Bow Shape

Discussion in 'Sailboats' started by SuperPiper, Aug 23, 2013.

  1. David L. Dodd II
    Joined: Jun 2020
    Posts: 20
    Likes: 13, Points: 3
    Location: New York

    David L. Dodd II Junior Member

    I am just going to write a quick primer on bow shapes. This primer is based on my years of research into sailing, and actual sailing. I have been spending the last several years working on a design for a cruising boat which I will be starting to build shortly. Of course any one is free to disagree with me on any statement made. In fact, I welcome any opinions regardless of whether or not they agree with me

    First, I wish to say that bow shape influences and is influenced by every other design feature on a boat or ship. Nothing can be said about just the bow alone, so often discussions of bow shape will lead to discussions of other features. I endeavor to keep this to a minimum but it is unavoidable. Second, I note that I am consciously aware that I am baised towards certain bows for strictly aesthetic reasons.

    1. The scow bow: Ugly but effective. The idea is simple, shove the water under the hull. Usually used with either a flat or a slightly v bottom that is rockered both fore and aft. Running and reaching this may be the fastest hull form for a monohull. Due to pounding on waves, this bow suffers into the wind unless well heeled. When properly designed, the bow allows a boat to minimize skin friction while sailing upright in light airs and increase waterline length while sailing heeled in stronger airs. This bow is the simplest bow, and for practical reasons, just wont go away. Generally refered to as revolutionary whenever it is rediscovered. This bow gives maximum length and width on deck and maximum volume. Combine with rounded chines, this may be the best hull for small but fast sailing vessels that do not need to beat into the wind often.

    2. The bulbous bow: Slightly less ugly that the scow bow, the bulbous bow shoulders its way through the water. Paired with underwater bulbs, this hull shape can be surprisingly effective, despite frothy bow waves. This bow shape is generally seen on bulk carriers with long parallel sides. It makes the most out of the volume and tends to not nose dive too badly into oncoming or following seas. It is pretty dry when combined with even moderate flare. Only really useful on truly slow sailing vessels or giant tankers and container ships, the bulbous bow has been and probably always will be a hallmark of the truly pedestrian cargo vessel.

    3. The sharpie bow: A significant improvement on the scow bow especially, going to windward. The sharpie bow is a scow bow pinched to a point in the front. The bottom generally has a rocker like a waterski. It tends to plane easily and move with alacrity. Can be prettied up a bit, but usually isn't. Best with long low narrow hulls that have slightly flaring sides and flat or mildly v bottoms. Popular the world over as a fishing or tongueing boats. Surprisingly seaworthy in semi-sheltered Coastal Waters. Popular as racing classes in many locations with shoal water.

    4. The bald headed clippper bow: This bow used to be popular in Slavers, Blockade Runners, Baltimore Clippers, Fruiters, and Clipper fishing schooners. Though called a clipper bow, the ships that wore it, and the bow itself have little to do with the famed clipper ships designed by Pook, McKay, Griffiths and others. This bow is characterized by a workmanlike cod's head appearance, usually with just a gammon knee and no trail boards or other decorations. Paired with a long low hull with drag in the keel, this bow's slack buttocks lines and round but fine sections tend to cause the water to flow both around and down the bow into a long fine run with somewhat straight quarter beam buttocks crossing the load waterline. This bow floats like a cork in the sea, and has plenty of reserve bouyancy. It sometimes shoulders its way through the waves but generally rides nicely over them. It doesn't seem like it should be fast, but it is. Though fast and seaworthy, it quickly fell out of favor as Wave Line Theory entered into vogue.

    5. The Aberdeen or clipper bow: This bow is perhaps the most beautiful bow ever to grace the seas. Used in everything from classic sailing yachts and clipper ships to mighty battleships, this bow has the history to back up its claim to greatest bow ever. The bow is characterized by a sharp rake forward flaring sides, and concave waterlines beneath the load waterline. A favorite of the Wave Line Theory, this spectacular bow lived long after the demise of this dubious idea, because it combines some truly great design features. The sharp rake forward, flaring sides, and sharp underwater profile allow this bow to slice thought the water without nosediving into waves. It has low resistance combined with just enough reserve bouyancy. It isn't too wet, though it does have a tendancy to throw up more spray than other bows. It is important to work the shoulders from the hollow waterlines into the underbody of the bow, to decrease wave making at those shoulders. The load waterline should be sharp but only slightly hollow or only slightly convex. This bow is best on long thin ships, since it tends to slightly decrease length over all and shorten effective waterline length. This bow excels in hulls with full midsections as long as there is enough length to provide fine entrances and long fine runs in the design.

