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Topic: Hull speed

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	QCC Kayaks - Sea, Touring, Ocean Kayaks - Factory-Direct Kayaks (Site not responding. Last check: 2007-10-10)
		"This boat has a high hull speed." (few ever have a "low" hull speed) or "We were paddling at hull speed." are commonly used to imply that "hull speed" is a limit to displacement speeds and bloody fast at that.
		The speed corresponds to the speed of a wave having the same length as the effective waterline length of the hull.
		And, when others do, just point out that "hull speed" is a term of convenience referring to the speed at which the bow wave length and boat length are the same and that it doesn't have any real significance for boats of low displacement length ratios like kayaks.
	www.qcckayaks.com /resources/speakboat2.asp (939 words)

	Hull speed - Wikipedia, the free encyclopedia
		Hull speed is a common rule of thumb based on the speed/length ratio of a displacement hull, used to provide the approximate speed potential of the hull.
		Hull speed is typically not a term used by naval architects (they will use a specific speed/length ratio for the hull in question) but is most often found used by amateur builders of displacement hulls, such as small sailboats and rowboats.
		The hull speed limit does not readily apply to certain types of hull which are not primarily limited by wave drag.
	en.wikipedia.org /wiki/Hull_speed (636 words)

	Hull speed - Boat Design Forums
		It is given by the expression v^2=Lg/(2Pi) where v is the speed in feet per second, L is the length in feet, g is the acceleration due to gravity in feet/second/second and Pi is the circumference of a circle divided by the diameter.
		The so-called hull speed is a reasonable compromise and is often exceeded especially by small boats as the power needed is still relatively low and fuel is relatively cheap.
		As far as displacement hulls and semi-displacement hulls are concerned using a factor of 1.34 is merely coincidental to the boat length equally wave length.
	www.boatdesign.net /forums/showthread.php?t=1220 (4411 words)

	Hull Descriptions
		These hulls are like a half of a canoe, instead of coming to a point at the back they are usually cut flat across, and have a transom.
		These hulls look like trawler hulls, but the bottom is more complex, they have a lift built into the hull's bottom so that as the boat speeds up, the boat starts to lift out of the water.
		At hull speed the length of the boat is about equal to the wave pitch, the bow wave of the boat becomes larger, the hull is trying to climb up the bow wave, this cause a tremendous increase in power demand to drive the hull.
	homepage.mac.com /dalheid/BoatData/Hull_Descriptions.html (1094 words)

	Expensive Hull Speed. - Boat Design Forums
		Since most displacement hulls are speed limited by the distance between the bow and stern waves, they are limited to 1.34 x sq.rt.
		The idea of a "theoretical hull speed" is left over from the early theoretical work by Froude and Havelock and propagated by some magazines in the inter-war years.
		Most displacement hulls do not see a decrease in power in the hollows, but rather a "flat spot" where very little power is required to increase speed.
	www.boatdesign.net /forums/showthread.php?t=11342 (1224 words)

	Kayak Speed and Hydrodynamic Designs (Site not responding. Last check: 2007-10-10)
		Generally speaking, the speed of a boat is the result of the power propelling it forward (effective propulsion) and the resistance of the water to this effort.
		For example: the hull speed of a 20 ft boat is 6 knots and that of a 10 ft boat is 4.23 knots.
		Hull speed is by no means a final limitation on speed, and it's very common for boats, including human powered ones to go faster than their hull speed.
	www.wavewalk.com /COMPARISON.html (5064 words)

	Boat Docking - Mushing a planing hull power boat
		Hull speed is intimately related to and caused by the waves made by the hull - those waves being the "wake," of course.
		The formulas dictating hull speed are actually about wave-length - and at hull speed, the second in the series of waves called the bow wake is at the boat's stern.
		At slower speeds, the second wave is further forward along the boat's hull, and the hull may sit on two or three waves, bridging across their crests and troughs.
	www.boatdocking.com /other/Mushing.html (3803 words)

