Monday, February 27, 2012

Fleet - a Planing-Hull Version of Flint

Back in about 2003 I was asked to design a rowing/small outboard boat for operations in a short, steep chop, with the emphasis on lack of pounding. The resulting boat, named Flint, has been very successful and popular. She is very easy to build - if you follow the assembly sequence - and a distictive feature of her hull is the fine, hollow sections in the forward part of the boat. What is amazing is that this shape can be produced from a single developed plywood panel. I have tried to achieve this sort of shape in the past using conventional projection of developable panels, but the geometry required to produce a hollow shape has always defeated me. The arrival of computer programs which have the ability to do the mathematics saved me from myself!

Proof that the hollow sections come from a single panel of plywood
The very first Flint, built by Eddie Guy
In recent times I have been approached by a number of people who have wanted to build a planing version of Flint. The hull of the original rowing/sailing/small outboard version is of the displacement type, although her fine sections and high length-to-breadth ratio mean that she can be pushed faster than her theoetical displacement speed which is 5 knots. On launching day we got her to 6.1 knots with two adults and two teenagers onboard, using a 2hp Yamaha at part throttle. Steve Dorrington got his to a speed of 6.2 knots under the urge of British Seagull 40-plus - certainly an achievement!

Steve Dorrington measuring his 6.2 Seagull-knots using a GPS. Note how Steve has to sit on the midships thwart in order to retain proper trim. In the case of the planing version, a helms-person should be able to sit aft and operate the outboard without a tiller extension.
Bruce Erney, on the east coast of the USA modified his Flint to take a 6hp motor and got her up to 17 knots, I think, but he needed to put trim tabs on to overcome the tendency of the displacement hull to point her bow at the sky. I was concerned about the exercise, but Bruce had many successful trips while fishing in the big waters.

Bruce Erney's trim-tabs

One of Bruce's many fishing trips in his modified Flint

I've made a number of attempts at drawing a planing version of Flint and things were brought to a head this week when a friend/customer for whom I have great respect, asked me for a semi-disposable planing power boat which he and a friend could build over a weekend or two, to be powered by a 5hp outboard. He looked at few drawings I had on hand, and chose a preliminary sketch of a planing version of Flint, which I drew as a discussion piece for Rick Hayhoe a number of months ago.

Lines Drawing of the original Flint
Lines drawing of the planing version, now called Fleet
In the above drawings you can see the substantial changes made to the shape of the hull aft of the midsection. I have retained the fine, hollow forward sections, although I've increased the rake of the stem very slightly in order to reduce the severity of the bending and twisting of the plywood panels. With good-quality ply the hull is easy to assemble, but some people still insist on using poor-quality sheets in order to save a dollar, and end up encountering problems - hence the alteration.

My aim with this design is to retain the extemely light and simple style of hull as seen with the original Flint, and to have her run efficiently with nothing larger than a 4hp motor. This is important in my part of the world because we can operate with up to, and including, 4hp without needing to register the boat. The customer wants to use a 5hp, and specifically asked for a water-shedding foredeck and side decks under which he can store fishing gear. He intends taking her into the open Pacific off the Queensland coast here in Australia, and so adequate emergency floatation is essential. His boat will have built-in buoyancy under the sternsheets (aft seating which extends aft in a horseshoe arrangement),  under the midships thwart, and under the large foredeck. We have not finalised details of the arrangement, but here is a very preliminary sketch with the decks and seating shown in blue.

Here is a very sketchy drawing showing one idea of an internal layout. The final version is a fair way off yet, I think. The decks have very pronounced camber to aid in water shedding (those odd looking bits at the bottom are just working drawings to establish the height of the inner edges of the side decks at each station). Note how the cambered foredeck makes the sheer look much flatter than in the undecked original - this is an optical illusion. 
This little article should give some indication of just how much the character of a boat must be changed when the mode of operation is altered. However, a completely open version with a very small motor may retain the spartan feel of the original, while still performing in the semi-planing and planing modes. When the plans are complete and the boat tested, I'll post more details. For those who want to read more about the original Flint follow this link and this link.


