Monday, August 27, 2012

Glued-Lapstrake (Clinker) - Another Approach

Trailer and car-top boats are my specialty for a number of reasons - the primary one being that I don't 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 I've 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 Morgan's 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, I've found myself spending a life involving small trailer boats, and I still get excited every time I head out (and in when I'm tired/cold/hot/scared/hungry/sun burnt/hypothermic....)

Graham Faulkner's 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 Shrapnel's 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 can't make this program insert the symbol!

Cover shots from Chris Kulczycki's 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 I'll 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 don't 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, I'll 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. I'd say the building process is more simple for a tyro than the conventional method, but not any faster.

Friday, August 17, 2012

Modifying Tools - #1 - Fein Multi Master

Much of the time I make use of hand tools - not because they are quaint or traditional, but because they work fast, predictably, and quietly.

Using a spokeshave on during the construction of a Francois Viver Aber. I was not aware that my wife was taking this photo  as I was concentrating on my work, so you can be assured that the photo was unposed.
Despite my preference for hand tools, it is obvious that for certain jobs power tools allow one to get a lot more work done in a given time, and so where there is a real advantage I have no inhibitiions about picking up an electric or a pneumatic tool. Some become real favourites, and close to the top of my list is the Fein Multi Master.

I have three of these tools - two are mains powered electric versions and one (not a Fein, but identical in operating principle) is a pneumatic version of very high quality made by a Japanese manufacturer who's name escapes me. Fein Multi Masters are expensive, and the pneumatic machine was astranomically expensive, but quality is usually worth the money. For those on a tight budget, the are a number of cheaper brands coming on the market.

Two photos of a Multi Master in use on First Mate
The Multi Master performs a number of tasks using a range of fittings including the triangular sanding pad shown in the photos above, as well as cutting and scraping using several different knife and saw attachments. The use to which I put the machines for the majority of the time is sanding.

What makes a Multi Master (and its copies) so good? Well, most triangular detail sanders work on the orbital principal in the same way as 1/2 sheet and 1/3 sheet orbital sanders. The problem with such an operation is that when you run the sanding pad up against an edge such as in the above photos, the orbital action causes the machine to bounce off the adjacent surface in an annoying and somewhat violent fashion.

However, the Fein Multi Master operates on a different principle. The sanding pad (or saw blade, knife etc) oscillates through an arc of about 1-1/2 degrees in each direction at very high frequency. You will note in the photos that the three sides of the sanding pad are slightly convex, and when you run the pad up against a hard edge, the machine continues to operate smoothly despite being in contact with the adjacent surface. In addition, the sanding action is much more effective than that of an orbital version. Make sure that anything you buy has an oscillating action - not an orbital action.

The metal backing plate to which the foam backing pad and the 'hook-and-loop' is attached. Note the convex sides.

My one complaint is that the sanding 'discs' are expensive, and are held on the pad by a fine 'hook-and-loop' material like Velcro. Because the oscillation frequency is high, and the pad is basically contacting the same place, heat due to friction is not removed by constantly rotating pads, and it is very easy to melt the plastic in the 'hook-and-loop' material. To get around both of these problems, I peel the 'hook-and-loop' off the face of the sanding pad, and use sticky-backed paper placed directly against the dense foam backing on the sanding pad. I cut my own sanding 'discs' by tracing around the machine's pad onto 200mm (8 inch) sticky-backed sanding discs which can be bought in bulk from the hardware store at reasonable prices. I cut them out using a utility knife of robust shears, and I think I get about 6 or seven from each 200mm disc.

Occasionally I find that I need a really flat and hard backing for the sanding 'disc' and I have developed a modification which works superbly well. What I do is I peel the factory-supplied dense foam pad off the alloy plate (I keep a number of spares in my workshop) and in its place I glue on a pad of 6mm (1/4") marine plywood which I cut from scrap. Then I simply attach the stick-backed paper in the normal manner. See photos below.

My modified pad, with 6mm (1/4") plywood glued to the alloy plate using contact adhesive
A nice, flat and hard surface to which the sticky-backed sand paper can be applied. The counter-bored hole in the ply is to ensure that the attaching bolt for the alloy plate does not interfere with the sanding surface.
I hand bevelled the edges of the plywood to replicate the shape of the foam pad.
In some future postings, I'll decribe some other tools which are rarely mentioned, but which I find particularly effective.

