Saturday, June 11, 2011

Nesting Dingy Construction

The construction plans were for the CHAMELEON, a design by Danny Greene of Offshore Design Ltd in Bermuda.  (Offshore Design Ltd., PO Box GE 213, St. George's, Bermuda GEBX  Email:
It's a multi-purpose nesting dinghy ... and can be constructed with a sprit sailing rig and/or outriggers and rolling seat  and can be fit with a small outboard.  But the foredeck of  my Fuji 32 Ketch, VALHALLA, would not accomodate  the designed nested length of 5'4" so I did a linear reduction of the plans by 11% to get a nested length of  4'9".  This gave an overall length of 8 1/2 feet.   The sailing rig would also be too much gear to stow onboard so my project was for a basic rowing and motoring version.
The math involved with all of the plan dimensions, which are given in feet-inches-eighths, was easily handled by an Excel spreadsheet conversion of dimensions to metric equivalents, then the application of a percentage reduction.  The 11% reduction gave the desired final dimensions.  Here's a sample of the spreadsheet I used:
Dimension Conversion
Construction is a 'stitch and glue' (or 'tack and tape') project.  The selection of marine grade plywood in the southern Philippines isn't all that great so the best I could come up with was 3/16" thickness instead of the desired 1/4" ply.  So it was planned from the outset that glassing of surfaces inside and out would be required.

The layout and cutout  went smoothly and copper wire was used primarily for holding the pieces together while fillets and glass taping was done.
tack and tape

 The basic hull is shown below after filleting and taping.
 The next stage consisted  of fabricating and installing the bow locker, seats, and aft buoyancy tanks.

It was now time to separate the hulls by cutting between the mating bulkheads.

Fabrication continued with the installation of skegs, corner fillets and reinforcing for the outboard and rowlocks. Two coats of epoxy primer were sprayed using SCUBA tanks in lieu of an air compressor.
The nested package ready for launching.
A companion project was to fabricate a pair of 7 foot oars after the design of Pete Culler.  Here's the result:
Not able to wait for final painting I gave GECKO a trial row.
Though she rowed like a dream I discovered that the reduced freeboard placed the rowlocks too low ... my hands would touch my legs on the rowing downstroke.   The low freeboard also gave me some stability concerns ... something that Danny Greene cautioned against when I told him of my approach to this project.
The solution was to add some freeboard by adding a higher gunwale.  New mounts for the rowlocks gave the desired increased height.

With the gunwale completed it was time to determine the exact waterline before painting the outside.  An in-the-water test was done with some loading to simulate "normal" conditions.  The resulting mark from the dirty water in the boatyard was easily visible on the primed surface.


The 'topsides' were painted to match the topsides on VALHALLA and a vinyl rub rail affixed around the gunwale.  A coat of antifouling on the bottom completed the project.
Oh !  you wanted to see the finished product?  Then you must  click here.

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