1 pc riser- fitting to form???

[md126]

Hello all,  what is the best way to shape your 1pc risers so they fit the form perfectly w/ no gaps, alignment issues, etc??

i've been cutting out the riser (just outside the line) from a template traced from the form and then sanding down to the line. I've had a terrible time getting it just right though to where they fit with no gaps. i've been marking the high spots and then sand them down and then other gaps show up. i don't over sand and check frequently for fit but still can't get it just right.

thanks in advance for any assistance

Mike

[macbow]

If your going to make many of the same style it might be worth your time to make one that is perfect then use it as a template.
The template is used with a drum sander on a drill press .
The sander drum has a built in stop for the template.

[Buemaker]

An other thing to consider is that even if you get your riser to fit your form perfectly it may not fit so perfect  when the laminates are placed on your form. This should also be taken into consideration. Bue--.

[kennym]

Yep, what they said!

You might clamp a fake riser (cut within 1/8" or so)down on the lams and glass that go under it  and scribe a line to grind to. When you get it to fit the way you want, keep it for a pattern or make a jig like macbow described.

This kind of stuff can drive you nuts, but worth the trouble when you get the way you want!

Good luck!!

[Gundog68]

I put all the lams under the riser in the form with some tape. Then clamp the riser "behind" the form. So i can fine adjust the position of the riser. After all is ok, i draw a line on the riser with holding the pen flat on the lams, perpendicular to the lam-direction. This works fine also to create a template. I do not much bows and always the lam stack is not the same, so this works fine for me.

[md126]

Thanks for the replies!      

what do you grind the riser down with? drum sander, spindle sander, by hand....??

thanks!

[kennym]

Disc sander on the bow back, and a spindle on the belly curves.

[md126]

thanks fellas!!

[northstar]

I also get and chase gaps. Once I get the gap down pretty good I put masking tape on the lower form under the gap (sometimes two or three layers) to force the glass up a little tighter in that area.
Once glued up and finished I can not see or feel any  problems. And no voids in the glue. 12 bows so far and they are all shooting.. Jeff

[Crooked Stic]

I have never really had a big problem as long as you take your time and get the riser to fit the form perfectly.Then make a sanding jig off the perfect fit. One way to do this is get some sticky back sandpaper-40 grit- and stick it to the form in the riser area get your riser real close to right then scrub it back and forth in the form with the paper in place. Boring and takes time but will work.
Back to the jig. you will need some type of profile sander. I have found the robos to be junk. I build a lot of bows and have converted my 6x80 to a profile sander. Once you get the jig made by trail and error fitting the next ones are  pretty easy.
Another thing some guys do is a hard rubber strip next to the form for a bit of give when clamped or air hosed.
 
 

[kennym]

Hey Mike, where did ya get the drum for the sander with the lip on it?

Brought another thread up to top with a cool way to make a template!

[Buemaker]

Your sander looks like a good setup. The template bearing is it fixed permanently in place or is it a ballbearing wheel of some kind that is rolling? Bue--.

[Crooked Stic]

I had all the stuff made at a machine shop. The drive drum has to be machined flat except for an inch on each end for tracking. The guide wheel has a lock collar bearing and a press fit in the wheel. The table is machined flat and mounted with three motor end cover screws. The cost of this about 4 years back was $350. Brandon of Rose Oak bows posted his setup quite awhile back and I copied it.
 
 
 

I had to use shim stock to square the table to the drum.

[Crooked Stic]

I forgot to say the guide wheel needs to be about the same diameter as the drum with your prefered grit of belt. I use 60 grit.

[rmorris]

That is the cooled thing ever! thanks for sharing.