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ambrozy Offline OP
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I have a question for people who do Fandrich epoxy soundboard repair, how much (weight) resin do you usually end up putting on soundboard?

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I plan to do one in the next month or two. I'll try to remember to weigh it as I mix it, and report back.


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Ok thanks! I plan to do it later this year and just doing research now and also searching suitable resin available in my country.

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Its a good acoustic question, but i don't think it matters because the goal seems to be saving a damaged board at minimal cost.

Acoustically, adding weight is undesirable as it starts chipping away at many of the characteristics that make a tone beautiful.
Poor soundboard/rib designs can be too heavy at the start. Too much finish, and too much downbearing can lead to unsatisfactory results. The choice itself of using Spruce for sounding boards is that Spruce has the highest Strength to Weight ratio of all the softwoods. Technically many other woods can be used as a soundboard.

It will be interesting to know how much further weight is being added by technicians that use this method.

-chris


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ROUGHLY 300-400 grams of material on average. Two coats...second coat goes on hot creating one thick coat, much of which gets sanded off to level. Then I usually apply one or two coats of marine varnish.

Peter Grey Piano Doctor


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I use the same procedure that Peter uses. The added weight is minimal and really doesn't matter. What matters is the results and you're expectations. The procedure will make a good board better, but it will not make a bad board good. You have to evaluate the board and decide if it is the right approach.


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Bill,

I wanted to thank you for your tip about orienting the piano wire vertically for restringing. I would say this is a significant improvement in my work now. I set up a dead simple arrangement and it's hard to believe how much better it is which such a simple change. Thanks again!

(I don't recall the thread in which this came up so I just thought i would mention it here since you and I seem to share some similar procedures). 😊

Peter Grey Piano Doctor


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ambrozy Offline OP
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300-400g shouldn't make a difference, I see that.

Originally Posted by Bill McKaig,RPT
The procedure will make a good board better, but it will not make a bad board good. You have to evaluate the board and decide if it is the right approach.

Can you be more specifit what you mean by bad board?

I've been doing work on pianos (tuning, regulation, action repairs) for the last 10 years, but I'm not a proffesional technician. I'm robotics engineer so I understand physics and theory well, but regarding soundboard repairs I have zero practical experience. I plan to do this to one of my pianos, it's a 185cm grotrian from 1918, I've been planning soundboard repair since I bought it 6 years ago, but I realized that it was beyond my practical skills at that time. Now when I have much more skills regarding pianos and woodworking and also made bass string winding machine (I will post some interesting tests regarding scale design soon) the time has come laugh

Soundboard of that piano looks bad, it has no crown, separated ribs and of course cracks right at the old shims (it was repaired probably 30-50 years ago) but it sounds way better than it looks, it is not good of course but piano is usable, just some sustain problems in the middle. For example I've seen piano (august forster 200cm 100 years old) that has soundoard visually in much better shape but it was soo "boomy" that it was absolutely unusable. I think my board should be better candidate to repair if it sounds closer to good board despite it's worse condition, am I right?

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The worst boards I have tackled had severe cracking of the soundboard, and serious issues with rib detachment. Both sounded terrible before the projects began, and both had a very presentable sound at the end of the process. One of these projects proceeded poorly until, after going through the Fandrich process, I used a protocol for restoring appropriate rib adhesion developed by Jim Ialeggio.

(See posts at the bottom of the following thread) https://my.ptg.org/communities/comm...Key=7c1eb77f-336a-4af2-aaeb-32770faeff51

I also use a protocol described by Bill Spurlock in an article titled "Bridge Repairs for Better Tone" originally printed in the March 1992 Piano Technicians Journal, then reprinted in the August 2015 journal.

Since this is your own piano, I wholeheartedly encourage you to go for it!


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Its impossible to put a proper crown, and its associated internal forces back in. Your board isn't bad. its basically dead on arrival.

A board that is crowned properly will be more responsive to the energy from the strings. Energy efficiency is the key to tone production that sounds alive. Boards that are heavy and with misaligned driving points often exhibit tone problems right from the start. Thin bass, weak alto sections that i have noticed A 1/2 a pound or 3/4 of a pound is an enormous amount of weight when you consider that its cumulative. I did a video in which I weighed 3 Baldwin R soundboards. A 3 pound difference between the lightest board and the heaviest board. So lets see- 18, plus 1000 downbearing, plus 1lb new finish and 1/2 pound epoxy = roughly 1,019.5 lbs the soundboard is expected to carry. I just made a new Baldwin R board at 12 pounds. And I only put 2 light coats on a board, and I use a light downbearing plan which all together totaled 512.5 pounds.

Do heavy boards with heavy loads work? yes, but to my ears they sound like they acoustically reduce the size of the piano. I always went the other way and tried to make the smaller pianos not sound small.

Maybe just comes down to personal taste.

-chris


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Thanks Peter, I'm glad it's working out for you! It is amazing how a small change can make such a big difference.

Ambrozy,
I would not consider that board appropriate for epoxy treatment, but that would be your call. If you wanted to save the original board, I would use Craig Hair's (Hampshire pianos) procedure of pulling the board and re-crowning.


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To be clear I don't expect that somewhat deformed board with no measurable crown will magically work like new because I put some epoxy on it, as I said piano is mine and as you can guess it didn't cost a fortune, so it's a bit more like an experiment. Epoxy is the last step anyway so I'll know if I was able to get the board back into reasonable shape before that. I'm open to any non standard way of repair and I'm considering pulling out the board and re-crowning if others method fails.

http://moypiano.com/ptg/pianotech.php/2009-July/011127.html
What do you think about this method?

