Winter Storage: Shrinkwrap Engineering

Posted by Phillip Gutowski on

tayana 42 winter storage

While many boat owners are consumed with the annual task of hauling and storing their vessels for the winter, others are prepping for the cold months by turning theirs into a stationary den.  Here in the snowbound Northeast, most liveaboards cover their decks by erecting a temporary structure to be wrapped in heat shrinkable plastic sheeting.  This cover adds a layer of protection and comfort for the ship and her crew by helping to shed rain and snow, reduce condensation and provide passive solar heat during the day.  Albeit temporary, I’ve decided to build a seasonally reuseable structure that offers plentiful space to do the only thing I love more than sailing.  Boat work.  Here are the steps I took, from conception to the realization of a functional winter boat shop under the shrink wrapped shelter aboard our Tayana 42, Eclipse.

shrinkwrap from exterior of boat


Material choice

Galvanized electrical conduit is the most common choice for reusable shrinkwrap frames.  It’s a great choice and allows for very easy assembly.  It’s compact when broken down, and it’s quite strong.  I previously built a frame from metal conduit, but decided to rethink it this time around.  Wood is less expensive, faster to cut, doesn’t require bending and is lighter.


Roof pitch

The weight of the snow weighing on the frame could cause a collapse, so a proper pitch on the roof is necessary to allow it to slide off.  Too much of a peak however, makes the structure extremely difficult to cover in plastic since the peak is out of reach.  The angle at the peak of our structure is 30 degrees.  Stubborn snow can be persuaded from its perch with a banging action from the inside.

boat shrinkwrap roof

 

Elbow room

From previous experience, I knew that proper head room isn’t the only thing necessary to be functional on under the wrap.  Elbow and shoulder room is critical while walking along the side decks.


Ease of assembly

If you're going to reuse your frame, be sure to label all of the parts.  Each of our frames is designed to fold up upon the extraction of wingnuts and bolts from each plywood joint.

boat shrinkwrap frame wingnut assembly


Watertightness

Unstepping the mast was a critical part of making our frame easy to cover and completely watertight.  It was also critical for positioning the work bench over the mast pulpits.


Mistakes

Not accounting for any rise of the sheer both fore and aft was a critical oversight on my part.  When making my original CAD drawings, I designed all the frames on a flat plane.  In the end, everything worked out ok, but assembly was definitely more difficult.  The wood used for the fore and aft ridge elements did not line up appropriately and needed to be bent into place.



Design and Construction


Using CAD Software

I’m not formally trained in CAD software or in drafting.  However, modern computer drafting software has really lowered the bar for doing work like this.  I used OnShape (onshape.com), for its free web based CAD software.  It’s easy to learn how to use from the plethora of tutorials online.  To design the frame, I took an image of the deck profile of our boat and imported it into the design.  Then by stretching it lengthwise to its 42’ LOA I had a very close representation of her profile.  This served as the guide for the lines I drew to represent each frame.

boat shrinkwrap cad drawingboat shrinkwrap frame cad drawing

 

I also used the software to design the plywood frame joints which I paid to have cut at Artisans Asylum (artisansasylum.com), our local ‘maker space’.


Build a Workbench

We are very lucky to have stable mast pulpits on deck which, without a mast in place, would support a table.  The workbench was the first thing to be constructed and continues to be the pièce de résistance throughout the evolution of winter boat projects.

sailboat workbench

 

Create Construction Directions

I manually took the dimensions from the CAD drawings and created a spreadsheet with the lengths of the various timbers which would make up the frames.  I cut these accordingly.  Each of the frame legs was notched with a router so that they would sit securely over our slotted toerail.  I had created jigs for all notching and drilling which made production of the parts happen quickly.

boat shrinkwrap frame plans


Assemble

The more hands the better.

removing sailboat radar post

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