	Nordhavn (Site not responding. Last check: 2007-10-10)
		A displacement hull is designed to remain fully in the water throughout its entire range of speed.
		Requiring a fraction of the horsepower that semi-displacement or planing hulls require to attain optimum speed, a displacement hull in the 40 to 60 foot size will be capable of maintaining speeds in the 7 to l2 knot range while burning a minimum of fuel.
		This is the speed at which the hull makes a wave as long as its waterline, and it is the speed which cannot be exceeded without applying great amounts of additional power.
	www.nordhavn.com /design/full/full.htm (1059 words)

	How Fast IS a West Wight Potter? A New Look at Hull Speed.
		We've all heard that the hull speed for a P19 is 5.4 knots and for a P15 it's 4.6 knots.
		A hull is planing when it is supported by the water flow under her hull.
		They are restricted to the theoretical hull speed limit that is defined by the propagation of waves.
	potter-yachters.org /manyways/hullspeed (1233 words)

	M-hull
		For a displacement boat, the bow wave increases in amplitude with boat speed until propulsion power is insufficient to climb the wave (i.e., the hull speed limit).
		In sea trials of a boat embodying such a hull, the act of increasing power to test the advantages of the air planing cushion at higher boat speeds led to the discovery of two new phenomena.
		The first and second channels are adapted to capture a bow wave and to cause air and water to mix and spiral toward the aft end of the hull as compressed aerated water, thereby reducing friction drag, increasing lateral stability, and dampening transmission of bow wave energy at the aft end of the hull.
	www.globalsecurity.org /military/systems/ship/m-hull.htm (1111 words)

	Powering of Hulls - a discussion. (Site not responding. Last check: 2007-10-10)
		Thus at about 20 knots, this particular vessel's top cruising speed, one could expect the wave making resistance to equal 25 Newton per tonne, or, as she was a 12500 tonne vessel, a total of 312.5 kN.
		This particular vessel, a fast reefer, was fitted with a 16000 horsepower MAN diesel engine and achieved a speed slightly greater than 22 knots on her measured mile trials with a clean hull, standard displacement, ambient sea temperature of 12 degrees and an ambient air temperature of 19 degrees.
		It only pertains to displacement hulls and gives an approximation of the maximum speed a hull can achieve before the bow wave combines with the stern wave to dig a trough out of which the vessel would not be able to climb without using inordinate amounts of power.
	www.dynagen.co.za /eugene/hulls/index.html (1591 words)

	Kayak Wiki: Hull Speed (Site not responding. Last check: 2007-10-10)
		First let us note that hull speed is not an absolute limit on the speed of a kayak.
		Hull speed is related to the waterline length of the hull.
		This of course is the same as the speed of the hull.
	www.kayakforum.com /cgi-bin/wiki.pl?Hull_Speed (354 words)

	Why Would You Want a Mulithull Power Boat?
		This phenomenon is however exploited very sucessfully in the Formula 1 tunnel hulls and the large offshore racing catamarans where there is horsepower a plenty and the comfort of the passengers is relatively unimportant as long as they survive.
		If we look at the graph of fuel useage plotted against speed it is obvious that at low speeds of around 7 knots there is not a lot of difference between the four different hull types that are plotted.
		The displacement boat is getting close to its hull speed limit whereas the planing boat no longer has a wave drag determined hull speed limit in the same sense though even its resistance to motion will continue to increase exponentially until it to grinds to a halt.
	www.powermultihulls.com /magazine/articles/why-multihull.htm (1407 words)

	untitled
		While current record speeds are certainly within the upper limits of all hull types, we believe that the effects of these limits are being felt by displacement and hydrofoil platforms.
		While inefficient at speeds under 20 kts, this generates more efficient and predictable sideforce at 40+ kts in a chop than ventilation-prone conventional fins and hydrofoils in the turbulent air/water interface encountered at these speeds.
		As boat speed increases to equal true wind speed, (beta) must be reduced to 45° as the relative wind speed increases from Vt to 1.41 Vt.
	www.dcss.org /speedsl/ST89hulls.html (1565 words)

