Hull designs for VJ12

From 2011 to 2019 former 12ft Skiff Interdominion and Australian Champion and naval architect David Cleworth designed several variations of a new 12ft long hull for the VJ Amateur Sailing Association.

On 13th November 2021 the VJ Amateur Sailing Association voted to amend the name of the new boat to ‘VJ12’ in order to distinguish it from the classic VJ design. The aim of the VJ12 name is to maintain the connection to where the new design has evolved from and the role of the boat.

The new designs are:

1. Hull 6C – widest on waterline and most stable hull. Hull 6C was redesigned in early 2019 by David Cleworth with finer bow sections and named 6CR

2. Hull 6Y – middle design version designed in August 2018. A finer bow version 6YS was designed in November 2018

3. Hull 6X – narrowest design version and potentially the fastest. 6X was designed in November 2018 and a subtle variation with chines was also designed at that time named 6XC

The 9 year design journey was extremely enjoyable – yet very complex and involved many discussions and different versions drawn and evaluated.

Please see this page for the whole design journey including trials, reasoning, photos and design diagrams:

From VJ to VJ12 the journey from 2011 – 2019

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23rd November 2019:

Hull 6YS and 6X:

The latest variations of the 12ft long VJ hull were designed by David Cleworth from June 2018 to November 2018 and are named 6YS and 6X.

These hulls are slimmer overall and finer in the bow than 2012’s Hull 6C, and both 6YS and 6X also have more freeboard than 6C with stem height being 460mm/18″ and transom height 381mm/15″

The narrowest design is 6X, followed by 6YS, and the widest and most stable design is 6C.

Hull 6X has been designed both with chines and without although there is only a subtle difference between the ‘chines’ and ‘no chines’ versions.

Below are images of 6XC (chines).

VJ 6XC Frames Buttocks & Waterlines

VJ 6XC Frames & Diagonal Slices

PDF of Table Of Offsets for Hull 6X and 6XC:

VJ Hull 6X with chines Table Of Offsets pdf

VJ Hull 6X no chines Table Of Offsets pdf

Below are photos taken of the computer screen during the design process of Hull 6X which compare 6X in pink with the 12ft Skiff ‘Woof’ hull in green:

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Hull 6Y/6YS:

Hull 6Y was designed in July-August 2018 and was refined in November 2018 to be Hull 6YS which has a finer entry and forward sections.

Following Lindsay Allan’s request for a narrower hull than 6C which he built and launched in Sept 2016, Hull 6Y began as a narrower version of the 2012-13 Hull 6C:

VJ 6Y Plot 2019 plan & elev diagonals

VJ Hull 6Y 3650 Plot DXF File pdf

VJ Hull 6Y Plot 2019 plan wl & elev buttocks

VJ Hull 6Y Table of Offsets pdf

Below are photos taken of the computer screen which compare hull 6Y (light blue) with ‘Woof’ (green)

4th August 2018 Hull 6Y light blue and comparison with 12ft skiff hull Woof in green

4th August 2018 Hull 6Y light blue and comparison with Woof green closeup

Hull 6YS was a further refinement of 6Y and was designed in November 2018. It has combined aspects of 6X (notably the finer bow sections) with aspects of 6Y, however all parameters have been adjusted to make 6YS a balanced hull design.

VJ Hull 6YS diagonal slices chine line

PDF:

VJ 6YS Diagonal Slices – with hidden chine line v good

VJ Hull 6YS diagonal slices visible chine

PDF:

VJ 6YS Diagonal Slices- with defined chine v good

PDF:

VJ 6YS Buttocks & Waterlines – with hidden chine line v good

VJ Hull 6YS dxf plot file

VJ Hull 6YS Table Of Offsets

PDF:

VJ 6YS Table of Offsets

Tutorial for use of Table Of Offsets

Tutorial for use of Table of Offsets (pdf)

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Comparison overlay images of the VJ hull designs 6C, 6Y and 6X:

6C is drawn in purple and has lower topsides than 6Y (light blue) and 6X (pink)

Overlay of VJ Hulls 6C, 6Y and 6X

Overlay closeup #1

Overlay closeup #2

Below are comments from David Cleworth about the above overlay of the 3 designs:

“This is a very rough 2D view of the relativities, the difference in the topsides is a different story with 6XC the widest at the tuck and straightest.

(Note from Greg Fryer: 2016’s 6C would be the widest at the transom if it had the same topside height as the narrower hulls 6Y and 6X. In 2018 we raised the stem and transom height in 2018 for the next design drawn which was 6X. In 2018 after 2 seasons of sailing the new hull 6C against the older classic VJ designs such as Big Apple IV and Go Hard, we realised the new hulls would benefit from having a little more height at stem, topsides and transom.)

