Glued Lapstrake Clinker Another Approach

Trailer and car-top boats are my specialty for a number of reasons - the primary one being that I dont have the resources to live near a deep water anchorage and so carvel-built boats kept on a mooring are beyond my means. 

Tom Dudgeon moored in very shallow water.
(illustration taken from Coot Club by Arthur Ransome)

But in many ways this state-of-affairs has turned out to be to my advantage. Large and deep boats are unable to visit the hundreds of thousands of superb shallow water destinations which abound along the coasts of most countries, and a cruise in a large boat can mean being imprisoned in a cabin or on a deck which is in constant motion while the crew view the exciting coastline from a long distance out. Every bar-crossing is a stressful event and very few nights on a cruise provide real rest because of the responsibilities of anchor watch.

On the other hand the dinghy cruiser can work up tiny creeks, cross bars where a mishap simply means stepping into ankle-deep water and pushing the boat across the obstacle into the calm on the other side of the bar. Some of the most enjoyable cruising Ive done (all in dinghies - sail and power) has included sessions of travel along the coastline with the boat just outside the shore break. This is most exciting and enjoyable stuff, providing close-up views of beach, rocky headlands, mangrove creeks, breaking reefs, entrances to bays which are invisible to the crew of boats further offshore etc. Sailing, poling or rowing across flats covered by two feet of water is challenging and deeply satisfying. The options available to the beach-cruiser are manifold....

Alec Morgans camp ashore on an island in Moreton Bay during a solo beach-cruising expedition. The trip was of about five days duration, and involved a whole range of coastal activities including exits and entries across surf bars.

I still suffer from a desire to spend nights aboard bigger boats, snug inside a cabin surrounded by sounds of the sea, listening to rain drumming on the deck. However, my wife, who has actually cruised and lived aboard larger boats for approaching nine years full-time, has told me the dream is frequently better than the reality. For her, cruising in a centreboard dinghy for the first time was a true and enjoyable revelation.

Anyway, Ive found myself spending a life involving small trailer boats, and I still get excited every time I head out (and in when Im tired/cold/hot/scared/hungry/sun burnt/hypothermic....)

Graham Faulkners Periwinkle in the beach slop

Son David and me approaching the shore after a very wet and cold sail  - heavily reefed and going like a rocket.

An extremely important element in successful beach-cruising is light gear, and light-weight boats. It is no fun not being able to haul a boat up past the high-water mark, and even worse being unable to get a boat back down the beach to the water. Also, late middle-age has taught me that manoeuvring a trailer around the yard by hand has become more difficult than it was.....

Launching the Francois Vivier Aber I built for Dr. Paul Truscott. She is quite a large boat for her length, but the entire package can be wheeled around on land on her trailer by a single person with relative ease. As you can see, launching and retrieval are a breeze, without even having to immerse the trailer wheel bearings.

Very light-weight hulls can be built using cold-molding techniques, foam-cored construction and glued-strip planking, but all of these methods are fairly complex and/or expensive. My choice of methods for light-weight, inexpensive, quick, and simple construction include stitch-and-glue plywood and glued-lapstrake (clinker) plywood.

Periwinkle under construction using glued-lapstrake techniques.  Most of the weight in the internal structure gets left on the mold strongback.

Will Shrapnels boat being built using the stitch-and-glue method. This is my Fleet design  - a very light boat.

Recently I was commissioned to build an Annapolis Wherry Tandem from a Chesapeake Light Craft design. I was interested in building this boat having previously read about the patented "Lap-Stitch" method devised by Chris Kulczycki. "Lap Stitch" is a trade mark, but I cant make this program insert the symbol!

Cover shots from Chris Kulczyckis book The Canoe Shop in which I first read about the "Lap-Stitch" construction method. That is John Harris, owner of Chesapeake Light Craft, in the paddling photo.

"Lap-Stitch" combines the advantages of both glued-lapstrake and stitch-and-glue construction methods, meaning that a shapely glued-lapstrake hull can be constructed without having to use a strongback and station mold set-up, saving time and making the somewhat intimidating glued-lapstrake construction method accessible to inexperienced builders. What makes this possible is that the overlapping planks have a rebate machined into one edge instead of needing a varying bevel planed along the edge(s) - something which worries many beginners. The key, though, is not that the beveling operation is avoided, but that the inner edge of the rebate "hooks" onto the edge of the preceding plank allowing properly developed planks to be stitched together in a manner very similar to that used in normal stitch-and-glue.

A drawing I did to illustrate the difference between Glued-lapstrake and "Lap-Stitch"

Any true stitch-and-glue design relies on extremely accurate panel development and panel cutting in order to have the hull adopt the correct three-dimensional shape, and the same remains true for "Lap-Stitch". Once the hull has been stitched together, it is positioned upside-down and relatively low-viscosity epoxy is run into the open lap rebate and allowed to set. Not only does the technique require the accurate panel development and a defined rebate, but it also needs an adhesive which is truly gap-filling in a structural sense - and the adhesive must be runny enough to work into the gaps under gravity - but not so thin that it runs all the way through to drain out on the inside! As far as I can see, only epoxy is practical for this, and it must not have much of the glue thickening additive included in the mix.