Wednesday, August 15, 2012

It is the 'average' of the job which matters - advice for the perfectionists

This is the text of an article I wrote many years ago - the message is still important...

A Phil Bolger Micro and an Iain Oughtred Tammie Norrie in the workshop I rented after first turning professional

Ian lay against the wall of the workshop, seated on an off-cut of plywood placed across a pair of sawhorses. He raised his eyes from the jumble of boating magazines on his lap and contemplated the scene within the building. 

Mike Rowe was completing the final stages of the scarph joint which had changed two sheets of 9mm plywood into a single 4.8metre panel. Ian had been able to watch the whole operation as though a fly on the wall, his friend being almost unaware of another person in the shop.  

What interested Ian was the speed with which the scarphing operation had taken place, despite Mike having been interrupted by a customer call. 

“Hey Mike,” he called, “Do you realize that you would have taken three weeks to do that job a few years ago, but that that one took less than fifteen minutes?” 

Mike Rowe glanced over at him as he tossed a pair of disposable gloves into the bin and washed his hands in the grubby wall-mounted sink. “The reason that I used to be so slow,” said Mike, “was that I used to be frightened of making a mistake. I would plan the whole operation (whatever it might be) in great detail, but the more I planned, the more complicated it became in my head. Fear of wrecking the job really slowed me down.” 

Warming to the theme, Mike continued. “I’m still concerned about making errors, but part of the learning process involves understanding that mistakes and accidents will occur, but that just about anything can be fixed properly.” 

Having dragged his body away from the empty coffee cup and stack of books, Ian cast a critical eye over the scarphing job. He noted that although it was not perfect, it was neat and very accurate. The feather-edge of the plywood scarph showed some unevenness where the razor-sharp blade of the block plane had jagged the wood fibres – but these were minor errors of no structural concern. 

“It is the ‘average’ of the job which matters, not the occasional fault,” observed Mike. “If you just keep trying to be accurate and thorough, the job will work out well, despite the saw wandering or the chisel slipping”. 

Mike flicked on the kettle. “What used to happen was that I’d become discouraged by mistakes. Then I would either walk away for a week, or I would drop my standards because I thought the job was no longer perfect.” 

Nodding slowly, Ian reflected on the number of times he had experienced the same feelings…

A Phil Bolger Harbinger catboat in my second professional workshop. She was built strip/diagonal from one lamination of Western Red Cedar strip planking and two laminations of Hoop Pine diagonal planking

Let us leave this imaginary pair in the imaginary workshop, but think about their story. Once you lose momentum on a project, it is very difficult to get going again without encouragement.  

Most amateur builders work alone, juggling work, family, finances and time. A minor setback can seem disastrous, and it is no wonder that some boatbuilding jobs are never completed. Others get finished, but in a slap-dash manner because reality hasn’t matched the dream. 

Don’t lose sight of the dream, but be realistic about the outcome. As long as the wandering saw keeps coming back to the line, the overall result will be good, and the care will show. Attend to errors where they occur, but keep on working with accuracy in mind.

Wednesday, August 1, 2012

Balance Lug - Rigging Details

If you are looking for a super-simple rig which is effective on all points of sail, and which can be put together with the absolute minimum of fittings, the Balance Lug could be for you.

Phoenix III showing-off her Balance Lug rig option.
I first used the Balance Lug for the first time in about the year 2000, nearly forty years after first learning to sail, and I have to say that it was a revelation. For most of my sailing life I've been interested in the simple rigs associated with small working boats, with particular focus on the Chinese Lug (a.k.a. Junk Rig), the Standing Lug, and the spritsail in both it's leg o'mutton form and the better known four-sided layout.

The Chinese Lug
Four-sided Spritsail with a jib set flying - Phoenix III

Leg o' Mutton Spritsails on my Little Egret design
Standing Lug with a sprit boom shown on my old Phoenix, designed by my father back in 1970. She is the same boat as in the photo showing the Chinese Lug. She has been the workhorse for my rig experiments, and has carried at least eight different rigs (so far...)
Dipping Lug. This boat is a Francois Vivier Aber which I built in 2007

All of these older working boat rigs evolved over long periods of time, and the evolution was not perverted by the artificial constraints imposed by the rating rules used in various forms of racing. These rigs were developed by people who required low-cost, reliability, ease of operation, and repairability in order to survive on the oceans, lakes and rivers of the world. The result is that the rigs work efficiently with the minimum of costly fittings, and they are reliable. If the crews understand the idiosyncrasies of the rig, their performance can be superb.

