GD, I’ve done a lot of it both ways, but mostly I cut a 2×10 or 2x 12 rafter, then cut the swoop out of it.
I often sheath the roof with 1 x 3 utility boards. Sometimes I use 1 x 14 utility. Quite often the last bord is ripped from a 1 x 6.
I have used 3×8 ply. I don’t like to use osb products because they tend to break, rather than bend.
blue
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Blue, easy enough to imagine a simple radius as the 'swoop' cut in each rafter, but how do you get the matching swoop in your hip rafters?
"how do you get the matching swoop in your hip rafters?"
Swanson's Speed Swoop?"he...never charged nothing for his preaching, and it was worth it, too" - Mark Twain
if you know the radius of the main swoop, multiply it by 1.41 for the hip swoop radius
Makes sense... 17 over 12... so your vote is for layout with a trammel arm?
That doesn't work.
It worked pretty well when I built these poolhouses.
jayzog, that's an interesting roof but I don't understand how that formula applies to laying out a hip roof. Obviously, you made it work. That underframing looks awesome.
blue
I often use my CAD package to work out solutions in building. The attached image is from a file I just built.
A 6:12 pitch is shown, with a curve on it. Disregard the fact that it is looking as if it is convex, rather than concave. It is because of the view I took (upside down and anaxonometric) to display the 3D model.
The curve at the common is a true arc . . . a circular segment. Its projection onto the 45 degree plane is not an arc, but a conic section.
Although the hip curve is a conic, it can be closely approximated with an arc. You would want to do this if you are going to swing the curve with a trammel.
In this example, the ratio of radii, common to hip, is a little over 1.7.
The dashed lines show how a straightedge might be used to define the points along the hip curve.
The projection of curves onto skewed planes is best left to professionals. ;-)
My CAD program will do it for me, but I'll bet for something like that small portico roof, you could do it with a straightedge. Erect your commons with their curves, lay up an uncut hip, use the straightedge to project a series of points onto the hip blank, connect the dots and fair the curve, then fire up the bandsaw.
I found a way that is ez. Draw the common on a sheet of ply at one edge, divide it with step-offs ( dividers duh) equally. Extend the points to the far edge ( this may take two sheets side by side, depending on size) and there make a 45 degree base line. Where the division lines intersect the 45 line is where you connect the fair swoop points.
I just did this last week for where a 1/2 round roof vent intersectes a 12/12 roof plane, I needed to find the ellipse shape of the valley plates.
Ez-er to do than say, I am afraid.
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Sphere, I vaguely remember doing something like that in my high school drafting class. But, I cant fully understand what your saying.
Is it possible that you might add a little detail or picture to your explanation? I doubt that I'd ever need to use it but I still like to know the process.
blue
I can't draw worth a hoot on a puter, but here is really ruff way to show it..I did a scale on paper to remember how ( like you, from drafting class) then full size on ply wood..this is the concept. connect the lines intersections at the letters.
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Thanks Sphere....I now remember the concept and see how I could make it work for me.
For funnsys, I'll use that technique on my next swooped roof.
blue
glad you could make sense of it..LOL
been almost 30 yrs since High School drafting, amazed I remembered most of it.
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Stinger, I cut all my swoops with my power saw. Usually, the dimensional lumber we use is 2x12 hem fir or doug fir. The power saw easily makes that type of cut in about 3 passes. I often work the saw (sidewinder, blade right) backwards because the blade and rotation tend to create an arc if you let it follow it's natural tendencies.
Understand, that this technique is being done on a rough framed roof that does not have to have a finished appearance underneath like your work did. Obviously, if underneath appearance was a factor, a more precise method of cutting would need to be employed.
blue
I'm not properly insured to use your saw! ;-)
David, in most cases, the roofs I'm covering are relatively small surfaces: bay projections, boxed out window projections, etc. Although I appreciate the fact that mathematical formulas can be used to derive the configurations, I don't spend any time trying to determine them. Instead, I use my eyes.
