Catenary or flat tarp?

[sierraDoug]

I'm looking into making my own tarp. A flat design seems to have more options of how to put it up, and it's simpler to make. Do you see any definite advantage to one with a catenary ridge and edges? Frankly I like the look of good ol' Ray J's design with the beaks. Any experiences with this or other tarp designs?

[DebW]

Flat tarps can be hung across the open side of a shelter in cold and windy conditions, so that's a plus for them. Versatility is good. But if you prefer to sleep on the ground, then a catenary tarp with beaks might be your preference.

[Youngblood]

I have made a few tarps with catenary curves on ridgeline and edges on silnylon tarps. These tarps are used with a hammock, are rather large (8'x11' and 10.5'x11') and are used in an A-frame pitch. I have been very pleased with them. They are more difficult to make, but in my opinion they are a class above a standard flat tarp when both are used in an A-frame pitch. I suspect that only applies for an A-frame pitch.

Basically they keep the tarp more taut without the use of panel pullouts. If your tarp is not large enough to require panel pullouts or you are not using an A-frame pitch, the catenary ridgeline probably isn't worth the trouble. The way I would try to describe it is that the catenary ridgeline removes the loose material that you would otherwise use panel pullouts to pull taut. The catenary edges don't do as much, they basically remove the loose fabric along the edges of the tarp.

Youngblood

[Singletrack]

The catenary tarp is alot better in windy conditons. Whereby the flat tarp is more versatile.(various ways to pitch it.)

[peter_pan]

Wind stability in optimum pitch vs flexibilty is the main issue. How the ridge line is located is another major issue. article on tarps and this issue is at WWW.jacksrbetter.com in the articles section.

[gardenville]

Wind stability in optimum pitch vs flexibilty is the main issue. How the ridge line is located is another major issue. article on tarps and this issue is at WWW.jacksrbetter.com in the articles section.

I went to your web site and read what you have on "Tarps" your "thoughts" about the Catenary Tarp design. I own two Cat Tarp's, one is an old orginal Moss "Heptawing" bought about 14 years ago, the other is a Mac Cat made for me with a lighter material than Brian's normal material. I wanted something bigger and lighter.

You thoughts about only having one way to pitch a Cat Tarp is wrong, wrong, wrong. Maybe a better way to say this is that with more experimentation you will discovery there are a lot of ways to use a Cat Tarp. I have pitched my Cat Tarps in all kinds of ways and used the Moss Tarp in some heavy wet snow a few times. I use my trekking poles to lift one side or both as the weather permits and have used two poles on one side almost like a learn-to.
I am a Hammock camper so my Cat Tarp is tied above my Hammock to a tree most of the time

I know you are the business to sell what you make and if you can't make or don't want to make a Cat Tarp don't bad mouth them. I have followed your start up in the gear business and that takes a lot of courage in this day and age. I think you have followed others in your product designs instead of leading in new design ideas. This isn't bad but you might want to reflect on this and see if you can become something special instead of someone that just makes a really good copy.

[sierraDoug]

Gardenville,
This is the crux of the biscuit for me. Can you set up a catenary cut tarp as an A-frame at various steepnesses of the tarp? Or is it taut at one angle and progressively more floppy as you move the angle flatter or steeper? I haven't been able to puzzle out the math, or visualize this very well. What have you found with your cat tarps?

[tlbj6142]

I know you are the business to sell what you make and if you can't make or don't want to make a Cat Tarp don't bad mouth them.Their "article" claims they make both flat and Cat Tarps. But they don't list a Cat Tarp on their "Products" page.

[tlbj6142]

This is the crux of the biscuit for me. Can you set up a catenary cut tarp as an A-frame at various steepnesses of the tarp? Or is it taut at one angle and progressively more floppy as you move the angle flatter or steeper? I haven't been able to puzzle out the math, or visualize this very well. What have you found with your cat tarps?You can setup them up a various angles. IOW, you can make a narrow steep sided tarp or a wider flatter tarp. What you can't do easily is setup the cat tarp flat in a single plane. Not sure exactly why you'd what to do that. Especially when used with a hammock, but you often see small flat tarps setup in position. Mostly as a wind break with no intentions of stopping precipitation.

