Tag Archives: kayak

Lightweight Kayak

Ultralight kayak on the beach at Alameda.
Ultralight kayak on the beach at Alameda.

My first kayak was a heavy rotomolded sit on top. I had a lot of fun with it, but it was heavy and slow. The decked canoe/outrigger sailing canoe I built is lighter and faster, but it is too long to haul around all the time and has a large cockpit that isn’t good for rough water. So I built this lightweight kayak for everyday use. It is 12′ long, 22″ wide, and weighs 24 lbs.

I designed the kayak using Hulls and AutoCAD. I printed out full sized patterns and traced them onto the panels. the kayak is symmetrical front to back so I cut out four identical half side panels at one time, and two identical half bottom panels and joined them together at the center. I used that crappy 1/8″ plywood from Home Depot again.

The hull is assembled using duct tape to temporarily hold it together.
The hull is assembled using duct tape to temporarily hold it together.

Once the side panels and bottom panel were epoxied together, the hull was ready to assemble. I temporarily taped everything together with duct tape, then filleted all the joints with thickened epoxy and covered the fillet with a strip of fiberglass.

The assembled hull after the tape has been removed.
The assembled hull after the tape has been removed.

Before the epoxy was set, the bulkheads were tacked in place and alignment was checked. Everything was allowed to cure overnight, and the next day the bulkheads were filleted and taped in place and the bulkheads and inside of the hull was sealed with epoxy. I also fiberglass the floor of the cockpit and a few inches up the sides to add strength in this area.

Fiberglassing the exterior of the hull.
Fiberglassing the exterior of the hull.

Once the inside of the hull was sealed, the kayak was turned over and the exterior of the hull was fiberglassed. I ran the fiberglass past the ends of the bow and stern, then trimmed it even with the plywood once the epoxy gelled. The next day I sanded the ends, then wrapped two strips of fiberglass over each end, covered with waxed paper, and clamped boards over the waxed paper. No more sanding on the bow and stern were needed – I hate sanding.

Installing the external sheer clamp.
Installing the external sheer clamp.

Next the external sheer clamp was installed with thickened epoxy. I used an external sheer clamp so the fiberglass on the deck could run over the sheer clamp and be trimmed even with its bottom edge. This way there was very little sanding required, and I hate sanding.

Attaching the deck.
Attaching the deck.

Next, the deck was attached. Since there wasn’t a deck beam the deck was not cut to shape – it was left rectangular so there would be a constant curve along the length of the deck. The deck would tend to have flat spots at the ends if this wasn’t done. The milk jugs full of water tied across the ends also helped to maintain the curve. The underside of the deck was sealed with epoxy, and it was bonded to the hull with thickened epoxy. It was temporarily tacked in place while the epoxy set.

The deck is trimmed even with the sheer clamps.
The deck is trimmed even with the sheer clamps.

After the epoxy cured the kayak was turned over and the deck was trimmed even with the sheer clamps with a hand saw. Then the kayak was turned right side up and the edge of the deck was rounded with a plane and rough sandpaper. The deck was fiberglassed.

Installing the cockpit coaming.
Installing the cockpit coaming.

Next the hatches and cockpit were cut out and the cockpit coaming was installed. The kayak was painted. The hatchcovers and deck lines were attached and kayak was ready to paddle.

Painted, Hatched, and Coamed.
Painted, Hatched, and Coamed.
Ready to paddle.
Ready to paddle.

Huck Finn Canoe Update

MRE Boat at Oroville Spillway

I’ve now had the chance to test the Huck Finn Canoe several times, and I was definitely wrong about the stability. The boat is very stable. In fact, when I tried to tip over to see if I could re-enter from the water, I had a hard time getting it to tip. One has to roll to about 80 degrees before it goes over – I think this is because of the high, flat sides.

I was also concerned about being able to get back in the boat after a wet exit, especially because of the deck height. This turned out not to be a problem either. The boat was practically dry inside when I turned it upright, and I was able to jump back in on the first try with no difficulty.

