radiusing a soundboard?

I take a smaller (6 or 8 inch) diameter piece of mdf and sand it on the dome to create the matching form for the bridge. Put sand paper on it and sand the bottoms of your bridges prior to gluing them on so they match the radius of the top.
Hey Dominator, I knew there must be a clever way of doing this. Sweet. cheers Steve
 
If the lower part of the soundboard, south of the sound port, or hole, is domed, and the board north of the sound hole is flat, the domed area is necessarily higher. Does one need to account for that change in height with slimmer bridges?
 
Hi Mattclara
If the lower part of the soundboard, south of the sound port, or hole, is domed, and the board north of the sound hole is flat, the domed area is necessarily higher. Does one need to account for that change in height with slimmer bridges?
I'm putting a 20' radius dome on my uke tops and the amount of doming is not a lot I'd guess it's 1mm higher in the middle than the sides on a soprano so with that radius it's not a huge issue. cheers Steve
 
I sent this to Pete's email, but thought it would be great to get an answer here, so:

Hey Pete,

I was watching your video on making/using a solera. I have a couple questions.

Is the middle brace below the sound hole made flat or with a radius?

Do you keep the neck at a 90 degree angle, since the upper part of the uke is flat or do you angle it a little because of the radius in the lower body?

Thanks
 
Hi Mattclara I'm putting a 20' radius dome on my uke tops and the amount of doming is not a lot I'd guess it's 1mm higher in the middle than the sides on a soprano so with that radius it's not a huge issue. cheers Steve
Closer to 1/2 mm I make it..Hardly worth the trouble.;) Go for 10' rad if you want approx: 1mm proud
 
First instrument builder here...
As I understand it from the wisdom here, there are 3 options to soundboards:
1. Flat
2. Radiused in a round dish
3. Somehow flat on the lower (?) bout and then angled thinner on the upper end??
I was planning to radius the back of this tenor at 15' and the top at 20'.
Perhaps this is simpler than I am making it?
I do appreciate this forum!!
Chuck (not THE Chuck) Barnett ;-)
 
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I've done dozens of instruments with flat soundboards. Sound perfectly fine to me. In fact to prove that radiused is better than flat you would have to build two virtually identical instruments and (preferably) stick them in a blind test.
 
I've done dozens of instruments with flat soundboards. Sound perfectly fine to me. In fact to prove that radiused is better than flat you would have to build two virtually identical instruments and (preferably) stick them in a blind test.

I am also of the flat-top school and they sound fine to me... Also a lot easier. Radiusing the top brings some advantages but also brings in a couple of troublesome issues. the first of which is your bridge will need to lay flat on there somehow (do able) and then there are binding routing issues to get a good binding channel on a radiused top (also do able or just don't bother to bind). There are other issues too which might rear their ugly little heads that I won't go into. I would say since this is your first build, just leave the top flat and the uke will sound just fine if you have thinned and braced your top correctly. You have other issues to deal with without trying to radius' the top on a first build. The back however is easier to radius with fewer issues so definitely radius that. 15' is pretty subtle. You can go more radical than that. Don't forget to taper the sides! Good luck and don't forget to send pitchers!
 
Thanks for the encouragement. -)
The thinning of the top certainly baffles me. Tone tap tuning is a deep mystery and i feel I've no clue what I'm doing. I've got the redwood top to a shade over 10 thousandths and have no idea if that is too thick or too thin. I guess it being as you mentioned my first build i should simply get it done and give up on doing a great job. But that frustrates the daylights out of me.
 
Yes, my math brain is deficit. :) So why do I hear from some don't go that thin, yet you and some others think it's okay to go that thin with redwood? One person I have talked to said you can go too thin, past the point where you can tap nice tone to a point where the board sounds like cardboard. I'm also concerned about going to thin in view of some instruments that I have seen that are so thin that the braces would actually be discerned on the surface of the top. Remember, this is my first shot at this. I have no experience and thus I ask many, many questions. I apologize for inundating this forum with my questions in ignorance. Once I get through this first one I will be a whole lot happier. :)
 
I apologize for inundating this forum with my questions in ignorance. Once I get through this first one I will be a whole lot happier. :)

