Boats for Sale
authorities say should be
guiding principles of
first in the requisites for consistent success, but it must be blended
with natural genius, imagination and much practical handling'
Norman L Skene
- Simplicate, and add more lightness.
- The first requisite of any practical
boat is safety, the second comfort, and the third speed.
Edson B Schock
- Other things being equal, the faster
boat is preferable. The hell of it is, other things are never
equal. John G Hanna
- Unless a boat, however small and
simple, is built in a shipshape manner , it is better not built
at all. William Atkin
- Cinch up your belt, roll up your
sleeves, and go ahead and build it, regardless of hell,
hurricanes, and high prices. It'll always be worth the cost, as it
always was. John G Hanna
- A man needs a foot of boat
waterline for every year of his age. Traditional, repeated by Uffa Fox.
based on one's own study and experimental work, is really the keynote of
success Norman L Skene.
- The centre of
bouyancy should be just aft of half way between bows and
stern - John Teale
- Flat-bottomed vessels need slightly
more centreboard area; round bottomed ones can get away with
slightly less - John Teale
- The beam of a flat bottomed boat
should be no more than half the length; if it is to be rowed or sailed,
the length should be two and a half to three times the beam -
- In wall-sided boats, making the curvature
of the sides equal to the curvature of the bottom ensures
that the water pressures at each surface are equal, and reduces eddying
and wake, and therefore drag. - Philip C Bolger
- In a ballasted craft, the weight of ballast
should be 40 to 50 per cent of the all-up weight -
- In clinker-on-frame boats, there should
be Ďthree strakes or three framesí of separation between joints -
- Don't concentrate ballast
amidships in a ballasted boat, or the craft will move unpleasantly, but
donít spread it too far, as that will turn it into a diver. A happy
medium is likely to be to distribute it over about the middle third of
the distance from stem to stern - T Harrison
- In small and medium-sized cruising
vessels, make the least freeboard about a tenth of the LWL -
T Harrison Butler
- For an inshore racer in primarily light
air conditions it might be wise to go to a prismatic coefficient of .525 Cp, while an all around cruising yacht would benefit from a
higher Cp, say... .54-.55 and an ocean racer from higher yet, perhaps
.56-.57. In any case, it is best if the Cp is a bit on the high side
since the penalty for having too high a Cp at low speeds is less
detrimental to performance than having too low a Cp at high speeds. As
well, the high Cp should be achieved by fullness aft, not forward, as
full bows have an adverse effect on performance.
curves of areas for the hull heeled at 25 or 30 degrees for an
easy bilged boat should lie roughly parallel to the curve of areas
upright, and fairness of diagonals is important.
- Wineglass sections throughout
the hull will give slack diagonals in a chunky boat - and that's good!
- Suitable beam in a
round-bottomed cruising boat should be found from the formula square
root beam=cube root LWL - T Harrison Butler
- To minimise wave-making, (i) the length on the waterline should be as great as
possible; (ii) there should be no parallel body; (iii) the curve of
areas of cross section at the waterline should increase smoothly to a
peak just aft of amidships and then decrease similarly smoothly, tailing
off at both ends; (iv) there should be no abrupt changes in the shape of
the of the cross sections, although planing vessels are an exception to
this; (v) in sailing craft, conditions (i) to (iv) should be met also at
heeling angles of up to 15 to 20 degrees.
John F Sutton
is only when the topsides stand high above the water that your straight-sectioned boat looks 'boxy.'
- To be successful,
a self-draining cockpit should be at least eight inches above
water level... The minimum leg room is held to be 15 inches.
- Expense: Never use expensive materials to build a boat designed to be cheap; also
it is bad business to design a cheap looking boat that will be expensive
to build. Philip C Bolger
- A straight,
nearly upright stem with a good depth of forefoot produces a dry
bow. Howard Irving Chappelle
- Issues of
form. To be dry, keep the weight away from the ends of the craft.
Also, to be dry a bow should pick up bouyancy smoothly as it submerges
and only needs a moderate flare - in fact a straight-sided Vee-section
will do. There is no advantage to a hollow entrance and a great width at
the sheerline. Carrying flare aft can contribute significantly to
dryness, however. Hollow should not be considered in anything but a
relatively long craft with a length of no less than four times the beam.
