OSEP-16 Hull: Fusion 360 Step-by-Step Guide

Overview

You’re going to build a parametric 3D model of the asymmetric proa hull using lofting techniques. This guide assumes basic Fusion 360 familiarity.

Time required: 3-4 hours (first time)
Difficulty: Intermediate
Result: Fully parametric hull model ready for panel development

Prerequisites

Files You Need

hull-points.csv - Point cloud data
hull-mathematics.md - Reference dimensions

Fusion 360 Setup

Units: Set to inches (Edit → Preferences → Default Units → Inches)
Workspace: Use “Design” workspace
New Design: Create new design, name it “OSEP-16_Main_Hull_v1”

Part 1: Import Point Cloud

Step 1.1: Prepare CSV Import

Action: Create → Insert → Insert Mesh

Problem: Fusion 360 doesn’t directly import CSV as points.

Workaround: We’ll use sketches to place points manually at key stations.

Step 1.2: Alternative - Manual Station Sketching

Better Approach: Create sketches at each station with exact points.

Action:

Create → Create Sketch
Select XY Plane
We’ll create 11 station sketches

Part 2: Create Station Sketches (Cross-Sections)

Station 5 (Center/Max Beam) - Start Here

This is the widest, most complex station. Master this, then the others are easier.

Step 2.1: Create Station 5 Sketch

Action:

Create → Create Sketch
Select XY Plane
Sketch → Project/Include → Offset Plane
Offset: 96” (this positions station 5 at hull center)
Name plane: “Station_5”

Step 2.2: Draw Station 5 Cross-Section

Draw these points exactly (refer to hull-mathematics.md):

Leeward Side (Left):

Point L1: X = -12", Y = -8"  (keel)
Point L2: X = -11", Y = -4"  (mid)
Point L3: X = -10", Y = 0"   (chine)
Point L4: X = -8",  Y = +8"  (turn)
Point L5: X = 0",   Y = +16" (sheer/deck)

Windward Side (Right):

Point W1: X = +12", Y = -8"  (keel)
Point W2: X = +11", Y = -4"  (curved)
Point W3: X = +10", Y = 0"   (chine)
Point W4: X = +8",  Y = +8"  (turn)
Point W5: X = 0",   Y = +16" (sheer - same as L5)

Drawing Process:

Sketch → Spline → Control Point Spline
Leeward side (flat):
- Click points L1, L2, L3, L4, L5 in sequence
- Make segments nearly straight (adjust control points)
- This creates the “flat” character
Windward side (curved):
- Click points W1, W2, W3, W4, W5
- Adjust control points to create smooth curve W1→W3
- Keep W3→W5 similar to leeward side
Connect ends:
- Line from L1 to W1 (keel bottom)
- L5 and W5 are same point (sheer at centerline)

Step 2.3: Add Dimensions

Critical dimensions to constrain:

Horizontal Sketch Dimension:
- L1 to origin: 12”
- W1 to origin: 12”
- L3 to origin: 10” (chine)
- W3 to origin: 10” (chine)
Vertical Sketch Dimension:
- L1 Y-value: -8” (keel depth)
- L5 Y-value: +16” (sheer height)
- L3 Y-value: 0” (chine at waterline)
Make symmetric about Y-axis where appropriate (sheer point)

Step 2.4: Finish Sketch

Action:

Sketch → Finish Sketch
Rename sketch: “Station_5_Section”

Result: You now have the master cross-section.

Stations 0 & 10 (Bow/Stern Points)

These are simple - just single points.

Step 2.5: Create Bow/Stern Sketches

Station 0 (Bow):

Create Sketch on XY plane
Offset: 0” (at origin)
Draw single point: (0, 12) - sheer
Draw single point: (0, -2) - keel
Finish sketch, name “Station_0_Point”

Station 10 (Stern):

Create Sketch on XY plane
Offset: 192” (full hull length)
Draw same points as Station 0
Finish sketch, name “Station_10_Point”

Intermediate Stations (1-4, 6-9)

Efficient method: Copy Station 5, modify dimensions.

Step 2.6: Create Station 1

Copy Station 5 sketch
Paste at new offset plane: Z = 19.2”
Edit dimensions:
- Beam (L/W 1): 6” (was 12”)
- Sheer height: 14” (was 16”)
- Keel height: -4” (was -8”)
- Chine beam: 5.5” (was 10”)

Reference table for all stations (from hull-mathematics.md):

Stn | Z-offset | Max Beam | Sheer Height | Keel Height | Chine Beam
----|----------|----------|--------------|-------------|------------
 | 19.2"    | 6"       | 14"          | -4"         | 5.5"
 | 38.4"    | 9"       | 15"          | -6"         | 8.5"
 | 57.6"    | 11"      | 16"          | -7"         | 10"
 | 76.8"    | 11.5"    | 16"          | -7.5"       | 10.5"
 | 96"      | 12"      | 16"          | -8"         | 10"
 | 115.2"   | 11.5"    | 16"          | -7.5"       | 10.5"
 | 134.4"   | 11"      | 16"          | -7"         | 10"
 | 153.6"   | 9"       | 15"          | -6"         | 8.5"
 | 172.8"   | 6"       | 14"          | -4"         | 5.5"

Repeat for each station 1-4 and 6-9.

