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Hi all,

Relative beginner here building a couple of l00 s. I've Attatched the backs then sanded the top side of the rims flat with a sanding stick and then used a stone slab which is pretty flat with sandpaper and a 6mm shim at the tail end to create the flat upper bout/ fingerboard extension area.

One had worked greatt,, a straightedge to the saddle point shows 3-4 mm clearance. Unfortunately on the other one it doesn't even give a mm. I can't sand any more from the neck end as the lining will end up too shallow so I'm guessing at this point I need to remove height from the rims in the lower bout area.any suggestions?

Thanks,,,

Mike

Get the frame geometry correct and redo the linings. Better to sacrifice the linings than wreck the sides by chipping away at this end then that end then this end then that end etc...

Flattening The Upper Bout: http://www.luthiersforum.com/forum/viewtopic.php?f=10117&t=25931

From my read of what you said that you did your shim is twice, roughly what I use. Perhaps the link above will be helpful to you.

That's more or less what I did.no joy with 3mm shim so tried six. Does sanding the rim flat instead of using the top radius cause a problem?

Did you check the angle you have on the top of the neck block? Should be about 91.3 degrees -- sounds to me like you have the neck block tilted forward a little and it is not perpendicular to the sound board edge of the rim.

_________________
Ken Cierp

http://www.kennethmichaelguitars.com/

Thanks all. outside of the neck block to soundboard angle a fraction over ninety degrees. Attatched pic of a straight edge with a 6mm Rise at the tail block showing about a mm clear at the bridge . Very tempted at this point to plane a little of the lower bout until the angle is good and then replace linings if they're not deep enough as suggested.. Any thoughts?

Hopefully this is the picture.

Seems to me that you are mixing a bunch of different processes/methodologies and perhaps picking off or looking for popular theoretical dimensions. Seems like the fact is (a bit over 90 degrees you mention neck block and upper bout) is not going to launch the finger board plane to the height you need to clear the bridge. A better check of your upper bout slope can be made by simply laying the rim on a flat surface -- when holding the lower bout down against the table/bench there should be a taper from the waist curve to the neck block -- and a gap at the neck block of about .065" BTW this is another reason I recommend gluing the sound board to the rim before the back plate -- the tension of the contoured back can at times distort the rim (could have happened here)

_________________
Ken Cierp

http://www.kennethmichaelguitars.com/

I think you're probably right about mixing methods but I really want to understand and be able to visualise what is going on here. I adjusted the way the body is in the mould. Flattened the lower bout again and sanded the upper until the witness lines. With the flat plate resting on the lower bout I have 3.7mm under the neck block but only about 1.8mm clearance at the bridge point. Getting frustrated now and may glue as is and sand the upper bout of the soundboard a little but I really want to master and understand this partof the process.

Mike sorry that I can't be more helpful either but I felt the same way as Ken that you are mixing multiple different methods, some that I don't understand or subscribe to, and as such I have no idea where things are now for you....

I can tell you that the method that I use, which is also what Martin does, has dependencies on certain steps at certain times. Get things out of order or employ other methods and all bets are off with the method that I use.

As such I'm of the impression that in order to help you we all need to hit the reset button, get some clear pics and descriptions of exactly where things are now and go from there.

PS: Back in the day on the OLF Somogyi was often the subject of our discussions and his penchant for uber thin tops sometimes only .065" thick and on a dr*ad too. For some years after that everyone including me was looking to thin our tops as much as possible but some of us did not understand that Somogyi's build style has dependencies on other things that can make that uber thin top work and not crack all to heck.... Double sides and a super stiff rim were/are a prerequisite for going as thin as Somogyi as well but some of us would pick and choose just the thin top part and neglect to do the other things that made this work for Ervin. Some of us also had failures too because we neglected to understand that it's often the case that a build style is very much a build system with interdependencies.

Guitar geometry is very much like this or more specifically getting the neck angle correct and the transition of the fret board extension to lay flat, have perfect contact, and in my case have built-in fall-away as well.

I'm sure that everyone wants to help, I most certain do, but sadly I'm lost now and based on Ken's comment I suspect that he is too. So to proceed at least some of us, probably the geezers like me, need a reset and more information about exactly what you have now.

Thanks!

Right ok.sorry my explanations aren't clear. I followed your tutorial Hesh with a 3mm shim but I couldn't get enough clearance so I increased the shim. I also didn't radius the top, just sanded flat with a sanding stick. I'll try to Attatch some more useful photos.Thanks for bearing with me.

Neck block angle

Flat surface resting on the lower bout.

Box in the mould and the Stone plate with sandpaper amd shims used to sand the flat area.

Not the best pictures but hopefully clearer.

On a related note, I simply use a flat upper transverse brace. What are the pro's and con's that the collective here can see?

I think the pro's are that I have a flat upper bout and don't have to worry about all this. I'm not sure what the con's may be.

The UTB on mine is flat as well, the aim is top have the fb extension in alignment with the rest of the fb. As I understand .... which may not be very far.

