Correct neck projection height for a mandolin ?

[Paul Lupus]

I have the back off of an old Italian mandolin for restoration and know the neck needs re-setting. Will slip the back to correct the neck angle when I re-assemble it. Wondering about neck angle projection over the top.  I know that a straightedge sitting on the frets of a straight steel string guitar neck commonly just clears the top of a correctly sized bridge blank. Does anyone want to hazard a statement regarding the "projection" of a 6 1/2" scale, flat top mandolin neck ?
Not surprisingly, the original bridge is mangled and at best only a hint of it's former construction / size because of successive attempts to lower action.
Thanks

[Paul Hostetter]

I think you mean a 13" scale, which pretty normal for old world mandolins. I don't believe there's any way to approach it other than "shooting" the neck with the straightedge as you describe, and setting it for the desired action and bridge height. Make the bridge first. Make it a little tall, to allow some room for adjustment later. Remember the strings can't lay on the fingerboard—you have to allow for some height in action above the frets during the dry run, but once you clamp your straightedge item to the neck, you can experiment a bit before glue-up and it'll all make sense. You can even leave the straightedge in place during the gluing procedure. Be careful that the neck doesn't shift side to side, otherwise the strings will be too close (or past!) one edge or another of the board when it's finally strung up.

[Paul Lupus]

Thanks Paul, this sounds very reasonable. BTW, in your experience, is this bone saddle perched atop the bridge original / appropriate ? Also, since it appears I have some leeway, any ideas on best height-thickness for a small ebony bridge like this, to best encourage resonance ? Lastly, I have no experience in neck deflection under tension for mandolins, do they vary a great deal ?

[Paul Hostetter]

If you have a really old mandolin, you can expect it's done about as much shifting and so on as it's ever going to do. I usually reconfigure things like neck angle with an expectation that it might shift/sag/slump/bow enough again to need some anticipated help. That's why I said make your planned bridge a bit high.

[Tim Mace]

Your mando will determine its ht.The ones I make are all different but thickness is usually less than 1/4 in.And even though most F/T's aren't compensated I do it anyway to avoid the slanted look so common in straightline saddles.Also I remove material in the middle(arch),Another thing I've been doing is using an adj.
style bridge w/flat bottom to better get a ht. est.Remove and copy......Show us your mando!

[Tim Mace]

here are a few

[Paul Hostetter]

I think we need to see this mandolin of Paul's. If it's what I'm thinking it is, I wonder if a bridge like that is even advisable for the type of construction I'm imagining based on the description. A photo would really help.

[Paul Hostetter]

Sorry, I replied to the part about deflection, but not the bridge. I doubt that big piece of bone is original, but it doesn't hurt. There's a case to be made for using simple ebony, no bone at all, but those bridges are small enough that having 15% of it be bone isn't going to be an issue. The main thing is getting the bridge to fit the top precisely. Do that first, then dial in the height and compensation.

[Ned Knepp]

I rebuild an old Kaykarft archtop Mandolin last year with a low solid bridge made of ebony and a bone cap that I'm fairly sure was original. The cap was in bad shape but I left it until I had the neck set then fine tuned the bridge height when I replaced the cap. It worked out pretty well. I only changed the height of the bone cap but about 1/32 of an inch so it's not apparent. I don't think I would go very high with this cap because the ebony base is so narrow. The instrument sounds pretty good for what it is, not a Martin or a Gibson but not bad for what it is and I think the bone helps that a bit.
That said, I'm not going to bother throwing a bone bridge on my Gibson in an attempt to improve it.
Ned

[Paul Lupus]

Thanks to all for the input. Great photo / example Tim, good input about having an adjustable to fool with. I think the bone vs. ebony discussion is interesting and essentially the decision is most affected by whether or not the bridge is intonated (hence larger piece of bone) If I go with ebony only, I think I'll look for a looser grain piece of ebony and saturate the top portion with water viscosity cyano to toughen up the resistance to unwound strings cutting through. Relieving the bottom to create an arch is also a cool idea, but the width of the feet will have to be wider. An issue I also am thinking about is that the bridge sits on the inlaid pick guard which is challenging. Good input also about the cap and height / width of the bridge Ned.
Thanks,
Paul

[Paul Hostetter]

It's what I thought. I think it would be inadvisable to set the neck angle in order to take a bridge like Tim showed. It's ladder-braced and has a cranked top, it's simply not up for that kind of tension. A maximum height would be 1/2" to start, figuring that it might need to be brought down a bit to around 3/8" after it's settled in a bit. You could try taller, but be careful. Look at Neapolitan mandolins and Martin A's for the basic idea. Here's a really nice Martin one:

[Tim Mace]

All the bridges I photo'd fit into the ht you mention Paul and all sound fantastic.. 5/8 max.And all I have made so far were ladder.Most angles are @ 3-4 deg.I don't care for a near flat angle as the bridges want to move w/too little tension.Oh well they ain't Martins but Martins were never my fav for tone or flat top.

[Paul Lupus]

Thanks for the swell photo, it'll be quite helpful. Yes, because the bridge on this instrument sits right at the margin of the "fold" of the top, (just behind the bridge) I won't have the advantage of slightly twisting the bridge to wring out a couple of cents more of intonation. The bracing on this little guy is quite light and I think I'll leave it with the exception of the main angled transverse brace, which I may beef up a tad. All input given also gave me pause for thought that although the "Count Basie" mustache wings of the original bridge are kinda deco, there is a point of diminishing return on transmission of string drive and unless the underside of the bridge is slightly cupped end to end, the thing would probably rattle out at the ends eventually. Again, many thanks to all for your input.
Paul