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  1. #1

    Red face Making an 8X8 tarp - math?

    My apologies to JRB, but I'm trying to save a little $$ and I certainly know my way around a sewing machine. However, I basically slept thru math class in high school. Can an 8x8 tarp (two triangles, with a seam running along the diagonal ridgeline) be made from standard sil that's 60-63" wide? Or does it need to be wider?
    Thanks much. I'm glad the hackers didn't hit this site!

  2. #2
    Senior Member
    Join Date
    Aug 2007
    Western New York
    think. 8x8 (along the sides) will have a ridge line length of root 128, just over 11.3 feet long. if it is divided in half for the 2 parts, each half will need to be5.6 feet long. normal sil is 5 feet long, but speer sells 66" (5.5 feet).

    short answer: it needs to be 68" wide to fit your requirements. but you can make it so it would be an 8x8, with just the very corners missing. and if you really want them, you can use the part you cut off to make the triangle shape.

    btw the JRB 8x8 is more like 7.5x7.5

  3. #3
    jeffjenn's Avatar
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    Aug 2007
    HH Expd Asm or DIY or WBBB or .....
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    DIY UQ / CCF Pad
    Boose, by my rusty old math I think the best you will see out of the 60-63" wide sil will be a 7x7 tarp maybe just a tiny larger. Like 1-2" larger depending on your hems & actual width of material. This should give you about a 10' diag. ridge at best. Since you are one of the lucky ones who can sew I would have to advise a hex tarp using 7.5+ yds of fabric. Or to keep cost as low as poss. you can still make an 8x8 with the seam running the wrong way (some commercial tarps are made this way) with a little over 5 yds.

    I think I know what I'm saying here if I'm wrong please chime in. Like I said rusty math!

    Just looked at JRB's site again & they show their 8x8 is actually 7'2"x7'2" with a 10' ridge (just seems a little small) But it looks like their design with the diag. seam still takes 6.67 yds of fabric.
    Last edited by jeffjenn; 01-11-2008 at 00:27.

  4. #4
    Thanks, Skar and JeffJenn - I didn't think it would work with the standard fabric width, but I hadn't been able to figure out how JRB did it. They must have wider sil.

  5. #5
    Senior Member TiredFeet's Avatar
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    Quote Originally Posted by Boose View Post
    Thanks, Skar and JeffJenn - I didn't think it would work with the standard fabric width, but I hadn't been able to figure out how JRB did it. They must have wider sil.
    It's my understanding that the JRB 8x8 isn't actually 8' on a side. It's actually 7' and some inches. Can't remember exactly the something inches. Maybe 6" or so.

    I think they just round it and call 8x8 - it's easier that way.

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