Dupont crack Repair Help!

Bob Holo

It's crack season and I'm about ready to start into the busy part of a build... so I'm just going to kind of do an overkill response that can be pointed to for this sort of thing as I'll be OOP for a while. Either "you're welcome" or "my apologies" depending on whether you like it when I do this or roll your eyes ;-) But if it saves one person from screwing up their guitar this winter... well... probably worth it I suppose. Eventually I'll have the website up and probably put some of this type of thing on it. Anyway... in the interim...

marcos81 wrote:

Well its day 3! And the sponge trick helped out a little bit. the crack doesn't look so dry as it once did.

Not sure what you mean by crack looking dry, but if the crack is smaller, that's good - continue with the case humidifier and have the guitar tech see how far the crack goes in. If the crack is only in the outer veneer you're probably OK. You can do this too... In an otherwise dark room, hold the cracked part of the guitar near a lighbulb and look inside the guitar. Do you see any light spot, or light coming through? Anyway - get the guitar back to a proper humidity before repairing the crack or your filler will turn into a splitting-wedge when things get humid (as the definitely can in coastal Korea in the summer.) And... can't stress enough - ask Dupont what he would do if its his guitar. The repair depends on the materials and process he used originally.

marcos81 wrote:

I tightened the strings to standard tuning and played the guitar. The action is definitely lower than before. I can still hear a clean note on frets but it sounds like the guitar has a built in mute. The guitar is not as bright and whole sounding as before.

If your action is lower and its this time of year, you're very likely dealing with a humidity issue. The guitar sounds different because you've lowered the "a" side of a right triangle where the string is the hypoteneuse and the fretboard is the "b" side so an equal tension along the string path results in a lower downforce along the axis of the "a" side which is the loading force on your soundboard. Make sure the crack is stable before you try anything, but if so, try shimming the bridge a little (half a millimeter... no more than a millimeter thick shim. If the guitar sounds better and plays well, then ask the guitar shop guys to cut you some shims. Get some in veneer thickness (.6mm) and some a little thicker (1mm) Shims should be rosewood - or maple/mahog in a pinch. Half inch by one inch by .6mm (13mm x 26mm x .6mm) flatsawn veneer if possible... quarter sawn veneer gets really splitty in small chunks.

marcos81 wrote:

I also own a gitane GD255 and this guitar was exposed to the same air the dupont was. The gitane right now is unplayable. There is fret buzz from the 14th fret to the 1st. Only an open string is clear.

Yes, it sounds like your action is low due to low humidity. The reason it's not buzzing past the 14th fret is that the string's angle up to the bridge is pretty steep there and if the top is recessed due to lack of humidity, it is likely pulling the end of the fretboard down a little. It's good that it buzzes evenly on all frets... ironically this probably means your frets are fairly level.

marcos81 wrote:

I hope that the damage done to the gitane isn't an example of what is to come to the Dupont.

Wait a sec... I thought the Dupont was the one that cracked? Anyway, you don't know if you've done significant damage yet... check how deep the crack is and contact Dupont if the Dupont is the cracked one.

marcos81 wrote:

I travel to the local Busan guitar store in the morning to find out my options and possibly find a humidifier instead of waiting. ........

Ask them to measure the relief if they have the equipment to do so. It should be about 10/1000" (about 1/4 of a millimeter) If it's less than say 7/1000 or more than 18/1000 then (and only then) adjust the truss rod to bring it back into that range... but get the guitar back to a proper humidity and if the frets need to dressed (if you have high frets though you haven't said anything that would indicate that). Point is - only adjust the truss rod when the guitar is at a healthy temperature and humidity and the frets are in good condition. Contrary to popular belief, truss rod wrenches shouldn't be used by people who don't have a really solid understanding of necks. The world would be a better place if we legalized pot but restricted the sale and use of truss rod wrenches which are much more addictive and harmful ;-)

marcos81 wrote:

Oh but the guitar has never been knocked over, It's only been in my possession a short while and would remember dropping this expensive guitar over.

