kayak design

Kayak Design is the process of designing a kayak for a specific application (e.g. Touring kayaks, Fishing kayaks, etc.), and other parameters such as the user’s size, proficiency in paddling, the overall load capacity required from the kayak, speed, stability, etc.
Other kayak design factors are materials (e.g. Polyethylene resin, fiberglass, etc.), manufacturing technology (e.g. rotational molding, thermo forming, cold molding, etc.).

Kayak design is a term also used to refer to the kayak’s form (type), such as sit-in, sit-on-top (SOT), hybrid and twin-hull kayaks.

Cap’n Larry Jarboe: The Boat That Does It All

Quite a few years ago, back in the mid-1970’s, I was fortunate to work as a mate then captain of a large passenger carrying boat that took people snorkeling on the shallow coral reefs of John Pennekamp State Park in Key Largo, Florida.

I promoted our business with the phrase “If you can swim, you can snorkel.” Twice a day, we hauled up to 61 passengers a trip on a wooden Harkers Island-built boat to witness the amazing coral reefs and tropical fish that are found right here in the United States.

Today, the State Park concession that I worked from has about 4 multi-passenger snorkel boats that have evolved from that one vessel.

Like snorkeling, there are many marine sports that have sprouted over my lifetime.

Obviously, canoes have been with us for many years. But, who figured out that you could sit on top of a kayak or stand up to paddle a fat surfboard? These are relatively recent innovations that have attracted a huge following.

Then, there are those Wave Runners. When I grew up in the Fifties, we never figured you could have a motorcycle that flew across the water.

All of those sports are fun for those of us who swim but owning all four: a canoe, kayak, paddle board and Wave Runner is expensive, space consuming, and a major maintenance hassle.

What if one vessel did all this, and more?

The Wavewalk catamaran style skiff is the stable and portable boat that literally, does it all. A visit to the company website at wavewalk.com will show you the W500 and W700 solo and tandem twin hull kayaks that are easy on your back because they are straddled like a Wave Runner. Fishermen are especially fond of the Wavewalk design because they are so easy to stand up in order to spot or cast to their prey.

These magic boats can be paddled with kayak or canoe paddles or outfitted for gas outboard or electric trolling motor or both! And, they are lightweight enough to carry on top of your car without a special carrying rack or trailer.

I discovered the Wavewalk design while I was searching the Internet for the perfect kayak to establish a retirement rental business in Key Largo. My first Wavewalk was purchased at retail price. That little W500 was so good that I used it in my commercial fishing business in the Chesapeake region to supply Blue Catfish fillets to Linda’s Cafe in downtown Lexington Park and the Victorian Candle Bed and Breakfast in historic Hollywood, Maryland.

At present, in addition to two commercial fishing work boats, I have a fleet of Wavewalk kayaks for weekend Wavewalk Adventures in the State Parks and National Sanctuaries that surround Key Largo.

And, I am fortunate to be the exclusive Wavewalk distributor for all of South Florida. Contact me if you are in the Chesapeake region and I can arrange for you to have your own Wavewalk kayak.

On a nearly daily basis, I motor my green W700 skiff through mangrove creeks or out in the ocean to make my own adventures exploring places that are almost impossible to reach by any other method of marine conveyance. This Wavewalk lifestyle is a most wonderful and unexpected retirement pastime that I am most happy to share.

So, if you are tired of being cold this winter and want an excuse to visit the Florida Keys, you have one (as if you really need an excuse to visit paradise).

A trip to my website at floridafishingkayaks.com. will provide all the info you need to schedule a free Wavewalk Wednesday demo of this vessel. Or, a weekend rental with included guide service might be a way to enjoy a complete kayak, canoe, stand-up paddle board package in a boat that “does it all.”

Who knows? You might drive home with one.

Welcome aboard.

Cap’n Larry Jarboe

 

 

More fishing adventures with Capn’ Larry »

 

Wavewalk S4 update

Our mold makers sent us these two new pictures of the first (lower) half of the rubber pattern (developed from the initial wooden pattern) that will serve to create the Sand mold.
The rim and vertical columns added will serve to bolt together the top part of the mold to the bottom part each time our molders make an S4.

Producing cast aluminum rotational molds of this size is a lengthy (and expensive…) process.

