Members Emory Posted July 4, 2016 Members Share Posted July 4, 2016 Loaned my Larrivie dread to friend, who was less than kind in caring for, returned with 4 splits from bridge to tail. Oh well. Not going to get it fixed, as I live in Thailand and don't have lots of faith in their level of repair skill. Anyway, laying in bed at 4 am after Euro Cup little question popped into head. Could some of those thinner splits if near high strings actually increase treble response? Less mass to move, along lines of tweeter versus whole top being more of a woofer. Not saying this is desirable by any stretch, and I sure don't have any sort of apparatus to measure this (besides not having taken measurements before the ill fated loan). Vision in my foggy brain of top with subsections for at least upper 3 strings. Top keeping from blowing apart would be problem.... Just another pointless post.... just something to wonder about.... call me an idiot. Call me a cab Link to comment Share on other sites More sharing options...
Members garthman Posted July 4, 2016 Members Share Posted July 4, 2016 Loaned my Larrivie dread to friend, who was less than kind in caring for, returned with 4 splits from bridge to tail. Oh well. Not going to get it fixed, as I live in Thailand and don't have lots of faith in their level of repair skill. Anyway, laying in bed at 4 am after Euro Cup little question popped into head. Could some of those thinner splits if near high strings actually increase treble response? Less mass to move, along lines of tweeter versus whole top being more of a woofer. Not saying this is desirable by any stretch, and I sure don't have any sort of apparatus to measure this (besides not having taken measurements before the ill fated loan). Vision in my foggy brain of top with subsections for at least upper 3 strings. Top keeping from blowing apart would be problem.... Just another pointless post.... just something to wonder about.... call me an idiot. Call me a cab No. Splits in the top are not a good thing, period (although the guitar will probably be OK for a long long time). And a guitar top isn't a loudspeaker - you commonly hear the phrase "drive the top" and people believe the whole top physically moves back and forth like a speaker cone - it doesn't. What happens is that the energy of the vibrating string is transferred via the saddle to the top which causes sympathetic vibration in the wood molecules. They in turn cause the surrounding air molecules to vibrate carrying the sound to the ear of the listener. The trick is that the large area of the guitar top brings far more air molecules into play than the small area of the vibrating string. Link to comment Share on other sites More sharing options...
Members Idunno Posted July 4, 2016 Members Share Posted July 4, 2016 You have some rather dear friends. It must be close enough to accept them in all manner of trust or bust, which this story nicely demonstrates. Like Howard sez, the continuous plane of the top generates the excitation. Breaking up that plane with splits dramatically reduces the top's contiguous potential to generate sound. Now, again, about that friendship... Link to comment Share on other sites More sharing options...
Members FretFiend. Posted July 4, 2016 Members Share Posted July 4, 2016 call me an idiot. Call me a cab Call that clown you loaned it to an ambulance. Link to comment Share on other sites More sharing options...
Members Freeman Keller Posted July 4, 2016 Members Share Posted July 4, 2016 There is a discussion right now at one of the lutherie forums about the function of f-holes on an archtop - both as sound holes and their effect on the movement of the top. The general feeling is that they have a significant effect on the top - most people feel that they "free it up" to vibrate more which does follow your reasoning. However you also have the X brace, tone bars, bridge and bridge plate all tying the parts of the top back together so in my opinion the effect, if there on a flat top, would be so small that you wouldn't be able to sense it. Lastly, leaving cracks unrepaired is a bad idea, they can continue to grow. If nothing else wick some very thin CA glue into the crack - I can talk you thru the process if you want to try it. Link to comment Share on other sites More sharing options...
