I'm stumped - how do I figure out this angle?

[rnt80]

I'm wrapping this project up and I'm at a loss with the crown.  It's a paint grade job so the crown is a flex material.  I don't know how to get the angle on the outside corners of the middle section.  The issue that's throwing me for a loop is the fact that the crown doesn't flatten out at the corner, there's still a gentle curve.  The spring angle is 45 degrees so I've set the bevel on my ts55 at 30 degrees, however, I can't figure out the miter angle.

 

[Brice Burrell]

This problem has stumped many a carpenter/woodworker over the years so you're not alone.  I've good news and bad news (and more bad news).  First the first bad news, it can't be done with your molding.  The good news is some clever carpenters has figured out a solution, you have to fake it.  The problem is the profiles will not line up no matter how you cut them so you need a custom profile for the middle section.  You need to make a profile that mimics the original but allows the two different to trick the eye into believing they are the same.  Now for the rest of the bad news, with your curved piece that is going to be very, very difficult to do.   

 

[erock]

I think the miter angle is 35.3 
45/45 spring angle ----miter angle is 35.3 and bevel angle is 30

 

[rnt80]

I think the miter angle is 35.3 
45/45 spring angle ----miter angle is 35.3 and bevel angle is 30

Unfortunately, I'm inclined to go with what Brice has stated.  I don't have a straight line on the crown to reference the crown off of since it has that curve.

 

[erock]

sorry....I thoght it was a 90 degree corner angle you where looking for....ooops!

I just noticed the attachment and looked at the photo.....I feel silly now!

 

[rnt80]

This problem has stumped many a carpenter/woodworker over the years so you're not alone.  I've good news and bad news (and more bad news).  First the first bad news, it can't be done with your molding.  The good news is some clever carpenters has figured out a solution, you have to fake it.  The problem is the profiles will not line up no matter how you cut them so you need a custom profile for the middle section.  You need to make a profile that mimics the original but allows the two different to trick the eye into believing they are the same.  Now for the rest of the bad news, with your curved piece that is going to be very, very difficult to do.     

Wait...where's the good news? [unsure]
I'm not sure I can make a new profile.  What I do have going for me is that this piece has a painted finish so that will give me some latitude in covering up mistakes....three cheers for Bondo!!
I should've known better than to draw it up this way.  Had I designed this so that the crown flattened out before it got to the corner I wouldn't have this issue.

 

[rnt80]

sorry....I thoght it was a 90 degree corner angle you where looking for....ooops!

Erock, no sweat.  The crown is on an 90 degree outside corner but since the top and bottom of the crown are curved I don't have a straight reference point. 

 

[Brice Burrell]

Wait...where's the good news? [unsure] ....

Well, there really isn't much, other than it is possible (technically speaking of course).  

....What I do have going for me is that this piece has a painted finish so that will give me some latitude in covering up mistakes....three cheers for Bondo!!.....

 

You buy Bondo by the gallon right? [blink]

.....I should've known better than to draw it up this way.  Had I designed this so that the crown flattened out before it got to the corner I wouldn't have this issue.

You know what they say about hindsight......

 

[Ken Nagrod]

Russell, why wouldn't you want the ends of the crown in the center section to level out?  Is the flex crown's curve you came up with too big that it's not allowing you to do it?  I think re-shaping the curve would be your easiest solution.

 

[rnt80]

Russell, why wouldn't you want the ends of the crown in the center section to level out?  Is the flex crown's curve you came up with too big that it's not allowing you to do it?  I think re-shaping the curve would be your easiest solution.

Ken, the curve is pretty sizeable.  The crown is a 7 1/2" stretched King George, so it's fairly tall.  While it is a "flex" material the crown has been pre-shaped/moulded according to the template I sent the manufacturer.  There's really no "flex" in the material in the direction I would need it to go.  I think at this point my best option, since the case work has the finish already applied, is to make a mock up of the upper part of the middle case.  I can then cut those outside corners as close to the angle as I can get them, cut the two short return pieces, and assemble that section of crown.  I'll then sand/bondo/sand or whatever combination I need to get the two profiles to match up as best as I can.  I'll finish the piece and then have it ready to attach to the case. 

