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How do I remove the back from a ukulele? (Read 8491 times)
unkabob
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How do I remove the back from a ukulele?
Mar 4th, 2009 at 6:28pm
 
I have messed up on the bracing on my pineapple design. The middle back brace shound be located at the high point of the sides. With the brace located too far forward of that, the back bellies in at the high point and you get a dull sound.

I have removed bridges using a hair drier but the area of the back is too big for that. I have heard of using a heat lamp and sheilding everywhere but the kerfing and head and tail blocks.

I have to do all three but I will start on the worst one.

Any help would be appreciated.

Bob  Embarrassed
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Zippyzingo
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Re: How do I remove the back from a ukulele?
Reply #1 - Mar 4th, 2009 at 9:18pm
 
Bob,
A lot of guitar repair techs use a hot knife to work under the edge of  the glue joint.  The "knife" needs to be very thin.  A wide, thin artist spatula heated by a torch or perhaps boiling water is a good choice. I have a couple that are 1.5 inches wide with a rounded tip. I thinned the edge of one a bit without making it very sharp. I heat this one and  use it to work the separation  while the other can be used as a wedge. You need to work carefully and give the heat a chance to melt the glue.  You may also want something like Popsicle sticks to keep the back separated from the sides while you work.  Take your time and you will be OK.

ZZ
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unkabob
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Re: How do I remove the back from a ukulele?
Reply #2 - Mar 5th, 2009 at 3:20pm
 
ZZ:
Thanks for the information.

I think that those wooden (round) shish-kabob sticks would be better than popcicle sticks because they would have less surface for the melted glue to re-stick

I am still wondering how to get the separation started. The tail block seems a safe place to start.

If I get good at this process, a friend has a mandolin that needs a brace reglued.

Bob
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Zippyzingo
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Re: How do I remove the back from a ukulele?
Reply #3 - Mar 5th, 2009 at 8:38pm
 
Bob,
I  don't know how big your tail block is.  If it's fairly wide and thick, it may be easier to start a little higher up the side and be able to get to  one of the sides of the end block as well as it's back edge. If it's fairly narrow just start where you said.  You'll have to make that call.

I don't know how thick your finish is but careful use of an exacto knife may be needed to cut through part of the finish before you start.  If your finish is thick you may need to cut through the finish all the way around the body to help avoid chipping.  

You might try heating an area of the seam with a blow dryer or even a good old fashion Hot water bottle  to help you get started.

Your mention of pulling the back off of a mandolin makes me think to caution against leaving thing apart too long. If you have a mold for the uke you may want to put it back into that while you work. This will help keep everything better aligned. Things can "move around" when you remove a top or back and getting it all back straight  can be a bit of a problem.  If the mandolin is old, you should be particularly aware of this.  If you can rig some way to hold it while working, it would probably be easier to reassemble it without some overhangs.

The skewers are a good idea. The bambo skewers I find around here may be long enough to span the width of the body.  I should also clarify a point in my post earlier.  I said I use a "torch" to heat my knife but I actually use a Bunsen burner.  You don't need a blasting flame like a propane torch gives you but a candle really won't work either. You may be able to do it with a sterno can but I haven't tried this. The idea is to be able to reheat the blade fairly quickly but you don't really want to be burning the wood either. You want the blade hot, not red hot.  I don't know what kind of glue you used but a little moisture in the joint as you work can help too. Just  don't overdo it. Take you time and don't force anything.

ZZ
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obmissy-
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Re: How do I remove the back from a ukulele?
Reply #4 - Mar 6th, 2009 at 9:13am
 
I've done it two ways.  Yes I have had to remove a back more than once to fix an error.  The first time I removed the back I sanded it off and just made a new back.  Not a big thing because it was mahogany and not that expensive.
The second time I removed a back I used my heat blanket...the same one I use to bend sides. I placed it on the edge where the back meets the sides and waited for the steam to loosen the joing.  Then I used an exacto knife to start the seperation and followed through with a scraper until the back was off.  The finish had to be re done but for the most part it was fairly easy and when all was said and done you couldn't tell the back had been removed and then reassembled.
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unkabob
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Re: How do I remove the back from a ukulele?
Reply #5 - Mar 6th, 2009 at 4:42pm
 
Thanks for the help.

I ended up using an iron to heat it. The butt-joint separated at the tail block. I finally got started on the side and worked around to the heel and to the tail block last. The back may be reuseable. I would hate to do all the sanding again.

Next task is to remove the existing brace and make the new brace and glue it in place.

I should have checked the board before I started.

Bob
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Re: How do I remove the back from a ukulele?
Reply #6 - Mar 8th, 2009 at 4:34am
 
Bob,

Glad to hear you got the job done.This Friday I did exactly the same repair you did. My mistake was letting the heel angle change while I was gluing on the back.

I ended up using a clothes iron, also.  I fashioned a crude spatula out of a thin putty knife blade and attached it to the iron by drilling holes in the blade that lined up with 3 of the steam holes and screwed it on.  With the heat turned all the way up it took 2 hours.  I started at the tail and work one edge at a time toward the heel.

Set the iron on top of the wood to loosen the heel and tail.  That caused a bit of scorching on the back and separated the back joint at the heel end because the iron was still too hot from all the previous work.

Did you use the iron on top of the wood all the way around, similar to what obmissy did with the heating blanket?  I am curious because I would like to have a plan for the next time I have to do something like this  Embarrassed

Obmissy,

Sounds like you were pretty successful.  I thought about doing it by your method, but chickened out for some reason.   So did you wet the back around the edges before you applied the blanket?  Also, what kind of temperature did you apply, the same as for bending sides?

