Nacra 17 MKII

Configuration Update September, 2016

Prepared by: Pete Melvin Last Olympic Quadrenium – The Quest for Full Foiling

Olympic Sailors developed sailing techniques to sail the N17 MK1 at high Lift Fractions and even achieved short stints of Full Foiling on regular bases. Challenging the structural design.

2 Nacra 17 MKII Proposed Configuration

• Existing platform size is ideal for mixed crew weight range • The rig is efficient and well developed. Due to the closer AWA for foiling, the sprit will be shorter and the gennaker will be flatter • The hull shape is still modern and effective for a foiling catamaran • Cost effective solution compared to other foiling catamaran options • Configuration and foil development currently underway

3 A. Introduction

Morrelli & Melvin Design Team’s involvement into the MKII

• Review Hull Structural Specifications • Setup VPP program for foil design, balance & Propose sail plan refinements • Foil Design & Engineering • 4-Foil Configuration, CZ-Foils • 3-Foil Configuration, Tip-up foil design • New Rudder design • Rudder housing design review and FEA analysis, based on design provided by Nacra.

4 Design Tools – Foil Fluid Analysis & Structures

5 Design Tools – VPP, Performance Analysis

Evaluation of different foiling system options using the North Used for: Sails six degree-of-freedom VPP. • Appendage Foil design studies • Balance e.g. Helm Balance Foil Design and Hydro data input courtesy Morrelli & Melvin • Loadings for structural reviews • Overall Performance Polars Hull Hydro and Rig Aero data courtesy North Sails Group. • RaceModel

6 Foil Design Considerations

Main Design Considerations: • Heave Stability - or Flight Height Stability • Heave Stability Analysis by Foil design program and VPP • Pitch Stability • Pitch stability analysis similar to airplane theory, change in pitch angle ∂Cm/ ∂AoA • Ventilation Developed Lift/Area Foil Loading Criteria Diagrams • 2D custom Foil Section development • Boathandling • Optimum Crew Weight – VPP RaceModel • Performance - VMG

7 T-Rudder Design

8 Daggerboard Design

9 Design Tools – VMG Performance

WHY 4-Foil Configuration? • Up-tip style foils require a lot of energy to raise and lower. On larger crewed boats this is a challenge but you have enough crew to make it work. On two-handed beach cats on a short course, we have found the up-tip Uptip Foil style boards to be challenging to raise and lower and can cause slow maneuvers. They CZ Foil are best suited to distance racing boats where their straight-line speed advantage can be exploited. We believe the CZ style C Foil foils would make for better and more exciting short course racing • Sailing is greatly simplified since it is not necessary to fully retract the windward foil downwind. In fact, in order to achieve adequate lift and heave stability the windward foil must be left down. • CZ foils are considerably easier and less expensive to build than up-tip style foils since you do not have to build the structurally challenging tip elbow. In fact, we expect the CZ foils to be similar in manufacturing complexity to the existing C foils.

10 Design Tools – VMG Performance

C Foil

CZ Foil

11 MKII HULL- STRUCTURAL LAY-OUT UPDATE

NEW DAGGERBOARD-CASE CONNECTING TO OUTBOARD HULL INNERSKIN FUNCTIONING AS LONGITUDINAL FRAME

ADDITIONALADDITIONAL “SLAMMING” FRAMES IN ADDITIONAL “SLAMMING” FRONTFRAME & AFT of THE FRAME DAGGERBOARD -CASE

BOTTOMBOTTOM & & DECK DECK BEARING BEARING HOUSING HOUSING ARE ARE INTEGRATEDINTEGRATED IN IN THE THE HULL HULL LAMINATE LAMINATE PROVIDING PROVIDING SOLIDSOLID CONSTRUCTION CONSTRUCTION WITHOUT WITHOUT JOINTS JOINTS

12 MKII HULL – LAMINATE SCHEDULE UPDATE

A. Carbon Fiber Innerskin B. Extra full hull girth reinforcement laminate, FWD Beam and Shroud C. Hull Joint flange carbon fiber reinforcement patching D. Daggerboard-case bearing housings carbon fiber patching E. Beam reinforcement patching of carbon fiber F. Transom Carbon fiber reinforced patching

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