# Switchback turns on steep inclines



## TunicaTrails (Jun 29, 2009)

Hi all, I have two switchback turns and bench cutting that I'm going to need to do on a steep loessial bluff that's eroded over time to become a hill of around 90% grade at the point of the higher up switchback turn. It will all be dug by hand with McCleods and Prohoes. No rocks, but plenty of roots. 

I've been visualizing the digging but I'd really appreciate hearing tips and seeing photos of some of you all's handiwork on switchbacks, especially those on steeper hills. I'm thinking a 2 foot excavation on the bench cuts but digging 5 ft in for the turn?


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## Skookum (Jan 17, 2005)

Sometimes when you encounter those, the roots just won't let you sculpture what you need, if it's not super steep you can do a fill bench to raise the tread on the bottom side.

Sorry no pictures, but if you have about 5 or more people, have planned it out, got everything set up with materials (logs-rock for retention if it's really big and a place to harvest lot of mineral). You can easily bang one out in a day.

Last year was present on a work party that set up a zip line of buckets from a fell tree above. Was really a super fast way of getting dirt to fill.


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## Trail Ninja (Sep 25, 2008)

Sorry, the pictures aren't very good. It's pretty much what Skookum described.

Brushed out and cedar logs in place using 2 live trees and a bunch of cedar stakes sunk 4 feet into the ground with about 18" above ground.

View attachment 588312


Starting to dig into the back slope.

View attachment 588313


Mostly finished. There was more than enough material in the back slope to fill the crib wall. It's tight but rideable.

View attachment 588314


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## Fattirewilly (Dec 10, 2001)

TunicaTrails said:


> Hi all, I have two switchback turns and bench cutting that I'm going to need to do on a steep loessial bluff that's eroded over time to become a hill of around 90% grade at the point of the higher up switchback turn. It will all be dug by hand with McCleods and Prohoes. No rocks, but plenty of roots.
> 
> I've been visualizing the digging but I'd really appreciate hearing tips and seeing photos of some of you all's handiwork on switchbacks, especially those on steeper hills. I'm thinking a 2 foot excavation on the bench cuts but digging 5 ft in for the turn?


First, is there a better(more level) spot nearby that you could put the swithcback on, then reroute the trail to?

This thread was all about switchbacks, skip the first link, I wasn't the only one whose head was trying to explode. http://forums.mtbr.com/showthread.php?t=670049

90% grade will require much digging. Let's say you have a reasonable 8' diameter turning platform, you have 7.2' (8' x 90%) of elevation to deal with, so you want to build roughly a roughly a 3.6 foot retaining wall for the lower leg and dig in (the vertical bench cut prior to backslope blending) on the upper leg about 3.6' .


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## TunicaTrails (Jun 29, 2009)

Unfortunately choosing this area is the best I can do due to several factors. It sounds like partial bench cut work on the turns is going to be hard to avoid, but I appreciate seeing the photos of crib walls with red cedar. It just so happens that two nice fallen red cedar trees are close by.

Would it be best to stake out and build the switchbacks first before bench cutting trail to and from them?

I like this link from the other thread and it's worth re-posting:
http://www.poedunk.com/wp-content/uploads/2007/06/switchback.pdf



Fattirewilly said:


> First, is there a better(more level) spot nearby that you could put the swithcback on, then reroute the trail to?
> 
> This thread was all about switchbacks, skip the first link, I wasn't the only one whose head was trying to explode. http://forums.mtbr.com/showthread.php?t=670049
> 
> 90% grade will require much digging. Let's say you have a reasonable 8' diameter turning platform, you have 7.2' (8' x 90%) of elevation to deal with, so you want to build roughly a roughly a 3.6 foot retaining wall for the lower leg and dig in (the vertical bench cut prior to backslope blending) on the upper leg about 3.6' .


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## th29 (Nov 4, 2004)

Here are a couple of shots that might give some perspective.


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## Visicypher (Aug 5, 2004)

*This situation sounds familiar*

You need to dig....and dig a lot!

I'd do a 8' radius (on centerline). If you are going to do a partial bench, schedule the construction date for mid to early spring/late fall to acheive maximum compaction for the partial bench. If you can, try to haul rocks (big ones...40-100 lbs) for cribbing for your partial bench. Place your rock so the lock into place. Pay attention to your in slopes and out slopes on your switchback. If you can sneak a Dingo, or similar equipment, with an excavation arm, I'd highly recommend it...especially if you don't have rock to deal with.