	HULL SPEED LENGTH RATIO CALCULATION AND ANY BOAT SHARE WARE CALCULATOR LINK - SOLAR NAVIGATOR WORLD ELECTRIC NAVIGATION ...
		This is a handy rule whereby boat speed in knots (V) is compared to hull waterline length in feet (L) where V divided by the square root of L = the speed/length ratio or S/LR.
		For the 300 footer to be considered high speed she would have to be traveling (work formula backwards) V = 3 x 17.3 = 52 knots or more.
		However a third more important set, runs along the vessel's side which, depending on the speed of travel, produces a crest of water at the bow lifting the boat, followed by a trough into and then another crest, etc. The faster a boat moves, the bigger the crest lifting the bow out of the water.
	www.solarnavigator.net /hull_speed.htm (670 words)

	BENTLEY Yachts Advanced Hull Designs (Site not responding. Last check: 2007-10-10)
		As speed is increased, the lifting force generated by the water flow over the submerged portion of the foils increases causing the ship to rise and the submerged area of the foils to decrease.
		Speed Z drive systems with variable pitch propellers facing forward that catapult the vessel to speeds of 50 knots (90 km/h).
		At that speed the hull is lifted 2.3 m out of the water and the vessel is run with a "fly-by-wire"-computer controlled system which adjusts the five movable foils.
	www.yachtboutique.com /BentleyYachts/Advanced_Hulls.htm (2627 words)

	Boats and Speed - BoatSafe Kids!
		In other words, as it floats in the water if you were to mark the point on the bow where the water touched and marked the point on the stern where the water touched and then measured that distance this would be the waterline length.
		By the way, if you were to connect the marks you made at the bow and stern and paint a line on the boat's hull you would have created what is called a "boot stripe".
		It is at this point that the boat has reached its "hull speed".
	www.boatsafe.com /kids/speed.htm (564 words)

	Hull speed formula and chart for rowing type boats.
		Hull speed formula and chart for rowing type boats.
		Displacement hull speed is an important indicator of how fast a displacement-type boat will go.
		It is the speed at which a boat begins to climb it's own bow wave, essentially going uphill.
	www.frontrower.com /hullspeedchart.htm (99 words)

	Skills - How to Choose the Right Canoe Hull
		Flat-bottomed hulls are used in sport and cottage-type canoe hulls because their stability makes them good for fishing or for novice paddlers.
		When choosing a touring, expedition or sport canoe that will be paddled tandem and solo, the hull should be symmetrical (the shape of the canoe is identical fore and aft) and the bow seat located twice as far from one end of the canoe than the stern seat.
		Solo whitewater playboats need their pedestal or saddle mounted so that, when the paddler is sitting in the canoe with his or her accessories stowed in their normal places, the hull is trimmed with the bow riding 1/2" to 3/4" higher than the stern.
	www.paddlermagazine.com /issues/1999_3/canoehull.htm (1360 words)

	Kitesailing International 10/88
		We now orient the hull 70° higher that the kitelines' pull and "viola!" we see that we are sailing at an angle of 45° from the wind, upwind.
		A kite rig, which is independent of the hull, can accelerate to several times the wind speed before the hull begins to move (and thus the characteristic zig-zag or figure eight course of the kite stack).
		While this advantage decreases as hull speed increases, it is very useful at slow speeds to, for instance, bring a planing hull or hydrofoil supported hull up onto its feet.
	www.dcss.org /speedsl/KI1088.html (1902 words)

	[hpv-boats] Speed Bumps and Hull Speed
		The test speeds for which I am planning to test for drag, in knots, are 3, 4, 5, 6, 6.5, 6.75, 7, 7.25, 7.5, 8, 9, 10, 11, 12, and flank, which I think is 12.5 knots on the powerboat.
		The new water attacking angle is a function of the a hull wave's amplitude, which is in turn a function of a hpb's displacement vs. water line length.
		The hull speed for a 20 HPB, such as mine, is 6.71 knots.
	www.ihpva.org /pipermail/hpv-boats/2002q1/002331.html (1511 words)

