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Need suggestion for coating for fretless aluminum neck
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=24457		 Page 1 of 1
Author:  xplode [ Wed Nov 04, 2009 4:29 pm ]
Post subject:  Need suggestion for coating for fretless aluminum neck
I'm new here so let me preface this post by saying that I am not a luthier . I am a metallurgist that likes to play music and build/destroy/modify things.

That being said, your probably going to cringe when you hear that I sanded and rough-polished my ovation's cast aluminum neck. There's more than one thing wrong with that statement, no?

So... Ovation in their infinite wisdom in the 70's or 80's (wild guess at the age of the guitar) made some interesting materials selections for this model. They seem to really like casting because this model features a cast polymer shell (sides and back), a cast aluminum neck (yes they cast the frets and the fretboard all together and then painted the fretboard part black. The neck is a cast polymer foam molded right onto the back of the fretboard. In fact the only two pieces of wood on the whole thing are the bridge and the top, both in pretty poor condition.

Anyway, I've been thinking about trying fretless for a while and figured it couldn't hurt this guitar to lose some frets. It had already lost all the fret marker inlays. When I went to try to knock out the frets I found out they weren't set in plastic like I had assumed for the past 6 years of ownership, but that they were, like I described above, cast aluminum.

This was great news to me as I get along with metal a little better than wood, or plastic for that matter. Not enough practice I guess. So I have the neck polished down and the fret marker holes filled with epoxy. There is very little relief as you can see in the attached pictures.
Attachment:
fretless reduced.jpg
Attachment:
closeup reduced.jpg


My questions are:

1) What can I coat the neck with to prevent oxidation and scratching?

My first guess would be polyurethane but again, I am no luthier.

I realize that the coating will color the tone just as the fact that the aluminum fretboard is the reason the guitar has sounded so dang bright. The fretboard in its current state will probably make the O sound twangy.

2) How much would a few coats of poly darken it down?

3) Can I use something harder without worrying about chipping from "normal" use (bending, vibrato etc.)?

All constructive comments will be greatly appreciated
Author:  Hank Mauel [ Wed Nov 04, 2009 7:24 pm ]
Post subject:  Re: Need suggestion for coating for fretless aluminum neck
A couple thoughts come to mind since the neck is separate from the body at this time:

1. Anodize the entire aluminum neck...all sorts of colors to choose from, even black.

2. Use an automotive finish paint system of some sort...etch/prime the aluminum, spray base coat(s), then clear coat. This would allow you to make the neck shaft a "brownish" color like mahogany and then mask off and spray the fingerboard black, like ebony. Heck if you're really creative you might even "faux" the neck shaft to give the appearance of wood grain. [:Y:]


Ok...I'll go back into my den now to hibernate. :lol:
Author:  Tim L [ Wed Nov 04, 2009 7:36 pm ]
Post subject:  Re: Need suggestion for coating for fretless aluminum neck
Hard black Anodize is one of the hardest materials out there but it won't give you much of a damping effect.

Tim
Author:  Bob Garrish [ Wed Nov 04, 2009 7:38 pm ]
Post subject:  Re: Need suggestion for coating for fretless aluminum neck
If there's any way to separate the fretboard from the back of the neck, my first instinct would be to anodize it. It might require anodizing or an etch at least to get any sort of finish to stick, though a hard anodize (Type III) would work wonders for durability AND come out black.

I've got no suggestions so far as finishes go, I think they'd all wear eventually. Definitely nothing in the range of the lasting power of a hard ano.
Author:  Mark Groza [ Wed Nov 04, 2009 7:53 pm ]
Post subject:  Re: Need suggestion for coating for fretless aluminum neck
You might want to consider useing a NiSi coating like they use for cylinder walls of aluminum chainsaws.It's pretty well indistructable and shines like chrome.They have it in arisol cans for spraying.It's more durable than even the chrome bores they use in alot of high rpm engines.
Author:  John A [ Wed Nov 04, 2009 9:03 pm ]
Post subject:  Re: Need suggestion for coating for fretless aluminum neck
What about adding a wood veneer ? not sure how you would glue it - but I think it would be nice. I doubt anything will get rid of the twang.
Author:  xplode [ Thu Nov 05, 2009 1:10 am ]
Post subject:  Re: Need suggestion for coating for fretless aluminum neck
All,

Thanks for your suggestions!

I decided to go with some spay spar poly because thats what they had at the local hardware store and I want to keep the shiny finish. We'll see how it holds up. As for anodizing, I wont be able to remove the fretboard from the neck (if I want to be able to play it again) and anodizing involves a nice acid bath, so that's out. :( If I started making guitar necks tomorrow out of aluminum, I would definately anodize them but my plastic neck is melted in/on to my fretboard.

I will have to look into Mark's NiSi coating although I would expect high temperatures and more acid will likely be involved.

Attached is a picture of the coated neck. The lines where the frets would be are caused by differences in the solidification structure of the original casting. I thought that was a cool coincidence.

