Curved Japanese style bridge support

[StevieB]

I have been asked if I can make a Japanese style bridge to span a pond. The span of the bridge is to be approx 8 feet, with a height above the water of approx 12 inches at the highest point. The question is, how would you form a curved support of this length? I cannot see its feasible to use a single piece of timber since it would have to be 8 feet long and 12 inches wide plus the depth of the support itself, say 18 inches wide in total. There will be alot of waste once the curve is cut, making it expensive.

My idea was to use 6" x 2" joist timber and use 3 sections to form a support that would be 4" deep and 2" wide - the 4" thickness from a 6" depth allowing me to form the curve with less wasteage. I then worried that this would be strong enough, so thought about doubling this, making the joins in different places and bolting 2 of these together for each side to give a 4" by 4" curved support.

Anyone ever done anything like this or have any better ideas? If the above is not clear (reading it I'm not sure it is!) I will try and post a picture to show what I mean.

Cheers,

Steve.

 

[jasonB]

The doubled up timbers with staggered joints should work our fine, plenty of screws/bolts from the inside face and some PU glue will give a strong beam.

Jason

 

[ProShop]

Do you mean something like this :?:

 

[dedee]

Steve,
is there anything here that might help?

http://pacifi.ca/assembly.html

Andy

 

[StevieB]

Hi Felderman, yup thats exactly the type of thing but it will have handrails etc as well. I have only been given a verbal spec as to the width and length hence the 'approx' in my original post.

Did you form those supports from a single piece of timber? If not how did you go about joining the sections to make the curve?

Deedee, yup, found that site but it loses the single curve typical of Japanese bridges. Interesting design though.

Many thanks,

Steve.

 

[j]

Could you make it out of layers building up at each side, and have each layer getting closer to the middle.
Kind of like building an arch way.

Hope that makes sense.

 

[StevieB]

As a rough idea of what I had in mind, below is a half completed image of the bridge, together with a picture of how I planned to do the support rails:

Hopefully that makes things a little clearer!

Steve.

 

[jasonB]

I think it would look better if the top of the "hand" rail followed the curve of the bridge, you possibly don't need all the spindles either.

Something like This

Also don't make the curve too steep, I used to have a 6ft bridge with about 3" rise and that got very slippy in the wet weather, keeping the tread surface as sawn will help, mine was planned cedar.

Jason

 

[StevieB]

I agree with you Jason, but the client specifically asked for the posts and rails to be that way - they have some budda statues or something that they want to fix to the top of the posts (Hey, I just have to make it, not admire it!). Good point about the curve though. Client wants the bridge painted black and red but I will suggest some form of non-slip coating over the planking for the wet weather.

Cheers,

Steve.

 

[ProShop]

Hi Felderman, yup thats exactly the type of thing but it will have handrails etc as well. I have only been given a verbal spec as to the width and length hence the 'approx' in my original post.

Did you form those supports from a single piece of timber? If not how did you go about joining the sections to make the curve?



Steve.

Hi Steve,
Yes it's one piece of timber, it's just shy of 6metres, I cut the curve using a cheap chipboard template I made. If you look closely you can see the offcuts from the top ends of the curve have been fitted to the end underneath which helps to finish the curve (hope thats clear ). It now has some posts morticed into the ends and 3 more equally spaced across the bridge ( I used a newal post design to make the posts, then I drilled the tops to fit the style of post I wanted ( a bit like doing a staircase newal posts).

Hope this helps

 

[StevieB]

Many thanks for the info John

Steve.