Question
Does anyone have experience or an opinion on machining "Royal Wood" trim boards to make crown molding for an exterior application? I would be using their "1 x 6" stock. I am restoring a Victorian era curved wrap-around porch. To match the old crown molding profile, I need have this custom made. I am considering using Royal Wood because it is clear, readily available and it comes in 16 foot lengths.
Their website says this material can be machined, and that if the interior is exposed due to machining, that it will still be weather proof even if unpainted. But I will be painting the finished crown molding. However, my friend who will actually make the crown molding has never used Royal Wood before. Any input would be greatly appreciated.
Forum Responses
(Architectural Woodworking Forum)
From contributor B:
What you are talking about doing here is making your own flexible crown moulding. You could run into some problems other then those that might occur during the machining process.
I believe when you purchase ready made flex crown it is pre-twisted to make the upper and outer edge run the top outer radius while the lower inner edge runs the facia radius (outside curved descriptions - just the opposite for inside curves).
If you run your own crown I don't think you will be able to make the bend without the crown wanting to ride in flat up against your facia. This is because the bottom edge on an outside curve crown is running at a typically 3" to 4" smaller radius then the upper outer edge.
I'd suggest you take a piece of the un-profiled "Royal Wood" and seeing if it can be held up at the same angle as the crown and made to run the curve. Our business is curved mouldings and we make a lot of wood curved crown. I haven't worked with much flex crown over the years but do have a pretty good idea of how it gets applied.
I should post a separate question on how to best bend the crown around the curved edge of the roof. But for now, I simply need to know if the Royal Wood will work acceptably as a machineable substitute for real wood. Will we hit any surprises or have any regrets? I am just trying to make sure before I ruin about $160 worth of material.
As far as bending you'll just have to try a piece and see how badly it deforms. I doubt kerfing will help much in your application given the "lean out" of that size crown. You could try heat but it's a PITA. You could also try flexible polyurethane if you're so inclined.
Couldn't he also use a heat blanket to bend the crown? I'm pretty sure that would work very easily. If you get PVC too hot, it turns to cooked spaghetti, so you'd want to cook it just right.
Just heat up the moulding and push it to the shape you want its pretty easier. Why bother with everything else. Just get the job done with the right tools. I always go out and get the correct tools for the job. If I never use them again I just sell it off. Someone else is looking for the blankets and I bet you'd lose less on it than renting it. Most of the time I just include it in my bid and it's charged off to the job. By the way - my supplier has some Azek that was heated and then shaped into a pretzel. It can certainly make the 8' radius.
B) My friend has made some of the crown molding already, using a Bellsaw with a single blade. He reports that the Royal Wood shapes well, and is easier to cut than pine. He did note that it sands oddly compared to real wood, but is quite satisfactory.
C) As to making the 14 feet of curved crown molding, I had planned to follow the method described in Fine Homebuilding. But where wood was used, I planned to use a piece of Royal Wood. I had no idea that plastic wood could be bent with warming blankets. I'll have to think about this some more.
