Mandolin from scratch questions

[IvanaL]

Hey all, I posted a few weeks ago (the thread has been closed) and got a ton of valuable advice from many generous luthiers on this forum. I've almost finished my (tiger maple top, walnut back and sides) mandolin carved out of two solid pieces of wood. I've gleaned that maple tops are not ideal, but I was thinking if I don't like the sound I can use an ultrasonic depth gauge to assist me shaving off excess wood, the idea being to compensate for the denser maple by making it thinner than the traditional spruce. I'm still learning (1st mandolin) so I don't know how much effect removing 1/3 of the material will have on the tone. Can anyone give me some advice about material thickness ideals on each of the surfaces of a mandolin? I also have one more important question: The bridge is the last piece of my instrument which I need to attach before I can test it out, but the bridge I bought has the "steps" so that each string will not be the same distance from the nut as the others. Is this normal or do I need to angle the bridge a bit? Do you fellas glue a bridge without first playing it somehow? Though I'm using hide glue, it would still be a pain to unglue and refinish the mando if the placement is a little off. I am very grateful in advance.

[Marty Jacobson]

IvanaL,
You designed your own instrument, so nobody can tell you what the specs should be. I designed my own instruments, too, and a very real drawback of having done that is that nobody can tell me exactly what the properties of my mandolins should be. I had to figure it out myself, which took about ten mandolins. Four mandolins had obvious problems before I even finished them, but I moved on and built more, learning from those mistakes. Don't get too hung up on one instrument. If it needs to be refined, sometimes you can make it work on the one you're building, but sometimes the first instrument of a certain style is just a stepping stone to the real first mandolin of that new style.

There are several things we'd need to know to give you good information - neck angle, bracing size and location, stiffness of your individual piece of maple used on the top (slab cut or quarter sawn?).

So what you might need to do is rig up some way to see how flexible the top is. You want to carve it thinner without making it too weak. If you can somehow measure deflection of the plate under a weight, you can put a 20lb weight on it and carve it until the top deflects .010" or so under that 20 pound weight at the bridge location. That should be safe to string up. I don't think an ultrasonic thickness gauge will do you any good, since the surfaces are not parallel and are not homogeneous (wood cellular structure gets in the way).
My guess without knowing any of the geometry related to your instrument would be that your top should be somewhere between .200" and .100" thick, but since it's probably slab-sawn, not thinner than .100". And because it's maple, definitely not thicker than .200". It can be thinner at the edge than it is in the middle, up to 2x thicker in the middle than it is at the edge. So you could end up with .100" at the edge and .200" in the middle for starters, and then remove more material from the center until you think it sounds as good as it can.
Worst case scenario, it caves in and you've learned something. You would probably enjoy reading Siminoff's Ultimate Bluegrass Mandolin Construction Manual and/or Graham Macdonald's The Mandolin Project, both available online. If you're going to buy one, buy Graham's, because he gives you the principles you need to design your own instrument without saying it has to be done one certain way.

[EdSherry]

Mandolin bridges typically aren't glued on; they're held on by string pressure. See Siminoff's book. Or contact Rob Meldrum and ask for a copy of his book on setting up mandolins.

[Bernie Daniel]

What kind of a mandolin are you making? I think you would be better assisted if you posted a picture of your instrument so we know what we are discussing. Normally mandolin bridges are floating bridges and are not glued in place. If you are making a flat top mandolin then it might be a different story. You are correct a maple top and walnut backed mandolin is certainly not your routine way to go as far as woods are concerned anyway.

[multidon]

[buckhorn]

the only stupid question is the one you don't ask..........my first mandolin was a scratch built..matter of fact, I bought a cheap-o after I started the build to be able to say I was learning to play(still can't)..that first one took almost a year and a half, after putting two different tops on it.. got so discouraged I had to put it down for a few months and think about it..it was a true log..I didn't even have a thickness guage..the second was better, but the third one was a real zinger..I was hooked..now, "the build" is always on my mind..if it does get taxing,step back and look at it a while..and don't stop asking those questions...few people have all of the answers, but with the caliber of people on this site it's not far away..and there seems to always be a better way to skin a cat.......

[Bill Snyder]

I hope this does not cause any problems but many of the questions asked by those wanting to help can be answered in IvanL's first thread. http://www.mandolincafe.com/forum/sh...tch-has-issues

[CedarSlayer]

Ultrasonic thickness gauges are generally not considered useful for measuring wood, foam or paper. Additionally the accuracy drops on materials with curves, changes in thickness and variable densities.

Bob

[Bernie Daniel]

I hope this does not cause any problems but many of the questions asked by those wanting to help can be answered in IvanL's first thread. http://www.mandolincafe.com/forum/sh...tch-has-issues

I did take a quick look at that thread but hopefully the mandolin now has frets,a bridge, a nut and a full set of strings so perhaps more can be gleaned from a picture?

[IvanaL]

I'll post new pics once I string it up and test it out. Should be able to do this later today. Thanks everyone for taking an interest in my project.

[belbein]

I hope this does not cause any problems but many of the questions asked by those wanting to help can be answered in IvanL's first thread. http://www.mandolincafe.com/forum/sh...tch-has-issues

I ain't sayin' nuttin.