And for the love of all that is holy...don't site it near a tree like in this pic. Unfortunately, I was limited to this spot by existing constraints (which I won't get into).


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## bweide (Dec 27, 2004)

Definitely stop benching well prior to the switchback and connect everything together when the switchback is completed. Large constructed structures always seem to turn out a bit different than you planned them, usually to their benefit.

Loess soils have a lot of structural integrity vertically, forming surprisingly tall stable cliffs. This tendency might allow you to dig more of your platform into the hillside because you won't have to build a retaining wall above the turning platform. You might be able to construct a nearly vertical 4ft or 5ft tall backslope without worrying about reinforcing it.


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## Walt Dizzy (Aug 18, 2003)

Visicypher said:


> You need to dig....and dig a lot!
> 
> I'd do a 8' radius (on centerline). If you are going to do a partial bench, schedule the construction date for mid to early spring/late fall to acheive maximum compaction for the partial bench. If you can, try to haul rocks (big ones...40-100 lbs) for cribbing for your partial bench. Place your rock so the lock into place. Pay attention to your in slopes and out slopes on your switchback. If you can sneak a Dingo, or similar equipment, with an excavation arm, I'd highly recommend it...especially if you don't have rock to deal with.
> 
> And for the love of all that is holy...don't site it near a tree like in this pic. Unfortunately, I was limited to this spot by existing constraints (which I won't get into).


Visi, when you speak of "in slope" and "out slope" in this context, I assume you are talking about the rate at which the trail climbs the hill, rather than the degree to which the trail bench departs from horizontal? Sorry to pick at your nits, but very similar terms are used, even in switchback construction, to describe completely different things.

Walt


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## Visicypher (Aug 5, 2004)

*This should explain it all...I hope.*



Walt Dizzy said:


> Visi, when you speak of "in slope" and "out slope" in this context, I assume you are talking about the rate at which the trail climbs the hill, rather than the degree to which the trail bench departs from horizontal? Sorry to pick at your nits, but very similar terms are used, even in switchback construction, to describe completely different things.
> 
> Walt


I hope this explains it all..


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## Walt Dizzy (Aug 18, 2003)

Fattirewilly said:


> First, is there a better(more level) spot nearby that you could put the swithcback on, then reroute the trail to?
> 
> This thread was all about switchbacks, skip the first link, I wasn't the only one whose head was trying to explode. http://forums.mtbr.com/showthread.php?t=670049
> 
> 90% grade will require much digging. Let's say you have a reasonable 8' diameter turning platform, you have 7.2' (8' x 90%) of elevation to deal with, so you want to build roughly a roughly a 3.6 foot retaining wall for the lower leg and dig in (the vertical bench cut prior to backslope blending) on the upper leg about 3.6' .


I agree that J. Johnson's approach to laying out a switchback is a lot of work to understand. However, IMO it offers some advantages to the IMBA approach.

-The IMBA approach is conceptually simpler. However when you get down to laying it out, it doesn't show you how to design in the grade reversals in and out of the turn. I concede in advance that those of you with experience know how to do this. I didn't, and messed up my first couple of attempts.

-The IMBA switchback design depends on the construction of a central, level platform. The disadvantage of this approach, in my opinion, is it forces the upper and lower legs of the turn to make up elevation difference between the upper and lower legs of the trail. The J.J. approach uses a radiused turn that is sloped, helping to make up the elevation difference over it's length. It's fairly easy for a novice builder (me) following IMBA's design to end up with rather steep sections of trail leading into and out of the turn. Again, I'll allow that an experienced builder may know how to avoid this problem.

-Because the J.J. approach uses a radiused turn, it's more feasible to pile up rocks or logs right up to the inside corner of the turn, making it more difficult for riders to shortcut compared to IMBA's design which uses a point radius. To be fair, the IMBA design, properly executed, is probably more resistant to water damage.

