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New Nacra 17 foil bearing to be retro-fitted this week

Nacra Sailing has announced that the new bearing design for the Nacra 17 foils has been completed and the first prototype will be built and tested this week.New two-piece replacement bearing cassette -

The Nacra 17 medal racing at the World Sailing Aarhus Test Event was cancelled last week after manufacturer Nacra Sailing recalled all foiling configuration Nacra 17s because of possible foil bearing failure.

The prototype will be fitted to a boat to ensure it physically works and that it fits properly.

The prototype is an adaptation of an existing design for high performance catamarans so no problems are expected.

The new design is a two part cassette to provide a bigger (19mm) bearing surface for the foil. With a moving part, however, it must, and will, be checked.

The prototype will then be fitted to the test jig. Working load and breaking strength tests will be performed.

This to ensure the larger, load-bearing, surface solves the crushing problems that have been occurring with the original bearing.

Original bearing cassette - Click image for a larger image

Assuming both of these tests confirm the prototype as a solution, production will begin on Wednesday (16 August).

The bearing replacement procedure is simple. Each lower bearing is held in by 4 “allen key” screws. Teams will be able to change the bearing themselves.

The production facility has set aside their complete machining capability for the parts to be built at a rate of at least 15 sets per day.

Questions have also been asked about the suitability of the boards exposed to the high point loading of the original bearing, and specifically whether these boards can continue to be used.

The initial assessment by Nacra Sailing is that the mode of failure of the boards is via a crushing of the board first, followed by shearing of the material after it loses its shape.

As such, any boards without crushing should be ok.

Morrelli & Melvin, the designers of the boards, will continue to investigate this question and have been asked to produce an opinion on the matter.

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