[tlbj6142]

BTW, I have a Cat Tarp v1.0 (http://www.cattarp.com/) (See the Special Deals page). At 6.7oz sealed, it is perfect for one person. It might be a bit short in blowing rain (which I haven't had to deal with yet), which may explain why Oware now makes the Cat Tarp v1.1 that is a tad longer.

Honestly, if I didn't already own my Oware Cat Tarp, I'd save a few more pennies and buy a SpinnShelter (http://www.gossamergear.com/cgi-bin/gossamergear/Spinn-Shelter.html), as they offer better coverage in storms, yet provide the fexiblity (see setup pics and link towards the bottom of the above link) in setup and various ventilation methods.

Some tarp folks add a breathable bivy (think bag cover) in combination with their tarp to protect against blowing rain/snow and cut a bit of wind. With the SpinnShelter, I'm not sure you'd need the bivy. As you can close off the ends (or leave them partially open) in a bad storm. And, if pitched on the ground, you wouldn't get too much (if any) wind blowing under the sides.

Combined with the matching Bug shelter (http://www.gossamergear.com/cgi-bin/gossamergear/Bug-Canopy.html), ground cloth (http://www.gossamergear.com/cgi-bin/gossamergear/spinn_sheet_ground_cloth.html), guylines and stakes you have a near perfect 3+ season shelter that weighs 8.7 + 3.0 + 1.7 + 2.1 == 15.5 oz.

[sierraDoug]

Yellow Jacket,
Great info. Thanks. That's exactly what I needed to know about setting up cat tarps.

The SpinnShelter looks cool, but it's a lot of money. I might take a few ideas from it for a homemade tarp-thing, though. I'll have to research that fabric. I've seen and felt silnylon, and heard plenty of good things about it, but this spinnaker fabric is new to me. Wonder if it's even more delicate. And if it's buyable by the yard.

[tlbj6142]

Obviously if you are going to make your own gear a flat tarp is signifiantly eaiser to make. And typically wastes far less material than a cat tarp.

If I were going to make my own tarp, I'd go with an 8'x8' or 6'x8' tarp. And build a simple bag cover (aka breathable bivy sack) out of 1.1 ripstop with a silnylon floor (so you won't need a ground cloth). Both are fairly easy to make and would probably cost you less than $60 in materials.

There are several DIY tarp designs on www.backpacking.net (http://www.backpacking.net/) and, of course, Ray Jardine sells his kit for (http://www.ray-way.com/php/order-form.php) $55 (don't forget to buy his book $15 so you know how to make it).

Another source for tarps is www.mountainlaureldesigns.com (http://www.mountainlaureldesigns.com), but his site is a bit fubar'd right now.

[gardenville]

Gardenville,
This is the crux of the biscuit for me. Can you set up a catenary cut tarp as an A-frame at various steepnesses of the tarp? Or is it taut at one angle and progressively more floppy as you move the angle flatter or steeper? I haven't been able to puzzle out the math, or visualize this very well. What have you found with your cat tarps?

Let me say up front that this answer has not been cleared by me as scientifically verified by MacGyver.

I am not sure I can visualize what you are asking. The ridgeline of the Cat Trap design is made to be connected tight at both ends. Lets say connected to two trees. You get a curve that keep pressure on it and it stays tight. The sides of typical tarp are shorter than the length of the ridgeline. They are staked out and adjusted to be tight. The sides can be propped up/out with a trekking pole or pole of some other type in a lot of places and or ways. I would say that the common way to use a pole is at the place where the guy line is attached to the tarp. My Moss Tarp has 6 tie out points/guy lines and my Mac Cat has 4 tie outs/guy lines. That gives me that many places to put a pole at a strength point built into the Tarp. I could put a pole at each of the guy line points. This would open the side on one side or one place on one side or I could open the sides of both sides of the Tarp. You could build a Tarp with more tie points and then have that many more ways to set up the Tarp. I need a movie of this. In all of this the Tarp ridgeline is going to stay the same.

To the question about setting up a Cat Tarp like/or as an "A" Frame. If I had a Cat Tarp with a short ridgeline (both my Tarps have a ridgeline of about 10') and sides that were 5' or 6' or so long from the ridgeline the Trap would look like an "A" Frame. You would have to attach the ridgeline high enough so the long sides just reached the ground. I would want to connect this to a tree.

