Tarp Question??

Rectangular

I just finished sewing a 5'x8' poncho-tarp and played around with pitching it. I really like the flexibility of many pitching options over the limited A-frame variations my cat-cut tarps are capable of. I was able to set up my flat tarp with 4 stakes and 12' of guylines. My cat tarps take at least 6 stakes and 20' or more of guyline. Granted I couldn't get as tight of pitch the first time with the flat tarp, but with time and practice I feel that will come.
I would say that a basic rectangular tarp will give you more options than a wing-style tarp. I know I am plenty happy with my basic rectangular and tapered tarps.

Adam

I prefer the flat tarps as well. 5×8 or 10×10 or so for two people. I like because of its versatility over a cat shaped tarp, which only allows you one style of pitch the A-frame. With a rectagular flat tarp you have many pitching options for the what ever ocasion/weather system may come you way.

Yep, flat tarps are great for optional pitches. On a 5 night trip, I set mine up a differently each night.
I usually only set up A-frame when I expect rain – other then that, it's typically in a lean to config.

>>I usually only set up A-frame when I expect rain – other then that, it's typically in a lean to config.<<

That's funny, I usually pitch a lean-to when I expect rain.

Eins

nm

Ok, i got my 8×10 square tarp White Lightning by Granite Gear it looks good, however, there's a big seam down the middle with tension tape, so i am wonder if/how to seal it up. I am used old fashioned flat seams. So to i seal it from the inside or from the outside?

do you recommend a sealer for this material??

thanks!
mpd

What do people think about the GG White Lightning (or other similar designs) as an alternative to tarps with cat cut ridgelines? They claim that because the sides are cat cut, you can achieve a very taut pitch (similar to the ridge being cat cut). If thats true then the user could still have the benefits of both. Right?

Advantages to each. If you have a curve on the hem, it is
more difficult to get a good seal against the ground in
the wind. If you have a very large tarp, there is a lot of
fabric to stretch, so you may need curves on the hem and
ridge. Or some center tie out to do the same thing and give
more headroom.

Standard practice is to thin hi-quality silicon caulk (clear) in mineral spirits and paint it onto the seam with a foam brush. Works great.

Use approx 1 part caulk to 2 or 3 parts thinner. Be prepared to mix for awhile; it takes some time and stirring to dissolve it. If it thickens before you're done, add more thinner and stir some more.

I don't believe that it much matters whether you seal the inside or outside of the seam – which ever can be done most neatly if there's a difference…

Cat cut: Previous commentor is accurate in saying that side catenary makes sealing the sides against wind difficult. In general, however, a cat cut reduces interior volume. You might consider the rectangular Ray Way type of tarp which uses side pull-outs. Not only do side pulls give a taut set-up and shed wind well, but they increase the interior volume significantly. That can be important when condensation coats the inside of the tarp.

Seam sealing: Silicone sealants do not thin properly with mineral spirits, contrary to all recommendations in their favor. They merely form a slurry that is weak and patchy when cured. The most reliable sealant is a silicone resin that is formulated to be thin to begin with. McNetts Silnet is widely available. Cheaper and more durable is Permatex Floable Silicone Windshield Sealant, available at any automobile parts store – twice the amount for half the price of McNett's. It is the right consistency for seam sealing, penetrates thread holes, saturates threads, gets into seams, and stays where you put it. While you are in the auto parts store, buy a pack of plastic body squeegees – spreaders used on Bondo. They are really good for scraping up any vagrant sealant. Otherwise, you will find, the sealant – any sealant – will add an unexpected amount of weight.

The key thing in getting good seals is to clean the seams thoroughly with alcohol. Really scrub it with a soft cloth, then rinse it again and let it dry completely before applying the sealant. All fabrics have manufacturing residue and often DWR. Any contaminate will interfere with good adhesion.

Thanks Vick. While I've never had any obvious issue with using the caulking / mineral spirit blend, I'll try the window sealant next time out.

>>"In general, however, a cat cut reduces interior volume."
Are you referring to just cat cut (CC) ridgelines or CC sides as well?

Tarps with slightly CC edges like the White Lightning surely don't look like they sacrifice interior space:

I'm going to echo about cat cut tarps on the ground about not being able to seal out the wind, although If your using them over a hammock, Say a MacCat or a Speer Cat Cut 8×10 or a JRB 11×10 then the fact that the tarp is cat cut is more in your favor as it aids in tarp pitch overall and helps reduce the overall weight of the tarp. Just a thought, but to your orginal question, I would take a flat tarp due to various pitch options open to you. If you can find one of each you can borrow, then you can find which one works well for you.

Space loss: All cat cuts reduce interior volume. The cat ridge may reduce it a little more, but both strategies do it.

And Kyle is right about using a cat tarp with a hammock. The cat tarp's taut surfaces shed wind much better than a square-cut tarp. I use a side-cat with two pullouts on each side for my hammock for that reason. The cat cuts are diagonals on the ends; the central section between pull outs is straight. The diagonal cat sections produce intersecting stress along the bias and give a good, tight set-up.

"Just a thought, but to your original question, I would take a flat tarp due to various pitch options open to you."
—Doesn't a tarp with cat cut sides give you the same flexibility in pitching as a flat tarp?

"Space loss: All cat cuts reduce interior volume. The cat ridge may reduce it a little more, but both strategies do it."
—Doesn't it seem like the only volume lost with cat cut sides is near the edges? That volume (or floor area, however you want to see it) is unusable anyways. Are you suggesting that the sides of an A-frame would bow in more with cat cut sides?