Sunday, February 19, 2012

Discussion about Transom Bows - Whimbrel-related

Back in December 2011 there was some animated discussion about the design of boats with a transom bow - in this instance the discussion related to my Whimbrel design - with a number of people expressing their concern about Whimbrel's bow transom being too wide and too close to the waterline. The feeling seemed to be that the bow would dig in on some points of sail, and would bash into the wave in a steep, choppy head sea, therefore slowing the boat, throwing spray into the air, and maybe causing wild steering running downwind.

This perspective shows Whimbrel's hull viewed from the starboard bow - you can see that the base of the bow transom is close to the waterline when the boat is heavily loaded.

In this drawing there are three different waterlines drawn - the deepest one with her at close to one ton of displacement, which would not be likely to occur. But even at that heavy displacement the heel of the transom is just above the static waterline.

My argument was (and is) that the boat was designed to be only seventeen feet long, and that she would be faster, roomier, and more stable - for the load-carrying ability specified - with the large bow transom. For some background discussion on this matter have a look at this post  . In fact, if I had been brave enough to withstand the negative comments, I would have made Whimbrel's bow transom vertical, as I am convinced that her performance would be superior if drawn that way. I must say the raked transom looks better in profile, but I'm sure the performance is degraded.

I often quote Phil Bolger in my discussions, and at the time of the Whimbrel debate I used one of his remarks about bow transoms.

Fieldmouse - scanned from a photocopy sent to a customer by Phil Bolger in October 1971. Note how the waterline is at the heel of the vertical bow and stern transoms.
Here is Phil's quote when discussing his Supermouse and Fieldmouse designs: -

"Raked transoms make a faster boat less badly stopped by waves if they are raked out from the given bottom length, but in that case the boat would be better still if the waterline were carried out to plumb transoms at the new overall length...." (Boats with an Open Mind, International Marine 1994)
The logic in this remark seems to be lost on most people, but the technical importance of this comment, and others, has obviously been understood by commenter, Graeme: -

"No corners painted by Bolger here - even on those square boats! ;-)

What's not to understand? Drawing the bottom (and waterline) out to be as long as the deck of an otherwise raked ends hull makes for a narrower stern and narrower bow at the waterline. The finer entry is less stopped by waves and less wet. The drawn out waterline on the same beam has higher theoretical speed. Importantly (never forget the several intricate ways Bolger stressed the virtues of "shallow", this is but one) it also has less draft, and so less resistance, thereby being more likely to achieve or exceed that theoretical speed.

It is in no way all about the bottom though. What is often passed by in what Bolger said is that it's the decks that raise hull cog, and Bolger viewed decks, rightly, as a penalty. Other considerations not withstanding, he may just have stuck to raked ends, clipper bows, and such, if he'd been able to design decks of weightless unobtainium. As it is, plumb ends (and sides) impose a smaller deck weight penalty on a given bottom, or on stability, or on ability to stand up to sail, or on overall performance.

Flow on efficiencies there, which may also continue to run right into the pocket.

No corners then, painted or otherwise, rather Bolger's genious yet again seen remarkably squaring a circle unlooked for. A virtuous circle spiralling on with yet more angles round each turn.

Graeme"


You can read other very interesting comments by Graeme and Rick at the end of this post.

Now, I am not saying that bow transoms are the answer to everything. Most of my designs have unusually fine, sharp sections up for'ard. In fact, I sometimes wonder whether I may overdo it in an attempt to cut down pounding in a short head sea.

The very sharp entry on Flint

Periwinkle has a long, fine entry.
What I am saying is that for certain applications, a hull with a bow transom may be the most appropriate way to design a hull to perform a particular function and if one of the design constraints is overall length, then a wide, vertical transom extending almost to the waterline should be considered.

Sunday, February 12, 2012

First Mate Side Seat Rails

At the end of June 2011, I published a post about my idea for moveable side seating in cruising dinghies. The idea is that side seats can be used if prefered (although I like to sit down low in the boat with my weight near the windward turn of bilge) and can also be removed at a moment's notice. Most importantly, if they are slid into the centre of the boat they make an excellent sleeping platform, well above the bilge water.

