What type of seam do tent manufacturers use?
Apr 9, 2012 at 10:50 am #1865326Kevin BeedenBPL Member
I'm not sure if there's actually much difference in seam loading between a mock and true flat-felled seam. After all, in both seams, there's still a line of stitches between the seam and the main body of the fabric. When loaded, this line of stitches will open up. I think the benefit of a true felled seam is that the other layers of fabric in the seam hold the stitches more perpendicular to the fabric, which I think reduces the chances of seam ripping, either fabric or thread.Apr 9, 2012 at 12:34 pm #1865374Harald HopeMember
@hhopeLocale: East Bay
Samuel, beautiful work, do you have a thread here with pics on that tent, I don't want to pull this topic off topic, but I'd love to see a lot of closeups of your work there on the green tent, especially seams and key joints and connections, inside and out. I'm not to the point of being able to make a tent, but I'd love to see what others have done, especially with such an excellent outcome.
Roger, thanks for the input, I'll still try the hemmer presser foot on silnyon to see how it works, slipping, as indicated above, would be what I'd expect though, but if I have to pin to do it well, that's fine, I'll do it, it's just the lazy hacker in me wondering where I can avoid unnecessary work in the end, heh. But necessary stuff, no problem.
Peter, thanks for confirming what struck me as kind of obvious, if you pull at basically one single layer, which is a standard edge of a faux felled seam, not, I realized reading your comments, even two layers, that's totally different than having one seam press down, creating friction of the top layer, onto the next layer, onto the rest of the layer. I know that friction holds are radically stronger than the actual connector alone, thread, screws, etc, from experience, so conceptually that makes total sense. Excellent argument for making true felled seams on especially a tent.
I've had the same experiences with ironing in the folds, but I haven't been able to test durability, ie, if I damaged the silnylon by ironing it, but good point re making sure to only iron the actual fold, I was sloppy in that regard.
One thing I've started to see re myog is that I can do stuff with sewing, by not worrying about speed or efficiency, in terms of stronger seams that take a long time to sew, so it's possible to really exceed standard production techniques in some cases, since my time is free for me, give or take.Apr 9, 2012 at 3:16 pm #1865452
> re myog is that I can do stuff with sewing, by not worrying about speed or
> efficiency, in terms of stronger seams that take a long time to sew, so it's possible
> to really exceed standard production techniques in some cases,
Absolutely true. Commercial pack seams are usually a single line of stitching: mine have a faux felled seam and are taped as well. My way would not be commercial, but the result is MUCH better.
In practice I avoid the felled seam on the critical parts of my tents by using different designs.
CheersApr 9, 2012 at 3:18 pm #1865455
"In practice I avoid the felled seam on the critical parts of my tents by using different designs."
Could you elaborate a bit? I'd love to see some alternate techniques for joining strength critical panels of fabric…
BMApr 9, 2012 at 7:01 pm #1865542Harald HopeMember
@hhopeLocale: East Bay
I second that, can you show some pictures of your tent seams and other things Roger, would be interesting to see how you solved the problems.
I know I realized when I was ripping apart my first pack project due to design errors, it hit me, man, this thing would never have failed on the seams. Materials, maybe, but not the seams.Apr 9, 2012 at 9:34 pm #1865592Sam FarringtonBPL Member
@scfhomeLocale: Chocorua NH, USA
If the iron is hot enough, it will go through the silnylon like butter. What a mess. The temp needs to be just hot enough to make a good crease without melting.
Even at that temp, however, if the iron slips over the fold and onto the single layer of fabric, you can have damage to the fabric which is clearly visible. It starts to shrink and harden. Not what you want in a tent canopy.
Thanks for comments. But mea culpa. I was so focused on providing evidence that the ironed crease technique works, that I neglected to mention that the project was a fly, not an entire tent. The tent was a friend's Hubba. Phase 1 was making carbon poles, which dropped 5-6 ounces. Phase 2 was the silnylon fly, which dropped another 5-6 ounces. Phase 3 was to be a silnylon or 1.26 oz Cuben floor, but we broke up. Since you asked, here is the only other photo taken:
Here is a diagram of the mock or faux felled seam:
Please note where the stitch holes will be exposed in one layer of fabric when tention is applied. Yes, you can remove the first seam, and stitch #3 where indicated, but you will still be left with the bloody exposed holes.
I wonder what nifty ideas Roger will have for us. Have tried to come up with simpler methods, but none worked as well as the lap for flat felled seam – with the exception of the bonding approach for Cuben that I mentioned. That could be used with silnylon and sil glue also, I suppose. Haven't tried it, because for sil to sil, I have found that bonding reduces the elasticity of the fabric in the seam, creating wrinkles ad nauseam on the canopy. This doesn't happen if an unbonded seam is sewn, and then carefully sealed with a thin coat of sealer.Apr 10, 2012 at 12:36 am #1865622
Hi Magnus and Harald and Sam
This is my winter tent – featured in When Things Go Wrong. It has to be strong.
