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Old 03-11-2014, 11:57   #16
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Re: The bow of cats

I am not suggesting that no boats from the past had plumb stems - although the vast majority did not. Regardless, the same comments would apply. If someone believes that boats must be compared on a basis of LOA, then plumb stems have the advantage of an increased LWL and greater maximum hull speed. If one considers comparing boats based on the LWL, then that advantage disappears. Either way, there are some advantages to front overhang on a cruising boat and it is clearly not merely a matter of aesthetics.

Brad
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Old 03-11-2014, 12:25   #17
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Re: The bow of cats

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Originally Posted by a64pilot View Post
Although I tend to agree with you, that is why they make different boats.
I never realized it, always thought I was more of a "modern" person, but I've come to the conclusion that I'm a traditionalist.
The modern America's cup boats are I'm sure that fastest things they are,
but I want to see the J class race some day, not the America's cup boats.
Johnny come lately, Real Americas cup racing is for full rigged tall ships.

I really dont get why people cherry pick J class or 12 metre boats and say "that is Real Racing". The 12 metres were the most god awful boring things I have ever seen, at least the J Boats were pretty.
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Old 03-11-2014, 13:02   #18
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Re: The bow of cats

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This discussion seems to be proceeding on the assumption that boats were designed with front overhang only for the purposes of aesthetics, or in an attempt to get around racing rules on monohulls by having an unmeasured increase in LWL when a boat heels. This assumption is false.

Naval architects have known for a couple of centuries that hull speed in a non-planing hull (the only hulls that existed 200 years ago) increased in proportion to the length of the waterline. The clipper ships and other sailing vessels of the past were designed with that in mind - i.e.. a particular waterline length was chosen, but then front overhang was added. Was this purely for reasons of aesthetics? Were those commissioning large clipper ships (or those commissioning smaller fishing schooners such as the Bluenose) prepared to pay more more for an aesthetically pleasing overhang that added cost and worsened the performance of the vessel by adding weight and decereasing stability? Of course not. Were they designed with front overhang to take advantage of a rating rule? No, as there were no rating rules.
If you are talking about historical ships (clippers, square rigged) It was more an issue of the available materials. They didn't have aluminum, stainless steel or carbon fiber. You could only go so high with the masts and then you had to go fore and aft with the sail plan if you wanted more sail area on a similar sized vessle.

IMO, one should think of a boat as being designed to a specific waterline with the subsequent consideration being whether the builder (or customer) wishes to pay a little more for front overhang. There are several advantages:

1. Front overhang increases the area of the foredeck, assuming the coachouse and all other aspects of design remain the same. This facilitates sail and anchor handling, etc., on a monohull or trimaran. It also permits a symetrical spinnaker to be flown further forward off the bows of a catamaran. This benefits self steering effect downwind.
Assuming the same LOA, it doesn't add any of these things and adding the additional WLL costs next to nothing.

2. Forward overhangs also reduce spray on the foredecks of both monohulls and multihulls. This is important if one has to go forward when underway.

I believe it is mostly the flare that does this not the overhang. If this is your concern, you can add a bit of flare with a plumb or near plumb bow. In moderate conditions, the flare will never touch the waves but it's there in the event of rougher conditions but you get the speed benefit of the WLL in all conditions.

3. Foreward overhangs provide additional bouyancy forward on the same waterline length - in extremis, the volume increases on three rather than two planes as the bow is depressed. This reduces the risk of burying a bow - a very dangerous phenomenon for both monohulls and multihulls that can lead to a pitchpole or capsize. One of the earlier posts suggested that it would be harder for a submerged bow to resurface if there was a front overhang; no doubt true as the bow would be longer. However, the key is in avoiding burying a bow in the first place, where added front overhang has a distinct advantage.
Only if you look at the WLL doesn't provide more bouyancy. For the same LOA, it provides less bouyancy

4. On monohulls or trimarans (or catamarans such as mine, with bow rollers off each bow), front overhang reduces the tendancy of the anchor banging into and damaging the topsides of the boat as it is being hoisted back aboard.

Most cats don't have bow mounted anchors but it's not a huge issue and you will find most plumb bowed mono's address this with a bow pulpit or stainless steel guard that is largely independent of they hydrodynamic shape.

As naval architect Robert Perry wrote in Sailors' Secrets - Advice from the Masters, Michael Badham and Robby Robinson, International Marine, Camden, 1999 at p. 193:

"Some things, though, begin to look better the heavier the weather gets. Plumb stems are a modern trend. The obviously can maximize waterline length, but in a cruising boat do you want to give up a foredeck and make your boat into a submarine....? Traditional elements like overhang are traditional because they work."

