What are the design considerations when building a Carbon Boom?

Keep it light and don't let it break.

If using Super spar ends make sure diameter matches. Jacko's doesn't use inserts, he bonds the gooseneck 
eye on. Best bet is to measure up someones and make copy. 2.5-3kg I think is a good weight. Worth having extra wrap at the front as takes most load. Mine cracked there last year, so Linton beefed it up.

Considerations, What are you going to use for a die/mould
   Lay up a few test pieces to check finished thicknesses and your lay up process compare it with pro suplied. Buy enough for two & make the first on the stronger side, easier to make a lighter one later than be discouraged by a broken first attempt. A clean workshop with plenty of time, don't underestimate how long it can take. It's taken me about 9 months! (mast & boom)from starting to fiting mainly due work & life!!!!!
Good fun though,

Thanks Barry,

Could you give me an idea of where to get materals and perhaps some photos of your die/mould please?

Also, did you use any kind of oven or vacuum bagging?

Jon

I understand that the mast is a more complex vari-section structure, but isn't carbon tube available? even if this isn't strong enough, it could be used as a basis for laying up, and bag a layer on the outside.

Boom: We used a rectangle metal box section as a mandrile, then altered into a triangular profile. probably the most time consuming idea weve ever had,
If we did it again we'd rethink it.
Mast: based on comercial 90-100% carbon windsurfer section tubing, beefed up at usual ares of concern with 200gram carbon wet lay up, peel ply wraped (tightly bound) into place (3-4 layers,tapered ) luff track nylon sikaflexed on, we may run 40-50mm wide down the side of this if mast considered to soft.
Most of this info found on webb type in 'Carbon Masts'
Sources: Mainly SP systems & GBR base in Cowes, vacumm used on boom, mast built in back garden!
I'll post some shots asap, regards Barry.

Can you build it cheaper and better than whats on the market already.

JON 
If your going to lay up carbon ,vacuum it.if you dont it will be heavy and break . oven ,poly tent with a fan heater. Fabrics Carr Reinforcements UD and  plain weave keep it simple ,Resins West. Happy bogging.

Jon, 
Carbon suppliers www.cfsnet.co.uk Vaccuum kits, www.bagpress.com.  You can get away without vacuuming on low stressed components, but as someone's already said, on spars it's a must have. See the Cherub website for some good tutorials on what to do/not to do.

I see that a poly tent makes an "Oven"  I take it that "Oven" means a warm environment rather than a very hot one.  Is 30 - 40 degrees C warm enough?

Temp: Check out your prefered resin supplier info sheets/spec, Whilst mine was down in the back 'garden' I created mini ovens by taping an area of black bag over the area being reinforced (a localised oven), you'd be supprised how warm it got with direct sunlight on it, This is a very old trick used by many a boat repairer working in the open.
I made up gooseneck/spreader/prodder bracket/masthead sheave by fabricating with 2mm flat carbon(vacumm baged on heated glass table-GBR) cutting each piece to shape filleting in place then applying 2/3 more layers over the over them, again I'll take some photos next week.
I'll leave it till then as the pics will show it pretty well, more than my words anyway!  To finish I SP320 flow coated it then used a UV varnish to finish , performance we'll see. Barry.