Diffrent seams to make tarp

i think the french seam is the easiest way to go for ridge lines. Just sew the flap down and it will look like a flat felled seam.

-Tim

Do you mean i sew 3 times?
Normal french seam is two times but if i fold it so there is 3 sewing for ridgeline.
So this my option 2. i sew only two times.

Do i miss something?

I think your last message seam #2 is what Roger Caffin suggests for silnylon or other fabric that won't fray and you don't care how the inside looks (raw edge showing).

I haven't done that exact seam but it appears much easier than the classic flat felled seams. (My felled seam experience was sewing two double walled pyramid tents about 25 years ago.)

The important thing when sewing tent seams is to keep the fabric tight so the two stitching lines will share the load. It's good to roll the excess fabric up so you don't get lost. I found that masking tape worked well to keep the excess out rolled and out of the way. It's also good to have a helper watching to be sure that stray fabric doesn't sneak under the parts you're trying to sew.

And buy a good seam ripper.

Timo,
Yes, 3 lines of stitches in the French seam as in drawing #1 in you last post. The first line of stitches help secure and hide the raw edges, the second and third lines of stiches share the shear load.

Drawing #2 in your last post also has two lines of stiches to share the shear load, so it should be as strong as #1 provided the raw edges don’t fray into the stich line.

A flat felled seam isn’t much more difficult than #2. Here are some pictures of a flat felled ridge seam.
Hope this helps,
Lance

yeah, pic #1 is what i mean

-Tim

Recently, I started to use the seam Roger Caffin suggests for tents. It doesn't have the neatest look, but it is stronger than all the seams you show here. It is so strong because the loaded line of sewing is padded by the extra layer at each side, and ripping through two layers is not as easy as through one (providing the thread is stronger than the fabrics).

Timo, I made my 2,70 m Ridgeline with a felled seam, and its fine if you prepare it properly – use needles to put the silnylon together, roll excess fabric up and locate it with a clothes-peg, and off you go. Check the video I posted on how to make a felled seam in the thread in this forum if you want visual instructions.

I would prolly use Roger's seam the next time I would make a tarp (so after this one is finished =), it seams very easy and as its from Roger it certainly is bombproof (if made well!).

I am working towards a cuben tarp tent. I plan on glueing the main seams with Aquaseal. Because of its poor peel strength the seams will be sewed with long stiches too.
If I was just glueing straight seams I would just overlay the 2 pieces by the glue allowance. Glue and press. If the sewing was needed I would add it afterwards. This does not work so well with a curved seam such as a catenary ridge. Nothing is flat while you are trying to glue and press.
I thought of sewing the same simple overlap seam by sewing one side, close to one edge, flapping back the large flap adding glue, pressing until set, then sewing the other line of stitching. The little bit without glue to the other side of the first stitching could be glued while seam sealing.
Another possiblity would be to first sew like Timo's first post in this thread line 1 picture 1 but with the left hand sewing margin very small and the right the full glue margin. (Sorry I am not good with these graphics) This would be easy even with a catenary as you are sewing flat. Now open out the fabrics and glue and press until set. Finally sew the other line of stitching.

Anyone who has sewed and glued cuben which way did you do it?

> Recently, I started to use the seam Roger Caffin suggests for tents.

Jan,

Do you know where Roger recommended that seam for tents?

I've been researching various seams and would like to see what else Roger had to say (assuming there's more to read).

Thanks,

Steve

Hi all, I know this is slightly off topic as I'm sewing canvas and not nylon, but what are your thoughts on the following;

This idea should have the following attibutes
The edges are hidden so they can not unravel (like french or flat felled seam)
Two lines of sewing each share the same amount of force (unlike french seam or rogers seam)
Doable without use of pins or clamps and with simple folding (as opposed to felled seam)

I can't believe I'm the first with this idea so I'm wondering why no one else does this

I don't see the advantage over a regular flat felled seam?

With a flat felled seam you have two rows of stitches carrying the load.