Thanks,

Mark
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Thanks, Mike and Asa!
 
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unkabob
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Re: How do I remove the back from a ukulele?
Reply #7 - Mar 8th, 2009 at 7:16am
 
Mark:
I had no scorching but mine was already finished in truoil.
The razor knife that I used cut up to the surface over the tail block so I am seriously thinking of replacing the whole back. Mine is a three piece back because I have good access to three inch mahogany but my saw won't cut larger pieces. Both butt joints separated at the tail block.

Next time:
I will dull the razor knife on a sharpening stone before I use it. I want it thin but dull.
I will start on the side and work to the heel and tail-block.
I will only use the iron on the outer 3/4 of an inch at 3/4 heat.

Bob
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Zippyzingo
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Re: How do I remove the back from a ukulele?
Reply #8 - Mar 8th, 2009 at 8:40pm
 
Hi Guys,
I'm glad it worked out for you. Personally, I don't think I would use a laundry Iron for separating thin material like this.   On a fingerboard or something with more mass, it can be a good way to heat things up quickly but I want better control over the amount of heat and the location of heat I use to separate thin material.

 My concern is that applying a lot of heat to a general area will also weaken the glue joint to all of the blocks; Head, tail and lining around the body.  Using a heated knife gives me more control over where I am applying the greatest heat.

It's possible to use a hot knife to remove the back with the seams and finish intact.  It takes patience but I think it is less likely to cause damage that needs to be repaired later. My knives are not sharp, just very thin. I don't really cut the joint so much as I melt it.

ZZ
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unkabob
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Re: How do I remove the back from a ukulele?
Reply #9 - Mar 13th, 2009 at 8:02am
 
ZZ:
What shape of pallet knife do you use?
I picked up two different styles yesterday at the dollar store (my favourite emporium) but I don't know which to use. One is rectangular and three inches by3/4 while the other one is trowel shaped and 2 1/4 inches.
TIA

Bob
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Zippyzingo
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Re: How do I remove the back from a ukulele?
Reply #10 - Mar 13th, 2009 at 10:10am
 
Bob,
I'll try to post a picture of the knives but I may not get a chance to do this until tomorrow.

ZZ
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Zippyzingo
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Re: How do I remove the back from a ukulele?
Reply #11 - Mar 13th, 2009 at 8:02pm
 
Sorry, Bob, I can't figure out how to get the images on this post. Follow the URl and you will find a picture of my two favorites for this.
http://www.zooomr.com/photos/zippyzingo/

The top one is dark from heating it over a flame. It is very thin but not sharp.  Technically, it is something called  an"Alginage spatula", used in the dental trade to mix some of the materials used in moldmaking.  It's thin and very flexible. You can see that it is also a bit curved. It didn't come that way but it works very well like this, particularly when working under a bridge or finger board.
               
The bottom one is a plaster knife from a dental supply house that is made just a bit thicker so not quite so flexible.  Either one could be made from a putty knife. The hardest part would be thinning them out must a bit without ruining their flexibility and temper.  (just don't overheat them if you grind them down a bit. )

I found a link to a dental lab supply company that carries examples of these sorts of spatulas.  http://www.pearsondental.com/catalog/product.asp?majcatid=614&catid=4753&pid=178...

I forget to take a picture of a small square putty knife that I sometimes use, heated in a flame, along with the round headed spatulas. Is just a wooden handled putty knife with the corners rounded a little so they won't dig in, and the edge thinned down a bit.  Sometimes you need a straight edge but I think the round knife is easier to handle, particularly when just starting.

ZZ
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Re: How do I remove the back from a ukulele?
Reply #12 - Mar 14th, 2009 at 6:09am
 
Bob:

I just read a tip in the current issue of Wood Magazine (page 17) using a cloth bag filled with rice which was heated to hot condition (almost too hot to handle) in a microwave and used as a heat transfer blanket to release glue.  The bag used had 3-4 pounds of rice, but you could make the bags smaller or with different shapes for working areas like the heel block.  The idea is while it isn't as hot as an iron you can leave it in place for about 15 minutes for the wood to absorb the heat and soften the glue.  This would also be less damaging to the finish.

In the past, I also saw a method for attaching an Xacto knife blade to a wood burning tool for cutting open glue joints.  Since a wood burning tool is designed to scorch wood it is probably too hot for working with ukuleles, but is another option for stuborn glue joints.

Don
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Re: How do I remove the back from a ukulele?
Reply #13 - Mar 14th, 2009 at 2:39pm
 
Actually, Don, it seems to me that a hot Xacto knife blade wouldn't be bad for a small instrument because it focuses the heat where you want it.  I wouldn't want to try prying anything loose with it but a flexible putty knife could follow the Xacto blade. You don't want to pry too much anyway.     

I've got a couple of low wattage soldering irons laying around and I've got a mandolin that I need to open up. I've been dragging my feet on doing it because... well because it's going to be a complicated repair and I never see to get my ducks in a row on it.  Maybe I'll rig a blade for one of the irons and try it on this sometime.

ZZ
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unkabob
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Re: How do I remove the back from a ukulele?
Reply #14 - Mar 14th, 2009 at 5:30pm
 
ZZ:
Do you expect to have any problems with the curved back of the mandolin? I have been hesitant to try it.

Bob
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