dories and seakeeping

[Paul G]

What design factors makes a dory type seaworthy? What does seaworthy mean relative to small (under 20ft) dories or when does it become irrelevant

The traditional flat bottomed form seems to be about ease of build rather than performance and from what I gather lots of ballast, flare and sheer are required to keep the briny out.

I have a dory type hull in my pathfinder and I often wonder what differences a round bilge or vee bottom would make especially to the area in front of the centreboard.

[L.W. Baxter]

I'm not sure that the relatively narrow, flat bottom of a sailing or rowing dory neccessarily compromises seakeeping performance for ease of construction. Just because the elements are simple and come together with little resistance doesn't mean that the whole is inferior to something more complex and tortured.

As I understand it...if one were to convert a dory shaped hull to a vee bottom, the result would be a less stable hull form, unless the increased displacement were offset by ballast... or the turn of the bilge made fuller, as in a round or vee bottom design. Harder bilges mean a wider waterline, and a less easily driven hull. So the narrow waterline and flaring sides of the dory hull are cause and consequence of the flat bottom, and vice versa.

[Rick Clark]

Gentlemen
I took a 17' kayak and cut 5'off both ends the deck was missing on the kayak. I then laminated them back together and glassed them to the bottom of my 12 old town still water canoe, that left 1' bow-stern out of the water. Yes the kayak lay on it's side as I knew it would.
I then att. the outriggers put a 2hp. Mariner motor on it. Pushed it real good but harder the hell to turn with that long keel line.
Set up my lanteen and away I went, not a bad ride , dry, I had to build larger lee-boards for it to get it to jibe half way decent.
No deed to make the bottom less then is needed for initial stability

[ 12-06-2005, 02:55 PM: Message edited by: Rick Clark ]

[Rick Clark]

Yes I forgot to say there has to be an air vent in the bottom of the canoe in to the area of the kayak, I laminated a 1/4 in copper tube 12" Long as a stand pipe.
I sailed that little critter for 3 years and now it is getting a revamp.

[N. Scheuer]

I've come to believe that the dory's principal features are simplicity in construction (therefore cheap), stackable (thwarts removed), and able to keep large quantities of Cod afloat in all sorts of weather.

Other than that, there are lots of more able, better looking small boats on the scene.

In very early years I thought I wanted a Dory built with a cabin, suitable for cruising under sail. Now glad that never happened.

Moby Nick

[brian.cunningham]

I thought a dory's claim to fame, was it's launching and behavior in surf
http://www.geocities.com/garylambda/surfdory3.jpg
Hence it's use as a recue boat.

[Tom Lathrop]

I think you are both right but Nick is much closer to the reason they were built that way in the first place.

I've had some time in two power dorys lately. A 22' C Dory and a 28' Gerr Offshore Skiff. Don't like the behavior of either one.

They have their proper place and properly loaded or ballasted, they can be very seaworthy but, as Nick said, there is almost always a better boat for most uses. Those who love the idea of a dory may be upset. It's only my opinion but it is based on some experience.

[ 12-06-2005, 07:20 PM: Message edited by: Tom Lathrop ]

[L.W. Baxter]

The term "dory" covers a very wide range of boat types, developed for many different uses. Only the banks dories were intended to be stackable, and they were for a very specific use indeed. I gather that the banks type performs poorly under sail...but that doesn't mean that dories are poor sailboats. People who build banks dories for recreation and are disappointed by their performance have just not paid close attention to what they are about.

And just because wide-bottomed power dories behave poorly in rough water doesn't mean that narrow-bottomed, knuckle-sided sailing dories should suffer a tarnished reputation for being distant relatives.

[Thorne]

On the round-sided dories like the Whitehall and Chamberlain, the difference between them and a similar boat with a keelson is fairly minimal at the ends. The center of the bottom is fairly different, but again, the bottoms on these size boats are still really small.

I believe some of the Wherry plans also show the option of a flat bottom to replace the bottom plank on either side.