-IMBA's design tends to (in my experience) lead to a rather massive retaining wall on the lower leg of the turn. On *average* this will be the same for the J.J. layout. However, the J.J. layout offers the option of swinging the turn arc wherever you want it. You can, in theory, build a turn with no lower retaining wall at all (with a whole 'lotta digging on the upper side!) This could be a huge advantage building in a location without easy access to rock or logs. Another advantage would be in a place that has no space for the upper arc of the turn. Putting the arc toward the bottom leg would allow, with the construction of a huge retaining wall, the contruction of a turn in an otherwise unusable space.

I think that an experienced builder could alter the IMBA design to duplicate any of these features. The power of the J. Johnson approach is it shows anyone willing to spend the time to understand it exactly how to lay it out and does not depend on the builder having years of experience to make it work in exceptional circumstances.

Your mileage may vary.

Walt


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## TunicaTrails (Jun 29, 2009)

Thanks for all the advice, diagrams, and photos. I studied them intently. Here's how they came out:














































They have dried fully and need some perfecting next time it rains, but they're wide and ridable. Come race with us on May 8th and see for yourself!

Thanks again.


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## justinwp (Nov 12, 2010)

Looks good! I would consider placing some obstacles on the inside of the switchback to keep it from being cut.


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## J. Johnson (Feb 20, 2011)

Walt Dizzy said:


> Visi, when you speak of "in slope" and "out slope" in this context, I assume you are talking about the rate at which the trail climbs the hill, rather than the degree to which the trail bench departs from horizontal? Sorry to pick at your nits, but very similar terms are used, even in switchback construction, to describe completely different things.
> 
> Walt


This looseness of terms is definitely a nit of confusion, and needs standardization. Having studied this quite a bit, I find that "the rate at which the trail climbs the hill" is best described as its _grade_. "Slope" is best reserved for either the the tilted topography (e.g., side of the hill), or the angle of that tilt. The slope _across_ the trail is "in-slope" and "out-slope" (best used with the hyphens).


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## Ridnparadise (Dec 14, 2007)

TT, is that a wooden bridge or elevated platform at the top of the switchbacks? I am just worrying that it may be a place where large amounts of water funnel down into the first (lower) corner and impact the crib wall. It could act as a berm and catch all that water after debris traps in it. The drain below the turn seems to be isolated from the turn by the reverse-grade dip between them. 

Having said that, I love the feel of that first corner. It is very tight, but there is no obvious place to move it and it also offers a momentary respite before a nasty climb through the next corner. Is it possible to rock armour that corner if water starts to damage it? Maybe even armour a low berm into the hill to prevent erosion of the high side and allow more speed and flow in both directions? I can't see any perimeter drain working on such a tight turn. I know that is going to mean harvesting flat and large rocks and moving them by hand from your post. No small thing. 

Looks like a good job on steep terrain.


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## TunicaTrails (Jun 29, 2009)

Sorry, there's a bunch of cut brush tangled up with grape vines that obscures the hill. Part of our subtropical environment.

There are no bridges on the switchbacks but I have made significant use of crib walled (red cedar) partial bench cuts on the upper level. I'm finding that I can cut further into the soil and may end up not needing any of the partial bench sections eventually. But it'll hold up for the race (coming up this weekend!)

As shown on that great PDF diagram, I want to cut in a culvert at the wall of the turn to divert drainage. The whole thing was a muddy mess when I first laid it in and I was worried it might stay that way, but once we got a good solid dry spell, it's hardened and is stable. Loessial soil is magical, once it dries it can hold sheer vertical bluffs for thousands of years.

I'll definitely take everybody's suggestions into advisement and try to supply better photographs in time.



Ridnparadise said:


> TT, is that a wooden bridge or elevated platform at the top of the switchbacks? I am just worrying that it may be a place where large amounts of water funnel down into the first (lower) corner and impact the crib wall. It could act as a berm and catch all that water after debris traps in it. The drain below the turn seems to be isolated from the turn by the reverse-grade dip between them.
> 
> Having said that, I love the feel of that first corner. It is very tight, but there is no obvious place to move it and it also offers a momentary respite before a nasty climb through the next corner. Is it possible to rock armour that corner if water starts to damage it? Maybe even armour a low berm into the hill to prevent erosion of the high side and allow more speed and flow in both directions? I can't see any perimeter drain working on such a tight turn. I know that is going to mean harvesting flat and large rocks and moving them by hand from your post. No small thing.
> 
> Looks like a good job on steep terrain.


