Epoxy - flat using a turner (rotisserie-like)

[warx]

So I'm epoxying a fingerboard and trying to avoid the pour-n-fill route of total re-creation of profile after cure. I had some thoughts.

I have a vacuum pump from my fiberglass fabrication projects and thought how sealing the neck in a bag would help force a uniform bubble-free layer on the board. I don't think it'd help with the radiused flat surface though without standoffs. Doing glass layups you have the glass itself to keep the thickness even.

Then I was thinking about how fishing rods and cups are left to cure while slowly rotating. This makes more sense but of course they are a full 360 degrees of epoxy. A fingerboard is just like 15 degrees. Would it make a difference rotating it out on it's radius (like a 7.25 or 9.5" radius wheel)? Doubt it.

Final thought was a true spun cure where the spinning speed is fast enough to effectively negate/counter gravity with centrifugal force. I'm not sure it would self-flatten though.

I do know that turning and spinning strangely slows the curing process down due to excessive solvent evaporation. Epoxy like Mirror Coat is slow enough already!

 

[Rôckhewer]

Holy crap......
Wait a min.....

.... yeah... hmmmm...
Think like a fiberglass guy!!?....
....backwards. ¿
...create perfect mold....
... mold release....
....."gelcoat" (epoxy)
.... then cram the neck into the mold?
Let cure... trim edges....... done?
Could it be that easy?

For that matter.... since there would be no risk of sanding through...why not "glass" the thing?
Carbon fiber would be cool.

Hmmmmmmm.......
Thanks for the fresh brain food

 

[Rôckhewer]

 

[warx]

Of course someone had to have done the CF!! Good find. Does look cool. Would be hard to incorporate fret-lines although could be left to the top edge (like the pic has the dots).

If laying up fiber vacuum bagging would be great.

If using the fingerboard as a plug to make a mold then I think it would be important to create accurate mold standoffs to keep the mold in a uniform position. Also I think you'd have to think carefully about orientation for the pour/fill and eliminating bubbles and entrapment. Maybe you could use the mold and vacuum bag it as long as the mold was not able to be deformed.

I am wondering about buying a cheap ($10) rotisserie motor and trying it with some radiused wood. Ensuring the length-wise orientation stays dead level makes it harder.

 

[barking_spider]

So I assume that you're going to cut in frets afterwards, or go fretless? My advice is to think like a boat builder. When you need to get a big buildup, you can brush on a coat of epoxy, then wait until it kicks, but is still a bit sticky. Brush on another coat. Lather, rinse, repeat! Because the bottom coat isn't fully cured, it doesn't need to be sanded. You get both a mechanical and a chemical bond.

I've used Progressive Epoxy's Basic No-Blush over the years, and have always been happy with the results. About half the cost of West Systems. Be sure that you that you specify a non-amide blushing mix (Us nautical types would call that a "bright" finish), otherwise you'll have white streaks in your otherwise fine work. Don't forget to tape the sides so that the epoxy doesn't creep under.

 

[warx]

Correct - it's a factory fretless jazz.

I've used Tap Plastics Premium Marine Grade a lot and it's hard and very clear. I find the quick part B forms a harder finish and the pot life is decent at 15 mins. I did just try some MirrorCoat which is less viscous but takes much longer to set up. I'm waiting for 48hrs to do a hardness comparison between the two. I also have some Tap Plastics Vinyl-ester but I'm convinced epoxy is just better for DIY and repairs.

So the re-coat says 3-5hrs for the Marine Grade (end of gel) but the MirrorCoat actually says you can re-coat without sanding up to 24hrs and still get a chemical bond. The one thing I wanted to try was whether you can recoat over a less than perfect first coat that has some out-gassing holes. The answer is yes! With both marine birch ply and some walnut A1 ply I sanded, wiped with acetone and heated to about 110F then applied a thin first coat it showed some pits. Without letting it fully cure (and thus no sanding) I did another coat and it was totally clear. I even tried a bit where after only 8hrs I sanded gently (it was firm enough but not cured) and re-coated that and it was good too.

One thing I did was jiggle and tap my mix cup to help any mixing bubbles rise. There's so little amount needed for a neck it's worth mixing three times too much and dumping the the top half. I suppose stiff brushing could do this also.

 

[barking_spider]

I like the little bathroom dixie cups (shotglass size) for measuring, mixed into a typical red Solo cup. Kinda freaks me out now when I go to a party with people actually drinking out of them! A quick wipe-down with acetone prior to the first coat seems to kill most of the out-gassing for me, but YMMV. I'm very fortunate in that I can take a quick trip up to West Palm Beach to Glue Products Plus, which has everything I could possibly need (at least epoxy-wise) and a knowledgeable help desk for the occasionally necessary dose of adult supervision. I work it in with a chip brush (the ones from Amazon lose less hair than the ones from HD), then tip it off quickly.

