Cracks in my DJ's

[mtb_coop]

Over the holidays some we've been building some DJ's and they're looking pretty nice but there got a few big cracks in the lips. In the short term it shouldn't be much of a problem but eventually the lip will crumble off.

I'm not sure if its the dirt we're using of the recent rain that has done it but I just want to ask what techniques, types of dirt and how much water used on the jump to make it nice, smooth and durable?

Any comments are welcome.

 

[Hunt_11]

hey lachie,
i dont reckon it will brake off and if it does it wouldnt be any time soon. they're probably just like surface cracks which won't be to bad.
Can't wait to see the new up ramp after you guys used the trowl on it

cya

 

[mtb_coop]

Yeah the trowel made it pretty smooth and we used it to patch up the cracks but i reckon eventually some chunks will break off the upramp.

anyone else got any idea's on preventing cracks

 

[dw4dh]

Carpet can be used to make the upramp or the downramp smoother and also prevents the dirt from breaking up.

 

[shake_rattle_and_ roll]

Welcome to trail maintenance. Get used to it. They all eventually crack once they dry out- unless you've got a particularly water retentive mix of soil, fine organic matter and clay, or the most mythically magic dirt known to man. As mentioned carpet is great for keeping the moisture in and protecting landings, as well as some lips depending on the type of carpet you use (on kickers the carpet can actually wash off needed speed).

 

[DjRyde]

If you give it a through water everyday and smooth is out after riding it should be fine. But it depends wat dirt you are using is it clay.

 

[lach92]

Hey mate.

Would suggest like wetting down the ramp then put a layer of dry dirt on top and compacting that into place but it would need to be left and not ridden for 3 or so days. You could also reinforce behind the lip if there isnt much dirt then it has more room to move so piling up behind the top of the lip will help.

Cheers

 

[mtb_coop]

thanks for the help guys

I've patched up the cracks with a trowel and i'll consider puting carpet on the downramps. Anyone know where i could get some cheap or free carpet?

 

[rabatt]

look in the bins behind carpet/floorcovering shops, thats were i get mine from.

how i overcame this problem (i dont have water) is when it rains and i build something, as it dries out and starts to crack i mix muddy paste and force it into the cracks. untill it is dried out as much as it will. the first time it dries it will be abit rough but next time it rains you can smooth it off really nicely and usualy it wont crack again. carpet it a must tho!

good luck.

 

[STPryde]

The reason dirt (mainly clay) cracks is because, as it hardens, water evaporates out of the outer layer, causing it to contract. The inner part of the jump however doesnt get sunlight, so the only way water can escape is out through the outer layers (very slow). So the outer layer drys and shrinks and the inner mound stays the same, this of course will cause it to crack.

The obvious way to prevent this is by letting the whole jump dry out evenly, easier said than done.

The way i stop my lips from cracking is build it, water it, carpet over the top, then water the carpet a little every day for at least a week (2 is better). Peel back the carpet and you should hav a slightly damp jump, leave the carpet on for another week or so without watering for it to dry completely. It may still crack to some degree depending on your dirt, but they should be so small that its not an issue.

Alternatively, if 3 weeks curing time on each lip is more than you can handle, try building with less water (no water if possible, but it rarely is). Build the jump dry, shape it as best you can, water it, but dont compact it. Come back the next day and it should have mostly dried out but still be just moist enough that you can pack it in really well. Add no more water, just cover with carpet and leave for a few days.

 

[mtb_coop]

The reason dirt (mainly clay) cracks is because, as it hardens, water evaporates out of the outer layer, causing it to contract. The inner part of the jump however doesnt get sunlight, so the only way water can escape is out through the outer layers (very slow). So the outer layer drys and shrinks and the inner mound stays the same, this of course will cause it to crack.

The obvious way to prevent this is by letting the whole jump dry out evenly, easier said than done.

The way i stop my lips from cracking is build it, water it, carpet over the top, then water the carpet a little every day for at least a week (2 is better). Peel back the carpet and you should hav a slightly damp jump, leave the carpet on for another week or so without watering for it to dry completely. It may still crack to some degree depending on your dirt, but they should be so small that its not an issue.

Alternatively, if 3 weeks curing time on each lip is more than you can handle, try building with less water (no water if possible, but it rarely is). Build the jump dry, shape it as best you can, water it, but dont compact it. Come back the next day and it should have mostly dried out but still be just moist enough that you can pack it in really well. Add no more water, just cover with carpet and leave for a few days.

Thanks. Thats some great tips.

My jumps have fairly large cracks in them already so what would you recomenned?

1. Destroy the jump and start again

or

2. Wet the whole thing, smooth off the lip then place carpet on the lip and water it each day.

 

[STPryde]

just fill the cracks with wet dirt, wet it down and treat it as if it was a new jump (carpet + water etc).

 

[mtb_coop]

to build jumps allowing them to dry evenly, could i build them by making a small mound of dirt then let it dry out, then gradually add to it allowing it to dry after each addition to it?

 

[Hunt_11]

to build jumps allowing them to dry evenly, could i build them by making a small mound of dirt then let it dry out, then gradually add to it allowing it to dry after each addition to it?

Lachie, i think it would be better to make a big pile and pat it down heaps,
then shape it better when its hardened and then water it a bit if we need.