Diesel Duck 382

Diesel Duck 382
Diesel Duck 382 with the "get home" steadying sails up.

The Boat Shed

UPDATED 10/18/17 Follow this LINK to see our new roof.  The rest of this post is still applicable but if you plan to do something similar, visqueen just does not last unless your structure will really be protected from the sun and wind.  My opinion of course, but we'll see how the new roof holds up.

A place to build might be the most important thing to consider when planning a large boat build.  If you live in a traditional neighborhood, space is going to be a consideration.  Not only might you not have the space to build, but even if you do, how do you get it off the property when it's done?

Assuming you have the space on your own property or rented from someone else what's the plan to protect your project?  For some a "blue sky build" is sufficient with maybe a couple of tarps for a little protection.  For the lucky few maybe a large conditioned space with utilities.  For those in between a large "temporary" structure may be in order.  

The bow roof shed is a popular option that affords durability, low cost and lots of head room.  I found a few designs with the most popular being the Stimson bow roof shed/greenhouse plan and a similar design from Shamrock aquaponics.

There are lots of posts on this site from 2016 that thoroughly document the building process but I'll touch on the highlights here for the ease of the reader.  I went with Shamrock for a couple of reasons.  First of all I had trouble getting in contact with Stimson Marine to get more information.  Secondly, after researching the shamrock design, I appreciated the fact that the plans came with engineered drawings that you could use with permitting if required in your municipality.  Additionally, Shamrock's plan were actually reviewed by the engineer and were rated for winds in excess of 160mph.  I would not want to put this to the test but my building survived a rogue 81mph windstorm that ripped through upstate NY in the spring of 2017.  It not only survived but did not suffer any damage when nearby agricultural buildings were destroyed.

Stimson's design is a little simpler as the shamrock design involves cutting 2x4's into strips then laminating them back together as they are bent on edge around a jig you will need to build.  Neither is that complicated and I felt the Shamrock design was more durable and recyclable. It seems it would be quite easy to either convert the shamrock design into a permanent structure with the addition of a more permanent roof or disassembling the structure and selling off the arched trusses when your build is complete.

After deciding on the design the next step before construction was site prep.  I hired a local pool builder to clear an area on my property with his bobcat.  After he leveled it out I then added commercial landscape fabric and had a dump truck of 15 tons of #1 washed stone dumped.  The bobcat operator then came back and roughly spread out the stone.  The final leveling was done by shovel and it was not fun!

We then dug 16 holes around 24 to 30" deep for the 4x4 pressure treated posts that would make up the knee wall.  The four corner posts were buried in concrete with rebar drilled through each post perpendicular to each other.  one piece of rebar was added to all the other posts at the bottom and they were buried in just dirt.  We then used some very inexpensive lasers to mark the appropriate height on each post and cut them so they were all level and plumb. The knee wall posts were sheated in 3/8" plywood giving us a nearly 2' tall wall.  Since I planned to frame and sheath the end walls I also built a base for the end walls made of pressure treated 2x4's and concrete deck blocks.

Next up was constructing the jig that would be used to create the arched trusses.  The instructions are thorough and explain this process but essentially you stretch a tape measure the prescribed distance and strike an arc with your pencil on some sheets of plywood.  After striking several arcs you make the appropriate cuts and then attach the sections of the jig together.  In order to determine the appropriate angle for the ridge and the sill you'll need a bit more space.  Now I'm sure there is some mathematical way to do this an easier way but for people like me this seemed the most fool proof way.  By creating a large right angle grid in the drive way with some concrete nails and string, I laid the rough jig on the string and made the appropriate marks on the jig where it met the strings.

With the jig complete I went to work on cutting the strips of 2x4's and blocks from my large pile of lumber I had delivered.  This was quite a bit of work and will require a few hours at the table and band saw.

With all the materials ready it was time for assembly.  This involved a few weekends of work to build all 32 arches required for the size of the building I wanted.  It's not hard work but it is time consuming.  The process is the same over and over as we bent two layers of strips around the jig, added the appropriate blocking and then two more layers of strips with Titebond III between each layer and the blocking.  This assembly is then clamped around the jig with large C-clamps (harbor freight is your friend here) and then the entire arch is pneumatically nailed, stapled and screwed in the appropriate locations.  We then used the angles we determined on the driveway on the jig and transferred them to the completed arches.  The lines were cut with a circular saw and the entire assembly was removed from the jig and process began again.

Once the arches were all complete we moved on to the actual assembly of the building.  I found it necessary to build some scaffolding as the peak of my building was almost 16' in the air.  The scaffolding allowed us to work safely at these heights and made it possible to add temporary braces to assist with setting the ridge board.  Some black pipe and associated fittings made a simple and sturdy railing.

If you really need the details on building I would encourage you to check out the posts from October, November and December of 2016.  However the short version is a relatively simple process of laying arches against the ridge board and attaching them with joist hangars.  The sill end of the arches is then attached with hurricane straps and 2x4 blocking.

It's definitely easier with 3 people but the assembly process can be done with two.  As we attached the arches moving down the knee wall, we added purlins between the arches to stiffen things up.  We also used plywood collar ties that were glued and stapled to each pair of arches.

There is another time lapse video on our YouTube channel which you can find HERE. At this point you could cover the entire structure in visqueen and call it a day.  I wanted something a little more durable for the wind conditions I was expecting on this part of my property.  I added end walls that were sheathed with plywood.  Nothing fancy here just normal 16" on center framing.

I felt that the end walls were not stiff enough so I added some diagonal bracing that extended from each end wall to the ridge beam.  This was very effective coupled with the other diagonal bracing that connected each arch.

With the structure complete the last step was to cover everything with 6mil visqueen.  Our first attempt using plastic that was seamed together by myself with what I thought was the appropriate tape failed.  On our second try I used a piece of visqueen that was made at the required 40' width at the factory and it has held up well.  The plastic is draped over the structure and attached to the knee walls and end walls with battens rolled up into the plastic.  The battens were then through bolted with 5/16" galvanized bolts and screws.

These are the highlights, and like I've said, there are additional details in some of the previous blog entries from 2016.  This was a big project in and of itself but I found it quite enjoyable.  I think the effort was worth it as I now have a place to not only keep our build safe but all of our lumber and tools dry and protected.


  1. Even without a ship in the planning, your shed is an inspiration.

  2. I am thinking of building more permanent bow roof shop on a concrete slab. Thinking roof would be sheathed and maybe shingled so a lot heavier.
    Suggestions for beefing up the bows to carry that load? All suggestions appreciated. Thanks, reply to alsgonefishing2000@yahoo.com

  3. Curious if your bows on 2 foot centers or on 4 foot centers?