In craft with a large square stern, a raked transom with provide lift
when hit by a wave. Howard Irving
- The most seakindly boats
have between three to five beams to their length,
and a draft of one quarter to one half of the beam. they also had keels
that were significantly deeper at the stern than at the bows to prevent
any tendency to broach in a following sea.
Howard Irving Chappelle
'In his experience as a designer, this 'drag' in a keel reduced the
tendency to broach even in very square sterns,' he added.
- Balance is
important - for example a narrow and deep hull combined with a wide and
shallow stern is undesirable - but in motorised fishing vessels, at
least, this balance of the hull neet not be precise and does not on its
own justify a canoe stern. Howard Irving
boats may seem dry, but this is only because they cannot be made to
move quickly in a seaway. Howard Irving
wave-bridging boats may be more seakindly than other types due to an
air cushioning phenomenon. To be effective they should bridge three or
more wave crests. Figure the length between wave crests and build the
boat at least three times longer than that.
Philip C Bolger
- Length should
be at least 6 times beam. 10 times beam is better... at about 14
times beam the energy saved in smaller immersed cross section begins to
be exceeded by increasing surface friction
unballasted small craft design, try this Start the design as a
flat-bottomed double-ender, making LOA/beam= 4/1. Other types can be
developed along the lines of Matryoshkas (Russian dolls). A dory can be
created by taking the double-ender and replacing the stem aft with the
triangular 'tombstone'. On this basis, a 16ft double-ender becomes a
15ft 3in dory (LOA). A skiff can be created by removing a quarter of the
overall length of the double ender from the stern and plugging the hole
with a transom board; this makes the LOA/beam 3/1. The punt can be
developed from a skiff by lopping 1/8 LOA fore (again measured from the
original double-ender), with the resulting hole plugged by a bow
transom. A dinghy is a punt shortened still further from the bows. A
pram is a still more shortened dinghy. These figures are not absolute.
The trick for each development is to stay in the confines of the same
sheerlines of the original double-ender - that is, the beam for the pram
is still 4 ft if the original Double-ender is 16 ft. Oh, I nearly
forgot. Make sure that sheer line of the original D-E is a NATURAL
curve, that is part of a circle arc. For hard-chined hulls, the circle
arc segment is set on the LOA as chord. The (maximum) height of the arc
is the hypotenuse of a right triangle of which the long leg equals the
half-Breadth at Beam (1/8 LOA). The short leg equals the Profile height
at Beam. The acute angle between the long leg and the hypotenuse equals
the flare angle. (Gardner, John 'The Dory Book' page 43).
- The Dinghy
Cruising Association, a largely British association of people into
cruising small open boats, has its own set of criteria for boats
regarded as suitable for this purpose. The criteria that apply to boat
design are as follows: (i) The boat should carry sufficient crew - one
stone (14lbs or approximately 6kg) for each foot of waterline length is
suggested as a minimum. (ii) The boat should be stable enough to allow
the recommended weight of crew to sit on the gunwale without dipping it
under or the craft capsizing. A beamy hull is advised, minima to aim for
with 12ft, 14ft and 16ft dinghies would be 4ft 4in, 5ft 3in and 5ft 10in
respectively. (iii) The boat should carry sufficient positive buoyancy
to support itself together with stores and partially immersed crew, plus
a reserve of not less than 112lbs. This buoyancy should be so disposed
that it is possible for the crew to put the boat back into sailing
condition after capsizing or swamping. It should be stressed that
capsizing is not an acceptable proposition in a seaway due to the long
period of exposure that may ensue and the possible loss of stores and
equipment. In rough seas, recovery may even become impossible. (iv) The
vessel should have at least a foredeck. (v) Mast, rigging, fittings etc.
must be strong enough to withstand capsizing forces. (vi) Consideration
should be given to having the mainsail canvas a grade heavier than on a
similar-sized racing dinghy; at least this will ensure longer wear. The
mainsail should be capable of being reefed while at sea and the
possession of a storm jib is desireable on sloops. The
Dinghy Cruising Association
- A moderate amount
of rocker helps in waves by getting the center of gravity and the
center of the boat down low in relation to where the bow or stern enters
the wave. This keeps the bouyancy in the bow and stern up high and it
allows the boat to rock fore and aft easily in response to waves. The
downside of rocker is in loss of speed, however moderate rocker is
acceptable for most boats. Tracking is also affected. To compare
extremes, guideboats are dories optimized for rowing and salmon fishing
on the Columbia river, which has a nasty sandbar and surf where it meets
the Pacific. These boats have a great deal of rocker and are made for
playing in the surf. A rowing scull is built for flatwater and speed,
with a hull approaching a semicircle profile and no rocker whatsoever.
