Introduction: Corky My First Sail Boat

Picture of Corky My First Sail Boat

This project comes from an 1950 edition of Boat Builder's Annual and can be found by googling CORKY.  Im not posting the plans but this is more of a build ibble and some suggested modifications.

The second picture was from the Brimfeild Flee Market the dealer wasn't shure what he had but was selling it for $40.00 and would let it go for $30 because I told him what is was.

The wood was free the paint leftover oops paint $5, box of wood screws $5, tarp $10 Poles $.44 and I found some shower curtain rings a tennant left in the basement and made two boats  The inter tubes were $7 and $8 from a local guy that sells them on the side of the road. Total for two boats about $38.


 

Step 1: Cutting the Wood

Picture of Cutting the Wood

I had several pieces of cabinet grade 3/4 plywood that was about 6 inches wide and five feet long.   I first cut 2 pecies per boat eight inches long. I figured out the bow(stern) point by finding the center on the 6inch side(top), then measuring up one inch from the bottom on the sides and placing a piece of 3/4 material on those points and drew a line on the oppsite side.  This is also the measurement for the width of the side walls (4 per boat) I also cut a bevel about 15 deg to line up with the bow.  The height of the sides depends on the intertubes used mine were about 7" for one and 9" for the other.  After they were cut I rounded the bottoms on a scroll saw and drilled counter sunk holes(pic 2) for some #8 wood screws

On two additional five foot boards at one end I lined up the one of the points I cut and traced it, drilled more holes using the piece as a template (I then screwed the sides on them and placed the intertube on the board to line up where the stern should be.  

    

Step 2: The Bow

Picture of The Bow

I used the two cut off pieces inside the bow to hold the mast.  Spacing for drilling the holes for the mast was simple.  After the top was screwed onto the sides I pushed the drill into the corner inside the bow as far as it would go and drilled straight down.  Same with the cut off pieces pushed them in and drilled them as close as i could get the drill.    

Step 3: The Stern

Picture of The Stern

This is where I would make the biggest changes.  The plans call for a closet pole to fit in a hole in the deck and the bottom plank of the boat.  After some thought (and a hole that was too tight) I would cut the rudder out of one (or two pieces) piece of plywood attached a 3 inch hinge to the rudder and the boat.  if you need to remove the rudder just take out the pin.

The present configuration also requires (has) about a 2 ft draft depending on the weight of the captain. 

There was a lot of fit, clamp, drill repeat for front and back.  

Step 4: The Rudder

Picture of The Rudder

The rudder is made out of a closed pole that was flattened on one side about 5 inches up with a 3/8 plywood board attached with brass machine screws.  I cut out a giant washer with a hole saw.  The large hole was cut first (3 inches) and then the disk held in with a nail and the smaller hole drilled.   The top of the pole was flattened on both sides and the handle was notched so the pole fit into the handle and held with a screw.  The bottom of the handle was rounded at the back so the handle could be lifted up.

Again i think this could be cut out of one piece of wood.  (or two so the handle would still move up and down)

Step 5: The Mast, Boom and Sail

Picture of The Mast, Boom and Sail

The mast is a long paint roller handle with an eye screw drilled threw it at the top for a halliard holder.   The mast was just held in by weight.  And a cleat on the deck that held the halliard (rope attached to the top of the sail)

The boom was a short broom handle with an eye screw at each end, one for the rope and the other that was zip tied to the mast.

The sail was the corner of a drop cloth cut off with the edges rolled and sewn.  The bottom hem was large enough for the boom to slid into.  On the side I cut small holes and attached the shower curtain rings.  (Planes, trains and Automobiles)

The rigging made it more like a real boat but I think the sail could have been more permanently attached, as raising or lowering or adjusting it while sailing would be impossible. 

Sorry I did not take a good picture of these parts


 

Step 6: All Together and Some Paint

Picture of All Together and Some Paint

After i got it all together I gave it a good coat of primer and paint.  I wasn't concerned with using plywood because i knew i would give it a good coat of paint.

I also added a piece of wood to the bow and stern.  I just thought I needed them to make the boat look finished.  you can see one of them is a little short.   

Paint flip paint and repeat.

Step 7: Testing in the Pool

Picture of Testing in the Pool

Found a volunteer (victim) to test the boat.  I also wanted to make sure my son could sail before i let him loose on the lake and he wound up on the other side.   

The instructions called for an old belt in front and back to hold the inter-tube I haven't add that yet.  my son was small enough that i don't think it mattered.  I'm a bit bigger and sink down lower resting on the main beam.  My but was pushing down and the tire was pushing up separating the two.  I was using bungees that went around the mast (rudder) and inter-tube but that was not working.

Step 8: Out on the Lake

Picture of Out on the Lake

The sail could have been bigger.  The lake here is in a bay and is only 1-2 ft deep until you get past the boats in the picture so the rudder kept dragging.  Having a smaller rudder on a hinge would have prevented this.  I also thought that a small 1-3 inch keel would have helped keep the boat sailing straighter.   Can't weight until next summer to try them again.

Comments

Stick and Rudder (author)2015-10-03

I built an adult-sized "super-Corky" or "corky-plus" a few years ago, by scaling up the original plan and using a truck inner tube. Made it into a picture in MAKE Magazine. I was attracted to the idea of a micro sailboat that you could transport in a car trunk. Sailed it for a season, then gave up. The two main things about the design that need work are: a triangular "Bermuda rig / Catboat" style sail is not very efficient: make a square sail or a gaff rig, to catch more air.