After it fully hardens, you can work it down with increasing grits of sandpaper on the radius block to get it perfect. I 3D printed me a 9.5" radius one, let me know if you want the .stl file to make your own. Maybe do a nice marine grade varnish over the top?

I'm speaking from zero experience actually using this method on a fretboard, so take it with more than a single grain of salt. The playability might be compromised, and finger sweat (?) might make the fretboard sticky or gross. But using it on stage, and getting the lights flashing off that shiny neck would be awesome!

 

[tr4252]

Cool thread warx.

barking spider, is that your tribal name? I can't unthank the image it inspires.

If you already have a vacuum pump, do you evacuate the bubbles from your mix before you apply it? I'm guessing you do. I sometimes work with Welch 1402's and 1397's. Any chance you do too?

I've never done a neck as you're proposing, but have taken similar countermeasures to finish sag during curing or drying. Rotating both bodies and necks has saved me from fixing drips and thick spots more than once, but I've never used epoxy for finishing. Seriousley, if by chance you are a CNC experimenter, a step motor drive would give you a fine speed control for something like this. Not to get too bizarre, but you could program it to slow down as the finish hardens, reverse direction, control dwell time, etc. No wait, that seems excessive; this is TalkBASS, not CNC.com.

I hope you're successful, and I learn all about it so I can try it myself someday.

Tom

 

[bobdabilder]

Stop showing me this stuff.

View attachment 3484725

 

[Thumpin6string]

I prefer catalyzed poly instead of epoxy on a fretless finger board. Tape it off, spray a few coats, let it cure and your done. Any imperfections can be sanded and buffed out, or even leave it as a mat finish. No change to the radius. I've used round wounds for years and there is little to no wear or marks. I've been refinishing guitars for 30 years and this is what I found worked best and gives a ton of mwaaa. Holds up better than epoxy too, IMHO.

 

[warx]

If you already have a vacuum pump, do you evacuate the bubbles from your mix before you apply it? I'm guessing you do.

I've just used the pump for completely bagging hovercraft hulls that are made from rigid foam core laminated with glass-fibre and either poly or epoxy. Really squeezes the laminating together and leaves it tight and with the minimum amount of resin.

I think you probably could use it to aid pulling the bubbles out of the mix - but it would need a strong pot with a good seal - maybe something like a spray gun pot.

if by chance you are a CNC experimenter, a step motor drive would give you a fine speed control for something like this. Not to get too bizarre, but you could program it to slow down as the finish hardens, reverse direction, control dwell time, etc. No wait, that seems excessive; this is TalkBASS, not CNC.com.
Tom

Oooohhhh!!! OK, calm down... this could seriously get out of hand! I have not done much CNC beyond some 3D printing to aluminum prototypes.
Well, it does sound like this technique could help prevent sagging but maybe it's easier to be vigilant about thinner but more coats. This MirrorCoat does seem to re-coat pretty well. Perhaps all I need is an alarm clock.

 

[warx]

I prefer catalyzed poly instead of epoxy on a fretless finger board. Tape it off, spray a few coats, let it cure and your done. Any imperfections can be sanded and buffed out, or even leave it as a mat finish. No change to the radius. I've used round wounds for years and there is little to no wear or marks. I've been refinishing guitars for 30 years and this is what I found worked best and gives a ton of mwaaa. Holds up better than epoxy too, IMHO.

I have used Vinyl-ester and did some tests over regular laminating poly and feel it would be a great choice. My Pedulla is great too and held up very well (has some chips - but not on the fingerboard). Its poly layer is very thin too (guessing 5-8 mil). However, spraying it is beyond my means. I've got a conversion gun but it would be extremely painful to have to keep cleaning it so thoroughly and not even sure any of the nozzles would shoot resin. Oh, and of course me not breathing this stuff in would be an issue too. If there was a cheap, small-batch-size gun that is easy to clean or has disposable internals that I could use for other projects it might be an option.

I will also say that epoxy may not be as hard as poly but I feel it has more self-lubricating slippiness to it that might make it wear better than it's absolute hardness.

 

[micguy]

I think the OP is overthinking in worrying about gravity. If you apply a thin enough coat (or multiples of thin coats), surface tension will keep the original radius pretty well. I used thinned epoxy when I did this, and although it did pile up a little bit at the edges, a simple dam of masking tape kept things in check, and it wasn't hard at all to sand off the tiny bit of pile up I got at the edges.