The Phoenix III built by Paul Hernes, showing the side seats in the standard location.............. 
...........and slid together to form a nice sleeping platform............
.....or removed altogether.
You can find my original post at this address

I am continuing to work intermittently on a First Mate in my workshop - she gets attention when glue is curing on other jobs. Last week I installed the rails to carry the removable side-seats/sleeping platform, and I'm delighted to say that in First Mate, the seats are more than 26 inches wide at the upper part of the body when slid together. Here are a few pictures of the rails: -

Here is the seat rail glued and screwed onto the aft face of the midships frame. This frame is made from 12mm (1/2") marine plywood, with 38mm x 12mm (1-1/2" x 1/2") behind where the screws go through. The whole thing is very strong, and the seat rail would be fine with just a glue joint. However, the silicon bronze screws make it simple to position when the epoxy is slippery, so they may as well go in! The rails are positioned to carry a side seat which is 31mm (1-1/4") deep - these will most likely be 25mm (1") framing topped with 6mm (1/4") marine plywood.
A close-up of the aft rail, which attaches to the semi-bulkhead at the forward end of the stern seat (i.e. the "stern sheets"). The centre cut-away is just to allow positioning of the screw-in hatch to that particular buoyancy compartment.

Another shot of the aft seat rail with the rowing foot-braces on the floor below. These foot braces do double-duty as structural stiffening elements as well

This seating arrangement will make First Mate (and Phoenix III) very versatile cruising dinghies - my favourite type of boat bar none!

Saturday, February 11, 2012

Little Egret Construction Progress

I'm sorry that it has been a few weeks since I last wrote a post, but I've been very busy with a whole range of activities - not just boat related - which have prevented me from sitting down to write. In addition I been feeling a bit blocked for things to write about. It isn't that there is a shortage of subject matter - it is just that depending on mood, I sometimes find it difficult to write in a way that I think is interesting to readers. I've been writing articles for every issue of a print magazine for the last twelve years, and now for this blog, and I can assure you that it isn't easy!

Anyway, here is a bit of what has been going on: -



Back in late October 2011, I mentioned that I was in the process of designing an "Egret-style" sharpie/dory for John Hockings in Brisbane, Australia. In early December 2011, I reported that John had commenced construction. Since then, John has been making very rapid progress and the boat is looking great. The photos have been taken with a relatively wide-angle lens so the boat looks smaller than she really is in the flesh.

Here is the hull viewed from the stern with gunwales, mast partners, mast steps, and centreboard case fitted. Side deck carlings are being sprung into place, with temporary cross-braces to hold them in against the twisting, bending, and edge-setting forces.
A photo from very early in the construction process which gives a good impression of the hull profile - bow is to the right of the picture.
A view of the interior during the application of a thinned epoxy (Norseal). The photo has been taken from the stern and you can see the mizzen mast location at the aft end of the centreboard case.  The floor timbers (transverse frames on the bottom) will carry floor-boards in the finished boat, allowing passengers to sleep above any bilge water, and to give a nicely textured footing during normal sailing and poling. Note the seat risers which allow positioning of thwarts in many locations.
One topside panel cut and material for the second one waiting to be worked on. The panel shapes are precomputed and dimensioned drawings are supplied with the plans, allowing the boat to be built without any sort of mold or strongback.
View from the bow, with the first undercoat applied. Mast step in the foreground is for the third mast location, which will take either the main mast or the mizzen mast, allowing the boat to be sailed with a single sail if desired.
Another photo of the boat being undercoated, this time viewed from the stern with the main mast partner visible in the background.
This boat is an exciting prospect as far as I'm concerned. She will be rugged and yet is an easy project for any capable builder. John has been doing an exceptionally good job of building her and I really look forward to seeing how she handles the rough stuff as well as the thin water for which she is very well adapted.

Monday, January 23, 2012

Which Boat Gives The Most Satisfaction?

This a re-print of a short article I wrote about 3-1/2 years ago. I still think it is worth a read. For those who are interested, the boats in the article are my First Mate design, and Phil Bolger's 30ft Romp.

In the late afternoon of a balmy North Queensland day, a man in his fifties sat in a small rowing and sailing dinghy, near the banks of a sandy estuary. It was not the great physical beauty of the mangrove-fringed inlet that was the object of his attention, but a clean-lined sailing cruiser of about thirty feet length-overall which sat quietly at anchor only a short distance from the sand.

As is always the case for those obsessed with boats, the man was constantly alert for the sight of something different from the normal run of fibreglass, stainless steel, and push-pit barbeques; and this particular vessel had caught his eye from a long way off. What was different about her? Well, she was free from the normal clutter of standing rigging, furled headsails, high cabin trunks and inflatables, and importantly, she was anchored in what appeared to be impossibly shallow water for a boat of her size. Above all, there was something about her character that struck him as familiar.



