hexayurt tie downs

[mullenc525]

Hoping to build a hexayurt this year, and am planning to include a bunch of extra features.

One idea I had was an integrated tie down. A 24" x 2" x 1" thick board is glued into the bottom of each foam wall, centered. The board has a 0.5" hole in it vertically, and a semicircle cut into the foam above.The joint is reinforced by the edge taping which is applied afterward.

Once the yurt is assembled, the walls can be flexed inward a couple inches while a 3/4" rebar is pounded into the playa in the holes original position. There are female threads in the top of the rebar to accept a 3/8" bolt through the board, which is threaded in to secure the yurt to the playa.

Any thoughts? For those non-engineers, a 3/8" bolt can take over 3000 lbs tension, more than the rebar. I figure this is cleaner than either a rope halo or tape tie downs, plus the force is distributed onto more area over the foam boards.

Also planning to integrate LED lighting and wiring into the roof of the yurt, among several other features.

As a side thought, I am assuming a single swamp cooler per figjam: http://eplaya.burningman.org/viewtopic.php?t=33842 is satisfactory for cooling, with vents in the roof peak?

[Eric]

Why did I read this as "hexayurt the clowns" and suddenly get hopeful someone was going to offer me a hexayurt?

There's this old thread about hexayurts, and I'm sure some of our regulars with more experience in that area will be along soon.

[Captain Goddammit]

I think that sounds excellent.

[Canoe]

I considered doing that, only instead of the half-circle, add a strip/block of wood to the bottom piece of wood, so it sticks out the side and you can hammer a bent piece of rebar right through the hole while the wall is in place. No need to count on bending anything out of the way. Another way, was to route a channel in a 2x4 for the foam-board wall to sit in (add a cut-out in that channel to the outside for rain water flow, so it doesn't fill and overflow to the inside).

But, in a strong wind, the horizontal component of the guy-lines takes any awful lot of the force from the wind. Without guy-lines, the structure will be flexing more while it transfers that wind load to the ground. At what point will it no longer flex, but break?

I'd be inclined to still do some guy-lines, in case of Condition Alpha.

[burner von braun]

An interesting idea mullenc525. I do think you might consider, in addition to gluing, also taping the wood up to the foam wall also, for added strength. Still my instinct is that this method would give way before the standard anchoring methods would because you are relying on a small lower section of each wall to bear all of the forces, rather than accumulating the load across the entire roof, receiving support from the tension ring, and transferring it down to the stakes. It is all about that tension ring at the top of the walls. Having said that, your new idea might provide enough strength for what is needed. Better still, I see it as an nice improvement if used in addition to the standard anchoring method. The standard method would offset the wind forces, and your new method would keep the walls from bucking inward near the base.

[Canoe]

... It is all about that tension ring at the top of the walls...

Yup. To me the magic is the tension ring combined with the wrap over the roof seams that joins the tension ring, then into the guy-lines. Take an awful lot to convince me to give up taking those side wind loads to the ground through guy-lines.

In addition to the bottom wood piece, I also looked into using routed 2x4s for the vertical wall seams, so the wall panels would just slot into a simple wood frame structure: quick to setup, easy to reuse, no expensive bi-directional tape. Made for easy-up walls that didn't need the bi-direction tape, but still needed tape or weatherstripping in the channels for sealing (and another negative: more wind resistance). But no matter how I laid it out, I couldn't come up with anything that would allow mounting the roof panels anywhere near as securely as that tension ring, which the vertical wood seams interfered with.

[Elderberry]

... It is all about that tension ring at the top of the walls...

Yup. To me the magic is the tension ring combined with the wrap over the roof seams that joins the tension ring, then into the guy-lines. Take an awful lot to convince me to give up taking those side wind loads to the ground through guy-lines.

In addition to the bottom wood piece, I also looked into using routed 2x4s for the vertical wall seams, so the wall panels would just slot into a simple wood frame structure: quick to setup, easy to reuse, no expensive bi-directional tape. Made for easy-up walls that didn't need the bi-direction tape, but still needed tape or weatherstripping in the channels for sealing (and another negative: more wind resistance). But no matter how I laid it out, I couldn't come up with anything that would allow mounting the roof panels anywhere near as securely as that tension ring, which the vertical wood seams interfered with.

I agree.

[Captain Goddammit]

I wasn't clear whether the bolt-down anchors were meant to augment or replace having guy lines. I agree with everyone else, I'd still guy it, but the base anchors sound great.

[otakup0pe]

I have seen hexayurts where people add tie-downs to the roof pieces. They had simply bolted wood to the panels so it still broke down cleanly. Ended up with guy wires from the roof but without the rope halo or tape loops.

[mullenc525]

Good convo, I think I am going to go for it with no intention to guy it.

The reason I don't like the rope halo is it actually doesn't distribute the force over the whole roof, force is only applied where the rope is bent. I suspect it is entirely common for the rope to partly crush the foam in the region where the guy comes over the wall, since the tension force is distributed over only the rope width (perhaps 3/8" +-). Tape loops are partly better since they would be 6" wide and distribute the force better, but not very cosmetically appealing (as if a hexayurt is!)

I put some thought into the lateral resistance the guy lines provide to wind forces. In the case of my idea, 2 of the walls will be principally loaded in shear for any wind angles. Solid board of any type is terrifically strong in shear, and the structure is inherently rigid once anchored. Therefore I think the two shear loaded walls will have no difficulty resisting the wind forces.

Any comments on a single swamp cooler being sufficient?

