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Message started by Matt Blacka on Mar 27th, 2007 at 3:38pm

Title: Assembly with domed soundboard
Post by Matt Blacka on Mar 27th, 2007 at 3:38pm
Hi, I know there has been other topics listed here about doming uke soundboards, how to do it, what radii are used, how to make dished workboards etc, but I haven't been able to find anything on how the doming affects the attachment of the neck and fretboard to the soundboard.

I have built one uke with a true flat top, as per Hana Lima 'Ia plans and manual, no problems. For my next few ukes I was going to try doming the soundboard, but am not sure how this will affect the attachment of the soundboard to the flat table at the end of the neck (spanish style). Should this area of the soundboard be kept flat or sanded flat? or is the dome radius so large that it doesn't affect the whole process? Should the neck be angled back slightly, so that it forms a flush plane (tangent) with the curve of the soundboard at the junction? Should the bottom of the fretboard be sanded to fit the dome for the area where it passes over the soundboard (from heel to soundhole).

Also, I'm interested to hear if people (particularly Mike and Asa) also use a dished assembly jig for gluing the sides to the soundboard (Session 6 Steps 2 onwards in Hana Lima Ia Manual), and if so, how this jig differs from the one shown in the manual (at the neck body junction section).

Thanks in adavance for your assistance

Title: Re: Assembly with domed soundboard
Post by Hana Lima Ia on Apr 1st, 2007 at 2:30pm
Hi Matt,
Glad to hear you’re willing to dive deeper into the process.  This does open up a whole new can of worms for assembly.  Fortunately the size of the ‘ukulele makes it easier to deal with.  On the ‘ukulele, a 25’ radius is very slight so not much adjustment is needed.

If you angle the neck down just 2 degrees you will compensate for the dome (this will form the flush plane).  Create the neck angle by adjusting your heel slots.  Keep the attachment of the soundboard to the flat table at the end of the neck (spanish style) flat.

The radius is so slight you wont really have to sand the bottoms of the fretboard or bridge to fit.  It’s easier to see what I mean in a picture:


The 1’ box would be the length of the soundboard and the 8” box would be the width of the soundboard.  From heelblock to tailblock there is a difference of about 0.085” or just a little over a 1/16”.  For the width it is only 5 hundredths of an inch or so...just a little less than a 1/16”.



With the neck you add a little more length so the curve is more pronounced.  The 2-degree offset will take care of it.  Final adjustment can be done as usual with nut and saddle height.

We do have a dished assembly jig for gluing the sides to the soundboard.  That is one of the worms in the can…but once you’ve put in the setup time it’s all good!  I’ll have to post pictures, but that is another story.
-Asa

Title: Re: Assembly with domed soundboard
Post by Matt Blacka on Apr 1st, 2007 at 2:56pm
Thanks Asa,

that clears up a whole heap of questions, the drawings are great, a picture says a thousand words. Now I've gotta get to work making some domed boards and an assembly jig. I've got a few other jigs and tools in the making as well. As you say, its all in the setup time.


Title: Re: Assembly with domed soundboard
Post by Likeke on Apr 11th, 2007 at 4:35am
On spanish foot type instruments usually only the lower bout is domed per Cumpiano.  If built this way, is it still necessary to change the neck angle?  Seems to me one could lower the bridge? ???

Title: Re: Assembly with domed soundboard
Post by Hana Lima Ia on Apr 11th, 2007 at 6:04pm
This is only if you were going to radius the soundboard.

Title: Re: Assembly with domed soundboard
Post by Matt Blacka on Mar 2nd, 2008 at 3:09pm
Another quick question sort of related to this topic.....

I know that braces/bars are sanded on a domed workboard before being stuck down to the soundboard or back, so as to create the domed profile, but are the bridge patch and soundhole patches also sanded to the domed profile, or are they simply stuck down using the dished workboard?

I am thinking that if the patches are stuck down without being pre sanded, but the dished workboard is used during glue-up, that the domed profile will be held anyway due to the lamination between soundboard and patch being created using the dished form......if this makes sense?

