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How about those rowing shells!
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Grand Illusion XL - XW (extra wide - with central hull.)
It should be noted that that we have not labeled the above vessel a "Trimaran" It is indeed quite different from the normal trimaran configuration - which consists of one large, central (load supporting) hull and two smaller (stabilizing) outer hulls. The above boat is still very much a "Catamaran" and certainly so - in regard to the original meaning of the word - "tied logs".
The remarkable results of the projections regarding (3) 8 man rowing shells (on the web page Liar! Liar!, coupled with the long held wish to extend the overall beam of Grand Illusion XL to 45 ft., provided the impetus for this diversion. This is not only a diversion in terms of design, but also a diversion - from my "life's work and full time job" ( trying to explain my designs to uninterested potential investors) - to my "hobby" of creating these designs.
However , over the last year I have been working very hard and very long hours at my job. Hopefully then, my boss won't get too pissed off - if I take a few minutes off and check out this design avenue. Actually, I have played with this concept on many occasions and, in fact, have built a 40 footer employing this configuration.
In that case, however, the central hull was an afterthought - squeezed into the space provided by a rather narrow catamaran - with fat semi displacement hulls. It will not, consequently, provide much useful information in regard to Grand Illusion XL. On the other hand, the projections, regarding the (3) 8 man rowing shells, have provided a whole lot of useful information.
Utilizing this information (and all other information we can get our hands on) we project that the above version of Grand Illusion XL will differ from the version shown on the other pages of this web site as follows:
Pros
> Will provide for more space generally.
> Will provide greater load carrying ability.
> Will be even safer - in regard to all possible threats to safety.
> Will virtually eliminate any chance of pounding and damage to the "soft underbelly"
> Will provide for 200 sq. ft. cabins (equal or larger than "Luxury cabins" on most cruise ships).
> Will provide a central hull which could prove very useful in a wide variety of ways.
> Will provide more resistance to pitching.
> Will provide more resistance to rolling
> Will provides a shallower draft.
> Will maintain the chines (hull corners) well above the water line (providing less resistance)
> Will provide more resistance to leeway (being blown sideways)
> Will have a smaller waterline hull beam (providing less resistance).
> Will provide for shorter spans (and therefore less loading) on athwartship beams
> Will provide more "dock space" for the tenders.
Cons
> Will cost more to build.
> Will cost more to maintain
> Will weigh more,
> Will require more construction time
> Will have more wetted surface
> Will require more bottom paint.
Other alternatives.
One alternative would be to increase the beam to the same 45 ft. - without adding the third hull.
At the moment, we feel that this would be verging on overloading the hulls - thereby creating several negative effects. Pending accurate detailed weight calculations, we would keep this option open
Another alternative would be to do the above and increase the beam of the hulls - in order to gain buoyancy. This option is dismissed out of hand for many reasons - not the least of which is that it is a step backwards towards your average, fat hulled catamaran.
Whatever decision is finally made, will depend on accurate detailed weight calculations. However, with our current rough estimates, we are leaning at the moment towards the alternative shown on this page. This being the case, let us take another look at those 8 man "Heavyweight" rowing shells - compared to Grand Illusion XL - XW (extra long - extra wide)
We have recently come across a few claims that a trained "heavyweight" rower may be capable of generating as much as 0.5 hp. over a 2000 meter course. To err on the conservative side, we have used this number in the following table.
Boat waterline length gross weight power required speed
(3) 8 man shells 55 ft. 5,610 lbs. 12 hp. 12 knots
(3) 160 man shells 150 ft. 112,200 lbs 240 hp. 19.8 knots
Grand Illusion XL - XW 150 ft. 112,200 lbs 240 hp. 19.8 knots
Grand Illusion XL - XW 150 ft. 120,000 lbs 257 hp. 19.8 knots
Grand Illusion Xl - XW 150 ft. 130,000 lbs. 278 hp. 19.8 knots
Grand Illusion XL - XW 150 ft. 140,000 lbs. 299 hp. 19.8 knots
Our most up to date rough estimates put the gross weight of Grand Illusion XL - XW at less than 120,000 lbs. - for a requirement of 257 hp. There is also the lower wetted surface of the round bottom rowing shells to be accounted for. However, with this configuration (at this weight) the chines of Grand Illusion XL - XW will be well out of the water. This will reduce the hull beam and consequently the resistance and likely cancel out the advantage of the shells - in regard to wetted surface.
At any rate, even adding a 5% penalty for increased wetted surface - and even if our weight estimates are a bit optimistic - and there is also some added resistance due to interference between the hulls, it appears virtually certain that:
Grand Illusion XL - XW will do a minimum of 20 knots with 300 hp.
This would be a truly extraordinary performance - extraordinary enough, one would think, to warrant Al Gore and his buddies, or anyone else, for that matter, with an ounce of environmental concern (or avarice) showering us with e mails and phone calls. One can well imagine then, that after 50 years, from time to time, it gets a tad frustrating ----- waiting for the same.
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How about those rowing shells!
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