Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum Continuous Bridge Crack Baldwin SF10

Del; whether wood is or is not the "best" choice to repair a soundboard defect -that you have perfectly described-wood IS what the soundboard is engineered to be made from. Departing from that creates a "known, un-known" future. Using cross-ply, wood, to restrain splitting is part of the original engineering of the soundboard. Just like a rib does. If you read anything into my words implying that I seek to "denigrate you", please accept my apologies. Don't we know each-other well enough to stay calm? Sincerely, Ed

To me, this is not compelling logic. Wood is indeed what the soundboard was made from (not because it is the ideal material but because it has been the best available material). And wood is what failed. It may be that the design or execution failed to account for the weakness of wood, but wood is what failed, is it not?

If, then, wood is what failed, is it not legitimate to consider alternative materials?



I'm not buying this at all. Those of us who know wood (certainly including any experienced piano technician) know that any given piece of wood is an "unknown". Nobody on the planet can predict the response of any given piece of wood. Not even if they have access to MRI and x-ray equipment. So, using wood in a repair --or new construction, for that matter-- always contains an element of the unknown, just because it's wood.

And, lamination of fiberglas/epoxy type materials to wood is very much of a "known" process. Individual piano technicians may not know, but the boat industry has been doing it for years -- both in brand new construction and in repairs of classic wooden boats.

I just don't see that the case is made not to use the repair Del described -- even as a first option.

Mr. Adkins,
Thank you for your prompt response. It shows your passion regarding piano service.

The wood "failed" because of an engineering defect. The engineering of successful, durable, modern soundboards is a well established procedure at least 150 years old.
The fact that fiberglass over wood boats have been made for some 60 years does not make it a known piano application. That makes it a known, un-known. The uncertainty is obvious. It is a piano-not a boat. Respectfully yours, Ed

x (sorry, no interest)

I dunno . . . Soundboard failure is not a novel event. I see soundboards all the time that have failed . . .

And, I believe I have a fair grasp of those techniques since I have been replacing 'em since the '70s.



Again, most of the soundboard failures I see are because soundboards are made of wood . . .


But the idea you present is similar to some of what is being said about non-wood action components -- based on the assumption that the laws of chemistry and physics are not uniformly applicable across the spectrum of substances and events but that they are somehow suspended at the border of "piano work". The scientific approach makes the assumption that phenomena are repeatable and applicable in different parts of the world and in different applications.

Simply put, wood and fiberglas construction is wood and fiberglas construction. Period. And, they are known and understood. The properties of that kind of construction can be expected to manifest the same performance characteristics regardless of its application.

Certainly, being exposed in other applications to stresses greater than what would be normal for a soundboard would be encouraging to the idea that application in soundboard construction is a valid consideration.

And the repair I outlined is designed to both repair the damage resulting from that engineering defect and protect the soundboard from further damage.



Uncertainty disappears with knowledge, understanding and experience.

ddf

Mr Akin;
Again thank you for your interest and I must say I am flattered by you using the reference to the "constancy" rule of Physics. I have used that in many of my lectures to Technicians. Perhaps you attended one?

The particular failure described in this thread is rooted in a wood engineering fault.

I use W,N,&G composite shanks on most of my action rebuilds so I am not new material adverse.

Del and Mr Akins;
You both return to the "boat" theory of soundboard construction. You both make new soundboards for pianos. Have you ever made one for a retail client that had fiberglass coated to the top surface?

I can confidently predict that a soundboard made of solid spruce with ribs on the bottom, (with the usual dimensions), and fiberglass on the top would not function well. It would be too heavy. I know of no fiberglass cloth available with fine enough fiber size and weave to attempt such a construction. I don't think that carbon fiber is light enough either.

Using this technique on a portion of the top for a spot repair would carry the uncertainty of whether the reaction of the board to humidity changes might lead to separation between the glass and board. It would also look out of place and this is no small matter when evaluating a pianos marketability.

My repair technique is consistent with the engineering of piano soundboards thus it carries no risk beyond the workmanship.

I remember the beaches of the area of Puget Sound where I grew up as having been littered at times with plywood boats that were glassed on the outer surface only. The moisture caused the glass to separate from the wood in only a few years.


Neither of you has made a case for glassing over a cracked soundboard. The application of new methods to pianos is something I am always on the lookout for. But I am also very conservative on how I test these. Thats the responsible way. Thanks for listening and good luck!

And you have not made a convincing argument for rejecting this repair.

