| 2. Assembling the Harp Parts | Once the pieces were cut, planed and sanded to some extent, I approached the problem of assembling them. When building mandolins, I use a form to hold the pieces together to achieve the correct orientation, at least to start with. In the plans there was nothing about this type of approach, so I was forced to fall back on clamps and elastic largely. | |
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The plans recommended a
plywood soundboard, but I decided that a proper tonewood one would be
much better. I bought a jumbo folk guitar top.
On a harp, the grain on the soundboard should run from side to side, the string pressure running up the centre of a harp means that it cannot run vertically. In order to get the grain on the guitar top correctly oriented for the harp, it was necessary to cut it into several pieces. |
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Here the pieces are roughly
arranged to show the rough soundboard shape before gluing. The
joined edges of the sound board
pieces must be perfectly straight.
Here I am shaving them down in pairs on the shooting board prior to gluing.
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Having checked to make sure that the
edges match perfectly, I glue on a gluing board, with a batten
beneath the join. Having pinned both sides with nails, (not through the
board, just outside it...) and loaded the top with
weights, I remove the batten. The weights push the two pieces down and
together while the glue sets. (You need to check they are the same
thickness before gluing, or it will not leave you with a good flat join).
I glued the top 2 sections and the bottom 2 sections like this. |
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Gluing the two glued halves of the soundboard was a little more difficult, as it is really too long to fit into the gluing board. So, having checked that the edges matched, I clamped the two halves between 2 boards, (plastic to stop squeeze out from gluing the top to the brace boards) and applied pressure with several large elastic bands. | |
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Before assembling the sides,
it was necessary to make slots at the front and back inner edges, so
that the soundboard and back can be slid into place. This proved quite a
problem, because according to the plans, the slots had to be angled to
5* in at the front and 5* back in the back. The sides are not square relative to the front or
back! Eventually, after several abhortive dry-runs, I came up with an
adjustable router fence, that would angle backwards and forwards, and a bit that would do the job. (Not the first
I tried...!)
The top needed to be routed in the same way, to accomodate the top of the back and front panels. |
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| Router fence plans here. | ||
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The cutting of the back was
relatively simple. It was constructed in a similar way to the front,
from 2 pieces of guitar side wood, though this time the join was down
the centre.
Having marked out the access holes, I drilled a hole at the end of each to enable the saw entry. |
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The only problem, as illustrated in the photo, was that the fretsaw was not long enough to reach all the way down the hole. The only solution was to cut each end as far as possible, then cut the missing bits with an ordinary saw. | |
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Once cut out, the centre join was then re-enforced. There will be considerable outward pressure on the sides, which will be held in place partly by the back, so I didn't want the back giving way. | |
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In the plan, part of the frame
is secured with screws, through the bottom, as well as glue. With the help of clamps and
elastic, it was possible to hold everything in position while the glue
set, not easy as no angles are square, and the clamps slip easily. Here is the box frame
assembled.... top bottom and 2 sides.
In the second harp, I decided to omit the 4 screws through the bottom. |
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As the delicately angled joins were not altogether
perfect, I decided that the whole structure would benefit from a little
interior re-enforcement. I glued a small piece into each corner.
Then, final sanding..... by hand.
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One of the most awkward parts of the
construction, was the fitting of the arm on top of the head. A concave
section at the end of the arm needed to fit over the convex top of the
head. Both had been carefully cut by hand, but even so, the match was
not altogether what I would have wished.
After several abortive efforts to sand them 'together', I finally hit upon the idea of curved sanders. (No file was big enough!) I found a piece of drain pipe that was exactly the radius that I needed. Helpfully, at the end of a section of drain, a pipe widens, so the next section can fit into it. I uses the wider end to fit the sandpaper inside, and the narrower end for outer paper. In this way, in theory, I could sand 2 matching curves. Her is my 'one-off' head sander. |
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The arm and pillar were attached with the aid of 2 dowel rods, inserted into pre-drilled holes in both. Plenty of epoxy resin should ensure that they stay together. It was necessary to leave it clamped up in the vice, with the pillar pointing directly upwards in order to get it to set in a good position. It was too awkward a size and shape to clamp up otherwise. | |
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Sanding this piece was a little difficult, as it is quite large and ungainly. But it was possible, once I experimented with a variety of different clamping positions on and around the workbench. |  |
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Trial fitting the front............ It slides from the
bottom, up into the slots routed in each side. As the slots are only
3-4mm deep, I did not want to over-cut it, so fitting took several
attempts, until it fit snugly.
The back was the same, only slightly easier to manipulate on account of the holes. Once ready to glue in place finally, both front and back are pinned in place at the bottom. |
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Before the sound table is fitted, the
string holes need to be drilled.
Marking out for the string holes. |
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Holes are drilled. | |
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Once assembled, it remained only to stain
the wood. I used water based dyes, that wouldn't react with the Tru-oil
finish I intended to use. I did not stain the back or soundboard.
Once stained and assembled, it looked like a harp at last. The foot of the pillar is held in place by a screw from underneath, but the top arm, is held solely on the box top by string pressure. Thats the next bit........... |
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| 1. Construction of Harp Parts | 3. Finishing the Harp | |