concrete logs, just an idea

[Jon Boy]

cheap and easy Concrete Logs
concrete mix (main form)
small long skinny rocks (nubs, notches, and limb stubs)
assorted cardboard tubes (molds)
duct tape
small bucket for mixing
knife or blade

been thinking a little about course/trail obstacles. not sure if this has been done already, atleast i haven't seen anything about it yet anyway. i used quikcrete for a test sample and sifted out the bigger rock from it for my test mix. i figure some of you other curious types will find better ways and processes, i'm just throwing out the idea i guess. figured mainly outdoor courses could find this useful, since there's no wood to rot or wear down as fast.

cut tubes lengthwise once. open up the tube and make a few small holes randomly (careful not to get the holes too close together as this will cause weak points.push the small rocks from what would be the inside of the tube out the holes you just made. have them stick out lengthwise no more than 1/3 of the length of the rock so they're less likely to pull out.
now after you've got the rocks placed upon the tube, carefully place tape on the outside to help hold the rocks while closing up the cardboard mold. some rocks may push/fall out, so watch for that. run tape down the seam where you cut the tube, putting it back together.
use tape to cap the bottom of the tube seal it up the best you can but it doesn't have to be perfect. wrap tape every 4-6 inches around the tube to help hold things together.

ok you should be ready to mix some crete up by now. the amount varys depending on how big and how many forms you make. the smaller the batch the trickier i find it to get just the right amount of water/crete mix ratio. once you feel satisfied with your mixing job, then time to pour. as your pouring use a length of grass trimmer string to stick in there and work air bubbles out, tapping on the mold (mind the rocks) as your filling helps with getting air out the easiest and best i think. once filled and if your happy with your work so far, then stand the molds up to dry and cure. "WARNING: after you've filled you molds, after awhile the cardboard becomes very soft and you can easily break what you just made". the test sample i did fell over after sitting an hour or two and broke in 3 pieces , but i did notice there was no air bubbles in it . now if your careful enough you can try to maybe bend or curve the mold before it has time to set-up with out it breaking. in two. after sitting a couple days to dry and cure, the mold should be ready to pull off if you didn't really screw up your mix anyway .

the big idea was thinking "hey if RC companies or someone was to create "tree molds" out of plastic then sold these to the public as molds or some form of kit, so people could create their own. also if made in long sections you could then score and snap/break the trunks to the desired length you need. make a bunch load and have a sort of "Log Jam" with them.

my test mold, looks like it may just work like i was hoping. the concrete makes up the main trunk with the small rocks acting like the stubs and knots like a real tree, even though it doesn't really look like one. on my test piece i compacted things just to see how this first one worked. next test i'm gonna space things apart better and maybe run metal reinforcment rods inside it.

any opinions? like i said it fell before it had a chance to cure and broke, so imagine it in 1 piece not 3.

[Darksiede]

I think it's a brilliant idea..

But you can save some money & effort as rebar would be serious overkill.. Depending on the size & length of your logs, a 2X2 would offer enough strength to keep them together in all but extreme gap spanning situations.

My bro does simulair thing with his salt fish tank sea-scaping. They use 'crete a ton, and mold and shape it to resemble reef base materials. In those however, they have to stray away from materials that will decay in salt water, and thus use "rock" as the base sculpture material & for outcroppings.

~Kev

[Slow Mo]

Thats a great idea, im thinking about a rock racer course and might do something like that.

[Jon Boy]

well, i was just thinking of a piece of coat hanger for the rebar really, but i think your right it doesn't seem to be needed.

poured another test mold, the weight feels good too. not so light it'll get pushed around easily, but light enough to roll and flip. but, i'm going to have to wait till it's dried and set to really see though.

[dusty husky]

How bout using a rock? My buddy drives over the pass 3hrs. and picks up lava rocks because there aren't any in the valley.

[Jon Boy]

you could, but like i said it's just an idea.
IMO, the point is to have something that could move or roll. possibly causing a hang up or highcenter. the shorter ones (made these about a foot or so, around 1 1/2dia) are good for this. plus it seems to be a good weight for the scale.
then if the ends were notched on the longer ones for the edge to span a gap (2 1/2ft is about the longest i've tried to make). running the risk of hitting a rock/knob throwing you off. heavy enough i doubt they would move, unless using too much throttle.

...or maybe paint them a heavy gloss brown, add shallow water and you have slick logs that won't sog or rot.