[PUP] Emergency tiller

[Jim Leishman]

Dear Scott:

I personally have over 15,000 miles on both of the 40s that we have owned and
I can tell you with absolute confidence that the N40 steers beautifully under
all conditions. I have video of the boat running down swell during gale
conditions in the Pacific and then even tougher conditions in the
Mediterranean and it shows the boat tracking straight with little yaw despite
the steep and high seas coming up astern . We all marveled that during our
around the world voyage on N40#21 there was never one time when the boat had
to be hand steered during the many gales and a few storms we encountered.

I understand that you believe the boat is steering badly with the fins
centered and locked and if your observation is correct then I suggest that you
have air in your steering system. Your boat is equipped with Hynautic
equipment and the bleeding process is relatively easy but you must do it
exactly as stated by Hynautic within their operators manual.

The problem is easy to understand if you think of it in simple terms. A
hydraulic steering system free of air provides precise steering with very
little play. A system with air entrapped within is mushy and has lots of play.
When you initially apply rudder the forces against the rudder are at their
greatest. As the boat begins to turn and momentum is developed the force on
the rudder is slightly reduced. If you have air in the system and the rudder
is initially deflected the air within the steering system compresses until the
compression is sufficient to move the rudder. As the force against the rudder
is reduced after the turn is initiated then the compressed air causes the
rudder to move farther with no further input from the helm.

This is particularly true when running in any kind of sea. As the sea rolls
under the boat it tries to turn the boat until the helmsman or autopilot
recognizes what is happening and the rudder is deflected to stop the turn and
bring the boat back on course. The boat is turning and momentum has developed.
The rudder is deflected and the loads against are significantly more that what
is required in a turn from a straight line due to the momentum which has to be
overcome. The helm is turned and the air compresses against the heavily loaded
rudder just to stop the turn in progress. As the turn stops the load is
reduced the air expands, the rudder moves even further. As the turn is now in
process the momentum is established and the load on the rudder is further
decreased. Again the air expands and the rudder moves even farther causing the
boat to turn too far. Finally big counter rudder is applied to stop the
excessive turn and then the process repeats itself over and over.

Before you condemn your boat to the world I suggest you carefully go through
the process of bleeding the steering system and I'm certain that if your boat
is indeed steering badly with fins locked and centered - air is the problem
and you will see a remarkable improvement.

Best Regards,

Jim Leishman

-----Original Message-----
From: passagemaking-under-power-bounces at lists.samurai.com
[mailto:passagemaking-under-power-bounces at lists.samurai.com] On Behalf Of
Scott Bulger
Sent: Saturday, March 15, 2008 4:14 PM
To: Passagemaking Under Power List
Subject: Re: [PUP] Emergency tiller

on the Trac units I run them either Active or Off.  If Off they are
also pinned in place, they do not move.  The boat, with the fins off
and pinned wanders all over the sea like a sailor on shore leave in
the Roja district.

What more can I say?

Scott


On Sat, Mar 15, 2008 at 3:12 PM, Ron Rogers <rcrogers6 at kennett.net> wrote:
> Let me be more clear. On my ancient Naiads there be "Off" and "Centered"
and
> "On." "Centered" on my boat means that the system is on and hydraulic
> pressure is holding the fins rigid - locked. This can also be done with the
> pins provided. Mine can move around when the system is "Off."
>
> I noticed the difference both when heading into 5 and 6 foot seas and when
> docking, My boat handles better when docking (astern) if the Naiads (Model
> 252) are "Centered."
>
> Ron
>
> ----- Original Message -----
> From: "Scott E. Bulger" <scottebulger at gmail.com>
> To: "'Passagemaking Under Power List'"
> <passagemaking-under-power at lists.samurai.com>
> Sent: Saturday, March 15, 2008 4:35 PM
> Subject: Re: [PUP] Emergency tiller
>
>
> | As I said:
> |
> |
> | "it does it with our without the fins active."
> |
> | Wanders like the eyes of a teenage boy at the prom...
> |
> | Scott
> |
> |
> | -----Original Message-----
> | From: passagemaking-under-power-bounces at lists.samurai.com
> | [mailto:passagemaking-under-power-bounces at lists.samurai.com] On Behalf Of
> | Ron Rogers
> | Sent: Saturday, March 15, 2008 1:11 PM
> | To: Passagemaking Under Power List
> | Subject: Re: [PUP] Emergency tiller
> |
> | Before excusing the stabilizer fins, try going straight with the fins
> | "centered." I'll bet she stays on course.
> |
> | Ron Rogers
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