Tip: Use parameters to make this faster (next section).

Part 3: Parametric Design (Optional but Recommended)

Step 3.1: Create Parameters

Why: Change one number, update entire hull.

Action:

Modify → Change Parameters
Add User Parameters:

Parameter Name    | Unit   | Expression | Comment
------------------|--------|------------|------------------------
LOA               | in     | 192        | Length overall
max_beam          | in     | 24         | Maximum beam
max_draft         | in     | 8          | Draft at centerline
sheer_height      | in     | 16         | Deck height at center
rocker            | in     | 6          | Total rocker (ends to center)
station_spacing   | in     | 19.2       | Distance between stations

Step 3.2: Link Sketches to Parameters

Edit each sketch:

Right-click dimension → Edit
Change value to parameter name (e.g., max_beam instead of “12”)
Repeat for all constrained dimensions

Benefit: Want a 17’ hull? Change LOA to 204”, entire model updates.

Part 4: Loft the Hull Surface

Now comes the magic - turning 11 cross-sections into a 3D hull.

Step 4.1: Create Loft

Action:

Create → Loft
Profiles: Select each station sketch in order (0 → 1 → 2 → … → 10)
Rails: (Optional) Create sheer line and chine line as guide curves
Operation: New Body
Click OK

Result: Smooth hull surface flowing through all stations.

Step 4.2: Verify Surface

Check:

Rotate model - no sharp edges or kinks?
Inspect curvature - smooth transitions?
Measure beam at station 5: Should be 24”
Measure length: Should be 192”

Fix issues:

If kinked: Adjust spline control points in station sketches
If bumpy: Add more intermediate stations
If asymmetric: Check leeward vs windward curves

Part 5: Add Internal Structure

Step 5.1: Bulkheads

Create bulkhead planes:

Construct → Offset Plane
Create planes at:
- Station 2 (38.4”)
- Station 4 (76.8”)
- Station 6 (115.2”)
- Station 8 (153.6”)

Intersect with hull:

Create Sketch on each bulkhead plane
Sketch → Project/Include → Project (select hull surface)
This creates bulkhead outline
Add cutouts for:
- Drainage (bottom)
- Access hatches (top)
- Weight reduction holes (sides)

Step 5.2: Deck

Create deck surface:

Create Sketch on plane at Y = 16” (sheer height)
Project sheer line from hull
Offset inward 2” (deck has crown)
Extrude → Direction: down 0.25” (deck thickness)

Part 6: Panel Development (3D → 2D for CNC)

This is critical - how to flatten the 3D hull into cutable panels.

Step 6.1: Leeward Panel (Flat Side)

Method: Surface Flatten (built-in Fusion tool)

Inspect → Section Analysis
Select leeward surface
Create → Surface → Patch (if surface has holes)
Manufacture → Fabrication → SMD Flatten (Sheet Metal Development)

Settings:

Face: Select leeward hull surface
Stationary Edge: Bottom (keel line)
Manufacturing Model: New Component

Result: Flat panel with exact shape, ready for CNC.

Step 6.2: Windward Panel (Curved Side)

Challenge: Windward side has 3D curvature (can’t flatten perfectly).

Solution: Torturing Plywood

Flatten using SMD Flatten (will show distortion)
Note distortion map
Plan panel with extra width (plywood will compress)
Create “torture jig” sketch showing required bends

For OSEP-16:

Windward panel develops ~8% longer than flat projection
Use 6mm plywood (flexible enough to bend)
Pre-wet plywood before installation (easier bending)

Step 6.3: Bottom Panel

Select bottom surface (keel line)
SMD Flatten
This panel is simpler (less curvature)

Step 6.4: Export DXF for CNC

Action:

Right-click flattened component
Export → DXF
Save as: OSEP16_Panel_Leeward.dxf

Repeat for:

Windward panel
Bottom panel
Bulkheads
Deck

Part 7: Nesting on 4’x8’ Sheets

Step 7.1: Import DXF to Nesting Software

Options:

Fusion 360 CAM (built-in, nesting add-on)
Deepnest (free, open-source)
OptiNest (commercial)

Process:

Import all panel DXFs
Set material size: 48” x 96” (4’x8’ sheet)
Set margin: 0.5” (blade clearance)
Auto-nest or manual arrange

Goal: Fit all panels on 6 sheets (3 for main hull, 2 for ama, 1 for bulkheads).

