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Neck fit problems (newbie needs help!)
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10101&t=18184		 Page 1 of 1
Author:  ms960 [ Wed Jul 30, 2008 7:17 pm ]
Post subject:  Neck fit problems (newbie needs help!)
Run-of-the-mill newbie here -- this is my third guitar. Things were going great until I attempted to dry-fit the neck (it's a bolt-on) to get an idea of the bridge position so I could tape off and finish the top.

Basically, the neck angle and top of the guitar got royally messed up. If the neck is flush against the side of the guitar, there is a gap under the entire fretboard extension, with it being about 1/8" at the end of the fretboard. Even at the neck joint there is a small gap, maybe 1/32".

Image showing how severe the problem is:
Image

A couple shots showing how nice this guitar was beginning to look, until now :( .
Image
Image



Not sure where to go from here, but would appreciate thoughts before I take a saw/file/sandpaper/grinder/sledge hammer to this problem and give up the hobby.

Thanks everyone!
Mark
Author:  bluescreek [ Wed Jul 30, 2008 7:25 pm ]
Post subject:  Re: Neck fit problems (newbie needs help!)
it is rare the a neck just "bolts" on. There are more times than not some neck adjustment needed. I think you didn't take into consideration the neck angle in the beginning. http://bluescreekguitars.com/blog this link is one of many ways of doing this. I don't think your guitar is at its end. Adjust the neck angle to set the geometry and you will have a nice guitar. no need to give up on this one
john hall
blues creek guitars
Author:  Hesh [ Wed Jul 30, 2008 7:28 pm ]
Post subject:  Re: Neck fit problems (newbie needs help!)
Mark buddy in addition to John's info here is a tutorial for fitting a neck.

http://www.luthiersforum.com/forum/viewtopic.php?f=10102&t=15022%22
Author:  ms960 [ Wed Jul 30, 2008 7:45 pm ]
Post subject:  Re: Neck fit problems (newbie needs help!)
Hesh wrote:
Mark buddy in addition to John's info here is a tutorial for fitting a neck.

http://www.luthiersforum.com/forum/viewtopic.php?f=10102&t=15022%22


Hesh,

Very nice tutorial -- thanks for sharing that with me. It gives me some ideas on how to fix my problem. The biggest problem I face, I think, is that the top of the guitar (soundboard) is not flat at the neck joint. Instead, it curves downward, so even if I get the neck joint right, the fretboard extension won't lie flat on the top of the guitar. Is that something I should be least concerned about right now?
Author:  Hesh [ Wed Jul 30, 2008 8:01 pm ]
Post subject:  Re: Neck fit problems (newbie needs help!)
Mark glad that this helps.

Many builders will build a guitar so that the fret board drops off approx. .010 - .020 from where the neck meets to body to the last fret. I do this as well.

There are a number of ways to build in a good fit of the fret board extension with the top. Some folks do not radius the upper transverse brace or don't radius it in the middle.

In any event sometimes truing up the upper bout, so long as you don't make the top to thin there, will help the fit of the fret board extension. And combining this with a proper neck angle and the fret board extension drop off mentioned above and Bob's your uncle.... :D

Here is an easy way to true up the upper bout. http://luthiersforum.3element.com/forum/forum_posts.asp?TID=10344%20&KW=(pics)#forumTop%22
Author:  ms960 [ Wed Jul 30, 2008 8:32 pm ]
Post subject:  Re: Neck fit problems (newbie needs help!)
Hesh wrote:
Mark glad that this helps.

Many builders will build a guitar so that the fret board drops off approx. .010 - .020 from where the neck meets to body to the last fret. I do this as well.

There are a number of ways to build in a good fit of the fret board extension with the top. Some folks do not radius the upper transverse brace or don't radius it in the middle.

In any event sometimes truing up the upper bout, so long as you don't make the top to thin there, will help the fit of the fret board extension. And combining this with a proper neck angle and the fret board extension drop off mentioned above and Bob's your uncle.... :D

Here is an easy way to true up the upper bout. http://luthiersforum.3element.com/forum/forum_posts.asp?TID=10344%20&KW=(pics)#forumTop%22



Hesh -- again, thanks very much. I'll put the neck back on (dry-fit) and see if I can't use that technique to flatten out the upper bout to remove the "dome" i've built into the guitar there.

