Osthoff shop, getting ready for Woodstock and more

[John Osthoff]

I have been a bit quiet here on the AGF but that does not mean I have not been busy in the shop. A couple of people have expressed some interest in seeing some build threads and what else is going on in the shop, so I will start this thread with a couple of builds mostly relating to the Woodstock Invitational show. My buddy bob has a thread going about the attendees and more info about the show here.

First off let me mention the Woodstock Show. I was originally asked to take a year off and in interest of giving someone else a spot at the show I had planned to wait until 2016 to exhibit again. With a couple of late cancelations, there was a spot that opened up in the Utopia building (not in the same building as the main event) and I will be at a table of there. Cool!

Ok back to the shop. As mentioned, I have a lot going on in there but I will concentrate on what I am working on for the show.

First up is one of my FS models. It is Higuerilla (Sacha Rosewood) paired with a Port Orford Cedar top. This one will might get some "Woodstock" details.

I have had some interest in my Slope Shouldered Dreads again. I sort of got way from them a few years ago, but I have a couple on the books. I slightly redesigned this model and will be offering them in both a 14fret and 12fret neck to body connection. I am hoping to get one together for the show. It will be a Quilted Mahogany with Adirondack Spruce Top.

Plenty of other stuff going on too including a Cocobolo SJ. More details of that will emerge (possibly in a different thread)

Thanks for checking this out and I will get some progress photos up soon.

[John Osthoff]

Here will be a couple of "generic" pictures of the builds. These photos came from the Cocobolo SJ build but will be very similar for the Woodstock builds so I won't repeat them for those:

To begin, I evaluate the tops. I do this a number of ways, but I also use a couple of criteria to "help" me determine some criteria for them.









While a lot of this can be done by feel, the process I use allows me to get some numbers, things that I can keep for records and or reject the top based on them

[roberts]

Glad you'll be at Woodstock, John. The list didn't look right without you....Robert

[mikealpine]

John, a few years back I played a Sinker Redwood guitar that was a real standout at the show. Looking forward to this year's offerings!

[John Osthoff]

Robert,

Thanks, I am really glad to be coming back to the show. I hope we can catch up some at the show

Mike,

Thanks, I hope you get a chance to try out my stuff again this year.


I did not take too many pictures of the process on the FS model, but I will post some shots of what I have done so far in another reply.

In the meantime, here is some stuff on the SD. As mentioned this model is being reintroduced due to renewed interest in it. I will be offering both a 12-fret and 14-fret option. For this build, I am opted for the 12-fret. Although based a little more on tradition, these SD will still get the radial brace pattern, composite bridge, compensated nut and saddle, along with the stealth truss-rod cover. It has been a while since I did a slot-head, but this one will most likely get one of these.

The fixturing and templates are all new for this build:

I needed to make new side templates, and in this shot, you can see part of the process:



Now the templates are made, it is time to transfer the profile to the quilted mahogany



I cut-up some low-figured snakewood for the bindings:



After the sides are bent, the inside core (of mahogany) is added and the two parts are laminated together to create the double sides:



More to come

[psychojohn]

Could you provide some details on what is going on with what look like coffee grounds on the wood ? Must have something to do with tapping ?

John

[John Osthoff]

Originally Posted by psychojohn

Could you provide some details on what is going on with what look like coffee grounds on the wood ? Must have something to do with tapping ?

John

Actually they are poppy seeds, but that isn’t really important. Some use glitter, hence you will hear the name glitter patterns. This stuff is based on Chiladni’s research on vibrating plates.

A lot of builders don’t bother with this stuff, but indirectly at some level they probably are. The poppy seeds land on the node points, and if you grab a piece a wood at that node point and bang on it you will hear a ringing “dooong.” I listen for the note to be musical, good sustain, no, distortion (usually indicates a crack) but the actual note as meaning too. That is what I am measuring in the pictures. I am showing 2 patterns in my pictures that give me some information that I use in setting up my target thicknesses for the tops (and backs.) The picture with the shorter lines going across the grain are given me information about the stiffness of the top along the grain. The one with the longer lines along the grain are more about the stiffness across the grain. The particular note (frequency) will vary on thickness, so it is important that the top be a uniform (known) thickness. The spectrum analysis (colorful chart picture) will align to the frequencies that I am finding with the poppy seeds. This sort of dynamic testing helps to “guide” me in some of the decisions I make with the bracing and thickness of the tops and backs.

Some luthiers do more of a static test where they will measure deflection with weights. This works well too but it works best when the plates have been (all) uniformly thicknessed. I experimented with that approach but ultimately found a process through the dynamic testing that works for me.

