Curving pine boards via saw kerf method

[cag]

I need to extend the jambs of a complete semi-circular window.

I'll be using 3/4" THK x 2" W clear pine.
The internal radius I need to meet is 43-3/4" already taking into account the reveal.
I'd very much like to have 3/8" of "meat" left in the extension jamb strips left standing.

The initial question becomes, whether it is feasible enough of a notion and realistic; given the species, internal radius, thickness and width to accomplish this task?

Thinking positively...how often would I need to place the portable power saw kerfs to accomplish this? I'll not be rendered with a segmented rendering after all this! I won't have it! I want smooth...

Seriously, I know there's alotta' ****** **** involved in a question like this! Mainly with the clear pine I suspect.

I'm going to experiment beforehand ok so I'll get there eventually. But, I'm indeed interested in the learning of others having past been beckoned in similar pursuits.

What's the consensus here if you please.

 

[juddspaintballs]

I would think MDF would be easier to bend like that, especially if you added a little steam as you went.

 

[Dumber than lumber]

Steam bending is probably the way for you to go on this. You could do it with the kerfing, but you will probably have a few mishaps along the way (i.e., busted boards, etc.). Steam bending (note that I have not done this myself) would be how I would go at this.
Another possibility is to laminate it up with very thin boards.
Please post pictures of the existing window.

 

[cag]

I've no experience w/ medium dense fiberboard. Are you suggesting saw kerf still or strictly steam?

 

[cag]

This is a fairly large radius.

 

[dogdog]

Maybe look up steam bending... as suggested...


saw it some where when I wanted to remake my front door that had an arch... but never got to it... and problem solved with putty.

I think few here have done it, saw a few post way way back that they used a large pipe and a steamer... well a pot of water with a hose piped into the large pipe that houses the wood piece...

Maybe do it in layers ? and glue it back like 1/8 layer? 1/4 layer ? bend glue , clamp in the mold you cut out ?

 

[The Cobbler]

I would try to resaw the board to 1/4" or 5/16" to make it more flexible, the problem with saw kerfs is you wont get a smooth bend

 

[The Cobbler]

if it doesn't want to bend in place without feeling like it's going to break, bend it over several days by wedging it up more each day

 

[Skiff Builder]

This is a fairly large radius.

Cag,
Here is another way. Draw your radius on a pc of plywood. Glue up some 5/4 x 6" pine segments with ends cut to 22.5 degrees to make a half octagon that would fit your 43.75 radius. Trace your window jam on and cut it out. You would need 2 layers thick to get your 2" jam extension.
Solid, no saw kerfs, no snapping trying to bend.
Skiff

 

[PugetDude]

Laminate 3-4 layers of 1/4" thick pine together. You'll end up with a seamless face grain, solid edge grain without voids and a smooth radius. Very easy to do with a MDF form, wood glue, and clamps.

 

[shedfullatools]

Rip a sheet of 1/4" Luan into strips the width you need and laminate them together in place.

 

[Kaizen]

For ease and results make a laminate. As said use a full pattern on mdf with ability to clamp. Have seen packing tape use to clamp. Very easy to make something that big. Little sanding off of the glue and you are installing.


Sent from my iPhone using Tapatalk

 

[southalabama]

Skiff builder has it nailed.

Sometime back I saw Norm do the same thing. It was likely on New Yankee Workshop but possibly TOH.

 

[joe49]

One more laminate vote.

 

[PugetDude]

You can also use wedges if you don't have enough clamps. Just screw a block to the form and drive in a wedge wherever you need to apply pressure.

 

[Miss the Pontiacs]

I laminated some oak moulding to do an arched doorway. The only difference is when you run your finger the semicircular material is smoother to the touch. Due to sanding of the slightly mismatched material.

 

[readhead]

Is the radius actually 21 7/8” or is this really almost eight feet wide? Either way building a buck to laminate 1/8” strips, 1/4” if it is really that wide, would probably be the easiest way to accomplish this.

