My First Pyramid Shelter – 9x9x5' – Cat Curve Feedback?

[Kyle]

Just finished tracing out a cat curve for the diagonal of my 9x9x5′ pyramid shelter. It ended up being about a 96″ chord length, and I chose a 3″ max deflection. Material is silpoly pu4000. Was wondering what other people have chosen for this material, and size shelter. The silpoly seems pretty stiff, even at 20x20d…

 

Curve is based off that spreadsheet from Jerry:

Sorry for the kinda crummy shots, as you can see, I’m working in tight quarters here…

[Jordo _99]

I go with an offset of 1/4″ to 1/2″ per foot depending on what the impact is. I went with a 2″ offset over a 96″ seam (1/4″ per ft) from ground to peak and I have a tight pitch (https://backpackinglight.com/forums/topic/finished-my-tipi-hot-tent-picture-heavy/)

You can certainly have a more aggressive curve but it ends up cutting into the head room, which I why I stuck towards the bottom of my range.

…going from 3″ to 2″ is going to gain a fair bit of headroom for you.

 

[Kyle]

Nice tipi, and thanks for the info! I’ve heard that as the angle of the ridge decreases (ie a pyarmid has a 90 deg ridge angle, a 6 sided tipi has a 60 deg ridge angle) the depth of the cat curve can be reduced, with a similar level of panel tightness being achieved. Any thoughts / experience on this matter?

[Jordo _99]

That does make sense…I still expect that with a 60″ tall mid you’d be fine with 2″ offset so long as your seams are following the curve closely (ie, a curved line…not a wavy line that follows a curve). My tipi is ~80″ so the ratio is still pretty similar after accounting for all of this

[Kyle]

Cool – thanks for the info. I think I’ll go with 2″, and I’ve also decided to go with silpoly 1.1oz, instead of silpoly pu4000. Not looking forward to re-doing all the cat curve measurements, though =P

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