How much should it belly out?

[tomcat5]

Hi Everyone!

I live in the tropics where it is pretty high humidity all year round (70-80%). Have been watching my LV-03RE quite closely over the past 4 weeks since I've gotten it and it seems that the top and back might be starting to belly up a bit. My room is air-conditioned at night till the morning (about 45% RH) but during the day windows are opened and the guitar is on a stand.

From Larrivee's factory tour, it looks like the top and back are perfectly flat before assembly. My guitar top is mostly flat with about a 1mm gap at the sides if i put a straight edge across on the side of the bridge nearer to the soundhole. On the side of the bridge nearer to the butt of the guitar, the gap is a lot bigger - about 3mm.

With the back, it is definitely a lot more bellied. Roughly a 7-9mm gap throughout if I put a straight edge across.

I've got two questions:

1. Am I right to assume that the top and back are flat before assembly? Is it supposed to be bellied at all after that? I'm starting to get worried that the braces might come off.

1. How bellied are the top and back supposed to be? i.e. What is an acceptable range?

Thanks in advance!

shaowen

[Ratishna]

Most acoustics are built with a slight amount of arch to the top.  I wouldn't worry about your braces coming off.  I've see guitars from the 1930s where the area behind the bridge had lifted up nearly half an inch.  The braces were still there.

E. Shoaf

[Randy_R]

I'd recommend putting the guitar in a case during the day when its not being played if the humidity is that high.

[Fergy07]

a case would even out the humidity to a more linear range.

[saffron_boots]

Just to reitterate, some arch is normal. I build using a 15' radius bowl for the back and 25-28' for the top. If you're concerned about top swelling caused by overhumidification, here's a quick check:

Put your straight edge across the top, from base to treble side, on the lower bout just over the end block. If there is a concave gap in the top just above the end block, you guitar is too wet. This is because the top is glued to a significant piece of wood and is unable to swell with the rest of the soundboard. Cure? Do what Randy_R said.  :WNK>   

[Steve]

Hey tomcat,

We had another member here that had a wet L-03R, Dru from Australia.  He got his guitar dried out and you can really see it in the pictures below.

Wet guitar and then the dried out to 40% guitar.



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[tomcat5]

wow, this is really cool stuff. thanks to everyone for enlightening me. i didn't think of measuring the lower bout near the end-block. will try it out when i get home tonight.

incidentally, i have put the guitar into its case with silica gell and left it in there for about 2 days now. however, the RH seems to be at 65% all the way even though the room is at about 40+% with the air conditioner on. i would think that the RH with the silica gell should be even lower than in the room. am i doing something wrong?

think i'll start a new thread on this.

[Randy_R]

the inside of the case may have absorbed moisture by being open during periods of high humidity.

Open the case when humidity is low & close it when high. Eventually it'll even out.

The silica gel may need drying out in your oven...

[tomcat5]

Yup, was thinking that it is either the guitar or the case that is putting out all the moisture. The silica gel has been baked once already. It didn't really turn pink yet though. Most of the gel was still pale blue when i took it out to bake.

[Dru]

Tomcat5, I own the guitar that SteveK has posted pics of above. I live in sub-tropical coastal Aust where lowest winter RH is around 60% & summer RH goes off the scale. My guitars are always in cases when not being played. Our "summer" lasts for around 6mths. At first I thought someone had sanded a "huge" depression over the tail block! Then SteveK and others calmed me down on my crazy sanding theory & convinced me the guitar had "wet guitar" problems. SteveK also posted a link to the Taylor site that describes the problem.

To solve the problem I put 150grams of the same silica you're using in the sound hole with guitar in the case and checked the RH every 24hrs. After a couple of drying cycles with the silica I caculated it took out 25mls of water from inside the guitar. As you can see from the pics the swelling has gone. I'm know aiming to keep the RH to around 42% as that's what I read that the Larrivee factory keeps there bodies at during production.

 

[tomcat5]

Holy cow Dru. That sounds like a lot of water. Don't have a scale handy. Is 150g of gel about two  hands full (cupped)? Have you managed to reach 42%?

One final question. In your drying process, did you wait till the gel turning clear/pink before baking them or you just went ahead and baked them after a set time?

Thanks!

[Dru]

TC5, Yeah it sounds like a lot of water. To calculate what I did was to simply weigh the silica before & after drying it in the oven. Post drying weight is approx 150g or around 3/4 standard cup measure. The difference in weight being the amount of water held by the silica [ 1gram = 1ml ]. I left the silica in the guitar for a week before drying. At that stage it was a light pink.

I also have another 100g of silica in the case under the headstock. I'm now getting a fairly constant 40/42% reading and I'm working on the assumption that every time the guitar is out of the case it's taking on water. I'll be adjusting these weights if I start to get sub 40% RH readings. Seeing that I have fairly high RH at all times I have been drying my case weekly in the sun for 1/2 an hour. Then I bring it inside to cool before I store my guitar.

Funny thing about all of this, I've owned Aust made Maton acoustics since the '70s. When I first asked for advice about this problem on the forum I was saying " Well my Matons have never had any humidity problems." SteveK pointed out an update on the Maton site warning about excess humidity. Well then I also egg on my face ;) Thing is that I've done the same silica drying with my Matons and although they've never dramatically changed shape, they're really singing now ! Seems all that water really dampens the tone.     

[wyodeb]

I think I read somewhere about periodically using a blow dryer on the inside of the case to help dry it out. Living in Colorado, Wyoming, and western South Dakota, I usually have the opposite problem. Water the houseplants, water the guitar humidifiers... We have had some rain lately, so some drought relief might be in sight.

Deb

[tomcat5]

i think my case must be really wet then. left in an A/C room for two nights, blew dry it for at least 30 mins. still can't get RH below 60% even with 500g of silica gel (the whole bottle!).

sigh. wet wet wet.

[Dru]

TC5, Do you mean that the case won't go below 60% RH or the inside of the guitar ? When you say you live in the tropics [ without trying to sound nosey ;) ] where would that be ?

[tomcat5]

I've done two things:

1. 500g Silica Gel + empty guitar case = 60%Rh

2. Roughly 50g Silica Gel inside soundhole + hygrometer on top of guitar = 65% (but this was two days ago before i started to try and dry the case out.

I live in Singapore. wet wet wet :p