Monday, February 28, 2011

New Post Delayed

On Friday I had a major computer hardware failure and have spent the majority of the weekend and half of Monday purchasing new gear, and transferring data from old to new - luckily I have extensive back-ups, but the installation of programs has taken up a lot of time. I will try to get a new post or two done in the coming twelve hours.
First thing on my list to discuss is why the centreboard and case in both Phoenix III and First Mate have the raised section at the forward end.

Wednesday, February 23, 2011

Building Phil Bolger's Harbinger

Back in 2002, I received a request from a customer for a pretty Catboat. I can't remember the initial wish-list, but when I showed him Phil Bolger's Harbinger design, he was hooked. Harbinger is a Catboat of the New York model, rather than the better known Cape Cod model, and she has exceptionally fine and easy lines.

Fine lines

Easy bilges

Harbinger was designed with rowing as the primary source of auxilliary propulsion, and the New York model was much better suited to this than the more buxom Cape Cod hull-form. Phil had designed the boat to be built plank-on-frame carvel, but as the customer intended to leave the boat out of the water on a trailer, we had to come up with a different method of construction - carvel would open up when dry. The most obvious options were, glued strip-plank, glued lapstrake, and cold molded. I decided to go for strip-diagonal cold-molding, and wrote to Phil to get his permission. He was very happy with my construction plan, but indicated that he was frightened by the labour-intensive nature of the method.

The boat turned out to be very successful in construction and use, and I'd love to build one for my own use. Very briefly, here are the primary stages in construction: -

MDF Molds set-up.

7mm WRC strip Planking.

First of two layers of 3mm Hoop Pine diagonal planking.

Lots of staples needed in hollow sections - used a total of 18 thousand, put in individually and pulled out by hand.

Diagonal planking finished. Hull thickness 13mm (just over 1/2").

Shapely and massively strong hull.

Launching day.

First sail.

Phil Bolger's Harbinger
When I can get around to it, I'll put up a photo gallery showing the construction in more detail.

Sunday, February 20, 2011

Lapstrake Planking - cutting a rolling bevel

I recently received an email from Patricia Hong, asking for some clarification on the system I use for cutting plank bevels when building lapstrake (clinker).  I thought the email and my reply (attached to the original in red to save time - we were still in flood-recovery mode) might be of interest to others. Here it is, along with some illustrations for clarity.

That is me, cutting a plank bevel on the first Periwinkle
  1 :  Is this plane just drilled and a threaded rod put through the body of the plane ? I just drilled one of my low-angle block planes (on a cheap drill press) to accept a piece of brass rod which I had on hand. The rod is a neat fit in the hole, and can slide through to project any length I want, on either side of the plane.

2 :  Does the rod align flat  with the bottom / bed of the plane ? The bottom of the hole (and the bottom of the rod) are 11mm above the bed of the plane. I did this because I had access to cheap pine square-section moldings from the local hardware store which were 11mm x 11mm, and I used these as battens. See answer to next question. 

3 :  The guide / rod appears to be riding on the batten fixed to the mold stations and frames/bulkheads to  follow the rolling bevel of the laps .
Does this batten have to match the thickness of the planking stock in order to cut the correct bevel on the planking stock ?
No, it is independant of the planking thickness, but the batten needs to be the same thickness as the distance from the bed (or sole) of the plane up to the bottom of the rod (or the hole). So if a tangent to the rod was positioned 12mm above the sole of the plane, you would need to use a 12mm batten, and so on. All that you are doing is ensuring that the sole of the plane is parallel with an imaginary line drawn from the point where the next plank touches the mold (i.e. where the batten is positioned - in fact parallel with the bottom surface of the batten) to the bevelled lap on the plank which is already in position. I think my description is confusing, but the attached sketch may explain.

I hope you don`t mind all the questions No, I don't mind at all, and I'm only too happy to help where I can , and I hope they make sense to you Yes they do, and I think they are very sensible questions , as  I would really try my hand at clinker / (  lapstrake? )  boat building , and your method of cutting rolling bevels appears to be the best way to do this. Glued lapstrake is my favourite method of construction for small craft. It is nowhere near as difficult as some people imagine, but it does need the application of some common sense. Please let me know if you want more information. There are several excellent books on the subject,including Iain Oughtred's "Clinker Plywood Boatbuilding Manual" , Tom Hill's "Ultalight Boatbuilding" and "How to Build Glued Laptrake Wooden Boats"  by John Brooks and Ruth Anne Hill.

Wednesday, February 16, 2011

How good are small boats?

