Building a Bowl Back

the Padma · **Posted:** Mon Mar 16, 2009 2:19 pm

.
Building a non parallel bowl back.

I thought you all might like to see how the Padma fidgets around trying to do a "not parallel" bowel back.

All Doug fir build with spruce top and bracing and kurfing. Was hoping to do it all out of cedar but can't get me no cedar in the sizes me need for a while and well me don't feel like waiting, nor do I feel likes starting up the hill with a chain saw to get me own stick, so me using fir. Besides buddy at the lumber yard showed me this really nice fir plank....had to buy 14 ft of 2 x 12" but that's ok. Neck body and back cost $15. enough for 2 instruments.

Regarding wishbone construction,I have not shown pics of the bending or kurfing as the process is identical to my other builds posted in the Padma Builds sub forum on this site. I refer you to my earlier builds
http://www.luthiercom.org/phpBB3/viewto ... f=96&t=820
http://www.luthiercom.org/phpBB3/viewto ... 840#p15411
http://www.luthiercom.org/phpBB3/viewto ... 833#p15227

Look here, see the Padmas trial and error process for building a bowl back.
The 3/16" stave's were tapered on the 6 inch jointer and then half were rough bend late last night. Won't do that again ...Oh well.
To day they will get their proper final ark bent. Is best to finish the bend to is desired shape while hot rather than come back and finish it.
It probably would be easier to use a dish for shaping the ribs profile, and bracing and doing the bending...
however lets get one bowl back don did-ed befors me go into the time and hassle of making dedicated dish. The trouble with a dedicated dish is....me never builds two the same, so what me gonna do with the thing when its finished? Besides, the process of using a dish is so non thinking, non feeling and mechanical, and I rather enjoy the efforts of getting the "S" curved sides and end piece with an arced profile, and the bracing to all confirm to one arc. A lot of planing with a low angel.

And yes the 2 back braces are not parallel. This is to open up the " treble side "of the back in hopes of giving all them hi sympathetic strings some back to project and bounce off of.

the back is sanded to its final shape by double siding tape and 50 grid to one of the staves and then the stave double taped to a sacrificial board... plane first then sand....takes a few hours

bending a stave

checking it

shooting its edge on an upside down #5 ...should be using the #8 but the iron needs sharpening, and I wanted to get this series of pics out instead of grinding a nicked blade to day.

gluing it in place.

then its bend the next stave, shoot its edge and glue it down...then the next and the next and so on and so on ....

finally got the # 8 sharpened...more deck to slide around on.

3 staves gued down.

now its at 5 ...seven more to go.

up to 7 here.

9 staves in 9 hours... not too bad eh...maybe before midnight, me gets the last 3 in

one left to go

Many of the Ouds and other type bowl backers actually have their plane braised /welded to an arm on a stand that they bolt to the floor and can sit and shoot edges all day long, with a sheet of plate glass at eye level that they check the edge on. They use hide glue and a heating iron with about a 1 inch or so flat end. They heat the sucker up, slather on the hide glue and run the iron along the seam...instantly dried....no clamping...can actually glue up a bowl back up in about an hour or two depending on number of staves. Crazy!

The staves were 3/16 thick non lenticular, isosceles trapeziums (in the Queens' English) then bent and planar jointed just like a cooper stave (whiskey barrel

cleaning up the inside ~ removing weight.

Total time for this bowl back was about 25 hours.

This is me first bowl backer, and not wanting to mess it up with proud staves, I thicknessed them to 3/16 so as to have some meat left to plane, rasp and scrape off.

But now after 3 hours rounding of and thicknessing hard 1/4 sawed fir, I realize that they could easily have been an 1/8 as I really had no problem in gluing them up. A few were about 32nd proud here and there if that and I attribute that to my intoxicated state when doing the freehand bending. Oh well, 2 liters of brown beer made the bending go real easy.

You might notice I'm off the pot for bending, now got me a BBQ coal starter shoved in a length of exhaust pipe...works like a charm.

Next time...thinner staves and a jig bending, so the staves will all be the same that way there should be no or very minimal proud staves.

I will also design removable cross bracing so as to be able to sooth down the inside on the next one.

This back is thick enough to do some serious carving in...thinking of the 'Om mani padme hung' chant in
Uchang, the high falootin formal Tibetan script repeating it self like a freeze about 1/2 inch in all around the perimeter. I t would be very appropriate for a C# minor instrument. We will see.

Conclusions, ~ Flat back instruments...well the are kind flat, know what me saying
and carved backs for a compounded curved profile rim as are the type of instruments I build, are real hard to carve into the back a matched contact lip for gluing to the ribs as this tight fit can only be carved. I ain't figured out another way as of yet. Carving this triple compound curve, in my opinion is actually much harder to do than building a bowl. The bowl back has the advantage of much more pronounced curves to it than a carved back which opens up too much end grain and hence a weaker back as seen in many mandos. The bowl also creates a larger volume of air for greater bass response.

