joinery help on kingpost truss

[Don P]

Gilman, I realized when I looked up this post, nobody answered.
I'm no expert, on the truss here I laid out a plumb cut and then swung the base in 1" to create a seat. There is a 2x6 tennon laid out from the bottom of the rafter sticking in the king.

This is a more metal connected bent than the first one.


I kind of used a picture from above for an idea for a rafter foot on this bent. After this pic I welded an 8x8 plate from the heel angle iron up the rafter and sank 4  lags to help lock it in place. There are 2 more lags in the holes in the angle at the heel .


That way didn't save any time or money, but it is alot stiffer than the splined truss.

[Thehardway]

Gilman,  I have seen a lot of different configuarations and flavors for kingpost tops in books and pictures.  Some have no angle at all.  In many later designs, an Iron rod was substituted for the post which had no angle.  I like the angled version. The greater the angle the better the rafters lock the kingpost in place.  I believe the angle should be increased as the pitch increases. I say this because thrust and compression increases in the rafters as the roof pitch decreases, holding the kingpost tighter. The reverse happens as the pitch increases.  It is a Chinese finger trap principle.  Also much depends on the pitch of your roof and the size of your kingpost. An important thing to remember is that the kingpost is the only member in tension and all of the weight generated by the kingpost has to be transferred to the rafter foot joint. I started another post sometime ago on kingpost top configurations. I will try to pull it back up in a search.

Don,  What is the purpose for the strap visible on the top of the tie-beam in the lower picture? What does it attach to, the bottom of the rafter?

[Gilman]

Thanks

[Don P]

The strap with the 16-1/2" lags is the thrust resistance for the rafter foot  . It extends under the rafter and is welded to the angle iron behind the rafter. To get assembly room and proper spacing that got kinda long. Think about the amount of "meat behind a 1/2" lag and then the amount of shear resistance in the notched foot of bent 1. Just a different way of restraining that thrust.



Its unseen from ground level. The "spline" on this bent is 2 fish plates ~14' long let into the bottom chord across the king. There are 3-1" bolts in tension there on each side of the king.

[Thehardway]

OK.  Think I see it now.