[PUP] PPM, Convergence, narrow boats, etc.

[Ron Rogers]

I should have been more clear. My 1985 Naiad 252 active stabilizers turned
my Willard 40 into a submarine when punching into head seas. In this regard
they are dumb and we were taking dollops of green water as high as the
flybridge. At the suggestion of my friend (a pilot among other things) we
locked them in centered position and reduced the boarding water to the
occasional spray. I *assume* that new Naiads and their competitors now know
enough not to act as submarine dive planes and lock themselves up
automagically - rate sensors are cheap now.

For us slow boaters, the fin area must be proportionately larger than
normally recommended to compensate for the weaker forces generated by
passing through the medium more slowly. As I understand it, new stabilizer
systems allow you to adjust for sensitivity and corresponding frequency of
compensation. I have always wondered if the NAR stabilizer failures were due
to the owners running them at too high a setting for an extended voyage. Of
course, this would require that the manufacturers admit that their products
(in those sizes) are not made for high settings in continuous duty. It is my
vague recollection that the components that failed were mostly sensors and
not the actual hydraulic systems.

Ron Rogers

-----Original Message-----
From: John Marshall

The newer active fins (I've got the latest Trac 250's, and they are on  
the oversized side) can handle wave action from any angle, but of  
course they can't reduce pitching as they are mounted on the pitch  
centerline. But rolls greater than 10 degrees in most any kind of sea  
are a rarity.