But whatever the shape, the sail is useless for anything except going straight downwind, UNLESS you add a SERIOUS keel or set of "bilge keels" to the underside of the chassis. The inner tube has a lot of drag and also "freeboard", that is, exposed side area, which the wind will catch. That pushes you downwind, no matter where you wanted to go. I would say, to simplify things a bit, add a tapered keel board the entire length of the bottom of the chassis, delete the rudder, and steer by dragging your feet or hands in the water.

The truck inner tubes were easy and cheap to get on Ebay. Inflating this with a portable mini 12 volt air compressor, operating off the car battery at lakeside, was ineffective, compared to a little workout with a stand-up bike pump. Even when full, the tube has such a low internal pressure it won’t register on my tire gauge.

The Corky-plus was just okay on the lake: she had so much windage from floating high in the water, it was sometimes more than the meager sail could overcome. It absolutely will only sail downwind unless you put a substantial keel on it. I tried two means for this: a full-length bilge keel sort of board that was cleated underneath the main board. This increased the minimum draft to the point that it was hard to jump off the lake bed and up into the tube to board the boat. My best method was to belly-flop onto it, then spin around to face upwards, very amusing to folks on shore.

The second variation was to cut a slit in the main “hull” board and slide an actual daggerboard down into the slot after launching. Unfortunately, considering the sidesaddle/egg-in-a-cup style of sitting in a Corky, every time I ran aground, the daggerboard found another slot on the other side to bump against… namely, my fundament. This was wholly unacceptable. Maybe hinged leeboards or retractible keels would be better.

My next step was going to be tandem truck tubes with a rudimentary platform deck on top, more effective daggerboards and the lateen sail rig from a Sunfish or Snark. You need massive sail area to overcome the other dragging forces on this design. This thing is very draggy in the water, no matter what you try to do, sails more like a piece of the dock that broke off and floated away from shore:-)

If you still plan to build one anyway, I suggest using the absolute lightest and least wood you can, or to try it with PVC pipe for the unifying crutch substructure. And that you launch on a lee shore, unless you have a recovery crew on stand-by to tow you back in.

After a few years of thinking about it, off and on, it might be better to make a boat-shaped exterior frame (copying the simple outline of a cardboard, quart-sized milk container, as the general shape) without a deck or hull, just an outline shape to contain the inner tube or tubes, mount the mast, and streamline it. Then you can attach removable bilge-board keels to the sides of that frame, and get performance to sail cross-wind. The fame could be made collapsible, so the whole "boat still would fit in a mid-sized car trunk and/or carry the frame pieces on a roof rack.

Best of luck; it's a cheap, fun project, no matter how you make it.

macrumpton (author)2012-01-06

I remember seeing plans for this years ago, and I had some thoughts on helping the performance a little.

My first thought is that the drag of pushing the inner tube through the water is pretty bad, so I was thinking you could bend the inner tube so the front and rear end are lifted up and the sides are pushed down, so the tube is formed into a short catamaran. The way to accomplish this is to have two sturdy poles (broomsticks or larger) arranged in a cross, with the bottom pole running lengthwise under the tube and the top pole running crosswise over the top, and the two secured together with rope, or possibly even just weaving the top pole under the bottom one.


My other unrelated idea is to create a bottom for the boat (to give it more floatation and sit higher in the water) by cutting a plywood circle that fits under the tube, so the plywood straddles the lowest part of the tube. When the plywood is secured with duct tape, and a giant shower cap with a drawstring to fit over the tube and plywood keeps the water on the outside.

It may be that both of these are too much trouble to make for a small improvement, but I thought you might find them amusing.

turbobug (author)macrumpton2012-01-12

For a 40lb kid the design is ok. For me i needed more sail. And a rudder would have helped greatly. One of two design changes would be to cut the bottom out as a doughnut the size of the tire with the hole cut out so my weight is not pushing down on the board and the water is pushing up on the tire trying to seperate the two. Also the rudder would be attached to the back with some kind of barrel hindge.

indianabob (author)2011-11-20

i found the corky site,, the print is not readable,, and zooming in doesnt help,,anyone have a good copy,,, id love to make one

DA TROLL (author)2011-07-28

I made one of these a few years back for my grandson. Didn't move very fast, (coulda' used a slightly bigger sail with better fabric) but he loved it. I'll make another one later for my newest grandson, but will incorporate a few light-weight changes and extend the size of the boat with bigger sail. (Maybe make a two-seater with twin sails??) My grandson used his to try to pick up girls (at age 5)!! Ha!

turbobug (author)DA TROLL2011-08-18

In addition to a larger sail made with pvc mast I would put a keel on the bottom and attach the rudder to the back with a three inch hinge and removable pin.

tdem (author)2011-03-03

How would you describe the sailing performance? Were you able to sail on a reach?

tdem (author)2011-03-02

Wow, great job! I've wanted to make one of these for years now. Can't believe you found one at a flee market! Did you try that one out?

turbobug (author)tdem2011-03-02

I sailed mine. He wanted $30 for it. Too much for me. It was well made and the paint was still in good condition. It looked hardly used.

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