straight grain edge it made this otherwise difficult sewing easy.

“No pins, no bias grain stretching, creeping and easing of the unwanted length. Just the easiest Mock Felled Seam that a crap sewer could sew. Just one little difference between the seam done this way is that it has an extra layer of straight grain within the rolled seam and this just makes it a little stronger and plumper. “

Tie out tab tack hot welding while hot cutting

I have developed a method of integrating tie out tabs into my tent seams before the sewing is commenced. I did this initially by RTV silicone rubber glueing while I also glue tacked the seam (instead of pinning or hot welding). When using the hot welder to cut and weld the fabric edges together, the tie out tabs can also be tack welded in place in readiness for simple sewing them into the seam during the sewing of the two lines of seam stitches.

This was to be a short post, so I will let the photos below wet your interest.

Two layers of fabric have been placed together back-face to back-face with a bias cut edge on top and a straight-cut edge on the bottom where they have been hot cut/welded together with a hot knife cutter. This leaves the two edges conveniently welded together so that the subsequent seam sewing is easy. A tie out tab has also been welded to the edges in preparation for embedding or integrating it with the Mock Felled Seam. This preparation eliminates the tendency of stretch creep of the edges (the bias cut edge in particular).If there is a bias cut edge, then it should be arranged to be on the top so that when the fabric is rolled to form the seam the stretchy bias edge will be wrapped in straight grain fabric and will have no contact with the feed dogs or the pressure foot. "The process means that all the preparation for the seam and tabs can be done calmly away from the sewing machine and that portion of the tent is virtually complete once the two lines of stitching are done. Also, if each tent panel is successively added in this way, only a one tent panel width of fabric must be passed under the sewing machine bridge while sewing the second line of stitches."
Two layers of fabric have been placed together back-face to back-face with a bias cut edge on top and a straight-cut edge on the bottom where they have been hot cut/welded together with a hot knife cutter. This leaves the two edges conveniently welded together so that the subsequent seam sewing is easy. A tie out tab has also been welded to the edges in preparation for embedding or integrating it with the Mock Felled Seam. This preparation eliminates the tendency of stretch creep of the edges (the bias cut edge in particular). If there is a bias cut edge, then it should be arranged to be on the top so that when the fabric is rolled to form the seam the stretchy bias edge will be wrapped in straight grain fabric and will have no contact with the feed dogs or the pressure foot. “The process means that all the preparation for the seam and tabs can be done calmly away from the sewing machine and that portion of the tent is virtually complete once the two lines of stitching are done. Also, if each tent panel is successively added in this way, only a one tent panel width of fabric must be passed under the sewing machine bridge while sewing the second line of stitches.”
The hot cut/welded fabric edges(and tab) have been easily rolled and sewn down with the first line of stitches that will form the Mock Felled Seam. "The process means that a 'crap sewer like' me can just focus on the simple rolling and straight sewing, . No pins, no forgetting tabs or putting them in the wrong place, or accidentally sewing into some other part of the tent. It is so easy that extra tabs can be added if I am unsure about their optimum location. Also, I leave the back stitching for extra strength for the tabs to be done during the second line of stitches. This means that the seam and the tabs can be sewn without needing to remove the work from under the sewing machine pressure foot!
The hot cut/welded fabric edges(and tab) have been easily rolled and sewn down with the first line of stitches that will form the Mock Felled Seam. “The process means that a ‘crap sewer like’ me can just focus on the simple rolling and straight sewing. No pins, no forgetting tabs or putting them in the wrong place, or accidentally sewing into some other part of the tent. It is so easy that extra tabs can be added if I am unsure about their optimum location. Also, I leave the backstitching for extra strength for the tabs to be done during the second line of stitches. This means that the seam and the tabs can be sewn without needing to remove the work from under the sewing machine pressure foot!
Completing the Mock Felled Seam after hot hot knife cutting/welding of the components together prior to sewing the seam. "The sewing of the seam and tab back-stitching can be completed with the work staying under the sewing machine pressure foot."
Completing the Mock Felled Seam after hot knife cutting/welding of the components together prior to sewing the seam. “The sewing of the seam and tab back-stitching can be completed with the work staying under the sewing machine pressure foot.”

You may like to look at the detailed post to see many more uses for hot welding cutting.

Tim

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