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## J. Johnson (Feb 20, 2011)

*USFS 914_1 is the better drawing*

Strong suggestion: don't get too fixated on "that great PDF diagram" from the USFS. They have three different switchback drawings (and a "climbing turn" drawing; see  http://www.fs.fed.us/database/acad/dev/trails/trails.htm). I would recommend their 914_1 drawing ("switchback - type I") at http://www.fs.fed.us/.ftproot/pub/acad/dev/trails/914_1.pdf as the best of the lot.

Also, your expectation of loessial soil is likely to be disappointing. I know of _no_ soil that can hold a bluff "for thousands of years". You may want to delve into that a little further.


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## TunicaTrails (Jun 29, 2009)

That's a climbing turn which is not possible on a hill as steep as what I built on. Did you read the jist of this thread? Welcome to the Tunica Hills blufflands, jackass.



J. Johnson said:


> Strong suggestion: don't get too fixated on "that great PDF diagram" from the USFS. They have three different switchback drawings (and a "climbing turn" drawing; see http://www.fs.fed.us/database/acad/...fed.us/.ftproot/pub/acad/dev/trails/914_1.pdf as the best of the lot.
> 
> Also, your expectation of loessial soil is likely to be disappointing. I know of _no_ soil that can hold a bluff "for thousands of years". You may want to delve into that a little further.


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## jeffscott (May 10, 2006)

TunicaTrails said:


> Hi all, I have two switchback turns and bench cutting that I'm going to need to do on a steep loessial bluff that's eroded over time to become a hill of around 90% grade at the point of the higher up switchback turn. It will all be dug by hand with McCleods and Prohoes. No rocks, but plenty of roots.
> 
> I've been visualizing the digging but I'd really appreciate hearing tips and seeing photos of some of you all's handiwork on switchbacks, especially those on steeper hills. I'm thinking a 2 foot excavation on the bench cuts but digging 5 ft in for the turn?


Often most people overlook the fact that the grade needs to back off as you approach the switch back when going up hill or down hill....

This massivily reduces braking forces and therefore erosion.

On very steep logging and mine roads often the vehicles will not turn but simply reverse up the next switchback.....works very well.


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## jeffscott (May 10, 2006)

th29 said:


> Here are a couple of shots that might give some perspective.


Bingo you can see the reduction in grade here.....could have down a bit more of a cut and fill operation however.


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## Ridnparadise (Dec 14, 2007)

I agree, a lower grade turn is best. The reverse grade pre-switchback is a really good idea with new trails, but not so practical when maintaining existing turns. Having just spent a few days renovating really nasty steep turns and turning them into red hot plunging switchback berms with uphill lines as well, I would prefer to ride your sort of line jeffs, but I bet I ride the plunging line switchback more often. 

Just to add, lately we have been reclaiming out of rock and clay, so cutting new radii into the hill is not too hard with an appropriate berm and drainage.


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## J. Johnson (Feb 20, 2011)

TunicaTrails said:


> That's a climbing turn which is not possible on a hill as steep as what I built on. Did you read the jist of this thread? Welcome to the Tunica Hills blufflands, jackass.


For sure, the USFS "switchback - type I" (914-1) and "climbing turn" (912-10) diagrams are essentially identical (see side-by-side comparison at the bottom of [http://www.scn.org/sbtp/swbk-defs.html); this really goes to the long-running but quite meaningless attempts to distinguish between these. (For full discussion see http://www.scn.org/sbtp/swbk-defex.html.)

In regard of slopes and turns, "possible" is not a matter of can or can't; it's a matter of _degree_, of how much construction you want to do, of design and kinds of structures. With enough work (and proper design) good turns can be built even on steep slopes, but bad design has lead to bad turns on fairly low-angle slopes. Take a look at http://www.scn.org/sbtp/swbk-gdev.html to see the interaction between slope and various types of turns. And take a look at the picture at the bottom. The original slope was so steep it was proposed to use a ladder. As it turned out, the upper leg was excavated into the slope about eight feet, providing fill for the lower leg. A lot of work, yes, but, as demonstrated, possible.