Thanks,

Matt

Title: Re: Assembly with domed soundboard
Post by Likeke on Mar 2nd, 2008 at 5:00pm
Yes, usually the upper bout is kept flat, but if you dome it you can sand the area where the fingerboard overlays the top flat.  If fact if you consult, OLF(luthiersforum.org) and check tutorials you will see a jig for sanding this area.  I would not dome the upper bout and make life simple for yourself.

Title: Re: Assembly with domed soundboard
Post by lefty on Mar 3rd, 2008 at 7:46pm
Matt,
I think that because the sound hole patch and bridge patch are so slim they can be glued down on the radius dish with a Go-Bar deck without any modification.

They will conform to the radius without a problem.

Lefty

Title: Re: Assembly with domed soundboard
Post by Matt Blacka on Mar 4th, 2008 at 10:53am
Thanks for your responses.

I glued down a bridge patch last night, which I pre-sanded to the domed profile. It worked fine, and is holding the dome shape in that area of the soundboard, even without the tone bars being placed yet.

I am making three fan braced ukes at the moment, but I don't think I wiill worry about pre-sanding the rest of the patches for the others.

Matt

Title: Re: Assembly with domed soundboard
Post by lefty on Mar 4th, 2008 at 11:33am
Matt,
Glad I could help.  I have not built a uke with a domed soundboard, however, the one steel string guitar I built I did not radius the patch.

Good luck with your ukes, How about some photos.
Lefty

Title: Re: Assembly with domed soundboard
Post by Don_Orgeman on Mar 4th, 2008 at 1:19pm
On a fan braced ukulele (or a classical guitar) the only braces that run parallel to or close to parallel to the centerline are the tone bars which start below the sound hole and are notched to fit over the bridge plate.  Since the bridge plate is glued in place before the tone bars (and is placed in a cross grain direction) there should be no problem with gluing the plate in flat and then adding some curve with the tone bars.  Most of the dome effect will have to be provided from the shaping of the sides.

By the same token, the two enharmonic braces can only provide side to side doming, and any doming shape above the enharmonic bars must be accomplished by shaping the sides.

On a steel string guitar (which is commonly domed) the main support is a X brace that when shaped forms the doming for the top.  While the sides and linings must also be shaped to match the doming, the top bracing supports the doming before the being glued to the sides.

While classical guitar makers frequently dome the backs, most seem to use flat tops, particularly if they are using a spanish heel.

If you are going to use a domed top, think of using a tenon joint with matching mortise in the body heel joint.  By robbing 1/8 inch from each side of the Hana Lima neck cuts ( 3/4" instead of 7/8"), you can get up to a 1/2 inch tenon which is wide enough to use two 8-32 X 2" hanger bolts to bolt the neck to the body, or glue the neck joint if you prefer.

On my steel string guitar I missed the angle slightly and had one devil of a time getting things to work out because I had used a tapered sliding dovetail joint for the neck/body attachment.  A tenon joint will allow you to fine adjust the heel to match the body and get the neck set angle to fit perfectly.  The tenon joint (and seperate neck) also makes banding the body a lot easier with both a domed top and domed back.  It can be done with a spanish heel, but is easier with two piece construction.

Good luck in your adventure.  Keep us posted on how it goes and what you decide and learn as you go along.

Don

Title: Re: Assembly with domed soundboard
Post by lefty on Mar 5th, 2008 at 6:51pm

Don,
 Well put.  Thanks for the info.

Lefty

Title: Re: Assembly with domed soundboard
Post by Wood_Butcher on Sep 7th, 2008 at 10:29am
Hi Matt,

Just want to revive this thread as there hasn't been much talk of domed fronts or backs lately.

I'm assuming that you've completed this uke by now. I'm in the same place now that you were then. I've cut a 12 foot radius work board for my back and am thinking about making a 22 foot radius for the sound board. My intention is to stick with the Spanish heel and angle the cuts 2 degrees (+/-) like Asa suggested.

Which route did you end up taking? Was hoping to get feed back on the building process form you or anyone else that wants to give me any hints.

Also have seen a little info on using a solera ( a term used for something similar to the Assembly Jig on pg. 71 of the Hanalima book) with a dish cut into it to create a dome in the area below the sound hole and the lower bout. Pete Howlett did a video on ukulelecosmos.com about it, but not much info about shaping tone bars or the bridge was included. Does anyone have any info on this technique as well?