This would (YES) give you a Cat "A" Frame. It would be open on the front and back but it would be easy to attach walls and a door.

Here is where we get creative. You make a Tarp with 2 Cat curve ridgelines.
Something like a cross. One Cat curve on the long ridgeline say on the north to south line and at the mid point of the long line you make a Cat curve going east to west. You can use the tarp two ways. As a typical Cat long ridgeline Tarp and 2 as a Cat "A" Frame on the short ridgeline.

Why would we want something like this? I might use this in warm weather with my Hammock with the Tarp on the long ridgeline. In winter with snow I could set it up in the "A" Frame mode and use it like a light tent.

This has made me hungry. Interesting idea. Comments???

[peter_pan]

Gardenville,

I believe you misread our tarp article and cast some unfair aspersions.

First, the article fairly offers both good and less than good points on traditional flats and catenary cut tarps, especially as it applies to ridge line catenary cuts. While I would not debate that a catenary can be pitched many ways, they all must in some way take advantage of the catenary cut and include some use of the optimum or near optimum angle. The fact remains, catenary ridge lines are a simple geometry problem and there is an optimum angle to pitch a tarp with a catenary ridge. Other pitches may require creative use of poles and/or guy lines to adjust or take up slack caused by the cut. Many traditional tarp pitches, such as the simple lean-to, baker fold, and three sided tee-pee or miner's pitch for flat rectangles don't work with catenary ridges. Second because both sides of these considerations are presented, especially the strongest point for catenary cuts, i.e., the virtual elimination of flapping, it is very unfair to state the article, "bad mouths" any product. Our recommendation is clearly stated as just that, our recommendation. Anyone looking for a good introduction to tarp shelters should check David MacPherson’s introduction. It can be found at WWW.equipped.com/tarp-shelters.htm (http://www.equipped.com/tarp-shelters.htm). This article gives some 30-40 tarp shelter techniques/styles, probably not more than 5 or 6 are are readily pitched with a catenary ridged tarp.

While our preference is for flat cut tarps, we in fact, make either a catenary cut or a flat cut tarp in a good size for both a hammock or personal ground tarp use. Other than the recently opened Mountain Laurel Design web site I don't know of any other makers using the diagonal design ridge line.

As to following or leading in product design, we recognize that our Nest is not the first under quilt. It is to our knowledge the first commercially available under quilt. It is also the first under quilt to incorporate a slit entrance compatible with Hennessey hammocks. It can be configured to use with top or side loaders as well. It can also be readily worn or used when sleeping in a cabin or on the ground. It is compatible with the Hennessey Super System. While it was introduced at Trail Days a day before the Super System was displayed, it was in the hands of some customers over a month ahead of Trail Days.

The No Sniveller Universal Quilt is the only quilt or sleeping bag with a re-sealable head hole that enables its use as a simple yet effective serape. This original design was developed in direct response to the input of Whiteblaze members who commented and contributed to the early Spring thread, "Underquilts-the best answer" in the hammock forum.

The Nest and No Sniveller incorporate compatible sizing and features. By design they can be used as a three season set or doubled up below a hammock for winter use. This will allow one to use an exhisting bag as a top quilt, thereby achieving four season capability at no extra cost, a nice feature.

To our knowledge no other sleeping gear maker is using Omni-tape, or what is commonly called no snag Velcro.

While there are multiple makers of snake skins we were the first to design and make available Python Skins - Snake Skins on steroids. Large enough to hold the hammock with attached nest and up to an 8x10 silnyl tarp.

Our silnyl compression/stuff sack are an original design incorporating aspects of a paddler’s roll-down sack, compression sack, simple grab handles, and quick thread "d" rings in lieu of heavier ladder latches. At 1 oz nothing compares in weight and function.

All of the above seems to be a lot more like leading in design than following.

There are lots of ways to tackle this backpacking hobby. None of them are necessarily right or wrong unless it’s something that is going to endanger lives.

[sierraDoug]

[QUOTE=gardenville]
To the question about setting up a Cat Tarp like/or as an "A" Frame. If I had a Cat Tarp with a short ridgeline (both my Tarps have a ridgeline of about 10') and sides that were 5' or 6' or so long from the ridgeline the Trap would look like an "A" Frame. You would have to attach the ridgeline high enough so the long sides just reached the ground. I would want to connect this to a tree.

