#1
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how to repair crack in soundboard of harp?
Small 26 string dusty strings about 40 yrs old with I'm pretty sure what's a laminated soundboard with a horizontal crack near low c that is half way across and apparently growing, visible on half the width on both sides. the other side it's only visible inside and hasn't reached the surface. It appears threatening so I loosened a few strings. Needless to say it's all the weathers fault !
so is wood the best patching material... glued cross grain'd , or does that matter on a lam top? what about alternative patching materials that might be available? thanks for any suggestions.
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Goya g10, Yamaha CN525E, 10string classical, Babilon Lombard N Alvarez a700 F mandolin, Epiphone Mandobird Ovation 12 string 1515 Takamine F349, Takamine g340, Yamaha LL6M, Enya X4pm '78 Fender Strat Univox Ultra elec12string Lute 13 strings Gibson Les Paul Triumph Bass Piano, Keyboards, Controllers, Marimba, Dusty Strings harp |
#2
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It's hard to give useful crack repair advice without photos. Even more so when the cracked panel is made from laminated hardwood. Both sides, please. And close up.
Did the crack appear during your ownership of the harp?
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"Still a man hears what he wants to hear, and disregards the rest." --Paul Simon |
#3
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thanks Howard....I'll work on the photos . Yes , recently...this year, maybe this week? Obviously I just noticed it. We're in a serious dry spell in my neck of the woods.
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Goya g10, Yamaha CN525E, 10string classical, Babilon Lombard N Alvarez a700 F mandolin, Epiphone Mandobird Ovation 12 string 1515 Takamine F349, Takamine g340, Yamaha LL6M, Enya X4pm '78 Fender Strat Univox Ultra elec12string Lute 13 strings Gibson Les Paul Triumph Bass Piano, Keyboards, Controllers, Marimba, Dusty Strings harp |
#4
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https://postimg.cc/8JyZktYv like I said...ugly & possibly structurally compromising thanks for all suggestions my thoughts...maybe carbonfiber sheet & epoxy. If it cools down the bass strings alittle it wouldn't be the end of the world.
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Goya g10, Yamaha CN525E, 10string classical, Babilon Lombard N Alvarez a700 F mandolin, Epiphone Mandobird Ovation 12 string 1515 Takamine F349, Takamine g340, Yamaha LL6M, Enya X4pm '78 Fender Strat Univox Ultra elec12string Lute 13 strings Gibson Les Paul Triumph Bass Piano, Keyboards, Controllers, Marimba, Dusty Strings harp |
#5
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Maybe a picture zoomed out a little to see where the crack is in relation with the rest of the instrument?
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Fred |
#6
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I'll take another 'context' photo tomorrow. It's obviously in need of structural repair. cosmetics are unimportant ...as long as it works.thanks
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Goya g10, Yamaha CN525E, 10string classical, Babilon Lombard N Alvarez a700 F mandolin, Epiphone Mandobird Ovation 12 string 1515 Takamine F349, Takamine g340, Yamaha LL6M, Enya X4pm '78 Fender Strat Univox Ultra elec12string Lute 13 strings Gibson Les Paul Triumph Bass Piano, Keyboards, Controllers, Marimba, Dusty Strings harp Last edited by kurth; 05-08-2024 at 08:32 PM. |
#7
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https://postimg.cc/hfWy9PFf
looking at the photo, it magnifies the 'slight bulge along the crack , that to me appears the lamination has separated some....just guessing....maybe first, a watered down glue to penetrate and a hard press, then interior reinforcement.... ....how about vertical bracing, as well as a patch ? or a awkwardly placed soundhole ? ...are epoxy's too brittle for the vibration? thanks for any suggestions...
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Goya g10, Yamaha CN525E, 10string classical, Babilon Lombard N Alvarez a700 F mandolin, Epiphone Mandobird Ovation 12 string 1515 Takamine F349, Takamine g340, Yamaha LL6M, Enya X4pm '78 Fender Strat Univox Ultra elec12string Lute 13 strings Gibson Les Paul Triumph Bass Piano, Keyboards, Controllers, Marimba, Dusty Strings harp |
#8
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Are there just two layers, front and back?
I was expecting plywood, which always has at least three layers, and an odd number of layers so the outside laminates' grain runs in the same direction. What I think (correct me if not) I'm seeing here is that the main, thicker lamination is the inside, running at 90º to the thin veneer on the outside face. And what cracked from low humidity is the thicker inside lam, with the outside veneer not being thick and strong enough to resist tearing along with the inner lam when it opened. That would make the inside damage structural, while the outside damage is cosmetic. As with a guitar, you want to humidify to get the crack to close up, but not to make it so humid that the crack will open again (or open somewhere nearby) when the humidity is down in the normal range again. I'd suggest removing the strings adjacent to the crack and loosening the strings a little ways further out from the crack. Then give it a week at an elevated (like ~60%) room humidity. I suspect the crack will not close all the way. And if that's so, then there is little to be gained by splinting the crack as you would on a guitar, since it's on the inside where it won't be seen, and you are going to put cleats or a patch over it. Do you have or can you borrow a deep sliding bar ("F") clamp, that can reach around to near the middle of the crack [this type: ]? It looks like you need about a 4" reach. For a backup patch (which will be doing almost all the work of keeping the crack from reopening), I'd use something like a strip of maple (or other hardwood) about 3/32" thick, and about 2" wide and a little more than the length of the crack (narrowed at one end so it can fit between the string holes). It can have its grain running across the crack, or even better on a bias so it's at a little less than 90º from the way the crack runs. Bevel its edges to reduce the stress riser crossing the soundboard grain. Make an inside and an outside caul from hardwood or good plywood about 3/4" thick and use wax paper on both sides so the cauls don't get glue to the soundboard. You can place the cauls with adhesive tape when you glue. I think epoxy would be best for this, especially if the crack is not fully closed. A hardware store brand would be fine, but not the 5 minute. Epoxies are not so rigid that they will crack if the soundboard flexes a little. Lightly sand the inside soundboard and the glue side of the patch wood to give the glue a fresh surface to adhere to. Don't apply any glue to the outside veneer. It's important with epoxy to mix very thoroughly, which is one reason not to use the 5 minute (it's also not as strong as the slow stuff). Apply the glue liberally, clamp it tight, clean up epoxy squeeze out with small rags wet with alcohol (denatured from the hardware store), let it set for 24 hours. If the crack is tight on the other side and looks closed after humidifying, you can just work in some Titebond with your fingers. A few diamond shaped cleats across it would be insurance.
