Boat design 101
With a brief treatise on "rocket science".
You need to be a rocket scientist: to set the clock on the microwave - to retrieve the messages from a cell phone - to open an aspirin bottle - to design, engineer and build virtually every modern product in use today - to understand what the hell Einstein was talking about.
You don't need to be a rocket scientist: to design , engineer and build "a boat that works" - nor to understand the process. Ironically, this designer, despite the enormous gulf in complexity between the "theory of relativity" and "the theory of building a boat that works" feels a great deal of empathy for Einstein. He too, must have often felt overwhelming exasperation and frustration - at the fact that nobody understood what the hell he was talking about.
Designing "a boat that works"
In working on this project over, the last 50 years, this designer has probably spent 5 % of the time learning a bit about boat design - 5 % applying what he has learned - and 90% in futile efforts at explaining the results of his efforts to potential investors. At the risk of elevating this last figure even further, this is one more attempt to explain why our designs "work".
First a few basic facts:
> Long skinny boats require less power, to propel fairly quickly, than short fat boats.
> The longer a boat is, the bigger the waves, which it will be capable of "bridging" .
> "Bridging" waves means it will not have to ride up one side and slam down on the other.
> Wide boat are more stable than narrow boats.
> Catamarans have the potential of being very wide - while maintaining long skinny hulls.
> Our catamarans take full advantage of this potential.
Now a couple of slightly more advanced rules. (known as the law of mechanical similitude)
> Speeds of similar boats (of different size) will vary as the square root of their waterline length.
> Power required to propel similar boats (to these speeds) will vary directly as their weight.
In regard to our designs, the following projections are based on the known performance of our 40 ft. catamaran "Walk on Water" - built some 18 years ago and currently operating in the Bahamas.
This boat is 40 ft. long, weighs 6,000 lbs, with a normal load and, with a total of 20 h.p. does 10 knots. The following is a projection table based on this performance.
waterline length (ft.) gross weight (lbs.) power req. (h.p.) speed (knots)
Walk on water: 40 6,000 20 10
Grand Illusion: 72 30,000 100 13.4
Grand Illusion XL: 150 120,000 400 19.4
Unfortunately, there is one more complication - namely, the above boats are not totally similar. The length / hull beam ratios of the above boats vary as follows: Walk on Water - 20 : 1.
Grand Illusion - 18 : 1. Grand Illusion XL - 30 : 1. (Your average catamaran is 12 : 1)
The difference between Walk on Water and Grand Illusion is small enough to let it slide. We do, however, need to adjust the results of the above table - in the case of Grand Illusion XL. If the length / hull beam ratio were maintained at 20: 1 The hull beam would be 7.5 ft. The actual hull beam is 5 ft. What this means is that there is 1/3 less hull to propel through the water)
These hulls will therefore, presumably, require 1/3 less horsepower to propel. The variables that go into this result are actually a bit more complicated than this, but this figure should work out to be fairly close to reality. In effect then, Grand Illusion XL, rather than requiring 400 h.p to do 19.4 knots will require 264 hp. Rounding both figures up gives us the following, very conservative, result: Grand Illusion XL - 300 h.p. - 20 knots
For those who may be wondering why we employed a length / hull beam ratio for
Grand Illusion XL which is so much higher than the former two boats (and even more so than your average catamaran) the full answer is quite long and involved: The short answer, however, is - "Because we can". For those interested in more info. on this question, there is a link at the bottom of this page.
The weights of Grand Illusion and Grand Illusion XL are based on conservative estimates - and input data, based on Walk on Water's performance, is accurate. Consequently, these projections can also be expected to be conservative. At this time, we are still searching for reliable performance data for various mega auxillary sailing catamarans - which, we consider to be "on the cutting edge of yacht design".
However, we believe that few, if any of them, are capable of 20 knots, under power alone - with double, or even triple, the horsepower. Naturally, the comparison to planing power catamarans or monohulls, of equivalent size, is totally ridiculous - with most of these boats requiring more than 6 times the horsepower - to attain an equivalent speed.
We plan on installing (2) 350 hp engines in Grand Illusion XL - giving us an extra 100 hp. in reserve - to ensure we meet our projected speeds. Using a rough rule of thumb, which we have found to be applicable (within certain limitations) to our designs, (a 50% increase in speed requires a 100% increase in power) a top speed, under power alone, (without employing the reserve 100 hp.) of 30 knots is projected. With sail assist, it is expected that speeds of around 35 knots may be achieved on a fairly regular basis.
Of equal, or greater, importance, cruising speeds in the 15 -20 knot range will be extremely economical - and extremely quiet. In regard to sea kindliness or passenger comfort, "Grand Illusion XL" will provide exactly the same type of ride in 7.5 ft. seas that "Walk on Water" provides in 2 ft seas. Anyone who has ever traveled on "Walk on Water" can testify that one is hardly even aware of 2 ft seas.
In depth investing info. under renovation
Boat design 101 - with a brief treatise on rocket science.
 | ||||||
Escape! Runaway! Getaway! - - to a
Faraway Pristine Paradise, where
Light dances with crystal seas - Time flows at a gentle pace -
Space goes on forever and
Grace reaches out to all.
Stretch your horizons!
We can take you there!
*
Your Perfect Paradise.
Or scroll down to continue viewing this page
Much of the following info is out of date
Magic Carpet Catamarans
