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I recently thinned an engleman top to .125 and now it is quite floppy. It still has a nice tap tone, however. I don't have any deflection measurement capabilities so I can't quantify it. I didn't really notice the floppyness until I happened to get out a sitka top to show it to someone and it was really stiff. I vaguely recall someone claiming that engleman was a lot floppier than other spruces but that they still sounded good. I've never built with engleman before so I don't really know if I should continue with this piece or not.
(floppy top, You'll always be, home sweet home to me)

[QUOTE=Mike Mahar] I recently thinned an engleman top to .125 and now it is quite floppy. It still has a nice tap tone, however. I don't have any deflection measurement capabilities so I can't quantify it. I didn't really notice the floppyness until I happened to get out a sitka top to show it to someone and it was really stiff. I vaguely recall someone claiming that engleman was a lot floppier than other spruces but that they still sounded good. I've never built with engleman before so I don't really know if I should continue with this piece or not.
(floppy top, You'll always be, home sweet home to me)
[/QUOTE]

What size of guitar is it going to be? Is the piece well quartersawn? If it is a small body guitar it will probably be fine, but a larger guitar like a dreadnaught has to have a stiffer top.

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John Mayes
http://www.mayesluthier.com

It's a 0000 size top. 16" across the lower bout. I'm also working on an OM with a redwood top. The redwood is very stiff. Perhaps I could swap them. The sound hole is already cut in the engleman and it is 4". My OM usually has a 3-7/8" hole. The redwood has not had it's sound hole cut yet. Hmmm.

What would you expect to go wrong? Would the top collapse? How would you expect the top to effect the sound?

Mike I always use a 4" hole on my OM's I don't see any problem there. I have not built 0000 but I have built several dreadnoughts with Engelman top that were .120 and have had no issues. With that said each top is different as far as stiffness is concerned, as you well know. If you are concerned that the top is too weak for the larger body, put it in the Om. It is better to make a top too stiff than to make fire wood

Some great advise given to me several years ago by Mr John Mayes, " if it is a floppy top…what the heck you doing using a floppy top!? Throw it away!"

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Lance@LuthiersForum.com

What are the consequences of using a floppy top? Are they physical or sonic? If sonic, what are the symptoms?
Mike Mahar38372.6941782407

Mike,

Good questions. Hope you get the answers you need. I need to learn these things. Any way to determine stiffness of a piece of tonewood besides deflection testing or building experience?

jeff

Since you don't have enough experience yet to determine if it's usable or not, set it aside, and use another top. Once you have a dozen or two guitars under your belt, you'll be able to determine if it's usable or, if it's going to become many back center reinforcements.

If it is indeed too weak to use, it will just self distruct slowly, at worse, or just sound dull and without definition, at best.

This happens with all woods, and not only englemann, so don't feel bad. I've had red spruce tops come through that were useless, Sitka that was less than useless, and I've had Englemann that was super stiff. It all varies...

OK, back into the wood cabinet it goes. I have some nice redwood that I picked up last week. It's very stiff and sounds nice when you tap it. Thanks for all the advice.

[QUOTE=Mike Mahar] OK, back into the wood cabinet it goes. I have some nice redwood that I picked up last week. It's very stiff and sounds nice when you tap it. Thanks for all the advice.

[/QUOTE]

Woah big guy. You might want to let that new redwood top acclimate a while in your shop before building with it. Even it it is kiln dried it needs to normalize. I like to let the wood wait a couple of months in my wood room before building with it. A couple of years is even better;) This may save you some grief down the road.

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tim...
http://www.mcknightguitars.com

You said you lacked the devices to test deflection. Well, they need not be complex or sophisticated. But you still can determine a great deal about that floppy top. For instance, is it floppy cross-grain, while stiff lengthwise? That's where your real need for stiffness is, and you can brace for the other. There is a really unusual cedar top here in our shop that is really flexible across the grain, but like steel along the grain. (It's going to be used, too.) Wood will certainly keep you interested!
As for the soundhole, you could always bind the inside of that 4" hole and end up with one that was 3 7/8".

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From Nacogdoches...the oldest town in Texas.

http://www.stephenkinnaird.com

I built a Parlor one time with a Too thin Cedar Top. The top was a Really nice piece of wood I just went a little overzelaous. At the time I did not think much of it, but later It started developing a very bad bulge behind the bridge where the most stress is. Not a little buldge as that is normal and expected but this was bad. The top was stiff along the grain too, but not that great crossgrain. I was afraid the top was going to just cave in so, lucky me, I had a sister top cut from the same board. I made the top the right thickness for the stiffness, and the guitar turned out SOOO much better than the first time. The crispness came back and it did not sound near as muddy as before.

A top that lacks stiffness is going to break down slowly over time much faster than a stiff one, and not only that a top that is too floppy will lack good separation of notes and sound unclear and muddy. Put that top on a small parlor (like a sub 13" guitar) and you'll be smokin.. cept for the soundhole..

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John Mayes
http://www.mayesluthier.com

What's wrong with the soundhole? I go to 4-1/2" on OM's....

Time to take chances, kids....

(yes, I realize most of you are WAY older than I am <bg>)

I dedided to compare the top to some other tops that I have laying aroung the shop. I got 6 Martin tops at a swap meet last year. My top is floppier than most of these tops but not all. There are a couple of Dred tops in the bunch that flex about the same as my top. The rest are a bit stiffer and a few are a lot stiffer. The floppyness is across the grain. It is quite stiff along the grain.

At this point, my curiosity is getting the better of me. I think I'm going to use the top just to see how it turns out. This guitar is not for a customer so I can re-top it if there is any problem. Sometimes you just have to do the experiment and see. Since I know that I'm taking a risk, I won't be too disappointed if there is a problem. I'll just remove it and put another one on.

That's the spirit!

Mike it is tough to judge a top that is thinned and joined to a top that has not been thicknessed and/or joined. Be carefull you are not comparing apples to oranges. A thinned and joined top will be much floppier and can be very mis-leading. When comparing tops off hand they should be the same thickness, at least until you done a few.

These tops were all about the same thickness. .125 +- .005. But you have a good point. The Engleman loosened up quite suddenly as I thined it. The top were all joined with the sound hole cut and shaped to the basic guitar shape.