    6. The plum or cutter bow: Another handsome workmanlike bow, the plum bow cuts trough the water like the blade of an axe. Generally used on cod headed mackeral tailed hulls, the bow is often found on vessels that work exposed shores with large tides. An easy partner to flat floors, this bow is at its best when it is sharp, but convex, and combined with a long hollow run. It is a wet bow, that has little reserve bouyancy. It doesn't throw up spray like a clipper bow, but it ships water without hesitation. This bow gives long waterline lengths compared to overall lengths. It also has a lot of room on the fore deck. Combined with reeving bowsprits, a large spread of canvas can easily be set in light weather or shortened when it gets dirty. Some of the most seaworthy vessels in history have worn this bow. Long out of vogue, this bow has been rediscovered for use in a very different type of vessel. We will discuss the axe bow later.

    7. The spoon bow: It is hard to say if this bow is ugly or beautiful. It really depends on the boat. This bow is really just the bald headed clipper bow stretched out and tipped forward. It gives a lot of space on deck, is dry, stabilizes the boat in a seaway, eases entry into seas and encourages water to flow down and around the hull and into a long fine run. The spoon bow is a great option when cutting away the forefront as it tends to flow smoothly into the hull. Best when slightly convex and fine, this bow suffers most, because it shortens the load waterline length while increasing length overall. This is somewhat tolerable, because as the boat heels the waterline length increases. This is a great bow if not carried to extremes. It is especially useful for eliminating bowsprits and bringing sails inboard. It has plenty of usable space forward. Works best with longer thinner deeper hulls, or oddly with long shallow skimming dish style hulls. This bow was popular under certain racing rules and has fallen out of vogue recently. Still if great if used in moderation.

    8. The Reverse Bow or Ram Bow: Truly an abomination, this ancient bow was used on primitive canoes when materials were so poor no other bow could be constructed. In these ancient days, it was known as sturgeon nosed canoe bow. Like it's namesake, this bow turns the vessel that wears it into a submarine. It dives into waves, and ships water. The wettest bow known, it has no reserve bouyancy at all. It strips the boat of useful deck space forward, hampers tacking, and worse of all it is prone to damage. It catches everything there is to catch including anchor chains and mooring lines. The tip tends to break off in collisions with pretty much anything substantial or insubstantial. It does look fast though, which might be an advantage on a really slow boat. Really only useful on multihulls where the crew is a long way from the bow, if you decide to build this bow, build an axe bow first, and then add a ram bow as an extension. This will prevent your boat from sinking when the ram bow is inevitably smashed off. Because it produces the maximum waterline length for length over all and "pierces waves" this hull is often rediscovered and just as quickly forgotten.

    9. The Axe Bow: This bow is really just the old cutter bow recycled, and called revolutionary. It is not as wet or poorly mannered as the reverse bow, and it is a hell of a lot less likely to be ripped off than the reverse bow. Like the cutter bow, it will happily ship water, and needs a long convex for deck to shed that water. It tends to "pierce waves" as well but has slightly more bouyancy that the reverse bow. Usefull on very fast multihulls where the crew is isolated from the front of the boat. This bow can tend to nosedive and and is probably not the best choice for a cruiser. All in all it is a seaworthy bow that has all the advantages of the reverse bow with fewer disadvantages.

    David
     

  2. SuperPiper
    Joined: Jan 2003
    Posts: 364
    Likes: 5, Points: 18, Legacy Rep: 58
    Location: North Of Lake Ontario

    SuperPiper Men With Little Boats . .

    David, that is incredible. Very enjoyable reading. I now feel educated in the details of bow design.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.