This doesn't make sense. A 30' boat with a plumb bow has just as much fordeck to work from and has more bouyancy so it is less likely to submarine all else being equal.

While the advantages are less compelling in a cat than a monohull or a trimaran, nevertheless there are still some valid reasons for specifying a bow with some overhang on any boat.

And they would be?

Brad
I think the problem is you premise that we should compare boats of similar WLL. Most boats are compared and priced on LOA. If you can afford to buy and maintain a 35' boat with a 25' WLL, you can afford the equivilent 35' boat with a 35' WLL.

Aestetics and racing rules aren't the only reason to for overhanges but they are probably 75-90% of the reason on modern boats.
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Old 03-11-2014, 13:48   #19
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Re: The bow of cats

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Originally Posted by Southern Star View Post
This discussion seems to be proceeding on the assumption that boats were designed with front overhang only for the purposes of aesthetics, or in an attempt to get around racing rules on monohulls by having an unmeasured increase in LWL when a boat heels. This assumption is false.

Naval architects have known for a couple of centuries that hull speed in a non-planing hull (the only hulls that existed 200 years ago) increased in proportion to the length of the waterline. The clipper ships and other sailing vessels of the past were designed with that in mind - i.e.. a particular waterline length was chosen, but then front overhang was added. Was this purely for reasons of aesthetics? Were those commissioning large clipper ships (or those commissioning smaller fishing schooners such as the Bluenose) prepared to pay more more for an aesthetically pleasing overhang that added cost and worsened the performance of the vessel by adding weight and decereasing stability? Of course not. Were they designed with front overhang to take advantage of a rating rule? No, as there were no rating rules.

IMO, one should think of a boat as being designed to a specific waterline with the subsequent consideration being whether the builder (or customer) wishes to pay a little more for front overhang. There are several advantages:

1. Front overhang increases the area of the foredeck, assuming the coachouse and all other aspects of design remain the same. This facilitates sail and anchor handling, etc., on a monohull or trimaran. It also permits a symetrical spinnaker to be flown further forward off the bows of a catamaran. This benefits self steering effect downwind.

2. Forward overhangs also reduce spray on the foredecks of both monohulls and multihulls. This is important if one has to go forward when underway.

3. Foreward overhangs provide additional bouyancy forward on the same waterline length - in extremis, the volume increases on three rather than two planes as the bow is depressed. This reduces the risk of burying a bow - a very dangerous phenomenon for both monohulls and multihulls that can lead to a pitchpole or capsize. One of the earlier posts suggested that it would be harder for a submerged bow to resurface if there was a front overhang; no doubt true as the bow would be longer. However, the key is in avoiding burying a bow in the first place, where added front overhang has a distinct advantage.

4. On monohulls or trimarans (or catamarans such as mine, with bow rollers off each bow), front overhang reduces the tendancy of the anchor banging into and damaging the topsides of the boat as it is being hoisted back aboard.

As naval architect Robert Perry wrote in Sailors' Secrets - Advice from the Masters, Michael Badham and Robby Robinson, International Marine, Camden, 1999 at p. 193:

"Some things, though, begin to look better the heavier the weather gets. Plumb stems are a modern trend. The obviously can maximize waterline length, but in a cruising boat do you want to give up a foredeck and make your boat into a submarine....? Traditional elements like overhang are traditional because they work."

While the advantages are less compelling in a cat than a monohull or a trimaran, nevertheless there are still some valid reasons for specifying a bow with some overhang on any boat.

Brad



Once again, the voice of reason on the multi forum. You gotta stop making so much sense, or they are gonna ban you to the mono forum!
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Old 03-11-2014, 13:48   #20
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Re: The bow of cats

I like plumb bows on boats (mono or cat).

The reverse bows look cool too (because they are "different" or uncommon).

I also like clipper bows (on monos).

The Trireme bow is another favorite of mine (see below) and some say it was really designed for crowded anchorages in the Adriatic and Med.


But, as the subject of discussion is "The bow of cats" I suppose I should include one more illustration.
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Old 03-11-2014, 13:59   #21
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Re: The bow of cats

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Originally Posted by Southern Star View Post
I am not suggesting that no boats from the past had plumb stems - although the vast majority did not. Regardless, the same comments would apply. If someone believes that boats must be compared on a basis of LOA, then plumb stems have the advantage of an increased LWL and greater maximum hull speed. If one considers comparing boats based on the LWL, then that advantage disappears. Either way, there are some advantages to front overhang on a cruising boat and it is clearly not merely a matter of aesthetics.

