BYO Top and Back Thickness

Bones

I'm thinking about building some Selmacs using Sitka tops (bearclaw) and SOLID wood backs (maple, rosewood and walnut).

Does anyone have any ideas of what thickness to shoot for on solid backs (as opposed to laminated).

Thanks

Bohemian

Can't specifically tell you about Sel/Macs , but in Cumpiano's "Guitarmaking Tradition and Technology" page 104....
" steel-string backs on full sized guitars in our shop vary from .110 inch for mahogany to .100 inch for rosewood."

Bones

That's the range I was thinking of for a solid wood back.

I think the laminated Selmacs were a bit thinner at around .09".

Thanks

Ken Bloom

When I built my Selmac seven string I made both the top and back .080". A flat top with a pin bridge is subjected to very different stresses than a Selmac top with a suspension bridge. The curves and arches in the Selmac top support the strain very well. You do need a good piece of close grained spruce for strength. I used rosewood for my back and sides which is very dense. Maple is not as dense and you might want to consider going a bit thicker if you use a less dense wood. The Michael Collins book on building Selmacs has much good info in it. I don't agree with everything in there but between this forum and what is in there I think you'll get a good picture.

Ken Bloom

Bones

thanks Ken, I'll check out that book

Bohemian

Writing a book, particularly a technical book, is a tremendous effort..however, The Collins book has enough errors and conflciting and extranneous information that I do not consider it to be a credible and reliable source .

I would recommend reading it thoroughly.. though I would not recommend it as a "bible" but as
a curiously considered source. I would also recommend reading the Benedetto book on guitar construction or the Cumpiano book.. not for specific information, but how a book of the type can be wriiten, and for a comparison of price/value. Yes, I own all three: Collins, Benedetto and Cumpiano as well as Bogdanovich (classical) and many others. I own the Collins book only because it is the only book specific to Sel/Mac ( actually Favino interjected) and I collect instrument books.

I would find a Dupont or a DEll 'Arte or another premium Sel/Mac or Favino style guitar and take a micrometer or caliper and measure the top for a more credible measurement... the back would not be as critical... I would think that anything around .100 would be workable for a back with variances for density. And as Ken has posted... the top on a Sel/Mac does not have the same stresses ie the top being pulled up by pins but pushed down by a bridge tensioned with a tailpiece... and a "ladder" style bracing of impressive dimension and multiplicity of pieces. I suspect that Sel/Mac or Favino or other Gypsy Jazz guitars tops are thinner than the typical Martin dread

I'll check a few sets of plans that I have collected and see if their are some dimensions given for top and back.

Ken Bloom

Hi Bohemian,

I fuly agree with all that you have said regarding the Collins book. The Cumpliano book is :" the bible" for guitar builders for a reason. I found the Collins book useful mainly for some of the dimensions and a few other details. I took most of my info off the Charle plans and by asking questions here. What I finally came to were the dimensions that I quoted and the guitar has done very well for the last four years.
I compared as many different dimensions and measurements as I could including measuring a friend's Dupont and Favino. All of it was instructive and helpful. The only other bit of advice I would add is to pay very close attention to neck angle as this is a very critical factor in getting the right tone and feel. Good luck.

Ken Bloom

Bohemian

Collins uses different measurements on different pages for exactly the same piece/object being measured. Also the back and forth use of ,and not exacting conversion, of inches to metric is confusing and for lack of better words...sloppy and indifferent. I believe a more careful editing following input from literate readers with instrument building experience and from those who have read other such books may have helped. The content may be there ,but would benefit greatly from another level of production, editing and re-writing. .I also believe the price is obscene for what it is. ( that is also my opinion of some videos ... but I digress)

My opinion is that with plans from Summerfield, or other sources, the Charle(s) book along with the Cumpiano,possibly Bogdanovich and other steel string construction books; possibly resource material from the Guild of American luthiers... coupled with some hands on experience with Sel/Mac or Favino style guitars, would yield credible reults. Of course this is just IMNSHO.

Bohemian

Bones,

Why Sitka ?

I like it... and prefer it to Adirondack and all the other mystical, magical, mythical and usually higher priced woods...

But why Sitka for you and why "bear claw"
( which I recommended to CFM IV for the CEO-5 which he claims to have "designed.. but not true)

Craig Bumgarner

Three or four years ago, I built a Selmer style with solid bubinga backs and sides. I used standard dreadnought thickness dimensions for the back and sides (.110") and the guitar ended up sounding as much like a dreadnought as a Selmer.

I think regardless of whether the back & sides are solid or laminated, they need to be thinner and lighter (.080" to .090") to yield the best Selmer sound. Solid sides that thin can be fragile to work, so use caution and practice bending on scraps. The cut away bends are pretty severe and have to be right on. Once done, you have to be more careful throughout the building process and even in use. That is one of the advantages of laminated, they are tougher. I'm using four layers of veneer to get .080" laminated backs and sides.

Just saw Ken's post about neck angle, absolutely right, though I know from personal experience that you can get it wrong and still end up with an okay guitar. :oops:

Craig

Bohemian

Cool that you are making your own laminations

I believe that laminates were THE major key to the construction of the orignal Sel/Macs ...
construction technique specific to laminates, tone playability etc

I recall my first encounter with Dupont guitars more than a decade ago at Gryphon Music while Paul Hostteter was the importer/distributor and Dupont himself was making the guitars.

" $2300 for a laminated guitar, you're nuts!! "

Ignorance is not so blissful