ER PLAN

Just before leaving on our recent road trip (4,500km), I wrote a post about a planing hull version of my popular Flint design. I was quite excited about the concept of a planing skiff for low-powered outboard, having had it in the back of my mind for a very long time.


With this latest design, (see here for details in the previous post), I had to produce the basic drawings in a very short space of time (about three days), as we were about to leave on what turned out to be more than four weeks of road travel. Having given thought to such a design in the past, I felt that I could get enough detail out to satisfy the owner/builder, who is an exceptionally capable person with high-level engineering qualifications.

Stitching-up Flint on which the new design is based

Here you can see the complex shapes which can be formed in plywood, as long as the panel shapes are "developable".

In order to produce a design which can be built stitch-and-glue from pre-computed plywood panels, one has to resort to relatively complex geometrical drawing. In the past, the drafting methods used to develop the panels tended to result in hulls which were full up forard and had straight buttock lines aft. The hulls so drawn are frequently apple-cheeked at the bow and lack displacement aft - not a good shape.

With the availability of complex hull modelling software, it is quite practical these days to engage in the design of developable hulls which were never possible in the past because of the unbelievable volume of calculation required in manual drafting. I am not a computer person, but I love my hull modelling and CAD software!

In my extreme rush to get drawings to the builder before leaving on our trip, I burnt the midnight oil fairing-up the hull shape on the computer, and when all was satisfactory, I hit the button to produce the panel developments.

Panel developments for one of my other designs

Off I went on four weeks of road travel, confident that the information provided would be adequate for my talented customer. The trouble is that in my confident state-of-mind I had neglected to test the developments as I usually do, using a scale model.

Scale model panel developments for Three Brothers, cut from 1/16" plywood

Testing panel developments at small scale

On the day of my return from the first of two long road trips conducted over the last four weeks, I received an email from my customer to say that he had cut all the panels for the planing hull version of of Flint (named Fleet) using his own CNC equipment (!), and that he was having problems with the initial stitching process. He was of the opinion that he was doing something wrong, having never built a stitch-and-glue boat, but I had a more sinister suspicion!

For a long time, Ive had a feeling that some hull modelling programs have a hard time doing developments which incorporate large amounts of twist and bend at the same time. When one considers the unbelievable number of calculations required, and the geometrical complication, it is little wonder. In order to test my supposition, I reverse-engineered the offsets of Fleet into Gregg Carlsons "Hull Designer" program, which had proven itself to be very accurate at this sort of job in the past.

I generated a set of developments using the Carlson Hull Designer, and superimposed them over the ones I had generated from the other program. In the illustration below, you can see the Carlson developments in red, overlying the others in a dark colour. The topside panels are virtually identical, but the bottom panels show substantial difference.

Fleet developments showing the originals in black, and the Carlson Hull Designer developments in red.

As you can see, there was enough difference between the two different bottom panel developments to produce serious problems. So, my customer had not caused the problem - it was caused by my over-confidence, haste, and lack of testing! Below are some photos showing the result...

Bottom panel having failed in tension at the keel-line near the first frame (near the bow)

View of the failure from the inside. See how the crack has initiated at the keel line, and extended upwards and outwards from the keel line.

Having wiped the egg from my face, and being confident that the new developments would solve the problem in subsequent boats (but I will be doing tests this time!), the problem remained about how to fix the first boat without having to scrap the entire pair of bottom panels. The suggestion I made was along the lines of, "if you cant beat them, join them". I recommended to the customer (luckily for me he is a very clever and resourseful chap) that he use a saw to cut a whole series of of similar "failures" across the keel line both forward and aft of the initial failure, so that the topside panels could pull the incorrectly shaped bottom panels into the proper position. This was done, and with each successive cut the original failure closed up a little more, and an even bend formed in the keel line.

Here you can see some of the deliberately cut lines, filled with thickened epoxy and finished off with a "stop drill" at the upper end.The dark line closest to the camera is a scarph joint, but you can see the artificial "failure" cuts filled with white thickened epoxy forward of the scarph.

