The following material is quoted from "Blue Ocean" an incredible 
42' aluminum boat for sale at the link.


This information is so well written that I got permission from the owner to post it here.


Unique to Blue Ocean, for Comparison

Hull 

Double grade aluminum construction verses single grade. The use of two grades of 
aluminum in construction of your vessel means this boat is better suited for off shore 
cruising, both in its long term resistance to the saltwater environment and its ability to 
withstand substantial impact without puncture. For years most professionally built 
aluminum race boats and home made cruisers were constructed of a single grade of 
aluminum, 6061. While this material is superior in every way (except cost) to all other 
boat building materials, it is only half as good as a boat build of with two types of 
aluminum. With race boat builders, weight and cost took precedence over safety and 
longevity, hence the early reputation of Aluminum boats.  The designer and builder of 
BO were keenly aware that they were building a family cruiser, so no expense was 
spared. They constructed the frame of 6061, because of it superior strength and rigidity. 
They used 5086 aluminum for the skin (hull) because of it excellent stretch (verses 
breaking) capacity and it impervious nature to the marine environment.
Superior Angle bar ribs verses flat bar construction. While flat bar is cheaper both in 
material and ease of construction, Angle bar ribs provides approximately twice the 
impact strength and its use cuts way down on hull flexing (wear) buy increasing hull 
rigidity. 
High verses low number of lateral and horizontal hull supports, BO has 
approximately 24 cross members for every square yard of hull area (12 inch on Centers). 
Most aluminum boats are built with 18-24-inch from cross member to cross member.  
Not only is BO strong and safe as a result, but it is also much more resistant to denting, as 
hull pressures from minor collisions, raft-ups or sitting dock side, are distributed across 
several cross members simultaneously. 
Round chine verses hard chine hulls round chine vessels are not only faster, they are 
safer as well.
They experience a gradually increasing in righting tendency as heal increases through 
their normal healing range. Hard chine boats experience an abrupt roll-off in righting 
tendency half way through their healing range. Usually not a problem if an experience 
and attentive captain is at the helm when a gust hits but why risk it. . 
Modern underwater confirmation, Exhibits Exceptional speed and handling 
characteristics for a cruising sailboat. Keg supported rudder and V-strut supported 
propeller shaft. Highly recommended for cruising because the potential for running 
aground or snagging things in unknown waters is high and access to quality, cost 
effective repair is not always good.  
Centrally draining bilge system, Allows any rain or AC water to drain and collect at 
only one small central location above the keel. Confining water to a single area, below 
which there is a double hull, not only keeps the rest of the hull dry, it restrict the area 
where potential corrosions problems can occur to a 12" X 12" box. Many aluminum boats 
allow water to move throughout the hull, while healing, spreading the risk over a much 
wider and possibly inaccessible area of the hull.   NO PENNY JAR NECESSARY!


Standing Rigging

Tapered Mast can be efficiently raked to provide exceptional wind control and 
performance. Also allows for the adjustment of weather helm. Internally rigged double 
spreader mast and boom by metal mast of Connecticut a well respected designers and 
builder of performance masts in the US. Raking Non-tapered mast only minimally 
produces the results above because they bend in the middle rather than in the top third. 
 
Rigging chain places anchored across multiple ribs. Allows mast wind loading 
pressure to be distributed across a larger cross-section of hull area. Others attempt to save 
time and money by anchoring the plate to a single rib, or directly to the deck or hull. This 
will eventually cause stress cracks to develop and even chain plate failure, risking your 
mast or even injury to you or your crew. 

Deck

Custom radar, antenna and outboard motor hoist, Custom built and much stronger 
that any commercially available for sailboats, idea for off short cruising. 
Goitt deck hardware and Hatches throughout, Marinium hardware, strongest on the 
market and impervious to the marine environment
Aluminum hard dodger with opening ports.  Custom designed by current owner for 
safe and comfortable sailing if caught in inclement weather yet opens to let air circulated 
on those hot island afternoons. Designed to allow for internal lighting system. Owner has 
light bars to illuminate the cockpit for chart reading or dockside entertaining. 


Best performance and Safety of any cruising yacht of its size. Not only my opinion, 
but also that of all the experienced people whom have sailed her.  
Most boats produced designed and constructed first and foremost, to make a profit (or to 
win a race). Compromises are always made in order to meet the established benchmark 
weather it be cost, weight or whatever. These choices often come at the sacrifice of items 
serious cruisers desire.  Each of the items above on their own, adds substantially to the 
overall cost of construction, but the first owner didn't care. He and any owner will get 
back the extra  investment, in reduced maintenance costs and utility. The value of safety 
is harder to determine. The average saving for one additional year of life, in purely 
monetary terms, was just established by a leading university, at 150k per year of life.