Final conclusion: ~ I believe bowl backs are way the easier to build, all thought they take about 8 hours longer, they look far nicer and offer a greater visual impact, especially if a contrasting narrow stave is incorporated...not to mention a larger sound chamber. Esthetically they are much more suited to the wishbone construction and design of my instruments as a whole.

So for me it looks like me gonna be doing bowls for a while.

Blessings
the
Padma

Colin S · **Posted:** Mon Mar 16, 2009 5:46 pm

Call that a bowl back!

Now this is a bowl back!

Attachment:

8-Course Heiber back.JPG

Colin

Bruce Dickey · **Posted:** Mon Mar 16, 2009 6:33 pm

That is some pretty awesome work there.

Yours too Colin, purty. Got a sound clip of that one?

I've never once wondered how they made those.

I guess I just thought that's so hard to do I don't want to know how.

But, I think it's really awesome. [:Y:]

DannyV · **Posted:** Mon Mar 16, 2009 10:27 pm

"Off the pot and on the pipe". Not very Kootenay like Padma.

I've been playing a little in C# minor. I'm not sure but I think I may have hovered a little.

Great posts and very cool work. Keep it coming.

Cheers,
Danny

the Padma · **Posted:** Tue Mar 17, 2009 11:45 am

DannyV wrote:

"Off the pot and on the pipe". Not very Kootenay like Padma.

Cheers,
Danny

I thought I had better clarify that statement of mine regarding bending wood with this pic. Woodn't want anybody to get the wrong idea about the Padma now wood we?

What I meant was, "I don't use the pot to bend on now that I got the exhaust pipe and electric heater, which is much safer."

Blessings
the
Padma

Bruce Dickey · **Posted:** Tue Mar 17, 2009 8:18 pm

Padma the Outrageous, I have a question.

How do you make those awesome multi-exposure pictures?

They are awesome, give the feeling of blur and movement in a still photo.

Mighty nice.

Now I know how to build an Ark, should I ever need one too!

nickton · **Posted:** Wed Mar 18, 2009 12:53 am

Very cool post. Are those bicycle inner tubes?

the Padma · **Posted:** Wed Mar 18, 2009 2:26 am

nickton wrote:

Very cool post. Are those bicycle inner tubes?

Yo, nickton,

yes and no.

all are inner tubes,

bicycle tubes are the thinnest, then I have some for cars...hard to find now days and some cut from big big truck inner tubes. All for different strength clamping/ binding.

the
Padma

the Padma · **Posted:** Wed Mar 18, 2009 11:57 pm

Filippo Morelli wrote:

The Padma, when is the next video due out? They are priceless ...

Filippo

Yo, Filippo

Thank you for asking and for you kind comment.

There are currently 14 videos up at http://luthiertube.com

Got another one shot, but have been vacillating in editing it. Truth is, I've lost interest in that particular project.

Me spent 8 years producing and directing Television and well the truth is ... video don't really interest me. no more. Ya I did the ones on luthiertube more as a joke or to get some sample of me work out. SO to answer your question ... I don't know, probably after the 2 mandos, the bass and the C#minor Sympatars have been build...like next winter I would think.

But don't worry, when the next video is out, I will post trailers for it here at OLF and else were.

blessings
the
Padma

meddlingfool · **Posted:** Thu Mar 19, 2009 12:19 am

Query,
I hope I can articulate this understandably... How do you angle the sides of the staves, the edges which touch each other, as you go around the arc of the bowl back. From what I perceive as you shoot them on your plane, you are putting in a right angle edge. As you go around a convex surface, they would touch on the edge on the inside, but leave a gap visible from the outside. How do you make the angle as you shoot them which will allow them to butt against each other edge wise, whilst still allowing them to follow the radius of the ribs? Do you know what i mean?
Hmmmm... scritch scritch.

the Padma · **Posted:** Thu Mar 19, 2009 10:06 am

meddlingfool wrote:

Query,
I hope I can articulate this understandably... How do you angle the sides of the staves, the edges which touch each other, as you go around the arc of the bowl back. From what I perceive as you shoot them on your plane, you are putting in a right angle edge. As you go around a convex surface, they would touch on the edge on the inside, but leave a gap visible from the outside. How do you make the angle as you shoot them which will allow them to butt against each other edge wise, whilst still allowing them to follow the radius of the ribs? Do you know what i mean?
Hmmmm... scritch scritch.

Yo,
meddlingfool

Think of a water melon sliced from pole to pole.
Remove the fruit and look at the rind, it is wedge shaped.. It is pointed at both ends and wide at the middle or equator ~ So shooting the rind (the stave) is like cutting thinner slices of the watermelon.

Quote:

you are putting in a right angle edge. As you go around a convex surface, they would touch on the edge on the inside, but leave a gap visible from the outside.

