[Rhodes22-list] custom parts?

[Roger Pihlaja]

Richard,

When we first purchased Dynamic Equilibrium, the cockpit seats "creaked"
when they were sat or walked upon.  The noise annoyed me & made the
boat sound like it was cheaply made.  It turns out the bulkhead in front of
the lazarette compartment is not a structural support for the cockpit seats.
If you don't believe me; then, check it out & you will find the cockpit
seats are not attached to that bulkhead.  Instead, the cockpit seats are, in
effect, one long unsupported "beam" from the transom to the cabin bulkhead.
This simplistic model is especially valid along the inboard edges of the
cockpit seats, which is where the creaking seemed to be coming from.  Let's
model the seats as a simple beam supported at both ends & point loaded in
the middle as a worst case. The deflection under load, which is what
causes the creaking, is proportional to the unsupported (Length)^3.  To
stiffen the structure, I added two equally spaced support columns on each
side, port & starboard (Total = 4).  These support columns transfer the load
from the cockpit seats to the cabin sole.  This reduces the unsupported
beam (Length) by a factor of (1/3)X & stiffens the seats by a factor of
3^3 = 27X.  Viola, no more creaking!  So, that stainless steel support
column in the picture is one of the four.

Can you tell I've done way too many homework problems in Solid
Mechanics this week?  Aren't you sorry you asked?

Roger Pihlaja
S/V Dynamic Equilibrium

----- Original Message -----
From: "Christine Allison" <sailnut at asan.com>
To: "The Rhodes 22 mail list" <rhodes22-list at rhodes22.org>
Sent: Thursday, September 18, 2003 9:39 AM
Subject: Re: [Rhodes22-list] custom parts?


> What's the purpose of the stainless support inboard of the propane tank?
>
> Richard Smith
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