$100 Challenge- Apple bowl back Octave Mandolin

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$100 Challenge- Apple bowl back Octave Mandolin

Postby Josh Humphrey » Sat May 05, 2012 1:58 pm

Well, I think I may just be able to pull this off! It will be tight but it's worth a try!

This is the apple billet I sliced to 3/32" for the ribs of the bowl. I harvested the apple in my backyard five years ago, so it is VERY local. I paid $1000 for about the same number of board feet slab sawn and kiln dried, so I'll say at 1.5 * 6 * 22" its around 3 board feet or $3.
billet.jpg
Sliced apple billet


A shot of the sequence.
sequence.jpg
Rib blanks in sequence
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Re: $100 Challenge- Apple bowl back Octave Mandolin

Postby Josh Humphrey » Sat May 05, 2012 7:52 pm

I am planning to have a modified bowl- not the common half-round radius, but a more flattened back shape so the instrument is not as bulky. It involves a bit of guesswork and various radii, but I've been wanting to try this for a while!
1plan.jpg
Plan

First step is to create the assembly that holds neck and tailblock in place for gluing up the ribs. Neck block is marked.
2roughblock.jpg
Neck block marked

Then is rough cut.
3blockcut.jpg
Rough cut neck block
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Re: $100 Challenge- Apple bowl back Octave Mandolin

Postby Josh Humphrey » Sat May 05, 2012 7:55 pm

Then the neck block is shaped to match the profile of the body, and attached to a long holding block.
4blockattached.jpg
Neck block attached

Similarly, the tailblock is shaped and attached to the holding block.
The tailblock is usually half round, but since the bowl will be the flattened irregular style, it is elongated and looks odd...
5tail.jpg
Completed holding block

Now it is time to sand the ribs to thickness and start bending!
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Re: $100 Challenge- Apple bowl back Octave Mandolin

Postby Josh Humphrey » Tue May 08, 2012 11:35 am

Sanded the ribs to thickness. Then, made a profile rib by bending one to shape, fitting it, and flattening it back into a template.

Here are the ribs rough cut (the center 7 have altered bottom shapes to fit the flattened back)
ribs.jpg
The ribs rough cut


Then in trying to fit the first rib I realized both the tailblock and neck block needed to be reshaped to more closely fit the outline.
tail2.jpg
Tailblock take 2


Finally, I got the first rib fit and glued in place.
rib1.jpg
Rib 1 in place (actually rib 8)
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Re: $100 Challenge- Apple bowl back Octave Mandolin

Postby Josh Humphrey » Tue May 08, 2012 8:33 pm

Got a bit of work done- now 4 ribs. Time is tight this week, so I hope I can squeeze in enough time to get caught up...
ribs4.jpg
4 ribs
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Re: $100 Challenge- Apple bowl back Octave Mandolin

Postby Andrew Porter » Thu May 10, 2012 9:54 am

Looking good. I can't wait to see the finished product. I admire your adlib on the back. Did you cut the neck block on a bandsaw?
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Re: $100 Challenge- Apple bowl back Octave Mandolin

Postby Josh Humphrey » Thu May 10, 2012 4:39 pm

Thanks Andrew! In that regard, the ad lib is working out OK; there is something off with the geometry for sure which is making it end up overall about 3/4" narrower than the plan!! Once I get this one built, I can have a closer look and better idea how to get the next one right.

Yes, the neckblock was cut on the bandsaw.

Here is the latest bottom view:

clampRear.jpg
Bottom of bowl


And a front view. I am liking this improvised clamp situation.

frontclamp.jpg
Front


Finally- a close up of the new flexible clamp idea. Just add more rubber to get more power; it flexes to any part of the curve, and it pulls up towards the next rib each time.

clamp.jpg
Rubber band clamp
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Re: $100 Challenge- Apple bowl back Octave Mandolin

Postby Josh Humphrey » Sun May 13, 2012 11:05 pm

Wow- only a week left! Better get busy...
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Re: $100 Challenge- Apple bowl back Octave Mandolin

Postby Josh Humphrey » Mon May 14, 2012 2:17 am

The bowl, pretty much complete
fullbowl.jpg
Apple bowl
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Re: $100 Challenge- Apple bowl back Octave Mandolin

Postby Josh Humphrey » Mon May 14, 2012 2:21 am

Now time for the soundboard. I have this piano soundboard given in trade by a local friend- I don't know if the spruce is local but I think it's been here long enough- he had it in his garage for 40+ years!

soundboard1.jpg
Piano Soundboard


I cut it up into manageable parts, and saved one for this instrument. Here it is, sanded to thickness. It ain't pretty, but it sounds excellent- a very rich tap tone. I think it will have "nice character..."

soundboard2.jpg
Thicknessed soundboard
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Re: $100 Challenge- Apple bowl back Octave Mandolin

Postby Josh Humphrey » Wed May 16, 2012 2:49 pm

Now for the rosette- I have been developing this idea for the last dozen or so instruments. This one is spruce and walnut (shop made purflings leftover from another project!)

rosette.jpg
Soundboard rosette


And the bracing.

bracing.jpg
Bracing


Solid linings for the bowl; hopefully I can get the top glued on tonight and have half a chance of finishing...

linings.jpg
Gluing in solid linings
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Re: $100 Challenge- Apple bowl back Octave Mandolin

Postby Jason Rodgers » Wed May 16, 2012 4:02 pm

I'm not familiar with the variety of staved back construction techniques, but I like the seemingly simple (is it?) three-section method you're using. Not all the staves converge on the same point at the tail, but so what. This is going to look really cool!
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Re: $100 Challenge- Apple bowl back Octave Mandolin

Postby Josh Humphrey » Fri May 18, 2012 1:30 am

Got soundboard glued on this morning' very interesting to clamp! Then bindings- some leftover shopmade walnut with fir striping

binding.jpg
Binding taped


The bridge was an incorrectly sized one from previous project, that I think will work swell for this! It uses about $1 of madagascar rosewood.
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Re: $100 Challenge- Apple bowl back Octave Mandolin

Postby Josh Humphrey » Fri May 18, 2012 1:37 am

Now for the fingerboard: I saved a chunk of nicely figured walnut for this purpose, and resawed today. I got 6 boards out of an $8 piece; so that's $1.50. Here is the blank

fbRough.jpg
FB blank


I slotted it, radiused, and glued on some ebony bindings (scrap offcuts of a previous fingerboard) with strips of maple veneer for a contrasting stripe on the sides.

fbBound.jpg
FB bound


I will TRY to get the position markers inlaid tonight
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Re: $100 Challenge- Apple bowl back Octave Mandolin

Postby Josh Humphrey » Fri May 18, 2012 2:08 am

I got the neck blank glued up, and the peghead overlay glued on tonight- if I can get the neck shaped, frets in, some other odds and ends done tomorrow, I have a prayer of putting some finish on on Saturday and assembling Sunday. I'm not giving up yet! :?

pegOverlay.jpg
Gluing peghead overlay
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