This hull has very low resistance and is extremely fast but unstable in
waves. Paul Van den Bosch,
proprieter of The Guide to Sailing and Cruising Stories
- A 23' catboat is a one-portlight-per-side
size; two would be an affectation. William Garden
- Double the fiberglass overlay on chines centerline and sheer to reinforce these stress points. Over-zealous
sanding on the easy-to-do corners is a major cause of glass overlay
cracks. William Garden
- In selecting a rowboat, remember that a
265-pound Whitehall is too much for pleasure rowing... About 100 pounds
is the limit for enjoyable rowing. William Garden
- The first rule of economy is deletion,
and the second rule is substitution.William
- Nail where you can, screw where you
must, and bolt where you have to.RD
- A boat without flare is like a ship
painter's pontoon, and about as handy underway.RD
- Creating the perfect line means using
the eraser again, and again, and again. F S Kinney
- My experience is that the initial drawings
should be hand drawn, but then I am a technophobe when it comes to
the electronic drawing board, and chewing on a mouse is not nearly as
satisfying as a pencil. John Welsford
- A small boat of traditional flavour is in
reality a caricature , to get the features that say 'trad' and
give the boat its flavour there needs to be subtle exageration and this
can be hard to achieve without either over or under doing it. The
designer has to pick out those characteristics in the 'parent' that make
it memorable or induvidualistic and translate those into a form that
says to the viewer, 'look at me, I'm going to be like my daddy when I
grow up!' John Welsford
- The keel, stem and stern post of a
lapstrake boat should be twice the thickness of the planking, plus the
thickness of the stem bolts, plus 1/8 inch.RD
- Never glue the strakesof a lapstrake
boat. RD Culler He's
referring to traditional lapstrake, not to the epoxy plywood lapstrake
we see today.
- The Trapezoidal Rule for finding the
wetted area of a hull: Divide the underwater hull into any convenient
number of slices, and measure the length of each of the lines. Then add
the lengths of the lines together, remembering to halve the value of the
first and last of these lines. To a fairly close approximation, the
surface area will be this total multiplied by the distance between the
slices. Traditional wisdom
Outside of racing (and maybe rowing), I have yet to understand why this
is thought to matter so much.
- (About a 16', 8mph power boat) The deadrise
is approximately contstant throughout the bottom sections, a feature
that, assures (all values being equal) an easy and comfortable boat in
rough water. William Atkin
- A 7-in coaming coaming for even small
boats is not too high. John Illingworth
- Regardless of the volume of the (self-bailing)
cockpit, the drains should be large enough to drain it completely in
three minutes after it is filled to the coaming. To prevent flooding of
the cabin should the cockpit be filled, the sills of the companionways
should be no lower than the lowest point of the coaming.
C William Lapworth
- To be successfully self-draining, a cockpit
should be at least eight inches above water-level, yet in must not
be so shallow that it is virtually a box for the feet. ... The drains to
empty it must be of at least 1 1/4-in. pipe.
Des S is still around and writing entertaining columns for a couple of
- It must be mentioned that built-in buoyancy
should never be more than a last resort. First comes design, and a
hull that just cannot be swamped in a knockdown.Des
Sleightholme He's talking about
trailerable cruisers, not dinghies. I very much like his 1963 book
'Pocket Cruisers: A New Approach'. I take it that 'just cannot be
swamped in a knockdown' means a structure designed so that any openings
in the boat are likely to be well above the waterline in a knockdown.
- 'Through the kindness of MV Brewington Jnr,
the Bay rules for building skipjacks are available. They are as follows:
the greatest beam is one-third of the length on deck, and is located
between one half and two-thirds of the length on deck abaft the stem.
