Radiusing the back and top

smctunes · #1 02-06-2010, 03:37 PM

Hey all, I just want to say thanks for all the advice so far, before I move on to my questions about radiusing.

I've found some fantastically-priced radiused dishes from www.kennethmichaelguitars.com, but the bank account is getting dangerously low from all the various startup costs I've been dealing with. So, I'm looking for an alternative method.

I came across a post a while ago where some fella was using 3x5 flash cards, stacked on top of each other but slightly offset, to build a kind of ramp which worked as a radiusing device. Has anyone else had experience with this?

Also, I've considered just creating a radiused sanding block by hand, and then sanding the braces to match. The question there is this: If I have no radius dish for the top to rest in while I'm clamping the already-radiused braces on, what will happen? When I take the clamps off, will the top just bounce right into shape, to fit the curve? It seems like I might snap something if I do it this way.

Coke_zero · #2 02-06-2010, 03:55 PM

Woody from this forum told me about that, I'm not sure if he has done it himself, but he doesn't give bad information so it must work.

gregg · #3 02-06-2010, 04:19 PM

Do you have a router? If so it's not too difficult to build a sled to run the router on that will cut the radius dish for you. It is not too expensive to use MDF for the dish, I'm not sure but maybe $15-20 could get the job done....that and a day in sawdust

You can get around building a dish but it will make your life much easier for sure. Shoot me an PM if you need help.

Cheers,

Coke_zero · #4 02-06-2010, 04:26 PM

Gregg is right but if you do decide to use the other idea, using the cards will work but it would be very hard to actually radius the braces using those cards but will probably work for gluing. If you have a spare $50 (I imported it to the UK so the £:$ = bargain) get a brace maker from luthiersuppliers.com. I haven't got mine yet, but I've only heard good things about it.

gregg · #5 02-06-2010, 04:44 PM

Coke Zero I have on of those Brace-Maker's that I do not use, Shoot me a PM maybe we can find a new home for it......It does work great I just have other ways to do my shaping.

Cheers,

Coke_zero · #6 02-06-2010, 04:59 PM

I meant I just bought one, shame really as I would have loved to buy one second hand

Been a bad with with offers for equipment this week, missed out on a free binding machine & now missed out on getting a brace maker second hand

Thank you for the kind offer though.

gregg · #7 02-06-2010, 06:31 PM

No problem Coke Zero.....Dang, I barely used mine, wasn't really looking to get rid of it, but not using it either, figured I might as well let someone else find some use in it. I made a power dish sander a few years ago, now that is the ticket, not cheap but worth it!!

Cheers,

Rod True · #8 02-06-2010, 08:20 PM

Here's another way to make radius dishes http://www.anzlf.com/viewtopic.php?t=231 on the cheap.

You don't need to build a radius into the top. Olson's and Ryan's don't have one and the R. Taylor line offers a truly flat top as well.... neither do I, and I feel I'm in pretty good company.

SteveS · #9 02-10-2010, 03:05 PM

Check out the Luthier interest tab on my website. I have a quick tutorial on making these dishes. Let me know if you have any questions.

arie · #10 02-11-2010, 02:29 PM

On the guitar we are building, I radiused the braces and used a "compression pad" (hi-jacked new bath mat folded in half) under the bottom to force the plate to conform to the braces. It takes very little force and worked great. The top plate will be flat -no radius needed.

martinedwards · #11 02-11-2010, 04:13 PM

I radius my braces on the belt sander then clamp them to the top and back. no dishes, just clamps.

never had a problem

dekutree64 · #12 02-11-2010, 04:39 PM

How do you no-dishers deal with the joint between the top and sides? Do you just sand the gluing surface on the sides flat and clamp the top tightly so it bends flat at the edges, or do you use some clever method of sanding to approximate the curvature for a cleaner fit?

jeremy3220 · #13 02-11-2010, 09:16 PM

Quote:

Originally Posted by dekutree64

How do you no-dishers deal with the joint between the top and sides? Do you just sand the gluing surface on the sides flat and clamp the top tightly so it bends flat at the edges, or do you use some clever method of sanding to approximate the curvature for a cleaner fit?

I've glued a radiused(30') top to a flat rim. Huss and Dalton does this on some models. It works great; it doesn't require any forceful manipulation.

I've also used a radiused sanding stick to radius the back rim... not as precise as a dish but it works.

WhistlingFish · #14 02-11-2010, 10:04 PM

Quote:

Originally Posted by dekutree64

How do you no-dishers deal with the joint between the top and sides? Do you just sand the gluing surface on the sides flat and clamp the top tightly so it bends flat at the edges, or do you use some clever method of sanding to approximate the curvature for a cleaner fit?

You can get away with gluing your radiused tops to a flat rim, but you should still try to build some fall-away into the linings to accommodate the dome of the top. With the rim set in your body mould, a sanding stick rotating on a central pivot of appropriate height will give you the consistency you're after.

Where the back is concerned, bear in mind that radiused dishes are a relatively recent development and that builders have traditionally tapered the sides to allow for the back arch. Typically, the sides are of a consistent height from the tailblock to the waist area, then fall away gradually to the point at which the upper bout bends sharply towards the headblock, after which the rims are almost level again. Without dishes, the greatest challenge is in ramping the gluing surfaces of the headblock and tailblock exactly to match the curvature of the top and back plates. Without a close match, inconsistencies will telegraph through the finished instrument as a bump or dip. I speak from experience!

Gluing curved braces to the back plate is relatively simple without a dish, using an appropriately curved clamping caul similar to the one shown below. I lined this one with closed-cell foam to even out the clamping pressure. Use it with a go-bar deck, or position it on the outer face of the back plate in line with the brace to be glued, apply glue to the brace and clamp as you see fit.

Having said all that, I use home-made radiused dishes and still maintain that they're cheap, easy to make (if a little messy) and will reduce what is otherwise a daunting task to the level of mindless drudgery!