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Catenary Help
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Jamie Shortt
(jshortt) - MLife

Locale: North Carolina
Catenary Help on 09/27/2009 14:50:28 MDT Print View

I'm working on a mini tent that has a ridgeline that is 86+3/8" long. Any chance someone could supply me with the adjustments to use to give it a catenary shape.

I also have a grace solo tarp. Is it possible to use it as a guide, just ignoring the extra length?

Thanks, Jamie

Joe Clement
(skinewmexico) - MLife

Locale: Southwest
Catenary Help on 09/27/2009 15:22:30 MDT Print View

I've never done it, but I think I read that you can hang the material on the wall, then hang a rope with some slack in it along the ridgeline, and trace the rope. Like here - http://www.backpacking.net/makegear/cat-tarp/index.html

Tim Marshall
(MarshLaw303) - MLife

Locale: Minnesota
Re: Catenary Help on 09/27/2009 15:24:58 MDT Print View

In the 5yds to SUL article Jay suggests copying the curve from another tarp. It should come out ok even though the length isn't the same.

-Tim

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Catenary Help on 09/27/2009 15:30:21 MDT Print View

Hi Jamie

If you send me your email address I will send you a spreadsheet which allows you to calculate this for whatever dimensions you want.

Cheers
Roger@backpackinglight.com

Lance Marshall
(Lancem) - F - MLife

Locale: Oregon
Catenary Help on 09/27/2009 15:48:47 MDT Print View

Yes you can copy your Grace tarp. Start in the middle and work outward ignoring the extra length on each end.

The spreadsheet I posted in 2006 is still available.
2006 Spreadsheet

-Lance

Edited by Lancem on 12/04/2014 00:00:10 MST.

Christopher Bumgardner
(quillbone) - F
caternary on 09/29/2009 01:29:52 MDT Print View

Roger, is your chart a list of calculations, with a length variable, of points on a hyperbolic cosine curve?
By the way, I am not much of a regular poster but an avid reader here. I appreciate all your insightful articles and comments. Thanks.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: caternary on 09/29/2009 04:06:45 MDT Print View

It's a spreadsheet with a graph for pretties.
You can plug your figures into it - length of span and amount of sag. You get XY points along the line. Email with your address if you wish.

Cheers
roger@backpackinglight.com

Matt Lutz
(citystuckhiker) - F

Locale: Midwest
Re: Re: caternary on 09/29/2009 11:50:57 MDT Print View

So the part that gets me about MYOG cat-cut tarps is how do you sew the ridgeline? I have an Oware cat tarp, and the ridgeline appears to me a French seam (maybe flatfelled?), but with the curve, how does that work?

Pictures of the process, anyone?

Lance Marshall
(Lancem) - F - MLife

Locale: Oregon
Catenary Help - Pictures on 09/29/2009 13:48:59 MDT Print View

Use a flat felled seam. The plans I work from have a 1" seam/hem allowance all around so I offset the two halves 2/3". One side gets 2/3" allowance, the other side gets 1-1/3" allowance. When the seam is finished, a total of 2" is used and the seam is perfectly centered.

Two halves 'right side' to 'right side' and offset 2/3" :
Tarp halves before sewing

Sewing first seamline:
Sewing tarp ridgeline

First seamline finished:
Close-up of first ridge seam line

Sewing second line after opening up the two halves and rolling/folding the seam allowance (looking at the 'wrong' side):
Sewing second ridge seam line

Edited by Lancem on 10/06/2009 22:04:58 MDT.

Matt Lutz
(citystuckhiker) - F

Locale: Midwest
Re: Catenary Help - Pictures on 09/29/2009 14:55:47 MDT Print View

OK, that's what I thought was done. I was worried about the tarp ridgeline buckling because of the slope of the curve. I guess it is not as severe as I thought.

Also: bookmarked page - all MYOG folks with an interest in cat tarps should, too.