My three sons (one of whom built his first boat at thirteen, and a lapstrake sailing dinghy at age fourteen) seem to have picked up one of my bad characteristics - that is, having too many interests.

The boatbuilding boy is obsessed with sailing, model aircraft, engines, quality cars, and full-sized gliding. He recently confided in me that he had plenty of other potential hobbies, but time and space have already become critical. Welcome to life, I say!

Recently he and I went for a really good day of sailing in his recently-acquired-but-very-old Jack Holt-designed Lazy E (a.k.a. National E). We experienced 20 to 25 knot conditions, and had to work very hard indeed to keep the old boat on her feet. But what a ride we had! Lots of trapeze work, and lots of planing. At one stage as we were planing on a reach, my boy yelled from the tiller that if Green Island hadn't been in the way, we would have had to keep going to New Zealand, because it was too much fun to change tacks.

This reminded me once again just how much satisfaction you can get from sailing dinghies (dinghys? - I don't know how to spell it...). The interesting thing was that when I questioned this young man about which activity he would keep doing, if only one was allowed, he was emphatic in saying it would have to be sailing. This is despite the obvious attraction of the aviation and mechanical interests.

I have a theory that the human brain stores away the sounds, and sights of a days sailing, and that the beneficial effects last for weeks or months. It doesn't take much to keep me going, although more is always better.

Tuesday, February 15, 2011

More about Flint

I've recently received an email from a fellow who is interested in putting a sailing rig on Flint and I thought that my reply may be of interest to others. Here it is (with some illustrations added) -

Dear Martin,

Thanks a lot for your email, and please accept my sincere apologies for the late reply. For some reason or other, I forgot to highlight your email for a response, and I've only just re-discovered it!

Flint was designed as a rowing boat capable of taking a very small outboard motor i.e. the hull is optimised to be easily driven at displacement speeds. One of the primary requirements was for her to cut through a short, steep chop with minimum pounding.

Eddie Guy's Flint, built to replace a flat-bottomed boat which pounded too much, and was difficult to keep on course
 She was actually designed for an experienced waterman who lives on one of the Moreton Bay Islands, who had been having lots of trouble with an existing long, narrow rowing boat which had a flat bottom.The existing boat pounded badly and was difficult to keep on course when rowing in a crosswind.

It is common for passengers to sit too far aft in small boats, particularly when using an outboard, so I deliberately desinged Flint with quite wide sections aft, but only above the waterline. Therefore, when trimmed properly she is effectively a double-ender, but if someone moves too far aft, the wide sections pick up buoyancy quickly.

Note the wide aft sections on Bill Bronaugh's Flint
  As a rowing boat she has proved to be very successful indeed. One builder has taken his Flint on a number of  coastal cruising trips of several days duration, entering and leaving his home port on the Gold Coast through the surf. In addition, he uses her occasionally with a "crab claw" rig made from polytarp, without any form of centreboard or leeboard. Despite this lack of conventional lateral plane, she sails quite effectively, so I'm assuming that the very sharp forward sections provide reasonable lateral resistance - particularly in a chop.

Alec Morgan's polytarp Crab Claw rig - it works very well!
 Under power, Flint is extremely efficient. On the day we tested the one I built for a customer, we achieved a GPS-measured speed of 6.1 knots with two adult men and two teenage girls aboard (probably an overload) using a 2 horsepower Yamaha two-stroke at just over half throttle. Steve Dorrington, in New Zealand, has got his Flint to 6.3 knots with a 2.5hp British Seagull, which is amazing when you consider the gear ratio and propeller design of such a motor. 

Steve Dorrington doing 6.3 knots on 2.5 Seagull horsepower!

6.1 knots with a 2hp Yamaha, and a heavy load
 But to get back to the hull design -  When looking at the lines, I noticed that the wider sections above the waterline aft had produced quite a reasonable sailing hull, and a year or two after the boat was first built, I caved-in to pressure from a number of people, and I designed two sailing rigs - a gaff-headed knockabout (sloop) rig, and a gaff-headed cat rig. I normally use free-standing rigs, but in this case I decided to use stays in order to keep the diameter, length, and weight of the mast as low as possible, and more importantly, so that I could step the mast on top of the existing buoyancy tanks without cutting holes. If I had designed the boat with a sailing rig from the outset, I may have arranged things differently, but this set-up is quite simple (stays and shrouds can be made from Dyneema or Spectra if you like) and allows for the use of very simple, un-tapered spars.

Similarly, the sails have been located so that the daggerboard case can be positioned in front of the main rowing thwart. This means that retro-fitting an existing boat only requires the cutting of a slot in the bottom of the boat, without chopping into other parts of the structure.

