James,
Yes, it is largely men but there are noticeable exceptions "Umi R...." from the States is an exceptional modeller, she is also a professional and her technical competence has helped me and others, frequently. We also have a very young, active female. There are several others and quite a few female partners, so always try to be inclusive when you refer to Mayhem Members.
And, yes, the average age is "older" (I am 65). There is a discernable pattern for some of a model making background up to the age when a family starts to develop. Then family and career demands take over but a later return to the hobby when the family has grown, work demands diminish and money becomes less of a problem.
However, the age thing is relative and many of our more mature members can behave like kids when it suits them!
On owning a 1:1 boat...quite a few Members do. Some own river craft (including narrow boats and barges), others have sea going vessels. Others aspire to owning a full size craft and build their own. Many have never been to sea and some would never wish to. We are a very catholic group.
Enjoy our hobby and enjoy all your friends on Mayhem.
Roger in France.