Today I focused on getting the top and bottom carved out.
Unfortunately, things did not go quite as planned, but such is the way of life.
To start off with the good: I did carve the top, and it looks great. The odd geometry of the model that I used to carve the top seems to not be too bad. I was able to sand it smooth pretty easily.
The top mates well with the center, and the glue from yesterday set properly, so that crack is basically sealed. I did notice that the guitar centerblock was a bit too thick, so I took it to the CNC to surface it down some. This left the thickness of the top at ~1.35”, since the thickness of the top and bottom at their edges were ~0.4” total, and the total thickness of the guitar needed to be 1.75” from top edge to bottom edge.
I did notice today that setting up the top for the topside carve that it wouldn’t adhere to the glue when I was gluing it down to the machine bed. Further inspection made me realize that the top was cupping ever so slightly, so I had to apply body weight to actually get it to adhere.
Note this down? Because this becomes important later.
After machining the top, I didn’t want to make the same mistake of trying to chisel out the tabs, so I opted to hand cut them instead. I started with a coping saw, but got impatient and cut it out with the bandsaw. I accidentally nicked the top a little bit while I was adjusting, and almost had a heart attack. Luckily, the nick is minimal, and I will probably remove that material anyway making the binding channel, so not much is lost.
While the bottom side was being carved on the CNC, I spent some time smoothing out the top and planning the f-holes. Something about it didn’t seem right when I laid it out, so I chose to sleep on the thought. I might design my own f-holes to go on this guitar; may as well since I’ve mentally deviated from the original idea of the p93 styling.
So remember the note about the top bowing? As it turns out, the blank I was using for the bottom was bowing as well. This, however, was bowing enough that it actually overcame the adhesive; either I just didn’t press down hard enough when putting the piece down, or it just came undone due to the force. This actually caused an inconsistency in the thickness of the top: at its lowest, it is half if not less than the thickness it’s supposed to be.
Right: the bowed up side...
This creates a couple of issues:
- The finishing carve, which I didn’t do yet, will either not properly round off since it’s too low, or worse case, may mill right through the bottom since it’s bowing upwards.
- The thinness of the bottom might not leave me enough play room to sand and smooth.
- The acoustic integrity of the guitar might be compromised since it’s so thin in some regions.
This leaves me with two options:
- Make a new bottom
- Make do with this discrepancy
Judging by the delta in change—about 2mm over the width of 381mm, so > 0.005mm in height every 1mm along the width—I’m inclined to say I can make do with this top. Only tomorrow will really tell if I can make do with this top. If it ends up cutting through, I’ll need to find more figured maple to make the bottom. If I do end up using this top, it should be generally unnoticeable that there is a height difference in the first place; it’s such a gentle difference that probably won’t be felt unless you’re looking for it.
Tomorrow’s goals are to try and get this glued up. I don’t have any spool clamps, and I don’t really want to wait for the materials to make them, so I’ll have to make do with another idea. I’ll also need to buy some binding, and possibly some perfling. That’s for a later time.
That’s all for now. Hopefully I can right my wrongs tomorrow.