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How do you radius your sides?
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=28285		 Page 1 of 1
Author:  Dan Roach [ Tue Jul 20, 2010 9:17 am ]
Post subject:  Re: How do you radius your sides?
I use a dish to sand the radius into the rim. The pipe is attached to a piece of MDF and there are holes drilled through the mold into the piece of MDF so I can use dowels to line things up and hold the mold in place.
Author:  WaddyThomson [ Tue Jul 20, 2010 9:28 am ]
Post subject:  Re: How do you radius your sides?
I use a 24" stick of 2x4 with a 25' radius cut in one edge. Sand in all directions with 80 grit sticky paper. Radiuses the sides, the braces, the Spanish foot and the tail block.
Author:  ChuckB [ Tue Jul 20, 2010 10:07 am ]
Post subject:  Re: How do you radius your sides?
For steel string, I glue the sides to the neck and tail block before tapering the back with the sides about 1/4" taller than finish height. The sides are glued 1/4" proud of the neck and tail block. This allows for the extra height needed in the waist area when radiused in the dish for the top.

I usually taper the back 3/4" (already planned for in the different size of the head and tail block) by laying the glued up rims in the dish with a 3/4" shim under the tail block and whatever is neccesary on the sides to keep the rim even on the sides. Then I transfer the contour of the dish up onto the sides with a small 3/4" block of wood and pencil. Then I simply hand plane the back to just shy of the line. Then I take it to my motorized dish and clean it up. (I'll post a pic if needed).

Now that the shape of the dome is on the back, it will lay nicely in the dish for hand planing the line of the top that you will transfer from the top dish, like the back was transfered, minus the shim and with a 1/4" small block to transfer.

Hope that is not too confusing.

Chuck
Author:  segovia [ Tue Jul 20, 2010 10:30 am ]
Post subject:  Re: How do you radius your sides?
Sanding sticks - both are shown here 15 for the back and 28 for the top.

However I am deliberating making a sanding dish for which I will start a new thread as I am usure what the benefits are over my method.

John
Author:  Parser [ Tue Jul 20, 2010 11:12 am ]
Post subject:  Re: How do you radius your sides?
The "Unroll Surface" command works really well in Rhino as well. It literally just unrolls the surface... this command only works for single plane bends though...sounds like the one you use is the ticket for flattening more complex surfaces..!

Trev
Author:  Fred Tellier [ Tue Jul 20, 2010 11:50 am ]
Post subject:  Re: How do you radius your sides?
Radius dish with 80 grit on it, my buddy Tim who is building a guitar in my shop calls it driving the Bus. I do this without a center post to pivot around. Remember to flatten the upper bout of the top and use a non radius UTB brace as explained in Hesh's tutorial to get the fingerboard to fit the top.

Fred
Author:  bluescreek [ Tue Jul 20, 2010 3:23 pm ]
Post subject:  Re: How do you radius your sides?
http://www.youtube.com/watch?v=QYHPCeVRUA4 here is a video. The important thing isn't how you do it but what you do. The purpose for most of us it to make the neck angle match the neck we are using. this allows for a straight transition for the fret board.
Author:  dunwell [ Wed Jul 21, 2010 11:00 am ]
Post subject:  Re: How do you radius your sides?
I use a powered hollow form sanding disk. See info at
http://dunwellguitar.com/
click on the Luthier Pages button and go to the Powered Hollow Form Sander link

FWIW,
Alan D.
Author:  SteveSmith [ Wed Jul 21, 2010 11:59 am ]
Post subject:  Re: How do you radius your sides?
I have a sheet in each dish but I only use 2 dishes idunno I put freezer paper (the kind with a thin layer of plastic on one side) over them when I'm gluing backs and tops in the GoBar deck.
Author:  SteveSmith [ Wed Jul 21, 2010 1:40 pm ]
Post subject:  Re: How do you radius your sides?
I use the freezer paper because the plastic lining keeps glues and finishes from soaking through. Great stuff.
Author:  Darrin D Oilar [ Wed Jul 21, 2010 6:18 pm ]
Post subject:  Re: How do you radius your sides?
I'm not anywhere near as experienced as the posters on here, but I use Colin's method of scribing the arch onto a piece of tape. I affixed that to a paperboard and then transferred it to the sides. I approximated the line with block planes, then sand by "driving the bus".

