Fine Lines and Lapstrake Clinker Hulls

I was having a discussion recently with one of my sons about which hobby activity was the most fun. We have far too many hobbies, but flying and sailing are close to the top. Well, we both decided that there was no contest - dinghy sailing came out as number one.

Where I live, the biggest problem with sailing is exposure to the savage sun, but running a close second is being continually doused by water as you drive to windward. Yes, I know that we have a nice climate on the east coast of Australia (at least as far north as we are), but for a large part of the year the water is frequently very cold when it hits a hot body!

Most of the boats that I have sailed have had relatively blunt forward sections, and they tend to bash water into the air when butting into a wave, and the wind blows it back directly over the crew.

Hard to windward with a deep reef tied in - relatively smooth water as we exit the harbour, but we are still getting wet!

There are plenty of advantages in having full sections forward, such as adequate buoyancy when running down waves, and the ability to move forward in the boat while still retaining reasonable trim. In some boats where load-carrying is critical, a very broad bow is essential - for example a praam dinghy

My Alby design - lots of carrying capacity in a short hull

The problem is that the disturbed water pushed up by a blunt boat - at least in a dinghy - consumes power, and as previously mentioned, bashes water up into the wind so that it can wet the crew efficiently.

This is a nice design I built a few years back, but you can see that she pushes up a lot of water, even in light conditions

Here is another good example - a really nice design, but pushing up lots of water.

In both of the above photos, the boats were drawn by exceptionally good designers, and the shape ended up the way it did for important reasons. But it does demonstrate the point Im making about the water.

When I was asked to design Phoenix III, I really wanted to keep the bow fine. In fact, it has become a bit of an obsession with me, although I do change my attitude when necessary (e.g. Alby and Whimbrel).

Phoenix III showing her fine forward sections

My reasons for going down the path of fine forward sections include: -

• Dryness when pushing to windward;
• Reduced pounding - something which is very important in a small and light-weight boat;
• Easily driven hull - particularly when under oars

Paul Hernes in his Phoenix III under oars - he is too busy smiling, and should be rowing faster!

One of my favourite methods of construction is glued-lapstrake (or glued-clinker). This system is only possible if the planks are made of plywood, because natural timber planks lack cross-grain strength and will crack where the thickness of the planks changes from double to single. That is why traditional clinker hulls have lots of closely-spaced bent ribs, and have their plank laps riveted or clench-nailed - the ribs provide cross-grain strength, and the mechanical fastenings allow the planks to move relative to each other as the boat shrinks and swells in changing conditions. Plywood has almost equal strength in all directions, and can be glued at the lap - this produces a strong, stress-skin hull which requires few, if any, internal frames. The glued laps form an integral "stringer" which further strengthens the hull.

A clean and open interior

A wonderful side-effect of the lapstrake construction method is that the laps produce a series of "spray rails" on the external surface of the hull.

Fine forward sections and prominent laps on my Periwinkle design

The combination of the fine lines and the overlapping planks makes for a dry ride in most conditions.

Here is a good example of the effectiveness of the sharp forward lines and the "spray rail" action of the laps. This is another photo of Periwinkle.

As with all things, there are drawbacks. Any boat with fine lines forward (or aft for that matter) needs to be properly trimmed, as they are sensitive to weight distribution.

Here, the crew of Periwinkle is a little too far forward for the conditions. In gentle winds their position would be ok, but I think the big mainsail was driving her down somewhat at the bow. However, she is still going nicely!

Every boat is a compromise, and there is a place for all different sorts of hull shapes. The more more you understand about hull-forms and construction methods, the easier it will be to make a decision about what is right for your circumstances.

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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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