Pianotech

Topic: Soundboard cracks 

1.  Soundboard cracks

Posted 01-02-2018 10:13
I am working on an old upright. Some cracks clearly need shims. What do you think about using Gflex epoxy on the really thin ones?? 

Melissa


2.  RE: Soundboard cracks

Posted 01-02-2018 10:32
Melissa,

Before I give my opinion, can you explain in relative detail how you feel you want to proceed on this?  I use epoxy on soundboards, but the "devil" is in the details. Please tell what you want to do.

Also, I have not used g flex. I also use a different product for cracks.

Pwg

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Peter Grey
Stratham NH
603-686-2395
pianodoctor57@gmail.com
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3.  RE: Soundboard cracks

Posted 01-02-2018 11:18
You don't mention if the cracks are causing buzzing. If not, in my opinion, there's no compelling reason to do anything about them.

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"That Tuning Guy"
Scott Kerns
www.thattuningguy.com
Tunic OnlyPure, TuneLab & Easy Piano Tuner user
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4.  RE: Soundboard cracks

Posted 01-02-2018 12:03
*****Long post*****

I have not used the G Flex, but after googling it, I would be tempted to try it as well. 
I would do some bench tests with it on some scrap wood and see if I liked working with it, and how strong, stiff/ flexible it is.
Then I would try some fillers in it. My favorite filler is a very very fine sawdust that collects on the top of my bandsaw. Sometimes, it makes an invisible repair. Sometimes, I have to color camouflage and grain it before refinishing. The question that is forefront regarding epoxy repair is longetivity. A wood shim repair when properly done, breathes with the panel. What does epoxy do over time?
-chris





5.  RE: Soundboard cracks

Posted 01-02-2018 13:08
Chris,

I've used g-flex. Filler is not used, as the viscosity is built into the product already as purchased. According to the techs at West, who I chatted  up several times before I first used it, no "wetting" with a low viscosity product like 105 straight resin, is required.  I've used it as recommended, and for certain applications it works great. If a visible smoothing and sanding of larger gaps is going to be required to make things look nice, g-flex is not an ideal choice, as the flexibility of the product makes it hard to do a flat with the surrounding area patch. I go for harder west mixes in that case. I mostly use it for joints.

If it or any product is to be used for board cracks, new fresh wood in the crack must be exposed before attempting to get anything resembling a well-adhered glue joint.

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Jim Ialeggio
grandpianosolutions.com
Shirley, MA
978 425-9026
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6.  RE: Soundboard cracks

Posted 01-02-2018 13:18
My good friend and mentor in NYC uses it for small cosmetic cracks with excellent results. I've used it several times in my shop for other repairs and have been very pleased with the product.

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Karl Roeder
Pompano Beach FL
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7.  RE: Soundboard cracks

Posted 01-03-2018 17:10
How are you using G-Flex epoxy for soundboard cracks?

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Philip Jamison
Philip Jamison Pianos
WEST CHESTER PA
610-696-8449
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8.  RE: Soundboard cracks

Posted 01-04-2018 08:30
Thanks everyone. Since they won't be too visible I'm using it in the hairline cracks. I've also read that it's ok to to thin it a bit with be mineral spirits to aid penetration.

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Melissa Warren
Lawrence KS
785-749-5000
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9.  RE: Soundboard cracks

Posted 01-04-2018 08:51
I've never thinned epoxy with mineral spirits, but acetone or MEK both work well. You can also use a heat gun to thin it out. In my experience, the buzzing from a soundboard crack occurs where it pulls away from the ribs.

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Philip Jamison
Philip Jamison Pianos
WEST CHESTER PA
610-696-8449
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10.  RE: Soundboard cracks

Posted 01-04-2018 09:35
If the cracks are not visible (mostly) why bother? If the 'repair' fails, you're on the hook to 'fix' it, what a mess. If the board is tight to the ribs, let it be.

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Regards,

Jon Page
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11.  RE: Soundboard cracks

Posted 01-04-2018 09:41
In epoxy land, unless you are consolidating, which is a different animal than gluing cracks, glue lines should try to be no less than 1/32" or so. According to the tech manuals I've read, and my experience in the shop, this wider than usual glue line seems to perform better than minimal PVA type glue lines. This means, g-flex or a 105/hardener/filler combo really does not need thinning to get where it needs to go.  The crack does need fresh non-oxidized, clean wood. The widened crack or kerf accomplishes both a stronger fill with better bond. This, instead of hoping a low viscosity product will completely saturate any exposed non-prepared glue surfaces, and glue the whole thing together. In consolidation jobs, where the wood is highly compromised, there may be adequate saturation, but in a panel with simple cracks, my experience and observations show the product stays near the surface of the joint.

