German (Seiffert style) mandolin construction

[tom.gibson]

Somehow I've got it into my head to make a modern German style bowlback, but not having any actual instruments to hand, I've been drawing up plans based on pictures. This leaves me with quite a few questions which I was hoping some of you classical forum people might be able to help me with.

In the first place, it looks to me like the angle of the cant/bend in the soundboard is a lot less than it is in the Italian mandolins. This would mean a much reduced break-over angle at the bridge and therefore considerably less pressure on the soundboard.

If this is right, it seems that the soundboard should be built to be less stiff, which brings up a couple of questions. I can't see any noticeable transverse arch in the soundboard in pictures I have of Seiffert, Woll, Knorr, Brian Dean or other 'German' mandolins. Does anybody know how much, if any, curvature there is across the top in any instruments they have, have made, or have seen?

I'm also wondering about bracing. I have some photos of Seiffert's bracing, which doesn't look particularly light. It even seems to include three fan braces behind the bridge which aren't there in a Calace or Embergher etc. If anybody had insights on this, or any knowledge of other makers' bracing, I'd love to hear.

I'm sure I have more questions, but since this is possibly rather esoteric I'll see first if anybody bites...

[Bruce Clausen]

Interesting project and great questions! I'm afraid all the help I can offer is a bump to the top here. Hope some owners or builders will be able to contribute.

[tom.gibson]

Thanks for the bump Bruce. I've actually been looking at more Italian bowlbacks and see a big difference in cant angles even amongst them. In archtop terms the difference in static load on the top would be equivalent to changing the neck angle by three or four degrees, which is a lot. Interesting...

Have any of you bowlback restorers got top thickness measurements for various instruments? I was thinking somewhere around 3mm, but the Embergher I'm borrowing seems to have a very thin top (hard to measure, however, because of soundhole binding).

[mandoisland]

The book about guitar lutherie "Die Gitarre und ihr Bau" by Franz Jahnel has some pages about a mandolin with a plan, this is taken from a mandolin by Dotzauer which is an early model of a German mandolin. If you send me a PM with your email address I can send you a scan.

I do not know of a source of plans of a Seiffert model. I am not sure if the luthiers like to share their plans... but there are many pictures of German mandolins on the websites of the luthiers which show the proportions and the outside of the mandolins.

[billhay4]

I would suggest you contact luthiers of this kind of instrument directly. Some are accessible, some are not. Also, I'd post this in the Builders section of the MC. Most builders who frequent that section are quite open to sharing information and ideas.
Bill

[tom.gibson]

Michael, thanks very much for the offer. I have drawn up my own plans from available pictures and started work on the bowl, but any further information, especially regarding what is not visible from the outside (bracing etc), would be very useful.

Bill, I thought of putting this on the Builders forum (which I often visit), but since the only real information on bowlback construction and repair I've found on the Cafe has been here, I thought this was the better place.

[tom.gibson]

Just to finish the story which was started here a year ago, I did finally complete this project and learned a lot in the process. If anyone is interested, I've posted a few pictures of the finished mandolin in the Photos, videos, etc. forum.

[margora]

A very beautiful instrument. I sent you a PM about German Seiffert-style mandolins in Australia.

[Jim Garber]

Very nice. For convenience, here's the link to pics and Tom's description.