Tops and bottoms

[Absinthe]

Okay, time for me to ask a new dumb question. 🙂

This is a 2 part question. 

1. When making a top, what techniques are used to calculate me up with nice thin book matched laminated panels?

2. We've been doing some Reno work and I have a bunch of leftover 5 and 6 mm plywoods. Some of it is just silly underlayment, but some of it is pretty. I will probably give it a try regardless of advices on the topic. But I am curious what people have to say on the topic. After all, I've seen cardboard as an option. :)

 

[NoterMan]

1.  Techniques?  A.  Buy them already 1/8" thin.  B.  Use a bandsaw to cut consecutive slices from a plank and then a joiner-planer to reduce them to 1/8" thin.  
1b.  To actually glue up the bookmatch planks, I use  2" wide painter's tape.  With the 'not so good' side up, lay the planks out on a flat surface like your saw table and butt them together.  Tape them tightly together with a single strip of painter's tape.   Carefully flip the joined plank over and raise the center a bit, opening the tape hinge.  Run a line of Titebond (tm) down the open hinge.  Lower the center, closing the hinge, and wipe off excess glue.  put something heavy (a plank and some books perhaps) on the joint to hold things flat while the glue dries.

2.  Nothing wrong with 5-6 mm plywood except that the veneers are so thin that you have to be careful when sanding, to not cut through into interior layers.  Also you need, of course, fine toothed saw blades so you don't splinter the edges of cuts.   The first half dozen dulcimers I built, years ago, were make from 1/8" mahogany "doorskin" ply. 

[Absinthe]

3 hours ago, NoterMan said:

1.  Techniques?  A.  Buy them already 1/8" thin.  B.  Use a bandsaw to cut consecutive slices from a plank and then a joiner-planer to reduce them to 1/8" thin.  
1b.  To actually glue up the bookmatch planks, I use  2" wide painter's tape.  With the 'not so good' side up, lay the planks out on a flat surface like your saw table and butt them together.  Tape them tightly together with a single strip of painter's tape.   Carefully flip the joined plank over and raise the center a bit, opening the tape hinge.  Run a line of Titebond (tm) down the open hinge.  Lower the center, closing the hinge, and wipe off excess glue.  put something heavy (a plank and some books perhaps) on the joint to hold things flat while the glue dries.

2.  Nothing wrong with 5-6 mm plywood except that the veneers are so thin that you have to be careful when sanding, to not cut through into interior layers.  Also you need, of course, fine toothed saw blades so you don't splinter the edges of cuts.   The first half dozen dulcimers I built, years ago, were make from 1/8" mahogany "doorskin" ply. 

Re-reading my question I am not sure where the word "calculate" came from. I believe I typed the word "come" but that is neither here nor there. 

So to clarify you size everything down to 1/8 then glue-up? 

I was concerned with the idea of running so thin of stock through either the jointer or the planer. I assume my 6" jointer would be sufficient to make up even the widest of dulcimers I have seen. I was not sure if there were special techniques back-plating or sledding the wood when working with the jointer or planer respectively. It is my understanding from some reading that the book matched joint is not so critical since the fretboard essentially covers the whole area where it would be. As for the back, I assume book matching or center strip inlay are simply at the discretion of the maker. 

I have collected some nice woods over time. I assume I can do basic woodworking and joining. Just figured since I haven't worked with so thin of stock, there might be some tricks I was not aware of. 

I am also guessing that, at least in the case of an hourglass, one would do better to gang and cut them to shape for better symmetry before joining them. 

Lastly, all three curved shapes that I have seen appear simple enough to draw freehand given a basic length and widths for the shoulders, hips and waist. (and final fretboard/tail widths. Seems a bent yardstick could be used to effect most of the joining curves. Is there any other magic involved with coming up with the basic shape/pattern. I assume once I make one I like, I could trace it onto something to keep to simplify the next one.  

[KWL]

I tend to make my tops and bottoms 0.10 inch think or 2.54 mm, but I have a thickness sander.  I pretty much use the same technique as Noter Man for joining tops and back except I use clear packing tape instead of painter's tape. I have found that it does not tear the grain of the wood when taking it off. The same technique is used for joining when you have a center strip. Whatever you choose to use as a center strip is a personal choice.

I always join rectangular boards and but the shape out after gluing it to the sides using a flush cutting router bit. I make a template of the shape (hourglass or teardrop), but only one half of the dulcimer. I lay it along the centerline of the joined top or back, trace the shape on one side, flip it over and trace the other side. My templates are made out of thin plywood or plexiglas.

Ken

"The dulcimer sings a sweet song."

 

 

[Absinthe]

1 hour ago, KWL said:

I tend to make my tops and bottoms 0.10 inch think or 2.54 mm, but I have a thickness sander.  I pretty much use the same technique as Noter Man for joining tops and back except I use clear packing tape instead of painter's tape. I have found that it does not tear the grain of the wood when taking it off. The same technique is used for joining when you have a center strip. Whatever you choose to use as a center strip is a personal choice.

I always join rectangular boards and but the shape out after gluing it to the sides using a flush cutting router bit. I make a template of the shape (hourglass or teardrop), but only one half of the dulcimer. I lay it along the centerline of the joined top or back, trace the shape on one side, flip it over and trace the other side. My templates are made out of thin plywood or plexiglas.

Ken

"The dulcimer sings a sweet song."

 

 

Thanks Ken:
Sometimes I just need to talk things out and think aloud. I would feel more comfortable working thin wood with a drum or big belt sander than a jointer or planer. But I don't have one of them, so I would simply plan on using what I have. I assume it should do well enough since it is not directly working endgrain and I can go in small increments. 

I will have lots of this plywood to play with since there are so many 9" offcuts from this project. I can think of them as prototypes 🙂 My only concern now is that if I do an overhang, I will have the plywood sides exposed. I am thinking of either working some "edge banding" or perhaps edge paint, into the design. I don't think my current skills are up to doing binding and perfling but, hopefully, I will get to working with real wood soon enough. I also haven't seen too many calls to kerfing strips either, but I will see how that feels come time to assemble. 🙂    

[NoterMan]

I have used a sled when planing down thin stock' and very thin passes.  When I had access to a bandsaw set up for re-sawing, I simply surface sanded slightloy thick sawn planks.  The best tool, IMHO is a surface sander, but not many folks have that.  

Kerf strips are really necessary if you want to explore edge binding on plywood bodies in particular.  A few times I have used a 'surface binding" to make it look as though the instrument had overhanging "fiddle-edges" as they are called.  Just a narrow/thin strip glued on the outside, to cover the plywood "grain" of the top ply plank

.   Otherwise, kerf strips aren't used much these days, as modern glues need less surface area for a good joint than hide glues.