Once again, many don’t use this sort of approach and build very successful guitars. I am not saying my approach is better, only that it is better for me. It gives me real (empirical) data that I can use. When I tap on a top (and I do that a lot) I really listen carefully. However my memory for sound can fool me so I like having numbers and pictures to help me remember and visualize my process. There is a lot more to it, but hopefully that sheds some light on what I am up to.

[psychojohn]

Originally Posted by John Osthoff

Actually they are poppy seeds, but that isn’t really important. Some use glitter, hence you will hear the name glitter patterns. This stuff is based on Chiladni’s research on vibrating plates.

A lot of builders don’t bother with this stuff, but indirectly at some level they probably are. The poppy seeds land on the node points, and if you grab a piece a wood at that node point and bang on it you will hear a ringing “dooong.” I listen for the note to be musical, good sustain, no, distortion (usually indicates a crack) but the actual note as meaning too. That is what I am measuring in the pictures. I am showing 2 patterns in my pictures that give me some information that I use in setting up my target thicknesses for the tops (and backs.) The picture with the shorter lines going across the grain are given me information about the stiffness of the top along the grain. The one with the longer lines along the grain are more about the stiffness across the grain. The particular note (frequency) will vary on thickness, so it is important that the top be a uniform (known) thickness. The spectrum analysis (colorful chart picture) will align to the frequencies that I am finding with the poppy seeds. This sort of dynamic testing helps to “guide” me in some of the decisions I make with the bracing and thickness of the tops and backs.

Some luthiers do more of a static test where they will measure deflection with weights. This works well too but it works best when the plates have been (all) uniformly thicknessed. I experimented with that approach but ultimately found a process through the dynamic testing that works for me.

Once again, many don’t use this sort of approach and build very successful guitars. I am not saying my approach is better, only that it is better for me. It gives me real (empirical) data that I can use. When I tap on a top (and I do that a lot) I really listen carefully. However my memory for sound can fool me so I like having numbers and pictures to help me remember and visualize my process. There is a lot more to it, but hopefully that sheds some light on what I am up to.

WOW !! Thanks for that explanation. It helps demystify the process while simultaneously adding intrigue for those of us not in the know. Thanks again.

John

[John Osthoff]

I plan to take a few days off and hit the beach later this week (all work and no play makes Jack a dull boy) and then we will be back on these two next week. In the meantime here are a few more shots from the shop

First up is the sketch of the SD with the 12-fret neck/body join. That is just a rough idea with the pickgaurd just to see what it might look like.



Went with a thin rosette, it should work nicely with the burst



Here a few shots of the top getting put together, In this first shot the upper traverse brace (carbon reinforced) it precisely positioned using a little fixture on the go-bar deck



The soundhole patch prior to installation

[John Osthoff]

Here is shot showing the bridge plate core. It will get a thin veneer of maple laminated to it (providing the strength but not the weight) prior to being installed, so in this shot it is just there to check positioning.

[John Osthoff]

The SD is coming along. I hope to have it "boxed up" today, but it might have to wait until after break.

Here are few shots of the (quilted mahogany) back getting ready for braces.



Here is the back on g0-bar deck getting the radial braces

[iim7V7IM7]

What is the concept behind moving from a traditional ladder bracing scheme in the lower bout to a radial array of braces? Also, what radius top and back dishes are you using? There appears to be a significant arch in your go-bar deck shot.

Always curious about the "why's"...

[John Osthoff]

Originally Posted by iim7V7IM7

What is the concept behind moving from a traditional ladder bracing scheme in the lower bout to a radial array of braces?

Hi Bob,

This bracing pattern is based on "some of" the stuff Trevor Gore is doing. As a matter of fact the bracing pattern is very similar to his. The main reason I am doing this type of pattern is to get the back a little more involved with what I call coloring the sound by making the back a little more active. Some go with the more reflective approach. The cool thing about this design is the back is tunable in such a way of the main resonance gets in the way by robbing energy it can be adjusted (shifted down) by removing wood from the lower bout's cross brace. This can be accomplished on ladder braced backs too, it just is little more difficult to predict where to remove wood.

Originally Posted by iim7V7IM7

Also, what radius top and back dishes are you using? There appears to be a significant arch in your go-bar deck shot.

I use a 30' foot on the top (sort of.) Actually I try to keep the area in the upper bout on the top flat, so the 30' radius is mostly below the soundhole.

The back is 10' radius.

Originally Posted by iim7V7IM7

Always curious about the "why's"...

Ah a man after my own heart.

[John Osthoff]

I missed taking many photos of the FS in process that I am making for the Woodstock show. I snapped a couple the other day.








The neck blank was something I put together today, it will get cleaned up next week. ... you can see the SD body in the background.

[iim7V7IM7]

Interesting landscaping to the back. How does Higuerilla stack up density/stiffness wise to some hardwoods that we might know?