Thanks,

Mark Schrier

Title: Re: Assembly with domed soundboard
Post by Matt Blacka on Sep 8th, 2008 at 10:56pm
Hi Mark,

I haven't finished this series of ukes yet. I have one that has pretty much been boxed up, and another three that are waiting for their sides to be bent (soundboard, backs, and necks completed though). You can check out the pictures on my website. They are all designed to have a Spanish Heel style of construction.

I redrew the concepts that Asa had posted before, with the angled heel slots, and worked out that the angle I needed was a fraction over 1 degree, to get the soundboard and fretboard to be on the same plane/angle at the neck/body joint. All four necks had their heel slots angled back by as close to this angle as possible.

When I made my domed workboards, I made two for the back dome and three for the soundboard dome. I have since cut one of the domed soundboard workboards down to the same shape of my assembly jig, and modified my original flat-top assembly jig to take the domed board as its surface. I also added an adjustable neck support to the assembly jig, so that I can accomodate the slightly set-back neck angle. For the one uke I have assembled, this modified jig worked very well.

The domed workboards worked fine for sanding and gluing braces using a go-bar deck.

One thing that may be of interest, is that I worked out a modified shape that the sides have to be cut to before being bent, to get the correctly domed soundboard and back profiles. Solving this problem required a combination of maths and CAD to investigate the height that the sides should be at all points around the side, where they join to the back and soundboard. This is a strange three dimenional problem, where the height of the sides at any point depends on the distance of that point from the apex of the dome. This is very different to a side shape for a uke with an arched back and flat top. I can write some more about these calcs if you would like.

Anyway, thats my current position on the domed soundboard/back thing.

Matt

Title: Re: Assembly with domed soundboard
Post by Wood_Butcher on Sep 9th, 2008 at 3:30pm
Hey Matt,

Thanks for the reply.

It's interesting that you can develop a shape for the pre-bent sides. I figured that I would have to put the bent sides in a mold and shape them in a dished jig. Are you trying to keep your front and back as parallel to each other as possible. I hope that makes sense or at least it would if both pieces were flat. I am envisiong the top (soundboard) edge of the sides being as straight as the radius will allow, but the back edge being a little sloped so that the body is a little thinner at the neck end. Can you describe what you've achieved in your design?

So it seems that the main concern when setting the neck angle is to make the fretboard fit as flat as possible on the sound board. Does it seem like the relationship between the fretboard and the bridge works itself out? In my mind, I see the bridge needing to be a little taller than on a flat sound board.

I checked out your blog. The woods you are using are pretty neat stuff. Hope your builds continue to go well.

Best Regards,

Mark

Title: Re: Assembly with domed soundboard
Post by Matt Blacka on Sep 9th, 2008 at 8:39pm
Hi Mark,

I probably should have made myself a little clearer. By pre-bent sides, I was refering to the flat pieces of side wood, before they are bent. Its easiest to cut the shape of the sides while they are in this state.

It is difficult to explain, but for my designs, I have started with a rectangular shape for the sides, that is 2.75" high at each end (tail and heel areas). I have then applied a a certain profile above above and below this rectangle, that allows the top and bottom of the sides, when bent, to fit the domes for all locations around the uke perimeter. If you would like, I could try to send you some sketches/CAD drawings to help explain this a little better.

I have done some calculations and CAD drawings which indicate that the bridge should be a little higher when using the domed soundboard, so as to not end up with too higher saddle. Asa has a magic number for the difference between the height of the bridge and the thickness of a fretboard for flat top ukes (I would have to look up what it is, but I have it printed somewhere), but I think this number needs to increase for the domed tops. I will be investigating this more when I come to cutting the bridges.

I have seen a jig that someone made (can't remember where now), that was basically a solera for holding the bent sides, with a dished board as the base facing up, and a dished board for the top facing down. The dished boards were pinned in the centre with some way of keeping them alligned correctly, and could be rotated. The idea was to stick sandpaper on the insides of the dishes, and then use them to sand down the top and bottom edges of the bent sides to have the domed profile. It was interesting, and looked like it would work.

Anyway,

I will try to got some more info and pictures up here for the methods I used and the outcomes, when I get the chance.

