LUTHERIE AMATEUR

blaireau a écrit :Il y aura bien un pro pour te répondre, mais, en faisant le "réglage" dont tu parles (relachement du truss puis accordage forcé), que se passe t'il si, une fois le manche re-courbé dans le bon sens, tu mets à nouveau le truss en tension ? est-ce que le manche se courbe à nouveau en sens inverse ou est-ce que le truss fonctionne à nouveau dans le bon sens ?

BIGSTEVE a écrit :Je mettrais la touche en presse avec des serre-joints nombreux et une cale métallique qui recouvre toute la touche (tube d'acier carré) et je chaufferais le tube avant de mettre en presse. Bien sûr, si tu la chauffes au rouge ça va pas faire! je recommencerais plusieurs fois, en laissant chaque fois le montage refroidir. Et je suis pas sûr que ça marche, mais franchement je ne vois pas d'autre solution dans l'immédiat, à part défretter et re-profiler les deux bouts de la touche à un mm de moins.
Qu'est ce que ça donne si tu mets des cordes genre 50-105, ou même les 4 graves en 60-125 d'un jeu de 5 cordes light ?

BIGSTEVE a écrit :Il y a un moyen de savoir si on peut élaborer une solution juste avec cette histoire de frettes, sans chauffage / déformation etc: Si juste tu défrettais, sans refretter, et que tu mettes les cordes en tension? ...Si le manche reprenait sa forme correcte, et que ça devienne jouable, ton idée de pied de frettes qui créent trop de compression serait la bonne! Il faudrait les changer pour soit des frettes au pied (tang) aminci (si c'est possible), soit des fentes un quart de poil plus larges : là, c'est juste une lame de scie à métaux à rectifier, et tu peux le faire avec un étau, deux limes, de la super-glu et un pied à coulisse

How to fix a reverse bowed neck... Get two padded neck clamps from stew mac(or fabricate them from ordinary wood clamps and some felt) and a stiff board. A poplar, fir or maple 1"x2" board should work. I usually cut up old pallets for this purpose. Make sure it's stiff enough that it will not give under the tension of the clamps. Get a utility lamp with a a reflector and a clamp mount and a 150 watt infra-red lamp from Home depot. Cut a block of wood about one-quarter to one-half inch thick by 1" wide- by two inches long. Carve one surface of this piece to match the radius of your fingerboard and pad it with some 1/4" felt-Or better yet, just buy a radiused clamp caul from Stew Mac. It's alot easier. Using your new clamping jig made from the parts I just suggested aquiring, clamp the neck into a moderate forward bow. Here's where some experience is helpful, but used good judgement. Don't overdo it. Sight down the edge of the fingerboard to check your forward bow...it should not be to dramatic...use a straight edge to check the relief at the 7th-9th fret. Make sure it's no greater than about 50 thousandths to one hundred thousandths of an inch. Once you have the guitar clmped and laying on your bench. Mount the infra red lamp about 12 to 14 inches away facing the back side of the neck. Turn on the heat and leave it that way. A good A/C thermometer is helpful here. The temperature at the neck should not exceed about 120 -125 degrees. You dont want too much heat. Check it by feeling the back of the neck every ten minutes or so for the first couple hours. It needs to be heated slowy and midly for a day or two. Too much heat will cause the lacquer to blister. Keep checking the neck to be sure it's not overheating. Once the fingerboard is nice and warm to the touch, leave it that way for the next twelve hours or more. Turn the lamp off and let it cool down while still clamped up. This method works but I learned it as an apprentice to a fine luthier 40 years ago when I was 12. It could be tricky to learn on your own. Just be careful and go slowly...be conservative. You can always repeat the procedure if you need to. Dont overclamp and squish the wood...be careful not to mark the finish. The other way to fix this is to refret and level the board up. Good luck.

I would not heat the neck as a initial solution especially if it is a fret tang issue. Not really attacking the source of the problem. My suggestion is to pull a fret or two, or maybe the first 5 or 6 and see if the backbow disappears. You MAY need to heat the neck because the wood may have settled into a backbow over the years but I would diagnose and repair the cause of the problem first. Plaintops method is good for the heating process.