The panels are small so there is basically no need for an unsupported high-strength seam. Yes, there is a seam along the ridge, but that is really not under any significant tension. Where the tension does happen is at the pole seams. A lot of engineering went into those seams. This is a diagrammatic cross-section.
The black circle is a carbon fibre tent pole.
The yellow at the bottom is the inner tent, held up by the green and teal bits of Velcro or hook&loop tape. Yes, it is strong in shear like that.
The dark blue lines are of course stitching.
The top red loop is the pole sleeve in the fly. I have little patience with designs which have the fly free-floating, not sleeved into the fly. You can see how the pole sleeve goes right through the fly to anchor the inner tent – which incidentally includes the bathtub groundsheet. The connection is important, as our weight helps keep the tent down, although the guy ropes are always sufficient.
The two red bit at the sides are the fly. They have no less than three lines of stitching. These are important.
The lowest (pale blue) is the first one: it holds the pole sleeve folded and serves as a guide for the next two. It uses light Rasant 120 thread and long stitches.
The middle one (medium blue) attaches the bits of the fly to the pole sleeve. When sewing this all the fabric edges line up together (by design), the layers are pinned in the seam zone, and this line of stitching goes next to the first one. It too uses Rasant 120 thread and long stitches.
The top line of stitching is the strength line. I fold each of the edges of the fly back for reinforcement so I am sewing through a double layer of silnylon at each side. I use shorter stitches and stronger Rasant 75 thread, and the line of stitching is again next to the previous ones.
I run a small bead of sealant along the corners on the outside of course. But with all the layers and the tight sewing, not much water gets through without the sealant.
Is this complex? Does it take me some time to do? Yes. But the tent can take a violent 100 kph storm all night without flinching. Do I care about the extra sewing time? :-)
Is the design really meant to handle pole sleeves? Yes. Would you use it for a tarp ridge? No.
Hope this helps
PS: why did I camp in such an open exposed position? Well, at the time in the evening I was having trouble seeing my feet in the fog …Apr 10, 2012 at 2:02 am #1865625Ivo VanmontfortBPL Member
It is posible to glue sil to sil without wrinkles
if you use a catcut.
My copy trailstar is a combination of bonding and sew technics.
I used a large (240 cm) pu foam plate and … yes, pins.
Van lijmen/kleven silnylon panden
After this step you can sew the first seam without using pins.
If there is silicone on the wrong side of the seam, then tear it open up to the seam.
Then, glue again and sew the second seam.
In the corners you sometimes have to skip using glue.
Otherwise, the seams are too thick
Apr 10, 2012 at 10:24 am #1865736
Roger- that is some beautiful work and some seriously bomber sewing…
Ivo- what are you using to glue the silnylon? What kind of work space do you need to do the job? How long does it need to stay undisturbed until the glue sets up?
BMApr 10, 2012 at 12:25 pm #1865779Ivo VanmontfortBPL Member
I used pure silicone (eg aquarium silicone sealant).
I have no Permatex flowable silicone.
I think that would be an advantage.
I get a nice flat, strong seam but the shelter weighs about 3 oz more
than the original.
The tie-outs are glued to.
Must say that the apex is too heavily executed.
I gave me about 3 to 4 minutes to distribute the glue
with a putty knife.
Waited a while to let the silnylon relaxing and pressed the layers
together with a wooden bar.
Took a cup of coffee and began to sew.
Give it five minutes.
I protected the foam with brown plastic tape.
Residues hardened silicone can be removed easily.
Working on the floor is not convenient.
A table is useful.
Is it not long enough, support the foam plate with a few long wooden bars.
link with extra photo's of the makingApr 10, 2012 at 4:40 pm #1865891
Sorry! I'm a little slow on the uptake sometimes and always bad at remembering names. You replied and explained this process to me on my post about forming the peak of a 'mid shelter… But thanks again for taking the time to explain it again…
I'm afraid of doing a big project like that. It seems it could be really easy to make a mistake and have the whole mess get out of control and ruin the project. Maybe I'll try in on a smaller piece of fabric and see how it goes. It just seams (pun) to me that you would need to be pretty neat and precise in the application of the silicone to get an even, consistent seam…
BMApr 10, 2012 at 7:33 pm #1865958
I did try glue&sew, but before the silicone sealant set completely. The result was NOT pretty: the silicone adhesive stuck to the eye of the needle and the thread, and the whole lot ended up a serious mess very quickly!
Once the sealant has set it would be OK, but you would need to make sure the layer was very thin. I had problems keeping everything aligned exactly too.
