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Thread: Fitting neck on Stewmac F5 kit

  1. #1
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    Default Fitting neck on Stewmac F5 kit

    Hello. I’m building my first mandolin with Stewmac’s F5 kit, using the video created by Don McRostie. I thought I followed Don’s instructions carefully in measuring neck fit. I also used the Siminoff jig that’s often been suggested to measure height at the bridge and came up with 5/8” there. Neck angle is about 6 degrees.
    Now that I’m farther along in the build, and after reading several posts about neck fit problems on the forum, I think my neck fit is wrong. With the neck pushed firmly into the dovetail joint, the overstand on my build is slightly below the top at the neck joint (about 1/16”). Click image for larger version. 

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    I can’t raise the neck in the dovetail joint without creating a gap where the heel meets the back, and would prefer to not have to glue in a heel extension, as I understand that has to be a strong joint. If I attach the finger board in the current position, it would barely clear the top at the extension block and would leave almost no room for the finger board extension support. I’m wondering if it would make sense to add a piece of veneer or other thin layer of wood under the finger board (it’s not glued on yet) to raise the overstand and cover the seam with binding. I would probably then have to reshape the entire neck to make up for the added thickness.
    I’d appreciate any other thoughts or suggestions. Thanks for your help!

  2. #2
    Registered User sunburst's Avatar
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    Default Re: Fitting neck on Stewmac F5 kit

    As I see it you have two good choices (and probably other not-so-good choices).
    1. Glue an extender piece to the heel (what you said you didn't want to do).
    2. New neck.

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  4. #3

    Default Re: Fitting neck on Stewmac F5 kit

    agreed with JOhn if the neck is not glued in yet.... pull it out ..... cut a small piece of maple on the band saw and glue it to the heel of the neck.... reshape the heel with a dremel or what ever tools you have. You will have to shim the neck as i suppose it will be loose after the extension is added...

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    Default Re: Fitting neck on Stewmac F5 kit

    Quote Originally Posted by sunburst View Post
    As I see it you have two good choices (and probably other not-so-good choices).
    1. Glue an extender piece to the heel (what you said you didn't want to do).
    Thanks for your response, Sunburst.

    If I glue an extension on the heel, how much does that compromise the strength of the dovetail joint? Is there a way to reinforce the glued extension (dowel, screw?) before gluing on the neck?

    Should the overstand end up being a minimum 1/4” above the top at the neck joint?
    Last edited by MikeEdgerton; Jan-16-2022 at 10:27pm. Reason: Fixed quote syntax

  7. #5
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    Default Re: Fitting neck on Stewmac F5 kit

    There are hundreds of thousands of old Martin guitars with shimmed dovetail joints. Those joints are very strong as long as the fit is snug.
    Last edited by rcc56; Jan-16-2022 at 10:49pm.

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  9. #6
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    Default Re: Fitting neck on Stewmac F5 kit

    Quote Originally Posted by kymando View Post
    Thanks for your response, Sunburst.

    If I glue an extension on the heel, how much does that compromise the strength of the dovetail joint? Is there a way to reinforce the glued extension (dowel, screw?) before gluing on the neck?

    Should the overstand end up being a minimum 1/4” above the top at the neck joint?
    If you make a good joint and glue it with high quality glue (I'd use hot hide glue of course) there is no strength compromise in the short term, meaning beyond our lifetimes. It might fail in 200 years, but I don't expect to have to fix it if it does! No need for a dowel or anything else, and in fact a dowel would weaken the joint because we sacrifice side grain gluing surface when we drill for a dowel.

    BTW, "stacked" neck heels are very common in classical guitars and somewhat less common in steel string guitars. They hold up just fine.

    I like 1/4" for the overstand, but it is not a magic number. Higher is OK within reason, but much lower can cause problems for the player and for the luthier working on the fingerboard and frets of an F (scroll bearing) mandolin.

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  11. #7
    Adrian Minarovic
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    Default Re: Fitting neck on Stewmac F5 kit

    Looks like you did the neck fitting without the riser block glued on.
    I agree with John. I'd glue piece of new maple on the heel and shape it.
    You need to create PERFECT tight joint and use strong glue that doesn't creep under tension. Hot hide glue would be one of the best choices (you can use edible gelatin- knox, instead if you don't have hide glue). Titebond is good glue overall but this is area under large stress and the stacked heel may creep slightly cracking finish at the glue line. In hot conditions it may even open.

    My preference is approximately 1/2" tall riser block at the crosspiece (from ribs to highest point). This lifts the fingerboard gluing surface a bit above the body scroll so you can safely plane it without hitting the top.

    edit: I now see that you already glued the trussrod with the barrel nut flush with top of the neck surface. You should be careful to set the neck exactly as you won't be able to plane away any wood from the surface to do some final adjustment after neck is glued in.
    Adrian

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    Default Re: Fitting neck on Stewmac F5 kit

    Thanks to all for your advice. Looks like I’ll need to find some scrap maple and make my first attempt at using hot hide glue.

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    Default Re: Fitting neck on Stewmac F5 kit

    Making the neck heel extension is proving to be more challenging than I expected. I’m assuming the extension piece will need a dovetail, correct? Cutting that precisely has been difficult for me, and getting the surfaces of the heel and extension to mate on a flat plane has also been a challenge. Any advice on how to get the heel surface perfectly flat?

  15. #10
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    Default Re: Fitting neck on Stewmac F5 kit

    If you are adept with a block plane you can get a true flat surface, but you first must be adept at sharpening and setting up a plane.
    If you can come up with some sort of holder/jig for the neck that allows the heel to contact a true flat surface at a constant fixed angle you can stroke the piece on a piece of 120 grit sandpaper and achieve a flat surface. I sometimes do that sort of thing on my table saw or jointer table. It can be a simple as a cam clamp on the neck or as elaborate as you want to spend the time to make it. The exact angle is not important as long as the final surface is dead flat.
    Another possibility is use carbon paper (old enough to remember what that is?) or chalk to fit the pieces by scraping. Where there is contact carbon or chalk will transfer when pressed between the pieces. Scrape away wood where contact shows, press together again, scrape, repeat until there is contact everywhere.
    Easiest thing to do for the extension piece is to cut it from a piece of wood with an existing flat surface. It doesn't mater how big the piece is as long as it is oversized. Glue it on and then shape the neck heel.

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  17. #11
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    Default Re: Fitting neck on Stewmac F5 kit

    Thanks, John. I appreciate your help. Nearly every post I’ve read on this forum has a thoughtful, often long and detailed, response by you. Makes me wonder how you find time to build and repair instruments!

    I was able to get a very flat surface on the neck heel by clamping the neck, finger board side down, to a perfectly level table. I then used 120 grit sandpaper attached to a flat board that I moved slowly over the heel while holding a level on top of the sanding board and keeping the bubble in the level centered. Worked like a charm. I did cut an oversized extension piece from a flat board, as you suggest, so it should mate well when glued.

    When playing around with shims in the dovetail I noticed that there is a crack in one of the “wings” in the riser block. I must have exerted too much lateral pressure in the joint at some point. I believe I read in another post that this isn’t a structural element; that the strength of the joint is in the head block. True?

  18. #12
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    Default Re: Fitting neck on Stewmac F5 kit

    There is a certain amount of structure at the riser block. It is under sheer force when string tension is present and also any lateral force that might be exerted on the neck joint. It should be well glued with a glue that resists creep (once again, hot hide glue is a good choice). Much the same can be said for the fingerboard extender piece glued to the top. When all of these elements, along with the neck joint itself, are well chosen, well fit and well glued, the structure of the neck joint is the best we can do.

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