Design Considerations Of The Puddle Duck Racer

All boats are compromises, there is no single boat that is perfect for all purposes. When picking a boat to build, you need to think of the end result of how it is to be used, and pick the characteristics which best meet those needs. Below are some of the factors which make this type of hull perfect to use for puddle ducking.



Easy To Build = Easy Get Friends Build Too

Sailing is great, I've been doing it all my life, and every time I launch a boat, I get that magical feeling. Sailing and racing with friends multiplies that magic up to an even higher level of fun. So... the easier it is to build a hull, the easier it is to get your friends to build them, and come racing with you.

The generic term for a PDRacer, is a "box boat", meaning that it has a rectangular perimeter. Of all the hull shapes that people use as boats, the box boat is the easiest one to build because it is literally just a box with a curved bottom.



Carry Lots of Weight

A Box boat hull is a scow shape, and scows carry more weight for their size, compared to other boat shapes. Easy to understand, because for it's length, it has the most hull area at the beam width, which displaces water, which adds to it's carrying capacity. In contrast, if you look at pointy boats, that narrow bow doesn't displace much water but does take up length.


Very Stable

They are very stable - as in it is very difficult to capsize one. So not only does that mean we can use very large sails, it also means beginning sailors will have an easier time sailing them because they feel less tippy. And if you are into fishing, you can literally stand up to cast.

Box boats are incredibly forgiving as to how you configure them. It is often said that PDRacers sail much better than they should. Many duckers simply take a guess at what "looks right" for size and placement of the components, and those guesses continually WORK just fine.



Fixed Hull Shape, Unlimited Sails

Most of the other sailboat classes seem to be split into 2 categories:

Our class fits in an area between those 2 general types. Our racing competition is largely about the skill of the skipper, but also we have the freedom to engineer parts to make our boats go faster. Because we all use a common hull shape and our boat is so small, that imposes a natural limit on the overall cost of our boats so our class will always be within the grasp of an amateur garage level competitor.


The advantages of small and slow

From a class perspective, it really doesn't matter how fast or slow a boat is because the point of a class is to have a common set of parameters and use those to compete with each other. Because of the social nature of competing with friends, it really is nice to have slow boats. Often we all stay very close to each other and are within talking range. Usually the furthest we get apart is still within shouting range, just think of all the fun distracting things you can call out to other duckers. :) If you really want to be funny, carry one of those cone loudspeakers that lifeguards use and/or a duck call that hunters use. Another great advantage, if we are about to collide with each other, it is easy to reach out and push off the other boat so we don't damage each other. Besides, no matter what sailboat you build, the Hydroptere is always going to be faster.



Light and small 8' -- instead of 12' or 14'

Once you discover the boat building hobby and how easy it is to make boats, and then you realize that no single boat will be perfect for every situation, you will become hopelessly addicted to building boats (just like me). Sounds fun and dandy, but after you build 3 or 4 other boats, before starting another project, you start to wonder where you are going to put them. And then it becomes an issue of which one do you want to let go, so you have room to build another.



Easy to store when not using her

The puddle duck is just short enough, that she can stand upright against the wall of a typical garage so when you want to work on the next boat, you can just put her there, out of the way. Then your garage floor is completely open so you can build another boat.

I know of one duck that has a shelf that sits inside the upright hull, so the space is still functional storage area!



Can cut from single sheet of plywood

Since plywood is typically 8 feet long, all the pieces to make a pdracer hull can come from single sheets of plywood. If you want to make a boat longer than 8 feet, you will need to splice together sheets of plywood for various parts including the bottom. Its not that hard to do, just very convenient not to, have to.



pdracer carried in minivan

Easy to transport

Hey, look at that, you can carry a puddle duck in the back of a minivan!






Or on top....






Do you have a pickup truck? You can carry two at a time!



piggy back carry sailboat




A puddle duck can easily be piggy back carried on other boats, even other puddle ducks.




Got a couple of kids, and want to race against them? This is a boat trailer that was converted to carry 3 puddle ducks. The max width for loads on USA highways is something like 8'6", so the puddle duck is just short enough to be carried sideways like this.



48" wide instead of narrow, 32" wide kayak

A skinny kayak type boat would have been easier to carry around and store, however a big concept of our club is that we are very social, go sailing with others (both in our boats, or in separate ones) and take our kids aboard. At 48" wide, the duck can easily carry 2 adults. For some builders, this will be their only boat, so being able to use as a recreational boat to take another passenger and teach their kids to sail, is an important factor.


