G'day Frothie here, I have busted my carbon boom on the bend at the front and wish to repair it as funds are low and a wind event is on the way so if anyone can suggest a "How To Fix Your Boom Before Next Weekend" sites or youtube thing that would be great.
You can, but I reckon to be safe it would need to be sleeved with carbon and wrapped with same
not an easy job
If you have done some board repair etc before, making a curved sleeve about 3/4" to fit inside, gluing it in, then wrapping the outside would be doable
I would not want to take it offshore alone though 
I've done a couple now, was very wary of going to far off shore at first, but they've both had some pretty rough treatment and are still whole.
I didn't make a carbon internal sleeve, just shaped some foam and glassed it to fit neatly inside. This was to hold the boom together while I worked on it. Glued that in with some bog, then taper ground the carbon back from the break for about 150mm each side of the break. With no gap between them stick 350mm lengths of carbon strands on to several pieces of masking tape the length of the boom's circumference. Stick the tape on the unground part of the boom adjacent to the break. A small paint brush or small roller is the best way to apply the resin on to the boom. Wind the carbon strands as tight as you can around the boom so you get about 1 turn over the 300m length, alternate the direction of rotation with each layer, after you have about 5 layers, wrap a continuous strand around the length of the break. Do all this again and you should have about a 3mm thick layer. To finish off wind a strip of plastic between 50 and 100mm wide around the repair as tight as you can, taping it securely. Actually you can wind masking tape over the top of the plastic, again as tight as you can. This will squeeze out any excess resin and give you a fairly flat finish. You'll have lumps at each end and these can be thinned out a bit but don't overdo it. It won't look pretty and it may feel strange if you grab it in a gybe, but it should work. I put a layer of bog over mine so I could smooth it out with out sanding too much carbon away.
If you want to use it soon after fixing, it would be a good idea to wrap it in black plastic and leave in the sun for a day, make sure each side gets equal exposure.
I have used aluminium then wrapped carbon around it until correct diameter achieved then use this to sleeve
Taper the joint building it up with carbon
By the way I have a boom for you Greg gave me he has sold you ring me if you want to come and pick it up
Select to expand quotebyronmc said..
I have used aluminium then wrapped carbon around it until correct diameter achieved then use this to sleeve
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Be very careful mixing carbon and ali, they can have a strong electrolytic action. That's the reason for one of my boom repairs. It was an alli head fitted into carbon arms. The ali just rotted away and the carbon didn't look too good either. I shaped some foam for the front curve to hold the two arms together then used the above technique to join the arms together with carbon, then fitted a maui saild boom head.
One thing joining bits together, it helps if the whole boom is assembled at the size you use most when you do it. This ensures everything works as it should.
^^^ plus epoxy does not glue aluminiums very well at all without special prep.
So it needs to be a mechanical lock ideally, lots of roughing and a taper if possible.
I once glued three 90's carbon bikes back into one. Still works.
My points would be to perhaps use a balsa plug to hold the boom in place, or a carbon wrapped balsa plug, dripping in resin stuffed inside to hold it?
De- grease with IPA before sanding, then, taper & roughen the area well, de-grease with IPA.
Use at least a West epoxy [carbon doesn't stick to polyester resin]
You can buy stronger epoxy from a company like FGI, [ Fiberglass Industries, or call your local kayak canoe shop may point you to a local supplier].
I used a double bond vinyl ester resin! West epoxy is only single bond, like Araldite etc.
You can but these in various strengths and flex, so an epoxy with some give may be a little weaker, but wont fail with constant flex. [That's why I used it in the bike for seat, wheel & head tube.]
I used about a 1" tape, just wrapped it tight around with plenty of resin. Its not going to matter much if when sanding back after you sand the carbon, the strength is from the resin. The point in another post about wrapping it with glad wrap can save some sanding time, but the wrap will stick...
When you think about it. the boom is pretty thin, as long as you get a good bond & use the correct resins it should be very strong.
I personally would go for overkill and wrap a pretty thick layer, sand back as required.
You will need to clear coat or paint it with a UV resistant paint as most resins or carbon aren't UV resistant.
If you use a kevlar/carbon tape, you cant sand the kevlar, it goes all fluffy...