The width of the stern is about three-quarters of the greatest beam. The
flare of the sides varies from 2 inches to 3 inches for each foot of
depth amidships, according to the practice of the builder. The mast step
is located one fifth or one sixth of the length on the waterline, abaft
the stem, varying somewhat with the size of the boat, and the mast rakes
about 75 degrees to the lwl, the masthead coming directly over the
greatest beam. The length of the mast is equal to the length on deck
plus the greatest beam. The length of the bowsprit outboard is equal to
the greatest beam. The length of the boom is equal to the length of the
hull on deck. The length of the centreboard is one-third the length on
deck, and is placed in the middle third of the aforementioned length;
the board does not appear above the deck.' Quote from
Howard L Chappelle
- Side decks should be a minimum of 15
inches in width. With anything less it may be wiser to put the deckhouse
right out to the side of the hull. F S
- Metals used in wet conditions may
create electrolytic actions that may eat away important hull components
- the only way round this is to use together only metals that are close
to each other in the galvanic series. Starting at the most noble end of
the range, the series runs: mercury and mercury paint, vanadium, gold,
silver, monel, nickel, passive stainless steel, silicon bronze, copper
and copper paint, red brass, aluminium bronze, gun metal and Admiralty
brass, yellow brass, phosphor bronze, manganese bronze, tin, lead,
active stainless steel, cast iron, wrought iron, mild steel, aluminium,
cadmium, galvanised iron and steel, zinc, magnesium.
A truth discovered and rediscovered through
thousands of unfortunate experiences.
- You can complete your project on time, or
or under budget. Never both. John
- The centreboard should be about 4 per cent of the sail area.
- There should be about 1sq ft of centreboard
area to 40sq ft of sail area; in light craft the rudder area should
be half this, while in heavier craft it should be still smaller.
John F Sutton
- A rudder area of between 8 and 10 per cent of the total
lateral plane or underwater profile is the desirable size for a
sailboat. F S Kinney
- A foil should reach its maximum thickness about a third of
the way from the front edge. unknown
- On foils, I have experimented with all sorts of stuff and
come back to this simple formulae. For a non racer centreboard, the
thickness should be 12% of chord, the leading edge radius should be
1/6th the thickness, the maximum thickness should be at 40% back from
the leading edge, the trailing edge should be square across 5% of the
maximum thickness. Make a nice fair curve from leading to trailing edge.
This gives a high lift section with a very high stalling angle which
will assist the boat to tack reliably in very light or very rough
conditions when the low drag sections tend to stall and lose lift. It is
also not prone to damaging the leading edge if you hit anything. It is a
thick section, though, and on some boats would not fit the centrecase
and you may have to scale the proportions down to suit the thickness
available. John Welsford
- In general, a centerboard is not a desirable feature unless a
boat is to be used in an area that requires shoal draft. Also, the
rudder on a centerboard boat should not extend below the maximum draft
of the rest of the boat with the centerboard raised.
James A McCurdy
- Any rig her owner likes to work is the best rig.
John G Hanna
- No boom should be twice the beam to avoid tripping the boat
up. Philip C Bolger
- Boomless sails need at least 10 degrees of beam to work,
preferably 12. Philip C Bolger
- The effective centre of effort of boomless sails is somewhat
aft of where an equivalent boomed sailís would be .
Philip C Bolger
- Donít make the narrow angle at the top of a triangular sail
too narrow. If itís less than 27 degrees, the sail maker will not be
able to get any shape into it. Philip C Bolger
- Cutting a small convex curve shape into the luff of a
square-shaped sail is a quick and cheap way of getting a good shape.
- Sail area can be estimated using the following formula:
(Ballast in tons x distance in feet from the centre of gravity to the
(Sail area in sq ft x height of centre of effort in feet above the
metacentre) = R
- where R is some value in the range 16/10,000 to 24/10,000.
T Harrison Butler, attributed to
Admiral Alfred Turner
- The sail area of a 14 foot cruiser
should be 150sq ft; for a 16-footer 325sq ft; and for a 20 footer, 525
sq ft. From a graph published in Elements of Yacht Design by
Norman L Skene
- Stability is the engine of the sailing vessel.
- The appropriate
sail area of a vessel varies with its displacement in tons
squared and then cube-rooted times a fudge factor constant. A vessel
with 0.25 tons displacement will have a sail area of 100sq ft, one of
0.5 tons 150 sq ft, 0.75 tons 190sq ft, 1 ton 270sq ft.