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That method (above) I personally would not bother with.

The primary principle behind the Fandrich protocol is that epoxy "synthesizes" the stiffness factor that was originally engineered into the board with the crown. Depending on the specific details of the board, I have been able to "regain" a small amount of crown in the process (usually), but that is really not my objective...just a nice side benefit.

A prerequisite for this to work is to make sure that all cracks are filled tightly and fully. Leftover hairline cracks that may have been unseen or too small will be filled with the first coat of epoxy. When the window for "hot" application of the second coat opens, I apply as much material as I can as much will be sanded off in the final leveling process. Heat and wedging is kept on the board throughout the process till everything is cured (which takes 7 days). I also apply to the bridge sides in an effort to create a tight homogeneous structure.

I like the results (and others seem to as well). No, it's not a new board, nor is it an effort to pretend that it is as good. Pretty darn good though.

Peter Grey Piano Doctor


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Peter has made the comment that he uses 300 to 400 grams in an application of epoxy on an old board. Unlike finishes like lacquer or varnish which contain volatile solvents that reduce the volume of material as they evaporate, epoxy is close to 100% solids as it catalyzes into a solid state. This means that all the material that goes onto the board stays there. A question that i would ask Peter is if he weighs the cup full of mixed epoxy before he lays it on the panel, and then reweighs the container with whatever material remains after application to determine the actual amount of epoxy that is on the board.

After the application of the epoxy, the surface is fairly rough in the best of circumstances and will need to be leveled. My go to here would be to scrape the epoxy surface with a very sharp scraper until it is completely level, followed by sanding to a more finished surface. This means that I am removing a fair amount of material to get there. Let's say that I have removed 25% of the material to get there, so if I start with 300 to 400 grams, then I have removed 75 to 100 grams, leaving 225 to 300 grams. Or if I am taking off 50% of the material, I am left with 150 to 200 grams on the panel. I have not done this, but this could be determined by keeping all the scrapings and sanding dust and then weighing it.

What has been left out of the picture is the fact that we are typically scraping off all the old varnish on a board and then sanding it. Those materials could be weighed, which I have not done. I will make a guess here. If the residue weighs 50 grams (less than 1/10th of a pound), the net gain in weight of the panel would be to 175 to 250 grams. Or about .386 pound to .551 pound. If I have taken off 50% of the material, 100 to 150 grams remaining, or .220 pound and .330 pound. When one compares these numbers to the reported differences that Chris reports in boards of the same make and model being up to several pounds, this seems less consequential than Chris would have us to believe.


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Will,

The short answer is: "No"

I do not weigh anything before, after, or during. I take it off, I put it on, I sand it flat, I add more top coat, and I get what I get. What I am basically after is stiffness. If I get a little crown, great, but not a goal in and of itself (I know this was not what you asked but I'm just reiterating it for the benefit of those not intimately familiar with this process.

BTW, I seem to remember Chris talking about an epoxy coat (thin) on his new boards. I assume he is still doing that...?

When I first started doing this (Del had already been doing it for years) my goal was in fact to try to restore crown. Del had hinted in his original article that he was not 100% convinced that crown (in and of itself) was necessary for good tone. I thought about that a lot. Turning point was when I rebuilt a grand with a totally flat board (zero crown). I had informed the owner that I could not ensure really good results because of this, but he insisted that I go ahead with it as is and he would take whatever he got. Well, the thing turned out amazingly well (I forget the brand but it was not a highly memorable one anyway). I (and he) was totally blown away by how good it sounded (and not one mm of crown...flat). So I began to rethink this whole business of crown. I have my theory but will not get onto it here.

So, in the final analysis, I think that: 1) with the board losing weight over 6-10 decades simply by "seasoning", and 2) removal of original finish and some wood in scraping and sanding, my addition of a few grams of epoxy and finish is inconsequential considering the final benefit of the process.

BTW, though the first coat is horribly bumpy, lumpy and ugly, the second coat (which goes on "hot" without sanding at the point when the first coat is no longer sticky, but not hard yet) almost completely does away with that ugly look and forms one single "thick" layer. Then the whole thing cures for a week.

Peter Grey Piano Doctor


Peter W. Grey, RPT
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I have one additional question, how you decide when is the time for second coat?

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Good memory Peter i'm impressed!
I only use the process on a limited basis now, an old board with a low vibrating frequency (40hz- 50hz) which indicates the loss of compression. Then on the raw wood, i'll use the epoxy wash(1 part epoxy to 9 parts lacquer thinner), this will soak into the wood and stiffen the fibers. A different process than the Fandrich process yes? Which is more of a thick coating if i remember from reading the article. The idea was since compression crowning naturally puts stiffness into the panel, maybe simulate that a little with an the epoxy wash to add some longevity to an old board. There didn't seem to be any noticeable difference when used on a new board.

Regarding weight, because i rebuild for a couple universities, I often have numerous pianos of the same make and model next to each other. When side by side, its fascinating to try and figure out why some just bloom with energy and others are just dead. All i can say is soundboard weight became a consistent variable.

-chris


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You add the second coat when the first coat has solidified enough so that it is no longer a liquid, but is still tacky. You can find more information about this on the West System epoxy site.


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Measurement of soundboard first mode frequency should be a good indicator of board condition before and after whatever repairs are done, does anyone have any data what those frequencies are in good sounding pianos of different sizes?

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Not me, sorry.

Peter Grey Piano Doctor


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