I read it everywhere: If you make a catamaran wider it will pitch pole

Now where is the evidence to back that up? It seems to me that this is something someone wrote once years ago and since then everyone has just blindly repeated the dogma.

Probably they do so because at first sight it sounds logical. If a catamaran is made wider it becomes more stable sideways. Thus proportionately it must become less stable fore and aft, all other factors being equal.

But A) is that true? B) how many (besides me) have tried making a catamaran wider to see what happened?

The original writer was, I suspect, a promoter of early narrow English boats (like Prout and Sailcraft) worried about newer, wider designs. So it is ironic that one of the first pitchpoles was of a very narrow, low freeboard Prout 27 in Germany.

In practice catamarans tend to capsize diagonally, not cartwheel end over end. Indeed if they did go end over end then obviously the hull spacing would be irrelevant.

So it is the diagonal distance from windward stern to lee bow that is important. Clearly then, as a boat is made wider this distance increases and so it becomes more stable overall.

My 24ft Strider design has a 22ft WL and normal hull CL spacing of 10.6ft giving an overall beam of about 14ft (so when it was designed over 25 years ago it was considered wide).

In 1986 I built an experimental Strider with a 14ft CL spacing. Compared to it's WL length that is wide! In fact it looks scarily so on paper, still wide in the boatyard but looks great on the water.

A number of these extra wide versions have been built since then. None have pitchpoled or capsized. Indeed I have always thought that these wider boats sailed better and were more stable than the narrower ones.

I guess if there was any truth in the rumour that wide boats pitchpole then catamarans would gradually be getting narrower. Instead they are getting wider. Even the last generation of Prouts were wider than earlier versions.

So I say it again.

It is a myth to say that just making a catamaran wider means it will pitchpole. There are many more important factors that determine whether a boat will pitchpole or not than just the hull spacing.