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Recently, while trying to glue my latest top on, one of my go bars slipped, causing a four bar explosion! Thankfully no one was hurt, but in the process I got a pressure ding in my top. It,s not very deep, but long, and I'm a little bummed. I thought I read somewhere about using an iron to bring out a pressure ding in a top. Anyone out there with some ideas? I'm thinking of just trying to use a little epoxy to drop fill before finishing, but would love to be able to get it out.

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change isn't synonymous with improvement
instagram.com/bucketguitars/

http://www.youtube.com/watch?v=pDSQ7u_ii00
here is a vid on steaming out a dent.
To save you from doing the dent thing again . Use a heavy foam pad . I make a halo patter to fit the outside of the shape , then inside I cut heavy foam like a floor anti fatigue mat , that way if a gobar slips , It won't hit the top or back.

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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

I would certainly try steaming it out. Just take a damp papertowel soaked in water and place it on top of the dent (perhaps squeeze a drop or two of water into the trough if it is deep enough) then place a hot clothes iron on top of the dent and steam away. This will often remove most of the dent, then let it dry, smooth out the raised grain by resanding, and then continue on with the bracing.

Good luck

John, you rock!!!

Thanks so much. By the way. This guitar I'm building is from a Martin o-18 drawing you sold me. I made a great mold, and bracing template from it. Thanks for the service and help!

Sean

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change isn't synonymous with improvement
instagram.com/bucketguitars/

Sorry to hear about your explosion. But that is some great advice from John. I've never thought of making a foam protection pad. I think I'll be trying that soon. One can never be too careful.

I use poster stock ~0.040" or so cardboard with the white finish to protect the top when I glue it on the deck.

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Steve Smith
"Music is what feelings sound like"

So, Todd, can I assume you had your tongue in your cheek when you said on my other go-bar thread that you used 96 go-bars to close the box ???

I'm seeing like 30 there , give or take a few ...

96 go-bars? That's almost 700 pounds force. One of these days we are going to be treated to a picture of a go-bar induced guitar implosion.

To prevent go-bar deck "explosions", make sure the guitar pieces can't move around at all, that the bars are "sticking" in place (carpet at the top if necessary), and that the dish and any height spacers or sub-structure you have underneath the guitar/dish can't move at all either. This is critical. Every GBD "explosion" I have experienced has been due to the dish moving (spinning) a few degrees. Nowadays, I clamp the dish surface to the bottom of the GBD in at least two places before glue-up and putting the rods in.

Best way to undent a top is the Frank Ford method. Use an eye-dropper or similar small liquid dispenser to carefully place a few drops of 99% alcohol right in the dent. Don't get any on your hands or spill any anywhere else. If you do, wipe it all up, let it all evaporate, then start over. Set light to it immediately (making dead certain that you have moved the dropper, alcohol bottle, rags etc. well away from the work area first!!). Only the alcohol will burn. It will burn itself out in a few seconds. The dent will - amazingly - be gone, or almost gone! You can repeat the operation to undent it further if need be, but leave a few minutes between burns - if you don't, the wood will start burning too!! I've done this on several dings/dents now and I'm always amazed at the results - much better than steaming, which is how I used to do it.

Good luck,
Dave F.

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Cambrian Guitars

"There goes Mister Tic-Tac out the back with some bric-brac from the knick-knack rack"

Dave, I wonder why that works? Would it work on a top with polyester finish?

I use spring-loaded go-bars. I've never had an "explosion".
I've never heard of anyone who has. (Waddy, have you?)

Hi Mike, I'm really not sure, but I think it has to do with the intense localized heat that forces the alcohol that's soaked into the crushed wood fibers rush up to the surface to be burned and in doing so, it pulls the fibers back up, plus the localized heat makes the crushed fibers elasticate and expand.....probably a load of you-know-what, but it's the best I can come up with right now. Fact is, it does work, and very well indeed! I wouldn't try it on anything other than bare unfinished wood though!! Any finish is likely to catch fire and destroy the instrument IMO! Give it a try and report back to us if you like Mike!

Cheers,
Dave F.

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Cambrian Guitars

"There goes Mister Tic-Tac out the back with some bric-brac from the knick-knack rack"

Never!

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Waddy/Eric, a few questions if you don't mind:

1. What is the max length movement your sprung go-bars have?
2. What accuracy do you have to adjust the work height to (with height spacers under the dish) to get the spring force in the "right range" for any particular glue-up job?
3. Do you have, or know of, a build tutorial for them?

Thanks,
Dave F.

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Cambrian Guitars

"There goes Mister Tic-Tac out the back with some bric-brac from the knick-knack rack"

I cannot speak for Waddy/Eric, obviously, but here is my take FWIW, from a total noobie first builder..

I started another thread on go-bars, and got some really valuable information from Todd Stock et al, but at the end of the day I decided that I was going to go the spring loaded route. One factor in choosing this was that it meant I could use a 36" high deck rather than a 24" high deck, which the other Todd said was really useful ...

So my go bars consist of a 24" length of 3/4" OD aluminum tube, each of which has a 12" long dowel, 1/2" dia, "fixed " into one end, (6" inside the tube and 6" outside) and a 21" long dowel in the other end. These dowels are an easy sliding fit. When I say "fixed" I mean it just has some masking tape wrapped round it to hold it in place ...In between there is a 3" long spring, which has a compression factor of 12lbs for one inch compressed. I had to buy the tube in 5 meter lengths and cut to size btw.

The dowels I bought in 8' lengths, and cut to 21" and 12" , but my cunning plan is to cut the upper 21" dowel into two sections, one at 17" and one at 4" so that I can glue up the braces and the box without having to fabricate a separate platform, all I do is remove the 4" piece when it comes to closing the box. You could vary this length and get a very exact pressure, whatever you wanted. You could have a selection of 1" long dowels, 2" dowels, whatever.

It's not a cheap way to do things, leastways this side of the pond. The aluminum costs £1GBP per 24" length, the springs cost £1.08GBP each , and the dowel cost £.060 per 36" length. It all adds up if you are making 96 go bars, like what Todd uses ...yikes ... fiberglass works out a lot cheaper ...

Still, I just feel that for me it is going to be a better way in the years to come...YMMV...

I had a tut here or over at Luthiercom. Mine are made from CPVC water pipe. I can post pics later or you can check out my photobucket album (link below) and look at gluing braces on any of my builds. Mine are about 30" with the insert and about 27" without. The ins beer is a dowel used to equalize pressure. They are removed when gluing backs and in when gluing braces.

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

FWIW, this is a pic of the spring loaded gobars I decided to go with, these are clamping down the back center graft on my first build ...

Each gobar can be fine tuned for pressure... these ones exert 10lbs each, but can easily be tuned for more or less ...




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