No problem Chuck. It IS tough. But here is the thing: Until you make a few and tap a few you don't have any reference in your mind to refer too. It is not a hard thing, it just takes some learning. I do not claim to have mastered this part of the process, but I have progressed to the point where I'm starting to hear what might be a good thickness. In the absence of experience, just aim for a thickness and write it down so next time you have a reference. I've built three redwood topped ukes and talked with people who build with redwood a lot. In my limited experience it seems to me that redwood really behaves like the softwood that it is and likes to be a little thicker than you think. I think I over thinned my first two tops and while the ukes sound ok they have no cajones if you know what I mean. Redwood is a funny wood. The sound is quite delicate and pretty if you are of that mind... In my experience and others I've talked with is the stuff likes to be a little thicker on the side of thinness which is like 80-85+ mil. Kinda thick or else it seems to rat out if you dig in. Personally not my first choice in tone wood even though I live in redwood country and it is all around me. Also it not that redwood sounds bad, it is just a question of taste and what kind of sound you are looking for. The nice thing about building your own uke is that you can get that exact sound that sounds good to you and that is where the fun starts. Oh, and it never ends.
 
Thank you, Sequoia! I appreciate your taking the time to give me a little perspective. I've decided to go with about .085 and call it good at that. I have been doing a pretty fair job of making notes on this project. Upcoming, I have some decisions to make in other areas such as what sort of bridge to use, how to attach the neck, what to do about binding. A lot of research I expect. :)
 
If you are talking about the "bridge plate" then you don't do anything to it because it is thin enough to just bend into the shape when you glue it on via the go bar deck.

If you meant the actual bridge the answer is yes. After making the dish and applying the sand paper I take a smaller (6 or 8 inch) diameter piece of mdf and sand it on the dome to create the matching form for the bridge. Put sand paper on it and sand the bottoms of your bridges prior to gluing them on so they match the radius of the top.

This is a great idea! I've been searching the forums all day trying to find info like this. Thanks!
 
Don't forget to taper the sides!

Sequoia, I am going to be radiusing the backs of my next line of builds. Everyone says to taper the sides as well as using a radius dish. I'm having trouble wrapping my head around that geometry. If you taper the sides, wouldn't shaping them with the radius dish wipe out any taper that you added earlier?
 
Sequoia, I am going to be radiusing the backs of my next line of builds. Everyone says to taper the sides as well as using a radius dish. I'm having trouble wrapping my head around that geometry. If you taper the sides, wouldn't shaping them with the radius dish wipe out any taper that you added earlier?

I don't use a radius dish to taper my sides. I just make my neck block lower than my tail block by a quarter inch, glue in my linings in a continuous line head to tail (not critical), plane sides down to linings and then sand everything flat on a flat surface. Viola! One quarter inch tapered sides. No stinking radius dishes required.
 
Sequoia, I am going to be radiusing the backs of my next line of builds. Everyone says to taper the sides as well as using a radius dish. I'm having trouble wrapping my head around that geometry. If you taper the sides, wouldn't shaping them with the radius dish wipe out any taper that you added earlier?

No. The dish is concave..meaning that the deepest part is the centre. If you were to put a flat plane on the dish, only parts of the plane would touch the curve (the corners of the ends of the plane because they are the furthest away from the centre of the dish. This assumes that the length of the plane is greater than the width).

Similarly, with your sides in the mold, you gradually sand on the dish, more material is removed from each end before the midline (waist) would touch the sandpaper. If you were to take the sides apart and stretch them out, the waist area would be thicker than the ends (i.e. More would have been sanded from the ends than the waist). Having a taper saves you from excess sanding.
 
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No. The dish is concave..meaning that the deepest part is the centre. If you were to put a flat plane on the dish, only parts of the plane would touch the curve (the corners of the ends of the plane because they are the furthest away from the centre of the dish. This assumes that the length of the plane is greater than the width).

Similarly, with your sides in the mold, you gradually sand on the dish, more material is removed from each end before the midline (waist) would touch the sandpaper. If you were to take the sides apart and stretch them out, the waist area would be thicker than the ends (i.e. More would have been sanded from the ends than the waist). Having a taper saves you from excess sanding.

Perfect explanation. Thanks guys!
 
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