You are stretching the nature of the repair I described beyond all recognition. The key words in the above are “spot repair.” This is a spot repair to a specific area and type of damage. Typically this is a shear crack immediately adjacent to inside treble curve of the inner rim—in some cases the crack may actually overlap the inner rim slightly—and is between 100 and 200 mm long. The strip of fiberglass cloth used for the repair would be approximately 25 mm wide and extend beyond the ends of the crack by about 10 to 15 mm. Much of this strip will overlap the inner rim. The rest will extend into the working area of the soundboard panel by (maybe) 30 to 40 mm at the ends. If that far. I fail to see how a strip of e-glass this size is going to weigh down the soundboard panel no matter how thick it is. Or stiffen it, for that.

You keep bringing up appearance as an issue; have you ever actually worked with this stuff? I have—although not for this specific application—and the repair, done with reasonable skill, will be virtually invisible. Sanded and finished along with the rest of the soundboard panel even your critical eye would have a very difficult time picking it out. If fact, I’m reasonably confident that if you were not told it was there and where to look you would not see it at all. Can you say the same for the repair you’ve recommended? No, I thought not.

I too have seen wood boats with fiberglass sheathing that has failed. Without exception the fiberglass was bonded to the wood hull using polyester resins, not epoxy. Polyester resins work well to bind fiberglass fibers together in all fiberglass hulls but it is not a good adhesive. So, yes, it fails when used this way. Contrast these with the many hulls I’ve looked at—we were thinking of having it done to our old wooden boat (we ended up selling the boat instead)—that were properly prepared and then sheathed with fiberglass cloth embedded in suitable epoxy resins.

I realize this forum is primarily about pianos but for those interested a good overview of the proper technique for fiberglassing a wooden boat hull can be found here: http://www.jamestowndistributors.co...at+with+Fiberglass+and+West+System+Epoxy

When done properly this technique improves the performance of the boat, extends its useful life while reducing its periodic maintenance requirements. All materials have to be applied in a manner appropriate to the intended use.

ddf

Del,

You wrote earlier,



and then, later,



Do I understand correctly that your proposed repair is done to the top surface of the soundboard? (How else would it overlap the inner rim?) Do I therefore also understand correctly, by the part I quoted first, that when the plate is back in the piano, the repair is invisible anyway?

That is correct. It is completely covered by the string frame. And that explains why this specific crack can be present for years—decades—and not be noticed. That, and the fact that there is rarely any audible clue drawing our attention to it.

Still, if we're going to repair something it should be done in a neat, workmanlike manner and be as unobtrusive as is practical. By being essentially invisible the repair I suggested fulfills that requirement nicely.

ddf

Del;
I am convinced that most piano soundboards are made of wood. I am also convinced that the owner of such a piano wants any repairs due to engineering defects-to be engineered to work with the wood structure in a way that solves the defective design. I am also convinced that said repair should not carry any added uncertainty by introducing unknown factors into evaluating the future utility of the piano.

You are not convinced that repairing an engineering defect, that is due to the lack of an area of a soundboard having adequate cross grain restraint, with a proven piano woodworking technique is better than treating the repair area like a nautical vehicle.

So there we stand. It would be interesting to see what piano dealers think of the comparison.

I doubt many, if any, dealers have ever encountered the problem since most of these cracks go undetected until—and for some other reason entirely—the string frame is removed from the piano. And then I suspect that most of them will want it repaired in the fastest and cheapest method possible. And that won’t be either of those we’ve been discussing.

ddf

Del;
If the boat people promised "better" performance after glassing your old wood boat hull-they must have also planned to put in a more powerful motor-glassing will increase the weight.

You need to bring yourself up to date, Ed. Times—and materials—have changed since the bad old days. We would actually have been able to cut back on power requirements. For a quick look at how this should be done, go to:
http://www.jamestowndistributors.co...at+with+Fiberglass+and+West+System+Epoxy

ddf

Thanks Del;
I'm so old fashioned that I still live by the old adage about a boat being a hole in the water into which you pour money! So I don't own one!

That, ultimately, was the conclusion we came to also so we sold it. It was a lot of fun while we had it, though.

ddf

There used to be an America's Cup winner in our marina here in town. I understand that when someone asked the owner what it was like to own an Americ's Cup winner, he replied, " Imagine standing in a cold shower tearing up hundred dollar bills".

I enjoy sailing -- on other people's boats.

The epoxy glassing of a boat hull only reduces the weight by stopping the water from soaking into the wood. So it is heavier in dry-dock but lighter on the water. Thats what counts though.

Just because glassing wood is a proven boatbuilding protocol does not mean it is proven in pianos. Introducing new materials into a piano is fraught with difficulties. Piano owners expect a long service life to a well maintained piano. 50 to 100 years is easily attainable. the new composite action parts are nearly indestructible compared to wood parts. Of course the cushioning materials will still wear and distort.

I don't know of any technician who has repaired a soundboard split with glass/epoxy overlay.

My typical client is someone with an engineering/science/technology professional-they would not find a soundboard repair with epoxy/glass to be proper.