Matthew's cornerless bass project - Page 4

**Matthew Tucker** · #61 12-06-2007, 01:17 PM

Quote:

Originally Posted by Jake deVilliers

Gee, that's a big guitar!

Oh shut up!!!

Don Harris · #62 12-06-2007, 03:06 PM

What are your plans for the top graduation?

Ken McKay · #63 12-06-2007, 03:53 PM

Matthew, try not to cut any more corners on that project

KSB - Ken Smith · #64 12-06-2007, 08:53 PM

Quote:

Originally Posted by Matthew Tucker

Oh shut up!!!

No, it's not a big Guitar. It's a Bass Guitar and I also play one like that but it predates electricity by about a century or so..

**Matthew Tucker** · #65 12-06-2007, 10:20 PM

top transverse arching is based on curtate cycloids. haven't settled my long arch yet, it started out with a cycloid curve to centre of upper and lower bouts, then a flattish section joining the two. but I'm modifying that as I go. the cycloids have a low point at about 2cm from the purfling edge. varies a bit.

Graduation will probably be much as I did for the "Sirente" bass, 12mm under the soundpost, 10mm up the centre and going to about 6mm at the recurve point, then 7mm at the edges.

I stopped working on the top for a while as I needed to finalise my outline. Even with linings in, its a wobbly thing. I have glued taquets to the inside of the rib and hold the inner bouts from springing out with a piece of wire. you can see it in the pic. just.

**Matthew Tucker** · #66 03-11-2008, 07:20 AM

Well, here after quite a hiatus are some updates.

I forgot to cut the neck mortise before I removed the garland from the mould, and this meant I had to clamp the whole garland to a piece of thick plywood to hold it steady while I shaped the mortise.

Tonight I glued the back to the ribs. It is a bit tricky with a cornerless bass as the ribs are a bit floppy. You can clearly see the wire holding the waist together, a necessary addition. I'll remove the towers later.

Actually they are pretty boring photos but at least it's progress. I have the scroll progressing well but I have not touched the top for a while as I wanted to finalise my outline better before locking off my top arching. And I needed to glue the nack on to be sure what outline my front is going to end up with.

**Matthew Tucker** · #67 03-11-2008, 07:38 AM

And here's the floppy ribcage getting its neck cut ...

tyb507 · #68 03-11-2008, 11:56 AM

Just curious if there is a practical reason to remove the mold (or mould) before you glue the back on. Wouldn't leaving the mold in until the back is on take care of the "floppy rib" problem?

Jake deVilliers · #69 03-11-2008, 12:06 PM

You took the words right out of my mouth Tyb.

I have no experience with a cornerless bass but guitars are pretty wiggly until the back is on.

Because the garland is so floppy, its easiest to glue the back on a guitar by putting spacers under the sides while it is still in the mould. Just prop it up, glue the back & clamp over top.

Jake deVilliers · #70 03-11-2008, 12:14 PM

Hey Matthew,is that a laminated tailblock or just a couple of bands of linen?

Bourgeois has been using plywood for their guitar tailblocks for a few years now and its really cut down on the cracks, although they orient the plies 90 degrees from yours.

**Matthew Tucker** · #71 03-11-2008, 02:10 PM

it's a laminated tailblock. Time will tell if its a good idea or not.

I can't remember when I removed the mould, or why, actually. one reason for getting the mould out is that if you leave the mould in after the linings go in you can have a helluva time gettin the mould out again, even with floppy blocks. But I actually think I glued the linings in while the thing was in the mould. I just can't remember!

Jake deVilliers · #72 03-11-2008, 02:34 PM

Oh I get it, you have an internal mould.

I think its easier to build cornerless instruments with an outside mould. Then you can glue in the linings in the mould with impunity and its easier to attach the back too.

Looks good Matthew!

Do you think that the floppiness of the garland will add bottom to the sound?

tyb507 · #73 03-11-2008, 03:18 PM

I've been taught (regarding violin construction, not particularly bass) to make the rib structure up to gluing the back linings in, glue on the back and remove the mold through the front. Then the structure is made rigid by the back, and you can proceed with the top linings.

**Matthew Tucker** · #74 03-11-2008, 03:48 PM

Jake - more bottom? I have NO idea! The lower bout might look more like a bum though.

External moulds make sense too but they take up a lot more room.

tyb - yeah that makes sense, but it doesn't always fit with my schedule. In this case, I needed to wait quite a while for some dry weather before gluing my back braces, and I couldn't just wait around doing nothing!

This bass is assymetrical and I like it that way. Part of the fun is seeing what shape it ends up.

**Matthew Tucker** · #75 03-17-2008, 03:36 PM

Here's a few shots of my outside arching based on curtate cycloids and a 32mm max arch height from top of edge to top of arch.

The long arch is based on traditional italian arching the way that I interpret it.

**Matthew Tucker** · #76 03-17-2008, 03:37 PM

Its hard to convey the shape with photos. And I can't post any more because my image attachment limit has been exceeded (only 3Mb in 6 years!) and I don't have a good free hosting alternative at the moment.

If you look carefully at the last pic you can see some nice grain defects almost like "bearclaw" in the cedar. unfortunately these will largely be hidden by the fingerboard ...

**Matthew Tucker** · #77 03-17-2008, 03:53 PM

here, courtesy the ANZ luthier's forum:

I am pulling a very nice corduroy effect with scrapers. I think it is going to look, as people say, "killer".

Jake deVilliers · #78 03-17-2008, 04:19 PM

Nice shape Matthew. Nice deck too.

I'd love to see higher-resolution pix.

If you want, I could post them on the Gallery section of my website.

Ken McKay · #79 03-18-2008, 11:42 AM

Quote:

Originally Posted by Matthew Tucker

Here's a few shots of my outside arching based on curtate cycloids and a 32mm max arch height from top of edge to top of arch.

The long arch is based on traditional italian arching the way that I interpret it.

Matthew,

It was nice talking on the phone the other day...My 15 year old son, who answered the phone was imitating an Australian bloke who makes basses for the rest of the day. "Right then, thats a pretty good specimen [like Steve Irwin], a beautiful piece of wood...etc etc

Those plates look very Curtate-ish. I am wondering if you measured the way I would have though. Do you recall your numbers?

I think I would do it this way. Did you put h at plate thickness at the total height of 35 minus the thickness at the recurve? It is subtle but a real difference.

**Matthew Tucker** · #80 03-18-2008, 02:38 PM

Crikey mate ... Stone the bloody crows!

I don't remember exactly. I think I calculated the arching height at the point I wanted to draw each curve (not counting plate thickness) then made the width of the cycloid the plate width minus 4cm (2cm each side) and generated the curve with 15% over-run to give the recurve shape. I think my final arching is close to that for most of the curve but the recurve is flatter than the generated curve. This cedar is quite flexible in the lateral direction, and soft at the edges too. I might take it down a bit after I hollow the back and get the purfling in.