Mark
Author:  Hesh [ Wed Jul 30, 2008 8:38 pm ]
Post subject:  Re: Neck fit problems (newbie needs help!)
Mark buddy any time.

It would be a good idea to get the neck fitted and the angle of the neck set in relation to the bridge before you true the upper bout. It's also a good idea to sand the bridge bottom over the guitar top sanding in the radius of your top to the exact bridge that you will use. Often when sanding the radius into the bridge the bridge gets a tad shorter and you need this reference point to set the neck angle correctly.

So there is a sequence here and then it all comes together nicely.
Author:  Pat Foster [ Wed Jul 30, 2008 9:19 pm ]
Post subject:  Re: Neck fit problems (newbie needs help!)
Mark,

Good to see you back here again. Nice-lookin' guit, too!

Do you know how the dip in the top came to be? That might be a structural issue that might need to be taken care of, depending on its cause.

If you go with the top as it is:

As Hesh and John said, get the neck angle right with respect to the top of the bridge. That is paramount; if you base the neck angle on how the fb extension sits, you'll have an unplayable guitar. After the neck angle is right, you'll have to look at the gap under the fb extension and decide whether sanding out the top will take care of it. Looks like you'll have more than what you can take care of by sanding the top, even if you have 10 or 20 thou of drop-off. You might need to just get the dome out of the top under the fb extension and use a tapered shim. Wouldn't show too much, as it looks like the fb is ebony, though the taper surely will. If you're keeping this one, you could just live with that. Otherwise, the dip in the top really must be addressed.

Good luck, keep us posted,

Pat
Author:  Jody [ Thu Jul 31, 2008 4:57 am ]
Post subject:  Re: Neck fit problems (newbie needs help!)
it might be a photo illusion , but it looks like your fingerboard has a slight upward bow to it , increasing the gap , Jody
Author:  jackatwork [ Thu Jul 31, 2008 7:06 am ]
Post subject:  Re: Neck fit problems (newbie needs help!)
From what I see in your picture, it looks to me that the neck isn't in good contact with the body;Maybe at the heel, yes, but not at the fingerboard/neck ; looks to me as if you may have too much 'set' in the neck
Author:  ms960 [ Thu Jul 31, 2008 7:28 pm ]
Post subject:  Re: Neck fit problems (newbie needs help!)
All,

Here are two more pictures showing the issue:

Image


Image


The first picture shows how much I have to shim the heel of the neck to get the fretboard to align properly with the bridge. I have to shim about .165" (more than 1/8" inch!). The picture isn't great, but when I have it shimmed as shown, no part of the fretboard rests on the top of the guitar. Looks like I will have to shim under the fretboard to get this looking decent. Yes, I am keeping this one, so I can live with a shim here and there if I need to. I just want it to be playable (my second build wasn't playable, so my frustration is pretty high).

The second picture shows the dome (at least attempts to show it). I have not sanded the top at all, other than some rough sanding, but no final or aggressive sanding has been done. Would it be possible to try to sand down the dome in an attempt to flatten the upper bout in this area?



Hesh -- Again, thanks for your comments and help. I am hoping I can find the correct sequence for *this* problem :).


Pat -- No, I don't know what caused the domed shape in the top at the upper bout. I was taking this build very slowly and deliberate so as to avoid some of the really dumb mistakes I made in my first two builds. Ironically, this mistake is a new one -- go figure.


Jody -- the fretboard is indeed flat. What you thought might be an upward bend is probably just a function of the poor photograph.


Todd -- The top is convex in the upper bout. No, I did not over-sand the top. The neck angle is correct in the first photo of this post.


Jack -- You are right, the neck isn't in good contact with the body in the photo in my first post. I have a lot of work to do to get it right, obviously.

Again, I very much appreciate all your thoughts and assistance. I don't want this guitar to become a canoe paddle, but it may end up becoming one regardless. There is a semi-professional luthier in the area, but he is sooo busy it is impossible to get on his schedule. Ideally I'd love to take it by him and get his thoughts/help, but I have a feeling I'm on my own here.