[pipefitter]

Any boat that rides in the top foot of water is going to be a rough ride.Is a vee better than flat?When it was nasty out I sure didnt notice much difference. The only answer to either of the shallow running types was throttle back and nose up.I had a 17 ft mako that was a vee and it would beat the snot out of anyone forward of the console yet driving it wasn't all bad.If you are in the front of either shallower draft hulls it's going to be a bad ride.One thing that lends seaworthiness to the larger power dory types is it's high sides.Other than that it is just a matter of adjusting the trim/speed to the conditions. The lower sided flat bottom boats like the carolina skiff are very wet boats in even slight chop and you can bet you will be keeping company with about 4" of water in it.I also used to fish out of a converted mullet boat which was kind of a dory and it used to ride pretty good.

[Aramas]

"Seakeeping" is the physics of a vessel's motion through six degrees of freedom. It's a very specific area of study involving a lot of calculus, and doesn't have much relevence to small boats. "Seaworthiness" is a more suitable, albeit nebulous term.

There's nothing inherently seaworthy about dories. The origins of the design had more to do with economy and stackability than with any pretensions of seaworthiness. The reed boats of Lago Titicaca and the umiaks of Greenland are remarkably seaworthy small craft, but there are much more suitable craft to base a new design on, be it power or sail. All small craft are a product of their environment, culture, technology and economics. It's generally a good idea to base any new design on those same factors.

[ 12-06-2005, 11:10 PM: Message edited by: Aramas ]

[Bill Childs]

"There's nothing inherently seaworthy about dories. The origins of the design had more to do with economy and stackability than with any pretensions of seaworthiness."

Do you really believe that? The amount of reserve buoyancy built into a boat whose sides have a lot of flare is incredible. Yes, the early fishing dories were easy to build and stacked nicely, but because of their flare and overhanging ends they were able to carry great capacity and keep a sloppy sea out.

And a C-Dory is about as much a dory as a Boston Whaler is a whaler - jeeez.

[Aramas]

Originally posted by Bill Childs:
Do you really believe that?Sure do smile.gif

The dory is an extreme hull form, with the barge at the other end of the spectrum. Both have advantages and disadvantages, but given free rein, most people would choose neither.

The truth of it is, most characteristics attributed to dories are pure BS. A barge (ie slab sided skiff or sharpie) has higher initial stability, carries loads better and keeps waves out better. The original dories were fine if the boatman stayed on the centreline and didn't move around. The dory's low initial stability allowed it to respond less to wave action - allowing waves to slop into the boat rather than heel it like a barge. That makes them comparatively tippy, wet and poor load-carryers, but harder to capsize in the hands of an experienced boatman.

[ 12-06-2005, 11:44 PM: Message edited by: Aramas ]

[Bill Childs]

I was afraid of that. Think what you will then.

[L.W. Baxter]

The origins of the design had more to do with economy and stackability than with any pretensions of seaworthiness. "The design", Aramas? I think you have revealed the depth of your understanding of dories in general by referring to "the design".

I see, in my local area, "dories" ranging from the Learned and Pacific City dories, to Mackenzie River Driftboats, to the Canadian Batteau I launched this summer, to the Swampscott sitting on its trailer in my garage. Thinking that they can all be grouped together and dismissed is silly.

I'll repeat it so you understand, the banks dories were stackable. I'm not aware of any other type of dory that was or is stacked as a practice.

[Aramas]

Originally posted by Bill Childs:
I was afraid of that. Think what you will then.Unfortunately, my thoughts are dictated by the laws of physics. Were I not aware of the awful constraints that the universe so thoughtlessly imposes on us, my opinions could be unfettered by such irritating considerations. tongue.gif

[Aramas]

LW - My comments were with reference to the hullform of the original banks dories, with other 'dories' coming under the heading of derivative designs. Hull types can usually be (and, in naval architecture, usually are) reduced to typical hull forms, to which certain hydrostatic attributes are inherent. A dory is just a hull with a flat, narrow bottom and sharply flaring sides, and has low initial stabilty and load carrying abilty. A barge (such as all commercial ships, and skiffs and sharpies) has a full width bottom with vertical sides, and has the highest possible initial stabilty and load carrying abilty. Opinions contrary to either definition are incorrect.

In comparing a dory form to a barge form in beam seas, the barge form will heel away from waves, following the profile of the wave, long after a dory is swamped. When the waves are much larger, the dory will remain upright (but swamped) long after a barge form is capsized. In the large interval in between, the barge will remain dry while the dory is swamped. This is not an opinion. It's physics.