Members FretFiend. Posted July 4, 2016 Members Share Posted July 4, 2016 No. Splits in the top are not a good thing, period (although the guitar will probably be OK for a long long time). And a guitar top isn't a loudspeaker - you commonly hear the phrase "drive the top" and people believe the whole top physically moves back and forth like a speaker cone - it doesn't. What happens is that the energy of the vibrating string is transferred via the saddle to the top which causes sympathetic vibration in the wood molecules. They in turn cause the surrounding air molecules to vibrate carrying the sound to the ear of the listener. The trick is that the large area of the guitar top brings far more air molecules into play than the small area of the vibrating string. Agreed. Splits in the top are not a good thing, period. Yes. a guitar top is a loudspeaker. The top and braces are the cone, and the strings/saddle/bridge/bridge plate are the driver. "sympathetic vibration in the wood molecules" ??? Really??? Link to comment Share on other sites More sharing options...
Members Idunno Posted July 4, 2016 Members Share Posted July 4, 2016 Agreed. Splits in the top are not a good thing, period. Yes. a guitar top is a loudspeaker. The top and braces are the cone, and the strings/saddle/bridge/bridge plate are the driver. "sympathetic vibration in the wood molecules" ??? Really??? FF, how do you distinguish "Yes. a guitar top is a loudspeaker" from "sympathetic vibration in the wood molecules"? I'm not seeing one, if a distinction is indeed one you're attempting. And, with regard to braces, I'm not wholly convinced they're drivers as much as they are attenuators. I think I'd place them as attenuators first and foremost as a top without them would certainly result is permeation of whole frequencies versus partials in their presence. Dang it. I'm talking about guitars. Link to comment Share on other sites More sharing options...
Members Emory Posted July 5, 2016 Author Members Share Posted July 5, 2016 Thanks. Yes he is a dear friend, comes to Thailand once a year for a couple months from Holland. Been loaning different ones for several years no problem, although now I have told him needs to make other arrangements for guitar. Along lines of have overnight guest, then leaves turd in the bed... splits seem to be from sound hole to where tail joins the sides, so can't get longer (always look on the bright side of life). Could it be possible that those splits may trigger other splits nearby? Til top looks like set of pickup sticks glued together? Tommy Emmanuel stops or stays with friends brother when in Holland, usually has a Larrivie he puts on stage (some sort of promo deal I reckon). Maybe I should ask if he can arrange a swap. Fat chance! I wonder if I can get CA glue here.... CA same as superglue? I do have some gel brought from US and other stuff available here.... I suppose with mirrors and bit of coffee I could try to apply from inside.... I could see gluing fingertips inside of guitar.... Freeman, thanks for offer of help. Maybe you know of site or post I could just go to regarding wicking Ca? Link to comment Share on other sites More sharing options...
Members garthman Posted July 5, 2016 Members Share Posted July 5, 2016 . . Yes. a guitar top is a loudspeaker. The top and braces are the cone, and the strings/saddle/bridge/bridge plate are the driver. . . No FF, it isn't a loudspeaker. A loudspeaker is a device for converting electrical energy into acoustic sound. The electric current stimulates a magnet which physically moves the speaker cone. Explanation here: http://www.explainthatstuff.com/loudspeakers.html [quote=FretFiend . . . . . "sympathetic vibration in the wood molecules" ??? Really??? Yes FF, that's precisely what happens. The principle is called "forced vibration" and you can read about it here: http://www.physicsclassroom.com/class/sound/Lesson-4/Forced-Vibration Link to comment Share on other sites More sharing options...
Members FretFiend. Posted July 5, 2016 Members Share Posted July 5, 2016 Look up the definitions of "forced" and "vibration". The movement of the strings force movement of the top, just like the movement of the voice coil forces movement of the cone. A formal proof is not required to make a simple point, but if it makes you feel better... It's not rocket science. BTW, the cone on a Victrola is also known as a loudspeaker and it uses no electrical coil. I won't quote any physics on that tho. Look that up too. Back to the OP's question. I agree with the wisdom here that those cracks should be stabilized and repaired. Link to comment Share on other sites More sharing options...