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## cmc4130 (Jan 30, 2008)

J. Johnson said:


> For sure, the USFS "switchback - type I" (914-1) and "climbing turn" (912-10) diagrams are essentially identical (see side-by-side comparison at the bottom of [SBTP: Various definitions of 'switchback'.); this really goes to the long-running but quite meaningless attempts to distinguish between these. (For full discussion see SBTP: Definition of 'switchback' (and exegesis)..)
> 
> In regard of slopes and turns, "possible" is not a matter of can or can't; it's a matter of _degree_, of how much construction you want to do, of design and kinds of structures. With enough work (and proper design) good turns can be built even on steep slopes, but bad design has lead to bad turns on fairly low-angle slopes. Take a look at SBTP: Geometrical Derivation of a Switchback. to see the interaction between slope and various types of turns. And take a look at the picture at the bottom. The original slope was so steep it was proposed to use a ladder. As it turned out, the upper leg was excavated into the slope about eight feet, providing fill for the lower leg. A lot of work, yes, but, as demonstrated, possible.


i enjoyed reading your articles. especially the illustration of the turns which cut back uphill/upslope before doing a slightly-more-than-180 turn.

the only part i didn't quite get was your use of the term "zero-radius turn."

SBTP: Geometrical Derivation of a Switchback.

are you saying that this staircase would be a "zero-radius turn" 90 degrees? like a person walks straight, stops, pivots 90degrees, then walks straight. ? no matter if you have it squared off, a cyclist or hiker's path is going to be in a curve... so there's always going to be a radius to be measured. ... no?


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## Walt Dizzy (Aug 18, 2003)

TunicaTrails said:


> That's a climbing turn which is not possible on a hill as steep as what I built on. Did you read the jist of this thread? Welcome to the Tunica Hills blufflands, jackass.


You're wrong.

There isn't any reason why a platform turn is inherently superior to a properly designed and constructed climbing turn. The reason for that is that a climbing turn does not necessarily contain a fall line section of trail if it's done properly.

And yes, I read and understood the thread. Your situation isn't unique, and there is more than one way to get a good solution. IMBA doesn't have a lock on the truth.

Walt


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## cmc4130 (Jan 30, 2008)

just wanna make sure i'm getting the terminology straight....

are y'all saying this is a platform turn (roughly) because the area where the bike is has been flattened out....










whereas this is a climbing turn because there is a declining gradient throughout the turn?










btw, these pics are from Vail.


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## special O (Mar 19, 2004)

cmc4130 said:


> i enjoyed reading your articles. especially the illustration of the turns which cut back uphill/upslope before doing a slightly-more-than-180 turn.
> 
> 
> 
> ...


J. Johnson defines turn radius at the inside of the turn. So I would say the stairs would be a zero radius turn. The radius of a spiral staircase would be half the diameter of the center column.


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## J. Johnson (Feb 20, 2011)

Cmc4130: I appreciate your interest, but you should be more careful about not copying copyrighted material without permission. While I might be willing to acquiesce, the second image isn't mine -- I got permission from the original photographer to use it on my web page (SBTP: Switchback Theory and Principles.), and it is not in my authority to grant use of it here. I would suggest that after a few days (when folks have had a good look at them) you might replace the copies of the images with links to them.

As to your question: yes, just as Wally said, the staircase shown would be effectively zero-radius. (Well, perhaps a radius of about one-eighth of an inch on that plaster trim?) In the nominal "zero-radius turn" (second image) the original caption notes (see SBTP: Geometrical Derivation of a Switchback. that the two curb logs forming the apex do form a radius of about eight inches.

The point of this exactitude is that 1) any turn (arc) of zero radius has a _circumference_ (or length of arc) _of zero_, and 2) _any_ vertical rise that has a horizontal run of zero will be a step. Assuming that one is _not_ building a step, a level platform is thus a consequent of a zero-radius turn.

For sure, people tend to _curve_ around corners, which therefore admits of some run, and some rise, and thus a "climbing turn". The strictly level "platform turn" is just the special case of a turn of zero radius.


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## TunicaTrails (Jun 29, 2009)

The switchbacks in our loess soils are holding up pretty well. I suppose if I'd done this before I could do it right the first time, but I'm sitting back to see which way the water channels. Right now we've got some ruts over the top of the transition in the second switchback. Everything else is ok although there has been some sloping in the steep face I cut out for both switchbacks that makes the radius tighter.

