Benedetto Archtop Build

[Dave Stewart]

It's supposed to be 3/8" thick but the top flexes when pressed down and the edge rises which caused the corner to be 2/8" thick at the curve! Grrrr...

After brightening the pic, actually looks like 3/16" (correct) down to 1/8", which is thin for the edge.

This will effect the binding I'm sure.

Toss it in the bin and start anew, or make it work?

Fortunately, the spruce is a lot easier to carve, but I'd hate to redo it.

Suggestions?

I 'd keep it ... just don't go thinner (ie don't continue the recurve trough) into that area of the upper bout. Fair the adjacent regions to make it look right. (although the binding will thin in that area & be noticeable)
You could also put veneer on the underside of this region to raise it up a bit.... reflatten the underside & make things a little less noticeable, if you know what I mean.

Next time I'll cut the edge thickness 'before' carving! I thought I was being conservative with the edge. I didn't want to ruin it with a plane.

You weren't wrong ..... as I said above, I go to 1/4", then do most of the outside carving just for that reason, before reducing to 3/16". The difference I think is you carved the inside BEFORE doing the 3/16" edge (and pushing down on the hollowed plate caused the edge to flair up as it went through the router). Although some cupping does happen regardless, due to released tension from the carving ... I see it too. In my case, I route to 3/16" in short sections (4-6") while pressing down with jointer push-pads on either side. Just a technique issue.

[Ron Sommers]

After thinking about it over night and looking over the diagram, I plan to use the top and attempt to blend the recurve into the binding.

The binding sits higher at 3/16" and slopes down. The top edge would be cut away by the binding channel. I have 3/16" depth to "play with" sloping it into the recurve.

I don't have much wiggle room and It just might work.

The worst that could happen is it gets trashed and I recarve the top.

[Randolph Rhett]

...
Still wondering what I'm 'listening' for when tapping the plate...

Don't worry, you'll know. Holding the piece to your ear at first you will tap on a piece of dead wood. "Clink..clink..." Then, after you've smoothed it out and thinned it (more than you were expecting) suddenly it will sound like you tapped on a good crystal glass. "Piiiing...Piiiing..." It will vibrate in your hands a little like holding a tuning fork. You'll get excited. You'll carve some more. The glass will start to sound rich, even drum like. "Duuuum.... Duuuum...." You will really feel the vibrations in your hand. Oh, now it's intoxicating. You figure "more? do I dare?". You'll do some more carving. Now you notice its a little floppy, not as musical. "Thwappwapwap... Thwappwapwap..." Oh sh&*t! Yep, now you've gone too far. Tada!! The learning process. Next one will be even better....

I have more faith in my finger tips and ears than in calipers. On the other hand, I'm just doing this for fun. I use cheap wood. Others can probably give you exact Hz and tell you the difference between main dipole resonance and hemhotz resonance.

[Ron Sommers]

Ok, been busy with life...but have made some progress.

Figured I need to sand the sides and that will cause a lot of dust.

So I built this dust collector. Got the plans on line.
Sure wish I had a roller set up to bend the cone, but it turned out ok.
It's made out of tin used for HVAC ducting. Inexpensive.

The best part is it really does a great job! Lot's of air flow!

[Ron Sommers]

Also forgot to mention I got a new tech job so that's been sucking up time as well.

My plan was to make a side bender as well. It's almost completed.

I have the screw to attach to push the cutaway into shape.

Need to design the sides to get that to work.

I have the Watco heaters to connect still.

[Ron Sommers]

Ok the next bit of progress is the cutting of the 'f' holes.

Had to use a piece of underlayment.
Cut it in the shape of the top and laid out the position for the 'f' holes.

Jigsawed them out and filed to near perfect.

I was thinking 'pin router' but without the pin.
The bit shank runs along the edge of the cutout (pin-like) and surprisingly worked very well.

I considered purchasing a Makita trim router for $100+ but decided to go for one of those Harbor Freight
'Buffalo' brand units. Yet another surprise! It's not half bad. The sound is tight. I suppose I expected a screaming motor?
It did the job well. Never purchased a Chinese unit before. For as little as I plan to use it, it's a deal!

So, the way it worked is I put the top face down in the jig with the underlayment on top.
Clamped the 'sandwich' securely together.
Turned on the router and gently set it (plunged) into the 'f' where it did a fine job of hogging out the 'f'
as I followed the 'f' pattern with the upper part of the 1/4" bit shank.

It was nearly effortless.

Now to bind the 'f's and size the sides. Hopefully sooner than later!

I want to finish this by Christmas...!

[Hans Bezemer]

Good to see you picked it up again, Ron. Keep it going!

[Barry Daniels]

Well done! Are you going to bind the f-holes?

[Ron Sommers]

Thanks guys for the encouragement!

Yes, I plan to bind them with wood.

I looked at stewmac et al and decided $50 was a bit steep to purchase ready made, so I thought I'd 'roll my own'...

