I’m designing and building a non-structural gable truss (you see alot of these in the Rocky Mountain area) to spruce up a blank gable, using cedar 2X4s.
See the crude drawing attached.
The pitch is 4/12, the length of the bottom chord is 10′. The truss pieces will be cut and assembled in the shop. The short angled pieces will be something other than at a 45° angle from the bottom chord. If they were 45° this wouldn’t be a problem. I think I will draw this out life size on my garage floor to get the angles at the bottom chord ends, top of the vertical piece, and tops of the angled pieces.
Question is what’s a good technique to figure the angles, mark and cut the 90° (pointed to by the arrows) at the bottoms of the angled pieces so they’ll fit with no gaps? I have a SCMS. I can tolerate some trial and eror, but think there must be a best practices technique that eliminates most of it.
I’ve already cut and assembled a full-size template from plywood, but only was able to get a rough approximation of the correct angles at the bottoms of the angled pieces.
Kind of hard to explain, but I hope the drawing helps….TIA.
Replies
For that type of issue (never done exactly what you're doing but if I need to figure angles and dimensions of an involved assembly . . .
I draw it using Turbocad and it will calculate the missing angles and dimensions.
You can even plot full sized templates of the joints if need be.
"Let's get crack-a-lackin" --- Adam Carolla
Unfortunatley, I don't have any design software, and don't get into this sort of stuff enough to justify...but thanks anyway.
No problemo. You can get "trial" versions free.
I only use Turbocad 'cause I learned how to use it long ago and I don't want the learning curve of another program.
There are lots of free drafting programs.
If you want to try Turbocad, go here and click free trial. You get 15 days free.
http://www.turbocad.com/
A lot of guys here seems to use Sketchup. I think you can get that free too.
"Let's get crack-a-lackin" --- Adam Carolla
If you can scribble some dimensions on that I'll draw it up in cad and post the drawing back with angles noted.
2x4's for the top and bottom cords?
How far from the inside peak of the gable is the top of the bottom cord ,
How wide are center supports?
What angle do you want the small angled pieces to be?
Is that 10' measurment from the bottom or top of the bottom cord?
If I were going to do it and didn't have a cad program I would construct the top and bottom cord, add the center support, then rest the angled pieces where I thought they "looked right" and simply trace from beneath, cut them a little long and work my way down. To find the angle to use on my miter saw I would use a protractor.
Actually no top chord...they all butt on the soffit.
I think I'll go ahead and cut the ends of the bottom chord, then lay that out in the shop, cut the vertical and angled pieces long, cut the 90°'s on the angled pieces where they "look right", then use a long stright edge to scribe the tops with the angle, and cut away.
You can do all the math with a squared + b squared = c squared and a little trig.
It is simple math, just takes you time.
If you already have a full-sized template, why not use an adjustable bevel gauge to transfer the angles to the miter saw? Forget about what the numbers on your angle quadrant say, just line the blade up with the arm of the gauge and cut. For that matter, you could use a circular saw and get good results.
The problem I have with relying on the saw quadrant is that while your mathematics may be perfect, measurements aren't, and then there is the necessary interpolation that you have to do when setting the angle.
I kind of did it that way, first transferring the roof slope/angle to the ends of the bottom chord piece, which is a cedar 2X4, then fastening the piece to the gable siding, snuck up on the length and angle cuts for the middle vertical piece.
Glued and screwed the middle piece at 90° at the center of the bottom chord, then held the angle piece blanks to where they "looked right", cut the 90s, and stretched a string to arrive at the top angle cut.
Maybe you need a refresher course in high school trig.
You know . . I know trig Adj over Hyp, Opp over Hyp, . . .
But where are teh frickn tables when you need one!
And don't forget : a squared plus b squared equals c squared. You anc solve just about anything . . well . . you know what I mean.