Just to clarify, I attached the back which you don't do in your tutorial Hesh but i've tried it without and the rims vibrated all over the place when sanding, the spreaders on your pictures look rather more effective than mine. I've put some wedges under the neck block so that the upper edge of the rim is parallel with the top of the mould in an effort to keep the neck and tail blocks perpendicular to the soudboard.

Thanks Mike for the pics, much appreciated! I wanted to address James's question first and then I'll get to you.

James there seems to be three ways to approach the UTB question.

1) Flat, that's what I did and do still at times but not always.

2) Very slight radius which should be a bit stronger because of the radius. I've been using 55' lately on mine and no problems beyond a bit less fall away than the .010" - .015" that I like to see.

3) Hybrid slight radius with the middle of the brace where the fret board extension lays made flat.

Note: I also use CF in my UTB so flat stays that way....

All three approaches work fine or can be made to work fine IMO.

Mike I have to take this step by step to not get mixed up. So let's not talk about the linings at the moment and instead simply concentrate on how to flatten the upper bout.

I radius my tops currently to 25' so the top is built and braced in a 25' radius dish. I install all of my braces except the UTB in the dish. The upper transverse brace when I use a flat one is glued on with a flat board backer and is the last brace that I glue.

It's easier once the rim is done with the blocks glued in place and before the linings are installed to radius the top (and back) in the dish without linings. Reason being we are not sanding though the linings now either and when we do install the linings they remain very close to full height.

So the top is radiused except for where the UTB goes and the rim is radiused (I use 15' for the back, 25' for the top) in the dish.

After I have the rim completely radiused I install the linings and I install them about 1/32" proud of the rim so that the radius can be imparted to them in the dish without needing to take material off of the sides.

Next with the linings installed the rim goes back in the two respective dishes and is reradiused imparting the radius to the linings this time.

Now this is where I flatten the upper bout with the shim size listed in my toot (I'm at work slacking off right now so I can't see what I said in my toot about the size). This time it's a flat board with sandpaper on it, top side down, shim under the tail block, and pencil marks from the waist to the neck block sanding until all marks are gone.

That's it. Nothing more to it and I've never had any issues doing it this way. I prefer this method over flattening the top with sanding because I don't want to make the top too thin in that region.

Setting the neck angle is next once the back and top are in place.

Maybe you can let us know where you are in the process and we can go from there?

Thanks!

ok.

X, tone bars and finger braces radiused and glued in dish. 25 foot radius. Two UTB braces, as its a 12 fret joint l-00, both flat and glued flat.

Back braced standard fashion in a 15' dish.

Neck and tail blocks glued in. Back linings glued proud, top linings flush.

Back linings radiused using a 15' radius stick, back glued on.

Flipped over, shim under the headblock to even out the taper and sanded the top rim using a flat sanding stick.

I then used my large stone tile glued with sandpaper and 3mm shim at the tailblock end to flatten the upper bout.

Then cut the pockets for the upper X and two UTBs and held the soundboard in place with elastic bands as pictured. Checked the angle with a straight edge from the upper bout to the bridge position. No joy. Messed about with it for a bit, sanded it some more, possibly made a mess.

Decided i needed a steeper angle to get the clearance at the bridge point so doubled the shim. Same sanding process, still no joy. Checked the fit in the mould and made new witness lines and re-sanded. The linings are getting pretty thin at the neck block end but i think it's just enough at the moment.

I've got two others on the go which have worked fine but i did those in solid moulds with the backs on a radius dish which i think, with this technique, may have been more effective. I used my mould from Ken for this one because i changed the shape slightly so used the adjustable mould.

Really appreciate the help and advice on this forum.

thanks,

Mike

Mike my friend this is where I got lost. You flipped it over, meaning top side down? Where I'm lost is the shim under the head block, did you mean tail block?

Also just have to clear the air because this one has come up before: Folks think that this method will permit a neck to be attached and called good. Necks always have to be fitted for better or worse. This method gets things close IME but you still have to fit the neck. So when you say that you "needed a steeper angle at the bridge this is where we fit the neck and change the neck angle to fit the top of the guitar, not change the top geometry to fit the neck. Just want to make sure that you understand this because it has confused folks before.

Back side down and a couple of inch or so blocks under the neck block to make the top rim parallel to the top of the mould.

Like this.

So what is the angle machined on the heel cheeks of the the neck you plan to use. To Hesh's point, one size (measurement) does not fit all, the goal is to get mating surfaces that produce a straight line (some add a bit of fall off) I am still a little mystified as to what you are trying to accomplish. (measurements taking with the top rubber banded to the rim I believe have no value). What have you done that has made the ribbon linings so short? I believe the process Hesh describes normally removes about a 1/16" -- 2mm at the neck block.

Here's a refresher of the neck angle finger board plane concept -- its not the process that's important (many methods work) but rather understanding the geometry, particularly with the guitar you are working on.

http://www.kennethmichaelguitars.com/neckangle.html

_________________
Ken Cierp

http://www.kennethmichaelguitars.com/

Hesh, your confusion is that he is putting the sanding dish on top of the body to sand rather than the body upside down in the dish. It took me a while to figure that out too.

_________________
Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.