I was going to reply to one of the old threads, but since it seems I've got a significant amount of information to convey, I've decided to start a new one. I've recently figured something out that would apply very well to building mobile obstacles for Nerfing.
There is an ancient practice called "pioneering" that involves lashing poles together with ropes. Some scouts carry it out today, but it appears to be a dying art judging by the lack of non-scouting sites dedicated to it.
The point is that there are knots that can do all the stuff we'd want to do without threading, gluing, or other mucking about. They're tied easily in a minute or less when you get the hang of it, are quite sturdy, and untie fairly easily when you're done.
Tripod lashing
Square lashing
That site has a couple of other lashings that would be useful, but with those two you can build just about anything we'd need.
For this 'writeup', the entire instruction set is: Tie a tripod knot around 3 PVC poles of any size, set up tripod (optionally fix to ground or otherwise reinforce), affix cover.
Buying a stack of 1/2" pvc at Lowes is something like $18 for 10x10' sticks. Cut those in half to get 20x5' sticks, also buy a spool or two of medium-duty twine or mason's line (4-5$) and something to cover the obstacle with (could be anything though - bedsheets, cardboard, dropcloths, tarps, old shirts & coats, pine boughs, palm fronds... Keep in mind you don't need to cover all sides to create a viable obstacle). The cost per tripod-mobstacle should be in the neighborhood of $3-4 each, with no covers (since those can be almost anything, and certainly could be something you have lying around or could get for free, or could be something you spend hundreds of dollars on. Using Slug's purchase or some of these from Harbor Freight yields a cost-per of $5.5-$9 each - attach with some of your cordage or tape).
If you're feeling the need, you could dangle something heavy from the center of the tripod to keep it in place (a rock, eye-stake in the ground, bucket filled with rocks/spare blasters/lunch or use the preferred method: a cauldron); keeping the corners down shouldn't be an issue on turf but if it is bind the corners of the triangle together with another rope, tent pegs or stakes, or as shown on the linked sites with poles and additional lashings. Keep in mind that PVC is more slippery than wood, so keep your knots a few inches from the end of your poles. You can either leave the knots as-is in place or untie them when you're done. If someone runs into an unstaked tripod it should just collapse. For non-structural work, I'd imagine something as thin as mason's line will work, though I used paracord building one the other night. I also used rubber bands and super-cheap landscaping stakes for a smallish one, so that's something else to consider if you don't need the things higher than +/-5'. A twisted-natural fiber rope is best. I'll experiment with twine but I suspect that it'll work great (i.e.: better than paracord) for light-duty stuff.
And that is the kicker - these practices are good for far more than simple walls/blocks. With structural poles (4-8" dressed trees up to 20' long or 2x4's up to 8' long. Do not use PVC for any kind of load-bearing application!) and rope (1/2" +) there are projects you can build that are completely knock-down, but also completely load-bearing.
And once you've got things figured out, there's no stopping you making square frames, cubes, serpentine walls, tents/bunkers, etc. from just PVC.
Obviously I accept no responsibility for your stupidity - test anything you build from rope and wood before allowing just anyone to use it - but it seems that a dedicated host could easily construct quite the field to play on.
Edited by Aeromech, 23 November 2015 - 02:59 AM.
