uncle.fogey - Posted - 05/09/2012:  15:38:26

I’m thinking this is going to be a long thread.  Everyone likes resonators why shouldn’t they - they resonate!

OK - they don’t - I think they “reflect”, but I like them anyway.



First of all , since this is about design and building, I have 3 design criteria (3 - there are 3, and 3 shall be the number of their counting):



(1) It has to be able to be made without me buying a hydraulic press, which won’t fit into my shop, and specially machined forms



(2) It has to be somewhat adaptable to custom banjo needs



(3) IT HAS TO FIT INTO A CASE YOU CAN BUY .



So, according to criterion 3, we are talking about a max OD of 13  5/8”, and a max height of around 1  3/4”.  I have a guitar I made 1n 1964 thet won’t fit in any case.  It’s an awesome guitar, but it won’t fit in any case. I ought to have a T shirt that says “won’t fit in any case”.   OK, so I  have my max dimensions in mind.



There are several popular ways of building resonators, the most popular being the method whereby the bottom is laminated in a hydraulic press from (usually) 3 layers of poplar or similar, with a veneer on the outside, and the rim is steam bent, also with a veneer.  The binding hides the joint.

Then, there is the “pieplate” resonator. so named because of the famous food - ought to be called the “pizza resonator”

What I am aiming for is something with a rim that’s steam bent and laminated, and a bottom that’s turned from solid wood because that’s what meets my criteria.

 I don’t think this is a “step down” from anything - probably a “step up”, but I’m willing to spend the time - I am not a mass producer.



So, my design paradigm (hate that word) model (?) is the book-matched 2 piece backs used on violins, cellos, etc. Here’s a pic of two Stradivariuses.  Good enough for him - good enough for me.

i779.photobucket.com/albums/yy...trads.jpg" style="width: 500px; height: 659px;" />



I get a nice 7” wide board and glue up a square that I can get a 14” circle out of - you will notice that this piece is almost quarter sawn where the joint is - great if you can get it, but not necessary:



Cherry is VERY stable. I am building another one out of curly maple - less stable.

Here are 2 - glue-ups - I have a REALLY nice piece of cherry.  I am trying butterfly joints on one because I think it looks cool.

The wood has to be 7/8" thick because of what you have to do to make the back. 3/4" is just too scary.

Then, I need strips of whatever the outside rim will be (in this case cherry and curly maple) and the inside rim, which is beech - I make these larger than they need to be because of shrinkage and dressing down, I have a bending form made from birch plywood ans a plastic template for the length of the strips:

dickinnorwich - Posted - 05/10/2012:  05:30:32

Ken:

Can you spend a little time and explain to the good folks in Banjo Land the logic and utility behind your plastic template strips. Admittedly, it took me a while to see how well they worked. It's another one of those clever, homemade tools that should be in every banjo makers tool box. Thanks. 

uncle.fogey - Posted - 05/10/2012:  06:03:46

quote:

---

Originally posted by dickinnorwich

Ken:

Can you spend a little time and explain to the good folks in Banjo Land the logic and utility behind your plastic template strips. Admittedly, it took me a while to see how well they worked. It's another one of those clever, homemade tools that should be in every banjo makers tool box. Thanks. 

---

Thanks, Dick, I will do that.

uncle.fogey - Posted - 05/10/2012:  07:49:03

What Dick was alluding to is the idea of using the circumference measurement to determine the diameter of banjo parts, which are often either wood, that moves, or things like bracket bands, tone ring parts, and tension hoops which are usually out of round,



Here’s a picture of some of the templates and circumference strips I use:









The circumference of a circle is 3.1416 times the diameter, which means that every inch of diameter translates to  3.1416” of circumference - so much easier to measure, and 3 times more accurate .  Dick and I used these things while we were making a bracket band, which couldn’t be measured with a caliper while we were rolling it.



I use them for:

wood strips to laminate rims

notches in tension hoops

diameters of tension hoops

bracket bands

tone ring parts

resonator rim parts

rim turning



Here are a few pics - when you have a rim on the lathe, you can easily check how close you are to the right diameter. In the first picture the strip still has a 1/2” gap, which means that the diameter is still .159 too large.