Cheers,
Mark
Author:  Hesh [ Thu Jul 31, 2008 7:53 pm ]
Post subject:  Re: Neck fit problems (newbie needs help!)
Mark buddy this is can be fixed and again it is simply a matter of fitting the neck to the guitar body.

I am wondering, in the first picture it shows the neck, forget the fret board, coming in above the body. To properly check the neck angle the neck needs to be bolted on flush with the top of the guitar. Next add in the fret board height and the fret height and see where it comes in over, or under, the bridge.

What I am seeing here simply needs to have some material removed from the top of the neck cheeks and not from the heel area. This will reduce the neck angle. Granted 1/8" is a lot of material but it can be done. Also, the top of the neck tenon will probably elongate.... and may hit the bottom of the mortise. If this happens you can remove material from the neck tenon and/or route the mortise deeper in the area that it hits.

If my hunch is correct and you lower the neck to be flush with the body, bolt it on, and use a straight edge shimmed to the height of the fret board ONLY over the neck and not the body (this means not using the fret board) I suspect that your neck angle will not need as much material removed as what we see in your picture. Be sure to locate the bridge correctly too.
Author:  Mike Mahar [ Fri Aug 01, 2008 7:55 am ]
Post subject:  Re: Neck fit problems (newbie needs help!)
I've had my first dry fit be just about as "off" as yours is. You have three separate problems and you will have to deal with them separately.

I looks like your neck bolts on too high up. Are you using threaded inserts? If so, you can plug and redrill the holes in the neck block so that fret board is in contact with the top. I've done this several different ways. Dowels don't work as well as you might expect because the softness of the wood is different from the dowel and the neck block. The drill will drift when you re-drill. I have found that epoxy putty works really well. I use the gray stuff from the hardware store. Mix it up and roll it into a snake that just fits in the existing hole. Tamp it in with a end of a drill bit. Don't worry about it squeezing out of the ends. Just scrape it flush and sand is once it is hard.

Then set the neck angle using Hesh's technique. I'd do this before re-drilling the bolt holes. Once you have that correct, make a couple of centering points. You do this by taking a bolt that fits into the inserts in the neck. Hack saw off the head of the bolt and chuck it into a drill or drill press. Spin up the drill. Take a file and file the end into a point. Cut off the point so that there are enough threads to screw the point into your insert and have just the point sticking out. Make two of these. Once the two centering points are in the neck, place the neck into position on the guitar body and push the neck into body. This will leave two indentations in the body and that is where your new bolt holes will go.

Since you have changed the angle of the neck you have to make sure that the new bolt holes are on a line with the inserts. Screw in the bolts with the neck off the guitar. Notice the angle of the bolts in relation to the neck cheeks. Make sure your holes are drilled at the same angle.

If you are using barrel bolts, use the epoxy putty to fill the barrel and bolt holes and re-drill to the new position. In this case you can use standard dowel centers placed in the neck block to make the new position for the bolt holes in the neck.

Make your bolt holes on 1/32" larger than your bolts. It will make your life a lot easier when you do your final fit and the slop won't matter once the bolts are tightened..
Author:  Rod True [ Fri Aug 01, 2008 10:55 am ]
Post subject:  Re: Neck fit problems (newbie needs help!)
I know this doesn't necessarily help in this situation but this is why I always set the neck before I glue the fret board on. It's always easier to fit the neck with the fret board off versus on.

Anyway, as has been mentioned, you'll have to first make sure that the tenon isn't holding the neck up from being aligned to the plane of the body.

After you ensure that the tenon isn't interfering at all, decide if you want to flatten the upper bout of the sound board from the sound hole to the front of the body (I'd recommend it). There are several ways to do this which have been mentioned already.

Once the upper bout of the sound board is flattened, start working on your neck set. You want the set of the neck to be done based on the height of your bridge, not the other way around (which some early builds end up being).

Laying out the "tapper" of the upper bout of the sound board is one thing that I did in CAD which really helped me to see how the geometry of the neck set worked. All this was based on the bridge height I wanted to use (11/32"). Setting the neck is based on this for me. With the fret board on the neck with frets installed, I want to see a gap of 3/32" above the bridge. This allows for the top to pull up and allow for about 1/8" of saddle height above the bridge once the guitar is set up.
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