6C is purple (Plan Theoretical Waterline is Red)

6Y is light Blue with White topsides in frames. (Plan Theoretical Waterline is widest Yellow)

6XC is Pink (Plan Theoretical Waterline is narrowest Yellow)

Waterline beam (approx using tru view): all boats Trans Frame 10 = 0mm

6C @Frame 8 = 600mm; @Frame 6 = 756mm; @Frame 4 = 595mm; @Frame 2 = 341mm

Dif = 103mm; Dif = 90mm; Dif = 67mm; Dif = 67mm;

6Y @Frame 8 = 497mm; @Frame 6 = 666mm; @Frame 4 = 528mm; @Frame 2 = 274mm

Dif = 50mm; Dif = 64mm; Dif = 87mm; Dif = 69mm;

6XC@Frame 8 = 447mm; @Frame 6 = 602mm; @Frame 4 = 441mm; @Frame 2 = 205mm

Over All Dif = 153mm; OA Dif = 154mm; OA Dif = 154mm; OA Dif = 136mm;

all boats Frame 0 (stem) = 0mm

Further explanation of the above from David, also regarding the Table Of Offsets for each hull design:

Difference between the theoretical waterline widths (The Red & Yellow ones) of each boat and the next biggest (hull design)

6C @Frame 8 = 600mm; @Frame 6 = 756mm; @Frame 4 = 595mm; @Frame 2 =341mm

Dif = 103mm; Dif = 90mm; Dif = 67mm; Dif = 67mm; this line is the comparison of width of waterlines between 6C & 6Y at each frame

6Y @Frame 8 = 497mm; @Frame 6 = 666mm; @Frame 4 = 528mm; @Frame 2 = 274mm

Dif = 50mm; Dif = 64mm; Dif = 87mm; Dif = 69mm; this line is the comparison of width of waterlines between 6Y & 6XC at each frame

6XC@Frame 8 = 447mm; @Frame 6 = 602mm; @Frame 4 = 441mm; @Frame 2 = 205mm

Over All Difference between the theoretical waterline widths (The Red & Yellow ones) of the biggest and the smallest

6C @Frame 8 = 600mm; @Frame 6 = 756mm; @Frame 4 = 595mm; @Frame 2 = 341mm

6XC@Frame 8 = 447mm; @Frame 6 = 602mm; @Frame 4 = 441mm; @Frame 2 = 205mm

OA Dif = 153mm; OA Dif = 154mm; OA Dif = 154mm; OA Dif = 136mm; this line is the comparison of width of waterlines between 6C & 6XC at each frame”

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Permission is granted for use of Hull designs 6X, 6XC, 6Y, 6YS and 6C by sailing classes other than the VJ as long as acknowledgement is made by the user by way of website or in print of the designer/design owner David Cleworth. Please contact Greg Fryer for the cost of plotting and shipping of full size design drawings.

David Cleworth and Greg Fryer would like to acknowledge the influence of previous hull designs and the work of several hull designers over the years; all of which have inspired the new VJ hull shapes 6C, 6YS/6Y and 6X:

Brendan Egan and Jim Walsh’s 12ft Skiff hull ‘Woof’
VJ hull designed by David Cleworth in 1994 used for the boats ‘Big Apple III’, ‘Big Apple IV’, and ‘Go Hard Or Go Home’
The designs of John Spencer, Bruce Hewish and Michael Nash in the 12ft Skiff and Cherub classes

Design gurus ‘hard at work’ during winter 2018:

Greg Fryer and Dave Cleworth

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2012-13 VJ Hull design:

On 10th November 2012 the VJ Amateur Sailing Association voted to adopt a new hull design along with other changes to the hull, rigging, main jib and spinnaker.

Discussions regarding the design changes happened over several months in 2012 with two experienced small boat designers: David Cleworth (from the Lane Cove Sydney 12′ Skiffs) and Marc Turner (from the Brisbane 12′ Skiffs). Marc is a former Lake Macquarie VJ sailor and still owns a fine Don McGregor plywood VJ.

The VJ ASA would like to thank both David Cleworth and Marc Turner for their valuable input.

In the end, the Association chose David Cleworth’s ‘Hull 6’ design as the new VJ hull, and were also very impressed by Marc Turner’s submission.

Permission is granted for use of Hull 6C design by sailing classes other than the VJ as long as acknowledgement is made by the user by way of website or in print of the designer and design owner. Please contact Greg Fryer for cost of plotting and shipping of full size design drawings.

Also featured below are Marc Turner’s hull and rig drawings. These are used with kind permission from Marc.