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Lifting Foils

Lifting foils were pioneered in the prototype F-27 back in 1985. These were circular all carbon foils that could retract behind the beam, to still retain easy trailering, while avoiding the need to remove when folding or docking.

Retracted and curved lifting foil can be seen just behind forward beam.
Note that Sailing while folded as shown is NOT a recommended procedure

They worked well while reaching, but were heavy and very expensive to produce, and thus their inclusion on an 'all round' production boat could not be justified. The smaller floats used were then changed to larger floats on the production F-27, for good overall performance, and more offshore capability in very large waves. Non-retractable foils are used on some other designs, but these make folding more difficult, are a hindrance in light airs, slow down tacking, and make beaching the boat very impractical.

Simpler straight foils, as used by Kim Alfred's F-31 Cheekee Monkee (above), the F-9R Wilparina, and the F-35C are less expensive, and appear to work well. Details of where and how such foils should be fitted can be supplied, but they remain expensive and still have various practical issues.

The F-35C Blue Moon (line honors in 2007 Harvest Moon regatta by 1hr and 22 minutes)

2010 - The Latest Curved Foils:

CNC machining and modern resin infusion techniques have now made it more practical to manufacture curved foils, and thus they are now being utilized on the F-32SR and the F-85SR, details being at:

F-85SR

F-32SR

However, such production foils must be used within their specified limits, as it is difficult to make them strong enough to support the full weight of the boat, something they were not originally designed to do when developed back in 2010. However, since then, the America's Cup competition has shown that large multihulls can be setup to be flown on the leeward foil only, in conjunction with T foils on the rudder, but this greatly increases the loads on the foil, which could lead to breakage, as has happened.

The standard production F-32SR foils have proved to be very effective, and in fact it has been shown that the boat can fly on them, even without T foil rudders for trim. However, the foils are very long for light wind effectiveness, and as such can also break when used beyond their specified limits, and particularly when fully down in large waves. To prevent this, the production foils are now almost solid carbon. but they still must be retracted up to 400mm in higher winds to be safe long term. Stronger all epoxy foils are also now available, but these are much more expensive:

Foil Pricing

Video of F-32SR Foils in Use

Foils being used at risk of breakage. Conditions here are too rough for the foils to be used fully
extended, and three have broken. Fully extended extra long foils will be over their limit in these
conditions even without big waves, which then add impact loads to where a breakage becomes likely:

Recent Foil Break Test

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