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"Still a man hears what he wants to hear, and disregards the rest." --Paul Simon Last edited by Howard Klepper; 05-09-2024 at 01:51 PM. |
#9
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...thanks Howard I appreciate your feedback
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Goya g10, Yamaha CN525E, 10string classical, Babilon Lombard N Alvarez a700 F mandolin, Epiphone Mandobird Ovation 12 string 1515 Takamine F349, Takamine g340, Yamaha LL6M, Enya X4pm '78 Fender Strat Univox Ultra elec12string Lute 13 strings Gibson Les Paul Triumph Bass Piano, Keyboards, Controllers, Marimba, Dusty Strings harp |
#10
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I repair these,
The soundboard on that looks to be a laminate, the issue for me is the crack is too staright and indented inwards rather than pulled out like a tension crack would haplen, i almost suspect just looking at the crack and location that maybe the harp is folding itself under tension, any chance of a side view of the chamber Steve
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Cole Clark Fat Lady Gretsch Electromatic Martin CEO7 Maton Messiah Taylor 814CE |
#11
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https://postimg.cc/phT4qgZd ...oops...I shoulda thought of trying a straight edge. think you're absolutely right. But....wouldn't the string force fold it inward, instead of outward ? I'm confused and I don't get confused often. thank u ...also to factor in ...when I discovered it 3 or 4 days ago, I loosened all the bass strings up to about the 7th or 8th string. weird. but hopefully it makes sense to you.
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Goya g10, Yamaha CN525E, 10string classical, Babilon Lombard N Alvarez a700 F mandolin, Epiphone Mandobird Ovation 12 string 1515 Takamine F349, Takamine g340, Yamaha LL6M, Enya X4pm '78 Fender Strat Univox Ultra elec12string Lute 13 strings Gibson Les Paul Triumph Bass Piano, Keyboards, Controllers, Marimba, Dusty Strings harp |
#12
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Inisde the chamber we have small square sections of reinforcement with large holes in the middle of them to allow the sound to port between chambers, have you got an open back or closed back, i would look i side and see where the nearest reinforcement is to that damage.
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Cole Clark Fat Lady Gretsch Electromatic Martin CEO7 Maton Messiah Taylor 814CE |
#13
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Goya g10, Yamaha CN525E, 10string classical, Babilon Lombard N Alvarez a700 F mandolin, Epiphone Mandobird Ovation 12 string 1515 Takamine F349, Takamine g340, Yamaha LL6M, Enya X4pm '78 Fender Strat Univox Ultra elec12string Lute 13 strings Gibson Les Paul Triumph Bass Piano, Keyboards, Controllers, Marimba, Dusty Strings harp |
#14
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Cool, sometimes we have multiple chambers up the back to balance the volume, each chamber in this scenario is seperated by a reinforcment as i described (it ties front back and sides), yours as per your description is one large chamber.
Since the crack is near the column pillar attachement point, can we see the structure inside the chamber behind this area and above the foot attachment On the photos you supllied i can also see a small ripple in the side wall where it appears to have started the buckle under tension.
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Cole Clark Fat Lady Gretsch Electromatic Martin CEO7 Maton Messiah Taylor 814CE Last edited by mirwa; 05-11-2024 at 03:33 AM. |
#15
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I am not very fond of the idea with silicone. Instead I would try to stick to superglue or titebond. Try to somehow fill the crack with superglue/titebond and glue a laminate on the crack, from the "inside". Is this the inside https://postimg.cc/wR701DKG ?
Superglue, a laminate, or perhaps a piece of wood then some strong super magnets. The wood or laminate cleet needs to be thick enough to straighten the part of the crack (that now is dented), when set under pressure. Otherwise there will be a not wished for dent in the soundboard. If any glue gets out of the crack I'd scrape it off gently. A kind of simple straight forward solution. Try to get the crack as even as possible. If some work needs to be done to the finish after crack repair. I would stick to cellulose lacquer. Because that's what the harp already is applied with, isn't? Supposedly, the soundboard being laminate, this a'int a top of the line quality harp, is it? Or at least not the most valuable instrument? Supposedly, the work will be more easy to succeed with if the string tension is loosened for all the strings. Then you have a better control of "the arc" of the soundboard. I don't think it is a very difficult task. Please, take my words for what they´re worth, I have no personal experience in repairing harps.
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Just reclining in a place where I am exercising the Swedish national sport of fully over estimating my superiority in the English language. Lester Young and Ted Wilson Last edited by Henning; 05-13-2024 at 04:48 AM. |