stabilizing a crack.

[mickeyj4j]

Hi all I have a ukulele with a crack in soundboard see ukulele - Crack in Sound Board and help required.
I am wanting to stablise the crack.
1. Glue: Thin super glue. Not fussed if it affects the varnished finish. What type do you recomend?
2. Bracing: Locally in Auckland i can only find cheep thin balsa wood to use as bracing. Where can I get some stronger stuff?
3. Magnets: need some small strong magnets to hold the bracing and crack in place. Where can I get some?

Thanks in advance for any help you may have.

[kiwigeo]

Hi all I have a ukulele with a crack in soundboard see ukulele - Crack in Sound Board and help required.
I am wanting to stablise the crack.
1. Glue: Thin super glue. Not fussed if it affects the varnished finish. What type do you recomend?
2. Bracing: Locally in Auckland i can only find cheep thin balsa wood to use as bracing. Where can I get some stronger stuff?
3. Magnets: need some small strong magnets to hold the bracing and crack in place. Where can I get some?

Thanks in advance for any help you may have.

1. CA glue. I use hot stuff. My Australian Supplier: http://www.thewoodsmith.com.au/thewoods ... tuff01.htm Carbatec also usually stock the stuff. The glue wont affect your finish.....its more likely you may get the glue bleeding into the top wood and staining same. Note that hot stuff CA glue comes in three different viscosities. If penetration of the crack is the priority then the low or medium viscosity glue would be the go.
2. Balsa is for model aeroplanes and Smallman style lattice bracing. Its all about stiffness.....spruce is the most common brace material. When you say "bracing" I assume you mean "patch". For reinforcing a crack you only need some small flat pieces of wood.....I use offcuts of spruce soundboard.
3. Magnets - they're a dime a dozen on Ebay: http://www.ebay.com.au/itm/like/3215565 ... 107&chn=ps. Do you need magnets? If the crack is not going to be forced closed while the glue sets and youre going to be using CA glue....just hold the patch on with your finger until the glue sets. If using magnets then make sure you use wax paper between the magnet and the wood so you dont glue your magnet to your uke.

[simso]

I would avoid superglue personally.

Use a yellow glue like titebond, Superglue is great in our business for lots of things but joining spruce IMO is not recommended.

Steve

[kiwigeo]

I would avoid superglue personally.

Use a yellow glue like titebond, Superglue is great in our business for lots of things but joining spruce IMO is not recommended.

Steve

Not my first choice either. Rub some titebond into the crack from underneath and then slap some patches along the underside.

[dshaker]

Another vote for Titebond.

Note: that's Titebond regular, not Titebond II nor Titebond III nor Titebond Instant. It usually is pale yellow in a bottle with a red label.

[mickeyj4j]

I would avoid superglue personally.

Use a yellow glue like titebond, Superglue is great in our business for lots of things but joining spruce IMO is not recommended.

Steve

Not my first choice either. Rub some titebond into the crack from underneath and then slap some patches along the underside.

Ok so by patches you mean cleates. Small pieces of vaneer or thin wood at 90deg to the crack to stablise it. But how to hold them in place clamps won't work.

[simso]

I recently posted a walk through

viewtopic.php?f=1&t=7538

Feel free to ask questions after viewing, personally I am not a fan of magnets to close cracks, they are just fine for holding cleats in place whilst drying, others may have had more success than I with magnets.

Steve

[blackalex1952]

Hide glue is also good. One reason for hide glue is that it will re stick to itself in case of a misalignment, so more mistake proof. But for a small job use Titebond. Superglue can discolour spruce, it gets a green tint to it. It is good for drop filling some finishes. The reinforcement of the crack is best done on a soundboard with cleats- image search diamond or pyramid sound board cleats. Here is an image of nicely made cleats:http://www.strangeguitarworks.com/wp-co ... G_2758.jpg
The grain of the wood in the cleats has to be at right angles to the grain of the soundboard. The pyramid shape is the lightest shape that maintains a good strength. The violin luthiers trick is to use a suitably curved and pointed wire to reach inside the instrument to position the cleat. The point on the wire is driven just into the top of the pyramid to hold it. Glue is applied to the pyramid base, then the cleat is rubbed then held in position until the glue gells and grabs. A flick of the wrist so to speak and the wire comes out of the cleat leaving the cleat in position. Glue the crack prior to cleating, of course. If the crack can be rocked so that the edges of the crack rub, glue can easily be worked from one side of the crack to the other. Failing that, there are a few tricks out there...on is to try a suction cap-YouTube is becoming the luthiers friend! The suction cap idea is on a Stewmac video somewhere. I have even used my vacuum pump to suck glue into a join.
I usually apply the glue from the outside of the soundboard with a mirror on the inside. That way, the finish prevents the glue from spreading everywhere and leaving a stain as it would if you work the glue in via the unfinished timber on the inside. It can be seen in the mirror when the glue has worked its way in. Magnets to clamp are good on flat surfaces. (For some side repairs, I have used a tuning machine on a block of wood with a guitar string end (ball end) through the crack via a small hole with a curved shim on the inside. Glue is applied then the tuner tightened.)
Superglue can be a drama, if that's all that is available be vigilant and quick! Unless you use a slow hardening version. I have seen an almost invisible crack which I superglued, and the glue went off suddenly when the edges of the crack weren't properly lined up, yielding an obvious and poor result. Difficult to undo and redo. I was lazy and in a hurry with a hide glue pot staring me in the face the whole time!!
-Ross

[kiwigeo]

Superglue can produce a yellow stain if used on light coloured tops such as spruce

[simso]

I agree, hide glue is superior in many ways, I use it quite often, however I recommend titebond only as its easy to purchase easy to use (straight out of the container), and easy to work with for the novice and experienced

On some spruce tops, when sanding afterwards titebond can also leave a black line from the glue itself heating and discolouring.

Steve