Cheers,

Collin
Author:  mateo4x4 [ Thu Nov 05, 2009 11:04 am ]
Post subject:  Re: Need suggestion for coating for fretless aluminum neck
Ano would look best and last a while. If you don't mind losing the metal color, powder coat is an option...I'm still amazed by the abuse the powder coating on my offroad truck gear takes without a problem.

-Matthew
Author:  SteveSmith [ Thu Nov 05, 2009 12:04 pm ]
Post subject:  Re: Need suggestion for coating for fretless aluminum neck
Yeah, I was thinking powder coat if the plastic part can stand the heat (it has to go in an oven, right?).
Author:  mateo4x4 [ Thu Nov 05, 2009 1:41 pm ]
Post subject:  Re: Need suggestion for coating for fretless aluminum neck
SteveSmith wrote:
Yeah, I was thinking powder coat if the plastic part can stand the heat (it has to go in an oven, right?).


Yep...around 400F I think. Fun bit of trivia...powder coating is the same basic technology as laser printers...just more intense. :-)

hmmm....thinking on it, a good marine epoxy might handle the wear and tear pretty well. If it did get messed up from use, you could sand it smooth and re-polish it, or just sand down and recoat as needed.

Would oiling aluminum work for this at all? (like how steel can soak up the oil and get protected)

-Matthew
Author:  xplode [ Thu Nov 05, 2009 2:33 pm ]
Post subject:  Re: Need suggestion for coating for fretless aluminum neck
I'm pretty sure the anodized layer, which I will now just call alumina or Al203, might actually be worse for the sound. The thicker it is the worse it would be. I calculated the speed of sound, c_some solid, in Al203 to be c_Al2O3 = 9566m/s which is about twice that of aluminum's, c_Al = 4877 m/s, which is in turn about 50% greater than in wood, which varies from c_soft wood = ~3000 m/s to c_hard wood = ~4000 m/s.

The equation I used is the c_1 equation:
http://en.wikipedia.org/wiki/Speed_of_s ... _in_solids

The data I used for alumina can be found here:
http://www.accuratus.com/alumox.html

and the data I found on aluminum and wood is from Engineering Toolbox, a really useful site:
http://www.engineeringtoolbox.com/sound ... d_713.html

Other than comparing hardness, acoustic impedance, speed of sound, density, microstructures (a metallurgy thing) and gut feel, I guess I really don't have much justification for influences of the coating on the frequency response of the neck. I wonder if anyone knows anything about this. I also wonder if the how different the modified neck will even sound from the original.

I might have to do some experimenting to see how much heat the plastic can take to see if powder coating is an option. I know they cook that stuff for a while -according to wiki: 200°C (390°F) for 10 minutes. In retrospect, I think that was what was on it in the first place because it was about as thick as a powder coat layer (about 1/3 mm). and had wear patterns like a soft material.

Maybe Ovation powder coated the fretboard, cured it then thermally bonded the neck while it was still hot. I don't know.

Seems like I'd be a lot better off if I could get these two separated. I don't have a good idea of what the adhesion is between these two material (it looks pretty dang good), or if any glue was used (it looks like there wasn't) but I bet you all know some tricks. I definitely have no experience with this. I don't know how useful steam would be on these materials, they both have very non-porous surfaces.

I think epoxy is probably the most realistic option. I think I have just the stuff. Same stuff I used to set the fret markers. Maybe I'll try if the neck sounds too bad with the poly. For now its shiny, and somewhat (hopefully) wear resistant. I didn't use it this time because I didn't know how to get it even without sanding but it sounds like that may be the way to go for the future. I may even try for a better polish then an acid etch.

If any one knows anything about materials' acoustic properties I'd like to pick their brain.

Thanks again,

Collin
Author:  Mike_P [ Thu Nov 05, 2009 2:42 pm ]
Post subject:  Re: Need suggestion for coating for fretless aluminum neck
I don't think any kind of traditional finish (i.e. lacquer, poly, varnish, etc) would work...sure, if applied properly it will bond but you're going to rub it off real quick like when you push those strings down on it!

I think anodizing is the best option though perhaps a powder coat would actually make it sound better being that the traditional fretless neck uses ebony which while hard is quite a bit softer than Aluminum...

of course it may not need any finish at all since it will typically be exposed to only finger oils and inside atmosphere as opposed to being exposed to a salt water environment with wreaked havoc on the aircraft in the Pacific in WWII....
Author:  Zach Ehley [ Fri Nov 06, 2009 9:33 pm ]
Post subject:  Re: Need suggestion for coating for fretless aluminum neck
xplode wrote:
1) What can I coat the neck with to prevent oxidation and scratching?


I guarantee its already oxidized. AL actually oxidizes very fast and creates a thin layer of aluminum oxide that is very hard and wear resistant. Generally you don't need to put any coating on aluminum because of this. If it does scratch, the newly exposed metal quickly oxidizes and creates a new barrier.
Author:  MRS [ Sat Nov 07, 2009 3:40 am ]
Post subject:  Re: Need suggestion for coating for fretless aluminum neck
I would just use an aluminum polish and then a car wax to seal and protect. This protection would only be temporary though and would have to be done on occasion. Any type finish will wear with play. Try a rim polish like meguiars
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