In most cases, I literally draw the swoop freehand on the common rafter pattern. That takes me one second...two seconds if my first attempt doesn't please my eye. After cutting and installing the commons, I cut the hip to length and lay it in. I then scribe the hoop-swoop using a straightedge off the commons. This process is by far the most complicated and time consuming aspect of the job...it takes me about 30 seconds!
Obvioulsy, this technique is not going to be effective on long rafters and larger roofs, but I've never been faced with having to do any of them. If I did, I'd be in here asking for technical advice from guys like Sphere.
blue
Thanx to all. Don't know if the 1.41 multiple factor will work as this is an irregular hip, with the hip rafter not a 45 degree angle. Like the idea of shooting off the commons onto the hip to transfer the curve. I love math, but sometimes you can overcomplicate things.
It will be interesting because they do not want a flat ceiling. Initially they wanted the roof to be ####flat slope (not curved) and the 'ceiling' to parallel the roof. I'll have to find out if they now want the 'ceiling' curved to match the roof. Hopefullly not.
As it's my first such job, and as it's a small roof, I might just pre-build it in the shop. More comfortabe working on the ground, not to mention access to the band saw.
Let's not confuse the issue with facts!
I must have missed something along the way. Is the picture in the original post what you're building?
If so, we simply have the metal-gurus built it to our dimesions and install it in one or two pieces with no curved framing required. Maybe it's larger than what I'm thinking of, but in that case the framing is more like curved blocking above the entrance than what would be considered roof framing since it doesn't have to be self supporting, but rather can simply sit on the flat framing of the entrance.
The morning coffee has worn off so I'm probably missing something. :-)
Beer was created so carpenters wouldn't rule the world.
Having been a metal guru all last summer, I can attest that a standing seam copper roof NEEDS a frame under it, and sheathing.
Unless you are refering to an aluminum awning.
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dude, use heavier metal and save us all this framing hassle!
Sure, at 4 bucks a pound, I'll save ya some wood...LOL
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Sphere,Check out this site.Also Anderson used to make the copper roofs for their windows with no framing underneath. I don't know if they still do though.http://www.proofroof.com/http://www.proofroof.com/installation.phpJoe Carola
I was refering to the OP's porch installation. We still apply over a solid sheathing, for permanant attachment.
I guess for some folks a bay window lid like that would be OK, but I'd still prefer something substantial below it...I bet a hail storm sounds like the drums of Ummbapamoauwow! (G)
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They have it for that also.http://proofroof.com/photo_gallery/canopies/Joe Carola
Ok, Ok...shhhhhhhhh. I need my job.
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The photo is just what the client e-mailed me as to the preferred visual appearance. Actual roof will probably be about the same size: roughly 10' wide by 6' deep.Great client, knows exactly what he wants as soon as the missus decides.Had fun buiding sliding gates to keep his dogs off the rear deck so they don't scratch at the doors. Used 2 sets of pocket door tracks and wheels for each sliding gate. Funnest was installing a set of Bessler attic stairs. They're large.Let's not confuse the issue with facts!
We do add framing, but not curved framing, and simply shoot expanding foam to bridge the gap.
I'll agree with you that some kind of support is needed, it just doesn't necessarily need to be a perfect match to the metal cap.
Beer was created so carpenters wouldn't rule the world.
>>>>>>>>>>>Also Anderson used to make the copper roofs for their windows with no framing underneath. I don't know if they still do though.But, they fabricated them on a frame and they had relatively short spans. I've done several custom bay roofs to be installed by others. I got a set of plans, built a mock-up frame in the shop and fabricated the copper roof on it. Remove the skin and loaded it up in someone's pickup. Price would have been about the same, had I installed it on site. I just didn't have to travel from my shop, but I had to build the form.Birth, school, work, death.....................
http://grantlogan.net/
gdarpenter, that roof can be treated as an upside down cross vault. Here's a link to a thread in the JLC Forum ... leading to more links on Framing a Cross Vault. The math relates to cutting purlins but there's some material on how to project irregular elliptic Hip/Valley rafters.
Hope this helps.Joe Bartok