You don't have to pin – there's a ruler on the sewing machine so you can position the edges of the fabric on, say, the 1/2 inch mark, and you'll have the row of stitches precisely placed 1/2 inch from edge.

With canvas, you could have the top piece of fabric 1/2 inch, and the bottom 1/4 inch, fold over the top piece, sew the second row of stitches – then you'de only have to sew through 4 layers of fabric which would be easier in canvas.

But, I don't know, I'm just thinking

Thanks for the thoughts Jerry,

I think this will simply have to be tested out.
I just did so with 4 small sheets. Two I put together with the seam Roger suggests and two with the glue method.
I haven't tried the felled seam yet.

From what I've noticed so far (And without actual tests in rain which I will do with bigger sheets);
My fumbling and inexpert hands find it a lot easier to simply glue, fold and sew then to hold the seam folded back on both sides and nicely streched to make Rogers seam.

I also see that when pulled apart with force both hold very long but Rogers seam quickly starts showing the sewing holes as the fabric is pulled apart by the thread. SO I think water will get in there.

I agree my idea gives a very thick seam. I will look at leaving out the middle band which is really only there to help fold and as a bit of extra strength. (Also I believe the cotton will swell when wet so the more the better around the seams)

One big advantage of Rogers seam is that the large sheets of canvas will all be on the right hand side of the sewing maschine where I would have to roll the two meters of fabric through the left side ;-). The felled seam has the same problem of course.

Another thing I afraid of is the glue. I hope it won't be food for fungi.

This is all for a tipi project by the way so if this is the wrong place for it please tell me.

I'll do some more practical tests and post again.

Good you're trying different things, find out what works best for you, report back your findings

anyone have a good technique for making this stitch ?

i’ve been using it, and really like it, but it is HARD to make. i pin, then do the green stitch, then take out pins, fold over both pieces of fabric for the red stitch, then pin again, then put the material on a light table so i can see the line that i’ve drawn for the red stitch (which is now covered by the folded over material), then trace that line on to the folded over material so i can see it when i sew the final red stitch on my machine. yeeeeesh….

Kyle, you may need to pin fabrics for the green line, but for the second stitch (red line ) I’m not sure you need to pin again (the first stitch will prevent the fabrics to shift on you so no pins needed IMHO).  Just keep keep a bit of tension on the section on the fabrics you are sewing by holding the fabric behind the needle with one hand and the fabric in front of the needle with the other hand. Just enough tension to keep the 4 layers of fabric taught.

Also you probably don’t need to draw any line for the second stitch.  Just use the marks on your footplate.  If the marks are not clear or your machine doesn’t have them just put some blue masking tape next to the needle (Distance between the needle and the masking tape is the size of the flap you will end up after sewing.

Kyle, it’s not that complicated and Mario got it right.

In general, I never mark my stitch line – I cut my pieces with a seam allowance of a known width and then sew just this distance from the edge. In this case, I’d pin the pieces together only for the first stitch.

Let say I want the seam to be 6mm wide. For a seam allowance, I will use 2*6 (the red-green mark distance) + 3 mm free edges, it is 15 mm. I will cut my fabrics with that in mind. I will then use the marks on the sewing machine to sew 6 + 3 = 9 mm from the edge.

Then, I lie the fabrics flat and fold the seam allowance open and press it flat – this is the easiest way how to start the fold exactly along the stitch line. Then, I just fold the thing along the stitch line and sew the second stitch 6 mm from the folded edge. That’s all.

I generally stick to a flat felled seam and rolled hems but i wonder if this would work using a binder foot.

So long as the fabric is trimmed to the correct length (for mine…I need to trim a 3/8-1/2″ past the first stitch) the binder foot should take care of everything else and result in a stitch that goes through 6-layers and a bit cleaner looking.