Why the Puddle Duck Rocker is shaped like it is:

Max rocker closer to the stern

Water doesn't like to be moved, so the further aft you can put the maximum rocker, the more gradual of a water squishing effort you have. The water is going to get squished either way, but if you can do it more gently, it will cause less resistance, and be a faster hull. However you can't have the maximum rocker at the complete stern, because you have to curve back up and let the water go without dragging a transom corner across it. If you drag the transom corner, it will create vortexes and suck at the stern of the boat. This sucking force is so great, you can actually feel it: try rowing your pdracer around with even trim. Get a feel for how she rows, then have a passenger sit on the stern so it digs in, and row it around some more.


Look up at sail

Another advantage of having the max rocker further aft, is so you can look up at the sail. When racing, you look at the sail every 30 seconds or so to read the tell tales and the luff crinkles, to make sure you have laminar air flow. The further aft you can sit, the easier it is to look up.


6" Rocker Shape Depth

The more rocker you have, the more weight the boat can carry. The PDRacer's rocker shape is only 6" deep, which can carry a total of 630 lbs. That should be enough for the weight of 2 adults (or 1 adult and 2 kids), plus the weight of the boat (commonly around 125 lbs).


Types of rocker shapes

Generally speaking, there are 2 main types of boat hulls: Displacement hulls, and Planing hulls.

A displacement hull is like a typical sailboat. It is round shaped, and as you sail her a wave is created at the bow. The harder you push the hull, the bigger the wave gets, the longer it's trough extends. When the trough of the wave extends to the full length of the hull, that is called sailing at the hull's full displacement speed. One type of displacement hull shape tries to fit that wave, so as you sail inside of it, the water will match and flow evenly at that speed. After you reach displacement speed, the harder you push, the deeper the wave gets, and those shapes have a difficult time climbing above their bow waves.

A planning hull is shaped like a typical bass boat or jon boat, it has a curved entry and then a long flat run with an abrupt corner at the stern. The way a planning hull works is that as you apply power to the hull, it will create a bow wave just like the displacement hull. However when you apply more power, because of it's flat hull shape, it will rise up on top of the bow wave, and then start to skim on top of water, which is called planning. The compromise of planning hulls is that if you push it at speeds below planning, then the stern corner will drag in the water and create large amounts of resistance. This resistance is so great, that it actually takes more energy to push the hull at below planning speeds, than it does just after you have reached planning.

The Puddle Duck's rocker is a hybrid (semi-displacement or semi-planing) that borrows from both planning and displacement types. It has rounded ends so that it can move through the water at low speeds, but also has a long entry and flat-ish center section. To create this shape, I combined the bends of 2 battens. This compromise results in a hull that can travel at both displacement speeds, and climb up on a plane. In 2008, Kenny Giles was able to sail his duck at 9 mph (picture on mutton sail page) under wind power alone, which is more than double what the displacement speed of an 8' boat is.

I did not invent this type of hybrid shape, I first learned of it when researching boat design related to the Moth class, and am just one of many who uses the technique. Also before launching the pdracer class, I spent a year testing the rocker shape in my Flats Rat design.



Controversy of the PDRacer 2 batten bends

One of the great things about the boat building hobby, is that anyone can be a boat designer. There are some famous amateur designers like Noah, but also any native american that cut down a tree and scraped out a canoe technically becomes a "boat designer".

Get out some paper or load up your favorite CAD program, draw a boat. Buy some materials, build your hull, and presto you are a success. Some designers don't even do that, they just make plans and sell them. Of all the hundreds of amateur designed hulls I have seen and taken rides in, none were "bad", because sailboats are very easy to design, and almost anything will work. As for judging if a hull is to be considered "really good", is actually a perception on the part of the builder / owner, and how they feel the hull meets their needs (which may be different than the designer's intended purpose).

Because the Puddle Duck has an odd shaped rocker, a small controversy arose about the creation of it's shape. There is a belief floating around that all displacement hulls must be created in a way that their curve follows that of a single batten, if it is bent from the bow to the stern. The PDRacer is not a displacement hull, she has a hybrid rocker, created by combining the bends of 2 battens. Furthermore, it doesn't matter what the hull shape is -- the only important factor is that we all use the same hull shape, which has always been in rule 1 and explained further at the top of the class rules page.

For marking up plywood to cut the rocker, it is not an issue, just bend a batten around 3 or more station marks and make sure your pencil line crosses the 7 station marks at their proper dimensions. Or you can bend a single long batten around all the station marks at the same time and clamp them in place.

For CAD drafters that draw the rocker, it can be frustrating if they don't understand that the rocker is a hybrid shape because most try to draw it using a single arc spanning from bow to stern, and the computer typically will not draw it properly.