Flat ground questions- Mtbr.com
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  1. #1
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    Flat ground questions

    I took some photos of some of the flat stretches. I've still a couple weeks of benching to go before I reach them. Currently they are leaf-raked, and that is all. They ride ok as-is, and I am thus tempted to just ride them in. Would I be making a mistake in taking that approach?

    Photos below. The first two show different areas where it's impossible to bench as described in the book. The third is from an opening just ahead of our trail entrance. It gives a good idea of the ground we are working with. The entire hill is essentially beach sand held together by a thin layer of vegetation. The duff layer varies in thickness, but it's all packed sand underneath.

    So I am leaning towards "leave well enough alone" and riding in the sections below without any further scraping or raking.

    Flat ground questions-flat01.jpg

    Flat ground questions-flat02.jpg

    Flat ground questions-sand01.jpg

  2. #2
    Heavylegs
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    I would not touch the first two areas. Is the third just an entrance to the trail or is there a long section of trail with this sandy of soil?

  3. #3
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    Quote Originally Posted by redd4573 View Post
    I would not touch the first two areas. Is the third just an entrance to the trail or is there a long section of trail with this sandy of soil?
    The third is just the entrance.

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    1st 2 pics look great.

  5. #5
    saddlemeat
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    What are you doing where you are benching, are you into the same sand?

    How thick is the duff in 1 & 2?
    I ride with the best dogs.




  6. #6
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    Quote Originally Posted by bsieb View Post
    What are you doing where you are benching, are you into the same sand?
    Yes. And I am concerned about that, to be honest.

    How thick is the duff in 1 & 2?
    On the order of an inch. It varies, but the layer is pretty darn thin.

  7. #7
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    Quote Originally Posted by bsieb View Post
    What are you doing where you are benching, are you into the same sand?

    How thick is the duff in 1 & 2?
    Here is a photo I took this evening that happens to show what we're into when we bench. Sorry 'bout the blur, but it should still give a good idea of the soil.

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  8. #8
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    Quote Originally Posted by redd4573 View Post
    I would not touch the first two areas. Is the third just an entrance to the trail or is there a long section of trail with this sandy of soil?
    agreed, first 2 should be fine "as is" to ride, as far as the sandy entrance....good luck
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  9. #9
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    Quote Originally Posted by JonathanGennick View Post
    Here is a photo I took this evening that happens to show what we're into when we bench. Sorry 'bout the blur, but it should still give a good idea of the soil.

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    With that sand, I'd be more inclined to leave the duff. I don't have much experience in sand, but I'm sure someone else will.

    In Parker's book Natural Surface trails by design, he goes more into soil types. Sand is obviously one of the least stable, more erodible, so you gotta back the grade off and/or increase the frequency of your grade reversals. You might ask your designer to back of his 10% to 5 or 7% if that sand is everywhere. 10% is a guideline, not a law, once you get into specific soil types.
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  10. #10
    saddlemeat
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    Quote Originally Posted by JonathanGennick View Post
    Yes. And I am concerned about that, to be honest.



    On the order of an inch. It varies, but the layer is pretty darn thin.
    I would avoid removing any of the duff. You may have to add material over the sand to stabilize it. An inch of duff isn't much. I'm glad it's not my project.
    I ride with the best dogs.




  11. #11
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    Quote Originally Posted by bsieb View Post
    You may have to add material over the sand to stabilize it.
    So that's an interesting idea. I could try benching a section, saving the duff first, and then putting the duff back after cutting the bench.

    We aren't going to scrape the duff on the flat sections, btw. We've talked and have agreed to leave well-enough alone on those. But the bench sections, those worry me a great deal. Saving and replacing the duff--it's probably worth making the experiment.

  12. #12
    saddlemeat
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    Quote Originally Posted by JonathanGennick View Post
    So that's an interesting idea. I could try benching a section, saving the duff first, and then putting the duff back after cutting the bench.

    We aren't going to scrape the duff on the flat sections, btw. We've talked and have agreed to leave well-enough alone on those. But the bench sections, those worry me a great deal. Saving and replacing the duff--it's probably worth making the experiment.
    Yes, and it beats hauling soil in from somewhere else, which is also a possibility.

    At least the sand drains well...
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  13. #13
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    First 2 pics look fine now but I suspect that they will become a problem. May need to dig a ditch alongside the tread so water has somewhere to go. If there's a slope above that sheds water during heavy rains a ditch to get rid of the water may be needed. Leave it for now but keep an eye on it.
    There's a big difference between ripping and skidding. Those who skid don't know how to ride.

  14. #14
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    At the Midwest MTB conference 3 years ago in Grand Rapids, they had a tricked out Ditch Witch with a roto-tiller attachment.

    Trail construction in deep sand was done by removing larger sticks and logs, then just tilling the duff and top soil into the sand. I think they ran some kind of compactor over the tilled up soil/sand.

    Walt

  15. #15
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    Bench cuts in Sand???

    Not sure what your thinking. As you can figure with all the comments, Sand just fails. You have to have the natural vegetaion or something to stablize the sand. Once you have broken the root system it takes years to decades to come back. Putting the duff back will help fortify the organics in the soil, but it will still take time and will never work with tires runnung on the tread.

    The only technique I have ever found that lasts to stablize sand is to bury rock in it. I have used several styles that work. Roman road uses the most rock. Cribbed sides and gravel works the best. Just mixing large gravel into the sand will work for a while depending on water flow and use.

  16. #16
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    Sand base is a place where a line of secured logs either side of the trail can be the edge of a bed of stones over the sand. It will require stones/gravel to be brought in in large quantities. The result is a raised tread with good drainage underneath and this approach avoids the need to mix anything into the base and re-compact it. Even on sand there will be channels and surface flows that need to be attended to so they don't well up against the trails and erode it logs and all. A cost intensive approach that is probably best limited to short, difficult sections of trail.

    Another way to look at sand is can the trail be routed in a way that riding on semi-stable sand is interesting and sustainable. Never owned a fat bike, but have ridden a lot of sand in the past and quite enjoyed the gentle struggle of a soft, slow sand trail covered with litter. Provided there are no unrealistic grade/direction changes the trails seem to survive pretty well over time.

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