August and September are wonderful months way up north in the tropics, and rowing around an isolated estuary is good for the soul at a time when the sun is low – as long as you have your eyes open for crocodiles! This fellow had rowed and sailed in the particular location hundreds of times over the years, but it never lost its appeal as a sanctuary from his day-to-day work in the nearby city. His boat was a fifteen foot long plywood dinghy, fitted with the most simple of sailing rigs, along with a well-made set of leathered oars and bronze oarlocks.





The interior of the dinghy showed the evidence of frequent use – a collapsible crab pot in the forward space against the centreboard case, a large water container under the thwart, a camera in a waterproof case in a bucket aft and several sorts of other paraphernalia. The internal paintwork had endured its fair share of scratching, and the bundled sail carried grease and mud stains. But the boat was in a good, solid state of repair, and she looked like a capable sort of ship.

The man sat looking at the larger boat for several minutes, resting his hands on the handles of his nicely balanced oars. Then, with a few deft strokes, he spun the sailing dinghy in her own length and sent her in towards the sandy shore beside the object of his attention. As he passed close to the bow of the big cruiser, he noticed that the clear water was only about two feet deep, yet the anchored boat was definitely well afloat. As he continued to paddle along the length of the boat, it became apparent to the oarsman that the boat he was looking at had come from far away. She flew a foreign flag, and his experienced eye could pick the signs of a vessel which had traveled across oceans.

Stepping ashore on the firm sand, our friend dragged the plywood sailing dinghy up until she was safe from drifting, and then he pulled a wooden galley box out from under the main thwart and set a kettle to boil over an old alcohol stove. Had he been in a more exposed location, the man would have moved the boat much further up the beach, using the pair of inflatable rollers which were currently tied up under the side decks. The boat was light enough to be manhandled by him under most circumstances, and he was very grateful that he had resisted the urge to go for a bigger dinghy at the time of construction. To himself he said, “Just like Goldilocks – not too big; not too small; but just right”.

Returning his attention to the larger vessel, he studied her details once again. She had a plumb stem, with a beautifully sharp entry at the waterline, widening out rapidly to a wall-sided midsection which terminated in a shapely stern and a vertical transom of almost triangular cross-section. The overall shape of the boat put him in mind of pictures he had seen of Thames Sailing Barges, although this one did not carry leeboards like the barges. Because the boat did not have any cabin trunk (other than what appeared to be an oversized companionway shelter), the hull sides looked quite high. However, as he waded out to her in the knee-deep water, he discovered that his eyes were almost level with her deck-line, so appearances were deceiving and he could tell that this boat was much lower than the average production boat of her size.

Steam issuing from the kettle called him ashore, and as the man settled down on the sand to drink coffee, he felt the well-known demon of “Unreasonable Boat Desire” creeping up on him once again. This thirty-footer struck him as just about the ideal escape machine with her free-standing cat-yawl rig, one-and-a-half foot draft, centreboard and clean deck-line. That she was an ocean-going craft was beyond doubt, and he could see that in comparison with the average sailing boat tied up in a marina, she would be very cheap to build and maintain. In his mind’s eye he could see himself cruising the Great Barrier Reef, sailing to New Caledonia, reeling in large fish, weathering tropical storms without the slightest concern, and living out childhood fantasies related to desert islands and buried treasure. Oh no, it was all happening again…!

Now this fellow had a close friend who was known for his conservative (some would say, “boring”) views, and as he sat dreaming about the feats he could achieve in this wonderful ocean-cruiser, he could hear his friend’s voice-of-reason sounding in the back of his head. “Don’t do it,” the voice said, “you know the boat is too big.” He shook his head, but the phantom voice continued, “You know that a big boat will drain your financial and physical resources, and that you will get far more use out of your superb little sailing dinghy.” Still the voice droned on, “You can only just manage to keep the paint up to your little boat, you lazy so-and-so; how do you expect to maintain a thirty-footer?”