I pretty much expected those things to happen. I think it means I need to dig back farther this Fall and also cut a culvert around the inside of the turn as diagrammed. 

I was in New Orleans this weekend lending a hand to revive their trail that was under 10 feet of water for a couple of months. I noticed how much less "stick" the dark brown and gray soil had compared to our red clay, it was like angel food vs ice cream cake


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## HighFivenWhiteGuy (Apr 5, 2011)

A lot of good stuff on here already, but here's my two cents...

http://forums.mtbr.com/washington/cuss-hollow-now-open-business-697410.html

Check out the pics towards the bottom. VERY tight, VERY steep up and downhill switchbacks. Good luck with your project!


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## cmc4130 (Jan 30, 2008)

HighFivenWhiteGuy said:


> A lot of good stuff on here already, but here's my two cents...
> 
> https://forums.mtbr.com/washington/cuss-hollow-now-open-business-697410.html
> 
> Check out the pics towards the bottom. VERY tight, VERY steep up and downhill switchbacks. Good luck with your project!


Just wondering . . . do you guys actually like turns that are that tight? J. Johnson recommended a 24" inside-radius for turns (which also seems very tight, assuming a 2-3 foot wide path).

I personally feel like turns that tight only work at very slow speeds. And with downgradient riding, you'll just have people skidding into every one of those slow speed turns. Is this a case of wanting riders to ride slowly because it's a mixed-use trail?

If it was my trail, I would bank/berm those turns, and/or make them wider-radius. But then again my main background is DJ//FR/DH/BMX, so I love banked turns. I am willing to have an open mind though; some xc purists apparently hate banked turns.

























pics from this thread:
https://forums.mtbr.com/washington/cuss-hollow-now-open-business-697410.html


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## Skookum (Jan 17, 2005)

cmc4130 said:


> Just wondering . . . do you guys actually like turns that are that tight? J. Johnson recommended a 24" inside-radius for turns (which also seems very tight, assuming a 2-3 foot wide path).
> 
> I personally feel like turns that tight only work at very slow speeds. And with downgradient riding, you'll just have people skidding into every one of those slow speed turns. Is this a case of wanting riders to ride slowly because it's a mixed-use trail?
> 
> If it was my trail, I would bank/berm those turns, and/or make them wider-radius. But then again my main background is DJ//FR/DH/BMX, so I love banked turns. I am willing to have an open mind though; some xc purists apparently hate banked turns.


Most people don't like em. 
The builder took it upon himself to build this trail, going against the grain of the park and what it was intended to provide. Trails with flow. 
The justification was to provide a quick side-trail to give people practice on excessively tight switchbacks. And it does that.

i think the XC purist mentality that switchbacks SHOULD be super tight is misplaced. Really most of them are trails that never originally took mt. biking under consideration. So they were built with hiker mentality. That being said corners that are heavily bermed might not be great for a trail with high traffic, switchbacks can be good to slow traffic in some cases. So the opposite side of the spectrum is to say that all switchbacks should be insloped with big berms you can rail.

Every trail and each corner should be built on a corner by corner basis imo.


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## TunicaTrails (Jun 29, 2009)

^ Note that in the trail above, there are relatively tight switchbacks on a relatively low grade. Also they're apparently downhill. This is not the situation that the OP, yours truly, faced. Flow is a vague term to me and I disdain using it and "sustainable," because I think most people misuse them, or don't use them constructively, but pejoratively. Quoting an IMBA standard is more in line with numbers, and I can live with that.


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## HighFivenWhiteGuy (Apr 5, 2011)

The trail above featured climbing and descending switchbacks. Like skookum stated, it was designed and built to be a challenging skills trail to practice tight turns and obstacles on a steep climb or descent. Oh and hard to tell from the pics, but the grade was VERY high, hence the blocked corners to prevent skid erosion. 

As far as berming goes I would again have to agree with skookum here, it depends on the trail. Building a freeride, jump line or flow trail? Berms are a must have. XC or back country trail? Berms are a maintenance and water management nightmare, plus they only benefit bikes at the cost of other user groups. 