I also checked the speed of the boat with my GPS. If I paddle pretty hard I can reach 4.6 kts. Paddling at a leisurely pace I can maintain 3.5 kts. This was in flat water with a light breeze. We haven’t had much wind lately so I do not know how the wind will affect performance.

Continue reading

Huck Finn Canoe

MRE Boat Design

I’ve always wanted to do the Huck Finn thing and float down the Mississippi River. If I were smart I would fly to Minneapolis, buy a kayak, paddle to New Orleans, sell the kayak, and fly home. But let’s face it, I’m not that smart, so instead I ask myself what would Huck Finn do? Of course we know the answer – Huck would hang out on an island until a raft floated by, jump on, and be on his way. Since I live nowhere near the Mississippi River this will not work for me, and anyway it is doubtful that derelict rafts are still as plentiful on the Mississippi as they were in Huck’s day.

I like designing and building things, so I decided to try to design a boat that I could build in two days with indigenous materials sustainably sourced near the headwaters of the Mississippi (you know – Home Depot in Minneapolis) and a few hand tools. I failed miserably – it took me six days and $230 in materials to build the prototype – but it is actually a pretty nice boat. Continue reading

Progress on Micro-cruising Sailing Kayak

As usual with boat work, my progress has been slow. I thought I would be getting close to finished by this time, but I’m not even close. I have continued to tweak the design. I have moved the paddling position back into the pilothouse – decided shifting weight from position to position would not be practical. Had to redesign the pilothouse to accommodate paddling. I’m also working on the sailing rig – still not happy with it.

I’ve added bulkheads to the hull, front and rear decks, and framed the front hatch where my bike goes. I have built the pilothouse shell, but it is hideously ugly. I’m going to try to improve it, but function has to take precedence. I have to be able to paddle comfortably, so I may end up with one butt ugly boat. See the photos after the jump. Continue reading

I Start My Boat

First, I build a mold.

Assembling the Boat Mold

Next, I join together my EPS sheets. My boat is 12 feet long, but my EPS sheets are 8 feet long. Therefore I butt my sheets together and bond them with expanding polyurethane foam.

EPS Sheets Butted Together for Bonding
Panels are Bonded
Joint after Trimming

I designed the hull in Hulls, a free program for designing hulls. I then transfered the hull and panel layouts into AutoCAD where I completed the more detailed design drawings. The panel layouts were plotted full sized, glued to 1/8″ masonite, and patterns were cut from the masonite. I traced the panels to the EPS sheets from the patterns.

Tracing the Hull Panels

I cut the hull panels using a sharp steak knife.

Cutting the Hull Panels

The side panels are attached to the mold and bonded with expanding foam.

Side Panels are Attached to the Mold

Thickened epoxy is applied to the top edges of the  side panels (which are actually the bottom edges since the hull is being built upside down) and the bottom panel is bonded to the side panels. The jugs of water are used to bend the bottom panel to shape. Drywall screws temporarily hold the bottom panel in place while the epoxy sets.

The Bottom Panel is Attached the the Mold

Once the epoxy sets I shape the hull with a Surform and sanding block. The bottom panel is trimmed flush with the side panels, and all edges are given a slight radius so the fiberglass will drape over the hull properly.

Shaping the Hull - Stern

The photo below shows how much rocker the hull has.

Shaping the Hull - Bow

I also added a bit of V to the bow and stern.

Stern V
Bow V

The hull is ready for fiberglass. I used 4 layers of 6 oz cloth on the bottom and 3 layers on the sides. Getting all of that cloth to drape properly over the hull took 2 days.

Fiberglass is Draped Over the Hull
It Took 2 Days to Get the Fiberglass To Drape Nicely Over the Hull

It took another day to wet out the cloth with epoxy.

Wetting Out the Cloth
Wetting Out the Cloth Took Almost a Full Day

Three hot coats were needed to fill out the weave and get a glossy finish for sanding. The hull was then flipped over and the mold was removed.

The Hull is Flipped and the Mold is Removed

Here I am pouring some expanding foam into the bow.

Pouring Expanding foam in the Bow

Now I am ready to fiberglass the inside of the hull.