Turning to the right, the middle-aged mariner looked at his existing boat. She was light, and very good-looking. The rig was strong, simple, free-standing and easy to repair. As she sat on the sand he could see with great satisfaction that the lowered sailing rig lay nicely in a compact bundle to one side, well clear of his rowing position. Many times he had slept on-board, having set off after work to row or sail for a few hours before bedding down for the night on the sleeping platform he had fashioned inside the dinghy. With the boom tent rigged, he was well protected from insects and light rain, and the snug interior made him feel secure. After use, the boat could be tucked away in a corner of his shed until needed for the next mild adventure. Annual maintenance was minimal.



The afternoon sea-breeze being favourable, the sailor set the small boat’s rig (three minute’s work) and ran out of the inlet for an hour or so of sailing in the tropical evening, knowing that for him at least, the freedom provided by the small plywood dinghy was beyond price. He had built her with his own hands, and the cost had been tiny. The returns, however, had been enormous.


Sunday, January 15, 2012

Wildlife at the Boatshop

I'm starting the year's posts with a slightly off-subject entry. It is now six years since we moved away from our coastal workshop to live and work in Esk, Queensland, Australia. Although we only moved 100 kilometres (62 miles), the move was directly to the west - away from the coast. Many people thought we were mad, but we needed to locate ourselves in a quieter place, further away from the scores of casual visitors who had been in the shop at all hours. I like talking to people about boats, and I particularly enjoy explaining building procedures, and therein lay the problem. I was spending long hours in the shop, but not getting enough paying work done!

The old workshop in Wynnum. The office is under the sign at the far left, and workshop area extends to beyond the far right of the photo - it was a paradise!

Looking through the building from just outside the office. Notice the wooden floor and low ceiling - perfect for boatbuilding.
Well, moving into a rural area where horse-floats and cattle trucks outnumber the boats 500 to 1 may seem like a dumb thing to do, but we had our reasons (mostly financial). As it has turned out, we are very happy and enjoy the quiet surroundings. There is a 35 kilometre-long lake just down the road, and if we want to get to salt water it is only an hour-and-a-half by the highway.

The Esk workshop. Since this photo was taken there have been improvements, such as a concrete slab under the lean-to, but it is still basically 9metres x 10.5 metres (29ft x 34ft) of concrete under tin sheds, and a separate 6 metre x 6 metre storage shed. However, I work alone most of the time, assisted by my wonderful wife when things get tough, so I am pretty happy with what I have.
Inside one of the workshops
Being in the bush has its inconveniences, but the advantages outweigh the negatives many times over for a hermit like me. One of the significant benefits is that we get to observe native wildlife at close range, and come to take it all for granted.

Possum in a model aircraft
My wife with a totally wild Rainbow Lorikeet
Same fellow up close after eating apple
A King Parrot - once again, totally wild
A Koala ten paces from the workshop door
A buck Wallaby making friends with our cat through the front door glass!

For those of you who may be interested in Australian wildlife, here is a youtube video which I shot over the last couple of days. The quality is not high, as I didn't have a tripod, and there was too much backlight in some frames - but if you have never seen a Wallaby Joey in its mother's pouch, or seen a Koala climb a tree, take a look. All shots were taken within five yards of our door!


These photos may not show you how to build a boat, but I can assure you that the presence of these animals helps me to retain some perspective on what is important in life, and I'm sure that my building and designing benefits as a result.....

Friday, December 30, 2011

Periwinkle Video


Periwinkle was designed and built by me for her owner, John Shrapnel. She is a long, lean boat with very fine sections up for'ard to help her get through a head sea relatively easily, and without making her crew too wet. Towards the end of the video you can see how the fine entry allows the water to peel off the side of the boat rather than flying into the air to be blown over the occupants. The plank laps associated with the glued-lapstrake (clinker) construction also help tremendously in knocking the water down.

Although she is 17ft long, Periwinkle is actually a smaller boat than she looks, and she needs to be trimmed properly to get the best from her - she doesn't like weight in the bow, but all boats are compromises, and in this case the advantages described in the first paragraph make up for the attention needed regarding trim. In the video, John Shrapnel has her longitudinal trim perfect, sitting on the wide and comfortable seat just forward of the expansive aft deck and buoyancy compartment.

Large aft compartment and buoyancy/storage compartment

Room for sleeping, and note how the aft deck hatch is on the centreline, so even if the lid is open, water will not flood in during a capsise
The following video was shot on the east coast of Australia, at Caloundra, Queensland.


You can see more information about Periwinkle on my website here and here and here