Any chance you could post a pic of the break? What looks like dry uni's are probably actually ok, just due to the break they normally break up and look pretty horrendous.
You mention a glass tube? Is this just that the internal skin is slightly brown/mustard colour compared to the outside one? I remember this from when I extended mine over christmas.
Doing the repair is quite an easy task, the key as with everything is the prep. The more time and care you spend doing the prep, the better the appearance of the final result.
The method I have used to great success recently is as follows:
Step 1: Get a piece of glass weave with the dimensions of about 40cmx30cm, and wet out a single layer and let it go off. Cut it into a neat square and sand up both sides.
Step 2: Neaten up both of the broken ends of the mast to remove any dodgy straggly bits of mast and with an angle grinder/orbital sander rough up both of the outside walls of the mast, don't be shy here, go to town on it and remove some layers of carbon.
Step 3: Using the rectangle of glass which you have already laminated as a core, you will bond this inside the 2 lengths of mast to make it one piece again. I've found the best method for this is to paste a layer of bog (epoxy mixed with a blend of fillers) inside the ends of the tube all over the inside wall. Try and cover the wall as far up as your glass 'tube' will reach. Align the 2 bits of mast and tightly roll up the piece of glass to form a tube.
Carefully insert this into the mast and then when you let go, it will spring open and neatly stick itself to the inside wall of the mast. You can wiggle it round a bit to ensure that the mast is straight, and also that the overall length of the mast is the length which you require. (don't be worried if you can see the glass tube still, you will rebuild the gaps with carbon later). The main thing here is that you have the mast straight and the track aligned as best as you can. I normally clamp some long straight planks to the mast in order to keep it straight at this stage, and if possible you can wedge something in the track to make sure that both the top and bottom are aligned nicely so the sail will still feed. Leave this to go off properly.
Step 4: At this stage, your mast should be straight and one piece. The bond is strong enough to move it about as long as you are careful not to bash it on anything. The next step is to further neaten up the break. The aim here is to remove the carbon in a tapered fashion. At the centre of the break you will be down to the glass, and then taper it out so that you have undamaged outer wall about 30cm either side of the break. This allows you to rebuild the unis in tapered layers so you don't end up with a ridiculously overbuilt lump either side of the break. The neater the taper, and the more time you spend doing this bit, the better the end result will be.
Step 5: Cut your uni directional carbon. I would guess that you will probably need 4 layers of 300g carbon unis on this break in total, plus a finishing layer of weave to add some hoop fibres.
Layer 1: 300g UD Carbon 15cm long (7.5cm either side of the break)
Layer 2: 300g UD Carbon 30cm long (15cm either side of break)
Layer 3: 300g UD Carbon 45cm long (22.5cm either side of break)
Layer 4: 300g UD Carbon 60cm long (30cm either side of break)
Layer 5: 200g Weave Carbon 70cm long (35cm either side of break)
From experience, it can be a good idea to mark out on the tube the outer edges of the carbon for each layer to aid you getting it central to the break. Once you have the first layer down it can start being quite difficult to see where the middle is. Also, when you cut your layers, it is advisable to not cut them square, but to taper the ends so that the end of each layer of reinforcement isn't square to the tube.
Depending on how neat your first 4 layers of UD are, you can either go straight ahead and put the weave on in one hit, or leave the weave off and consolidate as per step 6, and then back and put the weave on last as a vanity layer once you have sanded it back and tidied it up a bit if it is looking messy.
Step 6: This layup needs to be consolidated. Depending on what you have got to hand, heat shrink tape gives the neatest and easiest finish but you need to be a bit careful not to crush the glass tube inside. Previously, I have always just wrapped it up in peel ply pulling it as tight as reasonably possible and then wrapping the whole thing in brown parcel tape. Parcel tape does shrink a small percentage using a hair dryer so attack it with your mum/wifes/girlfriends when they are not looking. Then leave it for a good 24 hours to go off. Might be a wise idea to re-clamp your straight edges to it to make sure it comes out looking more like a mast than a banana too.
Step 7: Remove the peel ply / tape and check your handy skills. At this point, your mast should be basically fixed. Some sanding and neatening up might be required depending on how vain you are feeling. If you have any voids you can sand and fill them, and add an additional layer of weave on top of this if you are going to clear coat it all. (of if you didn't put the weave on in the first hit, tidy it up and add it now).
Step 8: If you have laminated around the mast track you will need to cut a new slot in it using a hacksaw, and then get a piece of sandpaper inside to smooth it all back so that your sail doesn't get damaged next time you use it.
Step 9: Go out sailing again! Woo!
(I have written this from memory, but have repaired one CST mast using this method, and also extended the RS600 mast on 2648 in order to replace the stump. Both laminations have been done outside in a garden and are all still in one piece, so it is a tried and tested method :-) If anyone else can spot any glaring errors then please shout as I might have missed something silly)