 

[ccmviking]

If the molding still had some flex in it I would try something like this.  Problem is if it's curved is how to set it up properly for a cut.   Since It's paint grade you have a little room to play with it.  If you have enough straight molding, turn the coner while beveling the cut to start and turn the molding upwards.  It might take a couple of blocks with angled cuts to get a smooth transition so you can get a good round out of it rather than it being choppy.  Depending on if you look at those as cuts or blocks they can seem backwards but you should get the idea.

 

[tiralie]

Russell:
This is a perfect excuse to buy some profiled hand planes and try to match the curved arch profile.
It'll be some work and steep learning curve but I am told that guys used to do it this way before the advent of shapers and moulders.
Clark and Williams (http://www.planemaker.com/index.html) now called "Old Street" have some great DVD's to help you along.
It would be a shame to add a bunch of bondo filler to what appears to be shaping up into a very nice piece of furniture.
Tim

 

[Sparktrician]

I'm wrapping this project up and I'm at a loss with the crown.  It's a paint grade job so the crown is a flex material.  I don't know how to get the angle on the outside corners of the middle section.  The issue that's throwing me for a loop is the fact that the crown doesn't flatten out at the corner, there's still a gentle curve.  The spring angle is 45 degrees so I've set the bevel on my ts55 at 30 degrees, however, I can't figure out the miter angle.

 

I did a chart a few years ago for some of my installers facing the same issue.  The most common spring angles are in bold.  Hope it's useful.  

 Crown Moulding Cut Angles
Spring Angle Miter       Bevel
    30                 27           38
    35                 30.5        35
    38                 31.5        34
    40                 33           33
    45                 35           30
    52                 38           26

[smile]

 

[tiralie]

Russell:
Here is a great article from this is Carpentry addressing the problem you are having.
http://www.thisiscarpentry.com/2010/09/10/raked-baseboard-returns/
Hope this helps, a bit too late I know, but hey for next time.
Tim

 

[Brice Burrell]

Russell:
Here is a great article from this is Carpentry addressing the problem you are having.
http://www.thisiscarpentry.com/2010/09/10/raked-baseboard-returns/
Hope this helps, a bit too late I know, but hey for next time.
Tim

Thanks Tim, that's exactly the article I was trying to find for Russell last night. [thumbs up]

 

[tiralie]

I was curious if I modeled this in Sketchup, whether I would experience the same problem.
Here are the results.
[attachimg=#]
While Sketchup will force a match, the crown distorts in an unnatural way if you use the follow me tool.
[attachimg=#]
Drawing the crown in two pieces like you would when you cut it shows how the horizontal and curved crowns don't match at the corners.

Below is a (rough) drawing with the corrected crown.
[attachimg=#]

 

[Brice Burrell]

This helps visualize the issue, nice work Tim.

 

[rnt80]

Wow, Tim thanks for putting in so much work.  You'll be happy to hear that I solved the problem......redesign and get new crown.  Just in material costs these was a $150 mistake.  I probably spent a couple of hours in the shop trying to make it work.  I'm going to redraw the crown so that it flattens out at the corners and that should solve the problem.  Thanks to all for the time and effort you put forth trying to help me figure this out.

 

[Ken Nagrod]

Just curious Russell, but could you have heated up the existing piece of crown to change the overall shape?  Then repaint from any damage as a result.

 

[rnt80]

Just curious Russell, but could you have heated up the existing piece of crown to change the overall shape?  Then repaint from any damage as a result.

No.  The flex crown is formed into the required shape.  There's obviously a lot more give compared to wood but you can't reshape or manipulate the piece.