Brad
But these days people buy (and marinas charge) boats based on LOA. A plumb bow gives you the best waterline length for any given LOA.

And that makes the boat sail faster, pitch less, and better able to carry stuff.
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Old 03-11-2014, 14:23   #22
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Re: The bow of cats

Valhalla, we can agree to disagree. In the early days, they were also able to extend the sail area forward through the use of lengthy bowsprits and they did so in spite of the lack of carbon fibre. You are entitled to disagree, but facts are facts.

You suggest that if the LOA is the same, then the plum bow has greater bouyancy forward. I agree. However, as I mentioned, I believe that LOA is a poor standard of comparison for yachts. If the LWL is the same for two yachts, then the boat with front overhang has more bouyancy forward in extremis. This is not just because plum bows tend to have less flare forward (unless they have very fat bows) - it is because as the bow is depressed, the bouyancy of the overhang comes into play. As I said, in heavy weather the bouyancy therefore increases on three, rather than merely two planes. Simple physics, whether you agree or not.

Why do I use LWL rather than LOA in comparing two yachts? I'm sure that even you would agree that LWL is far more important in assessing relative performance, displacement, accomodation etc.than LOA. Indeed, it has only been in recent times that LOA has become so significant in terms of describing (and more to the point, selling) boat models.

As I recall, the first one-design yacht for the New York Yacht Club was the New York 30, early in the last century. It as 40 feet LOA, but the LWL was 30 feet and, as a result, they (and the naval architect, Nathaniel Herreshoff) called it the New York 30. In the era of mass-marketed boats, LOA became the method of describing most models, even though that number was typically less significant than the LWL. Let's face it, a model that was called a '40' certainly sounded better to the uninitiated, than a '30'. If you wish to be a slave to using LOA as the standard of comparison for yachts, you are certainly free to do so. I am not.
If you take two boats of the same LWL, then one that has forward overhang (which adds little to cost) has definite advantages.

I am unsure how you can suggest that the foredeck on two otherwise identical boats would be the same size even though one boat had an added front overhang. If the coachouse remains the same size, then the foredeck is larger on the boat where the bow is extended by overhang. Full stop.

As to reduced spray and resistance to submarining with front overhang, I am sorry that Robert Perry's comments do not make sense to you. You are entitled to your own opinions, just not your own rules of math or physics!

Brad
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Old 03-11-2014, 14:43   #23
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Re: The bow of cats

44cruisingcat, I agree that marinas typically charge based upon LOA - a definite advantage for plum bows! I was simply attempting to point out that plum bows still have some advantages.

If one takes two boats of the same LOA, then yes - the boat with the plum bow has a longer LWL and a greater hull speed. Indeed, on a catamaran, many of the disadvantages of a plum bow are minimized:

- spray on the foredecks is less significant as the foredecks are typically in front of the headstay, which is mounted on the cross-member. On trimarans and monohulls, however, it is still a significant factor.
- as opposed to a trimaran or monohull, the size of the foredeck on a cat is also not so important a factor with respect to sailhandling - you typically have the use of a very large trampoline.
- since most cats have anchors deployed off the centerline rather than the bows, front overhang does not reduce the risk of damage to the boat's topsides. On monohulls or trimarans, of course, an anchor rolller would have to be extended a long way out (creating increased side loading/risk of failure) in order to come close to the natural extension provided by front overhang. As we all know, hoisting an anchor out of the water when the boat is underway naturally causes it to swing aft.

Anyway, I guess my way of looking at it is this. If you compare cats by their LOA, then there is much to commend plum bows and very few disadvantages (or at least, of the disadvantages of plum bows on a trimaran/monohull). If you compare them by LWL, however, there is still an advantage in terms of forward bouyancy with some front overhang.

Brad
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Old 03-11-2014, 15:49   #24
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Re: The bow of cats

Brad,

Using LWL to compare boats is just silly. Sure it works when the designs start in roughly the same place, but it really doesn't work when you start trying to compare a boat with and without long overhangs.

Just a quick example:

...............Columbia 50 ......Pogo 10.50
LOA -............. 50'.............34.45
LWL - .............33'.............34.45
Disp (lbs) .......33,000........8,000

By your logic that LWL is the right metric to compare these boats they should be pretty much the same. Since the LWL is so close. Of course the Pogo is a slightly larger boat (LWL is a little longer) but no massive difference. Of course this is rediculious, the pogo is a fraction the weight, a fraction the size, and radically faster. Not to mention that working the bow on the Pogo is a dream compared to getting tossed around on the Columbia.

