Getting a better mate between two surfaces?

[Prarie Bowyer]

So for me it's constaltly a saga.  One thing leads to another.  When I glue u pmy risers on my R/D bows I pre cut the parts on a band saw.  I used to hand sand the curve for the riser but now I use a hand held belt sander held in a vise.  I never needed a perfect fit curve because I 1) used a thin strip between the riser and 2) used the riser curve as the clamping and bending form so everything pulled down to it.  Mostly perfect seams on ALL previous bows in that reguard.

This latest one is killing me.  Error in judgement # 1.  I got a slightly wavy bandsaw cut on the thickness of the belly which I was afraid would significantly reduce draw weight.  Still I had it worked out.  I sent the belly through the lam grinder and flattened off a section that would work. 

turns out I'm still over target weight so I was fine in that reguard.  But when I glue up I wrap everything in shrink wrap EXCEPT the riser assembly where I use TB3.  I put two calmps on the fades to pull the bow lams down over the riser curve.  Then I wrap everything in bike tire tubes  and remove those clamps and into the oven it goes. 

This time I think when I removed the clamps one side relaxed just a bit.  Th glue line was on Walnut against Ipe so you'd think it would be fine.  AND I forgot my accent strip (maple).  BUT the issue was that when sanding the fades in that glue line was 1/8" of an obvious glue line.  Looked terrible imo.  So I sawed it apart and made anew riser.

I got it kinda close then started scraping and sanding to get the best fit I could.  It got pretty tight then pretty terrible.  It's alwayse "just a little bit more right there".  Back and forth for a few hours sanding and scraping to get a "perfect fit" which eludes me.  Then I figured I'd make the riser a tad deeper than the belly curve and pull it down to fit.  Dry fit clamp up I couldn't see light through the important section.  Glued the crap out of it and clamped the heck out of it.

I can't see throught  the TB3 squeze out but I suspect I may have the same issue again.

Is there some easy low tech way to mate two curved surfaces nicely over a long shallow curve?  What I did was constantly check for light coming through the seam and tried to minimize that by sanding and scraping.  I even used my daughters sidewalk chalk at one point to shade one side then press them togeather and sand the places where chalk transfered.

Is there some method I don't know of?  Or how about fixing the problem if it persists?  Ipe dust in Epoxy and dig out the TB3in that area?  Of course my bow blank is coming along perfectly... I just needed to re make the riser section.  This is definately one of those things that is easier to make a new than fix I think.  but I can't now.  I've got to use this blank.

[mikekeswick]

Google pattern sander

[dmikeyj]

It always helps me to get one surface the way I want it, then use it as a sanding block against the mating piece.  You can do this with both surfaces, after a few good sandings with 60 grit both ways, you should have perfectly mated pieces.
I'm not sure if this description is good enough to get across what I mean.  If it is a curve that you will make many of, a circle sanding jig on a drum sander would help to get the one side perfect first.

Hope this helps,
Mike

[bubby]

the most important thing to do is slow down,take the time to make shure it all fits well and you will make less errors, it's alot faster to do it once right than 2,3, or 4 times real fast, Bub

[dragonman]

sanding always rounds off the surfaces so there is a bigger gap at the edges than in the middle of the 2 surfaces. The old english cabinet makers often used a slightly curved blade to scrape out the mating surfaces so their was no lump in the middle of the joint preventing the edges meeting perfectly... hope that makes sense, but it makes for perfect glue lines if you can follow it.??