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In The Planning Stage


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I'm planning out a pair of bodies, one of which I'll be keeping. They're essentially the same. Here's the plan:

LP or modified LP style

mahogany or sapele body - 1 5/8" thick

chambered body cavities

1/4" burled redwood top - laminated to 1/8" mahogany or sapele backer for stability

binding - most likely cream

bolt-on neck

So here are some things I'd like some clarification on:

1) What is the minimum thickness for the back/sides before it needs bracing? I'd like it to be lightweight as possible, but still structurally sound.

2) Should the redwood be hardened with sealer before the routing? I know that figured redwood is soft and that burls are delicate. Combining the two seems like a recipe for massive tearout. If sealing it with as much shellac as it will take (I know that it's 'thirsty' also) isn't the hardening answer, what is? OR... if hardening it before routing isn't the answer, what is?

3) Which adhesive would normally be used to glue the binding into place? I've seen binding tape or big rubber bands to clamp it in place, but it's the glue I'm concerned with.

4) Knowing how delicate burls are, is it OK to use my thickness planer to get it level & to thickness? I'd hate to see it get shredded into little Burl McNuggets by the machine or to see a chunk ripped from the center.

Edited by avengers63
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for 2 and 4: I've never heard of sealing a wood to make it safer to work with but I don't think that a finish would penetrate far enough to make much of a difference. The best to prevent splitting way is to make sure your tools are very sharp and take your time and remove wood in small bits.

And for 1: I'm doing the same thing for my guitar. I'm planning on leaving at least 1/2 inch of wood around the edge and back. I've seen pictures of a PRS hollow body carved out by a CNC machine and the sides looked to be around that thickness.

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Polycryl works well from what I've heard. I'd do a search on that both here and on the web. I also know that some people have "pickled" burl wood in a solution of acetone and some acrylic or something? It's not lexan, but one of the clear plastics that disolves in acetone.

What you're thinking about doing is essentially what pen turners do to burl blanks before they shape them. The experts might be found at a wood turning site.

Sorry I can't offer more.

Todd

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1) What is the minimum thickness for the back/sides before it needs bracing? I'd like it to be lightweight as possible, but still structurally sound.

If you leave a solid center block and mount the bridge to it, I imagine you could go a lot thinner without needing braces.. I have a semi-hollow guitar I built. The top is probably between 3/8" and 1/4" thick in different places, unbraced, with a large solid centerblock.

Of course, if you're really building an archtop guitar, I think they usually have two lengthwise braces like a violin-family instrument.

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If you leave a solid center block and mount the bridge to it...

A solid center was indeed my intent. I was probably going to go with a big U around the core.

...if you're really building an archtop guitar...

AAAHHHHH!!! Heck NO, man! I'm WAY not interested in that. The most I'd even consider at this point is a carved top with f-holes - which I'm NOT thinking about on this one. Just a chambered flat-top.

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a big U around the core.

Assuming you mean a U of space around a solid core (never know for sure :D ), then I don't think you need any bracing and your top could be as thin as you want. That solid core, stretching from the neck joint to where the bridge is anchored, is going to bear all the load of the strings. In a sense it's a neck thru, and the hollow stuff on the sides has no structural function.

Dude, you don't want to build an archtop?! Wouldn't that be the greatest challenge ever?

Edited by Geo
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Dude, you don't want to build an archtop?! Wouldn't that be the greatest challenge ever?

Yep. And I know that I'm a few years away from taking up that challenge.

Assuming you mean a U of space around a solid core (never know for sure ), then I don't think you need any bracing and your top could be as thin as you want.

That was what I was meaning for the chamber. BUT - I was questioning the thickness of the walls/back of the body after chambering, not the thickness of the top. But the top thickness is helpful too. I hadn't considered that one.

Polycryl works well from what I've heard. I'd do a search on that both here and on the web.

With a quick look into it, I believe you're right. Polycryl is meant to stiffen & stabalize soft punky woods like burls & spalts before turning. With this in mind, I'm sure it would be more than adequate for routing & planing operations.

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I know others have worked with stabilizing spalted wood with water thin CA. (Read up some of Drak's old threads.) Whether this is helpful or not for the redwood, I don't know.

I don't know anything about Polycryl, but I know that almost everything I've heard of being used to stablize wood outside of thin CA has involved doing it under a vaccuum.

Whatever you do, you will probably want to test it on scrap first - I've had problems with redwood finishing very "blotchy" in the past.

When I did my chambered guitars, I went about a 1/2" thick on my sides, FWIW.

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I recently used some flamed redwood on the front of a solid body. It's very soft and dents easier than pine. I bought some Minwax wood hardener, which I'm thinking is also a polymer resin concoction like that polycryl. When I tested the minwax on a redwood scrap, I didn't like the look of it, so I used thin shellac to bring out the grain first, then the minwax. My redwood was only moderately flamed and I had no trouble hand planing and scraping it, but my tools are hella sharp. Which is to say that I suspect dull tools are to blame when I hear people talk about tear out. Also, I did all the planing before I put on the hardener, which was a good idea because that stuff doesn't smell to tasty when you're working it. I don't have the safety planer, but I'm always suspicious of any machine tools' edge. I seriously doubt you could match the finish of a hand plane and scraper with any power tool.

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I don't know anything about Polycryl, but I know that almost everything I've heard of being used to stablize wood outside of thin CA has involved doing it under a vaccuum.

Whatever you do, you will probably want to test it on scrap first - I've had problems with redwood finishing very "blotchy" in the past.

