Curved accent stripes in riser

[kenboonejr]

OK so I am now thinking about bow #2.  On the first bow I just did straight accent stripes.  What is the key to doing curved accent stripes. I mean like I know that say if I was going to do just one stripe for simplicity sake I would take my block of riser wood and cut a curve in to it and then sand it up and put say a strip of hardwood or phenolic in there and glue it all up.  But I am thinking a few things like..

#1 How do you cut a nice steady curve for starters? 

Then #2, I would think you have to sand both pieces before gluing an accent stripe in and how do you ensure it's a tight fit? 

Then finally #3 if you are doing another curve, would you cut out the first curve, put your accent stripe in place and then glue it all back, drop it in the heat box, and once that has cured then cut your next curve and add the next accent stripe and then throw that back in the heat box again?  and if so is there any effect of having the first part go into the heat box a second time?

Just saying.. I'm thinking on my next one I would like to try a curved striped but not exactly sure how to go about doing it.

Thanks!

[Mad Max]

You can do them with a spindle sander, But you can sand forever and still have gaps.
You need a pattern sander with a bearing or rub collar.
Mine is a rub collar (at the bottom) flush with the sanding belt.

 
Some 3/4" plywood
You can use a router and a router attachment to make circles for a simple radius
Let's say a 12" Outside Radius on 1 piece of plywood and a 12-1/8" insider radius on a 2nd piece of plywood for a 1/8" stripe.
Double side tape both pieces of the riser block to the patterns and pattern sand them.

Yes you would do 1 curve and glueup then the second curve and glueup.

For something like this you need someone with a CNC to make your patterns.


Here are a pair to make 2 different curves for a 1/8" stripe

[Crooked Stic]

Like Max said a pattern sander with jigs is best. If ya do it free hand then use long gradual curves.

[Mad Max]

You can use a Robo-Sander Flush Trim Sander
 and get plenty of 60 grit sanding sleeves
Make sure and get the BIG one

https://www.stewmac.com/luthier-tools-and-supplies/tools-by-job/tools-for-sanding/robo-sander-flush-trim-sander/

[Shredd]

   If you want a simple curve just make a radius jig for your bandsaw...  As long as you don't go thicker than about 3/8" with parallel lam accents one simple cut will work... Any thicker with accents you may have to change the radius on one of the riser pcs...

   For the crescent accent just run the curved wedge through the saw with the same radius jig...

  You need a fairly smooth cutting blade...  After you make your curved cuts just run them over your sander with a very consistent and light touch...  Use the saw marks as your guide...  If your sanding is not consistent the saw marks will let you know... Don't sand smooth... Just leave enough saw marks on that shows that you sanded consistent... You are never gonna see .001 to .003" deep saw marks from the edge...  Sand with the cut you made don't try to true it up to 90*...  If you do you are looking for trouble and you will probably get gaps...

  If you decide to go with fatter accent, lets say 1"... You will have to cut the radius of one of the riser pcs 1" smaller or larger radius than the other pc. so they fit together properly...

[kenboonejr]

Ok cool.  I was thinking kind of along those lines but just wasn't sure.  I like the idea of having a pattern sander to get it right each time.  So I guess with a pattern sander, the challenge is just getting the pattern right so you only have to tackle it once.  And I guess once you have a pattern for the size of the curve you want, you could always change the orientation of the curve depending on how you want it to run so that makes sense to me.

@Mad Max - that looks good but don't think I am going to try and tackle anything that I need to have cut on a CNC at this point.  I like the way it looks like you have two patterns wrapped up in just those 2 pieces.  That was some pretty good thinking there!

@Shredd - Yea I was wondering if you just did 1 cut if that would work or not and I guess that depends really on the shape of the curve.  I suppose that works if doing a consistent arc, but if your curve changes like starts to curve in more near the bottom kind of thing, you would definitely have to have another pattern.

Thanks guys!

[Shredd]

  Each accent only takes one cut on the riser... (unless you go over 3/8 to 1/2" thick with your accent) The crescent wedge itself takes two cuts... Both cuts are the same radius as the radius cut on the riser...

  I done at least 40 bows this way using this method...  You need a smooth cutting saw blade though and a light consistent touch while sanding... I only use a pattern sander for the back side of one of my risers to fit my form... It's not a radius on that riser...

   You can even make sanding blocks the same radius as the cut on the riser and sand by hand...   

[kenboonejr]

That's cool.  I think I am going to try it on my next bow! 
Thank you guys!

[oldandslow]

That's cool.  I think I am going to try it on my next bow! 
Thank you guys!

Google woodslicer bandsaw blade...cuts so very nice.

[Mad Max]

Google woodslicer bandsaw blade...cuts so very nice.
[/quote]


That's all I use

[kenboonejr]

So i googled it and it says it is a resaw blade.  Can you use that for the curves as well?  1/2" blade?
Thanks,

[oldandslow]

So i googled it and it says it is a resaw blade.  Can you use that for the curves as well?  1/2" blade?
Thanks,

Absolutely...wide curves cut nicely. Using a jig will require little sanding

[kenboonejr]

Well thanks guys I have been needing a new blade anyway and I really want to try a curved accent stripe on the next riser.

[Walt Francis]

You can use a Robo-Sander Flush Trim Sander
 and get plenty of 60 grit sanding sleeves
Make sure and get the BIG one

https://www.stewmac.com/luthier-tools-and-supplies/tools-by-job/tools-for-sanding/robo-sander-flush-trim-sander/

They make 60 grit metal sanding sleeve for the Robo-Sander that cleans up fairly well with a sanding belt eraser/cleaner.  The one I bought 8-10 years ago still works fine after a few dozen bows.  Some of my risers have a few curves, below is the bow I built for last years Tradgang bow trade:

[kenboonejr]

That's a nice looking bow Walt!

[4 point]

That is a nice bow Walt, shoots good too!