Hull Design Primer
This is my personal opinion on some of the factors you should think about when designing your pdracer.
Build it NOW, modify it later
The number 1 thing that slows boat construction down, and robs sailors of good weather days, is indecision.
So many people are trying to get it right the first time, that they spend forever tinkering with their boat before the first time they put it in the water.
You can always tinker with the boat later, and even do major re-construction, but you can NEVER go back in time to sail on a good weather day or race that you missed.
So extreme is my opinion, that I even suggest: when the paint is dry on the outside of the hull (still bare plywood on the inside), put some oarlocks on her and go for a row.
Incredible feeling to be floating in a boat you built, can always row upwind and use an umbrella to sail back down wind.
The number 2 thing that slows boat construction, is waiting for someone else to form a fleet near you.
I get a lot of private emails from people telling me they are thinking about building, but there aren't any others near them, so they are going to wait.
Then about a month later I get another email from someone in the same town saying the same thing.
In this one city, I got 4 emails, each about a month apart from each other, each of them waiting for someone else to build a boat!
So build a boat and pass the word around locally!
Also consider having a boat building party, you can invite friends over, build a couple of boats and have a BBQ.
Emergency Floatation
The class rules require that you have positive floatation.
It isn't a matter of "IF", but a fact that "WHEN" you capsize or swamp your boat, you most probably will be alone and need to be able to self rescue.
A simple pair of end airboxes is enough, you can right your boat and bail the rest of the water out.
Without additional floatation, it is impossible to recover a boat by yourself in deep water.
See the Emergency Floatation page for more info.
Also don't be afraid of capsizing.
Would you be afraid of capsizing an air mattress in a pool?
If you have the proper floatation installed, it is about the same.
You should also test your floatation in shallow water, knock her over on purpose and recover her in the water.
Will build a lot of confidence.
Aux Propulsion
When sailing along, everything feels great, right up till the point when you break something and loose the ability to sail.
Your rudder can break off (most popular failing point), the mast can break, the leeboard can snap, or a number of other things.
A canoe or hand paddle will work, but they are very slow.
I have found the best solution is to carry a set of oars.
They are easy to use, and give you a good mechanical advantage when pulling in the oarlocks.
You can row a pdracer at 2.5 mph with an effort level that is very easy, making it possible to row for a long distance.
If you try to row fast, you will wear out your muscles fast.
The trick is to row slowly, so that you don't get tired, and therefore can go further.
Captain's Chair
The hull was designed to have the skipper in the stern, so he can look up at the sail and counter act the lever arm effect of the mast and sail.
The best place to sit in a pdracer changes with the wind conditions.
In light air, it is best to sit with your body centered about 30" from the stern, that will keep the boat level with both transoms out of the water.
The heavier the wind gets, the further aft you want to sit.
The lever action of the sail is felt most when going down wind.
One good trick is to face aft and lean over the stern.
That will keep the rudder in the water, and lift the bow up a bit to keep it from digging in.
Tiller Length
Since you sit so far aft, a shorter tiller works well, such as 16"-22" long.
You should probably make a slightly larger tiller than you think you need, and then cut it down as you gain experience with your boat.
Hiking Improves Speed
Having the ability to hike out (lean over the side) greatly increases speed.
You can hike from almost any of the hull configurations, all you need is something to tuck your toes under.
Some people attach a strap lengthwise in the cockpit to put their feet under, but something as simple as a 1" stringer down the side, or a bolt on seat work well.
Short Hulls & Digging The Bow
There are a lot of attractive features to a short board boat hull, such as a smaller hull to carry around and store, neat looking, less freeboard windage, theoretically less resistance when trying to sail upwind, easy to hike off the side, and it is easier to see how your boat is trimmed.
The compromise and negative aspect of a short hull is that you can dig the bow into the water fairly easy in 2 situations.
1 - Turning down wind -- As you turn to go down wind the mast acts like a big lever arm and tries to twist the hull forward and burys the bow.
This happens with all the hull configurations and sail plans.
If you have a tall 18" high hull, the bow transom becomes the entry point and you don't have to be as careful.
If you have a short 11" hull, and you aren't careful, the bow can easily go under water and you start to dig up water which really slows you down.
To counter this, when you make your turn, you should move as far aft as you can, possibly even turning backwards and leaning over the back of the boat.
You can have a large airbox or spray deck at the bow, like around 24", so that the water won't come into the cockpit as it comes over top of the bow.
2 - Digging in chop -- When out in big water with chop, you will be sailing over waves.
As you come down the back side of the wave, a short hull can easily dig into the rise of the next wave.
I have done this, was sailing along very fast and dove BucketEars completely underwater.
The boat stopped, popped up (did not capsize) and I was able to keep on sailing, even with a full cockpit of water since I had such large airboxes.
Don't let these problems prevent you from building a short hull, the same day I submarined mine, I had an awsome time sailing in 16+ mph winds in a protected area (the wind was coming over the shore).
You can see pictures on the Indianola Beach web page.
If you stick to protected waters, and be careful, a short hull is a lot of fun.
For more info on this subject, see [click here]
Gunnels & Side Stiffeners
Plywood is very flimsy when it is flat.
