Charity Acoustic

[fryovanni]

To be honest with you Erik. I sample surface temp.(the temp. of the steel). I have become used to the readings and know where it should be while it is cooking. Not the most spot on accurate method, but I have had good success with it.

Peace,Rich

[erikbojerik]

What ToneMonkey is talking about is the possibility that the thermocouple is touching a metal of a different composition.

The thermocouple works by virtue of the fact that two different metals in contact with each other have an electrical resistance that varies with temperature, and the voltmeter is calibrated only for the two metals that make up this particular TC. Put the TC in contact with a 3rd metal and all bets are off calibration-wise.

[thegarehanman]

You're only using one thermocouple,eric? You should see the pressure vessel I'm working on; there are upwards of 60 thermocouples and about the same amount of pressure taps all going to one stationary turbine blade . It's a nightmare.

Back on point...beautiful work, I'm taking notes. I wish I had the time to get crack'n on my acoustic.

edit: erm...double post?

Edited November 10, 2006 by thegarehanman

[ToneMonkey]

You're only using one thermocouple,eric? You should see the pressure vessel I'm working on; there are upwards of 60 thermocouples and about the same amount of pressure taps all going to one stationary turbine blade . It's a nightmare.

Back on point...beautiful work, I'm taking notes. I wish I had the time to get crack'n on my acoustic.

edit: erm...double post?

Back off point.....Are you just looking at one blade and passing the air over that. I've done blade and turbine design at uni. Rather you than me mate, never again.

Back on point again. I really need to make myself an acoustic too. Only 6 months to the wedding so hopefully within about 8 months, I may have a bit of money again......Unless someone wants to make me one for a wedding present of course

[thegarehanman]

Yes, it's a stationary blade, but the air is heated via a natural gas combuster. This experiment is for studying the effects of different film cooling temperatures on the efficiency of the particular section o fthe turbine associated with this blade.

[ToneMonkey]

oooh, sounds interesting.

I take it you have the holes in the blade and this produces a film of coolant over the blade. I've not actually done any film cooling so I don't know anything about it.

Does the film not flow off the blade with the shear of the air behind it and then pebble dash the blade behind? I take it these turbines are multi stage. All seems so long ago now

Err, this is a little off topic isn't it? Maybe we should start an off topic discussion because my PM's don't work

[erikbojerik]

I really need to make myself an acoustic too. Only 6 months to the wedding so hopefully within about 8 months, I may have a bit of money again......

Dude...start now so that you can finish in time to serenade her at the wedding.

[ToneMonkey]

Obviously you've never heard me sing...........

..........or play the guitar for that matter

[erikbojerik]

Obviously you've never heard me sing...........

..........or play the guitar for that matter

Yeah but it's the thought that counts right? (at least for her...can't say the same for the rest of the audience...)

OK, last few days saw me radius-sand the edges (25' radius) using not a dish, but just a long 2x4 with the proper radius routed in and sandpaper stuck down, worked in steering-wheel fashion. Got the bindings in and sanded flush, and got to work fitting the neck. I'm doing a Cumpiano mortise & tenon bolt-on with metal cross dowels in the tenon.

7° angle is going to work just fine I think. I got the tenon and neck angle cut on a table saw, with the inside corners cleaned up on a router table using a flush trim bit. But next time I'm going to figure out some kind of jig to do the whole thing on the router table (much better control than a table saw).

[fryovanni]

It's looking great Erik . It is gonna be a beauty.

Peace,Rich

[Daniel Sorbera]

I don't know what you ment by " radius-sand the edges (25' radius) using not a dish" What is radius sanding?

[fryovanni]

I don't know what you ment by " radius-sand the edges (25' radius) using not a dish" What is radius sanding?

Sanding the sides and kerifing around the top and back of the rim to accept the soundboard and back radius. I like a 25'+ on soundboards, and 15'+ on the back(really radius is a personal preference thang).

Peace,Rich

[Daniel Sorbera]

Okay gotcha.

[erikbojerik]

Some more work done over the past month. Used the Dremel cut-off wheel to make a rectangular opening for the preamp, and drilled the 1/2" hole for the endpin jack. Then realized I had made the heel block too thick and so I cut & chiseled it down some.

Under the edges of the preamp rout I glued some small strips of mahogany kerf to strengthen it up some.

[erikbojerik]

Got the rosewood fretboard done this week, from my stash of Brazilian. I decided to bind this one with the offcuts so that the grain would match. So I had to rough it out square and plane it down, radius the entire blank (16" radius), then trim off the sides at a taper right underneath the locations of the E-strings. Cut the slots with my radial arm saw (StewMac template with the 1/16" pin stuck into the saw's fence), then glued the offcuts back on with Titebond, cleaning out the slots after letting it set 30 minutes. Then I trimmed the fretboard to just 1/16" outside the final taper and touched up the radius again. I am quite pleased with the result.

This is a shot just before touching up the radius.

Edited December 5, 2006 by erikbojerik

[erikbojerik]

Here's the fret slotting setup, for those interested...StewMac fret slotting sawblade on a radial arm saw. The locating pin sticks out of the fence ~1/2" to the right of the saw cut channel, flush with the table surface. When I'm done slotting and want to go back to cross cutting, I just flip the fence 180° for the big blade.

I actually use the big blade to cut the slot for the nut in much the same way.

Edited December 5, 2006 by erikbojerik

[fryovanni]

Fretboard looks great Erik. Nice slotting set up .