Matt

Title: Re: Assembly with domed soundboard
Post by Acabooe on Sep 10th, 2008 at 8:42am
Hey Matt,
I would be interested in seeing some sketches about it.
I don't have CAD so I am not sure if that would affect my ability to see them, but if not then could you explain it a bit more?
I have see Mike Chock do something similar to the process you described with putting sand paper in a dished workboard and sanding to make stuf fit, it is pretty neat.
Aloha
Bob

Title: Re: Assembly with domed soundboard
Post by Wood_Butcher on Sep 10th, 2008 at 1:09pm
Matt,

Thanks for the follow up.  I actually understood your explanations.  Your info has been very helpful.  I also have no CAD software at this time, but do appreciate your offer.


Thanks immensely,
Mark

Title: Re: Assembly with domed soundboard
Post by Ukeman on Sep 22nd, 2008 at 11:08am
aloha all,

Thought I'd reply to your domed assembly queries. I use domed workboards and domed assembly boards for this process, 15  for soundboards to 25 degrees for  backs. Sounds like alot but actually if you place a short straightedge across your domed workboard you will see that in a 6 inch length the lowest point of the dome is about a meager 16th inch while in a 12 inch length it may increase to about an eight inch...not much, just enough to keep plates in tension.

Make plenty domed workboards...use one if making spanish style into a holding , assembly jig.

Make one simply a sanding jig place 100 grit stickit sandpaper onto workboard in adjacent rows..or buy a giant disc floor sander 100 grit and contact glue to workboard.

Use sanding dome board for all parts going on to sound and back plates ie: grafts, patches, tonebars and enharmonic bars.Simple way to sand is mark the surfaces to be sanded in dome with felt pen....sand in dome till no more felt pen marks...install under go-bar deck with a domed workboard underneath plate and whatever piece you are gluing on. Always sand in dome and assemble in dome.

If you want to adjust backset or foward set of your neck angle to plate...this can be done at the neck table on your neck, prior to installing soundboard in the flyswatter phase....add a shim to the end of the neck table to create positive neck set, sand off a bit at the neck table to create a negative angle.

In a flat regular holding jig you can insert your bent ribs and fit...mark the showing edges with felt pen and sand with a domed sander until no felt marks. These domed rib edges will be glued to your soundboard ala spanish style in your domed assembly jig to your neck soundboard asembly. Now for the back plate.

Mark rib edges and tentalones ...clamp a domed workboard with sandpaper to work table, pick up assembly jig turn over and sand by rotating on domed sandpaper board till marks gone, fit and assemble back to ribs.all done. ukeman

Title: Re: Assembly with domed soundboard
Post by Wood_Butcher on Sep 24th, 2008 at 2:10am
Hi,

I'd like to pursue this idea a litle further.

Now that I have shaped and glued all of the bars and bridge plate on the soundboard, I have noticed an interesting shape developing.

The lower bout has developed a spherical shape having retained the shape of the dished workboard

The upper bout is cylindrical. It is holding the curve formed by the two braces which run from bass to treble. It is flat from the waist bar to the neck.  I will add that I didn't glue in the sound hole patces yet.

I am sure that the entire top would form a spherical shape if I sanded the sides in the dish and glued the top to them as Ukeman suggested in the previous post.

What I would like to consider is to leave the top in the shape it presently holds by only sanding the lower bout in the dish shape. It would seem to make the neck to body joint a straight fit as if you were building a flat top instrument.

This seems to be a lot like what Likeke was suggesting on page one of this thread.

If this is what any of you are doing, I'd like to discuss it furthe. Particularily to get some ideas on fitting the sides, such as modifying a dish board or whatever you might have tried.

Sorry about the long story, I just couldn"t come up with a shorter way to say it.

Thanks,

Mark

Title: Re: Assembly with domed soundboard
Post by Wood_Butcher on Jan 5th, 2009 at 4:00pm
Hoping to get somebody who is building radiused instruments to engage in an exchange of ideas about building.  Here's a photo of a motorized sander I built.



Another shot with the radiused work board removed.



A close up of the drive mechanism for the work board.



An interior shot of the pulleys to get from 1725 RPM to about 150 RPM.