In the second picture, we are right on the money.





Here’s a diameter check on a tone ring, and notches on a tension hoop:





 

Fathand - Posted - 05/10/2012:  08:09:51

Just some thoughts:

The Siminoff book shows using two 20" Disc Harrows (36" Diameter vs. the usual 42") for forms and C Clamping them together in order to laminate the back of the resonator. I suppose you could always turn wood forms as well but would be tricky making the inner and outer match. These don't sound especially expensive.  

quote:

---

Originally posted by uncle.fogey

I’m thinking this is going to be a long thread.  Everyone likes resonators why shouldn’t they - they resonate!

OK - they don’t - I think they “reflect”, but I like them anyway.



First of all , since this is about design and building, I have 3 design criteria (3 - there are 3, and 3 shall be the number of their counting):



(1) It has to be able to be made without me buying a hydraulic press, which won’t fit into my shop, and specially machined forms



(2) It has to be somewhat adaptable to custom banjo needs



(3) IT HAS TO FIT INTO A CASE YOU CAN BUY .



So, according to criterion 3, we are talking about a max OD of 13  5/8”, and a max height of around 1  3/4”.  I have a guitar I made 1n 1964 thet won’t fit in any case.  It’s an awesome guitar, but it won’t fit in any case. I ought to have a T shirt that says “won’t fit in any case”.   OK, so I  have my max dimensions in mind.



There are several popular ways of building resonators, the most popular being the method whereby the bottom is laminated in a hydraulic press from (usually) 3 layers of poplar or similar, with a veneer on the outside, and the rim is steam bent, also with a veneer.  The binding hides the joint.

Then, there is the “pieplate” resonator. so named because of the famous food - ought to be called the “pizza resonator”

What I am aiming for is something with a rim that’s steam bent and laminated, and a bottom that’s turned from solid wood because that’s what meets my criteria.

 I don’t think this is a “step down” from anything - probably a “step up”, but I’m willing to spend the time - I am not a mass producer.



So, my design paradigm (hate that word) model (?) is the book-matched 2 piece backs used on violins, cellos, etc. Here’s a pic of two Stradivariuses.  Good enough for him - good enough for me.

i779.photobucket.com/albums/yy...trads.jpg" style="width: 500px; height: 659px" />



I get a nice 7” wide board and glue up a square that I can get a 14” circle out of - you will notice that this piece is almost quarter sawn where the joint is - great if you can get it, but not necessary:



Cherry is VERY stable. I am building another one out of curly maple - less stable.

Here are 2 - glue-ups - I have a REALLY nice piece of cherry.  I am trying butterfly joints on one because I think it looks cool.

 

The wood has to be 7/8" thick because of what you have to do to make the back. 3/4" is just too scary.

Then, I need strips of whatever the outside rim will be (in this case cherry and curly maple) and the inside rim, which is beech - I make these larger than they need to be because of shrinkage and dressing down, I have a bending form made from birch plywood ans a plastic template for the length of the strips:

---

uncle.fogey - Posted - 05/10/2012:  09:56:51

By the way, My PW Gibson, unaltered resonator has a 36" radius on the bottom, not 42" - maybe Gibson changed the radius later on.

I thought about it and considered it, disc harrow blades cost about $15. I rejected the disc harrow idea for my own projects because:

(1) I wanted to try the book match approach

(2) I don't have a way to make 14" circles from poplar veneers, or any veneers that large - they would have to be somewhere in the neighborhood of 3/16" thick

(3) I don't think that C-clamps would work all that well - you really  need a hydraulic press, and I don't have room  for one in my shop

(4) I have been told by a person who is very familiar with this process that you should heat the forms.

(5) Once you have created the "dish", by squeezing the veneers between the forms, you have a thing that cannot be very easily chucked on a lathe (if at all) or dealt with easily

(6) You have to fit the rim to that bottom dish, which requires fairly elaborate chucking setups

uncle.fogey - Posted - 05/10/2012:  10:09:38

The next step is to bend the parts for the resonator rim.

