20' span questions

[xulgiy]

I'm looking for some much needed help with a shelter build I'm planing.  I have my own mill, but it's only a 12 footer and I'm looking to make this shelter 20' wide.  Can I make a scarfed truss 20' wide with no support in the middle?  I was thinking i would use 12' foot 2"X8" lumber for the plate(?) and sandwich a 4"x6" king post where I'd scarf them...then use plate steel to hold it all together.  The posted picture is what I'm looking to construct, but dont have the capibility of slicing 20' lumber.  Any help would be great!

 

[S.Hyland]

You can create a king post truss with a two piece bottom chord. The king post extends past the bottom chord and joins them, usually with a large pass through spline joint. So yes it should be possible to use less than 12' lumber in this case. However, there are lots of variables as to sizing, metal plates etc. which will play into that.

[witterbound]

If you're going to use 2x8 beams, just go buy some that are 20 ft long.

[xulgiy]

Thanks guys.  I may go buy some, but that would not go over well with mother, as the mill purchase was "justified" by having "all the lumber we'll need right here!". 

[Remle]

I'd be adding 10 foot to the rails, the extension will pay for its self many time over the life of the mill, you may not need 20' consistently but 16' is a common length used in most construction..

[beenthere]

Thanks guys.  I may go buy some, but that would not go over well with mother, as the mill purchase was "justified" by having "all the lumber we'll need right here!".

Never box yourself into a corner.. and mothers can be forgiving and understanding. ;)

[Warped]

I've had good luck sliding the log down the track when I needed something longer than saw head could travel. Once four sides were opened up I took a few small bites to get a nice square cant down the length to get uniform boards.

[xulgiy]

Thats a good Idea.  Thanks!

[mrbrb]

This is one way of sawing a timber that is longer than your mill, and I'm sure it is explained elsewhere on the forum. In this case, we have  a 42' hickory beam on a 24' capacity mill. Let the log cantilever off the end of the mill, saw/rotate the section on the mill, then slide/roll your timber back to saw the other half, blocking it up on dunnage as necessary. This way, there is really no limit to the length you can saw.   

  

  

  

 

[Hilltop366]

Not sure what kind of mill you have but if it is a 2 track mill with angle iron for the carriage to ride on and not a mono rail you could cut some 12' lumber to make a extension, would only need to get some angle iron on it so the cost should be low.