I think you took my "A" frame description differently than I had in mind. I didn't mean steep like the letter "A". I just meant set up with a ridge line (versus "flying V" or some other shape).

To quote Peter Pan, "The fact remains, catenary ridge lines are a simple geometry problem and there is an optimum angle to pitch a tarp with a catenary ridge."

That's what I can't quite tell from the photos I've seen on the web. If you splay the side out and pitch the cat tarp low do you lose the tautness you had at "the optimum angle" of pitch? Looking at the photo linked below with one side up like an awning makes this seem OK... that is, it doesn't get too slack or sloppy.

See:
http://www.gossamergear.com/cgi-bin/gossamergear/Spinn-Shelter.html

What do you (Gardenville, and Peter Pan) say to that?

[sierraDoug]

I clicked on the button on Gardenville's post, but I didn't end up with the cool recessed box look. How do you do that?

Thanks in advance. :o

[gardenville]

[QUOTE=gardenville]
To the question about setting up a Cat Tarp like/or as an "A" Frame. If I had a Cat Tarp with a short ridgeline (both my Tarps have a ridgeline of about 10') and sides that were 5' or 6' or so long from the ridgeline the Trap would look like an "A" Frame. You would have to attach the ridgeline high enough so the long sides just reached the ground. I would want to connect this to a tree.

I think you took my "A" frame description differently than I had in mind. I didn't mean steep like the letter "A". I just meant set up with a ridge line (versus "flying V" or some other shape).

To quote Peter Pan, "The fact remains, catenary ridge lines are a simple geometry problem and there is an optimum angle to pitch a tarp with a catenary ridge."

That's what I can't quite tell from the photos I've seen on the web. If you splay the side out and pitch the cat tarp low do you lose the tautness you had at "the optimum angle" of pitch? Looking at the photo linked below with one side up like an awning makes this seem OK... that is, it doesn't get too slack or sloppy.

See:
http://www.gossamergear.com/cgi-bin/gossamergear/Spinn-Shelter.html

What do you (Gardenville, and Peter Pan) say to that?

I think I have some pictures of my Moss Cat pitched like you are asking about. I will look for them. The Moss Tarp was created with a CAD program and I think it will do what you want. The old Moss web site talked about the Cat design idea way back in time. Moss still makes things but now they are really big convention show like shelters. I will try and find the web site and post it. I also will try and find my pictures and add them to my Gallery. If I can't find the pictures I will set up my Moss Cat tomorrow in my backyard and try what ever you want me to and see if it works or not. This is research and I love research. I just need to be real clear as to what you want me to try.

I have added 6 pictures to my Photo Gallery here of My Moss Heptawing Cat Tarp. See if any of the pictures show what you are asking about? If not explain how you want to see the tarp setup. I will try and put the Moss Cat up that way and take some pictures.

[peter_pan]

SierraDoug,

Clearly the cat tarp can be made taut. If you design it for a few specific applications it should do what you want. I agree with the comments that the "A" can generally be set up steep or flatter, through a range that is usable. This is, in part, due to the flexibility and stretch ( perhaps "give" is a better descriptor than stretch ).

Many inexpensive flat tarps are not made with the main seam on the ridge. While this saves material and thus money it causes sloppy pitches and gives the flat tarp a bad image. Flat tarps with the seam on the ridge pitch considerable better. When drawn taut they begin to approximate a minor cat cut of 1-2 inch drop in say 10 feet.

Because the Cat ridge tarps have the seam on the ridge by definition they are going to be taut in a normal routine of pitches. Ridge seamed tarps are also stronger by design. Whichever design cut approach you settle upon, I recommend a ridge seam.

One final note. Carefully consider how much drop to put in any catenary cut. We had arguably better results, and the seam was easier to sew, with a drop of 3 inches in 10 feet than a drop of 5 inches in 10 feet. There may be a few other opinions on this out there. Recommend a search, seems we had a thread, or at least discussions, on this point 6-10 months ago.

Good luck with your project…post some pictures when completed.

[Youngblood]

...One final note. Carefully consider how much drop to put in any catenary cut. We had arguably better results, and the seam was easier to sew, with a drop of 3 inches in 10 feet than a drop of 5 inches in 10 feet. There may be a few other opinions on this out there. Recommend a search, seems we had a thread, or at least discussions, on this point 6-10 months ago.

