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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Another Layer of Veneer and Shaping the Outer Stem

March saw the end of applying the first layer of Mahogany veneer, as seen above, and the beginning of the second layer.

This second layer is applied at about a 90 degree angle to the first.

Of course, the scribing as described in the previous post continues. Note some of the fancy scribing up near the keel in the picture above.

The hull looks different, a little more streamline, with the strips running from the top of the bow and angled toward the lower stern. Both directions can be seen from the bow.

Here are some "action shots" of the second layer being applied...

The hull is wetted with the epoxy.

Note all those plastic staples holding the veneer on...

The underside of the next strip is wetted with epoxy, and Richard mixes more epoxy with wood flour to the consistency of frosting.

The thickened epoxy is applied over the previously wetted area to fill voids and give a base for the strip to smoosh into...

Absolutely no voids are wanted in the hull. Richard is basically creating plywood in the shape of a boat by gluing up these thin layers.

The pre-scribed strip with the wetted back is set into position as marked.

Once the marks line up, a couple of staples hold it in position so that it can be smoothed down evenly.

Of course, if only one or two staples hold the upper end down, then as you work to the lower end the upper end will pop up...

Working it back down, from one end to the other. It seems to have a mind of its own.

Applying lots and lots of nails seems the only way to tame it.

All the way around every curve.

Pow, pow, pow...

Richard is starting to get very tired of this phase. It will be about 200 hrs into this phase when both layers of veneering are complete on both sides of the hull. He is ready for something new.

During some down time while waiting for the last of the plastic nails and more epoxy to arrive, Richard started to lay-up the outer stem. He used the extra mahogany veneer.

The outer stem needs to be shaped exactly the same as the inner stem. The stem is the front edge of the boat, as seen above. A piece of the veneer was screwed directly to the existing inner stem, and left to hang over on the right and left, to create a jig for the gluing and clamping. A layer of tape was applied to the veneer jig to prevent any excess epoxy from sticking to the jig. This would allow the thick built-up outer stem to be removed and give access for the jig to be unscrewed from the inner stem when complete.

Layer upon layer of veneer were epoxied together and clamped to the jig.

All the clamps that were needed to maintain the tight curve makes it look like a porcupine.

The outer stem is made long to run all the way up to accommodate the bow sprit (toward the floor at this point).

By the keel, it also runs long, and will be shaped into the deadwood.

The outer stem that has been being layed-up over days is then unclamped from its base form. The jig was then unscrewed from the inner stem.

The resulting thick stem is a perfect fit.

It will need to be shaped, tapered and cut to the correct width when it is ready to be permanently attached.

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Another Flint Launching

Ive just received an email from Flint builder, Ken Newey advising me of another launching of what is turning out to be a very popular design. Most of the boats built to the Flint design have been constructed by amateurs, and Im very happy to say that as long as decent quality ply is used, the boats go together fine. This is very gratifying, considering the extreme amount of twist in the developable panels used for the hull construction. The resulting shape shows lots of curce and concavity, which makes for a smooth ride in choppy conditions.

Photo of the first Flint, launched about five years ago?

Here is the text of Kens email: -
Hi Ross,

I notice you have other completed Flint builds on your website and thought it appropriate to send you a shot of mine. It took a bit longer than hoped to complete, but thats only because I didnt really do anything during winter and only got back into finishing it in October/November. As it is, its not quite complete - I am in the process of painting it - Ill follow up with another shot when its all done.

First time out (and each time since) I have had the whole family on board (~200kg) and used a 2hp Honda to push it along - cant really saw how fast I went but it seemed to be quite reasonable. I look forward to taking it out on my own. Final weight is estimated to be about 60kg, but you can see I have added to the gunwales.

I am also thinking about setting up the sailing rig and have built (not yet glued up) a mast using the birds mouth technique. The staves are roughly 20mm x 10mm so the finished mast should be around 50mm in diameter. The timber for the mast came from a 1.2m length of oregon verandah post ripped into 28 strips which were then scarfed to produce 8 x 3.5m staves. Not sure how this will turn out - but it was pretty simple to make. I will be using a timber plug in each end (protruding at the tip to take loops for the forestay and shrouds). Does it need any other internal plugs for hardware? I dont think so but I am working it out as I go along.

Regards,

Ken Newey

Kens New Flint, showing her nicely made inwales. Boat yet to be painted?

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