Come to find out it's about the same price! Oh well, I'll be using what I got.

The side material is about 5.5" wide by 2/8" and I only need 3" for the sides (less really) so I want to use the remainder as the binding and I think there's plenty for the whole guitar. 12 feet if I calculated correctly? I need less than that.

I got some 0.30 sheets of pecan veneer that I was hoping to dye black, but it didn't soak all the way through.

So, back to the drawing board... bought some 0.20 black fiber binding strips and some 0.20 maple. I'll use the pecan for in between.

[Barry Daniels]

It is hard to bind the f-hole with plastic. It is Very difficult to do it with wood binding. Sure you want to do that?

[Ron Sommers]

I guess I'll try at least?

I mean... how hard could it be?


It's only wood.


I'll force it to submit to my will.... bawahaa haa haaa!

[Michael Lewis]

The bend in the cutaway looks a bit tight to me. Tight bends are often troublesome, just sayin'.

Binding f holes with plastic is much easier than with most wood. If using wood I suggest using your .020" veneers and use three layers to equal your .060" binding, then black .020, white (maple) .020, etc. for your purfling. Wood will bend around the top and back but will be difficult around the sides, especially around the waist and cutaway.

[Ron Sommers]

Well, it's been a while since I've posted.

Not that I haven't been busy on the guitar. I have!
The cold garage tends to slow things down for me.

Here are a few pics to peruse.

The first one (up top) is interesting in that the bearing marked the wood. Yes, it was spinning, but the light brown is oil from the bearing!
Not the middle of the bout however, that is seepage from when I sealed the interior with balsam varnish.

A bit frustrating yes. I had that cleaned up pretty well.

Also, the maple got a crease in it from the bearing.

Note the middle of the cutaway where the rise happens in the channel? I'll have to chisel that to match the rest of the relief.
Best I can tell is I didn't carve the top equally around that edge.

I cut the channel using the method from Bob's Archtop Blog [found here: http://bobsarchtop.blogspot.com/2012/03 ... -wood.html]

Binding the 'f' hole was not without its challenges.

Once I got the thickness down, the bending was fairly easy.
Some splitting did occur on the tight curves, but after I soaked and bent them I put them in a mold I cut and that kept the split small.
The 'mold' was made with a band saw kerf in a board. I pressed the bent wood into the groove and let it dry.
After the wood dried sufficiently, I wet it again before gluing. This caused it to expand, but also made it flexible.

As can be seen after scraping the wood down to the surface any 'splitting' disappeared.

Gluing the pieces into place was an exercise in creativity. I had to use filler pieces and shims to get it to bind evenly and properly.
Tedious comes to mind, but you can see the result.

I think if I was to do this again I would make a reusable jig out of wood in the shape of the 'f', instead of pieces of wood.
Something with a screw to expand the jig to press and hold the wood binding until the glue set.

I plan to thickness the binding and finish the body next.

[Patrick Hanna]

My compliments to you on the success of your bound f-holes. I'm not sure I could have convinced myself to try that. I don't even bind them with plastic!

[Barry Daniels]

Carefully remove the hump in the binding channel with a small chisel. The valleys in the top at the cutaway can be smoothed out later when you are leveling the top edge of the binding but make sure your purflings are thick enough and at the right elevation to allow this.

Also, you may be able to steam out the compression from the bearing. I can't imagine how hard you must have been pressing on that to create that dent.

[Greg McKnight]

Looking good! Nice build you've got going there.

I need to stop procrastinating and get a build thread on here myself.

[Ron Sommers]

On second thought I'm not so sure it's oil, as it could be burned wood? As for pressing hard, I wasn't at all.
I think the bearing scored the wood (might have been 'stuck'?) as it too was spinning as fast as the bit, 30k rpms.

Of course, it had to be in the most difficult area to work in!!

I've learned a whole lot doing this guitar and I'm sure there's more to come still!


I haven't approached the neck yet.

I've been debating a truss rod vs carbon fiber strips vs a carbon fiber D tube.

Anyone have pointers on any or all? Suggestions? Reasons? Good? Bad?

[Mark Swanson]

That is burned wood. The bearing was not doing what it is supposed to do and was sticking.

[David King]

I've been using Boelube chain lubricant from the bike store on my router bit bearings. It's very thin and cleans all the goop out and then dries leaving a thin layer of dry wax lube that doesn't attract dust or stain wood.

[Ron Sommers]

I'll have to get some of that lube! Who'd a thunk!?


I was able to sand paper off the burn mark and the groove.

One thing I noticed is the difference in width of the channel around the guitar.

It goes from 4.45 mm to 5.31 mm depending on where I measured for total thickness (upper/lower bout - includes both bindings). You'd think it would be uniform?

I think I'll be able to blend the side into the binding and I'm not adding for glue thickness, so it should meet in the middle or close to it.

The inside binding varies less - from 1.88 to 2.3 mm.