Acoustic Guitar Construction

Ken when you fill with epoxy what kind do you use? I know there are epoxies just for filling voids in wood for boats and the like. Did you have a brand that you like..

I used the System III first, and had trouble with the ratios the first time I tried it. I started using a postal scale to get the ratios right, and never had another problem. I have also used the 60 minute epoxies from the hardware store....you know the ones in the double tubes? Both work well. I think the System III works a little better, sands better, but the other is more convenient to get yer hands on it when you run out. You only need a tablespoon of it to cover the whole guitar....it spreads far. Both have finsihed very clear and with excellent depth and clarity.

Z-Poxy is my filler of choice. I have filled 5 guitars and I am still using the same two bottles I bought over a year ago. The ratios are very forgiving so you can mix by eye, which I like. The amber color of the hardener does not seem to translate onto the wood to any appreciable degree despite what some people believe. And nothing pops the grain of the wood like epoxy. It is great stuff and I have not found it hard to sand at all because you are leaving such a small amount on the guitar, it is simple to level.
There is a really great picture tutorial on this site:
http://www.lenaweelutherie.com/

On the right side of the page, click Luthier Info, then Epoxy Pore Filling towards the bottom.

I have heard a lot of great things about zpoxy, just haven't tried it yet. I will have to one of these days. I tried the colortone waterbased stuff on padauk. Useless.

Here's a nice document from "System Three" --- the mixing ratios seem very, very finicky and they come right out and blame the user if the product fails --- but I guess its has worked fine for some -- I'd like to see compatibility info, I don't think they ever mention using it as a wood filler?

http://www.systemthree.com/reslibrary/l ... y_Book.pdf

When I used system 3 (not on a guitar yet) I bought the little digital scale they had with their getting started kit. I use the scale even for z-poxy. I never had problems with bad curing but I had heard that system 3 is really touchy for the correct ratio.

I've been trained in structural repair on composite aircraft, and from the very beginning we learned to always mix enough resin and hardener to get a reliable mix. Small quantities are difficult to mix in the correct amounts. We needed to accept whatever waste there was as part of the cost of doing the work. It never was considered waste, but unavoidable excess. We also were happy to have the remains of the batch of adhesive to refer to so that we were content that the repair resins set right.

For what it's worth, I've never had a mix problem with West Systems epoxies when we used their pumps for resin and hardener. Always mixed full shots of both and let the pumps take care of the proportions. We do often mix up excess resin, but it always sets as we expect it to.

Another element of epoxy resin reliability, we always mixed our adhesives in new unwaxed paper cups (think ice cream cups) so that no contaminants from a cup with unknown qualities are introduced. And we didn't thin our epoxy mixes. If we wanted them thinner, we heated them. Thickening of epoxy was done with 'system' thickeners which West Systems sells.