Boom repair... Patch or what?

I had a similar problem with a catamaran cross member. I got my local stainless man to roll a sheet of 2 mm stainless to cover the holes and get it polished. Riveted over the top with lavish application of Duralac it was amply strong.
 
It can be repaired. Welding repair will be difficult and unreliable. The best way is to sleeve it using rivets; there are riggers and others out there who do this type of jobs. It will cost almost half the price of a new boom.
Why do you think welding will be 'unreliable' please?
 
No doubt it could be welded.
But it's not a trivial job as it's the most highly stressed part of the boom.
It might be possible to sleeve it internally.
I've done this with round sections, just use a tube which isa tight fit.
Years ago I did a 505 spinnaker pole, I used a piece of same-size tube with just enough cut out of it (10 degree slice or something)
so thet it could be knocked into the broken section with just a single rivet to hold it in the right place. It even looked quite neat.
 
Lot of doom merchants !!

I like the T section idea .. not only does it strengthen the area - but also gives you a new fixing point better than the key slot. Only drawback of course is its not so nice for roller reefed main as the T section will be against any rolled sail.

The other way of course is to get similar stainless kicker plate but larger .... clean up area - taking care not to remove surface anodized outside of new fitting - resin up - rivet new fitting in place.
 
I replaced my boom with a section of broken carbon fibre mast much lighter however you have to find a broken cf mast.
Repair of the existing boom is obviously easiest.
Epoxy and fibre repair across cracks are very common on aircraft aluminium wings etc that are stressed. They use various fibres like boron for strength. They use epoxy for resin. The sectret is to get the ali surface really clean with a final wipe over with clean acetone on a clean rag. I would suggest you use kevlar for the fibre being easily obtainable and not expensive. It also tends to be more flexible when laying on but very tough. Carbon fibre could be used but may give galvanic corrosion problems. I would just wrap the kevlar (or glass if you wish) around the boom in a non continuous way from the track back to the track. Or as said you could just glass right around with many wraps then cut the slot for the bolt rope. (depends if track is rivetted onto a round section or if boom is extruded with track integral and internal. Whatever you do it will always look like a repair. ol'will
 
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