The Hull of a JY 15
Production
-Three layers
Outer plastic skin
-1/8” thick
-High impact—resistant ABS and UV resistant
-Plexiglass
Central foam core
Inner fiberglass skin
Production
-Hull and the deck are formed using thermoforming
-Vacuum draws heated plastic sheet into mold
-Plastic skin reinforced by foam core
-Plastic hull put in matched mold with a 1” gap in between the mold and the hull
-Liquid foam is injected into the gap under high pressure
-Foam expands and fills the layer
-3rd layer is the fiberglass
-Cloth put on the hull and attaches to the hull during the foaming process
-Integrated into hull as foam expands
Benefits
-Strength
-ACP stronger than fiberglass
-No fibers to break, so hull will not soften
-Maintenance and Repair—easier than fiberglass
-Uniformity and Rigidity
-Better in both
-Vital for a one-design class (racing where all boats are identical)
-Cost
-Less labor intensive
-Less expensive in labor costs
-Environmentally friendly
-Amended Clean Air Act—restricts fiberglass manufacturing and limits styrene emissions

Sails and the Fibers Used in Making Modern Sailcloth
-Polyester
oClassic sailcloth
oLow stretch, good strength, low cost, durability
oCan be heated and shrunk during weaving—tightly woven cloth
oCruising sails and casual racing
oBrand—Dupont Dacron
-Higher strength, lower stretch, maximum shrinkage
-Nylon and Polyester Spinnaker Fabrics
oMostly downwind sails—light, strong, affordable
oRelatively stretchy—absorbs shock loads and makes it easier to fly
oNylon—most susceptible to UV damage and chemical degradation
oNew—polyester spinnakers
-Less stretch (especially when wet)
-Requires extra expertise in manufacture and design
Aramids
-High performance fiber in laminated sailcloth
-Kevlar—brand name
-Lighter than woven Dacron and polyester laminates
oGreater effectiveness in different wind ranges
oHigher cost, shorter sail life
oSusceptible to UV damage and breakdown due to folding
-Carbon Fiber
o1st used in America’s Cup
oVery low stretch, low weight, high cost
oBlends carbon fiber with Aramid in hybrid 3DL laminates
-Technora
oSimilar to moderate grade Kevlar in chemistry and performance
oHigher strength but loses it rapidly in UV damage
-Spectra (Dyneema in Europe)
oLower stretch, higher strength, better UV resistance and much less strength loss
oWill stretch in long term loads—not used for racing
oExcellent for large performance cruising boats
oUsed to be very expensive
-It was also used in bulletproof vest and fishing line
-Manufacturers increased production and lowered prices
PBO
oTop of performance pyramid
oBeats all but most exotic carbons in strength and stretch
oOffers option to Grand Prix level big boats to save weight and get extra wind range if spend a little bit more money
oDisadvantage—short life
oNorth Sails
-Produces a PBO/Aramid hybrid
-Used for around the world racing
-Hybrid
oBoosts performance
oReduces risk of sail failure in rough southern oceans
-Other manufacturers of PBO
oNumerous sail failures
oLack of forgiveness when sail is folded
-Produces full PBO/hybrid PBO hybrid
-Made for smaller boats
-Just 8 month old technology, so results are not known
-Pen
oRelative of polyester but stronger and less stretch
oOption for smaller racing sails when Aramid is not possible because of budget
oWoven form
-Limited to short life
-Resinated
-Required to maintain stability
-As resin breaks down—natural weave loses stability and sail loses design shape
-Not recommended
oLaminating
-Doesn’t require tight weave for stability-comes from Mylar in cloth, not in weave
-Well suited for paneled Mylar racing
-Can chose between polyester and Kevlar or Spectra (depending on budget)
-Best suited for boats under 40 feet
-New Technology in Sail Making—3DL
-Used to assemble sail out of pieces of flat sail cloth (paneled)
-3DL
oMolds sails three dimensionally into single seamless piece
oAdvantages
-Stretches less than paneled sail
-Holds shape over wider wind ranges
-Retains design shape longer
-Dominates Grand Prix racing
-Used on America’s Cup finalists in 2000