Glass tapes dry-fitted, with some extra tapes to reinforce the new cuts

A wider view, showing how the repair has restored the boat to a nice, fair shape.

There are a number of lessons from this project: -

• I should not assume that drawings for a new design are correct without testing them;
• Never give up, because just about anything can be fixed if you do some careful thinking;
• Dont take what I say too seriously, as Ive proved myself to be wrong on frequent occasions!!!

Boat building  and designing is a lot of fun, and I really look forward to seeing how this particular boat turns out. I believe that there is a genuine need for an outboard-powered skiff which can perform well with a low-powered motor - say 4hp - and still be spirited and lively.

Why would anyone build a boat? What kind of question is that for a boat designer to ask? I ask it because there are so many people who ask it in all seriousness. They ask it because they really cant understand why anybody would build a boat instead of buying one. There are so many boats out there that are available and can be acquired with so much less effort, new boats, good used boats, boats that have been damaged in weather events, tired boats that can be rejuvenated and almost dead boats that can be resuscitated.

There is no single answer to that question, there are many reasons why people build boats for themselves and each builder no doubt has a bunch of these reasons rolled up inside whatever it is that drives him to build his boat.

A reason that is common to all of the builders is passion. They have a passion to create a boat, to create something that would never have existed were it not for them and their desire to do this. Having been there myself many times, I can attest to the fantastic feelings that flood through when we first put that new boat into the water and then to give it life by hoisting sail or opening the throttle for the first time. If you think about how wonderful you felt when you first used a new boat that you had bought, doing the same in a boat that you have created with your own hands intensifies those feelings in ways that cant be described.

Petr Muzik built his Shearwater 39 then circumnavigated in his 70s.

It is that passion that also drives many of the decisions that are made during the build project. It drives them to do quality work because they want to feel pride in the final product. They want their creation to show well when seen by others, to be seen as a thing of beauty. Those who have never thought to build a boat themselves look at it and say "Wow, did you build that?".

Financial restraints are behind many amateur boatbuilding projects. Download the or want a new (as in not pre-owned) boat that costs double the money that you can afford to put into it, then the only route to get it is to build it yourself. I have never calculated ahead of my boatbuilding projects how much they are going to cost. Each time I have just dived right in and started, then kept going to the end. That was when I found out what the total cost was and was able to compare with what it would have cost me to buy an equivalent new pop-out production boat. Each time the cost of my fully-equipped boat was around 45% of the cost of a base-package for a production boat of similar size and concept.

Those who dont get it say "It cost you a lot more, you havent priced in your labour hours, which must be priced at your professional rate of pay". No, we dont price our labour into the project and no, we should not price it at the rate that we receive in our paying jobs, whatever they may be. The project serves as a hobby, as recreation that helps us to recover from a tough week working for someone else. It helps to keep us motivated and able to take on the world. The alternative of working very extended hours at our paying jobs to generate the funds to pay someone else to build our boat brings with it a risk of getting burned out in the process.

Andrew Morkel built his Argie 15. Now he and his family are learning to sail in it.

Many people who build big boats for long distance cruising want to build it themselves to give them confidence in the strength of the boat. They know that they will be sailing their boat on very remote waters, far from rescue services and possibly with their beloved family aboard. The safety of all depends on the quality of the build and they dont want to leave that to people whom they dont know. They have vested interest in doing everything in the best manner possible, so they want to do it themselves. In the process they garner the side benefit of knowing intimately how the boat works, where all of the important parts are, how to get to every seacock or filter in a hurry when dictated by some emergency that may develop onboard. They know exactly how to repair everything onboard because they installed it in the first place. They are likely to lay out all aspects in a very sensible and logical manner because they will have to maintain it themselves. At sea in a storm is not the best time to be trying to track down plumbing or electrical faults in systems that are overly obscure because the person who installed them before the hull liners or lockers were installed didnt consider the problems of working on them in the completed boat.