I only have two radius dishes so both of them have paper. I bought two-packs of the 6x48 belt sander belts from Harbor Freight and spray adhesive them onto the dish.

Darrin
Author:  dunwell [ Thu Jul 22, 2010 11:52 am ]
Post subject:  Re: How do you radius your sides?
Filippo Morelli wrote:
Alan,
Randy Reynolds uses a similar setup which I've seen in action. It takes up a significant amount of space (as a tool dedicated for this activity). Given Randy's shop size I surmise it was a trade-off to get it in there, so it must be very convenient. Unfortunately I don't have the space to justify that much machinery to arch the sides - obviously I'm not building enough :-). For others interested in such a tool, check out Alan's web page - [url]http://dunwellguitar.com/HollowFormSander/HFS-Sander.htm[/img].

For those using sandpaper on a radius dish ... do you have one of those sheets affixed to each radius dish? I have a half dozen dishes so I'm wondering if you hold the sandpaper on there some other way ...

Filippo


Filippo, you don't have to make it a separate tool. I believe I mention that in my discussion. You can build it into an existing work bench. The drive disk sits flush with the table top, that is why I have that extra 1/4" circle of ply as a spacer between the drive disk and the sanding hollow form. I just built it like I did because I already was using that bench as my table saw outfeed roller holder.

I'm currently using self-adhesive rolls of 80 grit on my disks but I'm just using that up. It has a tendency over time to lose it's tack and start to snag at the joints. I seal my hollow forms with what ever old finish I have around the shop, so I can then just warm the self-adhesive stuff with a heat gun and pull it up.

Once the rolls are used up I plan to go to the individual 24" disks. If anyone has a good site for those let me know.

Alan D.
Author:  dunwell [ Thu Jul 22, 2010 3:20 pm ]
Post subject:  Re: How do you radius your sides?
Thanks for the reminder about Shane and his disks. Well worth the $20 to avoid the bother of cutting and pasting my own, they last a long time. I've added his URL into the Colorado Luthiers Links page both in the Woods and the Sanding sections.

Laters,
Alan D.
Author:  John Killin [ Tue Nov 23, 2010 5:39 pm ]
Post subject:  Re: How do you radius your sides?
I know this is an old thread, but I'm right here in my build.

Todd Stock wrote:
I don't flatten the upper bout, choosing instead to use a 60' radius UTB. Works for me.


Todd,

Are you saying that you sand the entire top to your radius (I think you might have said in other posts that you use 28') and then just radius the UTB to 60'? Or do you do the lower bout at the 28' and the upper bout at 60'? I have been planning on using a 25' radius for the top, but was going to flatten the upper bout.

Thanks,

John
Author:  woody b [ Tue Nov 23, 2010 6:02 pm ]
Post subject:  Re: How do you radius your sides?
I just use a dish with sandpaper by hand....but, Bruce Sexauer described his system to me once, and I plan on adopting it sometime. He has a lazy suzan type bearing on the bottom of his dish, attached to a piece of plywood. He clamps the plywood base to his drill press table, the uses a rubber sanding drum against the round dish to turn the dish. I think I've explained it correctly.

My sides are flat on the top, even if I use a radiused top.
Author:  bluescreek [ Tue Nov 23, 2010 6:11 pm ]
Post subject:  Re: How do you radius your sides?
http://www.bluescreekguitars.com/catalo ... x&cPath=19
$18.25 for the PSA disks in 24 inch diameter .
Author:  GregG [ Tue Nov 23, 2010 7:49 pm ]
Post subject:  Re: How do you radius your sides?
I built a motorized dish sander with gear reduction, boy do I love that machine!

Greg
Author:  unkabob [ Tue Nov 23, 2010 9:35 pm ]
Post subject:  Re: How do you radius your sides?
Can you buy 24" sandpaper discs at a place that rents sanders for refinishind hardwood floors?

Bob :ugeek:
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