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| Fixing a Backward Bow with loose TR? http://www-.luthiersforum.com/forum/viewtopic.php?f=10102&t=8870 |
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| Author: | turbo411 [ Sun Oct 15, 2006 11:46 am ] |
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I have a maple/rosewood neck from stew-mac that I bought from someone. It had a significant bow on it so I loosened the truss rod screw and removed the nut from the truss rod just to see where my "base" was. After letting it sit for a few days, I rechecked the neck with a straight edge going from the first fret to the last fret. There is a substantial gap inbetween the straight edge and the fret from 3rd fret to the 16th fret (about 1/8 inch). This problem is causing action issues through the mid section of the neck. I have cut the nut so the string height at the first fret when pushing the third fret is very very small. I have adjusted the bridge sadles(fender strat) so that it does not buzz when pushing the 12th fret. Any help is very much appreciated! |
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| Author: | Rod True [ Sun Oct 15, 2006 12:45 pm ] |
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So, your saying that you have no tension on the truss rod at all? Is this correct. Also, the bow of the neck from the description sounds like relief not back bow. There is a gap when you hold a straight edge from the nut to the end of the fretboard between the bottom of the straight edge and the top of the lowest fret. Is this correct. 1/8" gap is huge. I don't think you can correct this with the truss rod only, it sounds like the fretboard needs to be re-leveled first, than re-fretted and set up. Anyone else?? A picture of the gap would be helpful. |
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| Author: | turbo411 [ Sun Oct 15, 2006 1:21 pm ] |
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Sorry for the confusion, yes you are correct, approx 1/8th inch of relief. You are also correct that there is zero tension in the truss rod. Is there a commonly used webpage that I can post the picture to so that I can add a picture to the message? |
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| Author: | crazymanmichael [ Sun Oct 15, 2006 2:15 pm ] |
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you need to tighten the truss rod!!! |
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| Author: | turbo411 [ Sun Oct 15, 2006 2:38 pm ] |
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Thanks for the reply. This gap is present with zero string tension so I guess my point was more to the fact that is this gap so large that tightening the truss rod would put the neck in a position for damage, i.e. should other mods be made before tightening the rod to reduce the gap. Thanks 
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| Author: | Rod True [ Sun Oct 15, 2006 2:59 pm ] |
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Michael do you really think he can get 1/8" back from tightening up the truss rod? This gap, IMHO is way to big to just tighten up the rod, I don't think you would even get it flat, let alone beable to at some point put some back bow in it. Come on, some of you repair guys, Evan, Dave-SKG what do you think. Like I mentioned in my first post, I think the frets need to be pulled, the fretboard leveled and than re-fretted. Or you could use the heat and straighten method. This is where you would heat the top of the fretboard using a heatlamp and than you make up a clamping caul which looks kind of like this i---i, it's a beam with short columns at each end. You place this on the fretboard with one beam at the nut end and the other beam of course out at the opposite end. You use a clamp in the middle to correct the bow once the heat from the heat lamp has soffened the glue between the neck and the fretboard. Here is a link to some more information about bowed neck repair. Here is a rough picture stollen from another guitar forum on the heat lamp bowed neck repair.  |
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| Author: | Rod True [ Sun Oct 15, 2006 3:05 pm ] |
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Oh, as far as posting pictures goes, you use this button 
to get pictures from your harddrive onto the forum, make sure they are 640x480 as this usually will fit the screen well and also make sure that they are under 150k in size. Hope that helps. |
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| Author: | crazymanmichael [ Mon Oct 16, 2006 12:18 am ] |
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yes, i think a tr can remove that much relief, though to do so it is advisable to use a clamping set up such as you illustrate to slowly straighten the neck a bit, then adjust the rod whilst the tension is held by the clamp, snd repeat in stages. if you use heat, the heat must be applied over the length of the fb/neck joint. to apply the heat in only a small area as you illustrate won't do it. if using a lamp, the heat is applied over the length of the neck, then the clamps are applied after the neck is hot. whilst when i started a lamp was the most common method, along with an alcohol lamp, i've been using a heating blanket for quite a few years. |
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| Author: | Rod True [ Mon Oct 16, 2006 12:43 am ] |
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Michael is correct in that you need to make sure the entire run of the neck/fretboard is heated. I see that I wasn't totally clear with that detail. The sketch isn't my own, rather one taken from another website. The heat blanket would be a great idea of course, if you have one the width of the neck, otherwise I would think the wider ones, for side bending would be to wide and long and would really damage the finish when drooping over the sides of the fretboard. |