Good luck with your project…post some pictures when completed.

I don't remember the discussion about how much drop to use. I used 5 inches for ten feet on mine after I studied photographs and pulled catenary curves into my flat tarps in my backyard. Since my cat tarps where almost 11 feet long, that worked out to about a 6 inch drop. Sewing the catenary curve is difficult, enough so that it got me rethinking what seam to use and how to implement it. I have a few ideas that I haven't done anything with, but would give them more thought if I were to build another one. Sewing the catenary curve into the ridgeline is not a trival matter and like Peter Pan pointed out, the more the drop the more difficult that it will be.

Having done a few, I am convinced that there are seams that are more 'cat friendly' than others and that the process and implementation is very important. It makes one want to 'back up' and rethink exactly what the purpose of the seams are and then factor in the characteristics of the catenary curve so that it is a more manageable task. If you hot cut silnylon and seam seal the edges with diluted silicone adhesive, do you really need to be concerned with exposed edges of fabric?

Youngblood

[gardenville]

I used an Army poncho a lot for a simple tarp. I was able to tie onto the center/hood and tie it over head to a tree. I could then pull it tigher than if I had just used it like a normal flat tarp. This worked great when you had a tree.

I bought the Moss Heptawing Cat in the early 1990's and loved what I could do with it. The only concern I now have is that it weighs 23oz. My "large" size - Mac Cat - which is made great is only 12.6oz without guy lines, stakes etc. I don't know how Brian sews his Tarps but mine is done as good or better than the Moss Tarp.

If my sewing ever gets up to it and I want to try and make another Cat Tarp, I would trace a pattern from the Heptawing. As for now any new lighter tarps in my future will be made by Brian if he will do it.

I think the Cat Tarp design lends itself great to a Hammock.

[sierraDoug]

Gardenville (and everybody),
I realized that someone in a hammock can be close under a tarp (good for rain protection) and still have lots of ventilation. I'm sticking to the ground (after trying a hammock). A flat tarp can be set up with all four sides close to the ground if needed for blowing rain protection. A cat tarp seems to need to be set up with open ends. At least the Oware or Mac Cat type designs.

Any agreeing or disagreeing thoughts on that?

[sierraDoug]

SierraDoug,

Many inexpensive flat tarps are not made with the main seam on the ridge. While this saves material and thus money it causes sloppy pitches and gives the flat tarp a bad image. Flat tarps with the seam on the ridge pitch considerable better. When drawn taut they begin to approximate a minor cat cut of 1-2 inch drop in say 10 feet....

Whichever design cut approach you settle upon, I recommend a ridge seam.

Peter Pan,
That's great info and advice. I didn't know a ridge seam had any advantage. Somewhere I even read that it should be avoided (to keep leaks out, maybe?). I figure you know what you're talking about since you make tarps (etc.) for sale.

Any thoughts on my last post about flat tarps being more able to have all four sides set close to the ground... and cat tarps needing to be set up with the ends open?

Again, thanks for the help.

[gardenville]

Gardenville (and everybody),
I realized that someone in a hammock can be close under a tarp (good for rain protection) and still have lots of ventilation. I'm sticking to the ground (after trying a hammock). A flat tarp can be set up with all four sides close to the ground if needed for blowing rain protection. A cat tarp seems to need to be set up with open ends. At least the Oware or Mac Cat type designs.

Any agreeing or disagreeing thoughts on that?

This was posted to another site a little while ago. I like the "flip-beak" thing on the front of (what ever it is). I have an OR Advanced Bivy that has a flip thing sort of like that. I can pitch my Moss Cat on the ground (really about touching the ground) at the back and as close or high on the front as I want it. Something like a beak would close the front like the Shires thing does.
----------------------------------o------------------------------------------------
From Henry Shires:
"Just wanted to let you all know that we have some new options available on all Tarptent models.
Tarptent Extended Floors: http://www.tarptent.com/extendedfloor.html

Cloudburst Extended Beak:
http://www.tarptent.com/cloudburstextendedbeak.html

All models with all options are in stock.
Thanks.
Henry"

[Youngblood]

... My "large" size - Mac Cat - which is made great is only 12.6oz without guy lines, stakes etc. I don't know how Brian sews his Tarps but mine is done as good or better than the Moss Tarp.

