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  1. #1
    Member Alter Id's Avatar
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    Making a new tarp, so of course I have questions

    Alright, my first sewing project since 8th grade home economics was a DIY nylon tarp I made last winter. I was very ambitious and decided I was going to try cat cuts on the sides and ridgeline. The end result was adequate but the ridgeline angles sharply from the attachment points to a flat section in the middle. I assume that the reason for this odd shape is that there is to much curve in the ridge line. Looking at other tarps it seems that the cat cut in the ridge is either very light or nonexistent.

    So the question is should a person even bother with the cat cut on the ridge on the next tarp?

    I have very little experience with tarps. Prior to hanging I slept in tents (don't tell anyone) and I thought tarps were for gram weenies living in areas with no bugs.

  2. #2
    Brian's Avatar
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    In my personal experience, if you have a properly sewn tarp with cat cuts all along the perimeter, a cat cut ridgeline doesn't help much with keeping it taught other than restricting your pitching options, and adding, as you experienced, a much more complex shape to work with while sewing.

    If pitched tight enough, a flat ridgeline will actually take the shape of a curve (false Catcut ridgeline), which is another nice benefit to a catenary cut perimeter.

    As long as you get a good cat cut along the edges, your next tarp should be great, considering that you ended up with a reasonable ridgeline even *with* the cat cuts - a straight ridgeline seam will seem like cake!

    Do let us know how it turns out!
    Brian MacMillin
    www.OutdoorEquipmentSupplier.com
    Home of the MacCat and OES 4-Season Hammock Tarps

  3. #3
    Member Alter Id's Avatar
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    Thanks Brian, your input is greatly appreciated. I'm still in the planing stage, picking materials and such, but I will try to post pics of the project when it is under way. I was thinking of DIY sil mixed up and sprayed on with an automotive paint sprayer. I suppose that experiment will get posted on the sil thread.

  4. #4
    Brian's Avatar
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    I don't know much about DIY sil, but I'm sure that not many people have access to a professional paint sprayer, so that may work out well.

    We're a great big friendly community (as I'm sure you've learned), so don't be afraid to post questions as your project continues.
    Brian MacMillin
    www.OutdoorEquipmentSupplier.com
    Home of the MacCat and OES 4-Season Hammock Tarps

  5. #5
    my rl's have a tiny cut to them, about 5/8" in 11 feet. since it's so little of a cut, it suffers from NONE of the drawbacks of a severely cat cut rl like mentioned above, it's just as sharp and doesn't restrict pitch. you actually don't want the rl to droop much in center, it reduces headroom, the droop comes from the rl stretching under the load of the corner ties.

  6. #6
    Senior Member Rushthezeppelin's Avatar
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    Quote Originally Posted by Alter Id View Post
    Thanks Brian, your input is greatly appreciated. I'm still in the planing stage, picking materials and such, but I will try to post pics of the project when it is under way. I was thinking of DIY sil mixed up and sprayed on with an automotive paint sprayer. I suppose that experiment will get posted on the sil thread.
    Let us know how the sprayed on sil works out.

  7. #7
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    A catenary ridgeline does drop and flatten the center area of a tarp. That has its positive points and its negative points. It reduces headroom and it doesn't shed snow as well but also tightens that area of the tarp a good bit and helps shed wind. Whether you want to do that depends on the size of the tarp, the shape of the tarp, the location of pullouts, and what other things you have done to help tighten it.

    I have heard the argument that it limits how you can pitch a tarp but don't agree with that logic. Since it helps an A-frame pitch, then the same argument would mean that not having a catenary ridgeline would limit tarps that don't have it when they are pitched in an A-frame. A catenary ridgeline is just another tool for tighten up portions of silnylon tarps. Silnylon has some peculiar stretch characteristics-- nylon stretches initially under load, stretches slowly under load, and stretches even more when wet. An silnylon is an orthogonally woven fabric that has more stretch along the bias of the fabric. That makes it more difficult to apply tension to the center area with some tarp designs and easier with others.
    Youngblood AT2000

  8. #8
    Quote Originally Posted by Youngblood View Post
    A catenary ridgeline does drop and flatten the center area of a tarp. That has its positive points and its negative points. It reduces headroom and it doesn't shed snow as well but also tightens that area of the tarp a good bit and helps shed wind.
    my point was that that's not necessarily the case, a slight cat cut on the rl does none of those things. i'll find some pics

    rl stretch can cause the rl to drop and reduce headroom too.

    Last edited by warbonnetguy; 02-17-2009 at 15:27.

  9. #9
    Member Alter Id's Avatar
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    Again, thanks to all for the responses. I'm looking at doing something like the Superfly, or if I can come up with a reasonably light weight way to leave the doors at home, so much the better. I suppose if I have to resort to zippers there would be no weight savings over permanent doors. Either way, I'd be doing a standard A-frame style pitch most of the time.

  10. #10
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    Quote Originally Posted by warbonnetguy View Post
    my point was that that's not necessarily the case, a slight cat cut on the rl does none of those things. i'll find some pics

    rl stretch can cause the rl to drop and reduce headroom too.

    Okay, a slight cat cut on the ridgeline is almost like no cat cut on the ridgeline. Here is a photo of a tarp that I think could benefit from a cat cut on the ridgeline to take out some looseness, it is pulled pretty tight on the tieouts.
    Attached Images Attached Images
    Youngblood AT2000

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