Is this low-footprint tie down feasible for a canopy tent?

Question

I've got a canopy tent, and I'd like to see if I can reduce the footprint of the lines (and the chance that someone will trip on them).

From what I understand, the standard way to lay out the lines for a canopy is with the lines going out from the corners at a diagonal, like this:

This is nice and stable, but this quadruples the footprint from 10x10 to around 20x20 (assuming 45 degree angles for the line).

If I understand the math behind it, I can split the force applied by those lines across two other lines which run the same direction as the edge of the canopy, and it should be at least as strong (at the cost of using more rope):

If that is the case, then I should be able to swap the ropes around a bit, as long as there's still the same number of ropes providing anchorage in each direction, and I can move most of the ropes inside the footprint of the canopy - with the exception of the two front ropes, which would otherwise block the side of the canopy we plan on going in and out of:

While all that seems to make sense, "it made sense in my head" isn't much help if it turns out this sort of thing doesn't actually work. Does anyone know if this line configuration is feasible?

Answer 1

Your intuition about swapping the ropes around is not sound:

• As RBarryYoung notes in the comments, the pivot points change. In your third design, the tent could pivot 90 degrees such that the back ceiling edge falls onto the ground, and all lines would be slack. The same isn't true for either of your first two designs.

• As ruakh notes in the comments, the internal structure of the tent would be subject to compression rather than tension.

• I'd go further to say that most folding tents have the legs come together to fold up the canopy for storage. In that case, the tent is likely to survive a much larger load pulled toward the corners (it's extended as far as possible) but it may only have a very flimsy spring-loaded pin to keep the tent open, since with typical guy lines and wind the tent wouldn't otherwise have to fight against compression. Putting too much compressive force may cause that pin to fail and let the tent fold up while you're in it, if you don't run additional stakes vertically to keep the legs where they belong.

If you're looking to reduce the footprint and protect against trip hazards, you may consider putting your guy lines in the normal configuration but nearer to your canopy legs (i.e. guy line angles 15-30 degrees from vertical).

You may also choose to install your stakes at an angle with the head pointed slightly away from the canopy ceiling, stepping up the length if needed to match the depth your dirt/winds require, such that the angle between the stake and the guy line stays at roughly 45 degrees. Loads will pull at a shear to the length of the stake rather than directly pulling it out of the ground, so you can keep some of the horizontal strength of the full-length guy lines and vertical stakes without them being positioned quite as far away from the canopy leg. However, for lag bolts (see video) or other threaded/spiraled stakes, the angle is not necessary or helpful: go for the compacted earth deep down at a 90 degree angle, since the threads prevent the bolt from coming out in a way tent stakes typically can't.

Answer 2

You are disrupting tension and compression in the tent structure.

As built in picture 1 (which you are correct, nets out to the same forces as picture 2), those vertical panels are in tension. Tension is easy to do with portable, easily knocked down things like tents. Tension is lightweight. That's why tension is a darling of tent design. Also those tent poles are in compression, and only compression. Tent poles are good at that.

You’re not wrong that triangles are very strong structures, but that only works when the correct sides are capable of the tension and/or compression asked of them.

However, your alteration in diagram C makes 2 huge changes to tension and compression.

First, it turns the vertical panels in the canopy from tension elements to compression elements. They have to carry vastly more than their own weight to make those inward-facing diagonal guys work as intended. As supplied to you, the typical factory made canopy is simply not designed for that in any way, shape or form. You will need to augment that structure somehow, with tent poles, channel, or something.

Second, wind forces will show up as side loads to the canopy. Just like a table flip, this puts downward (compressive) force on the leeward tent poles, which is fine; but puts the windward tent poles into tension (i.e. tries to pull them off the ground).

You don't have any plan for handling tensile load on the tent poles. Tent poles are not designed for tensile loads, unless they are super special in some way. (Screw-anchor bottom?)

Answer 3

To reduce the tripping hazard, use brightly colored rope, and/or tie bits of ribbon around the rope so they flap in the breeze. Or add a string of pennant flags to the tie-out rope. That will be festive and decorative, as well as extremely visible.

Or, place items next to or over the ends of the tie-downs so people will naturally walk around them. Some ideas:

• potted flowers

  

• sandwich board signs (be sure to weight down your sign so it doesn't blow away)

  

• folding chairs (although be aware that people will attempt to move the chairs to more convenient locations, such as inside the tent to be out of the sun/rain)

  

• racks of goods that don't need to be protected from sun and rain (eg, a drink cooler or shelf full of canned/bottled beverages)

  

• wind spinners

  

• traffic cones

  

Answer 4

That's actually quite clever. I think it would work. Potential gotcha: The steeper cord angles make the forces tend to be more upward. You may need to upgrade to larger, or use screwpoint stakes.

Canopy tents tend not to be super stable in high wind, even guyed out as in illustrtion 1 or 2.

Failure modes:

Canopy top shifts sideways, flexing the corners and/or the poles.

Canopy top rotates, twisting the corner joints.

Canopy lifts.

Method 1 and 2 are resistant to shifts, with 2 being better. Method 2 I think has more resistance to twisting.

Method 3 should as well as method 2 for the first two failure modes, if you did all four sides the same way. This would make getting in and out awkward. Method 3 is not as resistant to upwind edge of canopy lifting. Having anchors at the base of each post would help this.

You could take this a step further:

Put all the lines between posts. On the access side, instead of running to the opposite post, it runs to the ground short of half way. This leaves a person sized walk way. Could do this on all sides. This helps counteract lifting forces on the canopy. However a combination of lift and sideways could result in motion that doesn't put much tension on the line from the lifting corner. This means that line needs to be anchored closer to the bottom of the post, or it needs a lot more tension.

For best results, you want to have substantial tension on the ropes, and use rope that has low stretch.

Now: Come up with a screw anchor that you can put in with a cordless drill.

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Some of the canopy tents I've seen at farmer's markets have a plate at the bottom of each post.. Vendors carry sandbags or concrete blocks to set on the plates. A 5 gallon pail of water would also work well.

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If you want to get a better feel for this, construct a model out of paper and thin cardboard, and use dental floss for anchor lines. Then put a fan on it.

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Flagging tape and/or small bits of reflective tape can be applied to rope to make them stand out more, reducing the tripping hazard.

Answer 5

Picture 2 has worked well for me, with fairly steep guys in light winds or on the downwind side. It often has the advantage that laying things out without diagonals can fit better around other units, but the front guys need to be well-protected from people walking into them, and even hi-vis ratchet straps are apparently invisible to some. I've used tables, pot plants, etc.

As has been said elsewhere, picture 3 is protected against racking (to be honest the side will do that anyway is attached at all 4 corners) but not protected against the whole thing or one edge lifting. This sort of bracing can be used with weights, but you need a lot of weight on the upwind side. Market traders use multiple cast iron weights per pole, each of 20kg and shaped to fit around the pole on a foot. Two sandbags per pole may be enough if the pole can't come out from in between if pulled almost straight upwards.

Answer 6

In brief, in addition to other good observations, your repositioning of lines will put considerably more tension on each one.

From an amateur-engineering viewpoint (vectors!), yes, your proposed smaller-footprint version addresses the same issues... but, again, does require much more from each of those lines, since they have considerably worse "leverage".

(And, also, some incidental weirder failure modes, as pointed out in other answers.)