 

[Thumpin6string]

I have used Vinyl-ester and did some tests over regular laminating poly and feel it would be a great choice. My Pedulla is great too and held up very well (has some chips - but not on the fingerboard). Its poly layer is very thin too (guessing 5-8 mil). However, spraying it is beyond my means. I've got a conversion gun but it would be extremely painful to have to keep cleaning it so thoroughly and not even sure any of the nozzles would shoot resin. Oh, and of course me not breathing this stuff in would be an issue too. If there was a cheap, small-batch-size gun that is easy to clean or has disposable internals that I could use for other projects it might be an option.

I will also say that epoxy may not be as hard as poly but I feel it has more self-lubricating slippiness to it that might make it wear better than it's absolute hardness.

If you have a compressor, you can get a cheap gun from Harbor Freight. They work pretty well. A couple flushes and a wipe down of lacquer thinner gets it clean. Paint respirators are not that expensive and work well for protecting your lungs. My biggest issues with epoxy was the thickness and keeping it even so the radius stayed correct. The other option is Super Glue, but that is even a bigger pain and the fumes are deadly.

 

[warx]

If you have a compressor, you can get a cheap gun from Harbor Freight. They work pretty well. A couple flushes and a wipe down of lacquer thinner gets it clean. Paint respirators are not that expensive and work well for protecting your lungs.

May I ask what type of gun you use? I have a Wagner HVLP conversion "syphon" pot (and 30 Gal 2HP compressor) that I can not get the hang of! The only thing I like about it is it can use disposable paper 32oz cups but it does not feed well with them.

I see all sorts of guns from electric to real HVLP (including compressors), touch-up, detail and air-brush. I think gravity feed seems like a better system. I'd never be looking for maximum pot size but ease of use. Seems like you'd need a big 2.5mm nozzle too. I have a gel-coat gun but it's a pretty crummy finish. Fine for boat hulls. I see a touch-up HVLP gun that is identical to the one Tap Plastics sells as a resin gun. I wonder if i just get a bigger nozzle (hope they are standard) for it...
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Also I thought for poly resin you needed like a 2-pack fresh-air system. I have an R51A Organic Vapor mask. Maybe that'd be OK.

 

[bobdabilder]

Do you have a couple pics of this result? What brand of clear are you using?

I prefer catalyzed poly instead of epoxy on a fretless finger board. Tape it off, spray a few coats, let it cure and your done. Any imperfections can be sanded and buffed out, or even leave it as a mat finish. No change to the radius. I've used round wounds for years and there is little to no wear or marks. I've been refinishing guitars for 30 years and this is what I found worked best and gives a ton of mwaaa. Holds up better than epoxy too, IMHO.

 

[Paulabass]

View attachment 3484725

Hmmm....fretless three string banjo with a crochet'ed fingerboard. Git yer hillbilly on!!

 

[Thumpin6string]

May I ask what type of gun you use? I have a Wagner HVLP conversion "syphon" pot (and 30 Gal 2HP compressor) that I can not get the hang of! The only thing I like about it is it can use disposable paper 32oz cups but it does not feed well with them.

I see all sorts of guns from electric to real HVLP (including compressors), touch-up, detail and air-brush. I think gravity feed seems like a better system. I'd never be looking for maximum pot size but ease of use. Seems like you'd need a big 2.5mm nozzle too. I have a gel-coat gun but it's a pretty crummy finish. Fine for boat hulls. I see a touch-up HVLP gun that is identical to the one Tap Plastics sells as a resin gun. I wonder if i just get a bigger nozzle (hope they are standard) for it...
Invalid Link Removed

Also I thought for poly resin you needed like a 2-pack fresh-air system. I have an R51A Organic Vapor mask. Maybe that'd be OK.

I use a Binks gravity feed HVLP for paint and clear and cheap HF guns for primers and sealer. I need to clarify that when I say poly, I am talking about catalyzed automotive grade polyurethane clear coat, not resin. I've also used acrylic urethane clear with similar results. Any standard gun with a standard tip will shoot this just fine. Standard paint respirator is fine too. I get all my basecoats and clear from an automotive body and paint store. For a fretboard, any brand should be fine. I use a fast drying spot clear. It lays down nice and dries quickly. I don't think you can buy less than a quart, but you won't need anywhere near that. Probably a pint or less.

 

[Thumpin6string]

Do you have a couple pics of this result? What brand of clear are you using?

I'll have to get a picture of my fretless. Currently I'm using Evercoat spot clear. I have used PPG in the past, but it has gotten pretty expensive. The Evercoat works well, is easy to spray and dries pretty fast. It leaves a high gloss hard finish, but can be sanded a polished easily.

 

[warx]

Oh - I misunderstood completely. I did not know auto clearcoat would stick to wood. That might be more do-able by taking the neck to a body shop and having them spray it next time they're doing clearcoat rather than me kitting up for it. TBH though I think I'll stick with MirrorCoat epoxy.