Sunday, February 5, 2012

a harp starter

The harp that I'm to build has begun its life as a plywood template of the neck. There are lots of places I could have started, but for me it felt important to get the feel of the neck because it will determine both the engineering of the harp as well as establishing the flow of it's appearance (or not).

One of my older posts from the guitar build expands a bit on my feelings about bringing all parts of an instrument together, and seemingly 'working all over the place' in the process. It is:

Anyway, this template is derived from a drawing done by Rick Kemper of Sligo harps, and I acknowledge his technical advice and his design. He has been generous in his support, and if we weren't half a world apart, I'm sure we'd have some creative fun together. So, I started with a tracing of his suggested outline, but in these things (if you care about lines) the curves need to be tweaked and nurtured into a harmonic path. Even a perfect master drawing will become a bit  wobbly in the most fastidious tracing, and as well, I like to create my own little nuances here and there.

So the template is as much about getting to know the curves and their purpose as it is about having a master shape with which to make the real harp. Most of you will see in the pic above that the curves are still a bit rough and wobbly, and I'm working on them now, between typing things. The curve is set by the string length and the thickness is established by the strength required at a given point and by the need to have enough wood there for pins and levers.

For those who can't see what all the fuss is about, the pic below highlights  (I think) some of the blunt or dead spots on my curves so far. The knife is pointing to a place where the two curves begin to spread. The inner line comes out too fast, and then flows into a line that is too straight. On the outer curve (indicated roughly by the pencil) there are bumps and hesitations.

Now in focussing on these things and  spending some hours on the template, I get a side benefit in that I'm becoming familiar with the whole project and am beginning to own it.

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  1. I get it, the working all over the place thing.

    Rob what do you use for drawing curves patterns etc. I have a cheap french curve set but have always wanted a set of ship curves are there instrument curves.

  2. Hi Mike. For small curves I use french curves too, but for something like this I was working from some arcs radiating from the centres of the string pins, and freehanded to join the arcs where they intersected with my proposed line, then cut with bandsaw then made it fair with spokeshave, mini planes and sanding sticks. The pattern given by the designer is very good, and you could just trace with dots made from a pointy tool, then fair it all up.
    For the boats I used a disgusting array of bits of oregon and hardwood as springy battens, always meaning to make a nice set, but managing with scraps of stuff anyway...
    Love the floor structure in your Coquina, by the way. Absolutely top work!

  3. Oh, and I missed the last p[art of your question about instrument curves. Cello violin etc outlines can pretty much be plotted by intersecting arcs with centres at proportional intervals. There are lots of methods and even more theories, but they all start with the application of specific ratios and relationships, so it can nearly all be done with a compass.