Need to make some exterior arch moldings

[Zeke]

This is very similar to one of my next projects. I will be replacing some custom stucco moldings surrounding some wood arch windows.



We will buy some 1" thick foam and use a router on a trammel to shape the face profile. Then band saw the arch out of the blank. Since it's exterior, most of the foam core molding material seems suspect to me. I think I need a high density foam that I can expose the core to paint.

Any ideas what to ask for?

The detail shown here is pretty close except we are making complete half rounds.

[VINMAN]

Milt I've used stuff called resinmold or Flex mold or something like that. It is a flexible molding, that you can make curves with. It comes in all different profiles.

[Zeke]

I know about that stuff. Might be a possibility. But, I have to match 1930's original profile that exists on the verticals. We could do this in wood, but we would have to make sections due to wood grain. I'd rather make the whole thing at once if I'm going to set up the work. Fortunately, there is a way to slip the whole thing up into place or I wouldn't make a complete half circle.

[Zeke]

This piece of Trex Trim is close:



You can see it's simple. Just need to cut a key in the outside edge. But, this stuff doesn't bend.

[intakexhaust]

Milt-
Nu-wood makes all sorts of polyurethane trim including custom arches. They might need a sample of the original profile or perhaps find something close.

[intakexhaust]

Found there custom arch link: Nu-Wood – Architecturally correct windows, headers, gables, brackets, & more! - Nu-Wood™
Might be worthwhile to look at the ready made stock too.

Also, we did some fiber cement crown from James Hardie that had the plaster look. I'm curious if their expanding the line to other specialty trim although arches would be tricky.

[Zeke]

Thanks. I should mention that 2 of the arches have an inside radius of about 10". Pretty tight. That's why I thought I'd cut them out of flat blank stock For a larger arch there would be a tremendous amount of waste.

Also, I forgot to mention that I'm looking at all forms of composite. I even thought of using some Trex boards for this, but the core seems a little rough and I doubt I'b be able to put much of a smooth finish on it. Might as well do wood as I would not get much of an arch out of a Trex 2 x 8.

There is one larger arch about double the radius as well for a total of 3.

[Zeke]

Found Extira.

"What are Extira panels?
• A treated wood composite panel product for non-structural applications for exterior and high moisture interior environments.
• Available in square cut panel dimensions of 49"x 97", 49" x 194" and 25" x 194".
• Available in thicknesses of 1/2", 3/4", 5/8", 1" and 1 1/4" (+ /- 0.005").
• Sanded two sides (S2S) for a smooth, unprimed surface."

Extira Treated Exterior Panel Product Line

[imcarthur]

Originally Posted by Zeke

inside radius of about 10". Pretty tight. That's why I thought I'd cut them out of flat blank stock

There is your solution. That Extira looks promising. Albeit a different use, Focal use 6" high density particle board - like the Extrira but untreated - for sculpting curvy speaker baffles. Lacquer it & it can look awesome.

Ian

[dad911]

I've used Azek. PVC, comes in 1x & 4x8 sheets. Routes & cuts easier than wood, can glue with PVC glue.

[look 171]

Flextrim is your friend and its a paintable rubber / composite material. You aren't thinking about making the thing are you? Talking about working for free? As shaper is needed plus custom knife is necessary for the profile to match existing. Flextrim takes care of all that for you if you get them the radius or cure and the profile. That looks like a typ. profile and I am sure they have it in stock. That's a lot of fun making but you will spend some time doing it. We had to match a large cure baseboard for a job we did last year. I ended up getting the radius (12")turned on the lathe to match the profile then cut to fit. it was stain grade. I just didn't want to spend the time to cut it on my shaper. it would have taken me a whole day just for the setup. I have never been a big fan of the MDO type products although many freeway signs are made out of this stuff. If you decides to get shaper knifes, go to LRH in Chatsworth. I buy my knifes from them. They are not the China or Taiwan imports but quality knifes.

One more great thing about flextrim. It FLEXES and you can push and pull to fit the arch. You will be "Fooked" if it was made it out of wood if you are 1/2" off. This one isn't easy, and I hope you make a few bucks on it.

[look 171]

Originally Posted by dad911

I've used Azek. PVC, comes in 1x & 4x8 sheets. Routes & cuts easier than wood, can glue with PVC glue.

i don't think you can route that large profile even with the larger router bits. Now, you can reduce the rpm and chuck a 1/2" shaper shaft and insert shaper knifes for the large profile. YOu may be able to get away with it that way for a few pieces. don't expect the end result to be perfect because you can't cut the whole thing in one pass.

[look 171]

I just realized, that's your typ. brick molding?

[Zeke]

No, not the typical brick mold, however the overall size does compare. AFA the profile, I can run that groove with a core box bit.



A trammel set up on the flat sheet and that's easy. Band saw the shape out and sand the edges. I don't have a spindle sander, but this might be a good reason to buy one. Or use the drill press as I have for years with a drum attachment. This to sand the inside radius.

I think I have this covered, Jeff. Money? All T&M. That's only way I work. Nowadays, my T&M covers gas and drive time too. Don't want to pay? Go get it yourself.

[look 171]

Would you think after you cut it out on the band saw and run a straight cut bit to trim off the edge with a trammel to clean up instead of sanding would be a lot more accurate?

You know that Flextrim is only 200-270 bucks for the arch on that window. To buy that 1/2" core box bit and set up the trammel will cost you more then $200, would you think?

[Zeke]

I thought I might make a guide cut at the inside and outside radius. The thing is, where this is going against existing plaster (stucco), things aren't perfect. I might need to tweak it while on the ladder.

Don't want to makes things too perfect on a 1930's house. This isn't an arch in kitchen cabinets.

[dad911]

Originally Posted by Zeke

Thanks. I should mention that 2 of the arches have an inside radius of about 10". Pretty tight. .......

Originally Posted by look 171

Flextrim is your friend and its a paintable rubber / composite material. ........

Originally Posted by look 171

.....
You know that Flextrim is only 200-270 bucks for the arch on that window. To buy that 1/2" core box bit and set up the trammel will cost you more then $200, would you think?

Can bend the flextrim to a 10" radius? or will it need to be done with heat (My supplier does that)

Last time I did arch windows & casing, they still needed a radius of the circletop to get the trim close.

[look 171]

Originally Posted by dad911

Can bend the flextrim to a 10" radius? or will it need to be done with heat (My supplier does that)

Last time I did arch windows & casing, they still needed a radius of the circletop to get the trim close.

they make that stuff to whatever radius necessary (within reason of course) for you. Heat is good. I have used a heat gun a few times for some tough curves. for the most part, it has never given me any problems due to the small amount of flexibility that's associated with the material (a very, very good thing).

[look 171]

Originally Posted by Zeke

I thought I might make a guide cut at the inside and outside radius. The thing is, where this is going against existing plaster (stucco), things aren't perfect. I might need to tweak it while on the ladder.

Don't want to makes things too perfect on a 1930's house. This isn't an arch in kitchen cabinets.

You took the existing trim out and now you are trying to put a new one in its place, an arched piece?

I am not sure how that core box bit is going cut that profile? YOu will need to do a lot of trimming and shaving?