Step 7.2: Generate Toolpaths

In Fusion 360 CAM:

Manufacture → Setup → New Setup
Stock: 4’x8’ x 0.25” (6mm plywood)
Zero Point: Lower-left corner
Machining Origin: X0, Y0, Z0

Create 2D Contour:

2D → 2D Contour
Select panel outline
Tool: 1/4” upcut spiral bit
Depth: 6.5mm (through-cut + 0.5mm into spoilboard)
Tabs: 4 per panel, 0.5” x 0.25” (holds part in place)

Generate G-code:

Actions → Post Process
Select post: Grbl / MACH3 / LinuxCNC (depends on your CNC)
Save as: OSEP16_Sheet1_Panels.nc

Part 8: Verification & Quality Checks

Step 8.1: Mass Properties

Action:

Inspect → Component Properties
Check mass (should be ~85 lbs for hull shell only)

Material density for calculation:

6mm Okoume plywood: 0.015 lb/in³
Expected mass: ~85-90 lbs bare hull

Step 8.2: Volume Calculation

Action:

Inspect → Measure → Volume
Select hull interior
Should match calculated 11.6 cu ft (20,019 cu in)

Step 8.3: Waterline Check

Action:

Create plane at Y = 0 (designed waterline)
Inspect → Section Analysis
Verify hull sits correctly at DWL
Check: Beam at waterline = ~20” (immersed section)

Part 9: Export for Documentation

Step 9.1: Renderings

Create hero images:

Render → Render
Environment: Studio (clean white background)
Camera angles:
- Isometric (3/4 view)
- Side profile
- Top plan view
- Cross-section at station 5

Settings:

Material: Wood (Okoume)
Lighting: Studio soft
Resolution: 1920x1080 minimum

Step 9.2: Technical Drawings

Create 2D drawings:

Drawing → From Design
Create sheets:
- Sheet 1: Overall dimensions (plan, profile, sections)
- Sheet 2: Panel development (all flat panels)
- Sheet 3: Bulkhead details
- Sheet 4: Assembly sequence

Export:

Format: PDF
Scale: 1:10 (or fit to page)
Save as: OSEP16_Hull_Drawings_v1.pdf

Step 9.3: 3D Export

Export 3D models:

STEP format (universal CAD):
- File → Export → STEP
- Save as: OSEP16_Hull_v1.step
STL format (3D printing, visualization):
- File → Export → STL
- Resolution: High
- Save as: OSEP16_Hull_v1.stl
OBJ format (web viewers):
- File → Export → OBJ
- Include textures
- Save as: OSEP16_Hull_v1.obj

Part 10: Tips & Troubleshooting

Common Issues

Issue: Loft creates twisted surface

Fix: Ensure all station sketches have same “start point” (e.g., keel centerline)
Reorder loft profiles to flow smoothly

Issue: Panel won’t flatten (SMD Flatten fails)

Fix: Surface has too much Gaussian curvature
Split surface into smaller patches
Use approximation (slight stretching acceptable)

Issue: Nesting doesn’t fit on 6 sheets

Fix: Rotate panels for better packing
Reduce margin slightly (0.5” → 0.375”)
Accept using 7 sheets instead of 6

Issue: Parameters don’t update entire model

Fix: Some dimensions not linked to parameters
Edit each sketch, link all dimensions
Use “Capture Design History” to trace dependencies

Optimization Tips

Speed up workflow:

Use “Copy Sketch” for similar stations (faster than redraw)
Create templates for bulkheads
Save camera views for quick navigation
Use keyboard shortcuts (S = sketch, E = extrude, L = loft)

Improve accuracy:

Enable “Grid Snap” at 0.125” intervals
Use “Measure” tool frequently
Create construction geometry for alignment
Add reference points before lofting

Part 11: Next Steps - Ama & Crossbeams

Once main hull is complete:

Ama (Outrigger):

Similar process, simpler geometry (symmetrical)
12’ length, 18” beam, 6” draft
Fewer stations needed (7 instead of 11)
Estimated time: 1-2 hours

Crossbeams (Akas):

Simple cylinders, 4” OD aluminum tube
Model mounting pylons on main hull
Design quick-release mechanism
Estimated time: 1 hour

Completion Checklist

Before considering hull model “done”:

Resources

Fusion 360 Learning:

Autodesk Fusion 360 YouTube (official tutorials)
Lars Christensen (boat design in Fusion)
Product Design Online (lofting techniques)

Boat Design:

Duckworks Magazine (amateur boatbuilding)
WoodenBoat Forum (traditional methods)
Boat Design Net (technical discussions)

CAM & CNC:

Fusion 360 CAM tutorials (built-in)
Winston Moy (CNC basics)
NYC CNC (professional techniques)

You now have everything to build the hull in Fusion 360.

Estimated total time: 4-6 hours first attempt, 2-3 hours once practiced.

Questions? Refer to hull-mathematics.md for exact dimensions.

Next: Build the ama (outrigger) using similar process.