Modifying Shape of Traditional Tipi / Mid Shelters With "Support Ring"

Thanks for sharing this Kyle….. looks very interesting.  I think the ring will not only allow you to have the peak lower but also increase the usable space inside the shelter.  I’m not sure spokes would be better than a ring though.  If you use spokes you would have to reinforce quite a bit the area where the spoke end makes contact with the wall of the shelter otherwise there would be a good risk of punching thru.  I think a ring would be better distributing the stress along the fabric.  Yes your spokes would save you a bit of weight (depending of how many panels / sides your mid has) but I think you probably can get away with a thinner ring than what you would need for spokes, so that may offset the weight difference due to the amount of material used.

Cheers

Here is a thread from 2012 on C Nugget’s Experience with it( and Richard Webster’s), photos included

Good point on the stress concentrations, Mario. Spokes would require some abrasion resistant material, but I think a 1-2 layers of 70D nylon with some rounded pole ends would work out. Ring kinda seems hard to make on a small scale, and looks like a pain to install, so I think spokes are looking nicer to me. So long as I keep it under 6 spokes, the weight should be closeish…

Thanks for the link, Link. Looks like there aren’t any specific complaints about the concept of the tent itself, just some issues with build quality, etc… Perhaps the most useful thing I saw was that setup in rain isn’t easy with the ring design. Makes me think some sort of built in internal spoke system may work better…

I’m trying to think about alternative ways to deploy the ring.  The MH tent system seems to work well to keep the ring / tent walls taut / snug but I wonder if it is really necessary.  Also the ring seems quite thick and overbuilt.

Perhaps one can make a ring out of the easton carbon 6.3 from quest outfitters  (I’m sure there are other / better options but this is one of the first hit I got when googled).  4 – 17″ sections would weight 2.2+oz, cost $17 and give you a ring with a 68″ circumference which I think would be a good size for this purposes.  Perhaps you can attach the circle with velcro tabs sewn to the seams where you join the different panels.

I would use this set up only when I expect calm conditions so I can have more usable space inside the tent, but when I expect windy conditions i would probably skip the ring and just pitch the mid as before.  (i.e this would mean the panes would be more slanted, bad for room space but good for wind deflection).

+1 for the ring idea.

I think spokes are going to break and bow out with the wind…in a bicycle wheel, the spokes are actually applying tension to PULL the rim towards the axle and not PUSH it. If they were done the other way around, the spokes would be prone to bending/bowing out but this is not the case when they pull the rim in to support it’s round shape.

Interesting idea

but, without the ring, for the same volume inside, the peak would have to be higher

the pole would have to be longer, and since it’s longer, theoretically it would have to be bigger around, so it would weigh more.

but that would be cancelled out to some extent by the weight of the ring.  Maybe the ring would weigh more.

the tent would be higher so it would require more fabric, but the width or circumference would be small so it wouldn’t make that much difference

the tent would stick up higher in the air so would catch more wind.  And the wind speed gets higher as you go up in height.  As a result, theoretically, you’de need a stronger pole and fabric.  But again, the width or cross section is small so it wouldn’t make that much difference

I dunno, you might save a little weight over-all

It’s definitely cool though, that a ring just supported on the tent fabric, without any attachment to the pole, would stay up so rigidly

I don’t think that an Easton FX pole could be bent and work with a small radius like the one discussed here.

Note that the hoop in Hoopla is made with pre-bent pole sections.

I went to the store in Vancouver WA for Tent Pole Technology

They bent Easton poles with a crude jig made of a circle of plywood.  Not as much radius as your hoop though

Maybe you could ask them for a pole bent to that circle

It doesn’t have to be a circle. A square or rectanglular pole structure would work. 90degree elbows are readily available. Maybe use trekking poles somehow (if your trekking poles are not needed as the main pole)

That’s a pretty good point John…I know I’ve seen 90 (square) and 120 (hexagon) degree bends and I’m looking at 125 and 145 bends at quest right now for their carbon poles, which should work for 6, 7 and 10 sided mids.

For anybody not wanting to do the math, here are the angles needed for different sized polygons:

4-sided (90) | 5-sided (108) | 6-sided (120) | 7-sided (128.5) | 8 sided (135) | 9-sided (140) | 10-sided (144)

I agree with Jerry that the support ring idea will not save weight for a smaller sized tipi but it does get get more efficient as the tipi gets scaled to larger sizes because of the height needed for those to work. Just looking at SeekOutside as an example, their 6p size is 8′ tall and the 24p tipi is 13′. Those aren’t exactly backpacking sizes but they’d definitely have a lot of potential for something like this.

A ring is also fairly weight efficient.

To create a ring of radius r, you’ll need a circumference of 2.pi.r, or 6.28 * r.

Whilst you could use four ‘spokes’, using a total of 4 * r, you’d probably go with six, so the ring gives hardly any additional weight, for a much stronger, simpler setup. Spokes of length r won’t give you quite the same enclosed space.

Circles are also strong, as they have no stress concentrating points.

An aside…

A circle is the shortest enclosing perimeter, for a given enclosed area… I figured this out once, whilst playing with windshield designs. For instance, a circle of radius 1 has an area of pi and a perimeter of 2.pi = 6.28. An equivalent area square has a side length of sqrt(pi), so total perimeter of 4.sqrt(pi) = 7.09. The more segments you add to the perimeter, the more efficient the perimeter to enclosed area. A circle being the limit case of infinite number of segments…

Great input from everybody as usual,  this is what makes BPL great.

When I saw Kyle’s original post I was thinking about a modification to an already built Mid. I thought by lowering the post a bit, it would give enough slack on the walls to insert the ring (or shape).  However, after playing a bit on sketchup it seems the tent would need to be built from the ground up to have any SIGNIFICANT gain in usable space from this design unless the material of the tent walls is VERY stretchy.

Here is the sketchup simulation:
Hexagonal base: 5′ sides
Original height: 5′
Lowered height: 4.5′  (i.e lowered 6 inches)
Sides of the ring: 18″

IMO not enough gain to justify the ring at the above specs.  A larger ring is needed to have any real impact on the usable inside space.

I met a gal on the PCT in 2014 who had a collapsible hula hoop (not sure what it weighed, but she said it was “light”).  Maybe that could be used as the hoop?  Also, the hoop could be attached on the outside of the fabric via small hooks — take a look at how the poles are attached in the Sierra Designs Flash tents.

Thanks for the detailed analysis, Marco! After thinking about it a little longer, it seems to me that the ring really isn’t buying you much, until you get to bigger volume tents… My gut (and the current design of shelters available) tells me the simplicity of the standard mid/tipi style shelter gives you enough weight savings to increase the height of the shelter a little bit and achieve the same performance results as adding a hoop. Also, without a hoop you don’t need to worry about horizontal seams taking vertical load and spreading open… One main drawback, though, will be not having a hoola hoop on the trail…