Incorporating 'Cat Curves' into tarps/shelters

[Roger Caffin]

It worked for me.
Cheers

[Sam Farrington]

Jerry, re:
“With a tunnel tent all the edges are on the grain so no need for a cat curve? Or a pup tent or A frame tent. *** Maybe that’s pushing too far the theory that only edges on the bias need to be cat curve.”

If the hoops are identical, or close to it, and there are several as with Roger’s tents, I can see where a cat-cut might not be needed. The fabric panels need to be cut on the grain, otherwise, they will be taut alright, but cave a lot between the hoops. For an A-frame, like an A-shaped tarp, a cat-cut ridge seam is needed for a taut shape, even if the material is less flexible like DCF, as attested by the many tarp projects posted on BPL. So would not agree with the theory you mention.

[Sam Farrington]

Roger, re:
“The advantage of the two-peg vestibule is that it never relies on tension in the fabric on one axis to create tension on the other axis, with the door open or closed. That is what is causing the wrinkles in your 1st photo.”

I’d just say that the fabric over the door is wrinkling, because much of the tension on it is relieved when the door is open.  Maybe great minds think alike, but simple minds are more contented.

The discussion and diagram of your two years in the making fabric panel is fascinating and informative, but might scare me or Jerry away from making tunnels. But at least one issue seems settled; namely, that your tunnel designs do not require catenary cuts like those produced in your article about plotting points. Luv your digression about cryptography and the NSA (National Security Agency?); but if we need them for our tents, we will surely end up disappointed.

So as mentioned earlier, once the tunnels are modified with canted poles, with poles of different heights, or with elbowed poles, those wedded to the KISS principle may be put off. The answer, I think, is to keep the main canopies of our projects simple enough to require only good old rectangles, and limit any fussing about to the vestibules. But suppose this might not help Jerry much with the half pyramid.

One KISS warning arises from an oft posted photo of a tunnel made from a Gerry tarp, with zero alteration of the rectangular fabric panels:

I can attest that without the side guys, this tarp-tent was not taut on top.  As with photos on BPL of A-shaped tarps with pools of water collecting on top, there was caving on the roof.  Could the catenary process in your article address this as well as it would for an A-shaped tarp?  Or would a middle hoop, or a middle hoop with a slightly elbowed angle on top be advisable instead?  Either way, were I to make one of these today, would use the Epic Malibu for a breathable single wall canopy, and put on some two peg vestibules at each end.  In which case, might still be using the tarp today and have avoided all of the tent conundrums.  Under 3 lbs for a solo – not bad for those days.

[Roger Caffin]

@Sam

Just remember that Epic Malibu leaks at quite a low HH. Tested.

As for KISS – the simplest is to stay at home. Really!

Cheers

[Sam Farrington]

Roger,
Yes, you tested some Epic Malibu for me at one time. It was OK up to around 1500mm, then leaked quite a bit. A number of contributors to BPL, citing various authorities, have stated that 1500mm is the bare minimum for what can be considered waterproof. Hovering around the bare minimum might explain why some found it waterproof and others did not. I think you once opined that its water resistance was akin to ‘surface tension.’ If so, probably a little bit of soiling would likely destroy the water resistance. The manufacturer, Nextec, said that the ‘encapsulated’ coating was silicone based. It might be interesting to spray some Epic Malibu with a DWR treatment containing silicone and see how the water resistance is affected. Is there a simple home test for breathability or vapor permeability?

I guess it is the Malibu I’ve got sitting useless in the basement that continually tempts me to think of a use for it. Was impressed when put a hose nozzle set to highest pressure up against it, and there was no penetration. Despite my cautioning, a BPL member bought about half of what I had to make a rain suit. She never got back to me, as requested. Maybe because she got drenched?

Though I do think your experience with Epic tops was with an Epic different from Malibu, which was designed for tents. Before Wild Things went military, they had an outlet here for years, and I bought a couple Epic treated pullovers on sale that proved worthless in serious storms. But enough, the lessons have been learned, and you are right.

“… KISS – the simplest is to stay at home.” Yes, but if a reliable shelter is relatively easy to make, and make well, it should appeal to readers of this forum, judging from the proliferation of threads and posts about pyramids and A-framed tarps.

[Roger Caffin]

The data sheet I got from Nextec for the Malibu only claimed >400 mm HH. That is not enough for rain imho.
But I did make a nice ski/wind jacket out of it and some slightly heavier Epic (Arete?) for the shoulders. It sheds the wind and the snow very well.

Summit of Mt Jagungal, Kosciusko NP

Cheers

[Sam Farrington]

Roger,
Re: The data sheet I got from Nextec for the Malibu only claimed >400 mm HH. That is not enough for rain imho.

It may be a matter of trivial pursuits at this point, but the fabric formerly used by Black Diamond for its single wall tents was named “Epic Malibu,” and was sold as yard goods by several suppliers. It has a faded yellow color. At first, it was used by BD without calendering, but later was calendered on one side. I bought both types. As I mentoined, you tested a sample of it for me and advised 1500mm HH. So I think there must be some confusion with respect to the data sheet info. There have been many outdoor fabrics treated with the Nextec Epic process for a variety of uses, so it’s not surprising that confusion could occur.

[Roger Caffin]

Weird.
Don’t remember.
Mine was yellow too.

Cheers

[Jerry Adams]

I had a rain jacket from epic malibu

It worked okay for a while, then it lost all it water resistance

I think it’s susceptible to dirt/dust

[Sam Farrington]

Jerry,
That’s probably right. Black Diamond had a lot of complaints about leakage, and there were many on BPL and other websites. But many others said it worked OK. Your suggestion that it was contamination is a theory that fits the facts, and is in accord with Roger’s past observations. It’s time for me to clean out my fabric stash, and Epic Malibu is one that will go. I’ve a packrat instinct and hate to throw things out, but enough is enough. Will keep some of the materials if they are still in good shape and there is enough for a project, including tent floors, or prototypes not for use, but just to get pattern shapes right.

P.S. Did you try washing it in a non-detergent, like Atsko Sportwash? It’s interesting that some companies are still selling sleeping bags with shells with the Epic treatment. Talk about something that could get contaminated, rolling around on a tent floor.

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