[Jim Garber]

Worst case scenario, it caves in and you've learned something. You would probably enjoy reading Siminoff's Ultimate Bluegrass Mandolin Construction Manual and/or Graham Macdonald's The Mandolin Project, both available online. If you're going to buy one, buy Graham's, because he gives you the principles you need to design your own instrument without saying it has to be done one certain way.

I agree wholeheartedly with Martin's recommednations. I, too, am finally, after a number of years, finishing up a Campfire flattop mandolin kit and then (hopefully) diving into a scratch build. I am much more cautious about just diving in and my approach (based on my personality type) is to do as much research as I can. I have a pile of books on instrument building i have accumulated over the years with all this in mind. I have been studying Graham's book in preparation of doing my scratch build.

I heartily compliment you, IvanaL on your courage of diving into it without a net, but also encourage you to take a look at the conventional way to make a mandolin and then adapt it to your purposes.

[IvanaL]

Here's a picture. I strung it up and it played well though not as loudly as it should. I have started taking material off the back, sides, and top to see how it will play. Anyone know a good method of getting the frets the same height so I can get some super low action?

[Jim Garber]

Here's a picture. I strung it up and it played well though not as loudly as it should. I have started taking material off the back, sides, and top to see how it will play. Anyone know a good method of getting the frets the same height so I can get some super low action?

The photo did not show up.

Fretting at frets.com -- an excellent site with lots of good info

StewMac Free Fretting info

[Rick Lindstrom]

I can't quite make out how you would be able to tune the A strings. Could you give us a photo of the back of the peghead?

Thanks!

[IvanaL]

I carved some little spaces for the tuning nobs. It's not ideal, but tuning is not a problem.

[IvanaL]

I edited the post and the photo should be there. Please let me know if you still can't see it.

[Petrus]

It actually looks acceptable at the body, up until the root of the neck where it turns into a design disaster. Looks like you got a little carried away with the wood carving on the scroll(s) and headstock; but that can be remedied without affecting the soundbox in the slightest. (Don't get angry if I respectfully suggest you could cut off most of that headstock scroll business and make a nice rounded head. I know you didn't ask for that and maybe you like it that way, and it wouldn't affect the sound anyway.)

The face/table may have problems of lack of resonance as many have noted above, due to its being made of maple; then again, I have an all-mahogany Gretsch, and mahogany is itself not as resonant as other woods like spruce; it's quiet like I like my instruments. Worst case, you could install a pickup and make an electro-acoustic out of it.

The good: I see you took the trouble of putting on a quality cast tailpiece. The f-holes are well done and proportional. Had you stuck with the simple oval body and a simple square headstock, you'd be way ahead of the game right at this point. Again, fixable.

For comic relief, here's my latest attempt at a kit or box fiddle. I bolted a 1/2 size violin neck to a box I got at a thrift store for $2. Screwed on a tailpiece and chin rest from the remains of the original $25 fiddle. It could pass as "vintage," maybe, since there's no indication of a date anywhere (and technically both the neck and the box really are vintage, just not the mating of the two.) Ironically, the hollowness created by slats all around actually helps get sound out of it. I've considered installing non-tunable sympathetic strings on the inside of the box (a la the Hardanger fiddle) but I don't know if they'd even resonate properly. Naturally, the squareness of the sides of the box interfere with bowing.

Maybe I should start with diddley bows.

[Petrus]

Here's something I saw advertised on Craigslist a few months ago for $200. Advertised as home-made. Several commentators noted that it is clearly the work of a good woodworker, but not an expert luthier.

[IvanaL]

Fun. I'm really enjoying learning from you gentlemen. What do you think of a speculation I have that if you make the maple thinner than the spruce so that they have the same mass that this makes up for the density of the maple and they should have similar loudness? What are some drawbacks to having thin walled instruments? Are there any benefits to having thicker walls? Why is it preferred to have denser woods for the back and sides of the instrument? Would it theoretically be better to make the entire instrument out of spruce? Sorry to bombard you guys with questions, but I'm fascinated with luthiery and I love learning about it. This forum is a magical place

[Pete Jenner]

Stiffness not mass is the key to understanding why certain woods are favoured for certain tasks over others. Stiffness in wood and other biological materials is directionally dependent. The reason spruce, cedar and the like are used for tops is their superior stiffness along the grain. This property is called anisotropy‎. All wood is anisotropic (as opposed to isotropic) but spruce has one of the best strength to weight ratios in this regard (second only to balsa I believe). Similar masses of spruce and maple will have quite different anisotropic values. Do yourself a favour and search previous threads on the subject in the forums and elsewhere on the web.

[Bluetickhound]

Which is whu spruce isthe preferred wood for.aircraft construction. Light and strong is a combo thats hard to beat...

[IvanaL]

Interesting. But mass must have something to do with the vibration of the top since luthiers tend to make them as thin as possible (thereby reducing their mass). Can anyone enlighten me as to why making my mandolin thinner on the top and/or back and sides would be a good idea? My mando is currently about .15" around the edges of the top and .25" in the center. It's considerably thicker on the sides and bottom corners at over .5".

[Marty Jacobson]

Search is your friend -- look for anything posted in response to similar topics by Dave Cohen, sunburst (John Hamlett), or Peter Coombe. There are literally thousands of such responses from those three gentlemen alone, so it's a good place to start.

[IvanaL]

Thanks so much, but I'm not too savvy on searching for those specific threads. Would you mind posting links? I appreciate your help very much.