 

[PugetDude]

If you build a full-size buck, make sure to allow a bit of overhang on the ends of the arch so you can trim it to fit.
Also, if you make the buck with clamping holes every 6" inches it will be easy to clamp up the laminations. A strap clamp works well for initial clamping.
Post pics of whatever method you end up using.

 

[JonBoehman]

I have done a similar sized Arched frame and Kaizan and PugetDude are one the same track as I used. I made a shaping buck to clamp to and did it in lamenations. It took over a week for me to do but it worked.

 

[Skiff Builder]

Why go through the time to build a bending jig guys? This is a jamb extension that will most likely be covered up with trim.
Layout flat pieces, cut the arc. They can then be glued and fastened right onto the window jamb cag is trying to extend. This way you are also fastening through the face grain.
Laminating has its place, but requires more material time and glue.
Skiff

 

[tymbo]

I would cut kerfs 3/8" deep and 1 1/2" apart. If it is still too hard to bend( or shows flat spots), come back and cut more kerfs half way in between the original ones.

 

[Skiff Builder]

Pic for concept only. Disregard dimensions.

 

[bullnerd]

I'm in the bendy plywood boat.

Especially if its getting painted.

If its getting stained, hmmm, 3/8 plywood reveal might not look too good with stain on it.

Probably best to test the pine. I don't think leaving 3/8" is going to bend too easily without steaming.

A lot of variables we don't know.

Is it 10' up in the air or eye level?

Details man! lol!

 

[AZ Pete]

Skiff Builder is correct. The method he recommends is the easiest of those suggested. I have used it with great results in furniture making and would not waste my effort and time making a buck, laminating and gluing up an arch.

 

[2oolhound]

I made similar using a curved tree. Trees growing along side creeks, rivers or on steep ground often have to reach out horizontally for light, then grow upwards creating great natural curves (with grain). I live near the ocean where these wash up on shore. This one is cedar.

Rough length was about 8' but finished length was 5.5'. I used a chainsaw to hack it out (not the little electric in photo)

Final sizing was with a belt sander.

The 2nd one was too short so I had to laminate 6" worth of boards on the ends (glued, screwed and tatooed).

 

[acer66]

wiggle board?

 

[PugetDude]

Skiff Builder is correct. The method he recommends is the easiest of those suggested. I have used it with great results in furniture making and would not waste my effort and time making a buck, laminating and gluing up an arch.

Skiff Builder's method works great for the flat trim, the OP needs to build a jamb extension. I agree it could build it in place, using backing blocks to space the laminations away from the rough opening. 2" brad nails in lieu of clamps.

 

[cag]

UPDATE: We decided to use 3/4" thick vinyl material and simply cut it to length of half the circumference. Then we cut and fastened a piece of strapping the length of diameter plus 1.5" to serve as a spreader forming the arc. We were then able to place it as a unit up against the inside flange of the window unit tweaking and fastening it in place exactly as we wanted it. This worked very well. The screws will be buried underneath the casing and the whole thing will be painted.

Thank you all for the input. It was good to read all the suggestions from you fellas.

Be well and enjoy your holidays.

 

[Dumber than lumber]

Why go through the time to build a bending jig guys? This is a jamb extension that will most likely be covered up with trim.
Layout flat pieces, cut the arc. They can then be glued and fastened right onto the window jamb cag is trying to extend. This way you are also fastening through the face grain.
Laminating has its place, but requires more material time and glue.
Skiff

You are asking what seems like a silly question.
But it is a free country.
And this is Garage Journal.
Maybe you didn't read the earliest posts?

 

[Skiff Builder]

"You are asking what seems like a silly question.
But it is a free country.
And this is Garage Journal.
Maybe you didn't read the earliest posts?"

The thread discussed using kerf'd than bent, laminated, and segmented arc methods as possible ways of building a jamb extension for a window.

What's so silly about someone not agreeing with you on building a laminating jig or steaming on this particular task ?.

Many ways to skin this cat- depends on how a person likes to work it. I think cag came up with the best way! Nice job cag.

Your comment above is a condescending put down of another persons suggestion/question/enthusiasm.

 

[bullnerd]

Doh! Good call, I forgot about that flexi-flyer plastic ****!