Mid Design Question

[Ryan W]

Hey there,

So I'm in the process of redesigning a new mid shelter, about 9 x 5 floorplan. I'll have 4 panels that will trapezoid shaped as the base of the shelter. These will join to a pyramid top via a horizontal seam across the entire shelter. This design was necessary to preserve the length of the shelter given the width constraints of the fabric I have.

My question is what should I do with my plans for a catenary cut along the ridgeline seams. I'll in effect have two ridgelines, about 65" and 18". Should I do a cat cut along the entire length (~80") and ignore the existence of the horizontal seam? Or should I only do a cat cut for the long base ridgeline seam 65" and leave the pyramid top as straight cut. Or should I…..? How does the new seam effect the need for a cat cut. Suggestions for max deflection also appreciated.

Hopefully this will work out as this is my first large sewing project besides simple flat tarps. I promise to report back.

Thanks

Here is a very basic sketch of my question

[Jerry Adams]

Do a cat curve over the entire 80 inches

Did you see the article http://www.backpackinglight.com/cgi-bin/backpackinglight/myog_silnylon_floorless_2-person_tent.html

Might have a few helpful ideas

2 inches deflection at the center would be about right

[Ron Bell / MLD]

Hi

I've made a few of these waterproof type shelters ;-) and I think if you use paper and ruler and then cut each side to proportional size 1 inch = 1 foot and tape it all together you will see the long sides might not need a triangle extension at all – only the 5' wide base sides would since it is longer.

Here is another hint: If the long sides are 64" wide raw material (no triangle extension) and the floor base is 9' X 5' a single 140cm trek pole will work.

Of course if you want it taller, then add triangle extensions to the long sides two but they will be a different height than the ones on the short sides.

Someone could come up with a long math equation to explain the relationships of all those variables and angles, but in 2min you can do it as a 3-D mock up that will pretty accurate.

Peace,
Ron

[Ryan W]

Thanks Jerry, I have read your pyramid article a few times. There were a few things I found a bit confusing, but overall it was very helpful. I think I just need to start putting things together.

Ron,

"I've made a few of these waterproof type shelters." Ha, ya that is a bit of an understatement! Your website might as well be my home page for how often I drool over your shelters! I have no expectation of producing such a quality shelter or saving much money with my MYOG foray, but I would like to develop the skills to be able to tailor and make a few unique gear items for myself.

My fabric is barely 60". I'll take another look at maybe tweaking the height a little to preserve primarily the length and secondarily the width. You are right in that I maybe able to get by with only an extension on the 5' base sides. Thank you very much for the hints.

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