There seems to be good information on Polycryl on this site which indicates that a vacuum is not a pre-requisite. However, since you mentioned the blotchiness, it's possible that takeup may be patchy across the workpiece if vacuum acrylising isn't employed. That said, there have been lots of previous commentaries on redwood drinking finish so it may still work well with plain old saturation at atmospheric pressure.

http://www.woodnshop.com/PENTACRYL.htm

(Don't like the sound of Pentacryl much....siliconised...ergh)

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I think pentacryl is more aimed at displacing the water in green wood while polycryl is supposed to stabilize punky or funky woods.

I have always thought the colored / marbled plastic woods are pretty cool. I don't know that'd I'd want an entire guitar top to look like that, but figured redwood would be pretty.

Todd

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I think pentacryl is more aimed at displacing the water in green wood while polycryl is supposed to stabilize punky or funky woods.

That's what I was able to get from the various websites as well. As for penetration, here's the directions on the lable:

DIRECTIONS NOTE. The wood should be roughed carve or turned first in order to obtain the best penetration. Add 15% POLYCRYL to hot water and mix well. it is important to use a very weak solution at first. This will allow the next application to penetrate deeper. Apply a liberal amount of POLYCRYL solution to fill in the open pores until the wood will not absorb anymore POLYCRYL. Keep the wood wrapped in a plastic bag allowing the solution to penetrate overnight. Each day, increase the solution by an additional 15% POLYCRYL and again wrap in plastic bag and allow it to penetrate the wood overnight (it is very imports to keep the wood wrapped in plastic until the process is finished.) Repeat this procedure until the wood will not absorb any more POLYCRYL solution. (Note: a solution of up to 50% of POLYCRYL can be used for extremely soft or punky wood.) After wood has dried, it must be seated with a finish.

The reason for wrapping it in a plastic bag is to slow the drying process and thus reduce the possibility of warp or other contorting of the piece. Putting it in a closed box was also suggested.

Thickness: 1/4"/5mm is perfectly safe for most woods. 6mm is about standard for Fender thinlines. I leave the sides between 12mm and 15mm (1/2" and 5/8") wide.

PERFECT! That's exactly what I was looking for.

Don't know how strong/stable the redwood is.

From what little I've seen, not very. Combine with it the fact that it's a burl, which is delicate in hard woods, and you can break 1/4" stock with stiff finger pressure. That's why I'm 1) wanting to harden it before working with it and 2) I'm putting it on an 1/8" backer.

Where we're at: the original questions 1 & 2 have been answered to my satisfaction. 4 has been hinted at, and 3 has yet to be addressed at all.

So... what glue do y'all use to put on the binding? I'm guessing that titebond would work, but if there's a better option that's cost effective, I'd rather go that way.

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Superglue. Tightly strap the binding in place (after sealing the wood with shellac or whatever, to prevent the superglue from soaking into the end-grain) using packing tape (Clear stuff), then drip thin superglue along the exposed bits. It'll soak in through capillary action. Don't overdo it, one application per exposed area is enough. Then remove the tape, and run superglue around the entire edge one more time. Voila, done.

Re: 4, if it's that fragile don't even THINK about power planing it. Sanding is the way to go here. You might be able to plane it by hand with perfect sharpening, setup and technique, but for burls that's still risky.

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Re: 4, if it's that fragile don't even THINK about power planing it. Sanding is the way to go here. You might be able to plane it by hand with perfect sharpening, setup and technique, but for burls that's still risky.

That's what my gut was telling me, but I was needing someone else to say it.

So what's the advantage of superglue vs. titebond? I'm not steping on your suggestion, I just need reasons. FWIW: It's plastic binding, not wood. Were it wood binding, the clear andwer (in mt mind) would be wood glue.

Also, just to be 100% sure, you're saying to securely tape the binding into place leaving an exposed spot, and THEN put a couple of drops of SG onto the seam, letting it seep in? Why not put it on the binding, then strap it onto the wood?

Edited by avengers63
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Re: 4, if it's that fragile don't even THINK about power planing it. Sanding is the way to go here. You might be able to plane it by hand with perfect sharpening, setup and technique, but for burls that's still risky.

That's what my gut was telling me, but I was needing someone else to say it.

So what's the advantage of superglue vs. titebond? I'm not steping on your suggestion, I just need reasons. FWIW: It's plastic binding, not wood. Were it wood binding, the clear andwer (in mt mind) would be wood glue.

Also, just to be 100% sure, you're saying to securely tape the binding into place leaving an exposed spot, and THEN put a couple of drops of SG onto the seam, letting it seep in? Why not put it on the binding, then strap it onto the wood?

The method Mattia is describing allows you to get the binding in place ensuring it is a good fit before bringing messy glue into the equation. This can make your task much easier and forgiving(allow you to make small adjustments if you see a gap here or there, and actually see those flaws more redily without glue all over the joint). You can certainly apply glue to the binding then attach it. It just requires more skill and is less forgiving. You can use Titebond for wood to wood joints, binding cement for plastic binding if you really prefer that(of course they will not wick as CA can, so you will have to apply them to the binding then attach).

Rich

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What Rich said. Tape it down TIGHT, positioned PERFECTLY, and THEN apply glue.

Just did a guitar with titebond today, because I didn't have packing tape and didn't feel like cleaning up superglue+masking tape gunk, and I'm sorta regretting it. the CA method is less stressful and leaves me with less gaps to fix. Fortunately these are easy enough to repair, but still, it's not ideal...

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Cool.

I hope I wasn't sounding dense; I just wanted to be absolutely sure of the best way to do it. These two bodies are going to take a lot of work, and I really don't want to re-do anything or dork it up. I'm anticipating these redwood burls to be a bit unforgiving, so any mistake could be amplified.

Thanks for keeping me on-track and for the added explanations.

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