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So I had the sides bent, they were nicely in shape, only little springback (less than on the prebent sides I got with kits). I put them in the mold, glued in the heel- and neck block, glued in the kerfings. Everything was sanded to the final shape of the rim in the sanding dish.

Than I took it out.

Crack.

Luckily not the sides cracked, but the glue line connecting the kerfing to the sides at the waist and upper bout. And the whole rim is deformed now. One side worse than the other - definitely not symmetrical anymore.

I wish I could just stuff it back into the mold, glue on the top and back and trust in the glue to hold everything in place, but after what happened today that seems like a really really bad idea.

So what to do? Remove the kerfing, and the neck/heel blocks and touch up the sides?
Can I just put the heating blanket on the outside of the rim to soften the glue and then remove things?

Any other/better disheartening suggestion. I guess stuff like that is just what you have to go through in the process of becoming a good guitar builder. When it happened I was really disheartened, but now I see it as another learning opportunity (and my next sides will definitely have NO springback at all when I put them in the mold )

best, Christian

Bummer Christian,

I think you would be better off if you used a heat gun to soften the glue. This way you can work on one area at a time, instead of heating a large area and rushing to take things apart before the blanket scorches your rims.

Good luck!

Cal

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Christian, just put the thing back in the mould. I don't remove my sides from the mould until I have the back and top glued on. Check your glue. Glue up some scraps and leave them overnight and see if you can break them apart without less than reasonable force. If the glue is good then you probably didn't add enough to some parts and they became starved, so that fix is to just separate the area where the released enough to insert more glue and re-clamp. If the glue is bad (as evidenced by your test) then you would be better to use heat (while the sides are still in the mould) and remove the linings and the blocks and re-glue them with new glue. I was actually worried that your sides had cracked! Your issue is not really that bad.. I have had to reglue stuff on my guitar before as well.

Shane

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Canada

Hi Christian,

The only time anything like this happened to me was long ago when a side had significant springback, but I forced it in the mold anyway and hoped that the kerfing would hold it in place. Even then, the kerfing did a pretty nice job, and only pulled loose in a small area. For other builds, I've never had anything like this happen, even when I forced a side into the mold a little more than I probably should have, but too inexperienced to know better.

Did you have to force the sides into the mold? Can you post a picture?

I will say this: As nice as the Fox bender has been to me over the years, I'm fed up with the waves it seems to make in the sides, and with the springback. I've tried many combinations of moisture and temperature, and rarely do I end up with a set of sides that behaves the way I want it to. I have finally invested in a handy-dandy, old-fashioned bending iron. Maybe it's not as fast, and it may take a bit of practice, but I suspect I'll get much more control over the final shape and eliminate springback issues this way. I'm anxious to find out.

Christian, what kind of glue and clamping pressure? Maybe you starved the joint?

I find it difficult to get a perfect match also and am forcing my neckblock in a bit, but its sanded perfectly to the front end wood. My origional intension was to do the wood bending on the mold, and take the end result and make an outside mold to exactly fit the fox bender.

I think I will do that on the dred.

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I never pull side out of a mold till the top and back are on. Also how is your mold designed? I use a 2 piece mold so that if I have to I can take the mold off the body not pull the sides out of the mold. You learn from mistakes so consider this a learning experience. The mold does some very important jobs , it maintains symmetry , and keeps the neck blocked pinned for accurate location. The mold can compensate for spring back and get you an accurate shape. Check out this link so you can see how I set the geometry of the guitar. http://bluescreekguitars.com/blog/
If you sand the rim to shape and pull it out of the mold you no longer have that geometry. Now as for taking the kerfing off , that isn't that difficult but that it popped off concerns me. Some woods have more resins and can weaken the glue bond. Cocobolo is one . Are you bending on a pipe ? Anyway we are here to help you along .

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Wow, you guys who work in molds, must live a hard life. If my sides didn't stay in shape, I couldn't build a guitar at all. I take them in and out of my solera over and over before assembling the guitar. It seems to me that you shouldn't be depending on a mold to hold the shape, but only to provide support while assembling. If the sides don't fit, they should be adjusted to fit before continuing the assembly of the guitar.

This was not a criticism of you, Christian, but, just an observation on the process. Why would you build an instrument with that much tension in the sides?

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Waddy

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Awesome, thanks lot for all the suggestions. When I went down again today I realized that only one of the kerfings came loose in two places. Probably a combination of things led to this:

- Springback - I didn't have to force the Tasmanian Myrtle sides into the mold, at least not as much as the bubinga sides on my previous guitar. I'd say I helped a little to get them into shape There was a jump in humidity recently which is why I didn't work on the top yet. But maybe the humidity change affected the sides as well.

- Sanding: I sanded the sides prior to gluing with 220 grit. For some reason I didn't sand the basswood kerfings at all. No idea why - I usually sand all surface prior to gluing to 220.

- Glue: I used LMI white. It definitely wasn't the freshest anymore. It wasn't old, it didn't smell bad, but I think I'll open a new bottle now.

- Add to that the possibility of too little glue or too little clamping pressure (it would surprise me, but stuff happens...)

Here are some pics:

The mold - one piece...I'll go ahead and modify it


The rim:


One of the cracks (this is the worse one):


I guess I'll go ahead, remove the kerfings, put the sides back into the mold, and leave it there until the top/back are installed.

thanks again,
Christian

Using a mold does a number of things but most important , is the locking of the neck block. Without a mold you really cannot control this part of the building process. This makes neck setting most difficult. Today I set a neck on a build , it took me about 15 minutes to set a dovetail. The neck action will be under 7/64 on the base with a bridge saddle height of .545 . That will allow plenty of adjustment for the future.
Before I used molds I dreaded setting necks. I am not saying you cannot build without one , but it make the repeatability of process more secure. Also once you set the sides in the mold , there really is no need to remove them , this assures perfect symmetry and safety. Every time you pull sides out of the mold your change alignment and stress the sides risking cracks .
I know classical builder use Solera's and other building board arrangements. They work well with the Spanish style but we are talking steel stringed instruments. Still use what you fell most comfortable . I think I met Waddy at ASIA and he does make a nice guitar. I cannot fault his end result.

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Sorry, guys. Part of my post was "tongue in cheek". My point, really, was why put sides in a mold that don't fit? Wouldn't it be better to tweak the bend until you have stable sides and a good fit? I have a side that I bent as a test bend over two years ago, and it has been flopping around my shop now, without a mold, for those two years. It still fits the body shape, and it has been through swings of humidity from 30% to 80% during periods when I was out of town and turned off my dehumidifier or humidifier. It was bent on a pipe, as are my other sides. I plan on using a bender, at some point, but I would also expect to touch up the bend as required to fit a mold, if I were using one.

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

HI waddy
thanks and accept my apology if I got too serious . You are 100% correct , that the sides need to fit the mold . Don't assume the side will just fit.

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Update:
Turns out that only one of the side didn't fit the mold too well. So I removed the kerfings with a heat gun and chisel, touched up the waist area of the side with the whole rim intact, and it went back in the mold. I sanded the sides/new kerfings down to 220 again and glued the kerfings in (one of the two...the glue's drying as I type).
I hope that'll do. This time I won't remove the rim ntil the top and back are on.

best, Christian