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Salvelinus
2006-01-31, 22:43
Hi, everyone. I've been coming here for quite a while, but have only recently started posting again after a long absence. To reintroduce myself, I'm a physical therapist, am married with two kids 2 1/2 and 5 years old, love backpacking, fly fishing/fly tying, bonsai (the miniature trees in pots), geocaching, and way too many other things to really have enough time for all of them. ;) You all are a great group of people, and I've learned A LOT from you. Thanks!

Now, I have a question and need some help, please. I know most people here use hammocks, and their tarps are intended for that use, but I was wondering if anyone could give some advice on a tarp project I am planning. The purpose will be to use mostly as a dining-type fly and a dry place outside the tent for the kids when it's raining. It will be used for family backpacking, so weight is also a concern. The kids are too little to carry much of anything, so my wife and I will be carrying everything.

I've looked at various designs and articles, and have decided that catenary cut edges would probably be a good idea (I like a tight tarp), but that I may not need a catenary cut ridgeline. I need as much space underneath as I can get for the weight. I'll probably always set it up in a modified A-frame/lean-to style for wind and rain shedding.

I've been looking at this design (http://www.backpacking.net/makegear/cat-tarp/index.html), and it seems like it might be the best for my purposes. One nice thing is that it has detailed instructions. I'll probably do without the specialized tie-outs designed for use with oars, and go with plain loops. I'll also probably add a tie-out in the center and maybe a couple on the panels to increase versatility, but I'm not sure they would be necessary.

Sorry about the long post. :o What are your thoughts on the design, whether or not I should use grosgrain reinforcement on the edges, on the ridgeline, neither, or both, and any other ideas? Thanks in advance . . . :)

oops56
2006-01-31, 23:44
Hosty Hooc at minibulldesign check this one out mr. salvelinus its at the bottom of page
http://www.minibulldesign.com/fs2.htm

brian
2006-02-01, 16:11
Hi Salvelinus,

There are two main problems I see with a catenary ridgeline. The first is that is severely limits the setup options to those that involve an A-frame or very close variant, which reduces the function of a tarp, which is supposed to be flexible in the pitching options. The second problem is head room; a tarp with a catenary ridgeline has perhaps 6"-8" less headroom than a tarp without the catenary ridgeline. Tarps with catenary cut sides form a simulated ridgeline as the side pullouts are staked out. The ridgeline bends in a few inches, but this is due to tension in the tarp, not in the way that it is cut.
You only need grosgrain reinforcement on the perimeter, not on the ridgeline seam. I used to do this, but it just adds weights and is hard to keep the fabric from rippling underneath the webbing without a lot of experience with silnylon.

A few other tips that generally aren't really widely published. Make sure you do a ridgeline that is parallel to the long edge of the tarp. For instance, if you are making an 8' x 10', make the ridgeline along the 10' seam...it makes for a happier and more durable setup when setting it up in an A-frame type setup. Also, I have found that grosgrain is inferior to nylon webbing for tieouts, as the grosgrain comes unraveled over time. Whenever using grosgrain, make sure there are no loose ends exposed; always singe the webbing and fold it over itself to prevent any decay of the webbing in high winds.

Jeff's guide is a really nice guide (and it is what jumpstarted me making silnylon tarps commercially!), with just a thing to add to it, from personal experience. Before you sew on the reinforcement patches or GGR, make a run around the tarp doing a simple fold-over of the silnylon; this is very important to prevent unraveling of the fabric if\when the tarp is snapping in high winds. And while he says to use 3\4" GGR, I have found that 1" is much easier to work with starting out, and is a little more lenient when it comes to mistakes.

If you have any other questions, just PM or email me at Brian@OutdoorEquipmentSupplier.com. Have fun, and don't forget to use polyester thread!!

Brian
OES

Salvelinus
2006-02-01, 20:50
Oops: Thanks for the link! I've looked at that design, but I'm wanting something a bit more flexible as far as pitching options. Also, the purpose of the fly is not to sleep in but to have a rain-free outdoor area. Lastly, I'm not impressed by the strength of the grommets on those tarps.

It's funny. I bought one of the very cheap dining fly's made out of the same material years ago. It had 4 corner poles and one center pole that could be mounted on a picnic table. I think it cost $13. On the first trip, the center pole punched right through the canopy. I patched it with duct tape, and then pitched it in a "flying wing" style because that seemed like the best option. I'd never seen one that way, nor thought anyone else would have pitched a tarp like that. I found out later that I had just reinvented the wheel! :laugh:

Thanks for the help! :)

Salvelinus
2006-02-01, 21:14
Hi, Brian!

I've looked at your site many times. There are two tarps, one hanging on top of the other, on one of the pages that look a lot like the tarp to which I linked above. I've often wondered whether they were the same, or who inspired whom. I had almost decided to go with a hex-shaped tarp for ease of construction, but the completeness of the guide on the link I posted changed my mind. Any thoughts on shape?

Actually, it was your site and your replies on a thread on Whiteblaze that helped me decide that a catenary ridgeline wasn't worth doing, but that catenary edges might be a good idea. I had already planned on placing the seam on the ridgeline--it just makes sense.