[Canoe]

... rope halo is it actually doesn't distribute the force over the whole roof, force is only applied where the rope is bent. I suspect it is entirely common for the rope to partly crush the foam in the region where the guy comes over the wall,... Tape loops are partly better since they would be 6" wide and distribute the force better..
Any comments on a single swamp cooler being sufficient?

I thought rope halos weren't recommended, but the 6" tape over the top and joining with the tension wrap was. 6" tape to the tape loops and rigid handles to load the loop will not crush the foam.

Nice to suspect, but if this is your first hexayurt, be cautious about deviating too far from what is tried & true Playa-Tested©)'( for on-playa use.

If you're asking about Figjam's Playa-Tested©)'( swamp-coolers, the Endless Breeze fan used in the Box Cooler design has great flow, low noise, low power draw and three speed settings. But I'd suggest you ask FIGJAM about their suitability for your size of hexayurt, number of people going in and out, etc..
http://eplaya.burningman.org/viewtopic. ... 61#p945261

[Good]

So I'll be up front and say that I DO NOT have experience with yurts at burning man, but I DO like to think that I have a pretty good brain for the way that physics works.

The only forces you need to worry about will be horizontal, assuming that you can keep the bottom edges of your yurt on the ground. Therefore:

1) How much force does it take to resist the upward force from the wind trying to get under the edges of your yurt, and keep that sucker on the ground, and
2) How much force does it take to resist the horizontal force from the wind blowing on the giant, flat, 4x8 wall.

If we think of this as a physics problem in two independent directions, I think that covers everything.

A 'rope halo' will apply a downward force with varying degrees of even-ness depending on how far out your ties are staked. If the angle is steeper than the roof of your yurt (more than 30 degrees?) when you will have tension hotspots where the rope meets the edge of the roof. If they are staked further out, the hotspots decrease and instead the halo will be pulled straight down, and will behave more optimally... but that requires more overall area for the staking. Regardless of the tension, though, assuming that the rope doesn't stretch and the panels don't bend there is no way for the yurt to escape the hold, which makes this seem very secure laterally (in my mind).

Anchoring the base of the yurt to the ground means that there is a very strong resistance to wind getting underneath the panels and lifting them, which sounds great to me. However, the horizontal forces from the wind won't have any resistance from higher up - the wind forces will actually multiply at the base of the walls, due to leverage along the entire length of the panel (the height of the yurt).

Again, I don't see a reason not to combine the two - that seems like the sturdiest option. I don't have the math to say whether or not anchors would work alone, but I'm skeptical I look forward to hearing about your experience!
-Good

[Canoe]

...
A 'rope halo' will apply a ... you will have tension hotspots where the rope meets the edge of the roof....

The problems are already solved.
Go read how hexa-yurts are constructed. Hint: a rope halo is not what's recommended. Rope tie-downs do not touch the sides or top of the foam boards. They tie into "handles" made from the bi-filament tape. The tie-downs used provide both a vertical component and a horizontal component. Both are required.
Strongly suggest your first hexa-yurt the way they are known to work successfully on playa.

[maladroit]

I'll just point out that slamming a sledge hammer into the top of a threaded hole in malleable steel is not going to make you happy when the time comes to thread in that 3/8" bolt. And...3/4" rebar will mushroom out a bit even when it hasn't been converted to a hollow tube at the impact point.

[lucky420]

...
A 'rope halo' will apply a ... you will have tension hotspots where the rope meets the edge of the roof....

The problems are already solved.

Strongly suggest your first hexa-yurt the way they are known to work successfully on playa.

Completely agree. Why reinvent the wheel. Yurts are great structures and following Vinny G's plans, you can't go wrong.

[mullenc525]

Yurts been built with anchors nearly as described. Only change is I have 12 16" long 1" aluminum angle stakes to attach to the wooden boards. The stakes have a lateral hole in the top which will allow them to be screwed to the reinforcement boards once they are pounded in. The reinforcement boards were attached to the rmax with polyurethane adhesive and bidirectional tape and aren't going anywhere.

Not expecting any problems (source: professional mechanical engineer), will update if it doesn't turn out excellent.

As a side note, built the roof in two folding sections and walls in 3. Beveled all necessary edges at 15 and 30 degrees so our hinges are tight and there are no gaps at the seams.

[Elderberry]

...
A 'rope halo' will apply a ... you will have tension hotspots where the rope meets the edge of the roof....

The problems are already solved.

Strongly suggest your first hexa-yurt the way they are known to work successfully on playa.

Completely agree. Why reinvent the wheel. Yurts are great structures and following Vinny G's plans, you can't go wrong.

Yup.

[mullenc525]

Yurt and new tie downs were a huge success. Turns out 16" of 1" aluminum angle is overkill. It was a huge challenge to pound in and remove. We only used two stakes and the yurt wasn't going anywhere, it was very very stiff.

Gets my professional engineers stamp.

Single figjam cooler was marginal but comfortable enough. Bevelling all the edges and pre taping to fold out was worthwhile. We had it up in well under an hour with three of us.

[unjonharley]

Didn't see it mentioned here yet.. One hexayurt had a cargo net over it and tied down. A few bucks at an auto store will do it..

[Elderberry]

Yurt and new tie downs were a huge success. Turns out 16" of 1" aluminum angle is overkill. It was a huge challenge to pound in and remove. We only used two stakes and the yurt wasn't going anywhere, it was very very stiff.

Gets my professional engineers stamp.

Single figjam cooler was marginal but comfortable enough. Bevelling all the edges and pre taping to fold out was worthwhile. We had it up in well under an hour with three of us.

Did you take any pictures on playa? If so, can you post them here?