	Wave Resistance of Ship's Hulls
		So this model hull would have an expected 'yachties hull speed' of 2.7 m/s (27 knots for the real ship), which doesn't really correlate with any obvious feature on the resistance curve.
		Michlet assumes that the hull sections given are fully immersed, so this is the bit of the hull actually in the water.
		The baseline hull in this graph is NOT the hull used for correlation above.
	www.geocities.com /greglocock/hullres.htm (1378 words)

	Hull (watercraft) - Wikipedia, the free encyclopedia
		Beam or breadth (B) is the width of the hull.
		Depth (D) is the vertical distance from the bottom of the hull to the uppermost edge at the side.
		Hull construction then proceeded to keeled hulls, use of ballast, and on to modern double steel hulls with watertight compartments.
	en.wikipedia.org /wiki/Hull_(ship) (1379 words)

	V14 Hull Speed (Site not responding. Last check: 2007-10-10)
		A boat's LWL (Length at Water Line) is equal to the distance between the wave crests created at the bow and stern by the boat's motion through the water.
		A boat rides in the trough between the two wave crests when it is at it's theoretical maximum hull speed.
		Planing hulls, such as centerboard dinghies, are capable of exceeding their theoretical hull speed when they achieve a planing attitude.
	home.comcast.net /~vagabondsailing/VHH_Hull_Speed.html (227 words)

	Hull Design
		The hull design will be concerned with canoe body resistance, each of it’s three resistance components must be considered at a variety of speeds.
		Wave drag is a complex function of the hull’s shape but in general slender and sleek hull forms tend to have a low value of wave drag.
		This is the speed range that is hardest to design for as the hull is neither in a displacement or planing state.
	www.mothboat.com /USMMCA/Building/hull.htm (1356 words)

	Heavy Boats, Light Boats, and Hull Speed - Antrim Associates Naval Architects (Site not responding. Last check: 2007-10-10)
		When a boat reaches "hull speed" the bow and stern waves coincide to make one huge wave system.
		When they reach the speed that would be hull speed for a heavy boat the wave system is not big enough to trap them.
		A planing hull actually climbs up its own bow wave and is lifted partially out of the water.
	www.antrimdesign.com /articles/hullspeed.html (404 words)

	MEASURING HULL DRAG AND CALCULATING HORSEPOWER REQUIRED FOR LOW DRAG HULL DESIGNS - SOLAR NAVIGATOR WORLD ELECTRIC ...
		It is a relatively straightforward matter to arrange to tow the target hull using a spring balance to measure the pound-force or kilogram-force required at different hull speeds.
		The speed would be most accurately measured by recording the elapsed time over a measured distance (two points at least 10 meters apart).
		What they forget is that the power required increases approximately as the cube of the hull speed, so that very small speed increases need major power increases, as the boat speed approaches its hull speed.
	www.solarnavigator.net /hull_drag.htm (1265 words)

	Schoell Marine, Duo Delta Conic High Speed Planing Hull
		The forward hull creates a bow wave under the hull, along the aft hull to "ride the wave".
		As speed increases, the wave moves aft thereby lifting the stern.
		As planing speed is achieved air is vectored under the running section thereby reducing suction loads, as illustrated in the graph on this page, The forward and aft hull planes at optimum angles.
	www.schoellmarine.com /conic.htm (200 words)

	Speed Dating Hull - Speed Date Events in HUll, UK
		Speed Dating is a fast, fun and effective way of meeting new single professionals in the Hull area!
		Smart Dating UK had a fantastic speed dating launch in Hull at the popular Lloyds No1 Bar in Trinity Lane in March 2004.
		We are planning on running speed dating events on a regular basis as demand increases.
	www.smartdatinguk.com /speed-dating-hull.asp (339 words)

	M Ship Co. \| Technology Index \| Next Generation Hull Technology
		These designs may overcome the limitations of conventional hull forms and allow ships to perform over a broader range of operating conditions and missions.
		The hull geometry and the captured air plenums of the M-hull allow a ship to automatically and naturally seek the most efficient form of lift depending on speed, payload and sea condition.
		This remarkable characteristic is already demonstrated on several small vessels, and the scalability of the design by combining two or more M-hulls side-by-side holds promise for a new breed of large military craft.
	www.mshipco.com /index.php?page_id=3 (438 words)

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