I’m making 3 resonators, but most of the pictures I’m showing will be the cherry one.

The technique is pretty much the same from one to the other.



(1) The outside cherry lamination is bent and clamped into the form until it stabilizes.

Then the clamps and cauls are taken off, and the inner beech ring is bent and glued and clamped against the cherry one with the joints opposite one another.

The resulting 2-ply rim will be very strong and stable:





So we sit the rim aside and start on the back - you can be making more rims while you are doing the rest of the resonator.

I don’t want to have any marks or holes in the resonator when it’s finished, so I am using a method of turning the back that won’t make marks.



First, I cut the book-matched glued up board into a circle slightly bigger than 13  5/8” to allow for initial centering error, and I make a circle where the 4” faceplate will be screwed, then I screw the face plate onto the circle.  I am screwing it onto the INSIDE of the resonator back with short screws, so these holes will be turned away later on .  Always mark the faceplate orientation in case you have to take it off for some reason.



Then I can face off what will be the back of the resonator, find the exact center and draw another 4” circle.  The front and back of the resonator board are now parallel :





Now I can turn the back to the proper arc, checking it with my plexiglas template shown earlier.  When I get it right, I sand it while it’s on the lathe.

 I leave a 4” round flat spot to attach the faceplate from the other side when I turn the inside:







Now the sanded back can be removed from the faceplate:

Next will be the inside.

 

uncle.fogey - Posted - 05/10/2012:  14:22:50

You remember the two plexiglas templates I made for the inside and outside of the resonator - the wall thickness we want is 1/4”:





In order to get the thickness of the bottom right, we drill a hole with a forstner bit so that the point is just a little shy of what the finished thickness should be. This hole has to be big enough to get a little plywood slug on the end of the dead center in there -, this hole and the screw holes from the face plate will all be turned away:







Now we make a “sacrificial interface” out of urethane foam to glue between a plywood disc screwed to the faceplate and the flat center section we left on the back of the resonator.

In the past, we would use kraft paper for this - strong enough to hold the spinning thing on the lathe, but weak enough to get off without splitting out the wood. Nowadays I like the uretane, used for making signs. It’s called “sign foam”.  I glue it on with a few circles of super glue. We’re going to cut through it and destroy it in the end:



Now we put the faceplate back on the lathe, and use a plywood block to press against the resonator - this is a safety device as well as a “clamp” to hold the super glued faceplate in place while it dries.  There’s no need to subject the thing to any stress until the very end.

I should mention, that this whole turning process takes but a couple of hours I only face off the inside surface and make a kind of rabbet for the rim to be glued to:





We clamp the rim onto the back. The steam bent beech core rim is very tough and rigid, and it holds the whole thing in place firmly.  Think of it as the sides of a guitar or violin on stroids.  This ain’t goin’ nowhere.

I still hold it in place with the plywood disc while I turn it:



Here you can see what it looks like as I am turning out the inside - I am following the drawing for the side profile:



As we turn down the inside, we cut past the screw holes from the faceplate, and eventually have to take off the large plywood disc and substitute the one that fits in the Forstner bit hole, finally we back the dead center off altogether, and finish the turning, using the template as a guide.

Then we sand the inside:



NOW, while it’s still on the faceplate, all nicely centered, and it hasn’t had much of a chance to move, we cut rabbets for binding. These are nominally .060 deep and a bit more than 1/4” wide

Never take it off the faceplate until you don’t need it to be on there anymore.  Wood isn’t metal - this isn’t a cast bronze Gibson tone ring - it’s a living, breathing thing, and it WILL move. The longer you let it sit, the more chance it has to move:



Now we glue on the bindings - this can be Corian (as I am using), or nitrocellulose, wood, ABS, etc.  Whatever you like

Remember that the corners of this resonator are going to get banged around - we glue them with super glue and use a lot of clamps - we sand it on the lathe ( fortunately, we kept the face plate on:



THEN, we don’t need the faceplate any more, so we cut through that urethane “sacrifical” layer, and hand-plane and sand the bottom of the resonator





Finally, we have a  resonator - we still have to cut the notch for the heel, and finish it, but for now, we can put it aside:





Next will be the neck ( if anyone’s still interested).

