Thread: Suggestions for Timber Bending Iron

Originally Posted by Pauls321

Hi there fellows, Thanks for your advice on bending. My sides are pretty much finished now, so thought I would show you the results of your advice. I ended up doing all of this on just the 2 inch pipe only. Hopefully I can get back to the top next week and work on my rosette and sound hole. Then the bracing.

Paul

Those sides have come up a treat! And the blackwood did not discolour at all, right?

Hi Garcia, and thanks. I think the blackwood is a tad faded to what it was. But I did buy some of that oxalic acid (liquid form), and will use it down the track when I am ready to finish the guitar. I tend to think that it will open up the grain of the timber and when I apply some Danish oil, it should really lift it.

Today I cut the rosette slot and also cut out the soundhole on the top. Using a dremel with a circle cutting jig that I made myself. I was very impressed with the result. The plunge router accessory for the dremel would not allow for a radius small enough. Tomorrow I hope to start cutting the bracing for the top, but I am not sure about the very small dish shape, so I am just going to put the bracing on flat. When I come to the bottom, well that will require some re thinking,

Paul

Originally Posted by Pauls321

Tomorrow I hope to start cutting the bracing for the top, but I am not sure about the very small dish shape, so I am just going to put the bracing on flat. When I come to the bottom, well that will require some re thinking,

Paul

The last uke I built had a flat top and I'm pretty sure the back was flat as well. If I did arch the back it would have been using a 15' radius dish. The size of a uke means that you don't really gain much advantage from putting an arch in the top. FYI I build my guitars with a 25 or 30' radius top and my backs are either 15' or if Im doing a Gore style live back I use a 12' radius.

I am not sure about the very small dish shape, so I am just going to put the bracing on flat.

The dish is very important, especially for a bigger instrument such as a guitar. It is done to stop cracking when the humidity changes so I would recommend you do use a dish unless you keep the guitar at a constant humidity. The radius also gives you the neck angle, but the primary reason is for humidity control. You will notice after you brace the top that it will go convex when the humidity increases and will go concave when the humidity decreases. You need to be careful about humidity when you glue the braces. Aim for around 40%, and keep the top (and back) at around 40% for a few days. When everything is glued together a completely flat top is more likely to crack than a dished one.

hmmm, after all that, I glued my bracing onto my top yesterday (even made a go bar clamping system, one that I can dismantle with 3/8" threaded rods), and yes it was flat, and at present in this heat wave specially on the mid north coast, the humidity is running at about 90%, has been for about 6 weeks now. I haven't actually worked out how to build these dishes yet.

Oh well, lets see how it goes and it is my first acoustic attempt.

Paul

90% humidity and flat, not good at all, very high risk of failure. You really do need to control your humidity. The top will go concave and/or split when the humidity drops. There are several ways to get the humidity down, e.g. dehumidifier, hot box, or wait until the weather dries out etc. I used to wait, but now have a dehumidifier and life is much easier. I would get those braces off ASAP.

Originally Posted by kiwigeo

The last uke I built had a flat top and I'm pretty sure the back was flat as well. If I did arch the back it would have been using a 15' radius dish. The size of a uke means that you don't really gain much advantage from putting an arch in the top. FYI I build my guitars with a 25 or 30' radius top and my backs are either 15' or if Im doing a Gore style live back I use a 12' radius.

Not being a Uke/Guitar builder, can I clarify that the radii are in feet (') or is it a typo, and it should be in inches (")?

Just for my own knowledge.

Hey Mandoman, Get the braces off,.....but they are glued on. I just spent the last couple of hours finishing them off, as I only had the main ones on yesterday. Your saying somehow rip them off again,..???

Here on the Coffs Coast its a humid climate most of the year, I was wrong about the 90%, I checked, its only 80% today,...!

And Cava I think Kiwi did mean feet, I am doing some googling on these dish things.

If this fails I will put it down to experience. And rethink. The solid body guitars I have made (5 of), have turned out nice, I luvvvvv the last one I made, play it every night before bed.

Thanks again, Paul

Originally Posted by cava

Not being a Uke/Guitar builder, can I clarify that the radii are in feet (') or is it a typo, and it should be in inches (")?

Just for my own knowledge.

No typo....Radius figures are in feet..

Hey there Mandoman and Kiwi. Thought I would give you pair an update on what I doing. Mandoman worried me enough to halt my process and investigate these radius dishes. I just spent two days making two. Fingers crossed the calculations that I followed are correct. I made a 25 foot one, and a 15 foot one. So unfortunately I will can the top I already made, looked pretty good also. I'm heading down to Timber Heaven tomorrow, also known as Boutique Timbers and getting some more Australian Red Cedar from Mal.

For your info here are a couple of pics of my radius dishes.

Paul

Good, in the long run it usually pays to backtrack and fix the mistakes. Just make sure the humidity is 40-45% when yo glue it up again

Originally Posted by Pauls321

Hey there Mandoman and Kiwi. Thought I would give you pair an update on what I doing. Mandoman worried me enough to halt my process and investigate these radius dishes. I just spent two days making two. Fingers crossed the calculations that I followed are correct. I made a 25 foot one, and a 15 foot one. So unfortunately I will can the top I already made, looked pretty good also. I'm heading down to Timber Heaven tomorrow, also known as Boutique Timbers and getting some more Australian Red Cedar from Mal.

For your info here are a couple of pics of my radius dishes.

Paul

Nice work on the dishes. Re the top....are you sure you cant whack off the braces and re-brace the top? A sharp cabinet chisel followed up by a scraper should get the braces off cleanly.

Thanks Mandoman and Kiwi. That's not a bad idea Kiwi, I might have a go at whacking off those braces. What have I got to lose, and the top was looking nice. If I get them down low enough I could put it through my home made drum sander. Interesting point. But I will still head down to Boutique Timbers as planned, Mal and Greg are top blokes down there. And Mandoman, I take your point about the 40 - 45% but the only way I could physically do that is to bring everything in to my lounge room, turn the a/c on, but I don't think my wife would like that idea. My shed is totally open, just a normal double garage with two roller doors. I take my car out when I work and roll my saws etc into the middle of the garage. Humidity last couple of days was 85%, right now at 9.20pm its 75%.

Paul

Paul,

Just get the bulk of the brace of with the chisel. Finish off with a scraper and then dress up with sandpaper. No need to drum sand the whole top....that;s going to make the whole top thinner which is best avoided unless your top is on the thick side. Over the years Ive whacked off lots of braces.....you get good at it after awhile