Building a bentside spinet

[Charlie Schultz]

This will be based on the Keene & Brackley 1715 spinet, described in John Barnes' book "Making a Spinet".

First up, the form for making the bentside. The bentside 750 mm long, 176 mm wide and 9 mm thick (tapers to 7.1 mm at the towards the sharpest part of the bend). Barnes makes the case that the wood was typically just soaked in (cold) water and bent on the form. This is my interpretation of the bending form (minus the hold down clamps).

The walls are a couple layers of 15 mm BB plywood, with 1.25" dowels for the spacers (using 12" bolts through the dowels to old it all together).

My plan is to soak and use a hot air gun.

Questions
1. Should the outside walls of the form be beyond the edges of the side? Or should the edges of the side ride on the outside walls.
2. Do you think SuperSoft would help?

[Barry Daniels]

Supersoft should work. Are you using veneer?

[Charlie Schultz]

Plan 'A' is full thickness. I plan to use cherry for the case and lid, poplar for the baseboard and spruce for the soundboard.

[Barry Daniels]

Supersoft works well on guitar side thickness (0.080") but much thicker than that will be less effective due to the lack of penetration. I recommend resawing the wood into thin layers and doing a bent lamination. The other option would be making a steam box.

[Charlie Schultz]

I misinterpreted John's bending form, I think this is more like it:

The board to be bent rides on top of the cross pieces.

[Barry Daniels]

Either form should work but you would actually get more support on the first one due to the form's edges also contacting the wood during bending. This is just the way that a Fox Bender form works.

[Charlie Schultz]

If I was going to do laminations, the first one would be the way to go. But I wanted to try bending full thickness.

Here's my form (wood to be bent is leaning up against the back):

And the bend:

I don't think my heat gun was quite up to the task (it could not keep a big area hot) so I wound up pouring boiling water on it for a while (and bending slowly). Per the plan, this form should overbend the side to account for springback. I will leave it in the form while I work on the baseboard (case bottom).

[Charlie Schultz]

Here is the baseboard. It is poplar, about 0.5" (12.5mm) thick. The bentside (on the right) still needs to be trimmed. Barnes recommends waiting until the case is ready to be assembled before trimming it (the baseboard) to match the actual bent side. The long edge (back) is about 1.7m or 68" long. The long rectangle in the front is where the keys will be.

[Charlie Schultz]

Here is the wrestplank or pin block (what holds the tuning pins). I've used maple, 3.4 cm (1.3") thick. It will sit just in back and above the keyboard- you can see the left edge follows the baseboard outline. It will sit about 3" above the baseboard, allowing the keyboard levers to go underneath.

The jack guides are next and they are a bit involved (and there are about 30 of them) so it may be a week or two before the next update.

[Charlie Schultz]

I'm working on the jack guides and doing it a little different than the book. The jack guides are built up from a pattern of notches in the wood, then the wood is cut into the individual blocks (we need 29 of them). In the book, the notch borders are cut with a handsaw and then they are chiseled out to make the grooves. I'm going to use a tablesaw instead.

So here is a photo of the notches cut in some cherry that has been planed to a thickness of 12.3 mm. If I had a wider piece of cherry, I could have repeated the pattern horizontally. After the notches are all cut, the length is cut into 29 mm long blocks.

Next, a little jig is made to hold the blocks (now standing on edge). You can see that the notches on the back side line up with the notches on the top to create the jack guide. The angle (nominally 26.5 degrees) will vary slightly depending on the actual thickness of the cut. We need the octave span to be about 165 mm.

Here's a group glued up. I glued up 7 - 9 pieces at a time, then glued them all together. Next I need to cut off the top and bottom so we have a flat surface to glue to the wrestplank.

[Charlie Schultz]

Jack guide with edges trimmed off, just about ready to be mounted to the wrestplank

And glued to the wrest plank. The bass & treble ends have been squared off and a slight (2 degree) bevel was added to allow the jacks to move easily in the guides. The top surface of the guide is planed smooth with the top of the wrestplank.

[Eric Knapp]

I'm really fascinated by this. I'm really looking forward to seeing it develop.

-Eric

[Charlie Schultz]

I added the soundboard liners around the jack guide/wrestplank assembly- this is where the soundboard will attach to the jack guides. Sort of like kerfing on a guitar except it's not kerfed and it is a bit lower than the guides (so that the top of the soundboard will be flush with the guides and wrestplank). Per the drawing, the soundboard is 1.55 to 1.75 mm thick along this edge.

Next I cut the baseboard liners and put them in position (but not glued down yet).

Then here are a couple photos of the wrestplank assembly sitting in its place. I still have to add a couple spacer strips between the wrestplank and baseboard.

I need to read a little further ahead before I glue things down here- there are still some things shown on the drawing that I don't get yet.

[Charlie Schultz]

Some questions for anyone that might know...

There are a couple of "sloping" shelves shown on the drawing, but I cannot find any reference to them in the booklet. I'm not sure what their purpose is. The first is shown in the following drawing- the sloped wedge on the right baseboard liner, presumably right in front of the wrestplank assembly.

Perspective

From the plan

The second "sloping" shelf looks to be the horizontal baseboard liner shown in the drawing below. Now, it does slope left to right, but the booklet clearly says this liner is glued down but the plan notes that it is just nailed. So perhaps just the top is sloped? Or I'm just misinterpreting?

Top view

[Charlie Schultz]

One of the folks over on the hpschd-l mailer clued me in. There is another thin board that slopes upward from the baseboard liner to the back of the wrestplank assembly and it basically encloses the keyboard area. He also pointed out that you can see a small portion of it (now that I know what to look for) in one of the photos on John Barnes' web site.

[Bob Francis]

This is fascinating.

[Charlie Schultz]

Sorry for the lapse, it's been busy.

I got the case pieces all planed to thickness and at least rough cut. Here's about how they go:

Per the book, I'm starting to fit them from the front, winding up with the long back piece being the last to install. Here is the detail on one of the sides that goes next to the keyboard:

You can see a rabbet along the bottom edge- there is a long, thin piece of spruce that goes from the front to the back of the keywell for reinforcement. I think the historically correct way was to not rabbet the piece, but instead add a veneer (pecan) the same thickness as the spruce strip.

So I got the left side cut to proper lengths and mitered and I started on the right side- got the first two pieces done ok but now it was time to add the curved piece (which has been sitting in the bending jig all this time). Unfortunately, the bend did not come out well enough. 90% of it fit well, but the last 10% (the end nearest the keyboard) was significantly under bent. Not sure yet what I did wrong, but I steamed it last night and put it back in the jig- we'll see tonight if it's any better.

[Bob Francis]

This is totally fascinating and WAY out of my league.
Thank you

[Randy Roberts]

I'm with Bob and Eric in being really interested in this project you're tackling.

If your bent piece ends up not working out, I definitely would vote for doing it as a lamination next try. It would be a lot more structurally stable I think.

Where did you source your spruce for dimensions large enough for the soundboard?

Have you found a forum of similar builders you can draw on? If not, you ought to add a new category here for keyboard instruments.

[Beate Ritzert]

Where is the applause button? I am really fascinated.