This is the only photo I have which shows the rebate machined along the edge of a plank.  Here I am cutting through one of the tabs holding the plank into the plywood sheet after the shapes have been cut with a CNC router. You can see the routed rebate under where my left hand is gripping the plywood.

Annapolis Wherry Tandem during the initial stitching-up process

Plenty of stitches required. I elected to use plastic cable-ties instead of the  copper wire  recommended by the manufacturer of the kit. I find the cable-ties are less likely to damage the soft plywood, and are easier to tighten and to remove. You can just make out the "jigsaw puzzle" joints used to join the planks longitudinally. I will have more to say about these in a coming post, but in the meantime Ill be using scarph joints on my boats.

Here you can see the stitches on the inside of the hull.

In this photo you can see where I have run the epoxy into the gaps of the plank laps. I am fastidious about  gluing-surface preparation, and I took exceptional care to get the epoxy into the gaps to the maximum extent. Although I used a hypodermic syringe without a needle to run in the epoxy, the process was messy and slow. At this stage the epoxy had cured and I had removed the ties holding the laps. The remaining ties are the ones holding frames and bulkheads in position.

This is a section through one of the plank laps at the transom, showing the rebate, the initial low-viscosity epoxy which I worked into the seams with great care, and then above that the more thickened epoxy which I used to completely fill the seam.  To be done properly, the job requires great care and attention to detail.

I dont have any suitable photos, but this drawing shows a section through a conventional  glued-lapstrake hull showing the beveled laps with parallel-sided glue lines.

200gsm (6oz) woven glass set in epoxy over the flat bottom panel and the first two planks on each side of the Annapolis Wherry Tandem. The wide white lines are epoxy fillets used to fill out the internal plan laps so that the glass cloth will lay fair.

External glass cloth over the bottom panel and the first plank (garboard strake) on each side. The internal and external glass shown is as per instructions.

Recent photo showing external paint nearing completion

A long and lean boat - awaiting final internal sanding and painting

Well, that is a brief run-down on "Lap-Stitch". I think it has a place for some people - especially beginners. However, like all boat-building methods, it does require serious attention to detail, and should not be taken lightly. For myself, Ill stick to the normal method using a station mold and strongback, as I like the tighter glue-lines and neater work. My opinion is that I could have built the strongback, mold and the boat using conventional methods faster than by going through the messy gluing process and filling of hole associated with the "Lap-Stitch" system. But that is just my own opinion, and I can see a real place for "lap-Stitch" as long as the plank patterns are accurately deigned and cut, and that the person doing the work is happy with relatively heavy epoxy use in comparison with conventional glued-lapstrake. Id say the building process is more simple for a tyro than the conventional method, but not any faster.

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A Putt Putt Boat in Glued Lapstrake

In 2003, things were going flat-out in my workshop in Wynnum, Queensland, Australia. There were two of us working full-time, and one working part-time, and yet we were building up to six boats at one time. In addition there was design work to complete, as well as day-to-day stuff like retail sales and sorting through the accounts. At the time it was a kaleidoscope of activity, with fourteen-hour days and doubts about where the money would come from, but I still miss those days....

Busy Workshop - at the time I think there were five boats under construction and several repair jobs in progress, like the one in the foreground. We were even doing things like repairing a Wurlitzer Jukebox at the same time!

Anyway, one of the many interesting projects that we were approached to build was a Putt-Putt Boat of the old style. Our customer wanted a simple, low speed launch to take himself and his wife on gentle outings upon the Fitzroy River in Rockhampton. Bobs wife had been diagnosed with a serious illness, which complicated the process, but they both looked forward to lazy, quiet days on the river. Their boat would be called, "Picnic".

As was often the case in those days (and is still the case today!) I was frequently called on to choose a suitable design as well as to build the boat. I knew of a 14 ft Putt-Putt design from the board of Australian designer David Payne, which had a very attractive shape and suited the function very well. I had seen a number of these boats on the water, but they all seemed to lack buoyancy when loaded with the engine and a crew of two or more adults. In addition, they seemed to trim by the bow, which was not surprising given the very fine sections up foreward, and the small size of the boat.

With this in mind, I suggested to the owner that we lengthen the boat on the same sections to increase the displacement without altering the character. My suggestion was to increase the station-spacing by around 10% to end up with a boat of 15ft 6ins (4.724m) on the same beam. I contacted the designer, David Payne, and was given permission to go ahead with the proposal. In addition to the length increase, I moved the location of the engine aft slightly to further aid the lack of buoyancy in the foreward sections. All of this proved to be highly successful in use.

The matter of power-plant was extremely important, and I was lucky enough to have the perfect engine on hand. It was a brand-new (but 25 years old) William Olds & Sons 6hp Type "H" 4-stroke marine petrol (gasoline) engine.

