gibson j45 questions

[paco123]

Hi folks.

I am the new owner of a 2 yr old beautiful j45 rosewood. I have a couple of questions regarding set up and action. I bought the guitar knowing the action was high but could see no other issues. After changing strings and straightening neck I realize the the top may have been over humidified. It has been a very humid summer in the prairies. My basement is about 50% RH and I have it sitting on a stand hoping the top will settle. I followed this web site's instruction for set up and this told me about the bulge.

 

http://thbecker.net/guitar_playing/guitars_and_setup/setup_page_02.html

 

My questions are: how much arch should there be in the top? Will letting it sit out withe the strings loosened help settle the top down (de-humidify)? if I run a straight edge down the frets should the end of the edge sit on top of the bridge?

 

Thank you in advance

 

Mike

[rar]

My questions are: how much arch should there be in the top?

 

Gibson tops have a 28' (= 336") radius. Hence, on a J-45 (which is 16" wide) the gap on each side when a straightedge is laid across should be around

 

( 336 - (336^2 - 8^2)^0.5 ) = 0.1"

 

Of course, a little more when the top is under tension is not a problem. Certainly, say, 1/8" would be fine.

 

Will letting it sit out [at 50% RH] ... help settle the top down (de-humidify)?

 

Eventually, assuming that humidity is the problem (in which case, no need to loosen the strings). But a seriously over-humidified quitar can take months to dry out.

 

if I run a straight edge down the frets should the end of the edge sit on top of the bridge?

 

It should be about even with the top of the bridge, but lower can have causes other than over-humidification (e.g., a bad neck angle).

 

-- Bob R

[paco123]

Thanks Bob,

that does help alot. I played a friends j45 a couple days before buying this one and I checked his out because of high action at 12th fret and same deal. The bridge seem higher than the fret board. His guitar is only a few months old and my guitar hardly got played and left in case with planet waves humidifer in it consistantly. i'll take it to a luthier and see what they say.

 

Thanks again.

[RASHARU]

Please keep us posted on what you find out. I absolutely LOVE these technical learning threads! ( ..great explanation RAR )