uncle.fogey - Posted - 04/13/2012:  16:00:32

I know I posted a lot of this before, but here it is again, with a few new pictures.

There are a lot of ways to make banjo rims, and they all have their fans and attributes.

I Have 2 methods I use, a "finger-joint" type rim and a steam bent one. The finger-joint method uses pieces of wood from a small section of a board, uses very little wood, can orient the grain in precisely the correct orientation, is extremely strong and can be made from virtually any wood species, including tropical species and those that don't glue well.

I call this the "interlock" rim, and have used these very successfully.  I normally put a veneer inside to match the neck and hide the vertical joints, which I don't like for aesthetic reasons.

When the bindings and heel cap are on them the look really nice, and they are VERY lively rims"

As I said before, they can be made in any species:

The other method, which I have been exploring, and will use on this project is steam bending.

You can start with a log for this, and I'm using cherry and beech.

Beech because of it's very bright sound, strength and ability to be bent.  Here are some pictures of the preliminary slat production:

After you have cut the slats to a larger-than-final size, they have to be dried a bit and clamped so that they don't warp too much,

Then you cook them in a steam box, and bend them into a form - each one is coated with glue and clamped in:

You can see the sequence here:

So, I have a pile of these, which will be left to sit for a while, them turned down as needed:

They are all a little different, and the one on the bottom left has a maple outer layer.

The beech - cherry is what I will use for this project.

xnavyguy - Posted - 04/13/2012:  17:22:01

I always enjoy seeing the work of a REAL craftsman.  Thanks for sharing.

Waltj - Posted - 04/13/2012:  17:25:08

Thank you

Walt

ken61 - Posted - 04/13/2012:  17:42:37

Ken

Two wonderful ideas for rims.  I have built several vertcal staved rims, but the idea of finger jointed rims  and maybe 12 staves is great. 

I like the steam bent multi specie wood rims also.  Great ideas.

thanks for sharing..

ken

uncle.fogey - Posted - 04/13/2012:  18:21:23

quote:

---

Originally posted by ken61

Ken

 

Two wonderful ideas for rims.  I have built several vertcal staved rims, but the idea of finger jointed rims  and maybe 12 staves is great. 

I like the steam bent multi specie wood rims also.  Great ideas.

 

thanks for sharing..

 

ken

 

---

Thanks, Ken,

There are not vertical staves, they are horizontal grain with 16 sections with a quarter figure on the top:

You wouldn't really need finger joints for a regular stave construction

HarleyQ - Posted - 04/13/2012:  19:32:33

Very good Ken, looking forward to it. Thanks

aeroweenie - Posted - 04/13/2012:  19:50:01

Very useful information on the two primary ways of making rims, thanks!

XXXris - Posted - 04/13/2012:  20:35:29

Ken: This is good reading.... Here is a follow up to my previous question. On your bent rims, how do you get the butt-joints so precise?

Chris

BanjoBach - Posted - 04/14/2012:  01:40:58

Great looking work Ken, I sure like the excellent fit of your finger joints. I sure wish I had such a machine to make rims like a dream.

Randall - Posted - 04/14/2012:  04:41:12

On your ply rims, you using a scarf joint or a butt joint? It's hard to tell in your picture.

uncle.fogey - Posted - 04/14/2012:  05:07:21

What kind of joints work best is driven by the system used to bend the rim laminations; My first rims were bent around an inner form, and I used scarf joints.  I found this to be a pain in the neck with the equipment I have, so I switched to the outer form shown in the previous pictures.  In this way, I can get the joints very tight.  With a scarf joint, the tops of the scarfs tend to get bent up and sometimes split while you are gluing it up.  Butts are harder to bend, but they hold up better (for me)

On the old Gibson rims, they used scarf joints and positioned them opposite one another on the rim. 

The old Vega rims had butt-joints, and were staggered

On mine I stagger the joints like the old Vegas.  The very most critical thing is having the lengths of the laminations exactly right.  If you have a very small gap, you can drive a wedge in there and push the wood out, making it tighter.

My rims consist of an outer cherry lamination, 2 inner beech laminations and an inner cherry lamination that is really not much more than a trim veneer, which can be turned down to as little as .060 or so (this can be any kind of wood, so that it matches the neck).

