Suggested catenary edge depth...

[lazy river road]

tlbj, I recently bought the BWDD v2 (still being made) for the very reason you are explaining. I wanted a full door closure as well as more coverage when my flaps are extended. I like the BWDD v2 because the sides are cat cut but the flaps arent...this allows for a full closure instead of a gap up top. When researching about weather I wanted cat cut flaps or st flaps the biggest difference (explained by Ed) was that with cat cut, because the top of the flaps are not completly closed off you allow for better air flow reducing condensation, if you have a st. cut and your doors are fully closed, you reduce air flow allowing for more condensation build up. So I like the v2 because I see it as the best of both worlds, Just something to think about. Id love to see some pics when your done, have fun thread injecting

[SmokeHouse]

My DIY tarp is very similar to Speer Winter Tarp. It has a 11’ catenary ridgeline with a 4” drop in middle. I had no reasoning for the 4”,,,, just guessed… it’s just a tarp and if I didn’t like it I would have made another… I kelp the edges straight so I could close the doors and really didn’t think a cat cut on the edges would help that much… IMO…

[tlbj6142]

My DIY tarp is very similar to Speer Winter Tarp. It has a 11’ catenary ridgeline with a 4” drop in middle. I had no reasoning for the 4”

Looks great. It is hard to tell from the photo, but other than the ridge-line catenary curve, is it just a simple rectangular tarp?

[SmokeHouse]

Looks great. It is hard to tell from the photo, but other than the ridge-line catenary curve, is it just a simple rectangular tarp?

it just about is.... the top is 11', the bottom is 13', I cut 1' up from bottom corners. just a simple design. Also opens nicely for a dinner cover. a few more pic's,

[sclittlefield]

Edit: One of the above threads "suggests" 1" per foot. That seems a bit too much. And looking at the photos of the JRB and Speer tarps, it certainly doesn't look like they are using that "suggestion", but it is hard to tell for sure when looking at the photos.

This is approx. the depth of curve that I am using. I don't span more than 6' at a go, so there's only a 6" depth in the center. You'll be surprised how shallow it really looks when done.

Might look at Backwoods Daydreamer's Winter Dream v.2 as it has been amended over v.1 having straight cuts on the short ends to allow for a complete enclosure.
stumo

Here, this may help. Image is to scale.

it just about is.... the top is 11', the bottom is 13', I cut 1' up from bottom corners. just a simple design. Also opens nicely for a dinner cover. a few more pic's,

Here's another pic of the Winter Dream (very similar to SmokeHouse's framework - just with cat cuts on outsides rather than ridgeline) - opened up with an awning. Back side is cliped up to Hex shape in this image.



I'm looking forward to seeing your tarp when you finish it. Feel free to pm me with any specific questions if you run into trouble along the way.

[WV]

Hgn8r's method will work fine if you want quick method for making curves. If you want to get anal scientific about your cat curves take a look at this thread or just go to this page and download the Excel file that will give you curves based off of dimensions.

Who says Hogn8r's method is unscientific? "Catenary" comes from the Latin, catena ("chain"). A catenary is defined as the arc described by a hanging chain.

[oldgringo]

Who says Hogn8r's method is unscientific? "Catenary" comes from the Latin, catena ("chain"). A catenary is defined as the arc described by a hanging chain.

I was having similar thoughts. There was once a Coast Guard Cutter Catenary, btw.

Now, a question: how do these spreadsheet cat curves differ? How are they derived?

[Spevas]

It varies greatly depending on the fabric, and is best determined experimentally. Once your fabric has been cut to a rectangle approximating the final size of the tarp, grab the ends of the tarp along the edge where you want the catenary cut and pull them taut. In the middle of the taut section, you'll see a bulge in the fabric a few inches from the edge. The bulge likely won't be a sharp crease, but it will be quite obvious and will still give you a good idea of what the maximum drop of the curve should be.

The general rules like "one inch per foot" probably waste a lot of fabric and coverage in many cases. I've seen a huge variation among materials, e.g. thin canvas had about 1" drop over six feet, and a reinforced ripstop/mylar emergency tarp of the same length was about 2-3".

Keep in mind that hemming or taping the edge after you make your cut may change the ideal depth for the curve, but not by much. When in doubt, make the curve a smidgen deeper.

[XTrekker]

A few inches is just fine for 3 or 4 feet. If your getting around 8 feet then I would probably do about 5 inches. You really dont need that much.

[Boston]

I think these recent responses are about...4.5 years too late...