The 'seaworthiness' of dories has little to do with the hull form directly, but rather it is directly due to the seamanship of the occupant, and only applies to small sizes in which crew weight can significantly effect stability. A good doryman controls the heel of his boat like a kayaker does, leaning his body away from waves just enough to keep them out of the boat, and knowing from experience just how much input is required, and when to allow the boat to be swamped rather than capsize. In contrast, the occupant of a barge of the same length and beam has very little control over heel, and is at the mercy of wave action.

In short, the defining charcteristic of a dory's behaviour in waves is that it will be less effected by wave action and, up to a certain seastate, it will take waves over the gunwale rather than capsize. Any other quasi-mystical attributes are merely dogma or wishful thinking.

[ 12-07-2005, 12:29 AM: Message edited by: Aramas ]

[L.W. Baxter]

I think you have established a false dichotomy, Aramas. There are not two extremes of hull shape embodied by barges and dories. Some dories resemble barges quite a bit. And they are the worst sort of dory. But still better than a barge. ;)

[ 12-07-2005, 12:40 AM: Message edited by: L.W. Baxter ]

[Bill Childs]

Whoa there Aramas. You're fettered by your own confidence and wisdom. You said that a sharpie has greater load carrying ability than a dory and follow that opinion with - "Opinions contrary to either definition are incorrect." Nice of you to dismiss any other opinions.

Load the same weight of cod in the same size sharpie and dory. Add some miserable seas. Don't bother with a helmsman or his skills, just let them be out there. Some of us have learned a little bit about physics also. But I doubt we had the same classroom.

[ishmael]

Hm. My understanding of the dory shape is definately seat of the pant, not from engineering theory. Their evolution had to do with both their incredible keeping ability and their ease of build. The two struck a balance that has never been equalled. Give anyone who's been out in it a choice between a dory and a round bottomed boat in a seaway and which will they pick?

Just random thoughts. The flat bottom offers no resistance. It moves with the wave at the wave's will. Why you don't want a skeg. The flair keeps the water out. Those two things make for a remarkably good boat, which also happens to be easy to build. Maybe there is a god! smile.gif

[TomF]

While I completely agree that banks dories were designed with the economic concerns in the forefront, as you've mentioned Aramas, I'm frankly more inclined to agree with John Gardner.

In any small open boat, seaworthiness is in no small measure determined by the actions of the crew. While there may indeed be more "seaworthy" small boat designs than the dory, it's been well proven.

Tom.

[ 12-07-2005, 10:08 AM: Message edited by: TomF ]

[Thorne]

Gardner certainly makes this distinction of "seaworthyness", and seems to regard the round-hulled dories with lots of rocker as more seaworthy designs than the flatter Banks designs.

Regarding the Chamberlain dory skiff, he says in _
Building Classic Small Craft_:

"(it)...will row easily and be a good sea boat, as well, within the limits of its size..."

"In spite of its flat bottom, which of course is relative quite narrow, this dory skiff has virtually a round hull, and for all practical purposes behaves as a round-bottomed boat. Indeed, this skiff closely resembles the old-time New England wherry, which was a fine sea boat."

(So there!)

;- )

[ 12-07-2005, 09:12 AM: Message edited by: Thorne ]

[Bruce Hooke]

Thorne,

I don't see anything in the statements you quoted that indiciates Gardiner thought the Chamberlain dory skiff was in any way MORE seaworthy than a Banks style dory. The statement about "in spite of its flat bottom" is simply about whether this dory model is, practically speaking, a round-bottomed or a flat-bottomed boat, and as I read it, implies no judgement about whether round-bottomed or flat-bottomed boats are more seaworthy.

Beyond that, let me just say this: I have a barge shaped boat I built myself (specifically for quiet, shallow water). I also lived on an island on the coast of Maine for a few summers and one year I stayed on the island until Christmas. My transportation to and from the island was a Banks style dory. There is NO question in my mind which boat (the barge or the banks dory) would have been better for the task of carrying me and various supplies through the sometimes rough seas I encountered between the island and the mainland.

[Tom Lathrop]

Originally posted by Bill Childs:
And a C-Dory is about as much a dory as a Boston Whaler is a whaler - jeeez.[/QB]Let's see now. Narrow almost flat bottom (originally, it was flat until buyers complained too much about the slamming), high sharp bow, greatly flared sides.