I do it so that the outer joint winds up under the heel of the neck and that's where I make the dowel hole, the inner beech layers have their joints at 3:00 and 9:00, and the inner joint is at the tailpiece end, hardly visible because of the end of the dowel.

uncle.fogey - Posted - 04/14/2012:  05:19:55

In order to determine the precise lengths of the slats, you need to make a flexible plastic template, and you can mark each lamination length with a pencil as you go and transfer the measurement to the wood slat.

Here's a picture of the one I use for resonator rims, it's exactly the same system you would use for rim laminations:

Obviously, the length of each slat will be determined by the diameter and the thickness of the slat, and as you add successive laminations, the diameter changes - that's why I like something I can make pencil lines on.

Randall - Posted - 04/14/2012:  06:07:26

Thanks for the ply rim education! I have tried the scarf joint a time or two. But my ply rim looked like some Asian banjo rim!! A good 12"disc sander would be good to sand down the ends of each board to allow for a perfect fit. Cut the boards a fraction too long and sand offa few thousands as you go! I know that takes time and time is money. But it would be right!! I'm sure vega used the wedge deal to save time and material.

uncle.fogey - Posted - 04/14/2012:  06:39:17

Randall,

You can deliberately make the slat a little too long, and "kerf" it with a thin bladed Japanese saw. Then it "snaps" into place.

Dave1climber - Posted - 04/14/2012:  06:49:59

Ken

One again you make it look easy!  

Dave

Randall - Posted - 04/14/2012:  07:57:19

I have always said anything is easy if you have the correct tools and you know what you are doing!! You have both!!

HolyGrass - Posted - 04/14/2012:  09:55:48

how exactly do you cut those fingers?

uncle.fogey - Posted - 04/14/2012:  10:01:33

quote:

---

Originally posted by HolyGrass

how exactly do you cut those fingers?

---

With a table-saw and a shaper cutter on a table-mounted router.  I'll admit, it's tricky and a little scary because you're cutting into  end grain with the shaper.  When I do it, I do a bunch of them at once because the setups are tricky, and you waste a few pieces.

Randall - Posted - 04/14/2012:  10:30:03

quote:

---

Originally posted by uncle.fogey

quote:

---

Originally posted by HolyGrass

how exactly do you cut those fingers?

---

With a table-saw and a shaper cutter on a table-mounted router.  I'll admit, it's tricky and a little scary because you're cutting into  end grain with the shaper.  When I do it, I do a bunch of them at once because the setups are tricky, and you waste a few pieces.

---

The more pieces you put in a circle, the more critical  the cuts are!!  If your are using 16, each piece needs 11.25 degrees on each end.  NO MORE, NO LESS!! plus the length of each block must be exact too!!  It's bad enough putting 8 blocks together at 22.5 degrees on each end!!

uncle.fogey - Posted - 04/14/2012:  10:46:30

It's even trickier than that, because if you cut the segments all to 11.25  degrees, they would fit together in a normal "stave" cylinder, but you have to take into account that the fingers from one section extend into the next one, so the "join angle" of each 2 segments is in the middle of the fingers and the angle on the ends of the fingers is slightly different depending on the length of the fingers.  Also, you have to take the reduction in diameter caused by the finger joints into consideration, and make the sections longer.

I can't even explain it properly - I get confused myself.  Bending wood into a circle is simpler, at least from a mathematical standpoint.

Randall - Posted - 04/14/2012:  10:56:27

I sit and tried to figure out the piece of art you have created called a "finger joint rim"! I got a horrible headache and had to drink too much beer to clear out my mind!! I'll just stick to my block rim!! It works too!!

I do want to try to make a ply rim out of European Beech. Right now have have too many project started to start another til I finish some of them up!!

Grum - Posted - 04/15/2012:  17:13:04

Since this is all about sound and tone I'm keen to know what sort of glue you use.

Won't the extra glue in the finger joint (as compared to a butt joint) deaden the sound? I'm assuming that more glue and joints is a bad thing in that each joint should interfere with the sound waves moving through the wood. Tony Pass said he thought the glue in the joints was a problem so he developed a technique of ensuring the fit was as close to perfect as possible with a correspondingly less amount of glue.

Of course, this is all academic since the proof is in the sound.