CheersApr 10, 2012 at 8:50 pm #1865982Sam FarringtonBPL Member
@scfhomeLocale: Chocorua NH, USA
Thanks for your seam construction post. It is another one of yours that I will copy and refer back to often.
The shelter looks gorgeous in the photo, but in the close up, there is some puckering along the seams. With careful sewing at not too much tension and sealing afterward, there can be almost no puckering, which may or may not translate to wrinkles. The time I tried bonding, just a little puckering on the seam significantly reduced the tautness of the canopy. Sorry for being such a fussbudget.
The clouds finally opened, and it dawned that maybe that aquarium sealant, unlike silicone glue with a hardener in it, will allow a silnylon seam to stretch along with the fabric. Will have to try some. Thanks. Edited on 4/12/12Jun 8, 2021 at 7:26 am #3717692
Timothy Clarke PMed me:
“Hi Jerry, I have followed the discussion on ‘What type of tent seam do manufacturers use?’
The thread just seemed to run out (sorry about the double pun). I appreciated your comment on the third row of easy stitching. It seemed to be ignored. I think your idea is excellent and if that extra line of stitches is run very close to the first line (that does not go through all layers) it must be as good as a true felled seam that can be done by a double needle machine.
I have been locked out somehow by BPL, for years, from commenting on anything (including my own original articles), so I thought that I would use a PM to let you know that I appreciated your comment. I also would like the thread started again as I think the Mock Felled Seam got poorly define by the sketch from the start. In contrast, ISO 4916 2.04.06 show it quite clearly in:
If you think about toroughly the ‘stitched once’ layer is really held by two rows of stitches, but the fabric is just bent around over those stitches and is a quite reasonable second line to add support for the first line of through stitches. Your third line of easy stitches would make it stronger than the true felled seam.
Avoiding the pull holes around the stitches is all about pulling the seam tight while doing the second line of stitches. I don’t see how ironing silnylon will substitute for this tight pulling, or your third line.
Lastly, I sew through silicone rubber impregnated silnylon with no problems (it is easier to sew after silicone rubberising). For such a stretchy thin layer of polymer can’t see how it could spoil the looks of a seam.
I hope the discussion can be continued and that I can find some way to contribute. A magnified hem section as in ISO would be a good start. Add a tight rational description of the primary and secondary loading force lines for the stitches for each piece of fabric, with and without a third line would make a good start. “Bugger all difference”Jun 8, 2021 at 7:36 am #3717694
Yeah, I don’t see any huge advantage to a true flat felled seam over a faux flat felled seam if you do a third row of stitches.
Except time. If you were doing this as a business it would be better to do the entire seam in one pass.
I’ve been using mara 70 thread lately which is a little thicker than regular Gutterman thread. And I usually don’t bother to do an extra row of stitches. Except in high stress placesJun 9, 2021 at 7:42 am #3717881
Timothy Clarke can not submit replies even though he’s a member
Screenshot of what it’s supposed to look likeJun 10, 2021 at 11:17 am #3718012Diane “Piper” SoiniBPL Member
@sbhikesLocale: Santa Barbara
I recently made a RayWay shell pants kit and the way they had you do the seams was to pin the fabric together and sew, then sew another line right on top of the first, then fold the excess over and sew flat, then top-stitch another line in between. That was a lot of sewing. They called it a double-lapped flat-felled seam. There was no way I was going to sew that many times down the same seams just for shell pants.Jun 10, 2021 at 1:09 pm #3718043
yeah, I’ve moved away some from doing extra rows of stitches because it takes so long
although, on the other hand, the first row of stitches takes longer because you have to carefully line up the two pieces of fabric. It doesn’t take as long to run a second or third row of stitches on a seam that’s already sewn together.Jun 11, 2021 at 9:54 am #3718111
Timothy Clarke’s response that he’s not able to post so I’ll just copy paste it:
Hi Jerry, I am quite excited to hear your thinking on seams. I am heading in the same direction as you describe (using a multi-folded straight grain to stabilize the seams formed from bias cut fabric. I don’t know if it is wise to feel so good about someone else agreeing with oneself. It could be the blind leading the blind. Nevertheless, it is heartening to hear the ideas expressed by you. It means that I know that you will eventually understand what I am on about.
My most recent tents have addressed the bias grain stretch issue by wrapping the bias within the straight for the first line of stitching.
The process described briefly within in:
Yes, I now agree with you that a third line of stitches would be easy to do and add to the strength, even though I never had any leakage or failures over many years of use.
My cutting and sewing are tricky and tedious when compared with yours. So I am keen to do less cutting and less seaming where possible and make it as simple as possible without compromising strength, leak resistance and a taut tent shape. I don’t even want to cut cat-curves, never have, hope I never will as that is just giving in to gravity!
Do you have a sketch or photo of ’2 – I put a strip along each of the 4 ridges.’
