My first projects and a Cat cut?

Ryan, Congrats on the projects, please post pics if possible. I've only done one project with a cat cut ridge line. Mine had uneven heights. I used a standard formula/spreadsheet and it worked great. But you bring up a great question…should it be different if the heights are different? It would seem like it should now that you point it out, but maybe the difference is so small you dont need to worry about it.

Jamie

Thanks, you're probably right. The height difference isnt likely to be enough to bother with it.

You don't have to worry about it. Just down load the spreadsheet on cat curves from this website and it will calculate the curve for you. Just assume the straight line is between the tops of your fabric at the poles. I used the 2.5" max deflection over 99" and had more than plenty of curve: http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=27609 for pictures.

Thanks guys, thats what I did. Just finished another tight flat felled ridgeline, max deflection 3.12 over 94. Couldnt wait for more replies, them feed dogs was barkin'. :)

A chain hangs in a catenery and and if the endpoints aren't at the same height, the curve isn't symetric like it is in the spreadsheet. I just proved this by experiment. The nadir moves toward the lower pole. That said, if the heights don't differ too much, the difference will probably be negligible. It may even be advantageous to keep the nadir centered. I don't know that much about the physics of tarps.

I sweated over constructing a catenary until I checked out the spreadsheet. It turned out that the error from using a circle instead of a catenary was about a 64th of an inch for my project.

Anyway, if you have a piece of bead chain the length of your ridge, you can hang it between you poles with the desired amount of dip and it will give you a catenary section.

I knew that the deflection should drift towards the rear pole but decided that just sticking with the standard midpoint would probably get me close enough.

Just finished the last of the GG tie outs. Dumping snow out but I'll likely get out and pitch it to have a look. If the pics turn out, I'll share.