Members Freeman Keller Posted July 5, 2016 Members Share Posted July 5, 2016 I'm looking for a good link on crack repair - here is kind of general information from the StewMac site. http://www.stewmac.com/How-To/Online_Resources/Learn_About_Instrument_Finishing_and_Finish_Repair/Which_super_glue_to_use_thin_medium_or_thick.html CA is super glue and it comes in three thicknesses - so called "water thin", medium (which is what you'll mostly find in hardware stores) and gel. I do buy my thin (#10) from StewMac and unfortunately they do not ship out of the US but with luck you should be able to find it. I also buy their little pipettes for applying it to cracks. http://www.stewmac.com/Materials_and_Supplies/Glues_and_Adhesives/StewMac_Super_Glue.html The way I would fix your cracks is first to make sure they are stable - over here that means getting humidity under control - which usually closes them as much as possible. Then I rub some wax, candle or canning wax, on the top right up to the crack, trying not to actually get it inside the crack but covering the top. The CA won't stick to the wax. I fill one of the little pipettes with the thin CA and just run it along the crack, capillary action will pull the glue inside and there should be almost none left on the outside. I'll look inside the guitar with a mirror and flashlight to see if the glue has come all the way inside - you'll be able to see it. After it has dried you can clean the wax off with naptha or alcohol and if there is any glue standing proud of the crack I scrape that with a razor blade. The crack might still be visible and you might be able to feel it but at least it will be stable and not expand or get worse. Usually the braces across the lower part of the top are enough but if the cracks are in an area where there aren't any braces I'll often glue some little pieces of spruce inside to strengthen the area. I don't have any good pictures of the procedure and most of the time I see cracks during the winter - if something comes up I'll take a few pics and send them to you. Link to comment Share on other sites More sharing options...
Members garthman Posted July 6, 2016 Members Share Posted July 6, 2016 ... It's not rocket science. . . . Indeed, it's not rocket science. In fact it's elementary high school science. Here is a pertinent textbook section on the matter: Sound is a wave that is created by vibrating objects and propagated through a medium from one location to another.First, there is a medium that carries the disturbance from one location to another. Typically, this medium is air, though it could be any material such as water or steel. The medium is simply a series of interconnected and interacting particles. Second, there is an original source of the wave, some vibrating object capable of disturbing the first particle of the medium. Third, the sound wave is transported from one location to another by means of particle-to-particle interaction. If the sound wave is moving through air, then as one air particle is displaced from its equilibrium position, it exerts a push or pull on its nearest neighbors, causing them to be displaced from their equilibrium position (note that the particles of the medium do not travel with the sound wave).This particle interaction continues throughout the entire medium, with each particle interacting and causing a disturbance of its nearest neighbors. Link to comment Share on other sites More sharing options...
Members garthman Posted July 6, 2016 Members Share Posted July 6, 2016 I've done a similar fix to hairline cracks but using standard PVA wood adhesive rather than superglue. Seemed to wok fine. Link to comment Share on other sites More sharing options...
Members WRGKMC Posted July 6, 2016 Members Share Posted July 6, 2016 There is a discussion right now at one of the lutherie forums about the function of f-holes on an archtop - both as sound holes and their effect on the movement of the top. The general feeling is that they have a significant effect on the top - most people feel that they "free it up" to vibrate more which does follow your reasoning. However you also have the X brace, tone bars, bridge and bridge plate all tying the parts of the top back together so in my opinion the effect, if there on a flat top, would be so small that you wouldn't be able to sense it. Lastly, leaving cracks unrepaired is a bad idea, they can continue to grow. If nothing else wick some very thin CA glue into the crack - I can talk you thru the process if you want to try it. I agree. Some suggestions that can help. I've done a few with good results. Apply the CA on the inside so you don't ruin the finish. Place scotch tape along the top cracks so the CA doesn't wick through and run down the front, then try and apply the CA only along the cracks on the inside the best you can. and leave the guitar laying flat for awhile till it dries. you can then remove the scotch tape and it should look fairly good. If anything it should at least arrest the cracks from growing and can actually last quite a long time. Its just going to be difficult applying it on the inside. Tape a small flashlight inside so you can at least get your eyeballs in there. You could use two strips of electrical tape along the inside with the crack in between. This will help you guide the glue tip along the place where you have to apply the glue because you probably wont be able to wee very well with your arm in there but you should be able to feel your way along between the two strips as you go. Electrical tape wont stick to CA very well so it shouldn't be an issue if some gets under the tape. just remove the inside tape as soon as possible so before the glue hardens and have some nail polish remover or acetone to get it off your hands if you get it on them. You'll need to do the cracks one at a time too or you may wind up with your arm stuck in the guitar trying to do multiples at the same time. Link to comment Share on other sites More sharing options...