Except for the chopped off transom, it sounds just like a dory to me. What other category could it fit into?

[Thorne]

Bruce -

I'm certainly not casting aspersions on Banks dories, as they seem to be widely regarded as a good workboat.

Regarding Gardner's perspective, I haven't studied it at any length, but what I've come across in some of his books has always led me to believe that he feels a rounded hull is better "at sea" than a flat-sided hull.

(I feel like I'm quoting scripture here in some religious discussion!! grin )

In Building Classic Small Craft he says in the introduction,

"The rounded hull of good design is treated much more kindly by the sea. for this reason naval architects often characterize such hulls as "sea kindly". There is nothing flat or square for the surging seas to grab or slam against. Like the seasoned boxer, they "roll with the punches." The initial stability of such a hull may not be great because of the relatively sharp, easy lines of its underbody, so that it will start to roll quite easily. Yet, if competently designed with ample side flare, freeboard, and beam, as well as adequate overall length, it will rapidly pick up stability as it rolls down. Thus it will go only so far and no farther, to pause briefly before starting to roll back. The ultimate stability of such a boat will, under almost all conditions, prove more than ample."

Thus spake Saint Gardner in the epistles of the Introduction...

;- )

[Bruce Hooke]

Here is what seems to me to be a more relavant quote from The Dory Book about the Chamberlain Dory Skiff:


On the smaller ponds and shelted harbors, a wide, flat bottom is all right. Drawing little water and skimming along easily, if the water is smooth, the flat bottom is stiff and steady. Add high sides and you have a boat that small children can't tip over or fall out of easily. But don't take such a boat out where the big ones are rolling. Out there you will be much better off in something like the Chamerlain skiff.The Chamberlain Dory Skiff is a 13-foot dory with quite rounded sides and a larger transom than a Banks Style dory, but still with a distinct knuckle where the sides meet the bottom. The transom is also quite narrow at the bottom and stops near or above the waterline, as on most good rowing and sailing boats. Gardiner does note that a large boat will, all other things being equal, handle larger seas than a smaller boat will.

This all fits very well with my understanding of the matter. In the size range we are talking about a barge-shaped boat is very poor in heavy seas. This is why your basic flat-bottomed skiff is basically a boat for sheltered harbors, and why, across a wide variety of cultures and waters, small boats designed for rough waters almost always have relatively narrow bottoms and plenty of reserve stability above the waterline. As to whether a boat with a narrow bottom and flat sides (e.g., a Banks Dory) is more or less seaworthy than a boat with a narrow bottom and rounded sides (e.g., a Swampscott Dory, and many, many other designs, some dories but many not)...this is more debatable question. However, given the prevelance of rounded sides it seems like the general preference where other issues like ease of construction and stackability do not win out, leans very much towards rounded sides.

As to the physics of the matter, Seaworthiness: The Forgotten Factor gives a detailed explanation of why a boat that stays relatively vertical in heavy seas (as a dory does) is more seaworthy than a barge like boat that tips to follow the surface of the water.

[Bruce Hooke]

Thorne,

As you will see from my previous response, we are basically in a agreement, I was just responding to the quote you selected since it did not seem to really address the matter at hand...

- Bruce

[Thorne]

Bruce --

I went out to the garage and hugged my Chamberlain dory skiff, and she tells me that her feelings aren't hurt - so all is well.

;- )

http://www.luckhardt.com/cb-down.jpg

Obviously this overall discussion is so general that it can't rely on specific facts, as there are a zillion designs called 'dories'. Not quite as bad as the catch-all term 'skiff', but close...

[nedL]

Even after all this discussion there's not much that would change my mind from believing that I'd want a Bank's dory under me if I had to be out in nasty weather in a small boat. :D http://www.imagestation.com/picture/sraid14/pa4107b1f75df0c85a6a05523069ea45e/fde2bd28.jpg
Older than the hills when I got her 40 years ago. May she R.I.P.

[L.W. Baxter]

LW - My comments were with reference to the hullform of the original banks dories, with other 'dories' coming under the heading of derivative designs. Aramas, my point was that "dory" refers to a method of construction, not a design. If you want to establish that the banks dory is the archetypical dory form that's fine (though they are not the "original" dories) but be clear about it. Dories developed for poling, paddling, rowing, sailing, or motoring performance are very different.