Thanks for the advice on the grosgrain. I wondered whether it was really needed on the ridgeline, and whether it would be durable enough on the tie-outs. I think Jeff added it on the ridgeline to protect the material from abrasion by the rope, though I'm not sure. There's a lot of redundancy on that design (or so it appears to me), like having grosgrain loops AND velcro to hold the rope in the middle of the tarp. Then again, I think he was going for durability first, and light weight second (he planned on using this on canoe trips).

When you say to do a simple roll-over, I assume you are talking about folding twice to hide the raw edge inside the seam? I looked again at Jeff's guide, and I didn't realize that he doesn't recommend a seam on the edges. I had assumed that one would be done, for durability as you mentioned. Thanks for the heads-up!

One last question--I agree with your advice to use polyester thread, but Jeff says not to use polyester grosgrain. Any idea why? I would think the improved UV resistance would be worth it, but maybe there's a difference in durability?

I really appreciate your reply, Brian. I may contact you if I have any problems. :D

brian
2006-02-01, 22:34
For ground sleeping, a hex is not the most beneficial tarp shape. When you are in a hammock (what the MacCat tarps you saw in the picture were designed specificly for), you don't need to think about wind driven rain on the ends, so there is a much smaller penalty in a hammock. On the ground, wind driven rain on the ends could effectively render both ends of the tarp useless, so I highly reccomend a rectangular tarp or tarp similar to Jeff's which is at least 10' long. But then I'm paranoid of both my gear failing and getting wet, and you may not be so.

There are a few reasons for doing a rolled over seam under the GGR. Not only does it prevent fraying in high winds (VERY IMPORTANT), but it also gives you something of substance to work against when sewing the tarp. You only need a single roll, as that loose edge will end up being hidden underneath the GGR...only a 1\4"-1\2" is required. Also, when you finish doing the entire perimeter close to the inner edge of the GGR, do a complete encircling close to the outer edge of the webbing...this will end up going through that double layer of silnylon, giving it "wind-rip resistance", which was a real problem in my early tarps...but has been completely solved in my newest tarps.

As for GGR, I purchase all my materials from www.OWFINC.com. They have a very complete catelog of anything you could ever dream of, including incredible customer service. I have purchased all different sizes of GGR from them, and they have all worked fantasticly. They have the GGR, nylon webbing, fabric for reinforcement patches, thread, and anything else you could possibly imagine that you would ever need.

Brian
OES

dropkick
2006-02-02, 03:31
Just a thought, but this is what I'm doing.
I haven't decided on the shape of my new tarp either, so I'm making several different ones out of visqueen (plastic), grommits, and reinforcments of duct tape. I'm going to use them this spring/summer. I don't expect them to last real long, but they should last long enough to show me the limitations and advantages of the different shapes.

Salvelinus
2006-02-02, 20:16
Brian: Thanks for the clarifications. I kind of like to get things right the first time, so I appreciate the tips very much. I know what you mean about keeping things dry. Me too. ;) However, this tarp isn't for sleeping, it's for cooking, eating, lounging, and letting the kids get outside the tent on a rainy day. Since we'll be on the ground anyway, though, I think Jeff's design or a square/rectangle shape would probably be the best. Thanks again, Brian! :)

Salvelinus
2006-02-02, 20:23
Hi, Dropkick, thanks for your reply. Good idea on the plastic prototypes. I may do that as well. Would the grommets hold, though? Even with duct tape, I'd wonder about their strength in a wind. OTOH, you probably know more about it than I do.

An idea: you could try the old pebble trick, where you wrap the plastic around a smooth rock, then tie the line over it. It would probably be stronger, definitely easier to make, and allow you quite a bit of adjustability with setup until you finalize your design ideas. Just an idea, take it for what it's worth. :)

dropkick
2006-02-03, 03:03
I think they'll hold fairly well as I am putting them through 2 layers of duct tape and the plastic.
I thought about tying button rocks or using tarp clamps, but I decided against it as it would both bunch the tarp, changing it's line, and wouldn't show as well how the tiedowns are going to work out.
Grommits are also fairly inexpensive, so I can repair and try again if it rips free.

--If you use bungies on the tie out lines to allow some movement you will have much less billowing and cracking of the tarp, which makes for less strain on the tiedown points. -If you don't have any form of bungie you can also tie one downwind corner to a small rock or dead branch (light enough that the wind can lift it slightly) this also works.

I just now made a drawing of the tie outs in case anybody doesn't get my explanation. (I'm kind of tickled with myself - made the drawing and posted it in about 5 min. - I'm getting better at using paint)

http://www.freeimghosting.com/images/dropkick/p1138950142563.jpg

Lanthar
2006-02-03, 09:13
I just now made a drawing of the tie outs in case anybody doesn't get my explanation. (I'm kind of tickled with myself - made the drawing and posted it in about 5 min. - I'm getting better at using paint)

I've come to believe that paint is the most awesome graphics program ever... nice job, btw...

Salvelinus
2006-02-03, 21:27
Yep. You do know more about it than I do. Great ideas, and nice graphic. :)