If my sewing ever gets up to it and I want to try and make another Cat Tarp, I would trace a pattern from the Heptawing. As for now any new lighter tarps in my future will be made by Brian if he will do it.

I think the Cat Tarp design lends itself great to a Hammock.

I haven't heard much out of Brian lately, but I didn't think the tarps that he made had a catenary curve on the ridgeline of the tarp. I thought his catenary curves where on the edges only. Does your Mac Cat tarp have a catenary curve on its ridgeline?

Youngblood

[gardenville]

I haven't heard much out of Brian lately, but I didn't think the tarps that he made had a catenary curve on the ridgeline of the tarp. I thought his catenary curves where on the edges only. Does your Mac Cat tarp have a catenary curve on its ridgeline?

Youngblood

Youngblood, I just added 2 pictures of my MAC Cat Tarp in my Gallery. Take a look and let me know what you think.

[Youngblood]

Gardenville,

I looked at the photos. I have seen photos before that Brian has posted at various places and sometimes he had pulled a catenary curve along the ridgeline when he deployed the tarp and sometimes he didn't. You have a catenary curve in the ridgeline, is that made into the tarp or pulled into it? As we all know, what matters is if it works for you. Are you happy with it?

With my flat, rectangular tarps, I could pull a catenary tarp in the ridgeline but I had to pull quite a bit to get it to stretch enough and I think I may have had to use panel pullouts... at least on the wider tarp. I wasn't happy with them but I am with the ones that I make with a catenary ridgeline.

Youngblood

[gardenville]

Gardenville,

I looked at the photos. I have seen photos before that Brian has posted at various places and sometimes he had pulled a catenary curve along the ridgeline when he deployed the tarp and sometimes he didn't. You have a catenary curve in the ridgeline, is that made into the tarp or pulled into it? As we all know, what matters is if it works for you. Are you happy with it?

With my flat, rectangular tarps, I could pull a catenary tarp in the ridgeline but I had to pull quite a bit to get it to stretch enough and I think I may have had to use panel pullouts... at least on the wider tarp. I wasn't happy with them but I am with the ones that I make with a catenary ridgeline.

Youngblood

I really love my Digital camera. I took a few pictures and posted 3 of them to my Gallery. I hung both tarps from the same place on each tree. You can be the judge. Interesting. I have always know the Moss had a Cat ridgeline. It is very easy to see when laying out flat.

As for the Mac Cat, we know it takes on a Cat Ridgeline, but it may be how the guy lines are used. I don't know. I am very happy with it.

[Youngblood]

...As for the Mac Cat, we know it takes on a Cat Ridgeline, but it may be how the guy lines are used. I don't know. I am very happy with it.

Great... can't argue with that.

Youngblood

[gardenville]

I'm looking into making my own tarp. A flat design seems to have more options of how to put it up, and it's simpler to make. Do you see any definite advantage to one with a catenary ridge and edges? Frankly I like the look of good ol' Ray J's design with the beaks. Any experiences with this or other tarp designs?

I want to come back up to your basic question. I have been looking back over all the links posted with this thread. I had never really looked at Henry Shires web site. I found a "Do-it-yourself" tarp project.

http://www.tarptent.com/projects/tarpdesign.html

The design is old I think but the method in which he makes the tarp might be worth looking at. It is a way to do something and may provide some construction ideas. I like the way he uses the "beak" idea for one. The concept isn't new but the way he is using it I think might be.

The neat "quote" box comes from (I think) but "MacGyver" has not approved this message. I click the "quote" word in your "message box". Then I write. Then I click "Preview Post" box and look at the message. At this point I can see the neat "Quote" box. If I list a web site URL I click on it to make sure it works. When I am done I click "Submit Reply".

[Youngblood]

I followed Gardenville's lead and looked back over the postings on this thread.