Edited by citystuckhiker on 10/01/2009 09:17:35 MDT.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Re: caternary on 09/29/2009 18:37:44 MDT Print View

There's been a lot of interest in my spreadsheet, so we will try to figure out how to make it publicaly available from BPL. Stay tuned.

I tried Google Docs, but they can't handle the embedded graph. Feeble.

Cheers

Christopher Bumgardner
(quillbone) - F
Thanks on 09/30/2009 17:48:55 MDT Print View

I'm sure many people would appreciate the spread sheet Roger. Thank you.

Lucas Boyer
(jhawkwx) - MLife

Locale: 38.97˚N, 95.26˚W
white lines? on 10/01/2009 09:01:19 MDT Print View

Lance, are the white lines you have on the tarp the markings for usable sleeping space? What pattern are you using, if you don't mind me asking?

Lance Marshall
(Lancem) - F - MLife

Locale: Oregon
Catenary Help - white lines on 10/01/2009 11:02:14 MDT Print View

The material in the above pictures is actually the fly portion of a tent I designed and made for myself. The white lines mark where the mesh walls attach to the fly.

tentpic2small

More information and pictures in my 2007 Post

Edited by Lancem on 10/01/2009 13:12:03 MDT.

Matthew Dunn
(Boddunn) - F

Locale: Kirby Muxloe
Re: caternary on 10/06/2009 09:17:11 MDT Print View

Hi Roger,
Just a bump to see if you've managed to figure out how to get the spreadsheet to work? No pressure, just being nosey.
Matt

Lance Marshall
(Lancem) - F - MLife

Locale: Oregon
Downloadable Catenary Curve Spreadsheet on 10/06/2009 18:54:28 MDT Print View

I've put my 2006 catenary curve spreadsheet on-line. The spreadsheet was created using Microsoft XL 2002. The spreadsheet is at the bottom of the page and is 23kb. The web page works with Explorer v7. It should also work with other versions and other browsers, but I haven't tested it.

Be patient, it's slow.

Web page for Catenary Curve Spreadsheet

Let me know if it doesn't work for you.

Edited by Lancem on 10/06/2009 18:58:07 MDT.

Greg Mihalik
(greg23) - M

Locale: Colorado
Re: Downloadable Catenary Curve Spreadsheet on 10/06/2009 19:01:11 MDT Print View

Lance,
I Just saw the photo of your tent, and have to say it looks like a piece of art. I wish I had the patience to something that clean. Very nice job.

Kier Selinsky
(Kieran) - F

Locale: Seattle, WA
Re: Catenary Help - white lines on 10/06/2009 20:01:29 MDT Print View

Lance - this may be a dumb question, but looking at the spreadsheet curve, it starts and ends at 0. But looking at your tent, you obviously have a high and low side. So did you just use half the curve on the spreadsheet?

Oh and BTW - your spreadsheet hosting worked.

Lance Marshall
(Lancem) - F - MLife

Locale: Oregon
Catenary Curve Ridgeline Explaination on 10/06/2009 20:42:54 MDT Print View

Kier:
The tent ridgeline uses the complete curve layout from zero to max back to zero. Here's a rough drawing of how the curve was layed over a straight ridge line. I overlayed it to intersect the straight ridgeline where the walls intersect. That way I didn't have to make adjustments to the wall pattern.

2D Drawing of Fly Pattern with Cat Ridge
-Lance

Edited by Lancem on 10/06/2009 22:31:44 MDT.

Kier Selinsky
(Kieran) - F

Locale: Seattle, WA
Re: Catenary Curve Ridgeline Explaination on 10/06/2009 22:23:28 MDT Print View

OK now I think I got it. It doesn't matter what the height of each end of the tarp is, just the deflection from the original ridgeline? So first I decide the angle I want the ridgeline, then I plot the points from the graph, then I cut? So it doesn't matter even if I want something ridiculous like the tarp opening to be 6' high on one end and 1' high on the other? Thanks! so much easier