I’m building a harp (from a kit—if you’re interested, check out harpkit.com for harps and other nifty DIY musical instruments). I goofed, and I sanded through the top layer of the soundboard. It’s birch, so it’s very pale wood. The next layer down is darker, so now there’s a dark patch on the soundboard. Is there any good way to fix this? I thought about painting something over it, but my painting skills are not good, and it might end up worse than it is now.
One more small question—I need to fill in some screw holes with little wooden plugs. The plugs are a tiny bit too big. It’s going to be hard to sand down either the plus or the holes. Does anyone have any other ideas?
Get some wire clippers and a sharp chisel and appropriate sized dowel stock.
Use a pencil sharpener to put a point on a piece of dowel, then stuff the tip in the hole with some glue, and clip it off with the wire cutters just above the water line.
Once the glue is dry, it is possible to trim the remaining bit flush with the wood if you hold the flat side of the chisel blade completely flat against the surface and work the end of the chisel in a slicing motion across the peg.
At that point you can lightly sand in the direction of the grain using a sanding block to prevent you sanding a divot.
It sounds like the soundboard is veneered and you’ve sanded through the veneer. Technically this is what’s known as an “oh shit” situation. It’s one of those mistakes that is really not easily repairable. I doubt you’re going to be able to achieve a good looking repair, but here are some ideas:
You could try to find a piece of veneer that you like the look of, and cover the entire panel. This will have some small effect on the tone. Alternatively (my favorite idea) complete the kit and find a local artist to cover the soundboard with a scene or a design - this will instantly boost your project out of the “kit” category.
Forget power sanding - wrap your paper around a wood or hard rubber block.
And what Minor says - practice everything you possibly can on scrap. And get that chisel sharp.
Thanks to everybody for the helpful information. I can’t replace the soundboard or add another layer if veneer. The soundboard is glued and nailed to the body of the harp, and wood strips are glued around the edges.
Dyeing the soundboard is a good option. I have thought about dyeing the whole harp—purple, or maybe green—but natural cherry is nice, too.
You could leave the dark patch and make up some outrageous story about how it got there. You know, it got grazed by a micrometeorite or a homicidal maniac attacked you but missed and his knife hit your harp. Something like that.
Are the screw-hole covering plugs just dowels? If so, and if you have enough material, you can just chuck a dowel into a drill press, set it to low speed, and use medium grit sandpaper to slowly reduce the diameter of the dowel until it fits properly.
If you don’t have a drill press, I imagine you could rig something up with a hand drill that would get the job done, although more awkwardly.
I think the whole veneer problem has been very adequately covered by others.
The plugs are pre-cut, so I don’t have much to work with. I can’t use a generic dowel, because it wouldn’t match. I’m going to try to sand those little suckers down, and if that doesn’t go well, it might work to glue them to another dowel so I have something to hold on to.
Another question: I’m finishing the harp with a wipe-on polyurethane. The can I have is a little old. Does it go bad, and should I buy a new can instead of using the old one?
How old? I’ve used wipe on poly for a few guitars and it works well. If it is too thick you can thin it with paint thinner, as many thin coats are better than a few thick ones. If it’s more than a few years old I’d go buy a new one. I would also have a look at a few luthier’s forums for ideas as guitar manufacture runs into a lot of the same problems.frets.com or Stewart Macdonald’s tutorials are good places to start.
I’m still working on this darn thing. I’m almost ready to start finishing.
I have one little issue I could use some advice on. The soundboard has a strip of wood that’s about 1/8” thick glued around the edges. I had a little trouble with the glue, and I have some very tiny bits of glue where the trim meets the soundboard. I’m just wondering, how clean does that have to be? Is a little bit of glue going to cause a problem with the finish? I don’t want to be too aggressive with it, because I don’t want to sand through the top layer (again).
Any glue that seals the wood will be visible as lighter patches under the finish.
Wet the wood with a rag dampened in mineral spirits in order to get an idea of what it will look like when you apply finish. This will show you if you need to worry about it or not.
If the glue is higher than the wood surrounding it, you can use a luthier’s trick and put tape on a razor blade, leaving only a quarter inch or so of the blade in the center unprotected, and then use this center section delicately as a scraper, held at a steep (almost 90 degrees) angle to the wood.
Here’s a bit of a videofrom Rosa String Works that shows kind of what I’m talking about with the razor blade.
He’s lowering the purfling by using a razor blade as a scraper. This time he hasn’t taped the blade on either side of center, as he often does, but his videos are numerous and long, so I couldn’t find one where he did that.
That is good info. Thank you! I can’t see any glue spots with the mineral spirits, so I think I’m ready for the next steps. I’m going to try to decorate it a little, and then I can finish it and put on the hardware (36 strings, with tuning pins and sharping levers). Almost there!
A small update on this. It took a while to work out the best way to do the finish, but it’s finally almost done! I’m installing the hardware, and if my drill battery isn’t dead, I’ll be done with that this weekend. Then I can add the strings.
Thanks to everyone who gave me advice. It was very helpful. The finish isn’t perfect, but it looks fine as long as you don’t get too close, and I don’t think it will peel off, so I’m happy with it.
