Sewing curves on ripstop? and other questions

[ZDP-189]

Another question - why are the tarps with aggressive cat cuts in the middle also aggressive on the ends? Then the JRB and Speer tarps, with the less aggressive cuts, more like a rectangle. Has anyone tested a tarp that's almost rectangular, but with an aggressive cat cut in the middle section?

Because I think you'll find that cat cuts are not and scientifically demanding as some would lead us to believe.

An the actual shape depends on several factors:

• The loading profile
• The weight and thickness of the material
• The elasticity of the material
• The presence of, elasticity of and load distribution on hems
• The angle at which the guy line leaves the tarp
• The wind pressure at any given time

In practice, you can cut an approximate cat cut, then adjust the position of the peg to suit. Elasticity of the material should take up slack.

If the cut is too aggressive, more tension will be born by the hem. If it is too straight, the hem will be slacker.

I wonder why nobody has written about incorporating shock cord into a hem. That would have elasticity and bear load, especially beyond the elastic limit.

My wife wants ME to fix some of the hems in some of HER dresses, etc. So, that option is not available in my household!

In my home, for the last 2-3 generations, that has been our 'tradition' too.

[tight-wad]

OK - just posted several pix. Now where are they? Should be in my gallery - but how do I link to it?

3 sets:
1 - the far corners
2 - the ridge line
3 - the mid point tie outs

? 10 pix total?

Advice - no matter what you have today, go out and buy another box of pins if you plan to do this!

I am using tailors' chalk for marking the lines. Works great! but ... it rubs off too easy. With all the handling, I had to remark the lines several times.

These are my "training" pieces. I tried to replicate the 2 corner types and the ridgeline with scrap fabric, that is, places where cat curves come together.

One pix is mislabeled - it is the pix showing what I ended up with for the darts. Basically cut off everything at the point, on a line perpendicular to a mid point line. For this project, that point will be covered up with a grosgrain tie out loop. For another project you may want to be a little less aggressive. (Planning to use grosgrain for tie outs. Hope it holds! Could use some thicker webbing, but except for gale force winds, grosgrain should do.)

Another suggestion: Pin the first point as best you can (it will be messy for the opposite side) with a rolled hem. Depending on the tightness of the curve move down several inches - say 6 inches. Roll the hem here and pin. Then move to the half way point between these two. Roll, pin. Split the difference again between the latest and the first. Roll pin. Go the other way, split the difference, roll pin... Move down another 6 inches. Roll pin, split the difference..... For the close in work at the corners, make it 3 inches to start, and repeat - a lot.

The ridgeline pix show my attempt to make a very tight curve, not what I really plan to do.

All pix show a piece of reinforcement patch.

The mid point close up shows a lot of puckering. Since I don't plan to cover this up with grosgrain, I'll just deal with it.

Time for a bottle of my favorite, a good night's sleep, an attitude adjustment (rah-rah , cheerleader, dancing bananas, you can do it!), and rest before the real thing some time soon.

[Preacha Man]

Here is a pic of my cat tarp, that my wife finished sewing today

[/IMG]

Tight Wad, How is the sewing going? Were you able to do the roll hems without much frustration? I know what you mean by wanting everything to turn out good, especially after you shell out the $$ to make it. If you buy it and its not right you can contact the manufacturer, but with DIY if you mess up, you mess up. Go slow and post us pics.

Dwight