Again, I’m going to stress that I’ve never tried it…I have a bunch of scraps laying around and will try test out this theory tonight or later this week.

there’s a forum thread where someone tried a binder foot but thought it wasn’t useful

Maybe if you had a lot of hems to do and you wanted them the same and do as fast as possible

The problem with a flat felled seam ridge line is that as you’re sewing along, the top layer of fabric sticks to the foot a little, and slides relative to the bottom layer of fabric.  By the time you’re at the end of the ridge line, the two fabric layers no longer line up.  If you just cut off the excess fabric it doesn’t pitch good.

Maybe a walking foot wouldn’t have this problem?

Or, a few pins (or I just use hand stitches) will keep the two layers aligned.  Practice with scraps to figure it out.

And you want to keep the two layers of fabric aligned sideways – I usually mark a line on both pieces of fabric where I want the row of stitches to go.

The second row of stitches is easy – pull the two layers apart a little as you’re sewing along.  Fold over twice but it doesn’t have to be folded over exactly – just get close.

I usually do a third row of stitches.  Maybe if I was more expert, had better thread and machine this wouldn’t be as important.  And if I was sewing a lot of tents and had to pay for each hour of seamster.

I have used silnylon (which stretches) and polyester thread (which doesn’t stretch).  Especially at the two ends of the ridge line, the fabric stretches more.  Then the thread can break.  I usually sew a zigzag stitch for that third row of stitches at the two ends.  Then the seam stretches even though the thread doesn’t.

Thanks you guys for your valuable input! I will try the suggestions listed by Jan & Mario, and see if I can make things go a bit more quickly. In general, I try to make up for my poor sewing skills with excessive amounts of marking and pinning. Its a bad habit, and I keep telling myself its because of my hoopty card table and beginner $50 sewing machine, but there is probably a significant amount of user error as well =P

-K

This is a flat felled variant of Roger’s seam above.  Seams (ahem) like this would be even stronger as it has two load bearing stitches, both padded on both sides.  The little fold-under at the edge is unnecessary, and may complicate execution, but gives it a nice, clean, symmetric appearance.  Pending stitch spacing, a 3rd stitch could be run down the middle, but I don’t know if that would further strengthen it or not.

Thoughts?  Has any one tried this?

Feed back appreciated as I have a ridge line seam in my near future…

(Edit: heh – left the image out)

Just occurred to me you could glue the primary fold down and skip the secondary.  Then you’ve essentially got a re-enforcement patch running the length of your seam. This would also be much simpler to sew. But there is, of course, a weight penalty.

I have used Hilleberg’s flat felled seam

I do it such that I pin 3 uppermost layers together, then turn the 4th layer underneath but not pin it. This is the difficult part, ie trying  to keep them nicely together while sewing.

Finally I sew 2 rows as in the picture.

I leave the pinned layers up, so the roof does not have pin holes.

As Jan mentioned above  main reason “Roger’s seam” is stronger is because “the loaded line of sewing is padded in both sides”.

I have been doing some double rolled hem testings with Silpoly PU 4000 (which I understand has a lower tear strength than silnylon) and the fabric always tears at the sticthline on the “unpaded side”.  So just out of curiosity I sew the double rolled hem with a narrow strip of fabric on the “unpaded side” (I know not very esthetic but wanted to test Jan’s theory) and indeed the strength of the hem increased substantially.  It went from taking 25lb to 35lbs before breaking (again at the stitchline).  I have order thinner needles (i.e 60/8) which I will use with thinner thread (i.e MARA 120) to see how that affects the overall Strength of the seam.

Rene, I think your “Dollar Sign Seam” would work well.  I would definitely not bother with sewing inwards the edge of the fabric as it would make it much harder to sew the whole seam but as you mentioned use rather a tiny bed of adhesive between the sticthline and the edge of the fabric.  That should prevent the edge of the fabric to slowly unravel and make your seam stronger.  If you are using a fabric that was different coatings in each side (i.e silpoly PU 4000 or rockywood’s Silnylon 7D) that get a bit trickier though just make sure you use the appropriate adhesive for each side.

Harrie’s technique is brilliant and could also be use for your “$ sign seam”.  I suggest you baste those lower three layers instead of using pins specially if the segment of ridgeline you are using is long.