As far as your description of how your archetypical hulls perform, I think you have it bassackwards.

You say:

the barge form will heel away from waves, following the profile of the wave, long after a dory is swamped. And add:


In short, the defining charcteristic of a dory's behaviour in waves is that it will be less effected by wave action and, up to a certain seastate, it will take waves over the gunwale rather than capsize. Any other quasi-mystical attributes are merely dogma or wishful thinking.
In my experience on the water, this is exactly the opposite of how boats behave. The dory with narrow bottom and flared sides responds very quickly to wave action, and this nimbleness is what farmers call "tippiness", and which gives them the impression that the dory is dangerously unstable. But in the hands of the capable boatman, the tenderness of the dory becomes a virtue, rightly so. The flared sides and long overhang of the dory lift the boat over waves in a fluid and natural response, remaining upright--and not swamped, LOL-- in rougher water. There's your "inherent seaworthiness".

On the other hand, a boat more closely resembling a barge--with a relatively wider bottom-- will be "stiffer", responding less to wave action, giving the impression of great stability and security.

That's just an impression, though, and a dangerous one, particularly on the scale of small boats. The greater initial stability of the type resists being lifted...until it is too late, and the bottom falls out. That stiffer boat is much more likely to be swamped by confused water, or broached and flipped, or pitchpoled by a big, steep wave. On protected waters, of course, the more "stable" boat is much more comfortable. But we're talking about "seaworthiness", not the ability to fish the local trout pond while standing on your bow platform.

[Bruce Hooke]

Actually, I'd put things somewhere between the two extremes...

A barge sits on the surface of the water like a board -- if the surface of the water tips, the board, or barge, tips with the water. A dory, on the other hand, because of it's narrow bottom, is initially less influenced by the slope of the surface of the water, so it can stay more upright. But, note that it is staying upright precisely because of its lack of initial stability. This is why Banks type dories feel tippy when you get into one.

However, now let's say that both boats are being tipped substantially. The barge, once it reaches a certain point, will roll rail down quite abruptly and swamp or capsize. The dory, because of all the reserve stability it carries above the waterline as a result of the strongly flared sides, will gain quite a bit in stability as you tip it, so it will, in fact, resist swamping quite well.

Now, the thing about a Banks style dory is that it picks up reserve stability quite abruptly because of it's straight sides. A round-sided dory (or other boat) can have plenty of reserve stability, but be designed to pick up that stability a bit less abruptly, which makes for a gentler ride and, arguable, a somewhat more seaworthy boat. However, both are clearly better than a barge type boat, which has very little reserve stability.

[johnw]

I can think of few boats less seaworthy than a johnboat and few more seaworthy than a dory. Yet coast guard regs require an inclining test to judge how many people a boat can carry. Johnboats always do better in the inclining test, so even though they are the type that was typically capsizing and were the reason for the regs in the first place, they get rated for a higher capacity. As for sharpies, try rowing one of those for about ten miles and you will very much wish you were in a dory. Dories needed a narrow waterline in order to be easy to row, and plenty of reserve stability in spite of that to make them seaworthy. Reserve bouancy and reserve stability are great helps to seaworthyness, and a boat that carries its bouancy high is more likely to be seaworthy than a boat that carries its bouancy low.

[Bruce Hooke]

What a lot of this discussion appears to be converging around is that it is not so much the flat bottom that is the issue, as it is the flat sides. A narrow, flat bottom is not really that different from a round bottom. Straight sides, as on a Banks Dory are more different and have more of an impact on handling and seaworthiness.

[johnw]

I think the big distiction is between wall-sided boats like johnboats and boats with flaring sides, whether they are round-bottomed or flat bottomed.

[mmd]

I've always found it odd that boats of such diverse size, shape, and use can be called by the same name. In order, a St.Pierre dory, a Lunenburg-style Banks dory, and a Swampscott sailing dory.

http://www.luciengirardin.com/images/cabaneweb.jpg

http://www.capeannweb.com/dory/dorypics/2.jpg

[img]http://www.town.swampscott.ma.us/Public_Documents/SwampscottMA_WebDocs/00141370-000F8513.0/2503_85144_1.png

[Bruce Hooke]

Originally posted by johnw:
I think the big distiction is between wall-sided boats like johnboats and boats with flaring sides, whether they are round-bottomed or flat bottomed.I should have been clearer. I agree that flaring vs. wall sides seems to have become the big issue on this thread (actually, I think there is general agreement on this topic, with the exception of Aramas). The point I was trying to make goes back to Paul's original question. I was simply trying to say that focusing on a dory's flat bottom is largely beside the point.

