Bending Cedar for Arch

[Cooler]

When it comes to the narrow strips, I'll probably just plane them down.

I'll use more wood, but it ends up being a bit safer. I know my table saw will not cut higher than about 4". This frame is set to be 5 1/4" wide.

You can cut one side, flip it over and cut the other side, and then use a hand saw to part the narrow strip. That is actually a pretty safe operation.  Since you are only cutting a tiny strip in the middle it cuts very fast.  

A palm sander will quickly bring the narrow center strip down to level.  

Another option might be to use flexible molding.  Once painted it looks like regular wood:

https://www.amazon.com/Flexible-Moulding...B006R99T0U

[WilliamHodge]

When it comes to the narrow strips, I'll probably just plane them down.

I'll use more wood, but it ends up being a bit safer. I know my table saw will not cut higher than about 4". This frame is set to be 5 1/4" wide.

Use Cedar, it will be plenty strong enough. I band saw the laminations oversize, then plane them to thickness. 3/32" to 1/8" should work. Only the inner layer needs to be perfect. bury the lower quality laminations in the middle of the pile.They should be 3/4" wider than the finished lamination.

Make a form out of 3/4" CDX plywood sides and 2 x 4 stock cut with a square face. Make the form 20" longer on the radius than than the length of your finished lamination, and 1" wider. The bottom corners of the form should be rounded (coffee cup radius) to allow the truck straps to move around the form. The bottom of the form should be one solid 2 x 6 between the plywood, for strength. Cover the top with bending plywood, several layers. Add two reject cedar layers. This is where your finish inner radius should be.

Wax the form with paraffin.  Mix up a quart of slow set up glue, like Weldwood Plastic Resin glue (Amazon). Coat all glued faces. Pad the outside of the bundle with two layers of waxed bending plywood. Put the bundle on the form, and strap it with (2) 2" truck straps. Not 1", 2". make sure you don't spiral the lamination.

When the glue dries in 24 hours, undo the truck straps and gently pry the work piece out.  Joint one edge, plane the other on a thickness planer.

For a door jamb, I would make the head 1 3/8" thick to allow room to cut a 1/2" deep rabbet on the inside of the lamination. It's easier to cut a rabbet than it is to make a curved stop. Cut the rabbet on a shaper or router.

If this is your first lamination, don't be afraid to do a trial run on cheap 2 x 6 stock to learn how to do it.

[Azryael]

Great info!

A bandsaw is one piece of equipment missing from my workshop. I could make a fence that would allow me to safely cut down the middle; unfortunately space just doesn't allow for it at the moment.

I grew up working with wood, but never got really in-depth until my late teens (in my mid 20s now) and really find I enjoy it. My inner perfectionist is never satisfied with what I make, but I know I've a lot to learn and I'm realizing working with wood will never be "perfect", as it's living, breathing, just like me.

William, I'll give it a shot! I can't thank you enough for the pointers. I've really been struggling with how to best tackle this.

[RPE1]

Don't do what Jteneyck said or you'll be sorry.  You need to do just the opposite.  Don't bend it around something (Convex) but bend it into something (concave).  Unless you're able to accurately determine just how thick the final product will be and build the form to that size.  If you don't as you add layers the lamination will exceed the radius of the arch.
You probably already knew that, but I thought I'd better say something.
RP

[Azryael]

Good catch, yes, I figured that would be a concern as well.

It's rather unpleasant outside, and since most of my work involves me pulling my tools out of the garage to work in the driveway, I'm stuck inside!

[jteneyck]

Don't do what Jteneyck said or you'll be sorry.  You need to do just the opposite.  Don't bend it around something (Convex) but bend it into something (concave).  Unless you're able to accurately determine just how thick the final product will be and build the form to that size.  If you don't as you add layers the lamination will exceed the radius of the arch.
You probably already knew that, but I thought I'd better say something.
RP

I was just showing the concept, but that's a good catch. I made the arch jamb below with a concave form, as you recommended.  The OP is still going to have a hard time fitting a bent arch into that stone arch perfectly.  I'd make a template to make sure it's going to fit as well as possible.  I would still expect some masonary work will be needed to fill in the gaps between the wood and stone arches.  

And no, I didn't steam the laminations.  There's no need to.  Once you cut them thin enough they will bend into the form w/o breaking.  If you use Plastic Resin Glue to glue up those laminations the arch won't spring back either.  Lots of folks have good success with TB III, but I always get spring back with it.  
You don't want to cut the arch and side jamb at an angle.  You cut a rabbet in the side jamb, just like you would for a normal door jamb, and you cut the arch jamb to fit that rabbet.  Screw the two together in the normal manner.





John

[Azryael]

Excellent!

John, that arch I'm working with is nothing more than sheetrock over wood! No masonry work for me, at least not on this job!

I'm really looking forward to trying the lamination approach; I'm not sure why that concept just flew right over my head and I never considered it. I guess what they say is true, the complicated stuff comes easy, but the easy stuff you forget or fail to consider.

I've gotta admit, I've learned a lot by trial and error, but I always seem to learn more when I actually ask. I really can't thank you guys enough.

[Cooler]

I'm not sure you need such a wide piece.  Or even a bent piece at all.

You can run a narrow strip on  one side of the door and another on the other and spacers in between.

Or you can just use full width spacers and form a casing for both sides to cover them.

You can fabricate the casing from hardwood or you can use a paint grade flexible casing:

https://www.elitetrimworks.com/Flexible-Casings/


You can cover the spacers with bendable plywood:  http://www.rockler.com/1-4-neatform-bend...gLANfD_BwE

And you can cover the bendable plywood with cedar veneer:

https://www.amazon.com/s/?ie=UTF8&keywor...jyymrlt1_e

[brianwelch]

A lot of great information here. 

I bent cedar to a much tighter radius (very different application) by cutting thin strips, soaking in hot water and pre-bending prior to final glue up . After allowing the strips to dry, I used a thickened epoxy to laminate and plenty of wax paper on the table, forms and clamps to facilitate clean up.

[Azryael]

Well, I gave it a shot. All glued up and now to let it set for a while. Fingers crossed!

The laminating process was actually a lot of fun; I really enjoyed it.