Ah, FFF...I was waiting for a question like yours. The answer is : nothing.
RCMB was a smaller, independent forum...we had no sponsors as such, and therefore we were not beholding to anyone. Being smaller, a lot of the membership felt happier in the knowledge that their modelling skills weren't going to be open to a lot of criticisms, and we encouraged them to post their builds, warts and all.
One of the members has had a stroke, and he felt 'at home' on a smaller forum. A lot of the guys aren't exactly computer literate either, so they needed a lot of help with posting anything. A forum the size of Mayhem can be daunting to a person who has only just learned how to turn a computer on, so RCMB was an easier alternative for them.
Another reason RCMB was set up is that a lot of the members had got fed up with over keen moderation (and I do NOT aim that comment at this forum, despite what you may think) on other forums. RCMB was famed in it's short lifetime for self moderation...I think I only had to wave my famous Red Pencil a couple of times.
RCMB and Mayhem ran side by side quite happily, with many members here being members of RCMB and vice versa. Information was shared between forums, and people learned from each other.
RR...your offer of assisting with another forum is greatly appreciated, I may set up another general forum in the future, but at present I have more than enough on my plate with the running of the website and the forum for the AMS (Association of Model Submariners), plus I've now taken on the role of Secretary as well, so I have more than enough to do. But I'm sure that if you'd like to go ahead with setting up another forum to replace RCMB, a lot of the guys would be forming a queue to join up.
Once again, I offer my apologies to all of the membership of RCMB for it's demise, and I'd like to say thanks to all those people who have sent me emails and telephoned me offering help and assistance. I appreciate every word...
Rich