Ok…
I can frame an elliptical arch.
And I can frame a curved wall.
What I am having a tad bit of difficulty figuring out this morning is…
How do I frame an elliptical arch into a curved wall?
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Replies
Do you mean like the sketches in the last post in the Barrel Vault Thread?
The framing details I can't help with, I'm just a "math guy". This topic came up in the JLC Forums last year though. Some of the folks posted pics. They used plywood ribs. I'll be back shortly to post a link ... if I can find the thread.
When you've plotted your ellipse, you can make a copy of it(in ply or other). Then attach dowels thru both ellipsi in the same plane, along the plotted points. At one end these points will touch your curved wall, and this is where you layout the ellipse.
Edited 12/15/2006 2:42 pm ET by jackplane
Link to the arched window/cove ceiling intersection thread.
The link to the picture I was thinking of isn't working ... but you might be in luck. Tim Uhler posted it. I think a guy with that handle hangs out in this forum. :)
Bill Boyd also posted some images in that thread.
Joe Bartok
Edited 12/15/2006 2:49 pm ET by JoeBartok
--
"When you've plotted your ellipse, you can make a copy of it(in ply or other). Then attach dowels thru both ellipsi in the same plane, along the plotted points. At one end these points will touch your curved wall, and this is where you layout the ellipse."
--Yeah, that makes sense, however, I need to frame the curved wall and the arch all at the same time. I don't want to completely finish one wall and then cut into it to install my arch framing.This is less of a concept question and more of a construction question. I can lay out the ellipse easy enough on flat stock and then bend it to match the curve of my wall.I'm just not sure how I'm going to get my arch framing to <i>stay</i> curved through the entire plane of the opening.Seems to me that the bottom of the arch opening would try to flatten out.Kind of like holding a piece of paper up in front of you, by the two top corners. If you pull the top corners towards each other, the bottom corners do not maintain the same curved surface. Even if the bottom corners were held in place by the wall framing, seems like the bottom of the arch would still want to flatten out.I suppose I'll just make the arches, bend them and see if they hold the curve. I was just wondering if anyone else had done this type of thing before.=-)
I'll be following this thread with interest. All I can think of is make a jig and bend the wood (the 2 × 4's) to conform to the curve at each side of the opening.
Joe Bartok
Edited 12/15/2006 5:13 pm ET by JoeBartok
Edited 12/15/2006 5:15 pm ET by JoeBartok
I don't want you to follow the thread Joe - I just want you to tell me how to do it!<grin>
I belatedly thought of something better last night after logging off. Instead of bending wood why not cut the arches out of plywood? Make them two or three thick if necessary to make them rigid enough to support the two by fours.
The elliptic opening (actually the projection thereof) can be made out of one sheet of plywood and will easily bend when secured to the arches.
I'll try to get back later and post a scan of a sketch.Joe Bartok
Hi Joe - Yes, of course the arches will be shaped out of 1/2" ply, just as if I were framing a typical arched opening.I probably didn't explain myself well enough.The 2x material is just for spacing between the 2 pieces of 1/2" ply arch faces.So, imagine 2 pieces of plywood that have the shape of the arch cut into each piece. In between the 1/2" arch faces, there are 2x4 spacers that make up the depth of the arch. Kind of like a box I guess.Then, typically, I would just lift the whole arch box into the framed , rectangular opening (in the wall) and fasten the arch box to the opening frame.So, if we have a curved wall, the sill and top plate of the will be curved (plan view).I can make the top "plate" of my arch box curved (in plan view) to match the wall, so the top of my arch will maintain the curve. However, the bottom of my arch is wide open, so I just can't figure out how to maintain the curve at the bottom of the arch?Now I'm thinking, perhaps, instead of just making the actual arch box out of plywood, perhaps I need to make the entire opening out of 2 pieces of plywood. Basically from floor to ceiling, front and back, using a curved sole, a curved top plate, and a curved sill for the opening.If my rough opening is, say 30" width by 48"" height, I would just cut the entire opening into two vertical pieces of 4x8 1/2" and then screw those pieces, front and back, to my curved sole, sill and top plate.I could then add 2x spacers to maintain the depth at the bottom of my arch.
Nuts! I just spent twenty minutes typing and lost my post ... just as well, I don't think it would have helped much. Here's a sketch (you had this figured out anyway).