I haven't had any reports regarding the sailing performance of this rig, because to my knowledge, none have been tested. However, my feeling is that the boat would sail very well indeed.

As for your question about a simple lugsail option, I am very keen to have a look at the figures, but I suspect that it may be necessary to cut a hole in the buoyancy tank to instal a mast step and partner. I've got a lot on at the moment, but I'll try to get something done as soon as I can. Please give me a nudge if you don't hear from me in a reasonable time!

I hope this helps a bit,

Ross Lillistone  

Friday, February 11, 2011

Another Flint Launching

I've 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 I'm 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 Ken's 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 that's only because I didn't really do anything during winter and only got back into finishing it in October/November. As it is, it's not quite complete - I am in the process of painting it - I'll 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 - can't 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 don't think so but I am working it out as I go along.


Ken Newey
Ken's New Flint, showing her nicely made inwales. Boat yet to be painted

Thursday, February 10, 2011

New Periwinkle Launched

Graham Faulkner has launched his Periwinkle named Entropy. She is the first Periwinkle to to carry the gaff-headed Cat rig, and here is Graham's initial report: -

Hello Ross, Well finally she was launched. I picked a dead calm day and put her in at Poona, very light steering as we sailed out into a 5kn n.e drifter, perfect manners. Helm response was good, and pointing ability appears great., Tried out the 3.5 hp outboard and speed was impessive. Now out in the straits we could see quite a storm building from the south so we hoped for say 10-15 to give her a try on the shakedown. Well we had that and more.probably 20 but with little chop as the conditions immediately prior were calm.

On all points sailed well but I was not comfortable running square. Quite a bit of rudder pressure and the boom [loose foot] looked like it may sky so I backed off and ran a full shy. Also grannied rather than jybed in the 20knts. Mast bent at the head maybe 2" but the sail shape was generally good apart from a modification I will make at the throat [need to cut a bit out]. No indication of wanting to bury the bow although my crew and self were well aft.

Q. I need to find a way to slide the sail up and down the mast. At the moment I lace it on but that would be far to slow in the event of an emergency sail drop. Also difficult at sea standing on the foredeck. Any suggestions.

A friend on a cruising yacht took plenty of photos but they will take while to get back so for now a back yard photo and a sail down retrieval photo in the weather. More later  

Here is my initial reply: -

Dear Graham,

Thanks very much indeed for the photos and for the report.

To answer your question I would suggest mast hoops as the first option (either made from laminated timber, or made from rope like a quoit), with them being loose enough for the sail to always drop reliably. If that doesn't appeal to you, then I'd use a diagonal lacing pattern which automatically loosens off as the halyard is released.

There are two systems I know of which work well - see attached files. The pdf file is two pages out of Harold Payson's book, "Build the New Instant Boats" in which he describes a lacing method promoted by Phil Bolger. It works really well, but takes a bit of setting up.

The jpeg is a sketch I just did to explain the other method. Note that the diagonal lacing always comes back on the same side as it came around. You would expect it to pull the luff into a zig-zag shape, but it doesn't.

Regarding the downwind manners, the first thing I'd look into would be a vang, although that is an additional complication in the rig, and may cause problems fouling the side decks. N.G. Herreshoff used to use a diagonal sprit set between the mast and the boom to form a sort of vang that worked in compression rather than tension, using a snotter to provide the compression. I notice that they use similar systems these days on ocean racers, but the struts are hydralically controlled.

Periwinkle is a small boat, despite her length, and I'd be thinking about reefing for downwind work in those conditions. Lazy jacks and a jiffy reefing system make that sort of sail easy to reef, once you get the hang of it. By the way, with a narrow boat and a free-standing rig, it is absoloutely vital that the head of the sail is not allowed to swing out to more than 90 degrees to the centreline of the boat. If the head of the sail swings forward of the beam, you will quickly get out of control in what is called the "Death Roll". What hapens is that the head of the sail drives the boat over to windward, and it quickly leads to loss of control. I used to sail a Finn in competition, and if the head of the sail went forward of the beam it meant an instant capsise - it was over before you even knew it was starting! With an easily-driven hull like Periwinkle, you don't need much sail to make her get up to quite high speed in the sort of winds that you described. Reefing is the key.

I'm really looking forward to more photos if you get the chance, but in the meantime, I strongly suggest that you try one or other of the luff systems I've mentioned, and that you stay off the foredeck - as soon as she gets weight up forrard and up high like that, she will be quite unstable because of her fine forrard sections. However, those same fine sections make her a relatively dry, easily-driven, and soft-riding boat.


Ross Lillistone

This my rough sketch for Graham
More when information comes to hand