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The point of the study is that an abrasive thickness sander tears fibers and compresses the wood. This make for a piece that is potentially less stiff and more dense. Both of those properties are typically desired in the opposite direction. I guess I'll have to do my own study to see if it actually makes a difference. If it is only a few grams f mass over the entire surface of the plate, I might say it is measurable but insignificant

If anyone is interested just google kiyoto tanaka . He has many u tube videos on hand planing , tops backs , sides, necks etc etc . On a japanese planing bench, using japanese tools. He builds several styles of instruments including gtr and IMHO an exc. luthier. I use everything Large , thickness sander, hand planes, and light sanding . Being older I find it hard on the muscles to work in a cold garage /bsmt. So I will use whatever works.!

Just a suggestion -- there are two pages of posts from guys that know exactly "the point of the study" perhaps checking them out may save you from wasting time on your own study.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Seeing is believing ken. Different scenarios could exist that would change the original studies conclusion. What kind of conditions? Are there work arounds you could do to get the best of both worlds? Don't know, but i am curious enough to find out.
Furthermore, investigative study is rarely wasting time.

It is when there are billable hours to be done..... Lift that bale, tote that barge or something like that.....

This is something that I have noticed with Luthiers - many of them/us think that we have an entitlement to have our work be actually interesting.... to us..... Go figure..... Kidding of course!

I guess that is the benefit of being a teacher. Scholarly research is part of the gig

I'm just getting into Lutherie but I've planed a mile or two. I equate sandpaper to destruction of a fine surface. Is it really necessary to sand after planing? Incidentally, I'm planning French polish.

-jj

It's not so difficult to produce a surface fit for polishing away from or separate from a Guitar. Producing one where the rosette and purfling/banding has to go on is a lot more difficult. We also tend to use bookmatched Tops/Backs which makes planing a finished surface even harder. The grain direction is opposite in both halves of the plates.
You can try. Worse thing that can happen is that you'll have to use a scraper or even sandpaper! (shuddder the thought). I've finished off with a scraper many times and even with that tool you have to extremely careful, the scraper also needs to be extremely sharp. It's not easy. Sandpaper is much easier. Glossy finishes like French Polish will highlight any slight dip or depression in the wood. Matte finishes are much more forgiving.

I don't dispute that there's difficulties inherent in the unique aspects of planing soundboards and rosettes and the safe road is often wise. I do have lots of planing experience but none with soundboards so without any practical experience I'm only expressing an opinion regarding planing structural wood.

I too, have been saved many times in a figured area by a well tuned scraper. I suspect I will take my tuning in all respects to a Formula One level in my pursuit of making a guitar.

Figured veneer is often planed with the aid of a Toothing blade. How well does a Toothing blade work on avoiding these problems on a soundboard?

They don't. It's easier just to use a normal Plane at 45 degrees or even straight across the grain. That won't give you a truly polished surface though. You can produce a truly polished surface by Planing each half of the soundboard separately but in the correct direction in respect to grain run out. It's like using 800G or finer abrasive. It will shine. It will be perfectly ready for a finish/varnish without doing anything further to it. So then you have to join the two halves together without creating the slightest step (it's possible), inlay the rosette, glue on and shape all the struts, cut and inlay the purfling and binding. All of that without upsetting the perfectly finished surface.
I'm sure it's possible to do, just unlikely that one can do it on a consistent basis. It's just much easier to wait until right at the very end and either scrape (hardly anyone does) or sand (95%+ do that).

This is excellent insight, thank you.

Why don't more people scrape? Is there some downside I'm unaware of regarding soundboards?

At 60 my wrists just don't take that amount of repetitive motion.

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http://www.Harvestmoonguitars.com

If you're scraping at the end, then the plate is supported better directly over the braces, so you end up removing more wood over them and create a sort of x-ray look. It's possible to carefully focus your attention between braces and use gentle pressure, but it's slow going. Even before bracing, scraping softwoods is a lot slower than hardwoods.

So if you really want that scraped look, then scrape and shellac the show face before bracing, and do everything you can to protect it until the end so the final scraping doesn't take too long.

I know exactly the X-Ray look, I've seen it.

I sincerely appreciate the warnings and will take them to heart. I'm going to try it. Worst case scenario: I end up learning something.

-jj

The X-ray look (telegraphing) is also a product of over clamping and humidity changes, not scraping in itself. It often occurs with sanded Tops too. I scrape at the end and rarely get telegraphing. But a very sharp scraper can be a tool to reach a finished surface pretty quickly.
Scraping will produce the Corduroy surface though. That's where the soft grain lines are compressed and the hard grain lines are cut. It gives the Top a texture, loved by high end Violin makers. You can feel it when you run your hand over the surface. Very few guitarmakers leave it in, preferring a super flat glossy surface, hence the sandpaper. I prefer the texture but that's me.
Soundboards rarely remain flat and 'prerfect' though. There's too much going on on the inside surface. Most Guitar Tops will show gentle dips and humps. They are clearly seen when the light reflects off the surface and the Guitar is moved a little. You hardly ever get the more perfect even, reflected surface that you do from the Back.

Telegraphing braces in my experience are a function of a top that too thin.... Ever see a lovingly used Somogyi? You may see telegraphing braces and his tops can be .065" thin...

Not saying that Somogyi uses tops that are too thin at all here because he compensates in a number of effective ways. But you may see telegraphing and I have personally.

My test mule L-OO that I built to test various tops currently has a .080" top on it, sounds wonderful, and has telegraphing braces.

Interesting -- I have frequently mentioned to many that the best sounding classical guitar I've heard (to my ear) was a burl Mahogany Alvarez Yari, and what I noticed was that every single brace outline was clearly visible on the sound board.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Yeah, thin plate building pretty much guarantees visible braces, unless maybe if you use epoxy instead of a water based glue. But even then they'd probably show through after a few years with strings on. Not a bad thing, IMO. Great guitars can be made with a wide range of soundboard thicknesses (and not necessarily equal thickness all over either). And it's only superficial, unlike scraper-caused x-ray look, which is actually removing wood selectively.

Oh, and another thing you can do when scraping is reach inside the soundhole and support the plate with your fingers between braces where you're scraping. Though it is harder to scrape one-handed.

Just an observation.
I sanded (P100/Jet 10/20) and "Gore" frequency tested two top panels recently, and following this thread I decided to plane the top further and retest.
Unfortunately, one of the plate frequencies was too low after planing to be detected by my mic, so no great revelations there, but interestingly it took nearly 10 thou thickness off each face to get it completely cleaned up and level from the sander and, of course, looks totally different.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I did a similar test Colin and I found a negligible difference. The planed surface did look nicer!

Thanks for the heads up Sam.
I think the density measurement is probably the trickiest to get real accuracy on because the thickness measurement I figure is to around +/- 1.5% at best.
Anyway gave me a chance to test out my new thickness caliper from the far east.
I noticed the travelling end of the dial gauge was denting the spruce anything up to 6 thou - I could see the dents, and the measurement falling as I searched for a minimum reading! Springs were far too strong.
Dis-assembly and cautious tweaking of a couple of springs was in order, much better now.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

LOL Hesh I been there done that with the planner too, backer board, double stick tape the whole 9 yards. I learned the hard way. All I can say is for 20 years I used planes and hand sanders. Then I finally got a 10-20 and wondered why I had been so dumb as to not get one 20 years ago. I do enjoy planing and after sanding I always finish off with a scraper for that gleamy look. But not the tops. I don't like the corduroy affect.

The planer is a great tool though to finish off a board when resawing and for overall getting dimensions right on neck blanks and that sort of thing.