And for those of our readers who have already ordered an S4: Our mold makers also confirmed that we’re on schedule  🙂

 

 

Testing 15″ short (S) shaft outboard motor performance with Wavewalk kayaks and boats

This article summarizes the research that Captain Larry Jarboe, of Florida Fishing Kayaks and Boats in Key Largo, Florida did on this subject, and we are very grateful to him for this exceptional contribution.

Background –

 

Larry’s main goal in conducting this series of experiments that lasted for several weeks was to find the “sweet spot” for 15″ (S) outboards, namely a setup that would enable him to successfully outfit W500 and W700 boats with such motors, which are typically cheaper and easier to come by than 20″ (L) motors.
His secondary goal in running these extensive tests was to check the performance of Wavewalk’s TMM 700 HD motor mount, and see if we could improve it.

Larry is a passionate fisherman, mechanic, and seaman. He works as a commercial fisherman and fishing guide, and he is Wavewalk’s distributor in Southern Florida.
For the past fifty years, Larry has been involved in using, building, refurbishing and testing motors in various land and water vehicles, including electric racing cars, regular cars and trucks, a wide range of small watercraft, and big diesel engines in stern-drive commercial fishing boats, such as he still operates in Key Largo.

Means and Method –

 

In his tests Larry used five portable outboard gas motors that he had refurbished and tuned himself. Some of the motors had 15″ short shafts, and the others had 20″ long ones, and their horsepower rating ranged from 2 HP to 5 HP. He also tested a couple of electric trolling motors.

Larry conducted his experiments systematically – Being a handyman as well as a mechanic, he built a series of transom motors mounts that enabled him to mount outboard motors of both sizes in various places at the boats’ stern.
In his tests, he changed the height of the mounting plate, and/or its distance from the cockpit’s rear end.

Results –

 

There is no “sweet spot” for mounting a 15″ short (S) shaft motor on a Wavewalk, and any configuration involving the use of such size motor would inevitably result in sub-optimal performance compared to the use of a 20″ long (L) shaft outboard motor of the same power.

The main problems that Larry found with 15″ short (S) shaft outboard were the following:

Ventilation

 

Outboard manufacturers recommend mounting outboard motors with their anti ventilation plate (sometimes called “anti-cavitation” plate) immersed a couple of inches below the boat’s lowest point, which by definition is always immersed. This inevitably means that the anti ventilation plate is several inches below the surface. If the propeller rotates with its blades too close to the surface, it sucks air from the surface, and instead of rotating in water it rotates in a mixture of water and air bubbles. As a result, the propeller loses efficiency and power.

  1. At higher speed – Larry found that with 15″ short (S) motors, ventilation started to occur at about 5 mph, when the boat was transitioning from a displacement mode into a semi-planing mode, and its hulls were slightly raised, thus pulling the propeller upward and too close to the surface. The higher the speed the more extensive the ventilation and power loss. No ventilation occurs with 20″ long (L) shafts, even at speeds higher than 12 knots (13 mph), when the boat is in a full planing mode.
  2. When making sharp turns – Larry found that the 15″ short (S) motors’ propellers sucked air from the surface while he was making sharp turns. This happened since the boats tilted on their side, and the propellers got too close to the surface. In this case, ventilation resulted in loss of power as well as loss of control, to some extent, which made turning more difficult. Such problem did not occur with 20″ long (L) shaft motor, which performed flawlessly in sharp turns at high speed.

Splashing and discomfort

Splashing – In order to avoid ventilation, it is possible to mount 15″ short (S) shaft outboards at a lower level, with its propeller immersed more deeply. This can be done when a specially designed motor mount is placed several inches behind the cockpit’s rear end. However, at such position, the lower part of the motor mount’s vertical mounting plate is too low and too close to the surface of the water, and it will come in contact with the water. In such cases, the result is spray splashing over the motor’s head and into the cockpit’s rear end. No such problems occur with 20″ long (L) shaft outboard motors when mounted correctly on a standard Wavewalk motor mount.

Discomfort – When the 15″ short (S) outboard is mounted several inches behind the cockpit’s rear end, it is harder for the user to reach the motor and its controls (e.g. choke knob, starter grip), and it is harder for them to steer. This is not the case with 20″ long (L) motors that are mounted at the rear of the cockpit.