In trying to make epoxy laminated bridge caps about 6 years ago or so, I was impressed at how little low viscosity laminating epoxies (system 3 infusion epoxy), actually wet the wood below the surface. The bond remains pretty darn near the glue surface, low viscosity or not...which is why I say, create a clean new bond surface rather than hoping for saturation.

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Jim Ialeggio
grandpianosolutions.com
Shirley, MA
978 425-9026
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12.  RE: Soundboard cracks

Posted 01-04-2018 09:52
Melissa,

I would not recommend thinning except with heat as this could alter the chemical composition in such a way that it might not cure properly and then you would have a real mess on your hands. Most manufacturers do not recommend thinning their epoxy. Do so at your own risk.

If you are intent on using epoxy this way here is what I would do:

1)  Widen the cracks a little with a standard shinning tool (don't go bananas...just a bit)

2)  Thicken the epoxy like Chris suggested with wood dust or micro-balloons. You dont want it runny for this.

3)  Use a putty knife to work it into the cracks (save yourself some cleanup trouble by putting masking tape on either side of the crack but very close to it). Build up to level of tape.

4)  Let it cure, pull off tape, scrape off excess with the scraping of the rest of the board. (This assumes you are scraping and finishing the board. If not, I have no clue as to how you would do otherwise).

This epoxy has a long cure time. Simply putting it in the cracks as is will mean it's going to come out the other side. You'll need to stop that from happening, and that's hard with a long cure time.

I like to use Lakeone wood rebuilder for this purpose. You can regulate the thickness of it by the proportions you mix. The only caveat is that your window for cleanup is short (but sweet). There is a period between hardening and full cure where it can be scraped perfectly flush with the top of the board with virtually one stroke of the scraper. Then you're done. If you let it go to full cure before scraping off you'll be really sorry as it cures extremely hard and durable. It is also VERY SMELLY as it is a polyester based substance.

I only use epoxy as a full coating on the board (coating epoxy) as per Del Fandrich's protocol.

Anyway, this is simply an opinion. Others are free to disagree.

Pwg


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Peter Grey
Stratham NH
603-686-2395
pianodoctor57@gmail.com
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13.  RE: Soundboard cracks

Posted 01-04-2018 21:08
Best check that idea of thinning epoxy with "mineral spirits." I doubt it will work. You can thin most epoxies (moderately) with lacquer thinner, or just acetone, but mineral spirits (paint thinner) and lacquer thinner are not the same thing. If you want really thin epoxy, it's best to purchase it that way. My elixir of choice has long been System Three Coating Epoxy. I'm now testing a new (to me, at least) epoxy that is even thinner. It's called "TotalBoat Penetrating Epoxy."


ddf

--
Delwin D Fandrich
Fandrich Piano Company, Inc.
Piano Design and Manufacturing Consulting Services -- Worldwide
6939 Foothill Ct SW -- Olympia, WA 98512 -- USA
Phone 360.515.0119 -- Mobile 360.388.6525





14.  RE: Soundboard cracks

Posted 01-04-2018 22:07
I've been using the total boat penetrating epoxy.  That stuff is some awful stink. They say it is all solids, but I find it very difficult to be around in the shop.

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Jim Ialeggio
grandpianosolutions.com
Shirley, MA
978 425-9026
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15.  RE: Soundboard cracks

Posted 01-05-2018 06:39
There's Epoxy Technology's Water Thin Epoxy 301-2 or the newer 301-2FL

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Regards,

Jon Page
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16.  RE: Soundboard cracks

Posted 01-05-2018 09:06
Jim,

How have you used it?  On a soundboard, or on a boat, or elsewhere?  What do you think of it (other than the smell)?

Just curious.

Pwg

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Peter Grey
Stratham NH
603-686-2395
pianodoctor57@gmail.com
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17.  RE: Soundboard cracks

Posted 01-05-2018 15:56
Edited by Jim Ialeggio 01-05-2018 16:08
Peter,

I consolidated  the common, severely checked veneers on a Bechstein refinish job about 1-1/2 years ago. This veneer checking tends to telegraph through any finish...the client was warned about this. However, so far, this being the second winter, the nasties have not telegraphed through the finish. So I think its a good product and keep some on hand. I don't do epoxy soundboard repair work, only new redesigned boards, so I don't know about the soundboard epoxy angle.

I bought it originally to epoxy seal bridge caps, but I'm no longer using epoxy for surface treatment on caps. I found that it requires several coats of epoxy on the end grain cuts, the part one really wants to seal, to achieve the seal I can get with good old shellac which takes a half hour to do three coats. Plus shellac doesn't have the blobby, garish-gloss build-up epoxy has.

Also with the Total boat, or any large quantity of liquid epoxy, one batch started boiling in the mix container. We got it out of the shop quick, and mixed smaller batches...though it really wasn't that much product...only about 1 pint mixed...but it was hot out that day, I think.

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Jim Ialeggio
grandpianosolutions.com
Shirley, MA
978 425-9026
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