Replies

1. 
   UncleDunc | Dec 06, 2002 09:21pm | #1

   There is a type of plywood that is designed to bend in one dimension while remaining stiff in the other dimension. Do a web search for "bending plywood" or "bendable plywood". Other trade names or brand names I have seen are "wacky wood" and "wiggle wood".

2. 
   user-306759 | Dec 06, 2002 09:46pm | #2

   I built an arch support using with 2x4's and 3/4 plywood for the sides and bottom. The top was 3/8" plywood.  This plywood was easy to bend on the radius that I used by screwing one end fast and working my way toward the other end.  An alternative would be 2 layers of 1/4" luan.

3. 
   bd342 | Dec 07, 2002 12:32am | #3

   Take a piece of 3/4"cdx rip it in half. This will leave you about 23 15/16ths which for your purposes should be fine. tack the two sheets together and from the center of your long factory edge strike your arch using the edge as your zero line. By the way the radius of your arch is 39". Cut blocks out of 2x6 the width of your arch less an 1 1/2" for your plywood.( I would suggest using a miter saw for this because the truer your blocks are the more accurate the arch buck will be.)

   Nail the blocks between the two plywood forms about every 8"o.c.Next for the sheeting across the blocks if you cut 3/8ths ply across the grain you will find that they will bend very easily over that radius. If you do have some trouble just cut them and put the strips in a water tray for an hour or two.You also might want to glue the top edge of the 3/4 when your attaching your sheeting.

   sorry for the lousy writing ,but I hope this helps you out.

4. 
   ken1putt | Dec 07, 2002 12:33am | #4

   The arch supports I've seen around here don't have anything bent in them. And they are simple and strong.

   For typical arches in brick or stone veneer, over windows, for instance. The arch is laid out on a sheet of 3/4 plywood. For your arch, you could make 2 out of one sheet. They'd look like the letter D, laying on its back.

   For the 4-6 inch stone used on houses, a 2x4 is glued and screwed between the two pieces of ply on the straight side. Then smaller pieces are used to block the curved portion.

   Plywood well supported on edge like this is incredibly stiff, and you could add blocking, or additional layers to get the width and strength you need.

   K

   -

   -

   “The greatest achievement of the human spirit is to live up to one’s opportunities, and to make the most of one’s resources.” – Vauvenargues

5. 
   ken1putt | Dec 09, 2002 06:25pm | #5

   RE. Your e-mail,  You might be able do what you suggested if you get the layers of ply supported well enough. Plywood VERY stiff when standing on edge, but if it tips at all, the whole thing is going to come down.

   Because you are talking about pretty large stones, I think you really ought to hunt up some local stone masons and ask them about it. I'd hate to have an arch of that weight suspended overhead on an unreliable form.

   K

1. 
   ANDYSZ2 | Dec 10, 2002 02:30am | #7

   Don't put a large amount of stone up over the arch until the mortar is dry the mortar is where the strength to support the stone  comes from.Are you building a free standing arch or is it attached to a wall?If you are outlining  a front door entryway make sure your arch lines up symmetrically to the door opening  this can really sneak up and bite you.

                           ANDYSZ2I MAY DISAGREE WITH WHAT YOUR SAYING BUT I WILL DEFEND TO THE DEATH YOUR RIGHT TO SAY IT.

1. 
   joemorin | Dec 19, 2002 10:20pm | #8

   One putt, I am building a dry arch. It is basically free standing, as it is a arch over the entrance to a 100 year old root cellar. It will stand above and on the root cellar front walls which are dry e granite field stone. This might not work but "nothing venured, nothing gained".

   I now understand your form design, I think.So I will use plywood with 2x4's between them. The depth (width)of the arch is 24".

   It is going to be very hard to find stones in the mountains that have any kind of taper, so I'm wondering if i can put small stone shims between the vosiours (excuse spelling)to force the angle needed to keep them from falling.

   Joe Morin

   Lake George, CO

6. 
   andybuildz | Dec 10, 2002 12:43am | #6

   Joe

    I've made dozens. The best technique I came up with is to take your jig saw and cut the shape you want from the inside dimension on a sheet of 3/4" plywood. MAke it 3 1/2" wide or whatever will carry the top weight. Make two or three or more depending on how deep the wall is and how big the stones are. ( the 3/4" side faces up...duh) screw 2x4's  to the inside ot the plywood forms to keep em' together just short of the openings. This way you can even tool the cement with the forms up. Worked incredble for me.

   Bee thinking of sending this to the TIPS page in FHB

   Be a wall

         Namaste

                    Andy

   You don’t complete your inner work before you do your outer work. Nor do you say, "Well, the hell with the inner work: I’ll go do the outer work because it’s so important and pressing." That’s not conscious either. The conscious thing is the simultaneous doing of both. "Ram Dass"
   http://CLIFFORDRENOVATIONS.COM

1. 
   joemorin | Jan 16, 2003 09:12pm | #9

   Re: my stone arch.

   Ok did what you said. Ok so far.I have a 5foot widw, 2.5 feet high semicircle arch that is 20 inches deep. I'm doing this dry.And with field stones, Rocky Mountain granite.

   So my problem is finding stones with any kind of angle to build the pressure. I will need about 20 stones, about 6 inches thick,about 1 foot wide. SO I will need to chisel the faces to get a the 2 anglesie, say 5" at one end and 6" at the other.

   The granite isn't very friendly on splitting but I will try.

   Any suggestions?

   Joe Morin, Lake George, CO

1. 
   UncleDunc | Jan 16, 2003 11:48pm | #10

   You might find some useful information in this thread.

   http://forums.taunton.com/tp-breaktime/messages/?msg=22783.1