The Sailing Rig

The mast will be two piece fiberglass, with each half 5’6″ long. This allows it to fit through the pilothouse hatch to be stowed inside. The mast is stepped on the deck and supported by a compression strut to the bow and a shroud to each side. One piece or both pieces of the  mast can be used depending on conditions. In the sketch above the front view shows both mast sections and the full sail, while the side view shows one mast section and the top sail.

The sail rolls around the boom for reefing. The sail is a gaff sail with a very light gaff – more like a batten. The portion of the sail above the gaff will be attached to the mast with sliding collars. The lower portion will not be attached to the mast, but the luff will be reinforced so it can be tensioned. This will allow the lower portion to be reefed around the boom or raised from inside the pilothouse as there will be no need to deal with collars, sail slugs or a bolt rope. The portion of the sail above the gaff will be the storm sail and will rarely be rolled onto the boom. When the top sail is rolled onto the boom, it will unclip from the sliding collars as it rolls onto the boom. It will need to be manually clipped back in to the sliding collars when it is raised. The top sail is about 7 square feet. The total sail area is 34 square feet. Continue reading

Design Discussion Continued

The plan is to build the boat using 1″ thick EPS (expanded polystyrene) foam with fiberglass and epoxy on the inside and outside. The advantages are: EPS is easy to work with, the hull will have good impact resistance, the EPS will provide flotation, and it is lightweight. The disadvantage is I am having difficulty finding high density EPS. I’ve previously used EPS with a density of 4lbs. per cubic ft., but the suppliers I used are no longer in business. I’ve searched all over the SF Bay Area and the highest density EPS I can find is 2lbs. per cubic ft. For reference, Douglas fir is about 33 lbs. per cubic ft., and steel is about 490lbs. per cubic ft.

The problem with the low density EPS is it’s more difficult to shape, doesn’t allow as fine a finish, and doesn’t have good impact resistance. The fiberglass will delaminate from the EPS where there is high stress, and this will weaken the boat. So I really need to find high density EPS, and that is what is holding me up right now. Continue reading

Sailing Canoe Design Discussion

Here is some of the numerical data regarding my sailing canoe design: design displacement = 500lbs.; LOA = 146″; LWL = 134″; Beam = 32″; BWL = 32″; Center of buoyancy = 78″ from bow; Center of lateral area (hull only) = 75″ from bow; Lateral area = 3.32 sq. ft.; Prismatic coefficient = 0.56; Hull speed = 4.5 knots; Sail area = 36 sq. ft.

After studying the designs of other sailing canoes, kayaks, and small boats I’ve decided to build my sailing canoe with a flat bottom. The advantages are that it is easier to build, has good initial stability, and the sharp chine, or rail, will prevent side slip without the need for a keel or centerboard. The usual objections to a flat bottom are more wetted surface area, less strength than curved sections, and a rougher ride in choppy conditions. However, in this application I believe these objections are somewhat mitigated. With a flat bottom there is more usable interior space, so the boat can be shorter, reducing the wetted surface area (I want the boat to be short anyway so it will fit in the back of my pickup). Sure, a shorter boat has a lower ultimate hull speed, but this boat is for cruising around, getting some exercise, and having fun – it’s not a race boat. The bottom is only flat in regards to the longitudinal axis. There is significant rocker, so the bottom is curved along its length, adding strength. And because the hull is narrow, the bottom is buried six inches  in the water which will help produce a smoother ride. In addition, this is a low speed vessel so it will not be skimming across the surface of the water like a speedboat. Continue reading

My Sailing Canoe Design

SK1232 Sailing Canoe Sketch

I have been refining my sailing canoe design and this is my latest revision. I began by doing some concept sketches. This gave me an idea of the approximate size and proportions of the hull. I then used Carlson Design’s free Hulls software to optimize the hull shape. I went through probably two dozen hulls, each with minor variations in length, beam, rocker, and other variables.

I don’t have much boat design experience so I found the book ‘How to Design a Boat’ by John Teale to be very helpful. Between the book, Google, Wikipedia, and a few other resources I was able to figure out what the prismatic coefficient is, where to place the sail center of effort, and, most important, if the boat would float. Continue reading