Members Freeman Keller Posted July 7, 2016 Members Share Posted July 7, 2016 Hot hide glue works very well for this kind of repair and cleans up with hot water, but most people don't have access to a glue pot and the liquid hide glue that you can get in hardware stores just isn't the same. One of the nice things about CA is that it does a reasonable job of appearing like the original finish. Link to comment Share on other sites More sharing options...
Members Freeman Keller Posted July 7, 2016 Members Share Posted July 7, 2016 Having done a number of repairs thru the sound hole I think this would be a complete cluster. I did a pretty thorough description of how I have repaired a fair number of top cracks a few posts above - obviously there are different approaches to this. Link to comment Share on other sites More sharing options...
Members Emory Posted July 8, 2016 Author Members Share Posted July 8, 2016 Some very good suggestions I wouldn't have thought of: the wax on top and electrical tape underneath. Plenty of thin superglue available over here. And glad I could get a bit of discussion going about tops and all... nicely civilized of course, as this is acoustic page. Cheers! Link to comment Share on other sites More sharing options...
Members Freeman Keller Posted July 8, 2016 Members Share Posted July 8, 2016 Emory, as with any new technique I would suggest practicing on a piece of scrap wood with a crack first - getting the capillary action of the thin CA takes a bit of practice so you don't get too much on the wood. Also, if you plan to use any kind of tape on your guitar (I wouldn't) it would be wise to experiment with that too - you might end up just gluing it tightly to the top. I did find this video by Robbie O'Brien (he writes lots of how to do it vids for LMI) that shows the basic CA trick. He is planning to refinish the guitar so he doesn't use the wax (in fact, wax would be bad because the finish would not stick to it) but you see the basic idea of getting the CA to wick into the crack. If a tiny bit does stand proud of the crack you can use his razor blade scraper and try to buff any scratches out but its better to not get scratches in the first place. Hope this helps, let us know how it goes. Link to comment Share on other sites More sharing options...
Members guitarcapo Posted July 9, 2016 Members Share Posted July 9, 2016 Admit it. You made this all up. Link to comment Share on other sites More sharing options...
Members guitarcapo Posted July 9, 2016 Members Share Posted July 9, 2016 Those look like just finish cracks to me but the pic isn't that great. Link to comment Share on other sites More sharing options...
Members garthman Posted July 9, 2016 Members Share Posted July 9, 2016 Link to comment Share on other sites More sharing options...
Members guitarcapo Posted July 12, 2016 Members Share Posted July 12, 2016 I wouldn't do anything until you are sure those are cracks in the wood and not the finish. Link to comment Share on other sites More sharing options...
Members WRGKMC Posted July 12, 2016 Members Share Posted July 12, 2016 If you do it from the top, use vinyl tape tightly along the edges of the crack to minimize accidents. Wicking up excess is also possible this way without it becoming a problem to the surrounding area. I'd even leave the tape in place when sanding the excess away so when you remove the tape it has the thinnest line of CA left. If the cracks are definitely there and you're able to put pressure on the top and see the edge of the wood pop up you could even use a thinned mixture of wood glue. It will seep into the crack when you flex the top and a complete cleanup is possible because the glue is water based.The crack may be slightly discolored and lack the shine CA provides but its a heck of allot safer to work with. If the cracks aren't pliable then working the wood glue into the crack is unlikely. You'd need to get a razor down the crack and then you're into something much more difficult to pull off. Link to comment Share on other sites More sharing options...
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