Laser spars

Laser top sections are difficult to find so I cant help you there. Worth keeping your broken one though as you can turn it into a boom.

A sailing school I worked at, we manufactured our own spare mast sections for topper pico and laser, go to yellow pages find your local metal tubing supplier, either measure up your broken bits or take them a section and get them to cut you a length, it's only round aluminium tubing after all, you can then buy replacment collars and end plugs from laser and rivet them on yourself, one laser mast section fraction of the price.  Again you may have trouble if your boat gets inspected or measured, it just depends what you're using it for.

The sleave it and end for end it approach does work for repair, but there are a few 'wrinkles' you need to know.

Its best to get it welded if you know anyone who can weld aluminium for beer money.   Agree that you will bring it in ready to weld and will do all the cleanup on the joint afterwards (thats the slow bit of the job and you really dont want to get stuck with paying their hourly rate)

To prepare it for this,  you need to remove all the plugs and fittings then get the edges of the break back into shape.  easiest to do with a firmly supported length of scaffold pole and a big hammer.  Then to make it simple to weld you need to bevel both edges to 45 deg with a file so there is a V groove after its reassembled ready to weld.  Then you need to sand off the anodising for a few mm back from the edge,  and prepare the sleeve to fit inside.  The sleeve can be made from aluminium sheet of the same gauge as the mast.  Cut a suitable piece not less than 4x diameter by 200 mm (more if the break was not nearly streight).  Anneal it to dead soft by 'chalking' it with a bar of soap then heating on a gas stove till the mark turns brown.  You may air cool it or quench it as suits you. If you quench unevenly it may warp a bit.  The aluminium sheet will recover most of its hardness over the next few weeks as it ages.  Bend the sheet round the mast as a former by hand.  Mark the overlap and trim to length OFF BOTH ENDS, shorter by twice the thickness.  It should now be possible to just get it to fit into the mast.  It may need a little more trimming and the use of a fine file in the gap before it does so evenly.  Clean it with cellulose thinners and Insert it into the mast with the gap at the front (so it will be under tension, not compression) , fit the broken off part of the mast and  make sure its dead streight (strap both parts to a length of angle iron so they sit in the V and drill and pop rivit one side of the joint. (3 small rivits are plenty)  Now sand the inside of the end of the broken off part so the welder has clean metal fore his ground clamp, wash off both parts of the joint  with thinners and take it all to your welder.  Also take some scrap from the aluminium sheet as the welder will probably want to run a test bead while adjusting their machine.  Dont forget the angle iron to keep it streight.

The reason you only rivit one side is so the welder can adjust the gap a little if they arent happy with it. When its to their liking, pop rivit the other side and go and fetch coffee & donuts while its being welded :-)

For cleanup, if it was MIGged, expect a fairly rough bead proud of the mast with some splatter near it and blackened flux residuse.  If it was TIGged, the bead should be a lot nicer and may even be usable as is.   Scrape off as mutch splatter as possible then flatten the bead with an angle grinder  leaving it a milimetre or two proud of the mast.  Finish it with  a dremel but dont try to get it flush, you just want it smooth enough it wont snag the sail.  Finally give the join a coat of clear laqqer to protect against corrosion, and refit all the fittings. so the break is at the top *NOT* the middle.

  If you cant be bothered to order the tapered pop rivit for the coller, use a  countersunk stainless machine screw with a locknut on the inside.  (long batten with a ring spanner taped to the end and a little bluetack to hold the nut in)

It isnt class legal and it wont stand scrutineering but unless your club is a really pissy bunch (or a really keen laser club) It will be fine for club racing and general sailing.