Cal's Evals » ALIBI 54

Release Date: 11/13/2013

Alibi 54 - 2013

The Alibi 54 is an impressive racing/cruising catamaran designed by French designer Loc Goepfert. It is also known as the Aeroyacht Alibi 53, an earlier pre-production boat. It is very similar in appearance to several designs of Morrelli and Melvin. So, in addition to the usual comparison with several boats of near the same waterline length from the Multihull Dynamics website, this evaluation will include a comparison with the Gunboat 55. The numbers below provide the specifications, performance and stability data for the Alibi 54, followed in brackets by the average of 26 boats with waterline lengths between 53 and 54.75 feet, the value at the trendline for the MDI database of 986 cruising catamarans and last the Gunboat 55.

Hull length overall: 54.30 feet [55.52 average, (undefined) for the trendline, and 55 for G55]

Waterline length: 54.30 [53.71 average, (undefined) trendline, 54.75 for G55]

Displacement: 8.80 tons [14.79 average, 12 trendline, and 10.44 for G55]

Sail Area: 1323 sq. ft. [1581 average, 1500 trendline, and 1669 for G55]

Displacement-Length Ratio: 27.48 [47.67 average, 41 trendline, and 31.81 for G55]

Sail Area-Displacement Ratio: 29.01 [25.57 average, 27 trendline, and 32.65 for G55]

Beam between hull centerlines: 22.23 feet [23.38 average, 23 trendline, and 23.38 for G55]

Base Speed: 12.88 knots [12.03 average, 12.5 trendline, and 13.45 for G55]

Texel Rating: 111 [118.43 average, 111 trendline, and 102 for G55]

Bruce Number: 1.35 [1.25 average, 1.32 trendline, and 1.25 for G55]

Stability Speed: 20.70 knots [24.72 average, 22.2 trendline, and 18.04 for G55]

The displacement for the Alibi 54 is an estimate of cruising displacement based on 2/3 of the specified payload. This is a standard practice for Multihull Dynamics evaluations when design or cruising displacement is not listed. The Alibi 54 design shows the capability of being a credible racing boat in several areas. She is much lighter than average but carries slightly below average sail area for a SA/D ratio that is significantly above average. Her Bruce Number shows a power to weight indicator that is above average as well. Her Base Speed is over a three quarters of a knot higher than average. Her combination of displacement, sail area and centerline beam give her a lower than average stability, not unusual for boats biased toward racing. Her modest sail area is the only factor that keeps her from being comparable to the Gunboat 55.

Other hints of racing emphasis visible in the Alibi 54 design on their website at http://www.aeroyacht.com/sailing-catamarans/alibi-54-65-catamarans/alibi-53/ are the use of high aspect ratio asymmetric dagger-boards, a raked wing mast with square-topped mainsail and reversed (wave piercing) stems. Her bowsprit has an a-frame configuration with dinghy storage at the aft end under the bridgedeck leading edge.

Calvin H. Markwood
Engineering Analyst
Multihull Dynamics

Contact Cal: multihull.analysis@comcast.net

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