Best soil to use for building jumps?

[patches]

Looks good patches. Nice work.

So when are we getting the invite?

 

Any saturday that I go though, you're welcome to come along! Also bring your KTM... you can have some fun on the endurocross track!

[Big H*]

The PI or Plasticity Index of the material will be the one you choose. PI means the amount of clay present to make the material plastic. To test this (the eccentric1 on site test and not a real prescribed test like the Atterberg Test) take a little soil in the palm of your hand. Shake out the coarse material so you sit with dust only. Spit on it and mix it. Roll with your finger and try to form a little roll. If it breaks up when thick the soil is not cohesive. If it still rolls when very thin to much plasticity. You need the one that breaks up when it reaches the thickness of a match stick.

 

The laterite (red soil sometmes with little oxidised nodules in it) will work. You need to find the optimum moisture content before compacting. Too much water sloppy to little water it breaks up. A indication is when you grab a handfull and squeeze it in your palm. If it forms a solid cake and you drop it, it shatters and makes a little heap it will be almost ready.

 

You can also stabilize with cement. This makes a more permanent but more expensive structure that will be very impervious to rain and wear through use. It is also harder to fall on. Cement stabilised soil can crack as well and eventually destroy itself. Mix in about three to five percent cement by mass. An easier method is to mix in cement and stop just when the colour of the soil begins to change. Add water and place and compact as soon as possible. Flash set takes place in cement within three hours. It loses strenght after that.

 

Hope the above helps.

Edited August 22, 2011 by eccentric1

[jcmeyerSS]

take off hard landing soft

haha just kidding dont know nothing about leaving terra firma

[udxcob]

Soft landings are dangerous, many years ago I was 360ing a set of doubles with a soft landing, at 270 I realised I wasn't going to make it and put my foot out, it went straight into the soil and my body and bike were still roating.....twisted my knee in half, rushed to hospital and had to rebuild the cup and put a steel plate in the bone, and a bone graft from the shin......its still in my leg today, probably 20 years later, I would have prefered a harder landing......