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-   -   Need math help on DIY tarp (https://www.hammockforums.net/forum/showthread.php?t=1387)

 turk 06-28-2007 00:03

Need math help on DIY tarp

Sorry to admit, but I should have paid more attention in math.
I am trying to get ready to make a heated winter hammock tarp with
a stove jack. Before I cut into some very expensive soft structure
tyvek 1460uv, I want to make a mock up version from an old blue poly tarp.
Rather than cut the profile I want and sew two identical pieces together, I
wanted to make this from a single piece to avoid a ridgeline seam.

I am having trouble with layout. Would anybody here be able to tell me what
my dimensions are where I have marked 'A' and 'B'. That would be most
appreciated. I hope I am not missing any vital info.

Please excuse the crudeness of my drawings. I realize they are incorrectly scaled
and in actuality my tarp is nearly square. It didn't start out that way. I just made
the image and then started playing around with the numbers until they matched a
full scale tarp I had set up in the garage.

If someone could help me out so I dont screw this up. That would be fantastic.
http://ehko.info/proto_tarp_1man_pattern.JPG

 blackbishop351 06-28-2007 00:36

OK one slight problem...

If the long (outside) edge is 12' and the two small end-measurements (from the perpendicular lines) are 12", then the centerline can't be 10'.

 turk 06-28-2007 01:36

okay.....
I think I know what is going on, ....maybe, ..not sure. I was drawing in paint and then using freeware photo software to manipulate different parts of the tarp. But it keeps rounding off my angles to nearest degree. As I played with the cut away portions on the end, the angle on the backbone of my tarp was thrown futher and further off but cutting, rotating shapes and than mirror imaging them and pasting back together. None of the interior angles of any of my triangles were adding up. Very frustrating.

I went back to grid paper protractor and scale ruler.. The paper scale model worked out great.
I am confident I can layout the tarp correctly now. But I am having quite the trouble figuring out how to making curtained ends.

I don't know if I can express it properly in words. I will try and draw out what I am hoping to accomplish and maybe someone has some ideas.
This pic here is dropkicks original concept to shed weight off my tarp. Shows the curtain ends:
http://img.villagephotos.com/p/2006-...amtentheat.JPG
What I am wondering is how can I make them so that I can vary the height of my tarp pitch slightly, and still be able to close the curtains. At the same time, I need to keep tension as best as possible on the curtains so if I pitch low, they aren't flapping.
I realize the simplest answer is to keep pulling the bottom of the curtains towards the trees. But this will keep increasing my overall distance between trees considerably.

 blackbishop351 06-28-2007 02:02

OK I think I understand what you're trying to do. Basically an A-frame with end-doors, right?

A higher pitch isn't a problem - just raise the whole tarp by approximately the same amount.

A lower pitch is going to cause issues with your doors closing, no matter how you cut it. This is one issue with making a fully-enclosed tarp/tent like this - it can be pretty inflexible as far as different setups that offer a taut pitch.

I had this issue with my MSR Trekker (which is pretty much what you're going for) and couldn't ever figure out a way around it. I've actually thought about this issue a fair amount just because I really liked that tarp design overall. I hate ditching a good idea because of one little snag, but I can't seem to resolve the snag in this case.

You may just have to learn to live with pitching the tarp the same height whenever you want the doors to fully shut. On the other hand, this doesn't necessarily mean you can't HANG at different heights - you can open the doors more at the top to allow a lower hang, for instance. Since you'd (presumably) be setting up the tarp first anyway, this would be a fairly simple solution. If you're talking about lowering the tarp pitch for bad weather/wind, I'm not sure what to tell you other than to try to get a really good compromise between head room and stormproofness built into your design from the outset.

 slowhike 06-28-2007 05:56

have you ruled out the JRB type "side walls"? just thinking that might give you some flexibility, but maybe not.

 turk 06-28-2007 06:20

Quote:
 Originally Posted by slowhike (Post 20850) have you ruled out the JRB type "side walls"? just thinking that might give you some flexibility, but maybe not.
umm ... yes and no! :D
I am waiting for the actual JRB hammock tent to come out and already have
an extra stove jack ready to install in it.

But I also wish/hope to make the above design work in its own right.
It seems like it has alot of pitching potential if I have removable end doors.
I have been thinking about multi modes of pitching this tarp, and I think I can
do it with a few extra tie outs. This was an original design that I would like to
still make as a ventillated option with alternate tie-outs:
http://www.hammockforums.net/gallery.../tarpproj3.JPG

The limitations of closing the doors is a drawback, but I don't think ill let it stop me from
making the tarp anyways. I mean DIY projects are fun in their own right, even when
it doesn't all quite work out perfect.

 funbun 06-28-2007 08:45

So you're trying to put a stove inside a tarp? Will it catch on fire? Am I missing something?

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