# How to frame curved wooden features?



## phile (Mar 19, 2017)

Sorry, noob question. I'd like to add a small wooden berm to a tiny backyard trail. How are these usually framed if using 2x lumber--where does the curve come from? How are the joints/transitions between framing sections smoothed out? Thanks for any help!


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## HypNoTic (Jan 30, 2007)

This is a overpass we built 2 weeks ago. 6 layers of 1x5 glue-laminated create the 4 main beams. 4 layers for the ramp.

Climb trail goes under, over is the beginning of the jump line. The roll-in gives the exact speed to clear the line of 20-24ft tabletop and hip jumps.

Trail is located in Vallée Bras du Nord, Quebec.


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## cmc4130 (Jan 30, 2008)

phile said:


> Sorry, noob question. I'd like to add a small wooden berm to a tiny backyard trail. How are these usually framed if using 2x lumber--where does the curve come from? How are the joints/transitions between framing sections smoothed out? Thanks for any help!


This is going to be 'too much information' but, it'll illustrate various things about wooden berms.

*Bowled In with Ryan Corrigan (bowl building how-to)*





If you want the berm to have a transitioned (curved) face, then it's definitely more work. It's more like the wood bowl corner in the video above.









If you do the "ribbon twisting" style berm, you

Tiered berm at Duthie Hill, Seattle, under construction. 









Abel and Buddy,
Austin TX









https://forums.mtbr.com/trail-building-advocacy/wooden-berms-502865.html

https://forums.mtbr.com/trail-building-advocacy/looking-info-wooden-berms-walls-824784.html

FREERIDE 512


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## phile (Mar 19, 2017)

aha! That video was really the missing piece. Thanks a lot for that and the other info too. 

Is that a specialized saw, or just a nice worm-drive model? In skilled hands it really glides through the curved cut on the 2x6. In my hands, with a $40 harbor freight saw, I may end up with more smoke than anything else--any tips for making those cuts, besides practice and a decent saw?

Is the curved top piece at the coping (at the start of the video) just cut from plywood?


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## ray.vermette (Jul 16, 2008)

HypNoTic said:


> ...
> 
> This is a overpass we built 2 weeks ago. 6 layers of 1x5 glue-laminated create the 4 main beams. 4 layers for the ramp.
> 
> ...


Sorry for the thread derailment, but what trail is this on? Is this at Shanahan, or St. Raymond Sector?


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## life behind bars (May 24, 2014)

phile said:


> any tips for making those cuts, besides practice and a decent saw?


A carbide tipped blade set just deep enough to cut all the way through and patience. Look ahead of the cut, where you want to cut to, not where you are cutting. It takes a lot of practice to be good with a circular saw.


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## aero901 (Apr 11, 2012)

Straight lumber can be used to approximate a curve with multiple stringers joined at posts/piers aligned radially from a center point. You'll need 5-6 piers per 90deg of turn arc to make a pretty smooth transition between sections of decking but you'll never completely get rid of the transitions. More piers gets closer to approximating a true curve but with diminishing returns and much more labor. There are many images showing the framing layout for these structures out there if you image search for "wood berm framing". Making a small model out of craft wood & hot glue can help visualize how it all fits together as well.

This is one of the simplest 2x wood berm framing methods I've seen:








I designed/helped build three curved wooden berms a few years ago and we used resawn treated 2x4 material to laminate curved beams for the deck attachment structure and steam bent oak boards for the decking. Tons of work, but as close to a curved berm as you can get.





More images from the project here.

Shaky POV video from this section of trail here.


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## cmc4130 (Jan 30, 2008)

aero901 said:


> Straight lumber can be used to approximate a curve with multiple stringers joined at posts/piers aligned radially from a center point. You'll need 5-6 piers per 90deg of turn arc to make a pretty smooth transition between sections of decking but you'll never completely get rid of the transitions. More piers gets closer to approximating a true curve but with diminishing returns and much more labor. There are many images showing the framing layout for these structures out there if you image search for "wood berm framing". Making a small model out of craft wood & hot glue can help visualize how it all fits together as well.
> 
> This is one of the simplest 2x wood berm framing methods I've seen:
> View attachment 1142360
> ...


Wow!!!!!!!!

The only other one I've seen with curved surface planks like that is Mammoth. Mammoth Mountain Bike Park In California Opens This Weekend


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## aero901 (Apr 11, 2012)

I haven't seen many others but I'm sure they are out there. There is another curved berm in Copper Harbor, MI on the Overflow trail (one of the inspirations for our project actually). It looks like the Mammoth berm might use composite lumber (HDPE plastic + wood fibers). That stuff is really flexible and can be formed into a pretty tight radius by heating. It isn't very strong though and they warn to not use it for structural applications. We considered using it as decking but felt it would be too slick when wet and too flexy. It's also expensive (~$3 ln.ft.)


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## phile (Mar 19, 2017)

cmc4130 said:


> Wow!!!!!!!!
> 
> The only other one I've seen with curved surface planks like that is Mammoth. Mammoth Mountain Bike Park In California Opens This Weekend


agreed, that is really slick!


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## HypNoTic (Jan 30, 2007)

ray.vermette said:


> Sorry for the thread derailment, but what trail is this on? Is this at Shanahan, or St. Raymond Sector?


Toblerone (or, as we call it, Table-Run), St-Raymond area. Swiss mountain sector.


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