- On a sloop the headsail
should have about 50 per cent of the area of the main, and
on a cutter the headsails should have about 70 per cent of the area of
the main. John Teale
- The centre of
effort of a triangular sail will be found on a vertical line about a
third of the distance from the mast along the foot of the sail. The
height of the centre of effort will likewise be on a horizontal line
third of the way from the foot of the sail to its head. This only works
if the rake is negligible. Lew, of the
boatdesign mailing list
- Good balance
can be achieved by placing the centre of gravity of the sail plan
directly over the centre of lateral resistance, or perhaps an inch or
two ahead of it. John F Sutton
- For balance,
The lead of the centre of effort over the centre of lateral resistance
should be 12-14 per cent of the waterline length in the case of a
shallow hull, fin keel or centreboard craft; about 10 per cent for
deeper, more traditional yachts; and about 8 per cent for cruising
yachts of classic form. John Teale
for racing machines of the scow type the lead of CE over CLR should be 5
to 15 per cent of the waterline length; for shoal, full-ended
centreboarders, the lead lies between 7 and 11 per cent. For full-ended
keel boats the lead is generally a little less; for cruising boats of
normal form it is about 6 per cent. Norman L Skene
- To achieve balance, the correct lead of CE over CLP (=CLR?) as a percentage of
LWL is 7-12 per cent for a schooner; 11-14 per cent for a ketch; 12-15
per cent for a yawl; and 13-17 per cent for a sloop or cutter. He seems
to be talking about conventional designs in conventional sizes (say over
10 feet LOA).Dave Gerr
(The Nature of Boats, p301)
- In flat-bottomed
boats, putting the CE directly over the CLR seems to achieve good balance
just about every time; however it is different in boats with
a deep vee-section near the bows. Jim
- L Francis
Herreshoff used to place the sailplan
centre of effort of a conventional sloop to produce a lead of
about 7 per cent ahead of the centre of lateral resistance. However, he
listed several factors that might affect a sailing craft's balance.
(i) Hull shape. A deep,
vee-shaped forefoot will obviously increase lateral resistance near the
bows. However, in a yacht in particular you should also consider the
lateral resistance of the heeled hull shape - it may be, for example,
that at 15 or 20 degrees the bows have no grab, but the stern is
beginning to put up significant lateral resistance.
(ii) Sharpness of the bows.
As a sailing boat heels, there may be a large flow of water from the
lee-side to the weather side of the bows. This tends to turn the bows up
to the wind - by how much depends upon the sharpness of the bows.
(iii) Due to the shape is
presents to the water, a wide shallow boat will tend to head up to the
wind on heeling, while a deep narrow boat will tend to turn off the
(iv) Increasing amounts of
draft in a sail will tend to move the effective centre aft. (This is
especially noticeable in the case of ice yachts, apparently.)
(v) Where the sail plan is
divided into many sails, as in the case of a schooner, the effective
centre of effort moves far less than when there is a single large sail,
as in the case of a catboat.
(vi) The height of the sail
plan. As a boat with a high rig heels, the centre of thrust on the rig
moves outboard, again tending to turn the craft up wind.
How much allowance should
be made for each of these factors? Think about each one and employ a
sense of proportion, says Herreshoff, helpfully, for this is not
mathematics but pure art.
- Balance, againThe
shape of the leading edge of the keel is one of the chief factors in
determining the balance of a boat. If the edge is sharp the forward part
of the boat tends to bite into the water and hold its position, whereas
a a rounded or blunt leading edge will tend to slide off sideways when a
boat is sailing to windward - so what we might call the true centre of
resistance is further forward inn a boat with a sharp leading edge than
it would be in the case of one with a blunt leading edge. In other
words, we can't really know where the centre of balance is likely to be
without doing tank tests. F S Kinney
- The diameter of a
traditional solid wood round boom should be 0.02 of the boom
length. For a loose footed sail, it should be 0.022 maximum, tapering to
0.02 at the ends. The diameter of a solid wood gaff should be
0.017-0.019 of gaff length. John Leather.
- The best
proportions for a gaff mainsail are luff 1.0, head 0.833, leech
1.73, foot, 1.02. The angle of the gaff to the centerline of the mast
should be 30 degrees. The rake upward of the boom should be 6 degrees.
