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Thread: neck block design

  1. #1

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    I have designed a symetrical two point mando. I wondered about incorporating the point blocks into the neck block. I saw it done this way on a Regal Octophone, and wondered if it would work on a standard mandolin. Should I be concerned about grain direction, weight, stability,.....? Just didn't see much reason to stick a piece of kerfing 1" long between the neck block and point blocks. Here's a poor drawing of my idea.
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  2. #2

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    I think that's pretty close to what Phoenix does.

  3. #3
    Registered User sunburst's Avatar
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    Gibson did that on some of their two-points back in the dark days. That's a mighty wide cross-grain glue joint. The Gibsons I've worked on, with that type block, had alignment problems at the points, and elsewhere, caused by differential wood movement. The glue joints were evidently suffering, and I would suspect possible future glue joint failure. I think you would be better off, structurally, with separate blocks, and 1" pieces of lining.

    If, on the other hand, you were to run the grain in the block the same direction as the top and back, things could move around without causing as much sheer stress on the glue joints. I still think I would prefer separate blocks.

    BTW, Rolf uses a similar block in the Phoenix mandolins, made of Willow.

    Yes, you should be concerned about weight, stability, and grain direction. Actually, stability and resistance to splitting are the main concerns, in my opinion. All of the head block failures I've seen were splits, usually from the corner of the dovetail, so, the wood should be chosen for resistance to splitting and ease of cutting for the dovetail, and the grain direction should be chosen to minimize the chance of splitting.

    Some people laminate their head blocks. That really helps with stability and resistance to splitting, though somewhat at the expence of ease of machining.
    In this case, I think a one piece, laminated block would be too stable. In other words, it would be about the same as a cross grain glue joint, and may cause the same sheer problems that I mentioned above.

  4. #4

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    I was thinking of a laminate sandwich of mahogany, baltic birch plywood then another layer of mahogany. It isn't a big deal, but I thought I could machine the one piece block on my router table with a template.

  5. #5
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    I'd lean towards a laminated block as well.

    Ron
    My wife says I don't pay enough attention to what she says....
    (Or something like that...)

  6. #6
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    I did this one with 3 laminated pieces of wood for the neck block.
    Bill
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  7. #7
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    I'd go with a neck block and point blocks. Both for weight and expansion/contraction issues. My $.02.

  8. #8

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    Vega cylinderbacks are one piece - and, it transpires, don't have rib skins covering the neck block from joint to point.

    My assymetrical ridgeback used a 3 ply mahogany one piece block.



    Not too pretty, but it works and just you wait for the next one

    Steve

  9. #9

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    Thanks for the feedback guys. I never would have thought that expansion and contraction, especially with a laminated block, would be an issue. I'd rather be safe than sorry, so I'll go with seperate points and blocks. Isn't that an issue with the F5 design? Is that what is accounting for the scroll crack being discussed in the F2 thread?

  10. #10
    Registered User sunburst's Avatar
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    Quote Originally Posted by (thistle3585 @ April 12 2006, 10:04)
    Is that what is accounting for the scroll crack being discussed in the F2 thread?
    That's usually the main culprit in cracks like in the F2.

  11. #11

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    Hi All,

    What materials can I use for the neck block? Is ANY seasoned hardwood suitable?
    I have a couple of nice old oak blocks which, dimentionally are spot on for this
    purose - is there any reason that I shouldn't use well seasoned oak?

    BR
    Al.
    "The man who never made a mistake, never made anything at all"

  12. #12
    Registered User sunburst's Avatar
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    There's no reason why you can't use Oak.
    A couple of reason why you might not want to are: it's very heavy, and it's very hard and not easy to cut to shape and cut for a neck joint.

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