Posted on behalf of Scott Strickland

I do not claim to be an expert in this subject.

I do NOT state that the drogue is not the correct choice.
Please before your respond to this read it carefully.

But I feel I should off some comments from my
limited research into to the decision process I used and
review of the technology and information.

First a comment from the above report.

1. I worked for Avecor a biomedical company assisting in
   the computation fluid dynamics model of fluids (CFD).

The computer simulations (and included
programs) reflect what at best could be described
as very simple.  The state of the art in 2005 is still
unable to do a great job of modeling turbulent flows
of fluids.

I base this on our multi-million dollar attempts to
model the flow of blood thru the open heart circuit.
We use people with PHD's in CFD to do this on true
super computers and still find the computer models
fall short, his computer simulations are literally
thousands of times (probably millions of time) simpler.

2. The author sells the recommend technology.
   I would be happier if the study was done by
   independent experts.

3. They seem to only study sailboats which
   have different hull construction and windage.

I do not know which solution is better.

What I do know is that most boats, and certainly
this is true for our Nordhavn 47:

they are designed and built to take the
waves from the bow.

The cockpits are not as strong, the stern not as
streamlined, and does not shed water as fast
as the bow, therefore we have selected a bow
deployed sea anchor.  I do not know if that is the
correct answer.

the cockpit becomes 2-3 feet deep in water pretty
quick and working on the bow is impossible, and
quick frankly probably from the cockpit as well.
I could not open the aft door without hundreds
of gallons of water coming in, and I would not
be sure  I could close the door!

I bring this up not to say the drogue is wrong
only that to me at least it is not clearly the
correct solution

Sincerely,

Scott Strickland

You said:
2.  The author sells the recommend technology.
I would be happier if the study was done by
independent experts.

****Actually the Coast Guard seems to have done the study, the retailer
only refers to it on their web site. (I have no interest in this other
than to forward information that may or may not be of use, that is for
you to decide)

You said:
3.  They seem to only study sailboats which
have different hull construction and windage.

*** if you read the report, the CG used a 42' POWER research vessel to
test the system, I couldn't find any thing that says it's only for
sailboats. I think that it leans more towards sail type vessels because
in 1987 when the report was written there weren't that many smaller
power vessels liable to be caught in mid ocean during a storm. Again, I
state that I have never used either system, I'm only passing on info
that might come in handy.
Your right about windage and shape, a square box shape will cause more
drag than a football shaped hull of the same volume and weight, it's up
the user to determine what loads he/she expects. My personal opinion is
that the large parachute drogue in like being anchored in a blow. The
boat is pulling against an in-move-able object and the shock loads are
very high, the multiple small chute system will keep a constant tension
on the line and be easier on the vessel and the occupants. Remember that
there is considerable slippage with either system, both from the wind
and from the current; if I were close to shore I would reconsider using
either.

Again this is my $.02
Tom

-----Original Message-----
From: passagemaking-under-power-bounces@lists.samurai.com
[mailto:passagemaking-under-power-bounces@lists.samurai.com] On Behalf
Of Scott Bulger
Sent: Friday, February 18, 2005 11:15 AM
To: Passagemaking Under Power List
Subject: Re: [PUP] Bungee Cord Jumping with your Boat, Scott Strickland

Posted on behalf of Scott Strickland

I do not claim to be an expert in this subject.

I do NOT state that the drogue is not the correct choice.
Please before your respond to this read it carefully.

But I feel I should off some comments from my
limited research into to the decision process I used and
review of the technology and information.

First a comment from the above report.

1. I worked for Avecor a biomedical company assisting in
   the computation fluid dynamics model of fluids (CFD).

The computer simulations (and included
programs) reflect what at best could be described
as very simple.  The state of the art in 2005 is still
unable to do a great job of modeling turbulent flows
of fluids.

I base this on our multi-million dollar attempts to
model the flow of blood thru the open heart circuit.
We use people with PHD's in CFD to do this on true
super computers and still find the computer models
fall short, his computer simulations are literally
thousands of times (probably millions of time) simpler.

2. The author sells the recommend technology.
   I would be happier if the study was done by
   independent experts.

3. They seem to only study sailboats which
   have different hull construction and windage.

I do not know which solution is better.

What I do know is that most boats, and certainly
this is true for our Nordhavn 47:

they are designed and built to take the
waves from the bow.

The cockpits are not as strong, the stern not as
streamlined, and does not shed water as fast
as the bow, therefore we have selected a bow
deployed sea anchor.  I do not know if that is the
correct answer.

the cockpit becomes 2-3 feet deep in water pretty
quick and working on the bow is impossible, and
quick frankly probably from the cockpit as well.
I could not open the aft door without hundreds
of gallons of water coming in, and I would not
be sure  I could close the door!

I bring this up not to say the drogue is wrong
only that to me at least it is not clearly the
correct solution

Sincerely,

Scott Strickland

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