The Balance Lug is said to have been a pleasure boat rig more than a working boat rig. It has been said that the working boatmen would have found the boom to be an annoyance, particularly because of its self-vanging characteristic. For many years I discarded it as a worthwhile rig for a reason which seems to worry a lot of other people as well, and that is that the rig appears to be so asymmetric with the sail being distorted by the mast on one tack. That is a strange attitude for me to have, because the Chinese Lug (one of my favourites) is similarly asymmetric.

They say it is a virtue to become aware of one's own stupidity, and that was brought home to me in about 2003 when my friend, Doug Laver, gave me a near-new sail which was surplus to his requirements. The sail was a Balance Lug, and I added it to the inventory of sails I had for my old boat, thinking it would be interesting to try out, but not thinking much more about it. However, after several moths of regular sailing, it occurred  to me that the sail I was using most often was the Balance Lug, and that I was almost totally oblivious to the asymmetry which had worried me so much in my armchair theorising.

A Jim Michalak-designed Mayfly 14 demonstrating satisfying performance with her Balance Lug
So, what is it which makes the Balance Lug such an appropriate rig for a small cruiser? Here is my take on the rig: -
  • The sail is not attached to the mast anywhere, but is simply laced on to the boom and the yard. This greatly simplifies rigging, unrigging, and reefing as there is no sail track, no mast hoops, no luff lacing, and no slugs or shackles;
  • The halyard and down-haul are simply attached to the yard and boom by a rolling hitch - at least in the case of small boats. No expensive fittings, no gooseneck, no slides, no shackles;
  • Because the boom extends forward of the mast, the combination of the downhaul adjacent to the mast and the upward tension in the luff of the sail pulling the forward end of the boom upwards, the rig is self-vanging. No boom vang and associated pulleys and shackles required;
  • The luff of the sail is well forward of the mast, working in clear air free from mast-induced turbulence;
  • When the halyard is released, the sail always comes down on its own. No more tugging away at reluctant sails stuck in tracks;
  • Furling the four-sided sail is convenient, especially as the boom and yard can remain attached;
  • Reefing is convenient, quick, and neat. The remaining sail shape is good, and the sail cloth is not strained. Reefing can be done with nothing more than some light line, and the resulting centre-of-area of the reefed sail is very close to being in the same longitudinal location as with the full sail - in many other rigs, the reefed centre-of-area moves forward significantly;
  • Being balanced by the portion of the sail which extends forward of the mast, sheeting is light and gybes are relatively gentle;
  • The mast, boom, yard, and sail make up into a neat bundle for transportation and stowage.
There are plenty of tricks which can be employed to make the sail even more versatile, the most important of which is the use of a parrel on the boom. Here is how I do it, but there are plenty of other methods.

This is the view from above showing the boom parrel looped around the boom with a loose bowline (or rolling hitch if you like), and then running around the mast, forward to a hole through the tack end of the boom, and back to a cleat on the boom which is within easy reach of the helmsman. By tightening or loosening the line at the cleat, the entire boom and sail can be moved aft or forward relative to the mast location, making alterations to the balance of the rig. 
Here you can just see the downhaul on the port side of the mast, and the boom parrel running around the starboard side of the mast and extending to the forward end of the boom.
This is a closer view of the same arrangement
An out-of-focus photo, but you can see how the parrel runs through the boom and then back to a cleat placed anywhere handy on the boom

A view from below showing the entire set-up. All very simple, but also very effective.

This view of Periwinkle with her heavy weather rig set-up shows the mizzen mast removed, the main mast moved aft to a more central step, and the main sail set on its own, with a reef tied in. See how well the sail will set when reefed. This particular sail is set loose-footed, but it would probably be better laced around the boom.

The Balance Lug is a simple, effective, and versatile rig which can be put together with few, if any, store-bought fittings. The unobstructed luff, free from turbulence generated by the mast gives far better windward performance than many would imagine. The above video clip shows just how well the Balance Lug can drive a small boat, which in this case is my Phoenix III design.