sailboat bows

What is the reasoning for having a bow that comes straight down to the water besides getting more waterline.I do not know the technical term but this doesn`t seem like a good thing to me.Comments

 

It's easier for water to split off to either side of the boat than to go under it. Any water flowing underneath the hull must displace the water already there, wasting energy on sideways motion (athwartship). What you really want to do is slice the water efficiently, which is what the plumb bow does. An angled bow will tend to push the water downward, and has more to do with getting up waves or planing.

 

Plumb Bows are a way of Maximizing waterline length (for a given overall length). Thats why you see plumb bows on boats designed to a rule that restrict LOA. Plumb bows also tend to allow a narrow entry, and added volume, compared to a more "traditional" shape.

 

dman,
What the others have failed to mention, and which will make much of it clearer, is that a longer waterline length, in general, makes for a faster boat. This may sound strange, but it is true. (long story - see other threads)
Thus, if your length is limited, then you want a plumb (upright) bow to make the most of it.
Steve

 

Thanks for the replys,I understand the extra waterline for more speed but what about the effects on a cruising design.Why do you not see ships with that design?

 

Read the original post SD, he understands the waterline/speed issue. My understanding is that a square forefoot tends to trip the boat up when running before a gale. That's a big problem, since if you get caught in a blow, running may be your only option.

 

You rarely see ships with plumb bows, but it has been done. A conventional bow, with flare, keeps green seas off the deck until you get in the extreme rough stuff. Hence it protects the deck gear and any cargo that may be stowed above deck, like containers, from getting smashed by the seas.

 

Ships vith vertical bow?
Take a look at this
http://www.marinelog.com/DOCS/NEWSMMV/2005apr043.html

 

Plumb bows are nothing new, many traditional working boats had them. British pilot cutters for example. As for ships, there was a period when they were not only popular, but even dominant, (Titanic for example).

Aside from advantages in racing classes measured by the over all length, they are also simply most efficient, in terms of material usage. (The reason they were used by working boats and why they could be interesting for modern cruising boats).

Milan

 

A new meaning to the term "Bluff Bowed" .

Steve

 

Ocean Cruisers and/or racers dont tend to use them because the waterline issue and the fact that in a seaway having overhangs of any sort becomes very uncomfortable and can knock the boat off course.

 

Blunt Bow At The Deck

A plumb bow can have a finer entry.

I have always wondered why bows are not razer sharp from waterline to deck. Even modern racing boats will have a fine entry but will have a large radius at the deck level. Is this something to do with increasing the volume (and bouyancy) as a bow dips under a wave? Is it part of the rating game? Does it have to do with angle of attack as a hull heels or as the bow is submerged?

I am convinced that it is not a structural consideration.

 

A bow profile is one of the most distinctive features the eye is drawn to when looking at a yacht. The style a vessel carries in these lines is more then their function (which has only been lightly touched on here). Racers and commercial vessels are duty bound with the tasks asked and their bow profiles typically reflect this. A cruiser isn't selected because it takes most advantage of available LWL, but many other, usually considerably more important constraints (to them), such as reserve buoyancy in a plunging sea, ample rode and chain locker stowage, a pretty place to hang trail boards, etc.

Bows come in all shapes and types. Reversed, submerged, bulbed, clipper, spoon, plumb, Indian head, etc. Some are pure styling exercises, others an attempt to beat racing rules or increase efficiency or other element, in this area of the design. The same is true of sectional and plan shapes used in the bow. A great deal of thought goes into a boat's entry, which covers several issues of concern in this location. Some will sacrifice a fraction of a knot in hull speed or cargo capacity, to make this area look nice, others can't afford this.

 

I'm not an architect (as I'm sure will be all to obvious), but it seems to me that a plumb bow or even some of the more excessive examples here are requisites of "submarines"! IE: vessels designed to submerge. It makes sense to me that it is more efficient to a point to slice through the water than push it down, but at sea isn't it more important to keep the deck above water! Most racing (which I'm also no final word on) seems to be done in controlled environments or at least many times dependent on weather and conditions. When cruising, out at sea, and things get rough, you really can't just postpone the event. Isn't one of the main ideas to keep the water off of, and especially out of the boat?

 

When cruising, out at sea, and things get rough, you really can't just postpone the event. Isn't one of the main ideas to keep the water off of, and especially out of the boat? end quote This is what I am trying to find out.Which type is more seaworthy?I know it all has to work together(hull shape) but has anyone come out with any data to which is better suited to extreme conditions.