Pacific Proa compared to Catamaran
Morphing a 42' catamaran into a 70' proa

Quite simply, the reason for building a modern Pacific proa is the same as it was centuries ago in Micronesia, where the hull form evolved: to get the longest possible "main hull" with any given weight - which translates to COST of materials and labor.
 

Take the rig from any modern cruising catamaran and use it to push a longer main hull with the same overall weight, and the result is greater comfort and speed. The Pacific proa configuration uses sails that would be too small on a catamaran of the same length, yet work well on the proa.

Pacific Proa Advantages:
The Pacific proa gets advantages over the catamaran by using the same weight of materials (cost!) to create a significantly longer main hull with higher speed potential:

  • a longer hull is more easily driven for fast ocean passages and more appropriate to the scale of large seas offshore.
  • transferring up to 100% displacement to the single large leeward hull as the windward hull lifts results in smooth, comfortable speed with minimal wetted surface.
  • when pressed for maximum speed, the longer leeward hull with similar rig and no additional lateral stability (the ability to resist tipping over sideways) results in greater longitudinal stability than a catamaran. Instead of pitchpoling, the Pacific proa will roll gently onto the leeward pod .
  • a small, lifting hull to weather for stability is mechanically easier and lighter than connecting two hulls of equal size and weight (catamaran) or using "floats" of 100%+ buoyancy on either side (trimaran). While modern materials and methods make structure less of an issue, the crossbeams on a Pacific proa are less stressed than a catamaran of similar displacement.

For the very same reasons, however, it is also true that the Pacific proa carries much less weight for it's length than a catamaran.

Catamaran Advantages:
  • The catamaran has broad flat transoms aft that carry weight well and reduce pitching; the proa is pointed at both ends.
  • The catamaran has extra privacy afforded by two hulls for accommodations.
  • Since there is only one large hull, adding length to a proa returns less accommodation volume and weight carrying capacity than the same length added to a catamaran.
  • The proa's main hull might be narrower than the catamaran, using a length to beam ratio of 17:1 for speed, resulting in a smaller interior space.

For these reasons, a 21 meter (69') proa has barely the same accommodations as a 43' catamaran. When compared to an 18 meter (59') catamaran, the 21 meter proa has significantly less accommodation volume...

Conclusions:

A 69' Pacific proa may have only half the displacement of a 59' catamaran, yet it requires less sail area, cost, and has a longer main hull designed to carry the ama flying.

For the same price and using the same size rig as a 60'+ catamaran, a 90' Pacific proa with superior performance potential can be built.

Accommodation plans for large proas remain a challenge while cruising catamaran plans have been widely explored for decades.

web site under construction

 
43' catamaran, 69' proa, 59' catamaran




70' proa with similar displacement, accommodation, sail area and cost to 42' catamaran (below, to scale).




Click for rotating view! (253K)

Web site by wingo.com
Contact:
Northern California
Also: Jim Antrim, Naval Architect

Links to other Proa Web Sites