Kirk Jacobs - Posted - 05/10/2012:  14:48:12

Yep, still interested. Thanks again for taking the time to document for us.

Dave1climber - Posted - 05/10/2012:  15:13:10

Ken

Your methods make this process look easy, as a long time wood worker I know that a life time of knowledge is going into this topic.

Yes I am still interested.

Thanks for your time and efforts.

Dave

Waltj - Posted - 05/10/2012:  15:58:54

Thank you again

Walt

wuzapicker - Posted - 05/10/2012:  16:53:05

Ken,

Thanks heaps!

You have no idea how this information gets me thinking about an old vision. (Guess what that one is?) If a standard resonator can be built this way, so can one slightly smaller. It all becomes possible!

I'm very interested in this series. And since I'm also embarking upon a neck build project, I'd feel privileged to have your input and instruction before I start. Especially since you build banjos with dowel sticks where the fit up tolerances are more exacting.

Thanks,

Michael

Ladelnutts - Posted - 05/10/2012:  18:40:48

Fantastic. I am always amazed at what talented people can make with their hands. It is so nice to see something being hand made in lieu of mass produced. Thanks for documenting the process.

XXXris - Posted - 05/10/2012:  22:17:27

Enjoyed that! More!

I'd like to see photos of the butterfly one when it is done....

uncle.fogey - Posted - 05/11/2012:  05:31:20

quote:

---

Originally posted by XXXris

Enjoyed that! More!

I'd like to see photos of the butterfly one when it is done....

---

I am having second thoughts about the butterfly joints for a resonator.  I'm afraid they might actually cause the joint to come apart because of differences in expansion and contraction between the length and width grain of the wood.

I have used butterfly joints many times in cabinets and furniture, but always with a gap between the boards that the joints are holding together:

With a resonator, I'm afraid it might tear itself apart at the ends of the butterflies unless I used REALLY small butterflies.  I even thought about having a resonator with a gap, but thought that would be very odd.

If I ever DO make a butterfly resonator, I'll post it.  It would look good with a neck that had bow-tie inlays.

wuzapicker - Posted - 05/11/2012:  09:00:35

My Paramount Leader (and every other one I've owned or seen) have a solid wood resonator back consisting of two pieces of East India Rosewood laminated with a decorative 3/32" wide strip of Holly between them. The resonator back is flat inside and given a gloss finish. The resonator back appears to have been shaped by hand as the arc is rather flattened in the center. 



The resonator walls are Poplar wood laminated and shaped similar to Ken's example, but the outside sidewall is veneered with East India Rosewood to match the neck and resonator.  But the sidewall interior also appears to have been hand shaped rather than turned on a lathe.  

The photos below show the inside and outside under lighting.

Edited by - wuzapicker on 05/11/2012 09:04:27

uncle.fogey - Posted - 05/11/2012:  09:41:32

Thanks for showing that!   Those are very nice!!

I suspected that the Paramount solid rosewood resonators must have been made in that way. It's not unlike an archtop guitar, mandolin, violin, or cello back.

One way to put a veneer on the outside rim of a resonator (the way I do it), is to use a thicker than normal piece of veneer and laminate it into the rim as the outer lamination layer, as part of the making of the rim.  This precludes having to turn the rim down to a smaller diameter in order to accommodate the veneer, as well as eliminating an extra step in the process.

wuzapicker - Posted - 05/11/2012:  10:28:12

quote:

---

Originally posted by uncle.fogey

One way to put a veneer on the outside rim of a resonator (the way I do it), is to use a thicker than normal piece of veneer and laminate it into the rim as the outer lamination layer, as part of the making of the rim.  This precludes having to turn the rim down to a smaller diameter in order to accommodate the veneer, as well as eliminating an extra step in the process.

