Broke a carbon boom the other day. Broke the boom head moulding and the tail moulding. The arms and tail tubes are still intact. Two options for repair come to mind.
1/ Purchase new carbon boom head and tail moulding and epoxy the boom back together.(Subject to price and availability of parts). This will require "unglueing" the existing components. Can this be done and how...presumably my favourite solution the application of heat but how much.
2/ Ream the boom arms to fit an aluminium boom head fitting and epoxy this on. I have a spare boomhead of the same brand so the angles should be the same. How well will this work? this will be a significantly cheaper exercise. Would then either carbon bandage the tail piece together or do a similar fabrication using an alumium tailpiece spliced to the carbon tubes.

(1) don't use heat!!! Epoxy substantially softens at about 100 deg and fails at 120deg... by the time you loosen the glue, the resin in the tubes you want to keep will also have weakened.
Fiberspar sell a new head and instructions come with it, try their website or email them?

(2) electrolysis? doubt it.... carbon is carbon fibres in a resin which is not conductive (the resin I mean, as it is a insulator) so carbon - alum is fine (in fact there are many hybrid booms out there)
However gluing carbon to aluminium is difficult. Epoxy doesn't like to stick to alum... it needs to be severely roughed up and cleaned at a minimum and that si still not good. The only way is to etch with a nasty recipe of sulphuric acid and Potassium Dichromate and something else. Check the araldite (ciba geigy) data sheets. Too much trouble.

I'd say diegrinder removal with great care, and gluing a new carbon head on.

For the tailpiece you can get carbon braided "sock" to slide over it and pulling the ends reduces the diameter..... two bits of that over a couple of layers of glass woudl do it... but it is messy, needs a practice run first, and will cost $80 materials

Just adding a bit to this topic, re carbon booms.
For those who have the "twist lock system" and they have the problem of slipping under load, the fix cost 30-40c and takes about 60 seconds to fix.
Pull the tail end out of the boom, get two rubber O rings slightly smaller then the serrations in the tail end, role the O rings on to the size slot you need for any specific extension length, and fit it back together.
Have been using mine like this for last 6 months, on 6.6 7.4 and 8.2 sails, and no failures.
Just fixed one for Reg at WSP last weekend.

I agrees with Mark - dont heat the arms to remove - the arms are most likely carbon + epoxy, epoxy is a thermoset plastic - heat it will seriously shag its mechanical properties!.

I have seen many instances of electrolysis between carbon and other metals (particularly stainless) - once helped build a 30ft canting keel yacht that had "issues" between a pre-preg carbon fin (keel) and its stainless mounts, I have also seen heaps of problems with stainless inserts in carbon yacht masts. All these cases have been from exposed carbon in contact with the metal, I think if there is an insulator (ie epoxy (glue) or fibreglass) then it should be ok.

I have a Neil pryde boom that has a carbon/aluminium tailpeice, havent broken it yet!

Frant it must of been a pretty big wipeout to break both ends!

I read some where on a making a carbon bicycle web page that Aluminium has to be coated with something before putting epoxy and carbon on it because there is some sort of reaction. Sorry can't remember the specifics.

I've replaced a few of them, getting the old front section off is very time consuming. If we've got the same brand, NP, twist lock style, about 6 or 7 yrs old, then the front end was a weak point. After 2 replacements, the shop recommended I wrap another layer of carbon fibre around the molding to strengthen it. This requires grinding back the inner knobs that hold the clamp central and sanding out the clamp rubber bush. A big job but it's lasted 4 yrs now.

It was such a job that when my smaller boom broke in a shore break I couldn't be bothered reinforcing the new end and it's also been OK for a few yrs now. Maybe it's only on longer booms where the front fails under normal use.

Since reading about the O rings for the twist lock on this forum, I've also had no problems or repairs at that end. What a great idea, who came up with that?

Just say no to aluminim and carbon together.
the alloy will last about 6 months if you are lucky. best option is to use an angle grinder with sanding disks and grind off the old fittings and then glue to tubes into the new fitting. wear a mask and cover up, carbon dust is not pleasant

Paul Kelf said...

If you are spending big money on a carbon boom & can't get spares you should look for a brand that does give after sales support & a shop that carries spares.

Paul

Not too many shops stock these items and its a year 2000 model. Not enough movement off the shelf for small bits like these.

I have 2 fiberspar tail pieces. one is 38 and the other 48 i think.Both off wave booms.Make me an offer if you wan't one. Both of them have been beefed up with glass and epoxy resin to make them stronger. When the plastic outhaul starts to move, it wears through the carbon quickly if you don't beef it up and stop it moving.
I have replaced the front end a few years back and yes it is a dog of a job cutting the carbon head off and not going to deep so you don't hit the arms. It was expensive at over $200 for the carbon front end and plastic clamp.
Its hard to let go of an old boom, you can say to guy's down the track,"I've had this boom for 10 years, I've only had to replace the arms,head and tail 3 times".