Offset Centerboard Trunk
By Paul Herting
I finally finished one of the two twin pdrs that I’m building. They couldn’t be finished simultaneously as I had originally planned as I didn’t have enough shop space so one is still in the assembly stage and the other is finished with the exception of spars, rudder and sail. For now it’s a rowboat or electric. My season here is quickly coming to an end, so I don’t know if I’ll get the sailing part completed in time.
The idea was to have both boats painted similar, one orange on white and the other yellow on white. I wanted the duck idea to show and since the two boats will eventually be used for teaching children to sail (ie: our local yacht club wants to do Saturday morning summer workshops), I wanted a paint scheme that would appeal to ten and twelve year olds.
The black "eye" on the side came from the Asian junks and sampans that are so cool. Also, I have an advantage in the paint design area since I'm a graphic designer and can draw everything up on computer, then print full scale templates.
At work I can print 11"X17" paper. I just break designs up onto multiple pages and then tape the pages together to form templates for stuff that I paint. 2M makes a spray that scrap bookers use to temporarily place paper. It's like post-it note glue. The problem with paper templates is that they get saturated pretty easily. So I often use them just for drawing pencil lines. For the actual masking when curves are involved I switch out blue painters tape for 3M water-proof bandage tape which is stretchy and can form nice curves. It's skin colored - Walmart stocks it. For really tight curves, you can slit the tape down the middle to make it half as wide.
Speaking of templates, here's something you might want to pass along. When I started the boats, the first thing I did was make a side out of 1/4 inch Hardboard. I eventually made hardboard templates of the other parts as well. The hope is that if I convince anyone else in my community to build a boat, I can loan them at least the side template and speed things along for others. This would be useful for making multiple boats. Since I have a woodshop for making furniture, I already had a router and a pattern making bit. The bit is basically a flush trim bit with the bearing on the top instead of the bottom. Either type could be used. The idea is to ruff cut a bunch of sides outside the lines, then stack them with the pattern on top (or the bottom if using a standard flush trim bit.). Clamp them and use double stick carpet tape to keep them in place then run the router over making sure the bearing doesn't slip between the pattern and a piece. The bearing follows the pattern and you end up with a bunch of identical side walls. This operation is best done by someone experienced in the use of routers which if not wrangled properly can wander with a mind of their own.
Here are a couple of shop pictures displaying my peculiar building method. The messy junk photo shows the bow module. I built the 1st mast box hole as a somewhat triangular unit, attached it to the bow, then attached that to the main bulkhead that also has a 2nd mast box. This forms a complete module. It makes attaching the sides, stern and airboxes much easier.
The other photo is an overhead to show the internal centerboard trunk and the back bulkhead which I installed so that I would have a place to put the battery for electric mode. The other innovative feature can be seen in the other pictures on the other email. The boat has a retractable motor mount that is normally hidden and flush with the deck. Having a centerboard is simply more convenient, though required a lot more planning and build time.
The oars on the other picts. are PVC with a dowel slid half way into them and they work fine. They were quick and easy to make.
One of the first students to learn to sail puddle ducks will be my daughter (age 10) as seen in the picture. She had a blast running the boat around with the little electric trolling motor. I was really impressed with how easily the hull shape moved through the water with only a 25lbs. thrust motor.
Now if I could only figure out how to cut down the chrome motor rod without also cutting the wires inside, I'd be able to store the motor on board and sail that way, leaving the large deck cluttering oars on shore.