following is a guide and pertains to the services of J. Simpson
Ltd. The policy of other design firms or Naval Architects
Vessel Rig and Sail Plan
Consultation (Owner's Representative)
is a brief description of some of the most frequent types
of consultation we provide to the marine industry. The contents
of the subjects addressed should be considered as ‘non-inclusive’
in that each vessel must be reviewed on its own merit. Limiting
work to rigid formulae might not be in the best interests
of the client or the vessel.
Although we will work on designs other than our own, we strongly
recommend that questions and services should be addressed
by the original designer of your boat. If for some reason
this is not possible, we would be pleased to assist. Out of
courtesy, we may request authorization from the designer unless
there is a compelling reason not to do so.
You want to
know if your boat can go faster or how fast it might go with
a new engine.
We have standard forms available and with complete information
we can predict the speed of your vessel. Accuracy is often
within 10% and sometimes 5%.
The most common reason for this calculation is to verify the
existing installation. Example: a review of a 42’ planing
hull determined that the incorrect reduction gear was fitted
and no reasonable adjustment of the propeller would make the
boat go faster.
You may or may
not have the correct propeller. This is related to the speed
estimate but often the problem can be insufficient diameter
(& resulting low blade area) or a poor installation.
If you are going
offshore or cruising in higher risk conditions a thorough
review of the stability can be valuable and reassuring. In
addition to the initial, stability we also look at the range
plus other matters that might limit or compromise stability.
For standards we use several criteria with one being the I.M.O.
(International Maritime Organization). Calculations are done
for still water only since trying to predict what waves a
vessel may encounter is highly speculative and almost impossible.
Self-righting: A well designed, built, and maintained sailing
vessel will invariably self right after a capsize. For powerboats,
the configuration of the hull and superstructure is different
and self- righting and intact recovery may not be possible.
Vessels claiming to be self-righting (positive stability through
a 180 degree roll-over) will require special attention to
the structure, outfit, and interior storage. Arranged as such,
items like broken windows, backflooded engine exhaust, and
flying interior objects would not be of concern. Unfortunately,
such arrangements can be expensive, very invasive, and may
detract from the habitability of the vessel.
Vessel Rig & Sail Plan
may want to alter the rig (cutter to ketch, etc) or increase
its size (sail area). With correct information we can review
and furnish the appropriate information and drawings.
Owner may need
an alternate or new layout to satisfy special needs or requirements.
Work may be limited to one area (or drawing) or may encompass
the entire boat.
new details to satisfy special needs or requirements. Sometimes
a part or detail shown may not be available or suitable. We
can offer suggestions and guidance.
Estimate (Mass Analysis)
As a part of
the design process, the weight estimate (sometimes called
a Mass Analysis) is a crucial calculation. Unfortunately,
it is also tedious one of the less pleasant chores that a
designer must perform. The boat is floating in a fluid and
therefor affected by weight; each and every item that goes
into building, equipping, and operating the vessel and has
weight (mass) must be accounted for. This includes often over
looked items like paint and in the case of plates on metal
boats, over-rolling. We have had the privilege of reviewing
designs in which it was quite obvious that a weight estimate
was never done or if done, was perfunctionary at best. It
is not a pleasant task to inform a client that his boat will
be 40% to 60% heavier than quoted and float 8” to 12”
lower in the water.
In an existing
vessel, improving the way it handles is sometimes very difficult.
Sometimes the problem can be attributed to the design, sometimes
the way in which the boat is outfitted. A thorough evaluation
of the vessel may offers some clues as to how problems can
be lessened, if not eliminated altogether.
Check (a second opinion)
This is a review
of a design in its entirety and may range from a quick revue
to a detailed assessment. If a fair amount of time is required,
the design check can be a fairly expensive and in the case
of a design from a competent designer, is probably not necessary.
How do you know if a design check is warranted. Even to the
untrained eye, sometimes a small item can stand out. A good
example is a client who questioned if a ¼” plate
deck was needed on his 58’ steel cruiser. Unless he
was expecting heavy deck loads (wheeled traffic, cargo, etc.),
the use of 3/16” plate (or possibly 10 ga) would be
quite sufficient. This small revision saved him some money
and improved the stability by eliminating about 1700 pounds
of topside weight.
Obviously, the “check” is done by someone other
than the designer of the work under review. For this and other
reasons, some designers may not appreciate their work being
scrutinized by others who, in most cases, would be the competition.
While the design check is not commonplace in small private
vessels, it is quite common on government projects involving
public (taxpayer) money. If you suspect a problem (or even
if you don’t) there is nothing wrong with a second opinion
from a qualified person. After all, it’s your money,
your boat, and your life: a good design it will stand up to
to our own designs, we can also provide this service for clients
of other designers. The purpose is to provide some on-site
verification that the builder is following the plans, the
intent of the design, and good shipbuilding practice. In some
cases we might be asked to furnish technical assistance to
the builder on behalf of the designer. In all cases the designer
must approve all work and be kept informed of the vessel’s