The plywood with the projection of the opening at the intersection (not shown on the drawing) would be mounted on and follow the curve of the arches. A series of plywood ribs with two-by spacers are secured to this.
Joe Bartok
Edited 12/16/2006 10:30 am ET by JoeBartok
A rough (really rough!) sketch of what I mean by "ribs".
Twofingers: The intersection I'm showing is a projection of one arch to the surface of the other. Upon re-reading your post I'm beginning to wonder if I understand what you are making. Is this a curved Valley beam you need?
Joe Bartok
Edited 12/16/2006 10:46 am ET by JoeBartok
Ahh yes - the drawing you sent of the elliptic arch intersection?Well, turn the drawing 90 degrees. so the curved rafters become plates and sills, and the purlins become jack studs and the ridge beam becomes a king stud.So now what we have is a rectangular opening in a curved wall.Now imagine that the rectangular opening must become an elliptical arch. So you no longer have those double plates (rafters on your drawing) at the top of the opening because that is where the arch has to be.Does that make it any clearer?
Edited 12/16/2006 11:59 am ET by twofingers
Ah ha! Much clearer ... gotta go think about this some more. Whatever good that will do, I've never actually framed anything like to this.Joe Bartok
I hope two fingers derived his name from his drinking preferences vs. his sawing skills on arches...LOL
Spheramid Enterprises Architectural Woodworks
I have irriatable Vowel syndrome.
Agreed! :)
Before I'm shut down for the weekend I confess ... I'm stumped. You'll have to post some photos of the solution.
Will framing the opening by adapting the rib method (prefab this part?) will hold its shape??? The strongest thing I can think of is to install a curved beam at the intersection. So it's back to bending wood again, similar to the "curved Valley" but rotated to different axes. It seems easiest to cut and bend a metal arch. Is there a shop near you?Joe Bartok
"I hope two fingers derived his name from his drinking preferences vs. his sawing skills on arches...LOL"
Actually I assumed the "two fingers" referred to the drinking preference: two fingers of Johnny Walker. Sounds like a good way to celebrate if we can figure out a way to saw these arches.
Joe Bartok
I can use Sketchup to draw the shape of a curved wall and extrude its shape up as a solid.
Sketchup doesn't have a function for drawing elliptical curves, but if given an array of x/y points, I can certainly connect the dots and do a shape that way, then punch it through the wall.
With the opening shape punched through the wall, I can create a plan for framing.
The funky issue to be dealt with is the creation of some sort of header. I can envision it being done as a laminated curved beam, sized with enough depth to handle the entire curved head, and its curved underside being roughed out with a chain saw.
Can you post a jpg version of the drawing. I don't have Sketch Up.
It shouldn't be too tough to develop the curve. Correct the value of x for the opening to the wall ellipse arc length on the x-axis, opening height on the y-axis.
PS: Or bend the beam to the elliptic curve as viewed in plan and cut the bottom with a chain saw as Gene suggests. This last could be done by making a plywood template of the opening and projecting the curve rather than plotting points.
Joe Bartok
Edited 12/16/2006 2:43 pm ET by JoeBartok
Edited 12/16/2006 2:44 pm ET by JoeBartok
Edited 12/16/2006 3:16 pm ET by JoeBartok
Not being a wise azz, but is a header needed? We have a curved wall, with an elliptical ( arch, in my mind) hole...did the Romans use headers on the openings of the Colosseum?
Spheramid Enterprises Architectural Woodworks
I have irriatable Vowel syndrome.
I can't find a good close up image so I could be jumping to conclusions, but: didn't the Romans use stone arches in their openings? That would be a kind of header.
Joe Bartok
Edited 12/16/2006 3:38 pm ET by JoeBartok
Well yeah, they used stone and early forms of concrete, but even a wooden arch is in compression at the head and directly transfers load to the "legs" as long as there is not a spread of the legs, it stands up.
So, In my feeble mind sheathing will counteract that or a buttressed framing.
Spheramid Enterprises Architectural Woodworks
I have irriatable Vowel syndrome.
From a force point of view it's probably OK. I'm still having a hard time visualizing something that will hang together in the right shape until the last nails are in place. No surprise there, though. It took me a while to figure out which way the ellipses were oriented. :)
Go figure; I'm getting cut off the Internet in a few minutes just when this thread is getting interesting. I'm looking forward to catching up on all the posts next week.Joe Bartok
Well DO come back! BTW, I find your calculators immensly helpful!