Understood. Though the drop could have happened before you owned it and just finally expressed itself with the temp/humidity change. With guitars, damage is rarely purely from a single event unless it's a big thing like dropping it or hitting a mic stand. It's usually a combination of things... internal stress caused by weather playing on apposing wood grain orientation or wood density joints such as a horizontal-grain tailblock pressing past the rims or along-side the fretboard or around the soundhole... and a trigger event like a shock or a blast of cold wind or something pressing into the soundboard oddly (installing a stick on mic / agressive palm-mute etc.) happens and some little crack appears which you don't notice. Then the string pressure and weather changes start to go to work on that little crack and eventually... "pop". That's why it's important to maintain temp & humidity and keep your eyes open. If you just make a habit of rubbing your guitar down after a gig with a soft fuzzy natural fiber cloth - the fibers of the cloth will often catch on cracks that you may not even see or feel with your hands/eyes. Catch cracks early and your life will be happier and your repairs less expensive. If you're young and have good eyes, just look your instrument over from time to time.

marcos81

Thanks Bob!,
I'm going to leave a youtube URL today to show the difference so you all can see and hear the differences in the guitar.

marcos81

URL to the Dupont guitar action: http://www.youtube.com/watch?v=KiWRUffm ... AAAAAAACAA

URL to the Gitane 255: http://www.youtube.com/watch?v=E2foAtd1 ... AAAAAAABAA

URL to how I store the Dupont: http://www.youtube.com/watch?v=yz_KYX7v ... AAAAAAAAAA

URL to how the Dupont Sounds: http://www.youtube.com/watch?v=02YpMRCb ... AAAAAAAAAA

lacrossehotclub

Yet another URL

Humidity: the solution, according to Bob Taylor

http://www.taylorguitars.com/guitars/features/woods/Videos/video.aspx?file=Humidity_2_High.wmx

Bob Holo

Your Dupont sounds a little low, but the action doesn't look incredibly low.

The Gitane is ?!? wow... either the action is incredibly low or the neck is backbowed. Tough to say... Have it looked at.

Generally the goal is to get the guitars to a good humidity around 50% and then get the action around 3mm/2.5mm (low-e/high-e) with about 10/1000" relief. Whatever you need to do to get there will depend on where you are. But that's sort of a standard setup. Some pros have different setups to suit their styles or guitars or whatever, but generally any decent GJ guitar should sound & play well under those conditions.

Steven - Thanks for the point to the Those Taylor vids - particularly the humidity chamber one... I'm a big Bob Taylor fan. He's a thinker - he acts on data, which is how it should be.

Jeff Moore

The crack looks like an impact, but the greater threat is the humidity regardless of how the crack happened.
If, for instance, you have forced air heat and the temp outside is below freezing, the dryness will change your guitar - period. Get a humidistat. $8 US at Ace Hardware. Any cheap, passive (no battery), thing will do. I like the cheap ones that look like a clock - easy to read at a glance once you get the hang of it. 40% humidity is right near "6 oclock". Put it in the room where your guitar lives and do whatever you have to do to get it to at least 40 percent relative humidity. Your case is no help at all. Taking the strings off is no help and probably makes matters worse.
I live in Minnesota with passive air heat and doing nothing kills guitars. When the temp outside is below freezing and I do nothing, the humidity inside the heated rooms is 20%. This is certain if slow death to guitars and you can't just re humidify things to "fix" them. As wood loses humidity it changes shape and will to some extent "remember" the new shape. Every piece of wood and every glue joint of your guitar will change. Better to smack it and get it fixed than dry it out.
Buy a humidifier, simmer water on a hot plate, leave the water in the bath tub all the time (only works a little - near the bathtub), put pots of water all over the floor, whatever it takes.

Your Dupont is the child and you are the adult trying to shape the influences your child is subject too.
Dupont guitars are also very sensitive to US foreign policy by the way! Paris would be better.

klaatu

Jeff Moore wrote:

Your Dupont is the child and you are the adult trying to shape the influences your child is subject too.
Dupont guitars are also very sensitive to US foreign policy by the way! Paris would be better.

OMG! Jeff, you are so right! Of all your sage advice, this is the best.

Go to Paris. Take the guitar with you.Get Maurice to repair it. Then stay there. It's a much better environment for the guitar AND for you.

marcos81

It's been a while and I have used dampit on the dupont daily since the humidity always seems to be at 30%. The crack hasn't spread but the there is some buzzing on the frets. The higher GBE strings have a lower action than before the winter. I had taken the guitar to the local shop close to Busan, however the man there was telling me my guitar was S shaped and the fret board needed to be shaved down on certain frets? I took my guitar and left the shop since that sounded incredibly radical since the guitar is less than 7 months old and played incredibly well before the winter. Bob, is it possible that the guitar's bridge may be pressing too much into the wood? I'm getting pretty tired of not knowing whats going on and ask if you know a selmer style manufacturer on the pacific coast I can mail for repairs or if you are up for the service? Should I try adjusting the trust rod? Thanks bob if you see this!

klaatu

The guitar is "S shaped?" What did he mean by that?

marcos81

They had told me my neck was shaped like an S. They said it didn't bow up then down, or in the inverse direction. But they said it was Bowed in a way that is shaped like an S. Weird right? aahhhhh can't stand Korea.