Those long overhangs make the Columbia hobby horse like crazy. And the fine angle of the bow means there is no room to work. By comparison the Pogo has a very broad bow, that opens up into a large deck that's easy to work on. And the long waterline means the pogo isn't going to rock nearly as much.
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Old 03-11-2014, 16:58   #25
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Re: The bow of cats

I am often slow and greatly appreciate the wisdom and knowledge shared here. I have two cats both with overhang and both with stubby sterns. Both UK built in the late seventies. Was this thread intended only for current designs
as for esthetics, the size of the boat is directly proportional to wife approval.
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Old 04-11-2014, 06:51   #26
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Re: The bow of cats

Stumble, I am not saying that LWL is the only metric for comparison of similar yacht types - only that it is typically more informative than LOA. The two boats you listed are virtually as dissimilar as one could get and I cannot imagine that anyone in the market for a cruising boat would be considering a vintage Columbia 50 and a Pogo 10.5, whether looking at LOA or LWL or anything else.

In any event, my point is really only that there are still some good reasons for a bit of front overhang on a cruising boat and that, like most elements of yacht design, the bows are also typically a compromise. Would plum bows be a deal breaker for me on a cruising cat? No, although I would want to ensure that the waterline extended a little further forward of the Cg of the boat and Ce of the sailplan than on a similar boat with some front overhang. In this way you can compensate for plum bows which typically havie less flare and which, of course, lack the reserve bouyancy that the overhang generates in extremis.

Could I live with the foredecks being a little more wet? Yes, although it would make flying a symmetrical spinnaker (a great cruising sale on a cat due to the lack of a pole) a little less comfortable.

Do I worry that there would be a greater tendancy to hobby-horse with front overhang? No and, indeed, with similar LWL on both boats, a well-balanced cat with some front overhange might even hobby-horse less. Keep in mind that the weight of two foot front extensions will be very small as the structure need not have the reinforcment required on the bows of a monohull (there are no chainplates for a forestay, nor typically reinforcement for an anchor roller on the bows of a cat). With little additional weight, the additional flare and reserve bouyancy should actually reduce the tendancy to hobbyhorse.

On a cruising monohull or a trimaran, however, I would have a slightly more difficult time accepting a plum bow. In addition to issues concerning forward bouyancy in rough conditions, the reduction in foredeck space would tend to interfere with changing and flaking sails, inflating your dinghy, even lounging. Only if the boat were a flush deck would this not be a factor.

In addition, as the anchor must deploy off the bow of the boat, the lack of overhang will certainly create some damage to the topsides forward over the course of time.

Finally, the additional spray on the foredeck is more critical on a mono or tri as that is where the forestay/furling gear are located.

All the while. of course, I am prepared to concede that as the LOA will be longer for the same LWL on a boat with front overhang, docking fees will increase. That being said, the front overhang on my cat is only about 2 feet, or a 5% increase in cost. When cruising, we prefer to anchor out so the acual increase in terms of the overall budget will not be that significant.

Brad
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Old 04-11-2014, 07:39   #27
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Re: The bow of cats

I've a 38' IP, whose length overall is 41', add dinghy hanging off the stern it's over 45'
I've never paid for more than a 38' boat, do they often actually measure a boat?
I understand that when tied alongside a dock as you take up more dock space, but if your in a slip you taking the entire slip regardless of your length, so is this just done when your on the dock?
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Old 04-11-2014, 07:49   #28
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Re: The bow of cats

There is no need for overhangs and so there are no overhangs. We have a mono designed in 1967 and she has no overhangs either. I can't say I miss having any.

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Old 04-11-2014, 08:02   #29
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Re: The bow of cats

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(...)

In the early days, they were also able to extend the sail area forward through the use of lengthy bowsprits and they did so in spite of the lack of carbon fibre. You are entitled to disagree, but facts are facts.

(...)
This.

And today we have ways to build taller masts, and we have canvas to build higher aspect sails. These improve upwind characteristics of a boat. And with a rig that can go closer upwind, we need a hull that can be pulled upwind and this implies fine entry and limited (if any) overhangs.

Off the wind, we push out a carbon or alloy bowsprit and fly a kite from there. Fine entry of the upwind optimised bow will now deliver easier drive and better directional stability. We will sail faster and broach less.

Overall we end up with better sailing boats. Better overall, up and downwind.

Aesthetics.

I love plumb vertical bows. Others may love overhangs. There are good boats around for everybody. Just smart thing not to mix up aesthetics with pragmatics.

b.
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Old 04-11-2014, 08:05   #30
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Re: The bow of cats

A minor point- a plum is a fruit. It's a plumb bow. You know, like a plumb bob.
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