Others build their own boats because they want something different,  a boat that will stand out from the crowd on marinas, at sea and in distant anchorages. They add personal styling features to fit their own characters and they choose joinery detailing such as is not available from production boatbuilders.

Sergey Federov built his Hout Bay 33 to a very high standard.

Some people choose to build a boat purely for the hobby benefit. They enjoy the build more than using the boat, so the project will be drawn out interminably. They produce exceptional quality in the process but will probably sell the boat when completed or soon after.

It has been said many times that the happiest days of a boatowners life are when he buys and when he sells the boat. The exception to that cliche is the boatowner who has built his boat himself. There is so much of the builder wrapped up in that boat, in the form of blood, sweat and tears, to say nothing of chunks of skin and body hair, that he and the boat have an affinity and  intimacy that is unknown to those who buy their boats. I have felt very sad when selling each of the boats that I have built, far from the happiest days of my life.

It has also been said many times that boatbuilding is a disease and when you have had it, you will experience periodic relapses. I have to agree with this one, I have had numerous relapses. I cant say that I have suffered relapses, as would apply to most diseases, I have enjoyed those relapses too much to convince my wife that I have suffered in any way. And this is the way that most amateur boatbuilders feel. Visit any of the many boat shows that cater for amateur boatbuilders and you will see for yourself how much they love what they do and just how much passion they build into their projects.

To see our range of designs, for amateur or professional boatbuilding, please go to http://google.com.

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Its somewhat disappointing that we dont have images of every boat in the collection. Heres an example. I like this type of boat a lot: small cruising boat with a small deckhouse with big windows and shallow draft. Perfect for gunkholing and exploring just about anywhere. I think she probably looks a lot like Pelican, design #289. Click here to see an image of her.

I cant tell much about the design. The fact that she is entitled "one-design" tells me its a potential class boat for multiple builds. She was built by the Sound Marine Construction Company of Greenport, Long Island. The year was 1949.

Construction is typical S&S: mahogany planking over oak structure with silicon bronze fasteners.

Heres the general arrangement plan.


Heres a peek at the lines. As always, double click for zoom.

I receive a lot of questions and comments regarding the true cost of building a boat from scratch, full size patterns, and kits. Since I track time and materials closely, I have found that building from kits makes a lot of sense from an economic stand point. I took some discussions with customers/potential customers and put together this PDF on the economics of kits.

CKD Boats in Cape Town, South Africa, has supplied the first CNC pre-cut plywood kit for our new Didi 29 Retro design. It was delivered to owner/builder Mike Kopman at his home in Hout Bay.



You can see more information, including photos, on the  CKD Boats Blog . CKD Boats can ship a kit to you anywhere in the world. Our kit suppliers in other parts of the world will also be able to cut for you.

You can watch a video of my PechaKucha presentation about the design and how I developed it from the Didi 26 design.

For more information on our full range of designs, go to http://google.com/ .

Here we have an example of two boats of the same design built by two competent builders. Rascal was built by Henry Nevins of City Island. The principal plans were penned by the very talented Al Mason. She was launched in 1947.

Fast forward 14 years and we have Easterly being built and launched by Seth Persson of old Saybrook, Connecticut in 1961.

The following article tells a good story. Please double click for zoom.


Heres another article.


Here are the plans.


Take a look at this nice perspective Lines plan by Al Mason in the format of a half hull model.

Nirvana was built by Abeking & Rasmussen of Germany and launched in 1939. The boat was tragically lost in a fire in 1959. An exact replica is nearing completion at the Robbe & Berking Classics GmbH & CoKG shipyard of Germany to the complete set of plans supplied by Sparkman & Stephens. The rumors I hear say the boat has been purchased by a Swedish sailing enthusiast who plans to campaign her heavily. Construction images of the replica can be seen by clicking here.

Here are the plans.