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 Post subject: Fretboard Fall off
PostPosted: Sun Jun 03, 2018 3:07 am 
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Joined: Fri Mar 04, 2016 10:30 pm
Posts: 35
Hi All,

I am just in the midst of building my 3rd guitar and have ran into something that I haven't seen on my first 2 builds. I shaped the rims exactly as how John Hall shows on the YouTube video "prepping the rims".

For some reason I ended up with quite a lot of fall off on the fretboard extension. I have flat sanded the plane of the neck as far as I feel comfortable with. The guitar does not have a cutaway so playing this part of the guitar is not likely. So would you advise to shim it? Also I would be interested how some of you shape the rims so you get good geometry of the neck. The only difference on this build was I screwed the neck block into the mold to hold it true. I didnt do that on my first 2 builds and i might have just got lucky, not sure.

I'll try and post a picture of the fall off shortly.

Thanks in advance.

Curtis


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 Post subject: Re: Fretboard Fall off
PostPosted: Sun Jun 03, 2018 6:19 am 
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Joined: Sun Mar 09, 2014 8:13 pm
Posts: 1644
Hi Curtis.

Photos are always helpful. The fall off shouldn't cause any problems, as long as it doesn't interfere with playability. so you're good to go as long as the board makes good contact and lays flat on the top. As far as shimming goes, you'll have to make a decision based on aesthetics. If you're happy with the appearance and its playable for you, then don't shim.

I use a radius dishes to shape the edges of the rims so that they match the radius of the top and back. If you don't want to invest in radius dishes, then you can make a radius stick, which can be attached to a central "pole", so it pivots. It doesn't need to be pretty. Maybe one of the folks here on the forum will help you with ideas on building them.


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 Post subject: Re: Fretboard Fall off
PostPosted: Sun Jun 03, 2018 6:25 am 
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Joined: Fri Mar 03, 2006 7:09 pm
Posts: 5721
Location: Hegins, Pa
did you radius the entire top? I only radius from the top of the sound hole to the neck block? I use 28 ft dish
and wen you set the neck you adjust this plane by sanding it true.
You only need about 1/4 to 3/8 in rise so when you set the rim top down and push on the neck block that is all the tail block should rise. Your target number is 3/32 at the point of the saddle and without a top that is hard to measure but with the neck angle ramp established you should see this when you check it on a table top.
ask all the questions you need we are here to help
https://www.youtube.com/results?search_ ... s+addendum

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John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
Board of Directors of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com


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 Post subject: Re: Fretboard Fall off
PostPosted: Sun Jun 03, 2018 6:49 am 
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Joined: Fri Mar 04, 2016 10:30 pm
Posts: 35
Thanks for the replies. The fall off measures about a 32nd of an Inch at the end of the fretboard extension. Diane it is just enough that I would see it so I may shim the fretboard with an ebony veneer that i have. Just to take the edge off a little, but glad to know it won't affect the playability and is more less cosmetic on a non cutaway guitar.

John I did the exact process that you show in your video. This was the first time that I screwed the neck block into the mold so I thought it would be perfect. I flat sanded the top side of the rims to start, perfectly flat and then measured from the neck end of the rim to where the start of the sound hole would be (approx 4 inches) and radiused the 28'dish down to there.

I could go farther with the neck plane sanding to try and true it up more but I did pearl in the top purfling and it has already gotten thin enough that I don't think bringing it down any more is a good idea.

I think this will be ok for this build but I would like to try and perfect this somewhat as this will be less forgiving on a cutaway where you have the option of playing this part of the fretboard.

After I radiused the top I clamped the neck block to the work table and I was smack between 1/4 and 3/8" off the tail block on the bottom of the rims.


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 Post subject: Re: Fretboard Fall off
PostPosted: Sun Jun 03, 2018 5:36 pm 
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Joined: Fri Mar 03, 2006 7:09 pm
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Location: Hegins, Pa
one question
what was the RH when you glued the top braces?

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Blues Creek Guitars Inc
Authorized CF Martin Repair Center
Board of Directors of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com


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 Post subject: Re: Fretboard Fall off
PostPosted: Sun Jun 03, 2018 6:11 pm 
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Joined: Fri Mar 04, 2016 10:30 pm
Posts: 35
Good question, I generally keep my work area at 50% RH if any fluctuation at all, it would have been to the low side maybe as low as 40%. This may be the reason you think?


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 Post subject: Re: Fretboard Fall off
PostPosted: Sun Jun 03, 2018 6:40 pm 
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Joined: Fri Mar 03, 2006 7:09 pm
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Location: Hegins, Pa
if you were at 50% and it is lower 40% not that may have a bit of fall off. Did you use the flat sanding block and true up the neck to the body?


What it the height of the strings off the top at the point in front of the bridge?

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John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
Board of Directors of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com


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 Post subject: Re: Fretboard Fall off
PostPosted: Sun Jun 03, 2018 8:10 pm 
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Down the flat plane of the neck I measure 3/32" off the top at the point of the bridge. The string height should be approx 1/2" off the top when I get the bridge on. That's where my other guitars ended up when they were strung up.

I did flat sand the neck plane to try and reduce the amount of fall off but I am a bit hesitant to take it down much further.

What is really odd is my other 2 guitars were pretty much right on using the same method. I call it the "flat / 28". for some reason this one turned out not as well. The only difference this time is this is a different mold, the first 2 were dreadnaughts and this one is an OM. The mold is good and square and I used your suggested method of screwing the neck block into the mold to hold it true during the building process.

Is the flat /28' method what you always use for your builds? Specifically the method that you show in the prepping the rims video on YouTube?


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 Post subject: Re: Fretboard Fall off
PostPosted: Sun Jun 03, 2018 9:27 pm 
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Joined: Fri Mar 03, 2006 7:09 pm
Posts: 5721
Location: Hegins, Pa
yes it is
then I use the board to true the fret plane off the neck to the top
I like to see about a .010 in drop off.

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John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
Board of Directors of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com


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 Post subject: Re: Fretboard Fall off
PostPosted: Mon Jun 04, 2018 7:12 pm 
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I fully radius the top of the ribs. If you draw the resulting geometry, you see that you end up needing a thin tapered shim under the fretboard extension.

I'm not sure why a lot of people seem to be so appalled by the idea of putting a shim in there. The professional luthier who taught me how to build guitars puts in a shim on his guitars. He's a graduate of Red Rocks and served an apprenticeship with Dana Bourgeois, so I assume there is a sizeable group of well-respected luthiers who consider it a valid thing to do.

Now. you can set up the geometry so you don't need a shim, and that's also an accepted way to build a guitar.

If you intended to build the guitar so it wouldn't need a shim, and you're discovering that it needs one, it's probably worth the time to figure out why. If you do end up needing a shim though...I wouldn't worry about it much.

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