Peace,Rich

[erikbojerik]

Closed the box this week. First I taped off all the surfaces where glue goes to attach the back (heel & tail blocks, linings) then sprayed a coat of Zinseer's shellac on the inside of the box (and inside surface of the back). This will minimize any humidity-related changes to the soundbox. Here you can see that I placed the output jack into the box with some string attached, and secured the wire inside with small spruce tie-downs to keep the wire from flapping about inside.

http://img.photobucket.com/albums/v241/boj...oustic/box1.jpg

Then I glued on the back, held down with cam clamps and home-rolled spool clamps. Overnight glue cure.

[fryovanni]

Looking super Erik!. Your work is very clean(I am jealous ).

It is good to hear this

First I taped off all the surfaces where glue goes to attach the back (heel & tail blocks, linings) then sprayed a coat of Zinseer's shellac on the inside of the box (and inside surface of the back). This will minimize any humidity-related changes to the soundbox.

. At least I know I am not the only person that does this. It has always made good sense to me.

Peace,Rich

[erikbojerik]

Thanks Rich; I'm not sure that I'm any cleaner than the next guy, but I'm definitely getting cleaner as I go. For instance...the stair-step in the tail block. I could say that it was added for extra punch and sustain....but really I made it too thick for the strap button output jack and didn't really think much about it until I went to order the jack . Luckily there was just enough room to lower the blade from the radial arm saw in there to trim it down.

Here's some shots of the neck, which is now completed and ready for finishing (Tru Oil). Ebony top and backstrap on the headstock; I'll probably make little curves in the corners of the ebony bridge to match the theme.

backstrap

After having to radius the brazilian rosewood fretboard 3 times (due to binding screwups), it was slightly thin for my tastes so I went and added an ebony laminate underneath before gluing onto the neck blank. The neck is a single piece of walnut with a stacked heel and EI rosewood heel cap.

Here you can see the Cumpiano-style neck joint....I say "style" because Cumpiano probably doesn't routinely have to dowel and re-drill his neck tenons. The problem I had was in trying to get the neck angle just right; I went through 3 different methods (table saw, band saw, router table) and would constantly under- or overshoot the angle, or the opposite sides of the heel would be slightly different from each other so that I'd have a tight joint on one side but not the other. Finally the router table did it for me, but by that time I had shaved so much off the tenon that I had to re-locate the cross dowels deeper in. Good thing I left the headstock thickness for AFTER this step.

neck heel

During neck construction, I also discovered that my 3/4" Home Depot cross dowels (substantially better than the Woodcraft ones) checked in at 0.80" AFTER I had cut the tenon to 0.75" width . There was nothing to do but take 0.05" off the metal dowels.

Edited January 1, 2007 by erikbojerik

[erikbojerik]

Here's how I'm dealing with the internal wiring. Spruce brace offcuts, drilled for twist-tie.

[erikbojerik]

Wow....I am pumped today.

After trying out both of the StewMac Dremel attachments for routing the binding channel over the past couple of years, and being mightily dissatisfied with the results, I took the plunge and put together a suspended router jig to do this. Took about 4 hours to put it together and get it functional. Basically, you take a cabinet drawer, stand it on its face, replace the drawer slides with heavy-duty ones, make a shelf for your router to sit on, then mount the whole works in a frame. A spring suspends the router off the deck and the drawer slides allow the router to float up and down to follow the contour of the guitar top.

Oh yeah...and I used the StewMac binding router bit set. Easiest and cleanest binding channel I've ever done.

Here's the rig; one could make a frame with very tight tolerances, but I found the drawer slides worked most smoothly with the whole frame a bit loose. Mine is just a pair of 2x4s with one cross-member at the top, and a perpendicular foot at the bottom of each for clamping to the workbench (you leave the space under the router as free as possible).

Edited January 6, 2007 by erikbojerik

[erikbojerik]

The guitar sits in a cork-lined 4-post carriage with adjustable height, so that the edge is roughly on the same plane all around. The top registers on a small 1/4" thick shim of wood glued underneath the shelf, close to the router bit. Best to do a test cut on scrap, but even then the channel depth can vary slightly with a top that has an arch on it (which mine does, 25' radius). But it is clean, sharp and perpendicular to the sides.

Edited January 7, 2007 by erikbojerik

[erikbojerik]

Here's the result, the first ledge for the purfling. A little scraping and it's good to go.

I then did the next ledge for the binding and painted the entire channel with a thin coat of shellac. I am cutting the channels only slightly oversized (by like 0.05") as I am using CA so the binding shouldn't swell so much.

Purfling went on today (tape and wick in CA), tomorrow I'll cut the notch for the end graft and do it and the final binding strip.

Binding is always slightly frightening for me. You take a nice clean piece of woodworking and by the time the binding is in, the edge has glue all over it. I know it cleans up nice, but still....

[fryovanni]

Erik,

That is looking good mister! Binding and purfling is very challenging. Your going about it the right way and paying attension to those details. I am sure it will turn out great. Very impressive work for sure.

FWIW(not that I am sure this is a better aproch-just what I have been doing). I generally cut my binding channel first then take the purfling channel. I just figured it was safer to take smaller depth cuts. I seal with shellac like you do. I place regular Tiebond in my joints(I would use HHG,but I am just not fast enough yet). I have wicked CA before on a rosette, and it would up a little discolored(the white in my fine line). That may have been because it didn't wick evenly(your results may be very different). I also seal the binding and purfling after I scrape them true.

Peace,Rich