Independently, in my mind and sketches, I was thinking of a 2 time folding, giving 4 layers and incorporating it into the lay flat seam. Could go to 6 if required
I aim to make seams that are about 7mm wide. I would start with a 28mm wide strip and fold it in two and glue it together with very thin silicone rubber, just to make it easy to manage in the next step.
Next with the neat rounded edge facing left I would introduce the two bias-cut tent panel edges (from the left) and fold the strip, in half, around those edges and pin them together or even better glue them together at the starting point. The bias edges will be covered by the tape and the tapes two raw edges will eventually be covered by the ????? flat seam when the seam is laid flat for the second row of stitches. It will have all the features of a Mock Felled Seam, including the ’Gerry’s Third Line’. However, it will also have ’Tims and Gerry’s straight grain strength’ embedded within the seam. Am I making sense?
I have ordered some Grosgrain seam tape from China for the seams, but I would much prefer the multi-folded tent fabric to provide that strength with softness. Your success is encouraging. I have even considered adding glued 100lb Dyneema fishing line into the folded and glued strip!
If the tensile strip needs to be stronger, then 6 or more layers can be used.
I don’t know if you agree with me, but I would not be surprised if you do. I find the multiple layers of sewn thin fabric sew nicely and the thickness gives the seam resilience. I think the resilience comes from the stitches being more able to stretch along the seam, almost like zig-zag stitches do.
Later, I will send a photo of a crude sketch to supplement my inadequate words describing my proposed seam. I am certain that our thoughts are running somewhat similarly, and we are both very open to new ideas without resorting to defensive dogma.
I also have posted on a simple way of linking the tensile forces of the tent panels and particularly the seams to a simple tubular apex hem that easily allows the use of almost any tent pole or dare I say no tent pole at all. There is a detailed post on the subject, and it makes cutting and sewing easy and tolerant of errors and ends up with infinite strength, uses only tent fabric and looks great even for a crappy sewer like me:
A load bearing hem for the apex of pyramid tents
Look at any of my tent tops and they look good weather a thick tree branch or a skinny pole or no pole at all.
Also, my design differed from yours with a little wall. It means a smaller footprint, make the single tent pitch high as a palace or down low for storm survival as in the above photos. It adds sewing complexity, but I have a plan to eliminate this.
With your tent layout for cutting the equal triangular panels, why did you cut the 8 when you could have cut 3 at twice the size plus 2 halves (from each end of the stip) that would join at the zipper?
This would nearly halve the cutting and stitching.
I have been having conversations with a Candian who has made a wonderful tent with only three panels cut, sewn and taped on this basis, These taped bias seams form the tent’s structural stays to the ground. The straight grain section of each panel have secondary ridges formed in them and extra fabric sewn on to reach the ground. (Similar to your special cutting to maintain ground contact but on steroids.) A very nice tent, but you and I like the efficiency of a square tent. However, I think his design has some lessons for our square tents and his design can easily be scaled up or down. More on that later.
I sent the email Re: my access to reply/commenting to BPL, as you suggested. I got a robotic nice reply indicating that a real response would follow (as usual). Not holding my breath waiting!
I think I have ideas to contribute to forum discussions and as far as I can tell I am constructive and polite even when I have silly comments from fools or worse.
Do you think a group of forum participants such as Roger and yourself and some other respected members could partition for this action on my behalf? I promise to behave myself.
TimJun 11, 2021 at 10:10 am #3718120
a couple related topics
Hmmm… that doesn’t explain it real good. The pictures don’t show it very good. I take a 3 inch strip of fabric longer than the ridge seam. Fold in half. Fold over the raw edge 1/3. Fold over the other side so the raw edge is hidden. Sew along one side to sew it together. I sewed along the other side just for symmetry. Them sew that to the ridge with one row of stitches.
Or, you could just use grosgrain. That’s pretty stiff.
I think a strip is better because you can sew it all along the ridge. A dyneema line could be attached at the top and bottom, but it seems like it would be better for it to be attached to the ridge seam all along its length.Jun 11, 2021 at 10:23 am #3718123
the reason there are two panels on each side is the width of the fabric
the tent is 9 feet wide = 108 inches. The fabric is about 58 inches wide.
But, having a flat felled seam down the middle is a good thing regardless. You can attach a tent stake loop to it and it won’t rip. I had a tent stake loop rip out when it was attached in the middle where there wasn’t a flat felled seam. Of course one could put reinforcing fabric, but sewing tent stake loop to a flat felled seam works so good.
I started doing the third row of stitches after a seam ripped a couple times. But it was with the Gutterman thread you can get at fabric stores. The Mara 70 is stronger so the third seam isn’t normally needed. I made a pack recently and used a third row of stitches even though I was using Mara 70, just to make sure. So easy to do this, may as well. Tent has so many long seams it would be more of a pain to do third row.
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