Bottom line

 

There is no “sweet spot” setup that allows for mounting a 15″ short (S) shaft outboard on a Wavewalk (500 or 700) without it incurring serious drop in performance. The way to motorize a Wavewalk is to follow the recommendations of outboard manufacturers about mounting their motors, as well as Wavewalk’s recommendations that fully coincide with them, namely to use only 20″ long (L) outboard motors with Wavewalk’s kayaks and boats.

 

A sweet spot, sort of…

 

When Larry checked 15″ short shaft, weak electric motors, he found that the ventilation problem at higher speed didn’t occur, because such motors lack the power to propel a kayak at speeds that are high enough to make it reach a semi-planing mode, or have the propeller suck in air from the surface. Knowing about such a sub-optimal performance envelope, the user already expects sub-optimal performance. This said, this rule is not ironclad, and ventilation may still occur in case the boat makes a sharp turn.even when it is propelled by such weak 15″ short electric motors, and while going at low speeds.

This is to say that Wavewalk recommends not to use short shaft motors even in the case of weak electric trolling motors.

In sum, the only propeller shaft size that we recommend for all types of motors is 20″ long (L)

 

More reading:  How to measure an outboard motor’s propeller shaft length? »

 

 

 

 

Wavewalk S4 pattern pretty much done

This morning the mold makers sent us a batch of new photos. This time it’s the top part of the S4 wooden pattern.

Some of the areas that have fine details in them were done with a plastic material, in order to achieve the highest precision.

As seen here, this wooden pattern is almost ready to serve as a mold for making the S4 in fiber-reinforced plastic (FRP), such as fiberglass, carbon fiber, Kevlar, etc. But in order to produce a cast aluminum rotational mold for the actual product, the mold-makers first need to use this wooden pattern to produce a set of two second generation molds called ‘sand mold’.

 

In the actual Polyethylene boat, the flat surface on top of the cockpit is cut away with a computerized router, thus enabling access inside through the opening, and attaching the two MDO saddle brackets and the saddle itself.

Stand up casting platform with integrated anti-skid surface. The slots are vertical structures that support the platform’s center.

Front tip and integrated carry handles. Good view of the slanted sides of the cockpit, designed to offer passengers comfortable paddling.

Front view.

Rear view with integrated carry handles and integrated stand for mounting plate for motor, rod rack, etc.

Side view.

Close-up on the slide-in mount for a vertical plate that can serve either to attach a motor, or to install a rod rack. If it serves to mount a motor, the vertical plate should be bolted to the cockpit’s rear end.

Measuring an outboard motor’s propeller shaft length

Some of our clients who already own an old outboard motor, and others who contemplate buying a used one, ask us how to measure the length of an outboard motor’s propeller shaft, in order to know for sure that the motor indeed complies with the 20″ long (L) standard that Wavewalk requires.
This is an important question, because Wavewalk kayaks and boats work well only with outboard motors that comply with the 20″ long (L) standard set by outboard motor manufacturers, and our company strongly recommends not to use short shaft (S) standard motors.

Here is the full answer:
For this matter, the propeller shaft length is measured from the inner top side of the motor’s mounting bracket to the horizontal anti-ventilation plate that’s above the propeller.

Note that sometimes the anti-ventilation plate is called anti cavitation plate, although this is an incorrect term.

In many cases, this distance between the inner side of the motor’s mounting bracket and its anti ventilation plate can be slightly bigger than 20 inches, and if this is the case, it’s a good thing.

If the distance you measured is under 20″, it inevitably means that the motor does not comply with the 20″ (L) standard.
In fact, most outboard propeller shafts are slightly longer than their stated standard. For example, the length of a 2.3 HP Honda L is 22.5″, and the length of this motor’s short (S) version is 16.5″. Similarly, the length of a short-shaft (S) 4 HP, 5HP and 6 HP Tohatsu is 17.1″.

But don’t fool yourself –  16″, 17″ and 18″ is not 20″, and it’s still a short-shaft (S) outboard, and it won’t serve your purpose.

Why is this so important?

The reason the outboard’s propeller shaft’s length is so important is that it determines both the propeller’s immersion below the surface, which is critical to its proper functioning, and the distance between the propeller’s highest point and the boat’s lowest point, which is critical for trouble-free and effective operation of the boat.

Please avoid using short shaft (S) outboard motors with your Wavewalk 500, Wavewalk 700, and Wavewalk Series 4.