[dmede]

Originally posted by mmd:
I've always found it odd that boats of such diverse size, shape, and use can be called by the same name. [/IMG]I think if you know a little about the history and evolution of the type, and the construction method that it describes, you easily see the geneology they have in common (for most of the Dories anyway). Gardners "the Dory Book" gives a good deal of attention to this issue.

edited to add: that sounded a bit demeaning after re-reading. not intended. pointing out that there is a relationship between the styles of Dory that is more obvious after reading Gardner.

dave

[ 12-07-2005, 05:45 PM: Message edited by: dmede ]

[Dave Fleming]

Tugboat Dave likes my dory. ;)

http://pic4.picturetrail.com/VOL780/3097474/6292566/121161397.jpg

http://pic4.picturetrail.com/VOL780/3097474/6292566/121161395.jpg

[Bruce Hooke]

Dmede:

However, I'd say that in most cases the construction method does not define the type of boat. For example, a variety of boat types are all built with plank sides and cross-planked bottoms, and there may well be a common history behind this type of construction, but the boats built in this way are not considered one "class" of boat in the same way that dories are.

[ 12-07-2005, 06:36 PM: Message edited by: Bruce Hooke ]

[1stnewyorker]

Having built only one boat (a dory), I have little to offer in regard to disussions of stability, boat design, etc. However I can say that my dory performs far beyond what I had expected prior to building it. She is very weatherly, and handles well under oars or sail. I've had it in very heavy seas on Lake Champlain, on several occasions, and each time she was very stable and shipped very little water. My view is that the thousands of New England cod fisherman sailing them for the last hundred years or more must have know something. http://www.1stnewyork.org/boat/General-arnold.jpg

[LazyJack]

I think it somewhat silly to consider attributes of 'seaworthiness' in isolation of the human factors. While physical analysis of a 'barge' or sharpy hull form in a beam seaway might indicate that it won't swamp as easily...won't it be far more difficult to manage the boat that is snapping about under you? Won't that be rather fatiguing pretty quickly? How 'seaworthy' is the boat then? In a heavy sea, give me a dory any day! OR better yet, give me the exeprience and judgment that will allow good decisions before I leave the dock in the first place.

[ 12-07-2005, 08:57 PM: Message edited by: LazyJack ]

[pipefitter]

It is easier to move a narrow bottom boat for sure.Just look at a canoe.Yet a canoe is very tippy and you paddle a canoe.If the sides of a dory were not flared,wouldn't it be a paddling boat and not a row boat? Surely there has to be some space between oarlocks to be able to row a boat efficiently with enough leverage of the oars. Just seems like the best of all the worlds and an obvious design.
I was always under the impression that barges were straight sided so you could fit more of them next to eachother without having overhanging extremities to get damaged as they bumped together or to be able to drive a crane or heavy equipment onto them.To get as much displacement for the room they take up as well as easier to build or to keep to a standard dimension.

[Bruce Hooke]

The boats in a branch of the dory family called Bateaus, which lean strongly in the narrow direction, can indeed be paddled just fine. Bateaus are river boats, like canoes, but the construction is dory style. You do need sufficient space between the oarlocks to row well.

[Paul G]

Thanks for the discussion, I have been re reading various comments to see if I can relate them to my question and I realise that this is a very big subject, and as usual there is no black and white answer to anything to do with boats! A sailing dory heeling offers a very different profile to the sea that an upright rowing dory, even before we consider beam, flare and rocker.

[Ian McColgin]

Some prefer the Banks dory shape to the more rounded Swampscott shape. Either can be made a bit plump or a bit narrow with enormous changes in behavior. It is believed by many experts that the Banks shape does not work well in lengths under 20' and even the Swampscott shape gets difficult to love under 16'.

I've had the delight of rowing for years in three hugely contrasting dories.