If a topsail is to be carried, then the angle of the gaff should be
eased to about 42 degrees. John Leather.
- The simplicity of
the cat rig is a recommendation in itself.
William and John Atkin
- For singlehanding
a large boat and therefore obliged to split up the
rig, I would have a ketch with the area of the mizzen about two thirds
of the mainsail, and the mizzen mast stepped about as far forrard as
practicable. There would then be some chance of the vessel working to
windward under mizzen and headsails in heavy weather.
F B Cooke .
- The permanent backstay
should be designed to clear the end of the boom regardless
of how high the latter may rise in jibing.
William and John Atkin
- I believe only a
solid stick (mast) has any place on a gaff-rigged boat.
- A good figure to
aim at for important shrouds is to have the cap or upper shrouds make an angle of 14 to 15 degress with the centre-line of the mast.
- A cook's first
need is somewhere to put things down.
- Sail area is
modest in the small cruiser simply because the buyer cannot be
trusted to reduce sail to a safe area when it begins to blow.
- The length of
an oar should be of half the beam (from lock to lock) times three,
plus 6 inches West Marine
the length of an oar from lock to grip should be half the beam
times three, plus 2 inches John Vigor
- The calculation
of oar length for one of my boats is based on a movement at the
hands of only 700mm. The theoretical cruising speed of the boat is then
worked out by taking the square root of the boat's waterline length in
feet (Imperial units of measurement are good for some things) and
multiplying the result by a figure between 1 and 1.4... A short fat
heavy boat will be close to 1 while a really long light slippery boat
will be at the other end of the scale. This jiggery pokery tells me how
fast the water will be moving in relation to the boat, and by applying a
slippage factor appropriate to the oar type, about ten to twelve per
cent for the narrow blades I use, I can work out the shaft length needed
to move the blade at the right speed when the handle is stroked through
700mm25 times per minute. John Welsford
See John Welsford
- In the context of
small boats, the oar length should be about 7ft - at that length,
in beamier boats the 'gearing' changes appropriately.
Jim Michalak See Jim Michalak
- In a boat
designed for adults, rowlocks should be about a foot astern of
the thwart or seat that will be used for rowing.
- A length of 5
inches is about right for the grip. Never use a keg shape, but
give the grip a taper of about 1 1/4 inches at the inboard end tapering
to about an inch next to the swelled part of the oar.
- Build settee
berths with a slight hollow, and 1in fall outboards. This will do
wonders to keep the tired mariner off the cabin sole.
- Key internal
dimensions The minimum possible headroom for any cabin is 4ft, to
maintain sitting headroom on a 12in seat. The minimum headroom over any
seat is 3ft. This is measured from the top of the cushions. The height
of any seat from the top of the cushion to the floor should be between a
maximum of 19in and a minimum of 12in. The minimum width of any seat
should be 12in, the usual is 16in. The usual dimensions for seats to
sleep on, or for berths, are 78in in length and 30in in width. The
minimum is 72in in length and 21in in width.
- For cabin
ventilation, the total intake area in square inches = beam x
waterline length (in feet). Rod Stephens
- The cramping
of hatches, skylights and companionways only tend to emphasize the
smallness of one's craft, whereas if these openings are held to
comfortable proportions or even accentuated in size, they suggest the
ship rather than the tabloid cruiser.
Federic A Fenger
- It is important
to assume, I think, that at one time or another your boat will be
completely submerged and/or capsized, and, to be extra safe, that it
will be filled with water. So you need a boat capable of coping with
each of these possibilities. Robert
Manry, skipper of Tinkerbelle
- The minimum
power for the eighteen-footer is about 1.5 hp giving around four
knots in smooth water; this is barely sufficient if she is to punch a
tide against a head wind in order to get back up-river to her mooring,
but under sail and motor it is practicable.
- Murphy's law for
boatbuilders is that you won't find your mistake until the glue
has set, and Welsfords law for boatbuilders is that the mistake that
can't be fixed with lots of epoxy and fibreglass hasn't been born yet.
- In glue and
dust, and God we trust. Traditional
prayer of boatbuilding apprentices
- Cut on the
wastewood side lad, cut on the wastewood side! And always measure twice
and cut once. Traditional