And a shot showing how I am sanding the sides to match the radius.



Since I am using a Spanish heel, I have glued in the heel block.  Then I sanded the top edges of the sides to match the top.  I will glue in the tentalones and re-sand them to match the contour.  Later, the neck ends of the sides will be trimmed to receive the neck.  I will glue the neck and top together first, and then glue the sides to the top as per the Hanalima book.  I then plan on shaping the back edges of the sides and back tentalones in a similar manner as the top, after which I will glue on the back.

Title: Re: Assembly with domed soundboard
Post by Wood_Butcher on Jan 5th, 2009 at 4:04pm
Ooops.  Hit the enter button by mistake.

Having said all of that like I know what I am talking about, I will have to admit this is all theory and have never done this before.  This is where I would like some feed back from anybody who has had more experience with this  to see if my ideas are making sense.

Thanks,

Mark

Title: Re: Assembly with domed soundboard
Post by Ukeman on Jan 13th, 2009 at 3:49pm
Hey Fellow Domers! Though i'd squeak a bit and add my doming methods to this thread. I make my domed workboards with 15 foot radius for the backs and 25 foot for the soundboards. For guitars these are cool radii, for a tenor ukulele the dome at 25 and 15' radii is very slight, but enough to get the tops and backs in tension. My workboards are used for installation ala spanish style, another is used for under go-bar or any clamping situation to stay in the dome and the last is used for sanding all bars and braces, patches and grafts prior to installation. This means when sanded correctly the bars are never perpendicular to the soundboard but at a slight lean if one sands in the dome. My soundboard to neck table attachment is where i adjust 2 degrees or so to accomodate the dome of the soundboard...if you sand the neck table its such a small area its easy to do and a slight neck back set is desireable.

All my ribs if to be fitted to domed surfaces are not tapered! I bend the shapes, fit and clamp the ribs in a 2 ply thick form adapted to fit over a domed workboard and ribs are then domed and installed to soundboard, which is in a domed assembly jig. The backs after tentalones are installed are fitted and sanded with a domed sanding board and same domed workboard is used to clamp the fitted back plate. If you have a handy shimpo electric wheel or any potters wheel you can take off the  batten plates and install a domed workplate onto the wheel...build a holding device to keep your uke body level and lower assembled uke and ribs to the rotating domed dish on the potters wheel and with 100 grit sandpaper you can dome in 20 seconds....anyway doming is fun   laters   ukeman

Title: Re: Assembly with domed soundboard
Post by Don_Orgeman on Jan 14th, 2009 at 5:21am
Hey All:

Here's a link for a great tutorial on how to make a sanding dish using a router.

http://uketalk.com/luthier-tutorials/domed-dish.htm

Don

Title: Re: Assembly with domed soundboard
Post by Ukeman on Feb 3rd, 2009 at 4:32pm
aloha all message board posters and 'ukulele builders...here is another reason to join the 'Ukulele Guild of Hawaii: Send your paltry 45.00 to the 'Ukulele Guild of Hawaii at PO BOX 894426 Mililani, Hawaii 96789 for you one year membership.

January's issue 2009 included a fabulous Play it foward Tip via veteran Builder Bob Gleason ala Pegasus Guitars and 'Ukuleles who is sending this lateral tip from Pohaku 'Ukulele's Pete Hurney...and the tip is:

Making a domed sanding board by using your drill press!
Awesome...just need an extended workboard on you drill press to accomodate a sanding domed dish..Bob uses a formica workboard to make the top a bit slippery and by indexing the workboard with a centered pin...that mates with the underside center of the sanding dish, think record player the dish will freely spin....mount a rubber sanding drum Bob uses a 2" diameter drum into your drill press..aligned so that it just mates with the outside diameter of your sanding dish and the roating drill press drum will drive the domed sanding dish...Bob simply waxes the formica surface of dish and workboard...Pete Hurney used his domed dish mounted on a lazy susan bearing...this indeed is my next project.....way cheaper than modifying an electric Shimpo Potters wheel....and the tip of the Year...which is the first tip of 2009 from the 'Ukulele Guild of Hawaii!

Re join us at UGH for 2009   good things will happen    laters  ukeman

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