The beautiful Wm Olds & Sons 6hp Type "H" - 25 years old, but still brand new!

 The engine was a nice match for the boat, being relatively light, very smooth-running, and designed to operate at the correct speed for direct drive without reduction gears.

Planking complete, and working on shaft angles. The "skeg" is just a thin MDF pattern - much larger than the proper skeg would end up being. Note the essentials - a string-line and a calculator!

Construction proceeded well, although we changed the lining-off of the planking compared with what had been suggested on the plans. Lining-off is a matter of taste and does not have any structural impact on the boat. It is amazing just how much a millimetre of change in a line can alter the aesthetics of a hull. The thing is to trust your eye.

Engine installed and the coaming being laminated into position. Lamination of the coaming used up lots of clamps. The shape was quite complex, as it had to take into account the hollow sheer-line and the substantial deck camber across the foredeck

I did a full-size lofting of the lower part of the hull in order to calculate the propeller shaft line and to draw up the engine mounts. The skeg  was completed and attached before the boat was turned upright.

Most of the construction work completed, and awaiting details such as the rudder and the final engine installation.

Doug and Rhonnie looking relieved after lowering the engine into place for the final time!

This is the roof framework to carry the canvas-work over the cockpit. Lots of curves and bends so that it mirrors the sheer-line and shape of the boat.

This photo taken during painting of the roof framework shows how complex the shape was to construct. This was my design - not part of the plans

The finished boat, but without the tailored canvas sunroof. The four uprights were able to fold down, and were easily detachable

Simple engine installation, as befits such an elegant craft

Oiled floorboards were individually spiled to shape, and we stamped them with numbers to aid re-installation when required

Details of deck arrangement and brass rubbing strips

"Secret" launching before owner pick-up.

Power trials with engine at a low throttle setting. The easily-driven hull moved nicely with the engine running gently and quietly. This photo was taklen before we had installed a foreward thwart, which accounts for Dougs head being so low!

Here you can see the propeller and the rudder arrangement (as well as some of the local artwork on my workshop walls)

The end result of this job was a simple, efficient and satisfying boat - everybody was happy.

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Glued Lapstrake clinker Plank Fairing

Glued-lapstrake is a deservedly popular method for building one-off boats in wood/epoxy - for a number of good reasons. In the case of the amateur and small-time professional builder it gives just about the fastest path to a handsome, round-bilged hull, with the added benefits of being light, strong, attractive given the plank lap lines. Very importantly, the building jig is simple and easy to build.

Ill write more about the particular advantages of the glued-lapstrake building method in another posting, and Ive previously pointed out the way in which a fine entrance combined with the prominant plank laps keeps spray knocked down in a fashion similar to sprayrails.

In the above video, you can see how well the plank laps work at knocking down spray, although the boat (my Periwinkle design) is running in very light winds - but you can clearly see the principle.

To get back to the point, one particular advantage of glued-lapstrake construction is that the building jig need only consist of relatively few, widely-spaced molds or frames, with the plywood planks bridging the gaps between the molds in a fair curve.

Here is a typical glued-lapstrake jig, showing widely spaced molds made from disposable material. In this case the boat was a Francois Vivier-designed Aber which I built for a customer about five years ago.

Plywood is a wonderful material if you can locate good-quality sheets, but one of its virtues is also a liability. Plywood is of almost equal strength in all directions, and is frequently used in much reduced thickness compared with solid timber. The problem is that very occasionally the planks may tend to flatten out between the molds.

Plywood planks going on over widely-spaced frames and molds. This is Periwinkle

Some people put stringers into their molds, but this adds a lot of complexity to what should be a simple set-up, and adds considerably to the cost of the mold. In addition, it makes removing the boat from the mold difficult, especially if the boat has any tumble-home (that is where the sides of the boat curve in towards the centreline of the boat as they get towards the gunwale as frequently seen on "Canadian" canoes for example).

If the building jig is a simple one without stringers, it is easy to access the inside of the boat during construction, and when it comes time to remove the boat from the jig, all one has to do is knock the individual molds out one at a time.

However, there are occasions where the thin planking refuses to lie in a smooth, fair curve - usually just in a few odd places. When I am faced with that situation I use a technique where a stringer, or batten, is applied to the outside  of the hull. It need not even be a full-length batten - just enough length is required to span three or four molds. Temporary plank fasteners are driven through the batten to hold the plank while glue is curing, just as in the rest of the planking job.

Here you can see a temporary batten sitting over a plank lap on the original Periwinkle. There was a little flatness towards the bow (which has been fixed now with a minor alteration to the plans)

Close-up of the batten showing how it sits over the plank lap, and also showing where one of the temporary fasteners has been driven through.

For a job such as this you can usually get away with a single batten, re-used on subsequent planks if and where required. On Periwinkle the batten shown did the entire boat. But it needs to be empasised that the extra fairing is very rarely needed - but it is nice to have the technique available in situations where the ply is a bit too limber, or there is an inaccuracy in the jig.

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