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I am almost done with my diy Blackcat tarp. I am at the point of deciding to use trim or not to trim. Do you use double folded bias tape or is there something better? Also does the trim serve any purpose other than cosmetics such as does it add strength? I took my time and my hems look perfessional so if the trim is just to cover up crooked seems, I'd prefer to show off my handy sewing abilty.
I didn't trim and it works very well. Look at my gallery photos. I don't think it is worth the extra weight. I personally don't think it adds much strength.
I intend to trim mine since I'm going to be using very light fabric. You can make your own "tape" for trimming if you want. I'll be using 3.9oz coated ripstop to make my just barely biased tape... :) cut on a 10-15 degree angle instead of a 45 degree one. Allows some conformance to curves, but is stronger than 45 degree bias.... :D With the cat cut it distributes the tension evenly along the edge.
If I was using heavier fabric I'd be less likely to do so, especially with a good rolled hem.
two reasons to use trim. it can be used to cover up a raw edge. if you use bias tape, like rapt mentioned, it will be stretchy and not provide anything structural.
if non biased trim is used, the traditional corner pull tabs (weak link in the tarp) can be left off the tarp entirely, and the trim can take the load. what this does, is distribute any force applied to the tarp (wind for instance) to the trim, which then can distribute it evenly among the several thousand stitches around the entire perimeter of the tarp (like a trampoline), rather than applying the same force to a few stitches at each corner. you have to incorperate cat cut sides to achieve this though, but such a tarp should be able to handle much higher forces, and as a plus, the tarp will be stretched much tighter than is possible with regular corner pull tabs.
i think this is a new idea though. after i came up with the idea, i decided to search for other tarps with non traditional pull tabs. i found that the granite gear white lightning uses the same concept. the tarp i had at trail days and the granite gear white lightning are the only ones like this that i know of. the white lightning actually uses trim folded over the edge, i use 1/2" nylon grossgrain ribbon threaded through a rolled hem.
Warbonnetguy,
Do you have any pictures of how you connected the pullouts? I'm pretty new to DIY gear and have not been able to find any closeups of the Granite Gear White Lightnin tarp.
If you don't have pictures, could you please describe what you did?
The hem along the edges already distributes the forces along the edge. I still firmly believe it is for aesthetics alone.
no, if regular corner pull tabs are used, ALL force is distributed only to the stitches that connect the pull tab/pull tab patch to the sil. no actual force is distributed to the edge, trimmed or not.
Quote:
Originally Posted by lvleph
the only pic i could find is here: http://www.hammockforums.net/forum/s...+hammock+specs
i don't have one right now to take a close up of, but i'll try to draw a diagram.
basically, each side of the tarp has one piece of grossgrain ribbon running through (and stitched into) the hem from one end to the other. at the corners, the hem is open and the grossgrain is exposed. this is your pull tab. i have a plastic o-ring there to minimize wear on the grossgrain ribbon.
the 2 end corners are different. i just take a foot or so of 1/2" flat weave nylon webbing and sew it (doubled over) to the ridge seam. the two long pieces of grossgrain ribbon terminate inside the stitching of these end pull tabs.
Quote:
Originally Posted by nartoff
here's a drawing.
Thanks for posting those pictures; I think that's what I'll end up doing when I finally make my tarp.
send me a pm if you need more info
Quote:
Originally Posted by warbonnetguy
WBG,
Take another look at the stock Hennessy flys.... Believe it is also a continuous loop of tape with just excess formed into a loop at the corner.
Pan
Yeah, it depends on the method of attaching the pull tabs. Of course, if your trim is the the pull tab a more even distribution of those forces would occur, compared to pull tabs sewn down the hem just a few inches. Excluding the trim as part of the pull tab, whether you have trim or not, in my opinion, does not effect greatly the distribution of forces along the edge of the tarp. Of course, I am not doing any scientific experiments, but my knowledge of physics tells me this is the case. If the difference in fabric makes some difference in the distribution, it will be to a very minimal extent.Quote:
Originally Posted by warbonnetguy
yeah, but there is no cat cut, so it doesn't work like it could. same thing with the eno flies. thats why you never see one of those flies set up taut. they flap around like a flag in the wind.
in a perimeter loaded design, the cat curve is even more important in the tensioning of the tarp than with say a mac cat style tarp. with a mac cat style, the cat cut just removes excess loose fabric at the edges, the corner pull tabs stretch out the interior. the cat cut doesn't actually effect the tautness of the interior of the tarp like it can on a perimeter loaded design. in a perimeter loaded design, the webbing/trim in the curves wants to flatten out when pulled upon by the guylines. so it tries to, pulling the tarp with it and stretching out the sil in all directions like a trampoline in the process. the result is the tightest possible pitch and a tarp that distributes any force evenly among as many stitches as possible. such a tarp should hold up to alot heavier wind forces.
