Post any mistakes you have made, or successful things you have tried.
With each instrument you build, only change one significant variable. Neck angle, oval hole/ff-hole, parallel bracing or transverse bracing, etc. Don't combine more than one major change into a single instrument. Tops can be thicker than you think they need to be. All my first dozen or so instruments had tops that were too thin. I thought it would make them sound good. Less mass = more sound, right? Wrong. If it's too stiff, you can always remove mass from the outside if needed. The back you can basically make as thin as you want on an ff-hole, parallel braced model. Down to .090" in the recurve. I've done .070 in the recurve. It's not a structural problem after 9 years. Oval-hole instruments should have thicker backs. However, I have made instruments with smaller bodies (less air volume) and thin backs, and they sound great. If I had a "normal" sized air volume on an oval-hole instrument, I would make the back thicker (.100 in the recurve). That said, the bracing can probably be a lot lighter than you think it needs to be. 1/4" thick and 1/4" high is about all it ever needs to be. Transverse braces can be nearly 1/2" high, though.
What's that in real measurements Marty? I mean millimetres? Just kidding - I'll multiply by 2.54. We changed over to metric here in the 70s so I can't think in inches any more. I carved my first top (an oval hole) too thin around one edge of the soundhole. The mandolin tried to bend in half. It's still playable and has a great tone but I have to do some major surgery on it - maybe next year. The latest top plate I really did by feel and it has ended up 5.3mm in the centre going down to about 3.5mm at the recurve. Holding it up to a strong light reveals fairly even graduations.
Heh, yes, Peter. Everyone in the US still uses inches for everything related to manufacturing. It's because all the Bridgeport mills are all graduated in inches, and all the collets come in inches, and all the cutters come in inches, and all the verniers are in inches.... it's going to be a long time before it changes. I work on scientific projects a lot, so I can go back and forth pretty easily, but English is home base. 5-6mm graduated to 3.5mm at the recurve sounds like it's right in the ballpark. By too thin I mean like 2mm thick in the recurve, varies depending on the sample of wood, of course. (Though the crown is where most of the strength comes from).
Yeah the aviation industry worldwide still use inches because so much of the manufacturing (especially by boeing) is based in the US and a worldwide standard is essential. Never heard of a bridgeport mill before you mentioned it (just googled it). The English went metric in most things quite a while ago BTW.
Just posted some questions on tru-oil finish in builders and repair but thought I would share here as well. I'm about a half dozen coats into a tru-oil finish and not quite happy with it. I have good coverage and nearly have a mirror finish and glossy shine except for a bunch of pesky lint in the finish. I suppose I will have to sand a bit and find a way to keep the lint down. Any suggestions are welcome! Pictures can be seen in a photo album in my profile.
Are you giving it lots of time between coats? 0000 grade steel wool may be good for the lint.
I wet sanded using a little mineral spirits to get through all the fuzzies and have now re-applied a couple coats sanding with 1000 and 1500 grit wet or dry. Sanding wet keeps the dust down and allows me to wipe off most of it with a paper towel. I then wiped the whole thing down lightly with a tack cloth. Waiting 12-24 hrs between coats. Starting to shine now! https://www.dropbox.com/s/p9s0jdcl79...2020.28.34.jpg
Ah - now that does look impressive. I can't remember if you posted a soundclip of it in the white. If not, please post one when you finish it.
That is a very promising finish, Aaron. Interesting to see you achieving such a high gloss with an oil finish.