Spheramid Enterprises Architectural Woodworks
I have irriatable Vowel syndrome.
The way I do it is to to cut my top plate 5 1/2" wide. Then I cut a header plate 3 1/2" wide which leaves a 1" reveal when nailed under the top plate. Then I'll build a "curved ladder" type header, which I can skin with two layers of 1/2" plywood on either side. Now let's say you have an ellipse with 12" of rise and from the top of the ellipse to ceiling height is another 12". First build the ladder then rip your plywood across the grain (it bends easier this way) and cut your arch into it. It will be a 21" rip if you have 3" of top plate with a 12" rise for the arch. Your ladder height will be 9". Measure the chord length to determine your major axis. Cut the arch to fit and nail it.You have to measure both sides of the wall because one will have a 6'8 radius and one will be 6' 4 1/2", but it's close. Using the ladder type header and having an extra 9" of solid plywood helps it to hold the shape. It's really easy, just a little more time consuming that a regular arch opening.John
It's more fun if the legs spred and don't just stand up
After thinking about this for a few minutes. I'm thinking that the x (level) axis of the flat ellipse would change when it follows the radius. So if you treat the flat ellipse as a chord and figure the length of the circumference between the chord ends. Then use this as a new x axis length. Lay out a new ellipse on a piece of thermoply or something bendable and then lay it on the wall and mark your cut out. I'm not sure about this but I would try this first. Its not that labor intensive to see if it would work.
I've done a few and from my experience it's best to cut a piece of a least three quarter inch ply to fit in you curved wall. After you layout and cut your arch you then nail the front and back face of the arch to the ply giving it the same curve as you wall.
What about something like this drawing?
View Image
If you glue plywood on the framed header, it could be a load bearing box beam, I think, all though that might be tricky since you can't center the header between the jacks. An engineer would have to handle that part.
I'd sheathe it, and bend a strip of plywood or three on the bottom, then cut it off flush with the sides, if you see what I mean. I couldn't really figure how to draw that on this program, but it shouldn't be too hard to make it in real life. Like I said, structural is tricky because the moment of the support would be cantilevered out. So the plywood or whatever it was that was providing that structure would have to tie back into the wall quite a ways, I would think. But I'm no P.E., so don't take my word for it.
zak
"When we build, let us think that we build forever. Let it not be for present delight nor for present use alone." --John Ruskin
"so it goes"
Edited 12/16/2006 9:51 pm by zak
Did he say a load was on it?
DL=40 right?( just the safe parameter) the arch= < sqftx3.14r2..by x, x=load. assume a DL of 40 =x...
I might be as cornfused as the next guy but, I confused myself as far as a header value, I think I can field build and pass any inspection.
I see a dog trot into a vertical wall IGLOO..there is no LL, just DL..call that 100 instead of nil, work from that you find a saftey factor of 50% at least..always plat it safe.
Spheramid Enterprises Architectural Woodworks
I have irriatable Vowel syndrome.
Didn't entirely follow that but. . . .
Whatever your depth of beam is for the header, the connection between the header and wall is critical. If you looked at a section of the wall, you'd see that the center of the header is cantilevered out past the supporting kings/jacks, even if just a few inches.
So the tension connection between header and wall is critical, so the header doesn't sag by leaning out/down at it's apex.zak
"When we build, let us think that we build forever. Let it not be for present delight nor for present use alone." --John Ruskin
"so it goes"
I don't know the load...so I can't tell ya for sure, but a WAG says no header is needed.
Spheramid Enterprises Architectural Woodworks
I have irriatable Vowel syndrome.
I'm with ya there- I would still tie a little plywood back into the rest of the wall, just for the DL.
I doubt that a curved wall would be under another curved wall, or be supporting floor joists.zak
"When we build, let us think that we build forever. Let it not be for present delight nor for present use alone." --John Ruskin
"so it goes"
Yup even if it was, the plate oughtta be it..simple, but complex at the same time.
Spheramid Enterprises Architectural Woodworks
I have irriatable Vowel syndrome.
I tried to find it, but I couldn't Rustynail over at JLC used to have a pic on his website that was a curved wall with an elliptical opening in it. You might go over to JLC and PM him for a pic and description. He does some really great work.
Duh..call or see and pay..CloudHidden.
Spheramid Enterprises Architectural Woodworks
I have irriatable Vowel syndrome.