---

That makes sense.  On this resonator the outside East India Rosewood veneer seems to be about 1/16" thick wrapped around the middle Poplar which to make about 5/32" wall thickness at the ledge.  The inner walls are tapered.  Each sidewall layer runs in alternating directions.  The inside (short) Poplar layer and the Rosewood veneer have the grain running horizontally, while the center Poplar layer has the grain direction at 90 degrees to the others.  The resonator flange scrapes against the tall center Poplar layer.  I think by having the grain of the middle layer run parallel to axial centerline of the banjo better prevents the flange from chipping wood off the inside lip over time, and the thick Rosewood veneer strengthens it.    It makes sense from an engineering standpoint, even if it represents a little more work.

BNJOMAKR - Posted - 05/11/2012:  11:30:11

That is one nice looking resonator!

uncle.fogey - Posted - 05/11/2012:  12:46:24

Thank you, Marvin!

uncle.fogey - Posted - 05/11/2012:  12:54:21

quote:

---

Originally posted by wuzapicker

quote:

---

Originally posted by uncle.fogey

One way to put a veneer on the outside rim of a resonator (the way I do it), is to use a thicker than normal piece of veneer and laminate it into the rim as the outer lamination layer, as part of the making of the rim.  This precludes having to turn the rim down to a smaller diameter in order to accommodate the veneer, as well as eliminating an extra step in the process.

---

That makes sense.  On this resonator the outside East India Rosewood veneer seems to be about 1/16" thick wrapped around the middle Poplar which to make about 5/32" wall thickness at the ledge.  The inner walls are tapered.  Each sidewall layer runs in alternating directions.  The inside (short) Poplar layer and the Rosewood veneer have the grain running horizontally, while the center Poplar layer has the grain direction at 90 degrees to the others.  The resonator flange scrapes against the tall center Poplar layer.  I think by having the grain of the middle layer run parallel to axial centerline of the banjo better prevents the flange from chipping wood off the inside lip over time, and the thick Rosewood veneer strengthens it.    It makes sense from an engineering standpoint, even if it represents a little more work.

 

---

If the veneer is 1/16" thick, it could well be the outer lamination of the construction - That's very thick for a normal 

veneer", and it would allow for a little variation in the depth of the rabbet for the binding and sanding down in the finishing.  It would be fascinating to see how they joined the rim into the bottom.

A solid rosewood resonator is pretty cool!!

uncle.fogey - Posted - 05/11/2012:  13:38:05

When I started this thread (these threads) I was talking about what parts I would be making (or trying to make), and used some smoke-and-mirrors to illustrate that as well as I could.

Before I go on to the subject of neck-building, I thought it would be interesting to show a composite picture of what's actually happened in all the 9 threads so far - no smoke-and-mirrors - I hope I didn't make a mistake by breaking it into categories, but you can look back if you want to:

It's a lot of work and a lot of information.

Now, I'm on to the neck, which I think is a subject many are interested in - more so than tension hoops.

wuzapicker - Posted - 05/11/2012:  13:57:38

I thought your tension hoop build was fascinating! You took the die cast concept right out of my thinking and showed that a one-of is truly possible.

Regarding the method Lange used to attach the resonator back to the resonator side cylinder, It was pretty much the standard way, with the edge of the back glued to the walls and the joint hidden with wooden purfling and bindings.

Anyway, thanks! I truly appreciate the spirit and level of detail you endeavor to present in this series.

Seeders - Posted - 05/11/2012:  22:19:28

quote:

---

Originally posted by uncle.fogey

quote:

---

Originally posted by XXXris

Enjoyed that! More!

I'd like to see photos of the butterfly one when it is done....

---

I am having second thoughts about the butterfly joints for a resonator.  I'm afraid they might actually cause the joint to come apart because of differences in expansion and contraction between the length and width grain of the wood.

I have used butterfly joints many times in cabinets and furniture, but always with a gap between the boards that the joints are holding together:

With a resonator, I'm afraid it might tear itself apart at the ends of the butterflies unless I used REALLY small butterflies.  I even thought about having a resonator with a gap, but thought that would be very odd.