I have read the IMBA, USFS, and my local county trail standards and have a few things to say about them. First, they are mostly meant for multi-use, back country trails. Because of this they are conservative designs with maximum sustainability in mind, not the fun factor. Second, they are general guides, take them with a grain of salt. After all, that's the fun of building trails... creating a trail based on the materials, manpower and environment available, creating trails that are unique to their individual locations.


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## Skookum (Jan 17, 2005)

HighFivenWhiteGuy said:


> Berms are a maintenance and water management nightmare, plus they only benefit bikes at the cost of other user groups.


Well i wouldn't go that far.

Berms if done correctly can be little to no maintenance. As far as water management, i always tell people that they should envision your shoulder to be the start of a turn, a berm to be an elbow, and their hand to be the latter part of the trail. If when you envision your routing, in any circumstance where the elbow is lower than the shoulder and the hand, your boned. Unless you cheat and use some form of culvert to drain the water off to the backside of the berm.

Hopefully that just doesn't confuse most people... But the key is ALL in the routing, the common folly is to put a berm at the bottom of a turn, and it always turns into a maintenance problem.

Finally i think it's best if all corners/switchbacks, if not berms, should be insloped with a grade reversal of the low side. It will greatly reduce the wear, now the tires will work with the contour of the trail. Flow when concerning trail building is having a grasp of how tires work with the trail.

Yes there is something to be said of stalling and doing a nose wheelie kicking your rear wheel out to do a super tight switchback. But most people are going to skid out and sluff out a tight switchback till it's not only unrideable, but difficult for other trail users to use as well.

Thus is my opinion and philosophy on the subject of corners as i understand it today.


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## smelly (Jan 15, 2004)

HighFivenWhiteGuy said:


> Berms are a maintenance and water management nightmare, plus they only benefit bikes at the cost of other user groups.


Not my experience at all. They, like most trail features, are only a headache when not properly built/placed. And many trail runners like berms, so the berms don't only benefit bikes.

Anyway, I hate those super-tight switchbacks, and I've yet to ride a trail or trail network (in the hundreds of trails I've ridden around the northeast and east coast) that has them and makes them work. At best, they require slamming on the brake and killing your momentum, at worst, roots pop thru and make it unrideable in either direction.


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## special O (Mar 19, 2004)

I must be weird. I love super tight techy slow switchbacks. Uphill is even better. No stops. No dabs.


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## Visicypher (Aug 5, 2004)

You aren't weird special O. I like 'em too.


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## Skookum (Jan 17, 2005)

special O said:


> I must be weird. I love super tight techy slow switchbacks. Uphill is even better. No stops. No dabs.


Again every corner is different.

i just stop to think about how many switchbacks i've ridden, some of them with super high consequence. If you fall off the bottom side you're going to fall 30 or more feet. There are alot of smooth riders who understand how to use alot of front brake when cornering, but there are a ton of "sloppy" rider, who have years in the saddle but they still skid their rear in cornering, even at low speed. Switchbacks get even tighter and tougher as the bottom side sluffs out, shrinking the radius by a hair every season.

So if a trail becomes more popular, i just think inslope is the way to go. Inslope does not mean berm. Just to be clear if any reader is confused a berm is an extreme inslope.

And since there are many backcountry trails around these parts with with super tight switchbacks, to me it's not like we should be looking to protect them like they are an endangered species.


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## J. Johnson (Feb 20, 2011)

Careful! My recommendation for a _minimum radius_ was for _hiker_ trail. Bikes tend to go faster, so should have a wider turn. How much, I can't say, as there are just too many complications.


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## Fattirewilly (Dec 10, 2001)

cmc4130 said:


> just wanna make sure i'm getting the terminology straight....
> 
> are y'all saying this is a platform turn (roughly) because the area where the bike is has been flattened out....
> 
> ...


First pic is a platform or switchback. Ideally, (perhaps its there and I can't tell from the pic) it would have a bit more of a "pitchers mound" in the middle, the top leg insloped, and a drain going out near the back tire of the bike.

The second pic is an insloped turn or berm-turn (not as good as your work...but perhaps slight enough to appease a hiker oriented land manager). The foot and tire traffic location is different than where the water runs off. A climbing turn basically has nothing constructed, it just turns up and across the fall-line. The tire and water run in the same area.


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