Making molding for a half round window

[Wes Billups]

I'm in the process of replacing windows in my house. Two weekends ago I replaced a larger unit with a half round top. I now need to make the interior trim and get it installed this weekend. I've got multiple questions for those out there that have done this.

My plan is to do a segmented glue-up but I'm not sure what is best from a structural and cosmetic standpoint. Should I put a seam on the top center or would I be better spanning this with a board and place the seams at the 10:00 and 2:00 positions (see picture for example of what I'm asking)? I'm also wondering if there is a rule of thumb for how wide of boards I should use for the glue up as the old one I removed had split on both sides where there was cross grain as they had used some very wide boards to glue together the arch. I'm not against doing a glued up bent lamination but that seems like overkill for household trim.
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If anyone knows of an online calculator to use to calculate angles and lengths for gluing together an arch, please post a link as I've been unable to find one so far in my searches.

Just for information I will be using a William & Hussey molder to run the arch with a standard 2-1/4" width casing profile.
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Thanks in advance,
Wes Billups

[Mel Fulks]

If the finished product is going to be painted joint placement really doesn't matter. I like to glue up the pieces with pinch dogs on the back. News paper under it. Bandsaw finished glue up a little oversized. I do final trimming on shaper with a plywood template held with several nails.

[Keith Outten]

Wes,

I believe that there is a really good thread on this topic in our Archives. As I recall there were some very impressive pictures as well.

[Dave Zellers]

A classic biscuit jointer application if there ever was one. Plus, as you already noted, the more joints, the less cross grain.
Also, since you are using classic 2 1/2" colonial casing, I believe Andersen does this but I'm sure it's not cheap and you already have the means to cut it yourself. I think I would add at least one more joint and pick really nice straight grain to avoid tear out at the miters. This work is fun!

[Wes Billups]

Keith, I've searched and searched on this and can't find anything on the best from an aesthetic and structural standpoint. Can you give me a hint on what to search for? Most of my results pertain to gooseneck moldings for furniture.

[Neil Gaskin]

Wes. I'm assuming this will is stained. I would grain match as best as possible and worry less about where the splice is. For what it's worth I've done this and it isn't worth the hassle doing it yourself unless you just want to do it which I understand.


If if you do it yourself. I've done half lap joints about 4 in long and not had a problem. If you do not want to do it yourself I've usd Shawnee Millwork in Topeka. Good company. Alternatively, your window supplier probably has a contact.

[John R Green]

PM me
I'll send some pic' that will help

[Mel Fulks]

Biscuits help but are not absolutely neccesary. If someone else is installing ,instead of you...use biscuits. If you don't have a shaper to trim them as described earlier,just bandsaw them carefully on outside of the line. Then use a strip of 60 grit sandpaper (sometimes I use 40 grit) backed by a thin strip of wood to sand out bandsaw lines. P.S. I'm hoping they will be painted ,it's a small and pretty flat casing, without light color paint they will read as a flat board from accross the room.
Lots of variation on procedure ,mix and match at your discretion, you have a machine to run them . That is the big thing.

[Leo Graywacz]

Here's a thread that I put up a while ago

http://www.sawmillcreek.org/showthread.php?254119-Elliptical-Arch-for-an-Oak-Door

[Wayne Lomman]

Glue up a curved laminated top rail. Lamination thickness depends on what will bend around your radius. Glue it with resorcinol or epoxy. It will good enough to be structural for the building if required. Make a caul the shape you want. I have done this for curved trusses, curved stair stringers and rails as well as windows and doors. Griffith University in Queensland was a good example. No photos, sorry. It was another of those jobs with no cameras allowed. Cheers

[Wes Billups]

I ended up using splines to reinforce the corners and all went well. Amazing on how well the moulding process went. This was what had be most intimidated. I just attached the cutoffs from making the arch to guide the curved molding through the William & Hussey.

I now see why people with moulders speak so highly of them. These style of machines are truly amazing to watch what they can spit out.

I'll post pictures of the finished product once I'm done. I didn't take any during the build process as once I get working on something I completely forget to document the process along the way.

I will also say that the splines were a great addition as my daughter dropped the arch from about 7' up when I was making sure it'd fit the window. It bounced on the floor and none of the joints failed.

Overall it has taken me about 4 hours work and $20 in materials to build this arch. The quote from the local building supply store where I bought the windows was $300 for just the arch. Of course if you include the cost of the moulder, this arch was double what I could have bought it premade for.