If I ever DO make a butterfly resonator, I'll post it.  It would look good with a neck that had bow-tie inlays.

---

We use a lot of butterflies in our furniture as well, mostly in large slab tables that have cracks that need to be stabilized to keep them from getting larger over time. Here's a picture on our blog of one that sold recently.

1.bp.blogspot.com/-7ehRD6gFAXU...close.jpg

I think you should go for it with the resonator, I think you'll be fine, especially if they're just inlayed into the cherry and not too deep. I'd be surprised if such small pieces of wood expanded enough to split the cherry apart. No way of knowing without giving it a shot.

I was wondering if you had any noticeable issues with solid resonators in general with expansion and contraction. Do they tend to warp or shift at all over time because of the expansion and contraction? I thought this was one of the reasons they were more commonly laminated, other than the production standpoint? I'm planning on building resonators soon and have the means to laminate and veneer or turn them and I'm curious of the benefits of both methods.

I'm really enjoying the posts you've been making, very informative. It's great seeing the usually hidden methods of other peoples building techniques. It's a great way to refine my own.

Thanks!

Waltj - Posted - 05/12/2012:  04:43:33

I turned a resonator back about a year and a half ago out of curly soft maple. It is one piece of wood with no glue joints. I did it the same way as shown in this thread. To date it has been stable as a rock

Walt

Back of resonator

uncle.fogey - Posted - 05/12/2012:  05:32:52

We use a lot of butterflies in our furniture as well, mostly in large slab tables that have cracks that need to be stabilized to keep them from getting larger over time. Here's a picture on our blog of one that sold recently.

1.bp.blogspot.com/-7ehRD6gFAXU...close.jpg

I think you should go for it with the resonator, I think you'll be fine, especially if they're just inlayed into the cherry and not too deep. I'd be surprised if such small pieces of wood expanded enough to split the cherry apart. No way of knowing without giving it a shot.

I was wondering if you had any noticeable issues with solid resonators in general with expansion and contraction. Do they tend to warp or shift at all over time because of the expansion and contraction? I thought this was one of the reasons they were more commonly laminated, other than the production standpoint? I'm planning on building resonators soon and have the means to laminate and veneer or turn them and I'm curious of the benefits of both methods.

---

Thanks!

That big walnut table is really beautiful!  It reminds me of the things George Nakashima made.  Butterfly joints work beautifully to stabilize a crack.

I have not made that butterfly back into a resonator yet, but I'm going to let it sit and see what happens.  If it stays put, I'll go for it.

In answer to your question, I don't have enough history on the solid resonators to be able to make a definitive statement, but I'm sure they will not come apart.   Wuzapicker posted those shots of the bookmatched rosewood Paramount ones, which have held up prrfectly, and my wife's violin, which is several hundred years old has never developed a crack in the back  I think solid and 2-piece backs are a perfectly sound and long proven method of constructing musical instruments.

For one thing, they are arched or dished, which allows them to flex in a more 3-dimensional way than a flat piece.  In guitars with a flat back, they generally put a cross-grain strip inside the joint, but not on violins, cellos, basses or arch-top guitars, which are 3-dimensional.

I think banjo resonators have been historically pressed in a mold from laminations because it's cheaper and easier to do, and allows fancy veneers to be applied to the back, and banjo resonators, despite the name, do not need to resonate like the back of a violin or mandolin, so making them out of solid wood is overkill for a manufacturing operation.

It will be VERY interesting to see how the cherry and maple ones I made for this project sound on the finished banjos, and I intend to switch them around.

uncle.fogey - Posted - 05/12/2012:  05:37:44

quote:

---

Originally posted by Waltj

I turned a resonator back about a year and a half ago out of curly soft maple. It is one piece of wood with no glue joints. I did it the same way as shown in this thread. To date it has been stable as a rock



Walt

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It looks beautiful, Walt! - the color and finish is great. Thanks for showing that.

When you say "soft maple", was it red maple?

If I had wide enough boards, I'd try some one-piece ones myself.