As you keep reiterating Wouter this discussion is NOT on the banning of the use of carbon fibre BUT on the banning of "glued" beams to the hulls! As to that proposition I see no reason to ban or not to ban their being glued, I am completely ambivilent to the proposition! I can live with either way for as I have said, I feel that anyone who has their beams glued to their hulls is just wasting their money, BUT as to the banning of carbon fibre beams themselves, I am strongly against the banning of any type of material that is readily available and used commonly already in marine construction, especially when it seems quite obvious to me at least, that this will be the standard in a very few years and not the exception. Why ban it if, as you have been obtusely pointing out there isn't any great advantage between aluminum and carbon fibre when it comes to beams? other than price. If price is the only consideration, then I have to say that I think it is a narrow view of the future of boat construction. It was only a few years ago that no one having a boat built would even consider carbon fibre simply because of the "totally out of reach" cost of the material. As we all know that is not the case now, and it should only get better. Why should it be any different with beams??? Who doesn't feel that the price of carbon fibre beams will not follow the same trend and come well within the price range of the average sailor in the forseeable future? If this only had a remote chance of fruition, it would seem to me to be a very valid argument NOT to ban carbon fibre beams!
P.S. Why not, for the same reasons that you want carbon fibre beams banned, ban titanium alloys from beams? Just because no one uses them doesn't change the fact that they would be much more advantagous than either aluminum or carbon fibre