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| Author: | turbo411 [ Mon Oct 16, 2006 2:21 am ] |
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Thank you for the information. Just a few questions 1) Is this procedure under the assumption that the finger board has the bend creating too much relief or both neck and board? 2) Am I essentially just loosening the glue and pushing up attempting to have the new position hold straight by virtue of the glue holding or am I actually using heat to bend the neck and fingerboard wood? 3) What kind of heating blanket do you recommend? Assuming I complete this project my next thought was to build an accoustic and bend the sides. If I'm going buy a blanket, it would be great to use it for both purposes (noting the above cautions) Thanks! Sorry for all the questions |
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| Author: | Rod True [ Mon Oct 16, 2006 4:27 am ] |
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1) It is most likely the neck, not the fretboard, usually there will be some back bow because of the frets being "forced" into a slightly smaller slot that the outer dimension of the fret tang & barb. 2)I'm not entirely sure, but I believe that you will be straightening the neck so as to correct the bow in it, not to try and make the neck conform to a straight fretboard, I think that may be nearly impossible as the neck is stiffer and stronger than the fretboard which is thinner than the neck. 3)LMI sells a blanket for fretboard removal, but it is a different size than the blank for bending sides. I sure you could use the side bending blanket for loosening the fretboard, but I don't think I would do it personally. I would use the heat lamp method if you didn't have the proper heat blanket. You will have to decide this for yourself. I'm hoping one of the more experienced repair guys out there chime in, as I'm mostly in uncharted territory, just have done a ton of reading. I have removed one fret board in my short guitar building hobby though. I can hardly call myself a repair man, but I would feel confident in trying out most repairs if needed. |
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| Author: | 1bordeaux [ Mon Oct 16, 2006 9:25 am ] |
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Did you try and tighten the TR nut? I've seen many necks with this kind of relief, which had never been properly set up, adjust fine. I would snug the TR nut on, then try 1/2 to 3/4 turn. Let it set a few hours, check with your straight edge, then repeat. If you get it close to straight, be sure to sight down both sides of the neck to verify there's no twist in the neck. If this goes well, bolt it up, add strings and check relief at pitch. On a strat, I usually look for .008-.010 relief midway between the 1st fret and the neck/ body joint.(Capo the 1st fret, hold down the E string at the neck joint, then use a feeler gauge at the mid point.) Good luck! Paul |
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| Author: | Shane Neifer [ Mon Oct 16, 2006 9:54 am ] |
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Another method to straighten that out would be to remove some of the frets in the low area and replace with frets with oversize tangs. I am just reading about all that in the StewMAc fretting book. They have used it a lot in the past appearantly! You would stagger this at first and monitor your progress. So in your case like start with the #7, 9 , 11 or something like that. Good Luck Shane |
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| Author: | Rod True [ Mon Oct 16, 2006 11:27 am ] |
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[quote=Rod True]I'm hoping one of the more experienced repair guys out there chime in[/quote] Having not known that crazymanmichael was a seasoned veteran in the repair department, I may have steped on his feet here. I'm sorry Michael if it seems like I have disregarded your input and experience. That was not my intention. Just looking for more input that's all. I'm sorry again. |
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| Author: | turbo411 [ Mon Oct 16, 2006 1:47 pm ] |
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Thanks to all who took the time to reply. I have some good ideas and will try them. I will update the results. |
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| Author: | Louis Freilicher [ Mon Oct 16, 2006 6:46 pm ] |
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Just to clarify the way the heat bend method works. You are in essence taking advantage of the heat sensitivity of tightbond (or similar yellow glues) these glues begin to soften at around 150 degrees. So, you heat the neck / fingerboard joint to allow the joint to slip slightly when you clamp it. When it cools and the glue cools and hardens and the neck should hold in its new position. (Hopefully straighter than when you started!) This trick will not work on older instruments assembled with hide glue because hide clue does not creep under heat. This method is by no means fool proof. You need to get a feel for where to place your blocks and how much pressure to apply. But it can work wonders for badly warped necks and necks with no adjustable truss rod. I would put some tension on your truss rod and string up the guitar with some nice light strings and see what happens before I tried to heat bend it. Good luck! Louis |
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| Author: | pharmboycu [ Tue Oct 17, 2006 4:24 pm ] |
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Or, you can do what I recently did with an old Teisco Del Ray neck-- clamp it as shown in the diagram above and stick it in your oven at 150 degrees F. Bake for 20 mins, take it out and let cool. Worked like a charm! |
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