Yes that is the whole idea of shooting the edge of a convex surface....you are flattening that surface.

Shooting the edge of a convex surface is like laying an orange slice flat on the sole of the plane and
shooting that across the blade. The wrinkly side of the the orange slice will get flatter and smooth.
Well actually it won't simply because it is an orange slice and will get sticky messy orange juice all over your plane.
So imagine a wooden ball sliced up pole to pole with wedge shapes like a orange sections...now start shooting the sides of them wedge slices. No matter how many times you shoot / shave a layer off, yo will still be able to reassemble the ball ~ with no gaps....how about that.

Get the idea.

If this illustration don't work for you...go mark two intersecting longitudinal lines on a piece of flat stock, band saw it out, bend it into an ark ( the stave) and shoot it on a plane...then you will get it.

blessings
the
Padma

meddlingfool · **Posted:** Fri Mar 20, 2009 9:25 pm

Thanks, I think I get it.

the Padma · **Posted:** Sat Jun 13, 2009 11:49 pm

current state of affairs. so the box is closed up....flat lutz spruce top with " parallel bracing", fir back , banded and on to fidgeting the parts, tailpiece, 2 bridges, fingerboard, and discover that we are comming in at a 29.25 inch string length

layin down the mystical incantations in ancient symbols and their placement on a sign wave running on the fingerboard to possibly become the cosmic dragon or an inlay of stars or even simple assorted size dowel and gee ...maybe even brass on the harmonics.

here you can be seeing the upper and lower strings and the two bridges.

Is going slow ... but is going...one day is gonna be gone and then what ?

blessings
the
Padma

the Padma · **Posted:** Thu Aug 27, 2009 5:28 pm

.

Well its almost finished. She be strung up. Needs set up yet.

What me learned.

Dough Fir is too heavy for this design...gonna rebuild it in all cedar.

Neck too long without frets, although a bass player could probably handle it.

Neck still too long for the inline tuners and tailpiece ~ very hard to find strings.
I had to extend the strings up on the peg head by adding shorter lengths. Tacky,
but it works.

Gonna cut the design back from a 30 inche to about a 28 inch string length.

Do not like the flat top at all. Flat flat flat. Yuck.

Won't be able to really tune her up till I get some of that stuff to stop the pegs form slipping tomorrow.

Is loud and with all them extra strings and that tone plate inside...she just be a ringing every
which a way. Don't even breath on her or she starts singing. Won't be able to assess the tone plate or her sonics for a few days yet. However it seems that the jewari bridge works real good at getting them sympathetic strings to buzz.

Basses are week simply cuz me got the back too thick...more to doing a bowl back than meets the eye.

Carved the back and well Doug Fir ain't a wood you wanna be carving low relief into. It works, but
never again.

For the life of me I don't know why I used Doug Fir for such a large build. Might have been one of them seniors moments. idunno

Took a good look at the quality of me jointery and decided it wasn't worth the effort
and time to build and install a damper for the sympathetic strings. So I didn't.

Didn't have enough box wood for 14 pegs so used some hard red stuff...don't know what it is.
Strong enough, not the best for holding detail but by the time I got to the pegs, my head
space was really stressed and so I used the laith work as therapy and will tolerate the final product.
If it were a clients they would be chucked in the stove.

Although I am please with its design and I succeeded in the translation from drawing to finished
build without loosing the concept, the quality of craftsmanship is deplorable.
This build was started this spring...sorta to get my mind off of all the BS that was going
down all around me. Well it worked good for that so to speak, but as far as a quality build ...
its a piece of crap. Every single emotion, and all the stress I have been under can be seen at
every stage of its construction. I will wait till it has been set up and really played to hear
just what she sounds like, and it better be good, or I'm afraid its firewood. No joking dudes, my craftsmanship on this build is a real dog.

Oh well, can't win them all.

Will post sound and video as soon as Jiles shows up. Don't hold your breath...him a musician but he will show one day.

blessings
the
Padma

StevenWheeler · **Posted:** Sat Aug 29, 2009 1:04 pm

The,

It's so nice to see you finished this. To bad about the workmanship. Pictures soften the uglys so I'll just take your word for the build quality. I've followed this build on this and another forum and am looking forward to hearing what a "Padmitar" sounds like.
I'm just getting to the point where I am reasonably happy with the guitars I build. I find watching you take an idea like this from concept to design to completion truly amazing. Thank you for marching to your own beat.

Steve

BruceHerrmann · **Posted:** Sat Aug 29, 2009 1:38 pm

I have to agree with Steve, it's great to see work like this and the design process that goes into it. Thanks for taking all of those phots and for all the time that they represent. Great stuff and inspiring.
Thought you might like to see the buck that Martin used to use when making bowl back mandolins around 1900....I've always thought making something using a buck like this would be fun. Seeing your photos confirms that. Thanks.

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