A new guy needs help:
Gentlemen,
I’ve been a hobbyist at woodworking for over 5 years. I’ve built several large frames and interior doors for a local stain glass artist. He has been commissioned to make 5 large stained glass windows for a church here in chicago, which will replace the originals that were sold many years ago. He has asked me (and I accepted) to make the frames. The frames and stained glass are replicas of 5 existing windows on the north side of the building. Ours will be installed on the east side of the church which receives full unobstructed light.
Each frame will be 37 ½” wide by 12’ 3 ½” long. The top is capped with a semi-circle with a radius of 18 ¾“. I got my dimensions from measuring the existing opening of one of the 5 windows we are working on. The stiles, including the semi-circle are 2” wide by 1 ½” thick. Lastly, the bottom rail will be 3” W x 1 ½ “ T. These dimensions come from measuring the ones on the north side.
I’ve already made a test frame from some 2”x6”s to ensure my measurements were correct, and more importantly, to practice making the semi-circle. With a little shaving here and there, the test frame (in three 4’ long sections) went in easily. The final frames will need to be delivered to the artist in two 6’ long pieces. Ouch!!
With that said, I have two questions:
1. Wood Selection: Since the frames will be painted on the exterior side and stained on the inside to match the existing casing which I think is some old growth pine, I advised the church board to go with white oak instead of mahogany. Is there a better wood of choice for this type of project? Maple, Red Oak,
2. Making the semi-circle: I followed the process used by David Bedrosian in the mar/apr issue of Fine Woodworking to make my test semi-circle. The processed worked well, but when I accidentally hit it against a post in the basement, it broke at the glue joint! Basic yellow glue was used on the test frame and I’m sure it broke because the joint was starved of glue. We anticipate the stained glass to weigh about 150 lbs when completed, so I’m a little concerned.
Should I look at other options to support the heavy weight of the stained glass such as; bent laminations (which I have never done) or gluing up 3 layers of ½” material alternating the joints (then cutting the semi-circles).
I’m sure I’ve overlooked something, so I would really appreciate any comments.
Replies
White oak works very well for bent laminations. The process is not difficult and the resultant arch will be very strong. Your 'lams' should be right around 3/32" to 1/8" thick and can be easily cut on the BS. The thickness will depend on what you can bend around your form.
Joint the "parent" board; cut the lam;
Re-joint the board for a fresh edge; cut the next lam; NUMBER the lams in sequence.
Repeat jointing the parent board and cutting a lam.
When all lams are cut, stack them on edge to resemble the parent board and mark one edge with a large "V" - the numbers you used previously will be gone after the next step.
Thickness plane the rough edge of the lams.
Lay the lams, all except the last one, a flat surface and tape down all edges. Spread glue evenly, Titebond III or slow-set epoxy, with a 3/32' notched spreader; Stand them up together and add the last one. Make sure the "V" is in correct alignment.
As this is a semi-circle, you can start clamping from the center out to the ends, alternating right and left end clamps.
Apply a few clamps to blocks so that the 'stack' does not slip out of line.
Done! Congratulations on a good job.
P,S, There will NOT be any springback.
Frosty
"I sometimes think we consider the good fortune of the early bird and overlook the bad fortune of the early worm." FDR - 1922
Edited 9/5/2007 10:46 am ET by Jfrostjr
Stanford thanks for the question,
I plan to use mortise and tenon joints to connect the sides of the frame to the bottom rail. (the bottom rail will have the tenon). The semi-circle will be connected to the sides with a loose tenon, and I will probably pin them. I will also use the loose tenon (pinned) to connect the two 6' sections.
bd
I think the bent lams would be a huge mistake. Even with the best glues etc. The windows will go through different seasons and the lams will spring back. It might only be a little but they will spring. I think you would be better off using a brick laying technique. This will solve all of your problems. You can put the exterior wood on the outside and your interior wood on the inside. I would also suggest using Mahogany on the exterior. Both woods hold up to the weather equally as well. But with the oak you will have to fill the grain so the paint looks decent. Mahogany takes paint pretty good with little prep. How did they make the windows that are currently in the church? it would probably be best to copy the method and materials they use originally since they are still there, xso they must be holding up.
What about kiln dried cypress? The grain is similar to pine and it can't be beat for outdoor durability. It should take paint very well and wont need filler and should not cost as much as the mahogany.
I'm assuming the joint that broke was a mortise and tenon.Draw peg the tenon, the glue joint will not break.As a matter of fact ,you need not use glue at all. After fitting the joint, bore the mortise straight thru without the tenon in place. Remove the brad pint bit from the drill, fit the tenon in the mortise and insert the brad point drill. Push in to mark the tenon. Remove from mortise. The point that is left is moved 1/32" ,1/16" at the very most closer to the shoulder.Bore this offset hole.Put a point on the dowel, I use a pencil sharpener on smaller pegs. Install the tenon and drive the peg til the peg goes thru the other side. Cut peg off flush each side.The stained side can be left 1/8" high and slightly beveled if you like. If you do not wish to have the peg show thru on the stained side,then the bore stops 3/8" short and the peg point less pronounced.I prefer the peg to go thru if possible.The peg protruding can be round , square etc. Just use square stock and whittle a peg to round.
The tenon will not pull out.What happens is the peg bends a bit in the hole as it is driven. The peg pulls the tenon tight to the shoulder of the mortise.You can glue if you like, a drop on the peg is a good idea too. I cut the pegs off with a small flush cutting saw ,then sand to flush.Practice on a piece of scrap, if you offset in the wrong direction you will open the joint instead of pulling tight.
White oak, is a good choice.
mike
Yes I realized they will be tennoned in, or, by using bricklay there would be no need to tennon, the entire unit would essentially become one piece of wood.
Also in the time it takes to make the form and gule up each piece etc. let it dry in the form. It would take about 1 day for each part. Using bricklay he could do 1 unit in about 1 day.
Also unless he has a vacum bag or has alot of clamps and does alot of planning I would be worried about making sure there would be enough pressure to ensure consistancy of the bond and arc.
Also he would need to spend a day resawing all the laminations, then he has to hope his planer can handle thin wood. or he needs a drum sander.
Whereas with bricklay he can rough bandsaw the pieces, glue and clamp and use a router and template to clean up. And there are simple ways to even speed up that process.
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