I took photo's last spring of my biggest catenary tarp set up on the ground with two different pitch angles, both use the same ridgeline height and one has the sides raised about 8 inches and the other has the sides pretty much to the ground. This large tarp is about 130" long by 120" wide and it has two panel pullouts on each side. The panel pullouts are used when I try to change the basic shape of the tarp to what resembles a 'hammock tarptent' and aren't needed to keep the tarp taut in an A-frame configuration. I used four guylines on each side and the placement was determined by what I was trying to accomplish with the 'hammock tarptent'; however, after it was all done, it seems that they may be where I would want them if I was just using it as an A-frame tarp. (There are some things about the stretch characteristics of silnylon that I am only just beginning to appreciate.) One other note, about the width: the 120" width is basically along the edges; the catenary ridgeline that I used removes about 12" of material in the center of the tarp along the width and gives the tarp a three dimensional aspect... so in some photos it may not look as taut as it really is. If there is interest, let me know and I will try to upload some of these photos.

Youngblood

[peter_pan]

SierraDoug and all,

I looked at Gardenville’s pictures of the Mac Cat and can’t tell if the ridge is cat. Note, the high angle of tie to the tree. As stated before it is possible to get a 1-2 cat like drop on a flat tarp with a good ridge seam. Looking at these pictures reminds me that a flat tarp with 5 side loops that is secured by loops 2 and 4 will draw down much like these photos. Of course the ends will flap, if not secured. But they can be brought in to the centerline, if the pitch is not too flat, and pegged to close off the ends. Take a sheet of paper and fold it to model this point. Better yet use graph paper. (Believe what is described here is similiar to Youngbloods big tarp hammock tent if you size it as large and add tieouts.)

To your question of coverage, recommend you do the math. Compute the areas based on whichever models you are considering. Recognizing that the height of pitch will produce angle(s) which reduces coverage. Model them then ask yourself if you like the suggested answers. On a low wide pitch it seem to me that the square or rectangular tarp give better coverage as the areas of the side catenary cuts are not lost.

Another approach: for similar size tarps say an 8x10 and a catenary with a 10 ridge seam model, you will need the side measurements as well, draw them each on the graph paper, overlay the cat on the rectangle and ask yourself which coverage/design you like and which will support your anticipated preferred use. Put a scale model of your silhouette and gear under the tarp models and use some long thin items ( kabob sticks?) to model rain angles and reexamine the issues. You should find the results quite interesting.

[Youngblood]

Peter Pan,

In an A-frame pitch, I think the square foot coverage is pretty much the same if you use a catenary ridgeline tarp versus a rectangular tarp with panel pullouts. I would propose that the fundamental tradeoff concerning size is number of pullouts (especially panel pullouts), guyline and stakes versus interior volume. What I have found is that the catenary ridgeline reduces the number of pullouts (especilly panel pullouts), guyline, stakes AND interior volume. What do I mean by interior volume? Well, that material you removed to form the catenary ridgeline causes the tarp to drop along the center of the tarp... with a rectangular flat tarp, you would use panel pullouts and raise the sides outward to pull the tarp taut, so you have a net increase in interior volume as compared to the catenary ridgeline case. It reiterates the point that with a lot of design issues, it is not always a win-win situation... with a lot of them it is a tradeoff and you should select the ones that best suit you.

Youngblood

[TedB]

I had fun building a full scale model (http://www.whiteblaze.net/gallery/showphoto.php/photo/5208/size/big/password/0/sort/1/cat/500/page/1) of a catenary cut tarp using plastic and duct tape. Debating the pros and cons is nice, but rolling up your sleeves and experimenting is even better. Hope to make the real one sometime this fall.

[Youngblood]

I had fun building a full scale model (http://www.whiteblaze.net/gallery/showphoto.php/photo/5208/size/big/password/0/sort/1/cat/500/page/1) of a catenary cut tarp using plastic and duct tape. Debating the pros and cons is nice, but rolling up your sleeves and experimenting is even better. Hope to make the real one sometime this fall.

That's pretty slick, I like it. I haven't tried beaks before. I used drawing software (Visio) to model my first ones and cut and taped scale models from 8.5"x11" paper like Peter Pan suggested. I found that some things worked differently that what I thought they would... it was a good exercise and saved me some problems.

I am going to go ahead and upload a series of photos, I think it will help show some of the things I have tried to describe.

Youngblood

[Youngblood]

There are 10 photo I uploaded. I felt it was necessary to show why I selected the pullouts. I think this will take you the first photo of the series:
http://www.whiteblaze.net/gallery/showphoto.php/photo/5217/password/0/sort/1/cat/500/page/1 .