Quote:
Originally Posted by Peter_pan
yes, i agree with that, and i suppose if the stitches on a "regular" corner pull tab go all the way to the edge, the edge is somewhat loaded, but just not in the sense i was speaking of, which was taking all the load. and i also agree if the corner pull tabs are used on a regular pull tab setup, the trim just hides the fabric edge and does not distribute much force.
sorry for the confusion...Brandon
Quote:
Originally Posted by lvleph
in your 1st drawing it shows the grosgrain to be inside the hem w/ only one line of stitching going down the center of the grosgrain. is that right?
if so, what's the process for the hemmed edge?
if you've already explained that, just point me to it.
i've done it a couple ways. the pic would be: single stitch the hem. then thread the gg through and stitch it in place. so the hem itself is double stitched with only one of those lines of stitches going through the gg to hold it in place.Quote:
Originally Posted by slowhike
i have also stitched the gg to the raw edge, and then rolled and stitched the hem. not sure which is easier, but with the first method, you really have to have someone help you thread the gg through with no twists. (there is a half twist where each pull tab turns the corner though)
ok, i wondered if that may have been it (method #1), forming a channel in the hem, then threading the grosgrain through.Quote:
Originally Posted by warbonnetguy
no unnecessary stitching to weaken the fabric that way.
for threading the grosgrain through w/o twisting, a long, flat, length of metal like an electrician's fish tape, used to run wire through conduit comes to mind.
how did you do it?
Brandon since I have already done my hems am I correct in thinking I am too late for your method?
a coat hanger and a fiancee' :)
Quote:
Originally Posted by slowhike
i don't know, could you thread 1/2" grossgrain through there?. even so, might have to redo the hem at the corners (not that big of a deal), so the hems were open at the corners and so there was an inch+/- or so between the two sides (see diagram on previous page). also, make sure to get the amount of gg that sticks out of the tarp just right. too much sticking out and the hem openings could get stressed, to little and the corners will be a little wrinkly. just keep the same angle the webbing has coming out of the hem. it's not too hard if you watch for it. use a pin or whatever to hold it where you want it.
Quote:
Originally Posted by Dutch
All I have to do is seem seal. Man I am proud of how this turned out. Big thanks to BB and lvleph. I knew lvleph when all he could make is a stove or two, now look at him with his fancy speadsheet.
Brandon there was just no way I could get grossgrain in that hem. It was way to tight. Next one I'm gonna have to try your idea. I like the idea of not putting all that webbing on plus it will make it pitch tighter. I will be bringing it to Maryland Hangout in two weeks to show it off.
I've got a follow-up question on this topic--this is a mid-course correction.Quote:
Originally Posted by warbonnetguy
If I want to skip the traditional corner-sewn tie-outs and use a method to transfer the force to the entire hem, which approach would be a better solution:
1. Sew 1" Grosgrain to hem both sides of the tarp in a continuous band, leaving a loop (or twist?) at the four outer corners where a D-ring is installed
2. Sew 1 1/2" Grosgrain in sections to hem the tarp, leaving a channel in which a (for lack of a better term) flat drawstring is threaded. A D-ring would be placed in all four of the open corners for tieouts.
I'm thinking #1 would be my best bet. I think I'll reinforce that webbing in the corner to minimize wear.
Thanks for this discussion.
TWS
I would go with #1.
I'm wondering about the best way to thread the grosgrain through the hem. Although the coat hanger and fiancée technique sounds like a, um, delightful bonding experience, I can't help but wonder if there's a more direct method.
One thing that came to mind tonight was using bullet weights, found in the fishing section of Wal-Mart. They are heavy yet quite small--the 1/8 ounce ones are less than 1/4 inch wide, and the 1/2 ounce models are just under 1/3 inch wide. They have a hole running through them, and their narrow, pointed shape seems to be ideal for finding its way through a hem.
Would it work tie a length thread through one of these, tie the other end of the thread to the grosgrain, and let gravity do the work of pulling the bullet weight--and with it, the grosgrain--through the hem?
There may be something obviously wrong with this idea, but as I wait for my sewing machine to get back from the repair shop, I have nothing to do but fantasize and obsess during the day.
I think the weight idea might work... I'd pull a stronger line than thread though, (fishing line?)... And get it all the way through one side before using it to fish the grosgrain through.
Use a large safety pin. Old sewing trick. It's long enough and has enough stiffness to push through a channel.
I'm not certain I understand how the large safety pin would be better than using a heavy weight. It makes sense that a safety pin would be easier to push and pull it through a channel than just the grosgrain alone, but letting a weight fall through the channel would seem to be so much easier than manipulating something through all those yards of hemming.
Am I missing something here?
It actually works very quickly just use the pin to catch the end of the grosgrain ribbon, and then close it up.
It just feeds through sort of caterpillar/accordion style. Push the pin down the tube (gather the fabric over the pin) then pull the gathers off the back, then repeat.
A wire fish as used by electricians would be the fastest method, but its a pretty specialized piece of equipment. Literally it'd take longer to attach the grosgrain than to feed it down and pull it back....
I think it's a clever idea. Nylon is plenty slippery, as long as the channel is wide enough should be fast and easy.Quote:
Originally Posted by nartoff