Don Jordan the designer of the Series Drogue and I have been in contact by
email and phone. It is apparent from these exchanges that his grasp of the
intricacies of yaw, pitch, straight line stability and other factors are
extensive. He is now 89 and I cannot emphasis enough the importance of the
cruising community coming to as much understanding of his views as
possible. He is a gold mine of information and insight. We have to be
realistic and take note of the fact that his health might deteriorate and
he might be unable to engage in the extent of communication that would be
of so much benefit to those who cruise, in stormy seas.

In that regard, I intend and I suggest that others do the same. To wit, to
study the materials at the Drogue web site. To read all the reports that I
can find and to query him for clarification on issues that I don't fully
understand.
http://www.jordanseriesdrogue.com/

I posted some material about his drogue a while back and I will now attempt
to lay out some of what I gleaned from my recent communications with him.
He makes a strong argument that the drogue, and this may or may not apply
to similar systems, that a bridle is necessary in order that there be
"turning moment" to cause the vessel to come perpendicular to a breaking
wave. That a bridle that will cause this is nearly impossible to rig from
the bow, where there is not the necessary width to do the job. That single
point drags work well on catamarans because the bridle can be rigged to
both hulls at the bow and there will be enough separation to create the
turning moment.

Another point he made is that typical power boat hulls have generally more
directional stability due to a longer continuous keel than the typical
sailboat. This is a significant thing to note if you consider that in the
Fastnet 79' race and the Hobart/Sydney race of 98'(?) where there were so
many boats damaged and lost, that these boats were typically targeted at
racing. They most likely had short keels and small rudders. The logical
conclusion of shorter and shorter keels is a sailboat with NO keel at all.
Which in SOME ways but only very slightly similar is the case with power
boats intended for passagemaking. What these design issues implies is that
underwater hull form is more than just the curves. After all we could make
a sailboat with no keel as well as a power boat, carried to some irrational
extreme.

I think a lot of us have some tiny intuition in the backs of our heads that
the old timer's boats with long straight keels were generally pretty stable
when running off. Big keels add friction and sail boaters have been quick
minimize keel surface area in the quest for speed. The same is most likely
true for power boat designs making allowance for the fact that a modest
difference in surface friction may be less important than straight line
stability, where the motive power is coming from a diesel engine instead of
wind.

I will post more on this later.

Capt. Mike Maurice
Tualatin(Portland), Oregon

Mike:

RE: They most likely had short keels and small rudders. The logical
conclusion of shorter and shorter keels is a sailboat with NO keel at all.

I assume the word shorter is not meant to be short in depth, since racing
sailboats are designed to have maximum weight and arm length for a maximum
righting moment result i.e. very deep keels, but they are generally small in length
along the direction of motion. Obviously, this does not converge to NO keel at all.

John