You are currently viewing Kit Guitar Forum archives. To view the current forums go to www.KitGuitarsForum.com/board



Log-in
Register
Members


Pre-bent sides are too relaxed!
Author
Post
mbbransc

Total Topics: 13
Total Posts: 71
OK, virgin builder here but I want to get started.

I just won this kit on eBay and I already see I will have to do some work on those sides. I think I'll have to build myself an external mold to get it back in shape.

My question is, how should I handle that so that I don't crack the sides? Heat? Water? Anyone have any experience with anything like that?

thx
Brandon

Aug 19, 06 | 8:33 am
Bill Cory

Total Topics: 158
Total Posts: 3584
Brandon -- I checked out the kit. It looks like it's been around awhile. the Stewmac plan won't fit the Martin kit exactly, but it will be close enough.

The kit looks okay. Don't do anything extreme to it like "heat" or "water": heat improperly applied would dry and crack it and water would make it want to relax more, worsening the problem. Humidifying and molding slowly will do it.

1) Stabilize the humidity of the wood parts by storing them in a room of from 40 to 50% Relative humidity for at least two weeks. Like all our moms used to say, "You don't know where it's been!" If the seller's "friend" is from Seattle or from Phoenix, it makes a difference.
2) Go to the hobby store and buy some foamcore.Cut out the shape of the guitar from the full size Stewmac plan and fit the sides into it. Do this BEFORE you start building your external mold, and put your foamcore and sides in the humidifying room. In two weeks or so, they will be close enough to the original shape that you can put them in your external mold and not have a problem.

Did the Martin "Manual" come with the kit? If not, you're not missing much. Just forget it ever existed and your kit will turn out better. Go to www.stewmac.com and download from "free information" their manual on their dreadnought kit; it is close enough to the dread kit you have and much better than the sketchy manual from Martin.

If you want some good detailed instructions, go to www.KitGuitarBuilder.com and follow the steps in the "Martin Instructions" pages -- almost showing the complete kit. (It's a jumbo, but that has no bearing on the process.) The instructions shown follow the Martin manual and make up for its shortcomings.

Good luck.

Bill


Aug 20, 06 | 6:26 am
mbbransc

Total Topics: 13
Total Posts: 71
Thx Bill, a couple of follow up questions...

1. When you say '... 40-50% relative humidity...", what exactly does that mean? I know I need to let the wood acclimate to its new humidity level, but your statement stumps me. Should I lock the kit in a spare room with a humidifier?

2. I've seen foamcore mentioned before. You say cut out the shape and fit the sides 'into it', but do this 'before starting my external mold'. I'm confused by this. If I cut the shape out of foamcore and put the sides into it, wouldn't the foamcore basically be an external mold? Or were you recommending do that prior to making an external mold from wood?

I've followed your steps on KGB site. I have also downloaded the StewMac directions from their website. I'm sure I'll be referencing sources over and over before making any decisions.

thx again
Brandon

Aug 20, 06 | 9:41 am
Bill Cory

Total Topics: 158
Total Posts: 3584
Brandon -- "Relative humidity" is what is meant by "humidity"; it varies with temperature, which is why it is called "relative" humidity. 40-50% RH is recommended for most guitar building. An acoustic guitar body can usually handle humidity changes within normal ranges if it's built somewhere in the 40-50% range. If it's built at 70%, for instance, and then moved or used in a 30 or 35% environment, its glue joints are likely to fail or cracks may develop. Reverse the numbers, and similar problems arise. It happens all the time. I live in Colorado, and we often had people come into the shop where I worked who had moved from the south or east. Some had damaged guitars because they had moved from 55 to 65% RH to 30 -35%, and then in the winter, used central heating and lowered their house'es RH to about 18 to 22%. Nobody had told them what humidity changes do to guitars.

An example: My garage, where my shop is, hovers at about 25 to 30% humidity. There's no point in trying to humidify it to 45%. In a small storage room, though, I have a humidifier that does keep the humidity at 45%. When humidity is too low in the garage (which I know from keeping hygrometers in both areas) I keep everything in my little room, and carry parts to the garage where I glue them. When the glue has dried, I put them back into the 45% room if the garage is low. Maybe I'm overdoing it, but not according to a number of luthiers I've talked with about it. I'm sure the guy who lives in North Carolina for whom I've just finished building a guitar will appreciate that the guitar doesn't have to leap from 25% in my garage to 60% in his house -- a leap that might damage it. It can easily handle going from 45% to 60% though.

2. What I meant was this: It will take you awhile to build your external mold. If you make a temporary one in a half hour out of foamcore (or cardboard or whatever you have handy), the sides can be forming to the correct shape slowly while you complete the external mold -- which I assumed you meant you would be making of wood. The temporary mold will give your sides a head start on reshaping themselves. If you don't like the idea of allowing the wood to gently reshape itself, go ahead and force it into the wooden mold when you get it made; the worst that can happen is that you'll hear a cracking sound ...

Aug 20, 06 | 11:05 am
mbbransc

Total Topics: 13
Total Posts: 71
LOL!!! CRACK... is definitely not what I want to hear!!

Someone at my church works at Hobby Lobby so I'll get her to pick me up some foamcore. Thx for the tips and I'll let you know how it goes!

Aug 20, 06 | 1:26 pm
Bill Cory

Total Topics: 158
Total Posts: 3584
Good luck with it. Let us know how it goes. I was thinking, it's neat that you were able to get that kit within your budget.

Aug 20, 06 | 3:09 pm



You must be a registered and logged in member to post in this forum