Youngblood

[peter_pan]

Agree with Youngblood on the value of lift tabs or pull outs... They make a nice addition for either ridge design...generally good improvements on volume and tautness.

Nice model, TedB. Your model reminds me of a boy scout troop that hiked the C&O canal regularly and each two scouts were required to make their tarp out of 3 mil plastic and duct tape. Duct tape will work as lift tabs also on the plastic. Oh, the simple life.

[brian]

Sorry about the recent lack of communication, as I have had several projects in school which have kept me completly at a lack of time.

My MacCat tarps do not have a catenary curve in the ridgeline. As Peter Pan stated, having the tarp pulled tight often makes the tarp form a slight catenary curve, as long as the tarp has a ridgeline seam, which mine do. The force of the tieouts pulls at about a 25-30 degree angle, effectively pulling down the center seam.

For more pictures, please visit my new (and permanent) website at http://www.outdoorequipmentsupplier.com/maccattarps.htm

Brian MacMillin

[gardenville]

Sorry about the recent lack of communication, as I have had several projects in school which have kept me completly at a lack of time.

My MacCat tarps do not have a catenary curve in the ridgeline. As Peter Pan stated, having the tarp pulled tight often makes the tarp form a slight catenary curve, as long as the tarp has a ridgeline seam, which mine do. The force of the tieouts pulls at about a 25-30 degree angle, effectively pulling down the center seam.

For more pictures, please visit my new (and permanent) website at http://www.outdoorequipmentsupplier.com/maccattarps.htm

Brian MacMillin

Hi Brian, Your web site looks good. That first Tarp looks just like mine. I am sure happy with mine. I have posted several pictures of the "Lighter/Larger" tarp you made for me. I have it set up in my backyard now as San Antonio is a little cooler for a few days and I am testing my Down Air Mattress tonight. It will not be that cold but I want to see how warm it feels.

I took a few pictures of my tarp that shows a real nice curve in the ridgeline. It surprised me but I would say it is more than slight. We had a lot of rain and that may have been the reason for the curve.

[sierraDoug]

Peter Pan,

In an A-frame pitch, I think the square foot coverage is pretty much the same if you use a catenary ridgeline tarp versus a rectangular tarp with panel pullouts. I would propose that the fundamental tradeoff concerning size is number of pullouts (especially panel pullouts), guyline and stakes versus interior volume. What I have found is that the catenary ridgeline reduces the number of pullouts (especilly panel pullouts), guyline, stakes AND interior volume. What do I mean by interior volume? Well, that material you removed to form the catenary ridgeline causes the tarp to drop along the center of the tarp... with a rectangular flat tarp, you would use panel pullouts and raise the sides outward to pull the tarp taut, so you have a net increase in interior volume as compared to the catenary ridgeline case. It reiterates the point that with a lot of design issues, it is not always a win-win situation... with a lot of them it is a tradeoff and you should select the ones that best suit you.

Youngblood

Maybe it's possible to make a cat tarp... with pull outs to use as an A frame . It could be set up with just a few stakes in the usual cat/taut way. Like this...
http://www.owareusa.com/Cattarps.html

Or it could be set up using the pull outs to create more interior volume. Like this, only with a (slight) cat cut to the ridge and long edges...
http://www.ray-way.com/tarp-nettent/index.shtml (skip top photo).

And beaks could be added or not. I don't want to waste a big sheet of plastic to make a model. I'll have to try a scale model. This is cool!
:jump

[Youngblood]

Just some thought.

With enough tie outs, you can configure a tarp into a lot of ways... if you have the skill, guyline, stakes(?) and time. I've tarped in the past but was never particularly skilled at it and I have never used a tarp with beaks. I always preferred using a longer tarp (8' wide x 10' length) and fashioning some type of door with plastic, my backpack/packcover or my umbrella if I really needed to. Some folks swear by the beaks, but when I look at them they look like they interfere with entry/exit, are something else to tie off and I don't think they would help condensation issues. By hey, its a tradeoff type thing and like I said, I have never used them.

Side (panel) pullouts require more staking out and more guyline that has to have some significant length. More guyline, in general, means more hassle. Don't forget about the hassle factor, it might count more than you realize when you have to mess with it day after day.

Youngblood