Official Luthiers Forum!

I'm currently switching over to the radius dish/go bar method of construction, and I've got to the point where I'm getting a friend to CNC me some radius dishes. I was wondering what radiuses you guys use, and wether you switch from guitar to guitar? Or if you have a standard top/back radius used on every instrument?

Jammy have a search of the archives, we've discussed this on numerous occasions, and I believe had at least one poll. Though opinions differ the greatest number of people here use 25' for the top and 15' for the back.

By the way Craft Supplies here in the UK sell the Rolls Royce of radius dishes, double sided 15'/25' cast from phenolic resin. I have been talking to them about them recently and they should be on their website soon. ?64.95 for the two sided dish or ?44.95 each for separate dishes.

Go-bar rods I get from Into the Wind kites in Brighton, they will cut the fibreglass spars to 24" for you and supply the end caps, I use 5mm rods. Very reasonable price too.

Into the Wind

Colin

_________________
I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

25' for tops and 15' for the back here, what Colin said, it's the most commonly used, i must admit that i'd be tempted for 28' like John Hall, for the ease to install the neck joint and the fretboard extension, gotta be easier to sand flat if less domed.

[QUOTE=Colin S] Jammy have a search of the archives, we've discussed this on numerous occasions, and I believe had at least one poll. Though opinions differ the greatest number of people here use 25' for the top and 15' for the back.

By the way Craft Supplies here in the UK sell the Rolls Royce of radius dishes, double sided 15'/25' cast from phenolic resin. I have been talking to them about them recently and they should be on their website soon. ?64.95 for the two sided dish or ?44.95 each for separate dishes.

Go-bar rods I get from Into the Wind kites in Brighton, they will cut the fibreglass spars to 24" for you and supply the end caps, I use 5mm rods. Very reasonable price too.

Into the Wind

Colin[/QUOTE]

That's a coincidence! While visiting a friend in Brighton a couple of weeks ago I stumbled across into the wind. I spent all of the previous week looking for a supplier of the glass fiber rod with no luck, but they had loads! So I stocked up ;)

The resin dishes would be great, but shelling out ?90 at the moment on something I could have machined for next to nothing isn't really an option

Jammy,

I ask this same question a while back and a popular standard combo seems to be 15' back and 25' top, however a close second for backs is 18' and a close second for tops is 28' which from what I believe is favoured by some for the ease of dealing with the fretboard extension.

Cheers and Merry Xmas

(Edit: Well, I guess thats what happens when you start to type a reply, stop to cook the kids dinner and then come back and finish the post )

Kimlarkim39075.3156018518

Glad you found Into the Wind, I know at least half a dozen people who have bought from them now.

I made my own dishes with a router jig, from 18mm MDF. I made four and glued them back to back in radius pairs to help with stability and to add weight (I like em heavy). Buy 24" adhesive sanding discs from Axminster and attach to one side of each pair. Then you have a nice sanding disc one side and a smooth one for gluing the other side. Coat the MDF in boat varnish to seal out the moisture before attaching the sandpaper. If you are making just two, glue the dish to another layer of MDF, when gluing put a few layers of newspaper on top of the sandpaper to protect the wood.

ColinColin S39075.317650463

_________________
I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

Jammy,

I use 13' for my tops and 10' for the backs on all of my varius instruments.

_________________
Dave White
De Faoite Stringed Instruments
". . . the one thing a machine just can't do is give you character and personalities and sometimes that comes with flaws, but it always comes with humanity" Monty Don talking about hand weaving, "Mastercrafts", Weaving, BBC March 2010

First off , the radius isn't as important as much as that you have one. You must decide what neck angle you want to use and that can tell you the radius you should use for the neck geomtery to match the top. The radius is there for 2 main reasons. One to allow movement in humidty change and 2nd for strength.
   Martin uses 1 1/2 degree neck angle and that equates to a 28 foot radius using the same points and distance of the right triangle ploted for the saddle height and distance pluged into the arc of the 28 for circle.
    Now on the backs 15 is a norm . I do build alot off old Martin specs and the specs were vague but from what I have learned it seems they used a 20 on the D's and larger and 15 on the smaller bodies. I was lucky enough to be given access to the production templates.
   Gibson on the otherhand are alot flatter . The stock radii I see are 15-16-20-24-25-28 and 30. I am sure there are others used but these are what I can say that I sell.
    Classical builders are a bit different as they often seem to build upside down and place the top in the harder radius.
    Wishing all a Happy Holiday
john

[QUOTE=Hesh1956] 15' for the top and 25' for the sides and I have used these same radiuses for Dreads, SJs, OMs, and L-OOs.[/QUOTE]

?????

I'm pretty sure Hesh means 15' for the back and 25' for the top

Starting in on the eggnog early I see

_________________
My Facebook Guitar Page

"There's really no wrong way, as long as the results are what's desired." Charles Fox

"We have to constantly remind ourselves what we're doing....No Luthier is putting a man on the moon!" Harry Fleishman

"Generosity is always different in the eye of the person who didn't receive anything, but who wanted some." Waddy Thomson

poor hesh.....

i'm in the 15/25 camp as well. but i am going to experiment with the bigger radii soon, whatever soon means.

[QUOTE=Colin S] Buy 24" adhesive sanding discs from Axminster and attach to one side of each pair. Then you have a nice sanding disc one side and a smooth one for gluing the other side.[/QUOTE]

Wait...Axminster sells 24" sanding discs? Really?

Yep they sure do, just got to know where to look!

600mm sanding discs

I use the 100 grit, gives me a better gluing surface than my old 80 grit ones.

Colin

_________________
I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

Hot diggidy! Good prices, too!

Was planning on making some new dishes (not entirely happy with the surfaces on the ones I'm using now, and my radiussing guides could've done with being a little smoother), and now I know what I'll be lining them with!

I use a 30' on the top, not sure what the diference beteween that and a 28' is. I thought about going to a 28' to get a little more neck angle, just don't want to think about making a new dish right now. 15' on the back. Clinton