If you add a little curve to it, it becomes incredibly strong.
Because the PDRacer sides are flat, they will flex if you don't have enough structure to them.
If you build the simple end airbox version of the hull, you should consider adding a very strong gunnel, such as the one shown.
There is a 1.5" x 3/4" strip on the inside (it is black), and a 2nd one on the outside (bare wood) that was being added when the photo was taken.
Oil Canning (flexing) the bottom
While on the water, the force of you and everything the boat was built from presses on the bottom of the hull.
If you build a PDRacer with a wide open cockpit, the bottom will "oil can", or flex & curve upwards.
To prevent this, you should run atleast 3 skids down the bottom.
They add so much strength, that you could probably build with 1/8" door skin, and it still won't flex.
Look at the skin on frame kayaks, they use the same principle.
Most PDs seem to be built with either 1/4" or 3/8" bottoms, and the rest of the hull is from 1/4".
The 3/8" bottoms with 3 skids is very stiff and won't oil can at all.
The 1/4" bottoms with 3 skids will oil can a little bit, with 4 skids it won't oil can anymore.
The stringers, skids, and bulkheads are what makes the entire structure strong, not the thickness of the plywood.
Also you will notice that during construction, the hull will feel very flimsy, and be able to twist on it's long axis.
It feels that way right up till you get the decks on, then the hull stiffens up considerably.
Also, you should never sit in your boat while it is on land or not properly supported.
When the boat is floating, the bottom is sandwiched between your foot and the water.
On land or the trailer, the bottom is not fully supported and you will either stress or break your bottom.
Mast Placement
Most plywood boats with curved sides have a very limited range of area that you should place your mast.
Most of them use leeboards, which have to be placed at the maximum beam, and then the sail has to be balanced over that, which determines the placement of the mast.
The PDRacer has a huge advantage since it has flat sides.
You can put a leeboard almost anywhere on the side, therefore are not limited to where the mast goes.
For most single sail plans, having the mast 12"-24" aft of the bow seems to be an optimum place.
Also the mast step & partner should be atleast 12" high.
All of the force of the sail, hull, hiking effort etc is concentrated right at the top of the mast partner, so that must be a very strong point.
Rudder To Leeboard Distance
The further you can get between the leeboard and the rudder, the more control you will have, and better chance at preventing the sail from overpowering your controls.
(for more info, see the control problems article)
On #30, I made a very large bow deck and put the mast 24" from the bow transom.
This in turn moved the leeboard back another foot, so there is only 3' between the leeboard and the rudder.
I can still control it, but sometimes when the wind is really blowing, the sail will overpower the rudder and go where it wants to.
With 4' distance between the rudder and leeboard, there is a LOT more control from your fins.
Low VS High Aspect Sails
A low aspect sail is a short fat one, a high aspect sail is a tall skinny one.
The lower aspect sails seem to have better performance at the slower speeds, which is what the pdracer needs.
You should not have the sail go too far over the bow and stern though.
A stock sunfish sail has a 13'9" foot, and is very difficult to handle on a pdracer.
When tacking thru the wind, the boat gets stuck in irons and the sail acts like a big wind vane keeping it pointed dead into the wind.
Kickup Boards
The protected water that is most fun to sail these in, is often littered with shallow spots and underwater obstacles.
A kickup rudder is a must, without it you run the risk of breaking your gudgeons and pintles off and loosing the ability to steer.
You can get buy with a daggerboard that does not kickup, one technique is to have a hole in it so you can raise the board half way and put a pin in to keep it from going all the way down.
You can also sail without any keel at all, the side of the hull does provide some lateral resistance, but it slips a lot and won't make to weather very well.
Light Air Sailing
When in very light air, one technique that works well is to sit on the down wind side of the hull, and heel it over.
This makes the side of the hull grab the water better helping you move up wind, and also presents more of a V shape to the water, with less wetted surface area.
Heavy Weather
All boats with square bows share the same problem, they will pound in chop and are suddenly stopped, or slowed down.
The pdracer seems to do best in wind speeds between 5 and 12 mph.
After the average wind speed gets above 12, the chop rises to a point that it becomes more challenging to sail.
If you can find a spot where the wind will blow from over the shore, you can sail in much higher wind conditions and still have the flat water.
The pdracer will quickly get up to hull speed and even plane.
Be carefull, if you break something, you could find yourself paddling back upwind for a long haul.
Because the boats don't do so well in big water, it doesn't mean that you can't take interesting adventures.
There are plenty of neat places to go in protected waters.
Fancy Paint Job
Most of the other boats in the world are just one or two colors, some have a single stripe.
I think this is an attempt to keep them asthetically neutral, so they can be bought and sold more easily.
PDRacers are sort of like choppers, they are built by an owner for themselves, not as some resale object.
You don't want to be neutral, do you !?!?!
Give her a stunning paint job - something that nobody else on the planet has, something that people from miles around will be able to recognize and give her a disctintive personality.
Build it NOW, modify it later
Emergency Floatation
Aux Propulsion
Captain's Chair
Gunnels & Side Stiffeners
Oil Canning (flexing) the bottom
Heavy Weather
Fancy Paint Job