There's Leeward, an 18' Chamberlain Gunning Dory - doublended, narrow plank bottom, flattish garboards with deadrise maybe 20 degrees amidships, and mid and shear strake knuckling to give her that "rounded" look higher up.

A friend's 18' banks dory shape with the narrow bottom planks, flat sides, midships deadrise more like 60 degrees, tombstone stern.

I think both these boats were about as well proportioned for their length as possible.

I also rowed a friend's Gloucester Gull, which is really more like applying dory construction to a practice scull. The Gull is a hot little rowboat but uncomfortable and requiring very skilled handling if you're trying to row beam on wind and sea in say a Strong Breeze (Force 6) with the attendant viscous seas. And she's a real crank in a following sea. Nor is the Gull a load carrier. She's a sport boat very suitable for fast solo transport in moderately sheltered waters.

Leeward was without any doubt the best seaboat all around. Being a bit lower than the Banks dory, she was far easier to row against a wind. The partially rounded sides made her both less likely to broach in a following sea and perfectly able to surf sideways if she did. I know. I used to come in through 10' plunging surf to the Oregon beach and I'd not do that in a Banks dory.

The banks dory shape most comes into her own as a load carrier. Light she's a bit tender, to say the least, and can get dangerous in waves. But give her some good ballast, like a half-ton of fish in well-anchored boxes, and she'll act like a keelboat. Very comfortable.

Both Leeward and the Banks dory could easily handle 1,000# of cargo but with Leeward, that was a load that made her slow and hard to row as the relative beam to length became rapidly more adverse. When very heavily loaded, Leeward did not carry her weigh between strokes all that well. With the Banks dory, the slab sides also meant that the buoyancy was carried deeper and the ultimate beam to length was still relatively svelte. With the loaded Banks dory, rowing a nice easy 3 knots is almost restful, what with the improved stability and vast momentum. If all I wanted in a boat was load carrying under oar, I'd go with the Banks shape.

If built of wood with maybe a little high floatation at the ends and inside under the gunnell amidships and ballasted with something of semi-neutral buoyancy, like fish, both the Swampscott and the Banks dories are quite stabile and rowable awash. If you can stand the wet and cold, they'll get you back.

Awash, you'll probably want to back down for beaching through surf. Light, you'll have to back the Banks dory through surf but you can, if bold, strong and a bit of a show-off, surf the Swampscott type.

I liked the Swampscott shape - Leeward - far better than the Banks shape for hand longlining because of the shape's better ultimate stability. Both have little initial stability but the Banks shape really does not get better and the rail goes under easily. With the round shape, I could have the line over a large oarlock amidships, lean that way grabbing hold right near the lock, lean back to let my weight raise the gunnell way up and then haul in my slack as I leaned forward again. Can't get that powerful vertical pull off a Banks dory.

A Banks shape will sail, but poorly. The Swampscott shape is really a nice sailor but with the narrow stern is can never really power up. The semi-dory ranging from Gardiner's to the much-loved TownClass is a true sailboat shape as it has the bearings aft to really carry some canvass.

[Tom Lathrop]

Great Ian,

Should be required reading for anyone thinking or dreaming of building a "dory".

[Dave Fleming]

I started with John Gardiners 12 foot dory plans that were in an old National Fisherman and 'tweaked' it a bit here and there as well as making the frame connections out of Red Cedar sawn root stock.
It rowed well both on the Duwamish River and in Puget Sound near Anacortes. My son's, ages 12 and 17 at the time had no trouble handling her. As can be seen in the photos there was some fiddling with the oarlock positions as the boys grew. When I gave her to Dave, couldn't manage to cart her down here to 'insane Diego', he again modified the rowing position as well as beefing some things up for his use.

[ 12-11-2005, 01:54 PM: Message edited by: Dave Fleming ]

[Thorne]

I heartily agree with Tom -- great job, Ian! Succinctly put and accurate too.

I will think about this writeup whenever I swamp my Chamberlain dory skiff under sail...

: - )

[schoonertack]

Hello all; I don't know if it would interest you to know that the Northwest Natives canoes ie., Haida Klingit etc., all having their own character. All have a very flat bottom. I think there is a graph of roll dampening in Marjah's "Seaworthiness a Forgotten Factor" That explains the advantage of the flat bottom boat in roll dampening versus the round, as well as an advantage in beeching. Now if you wan't to row a barge,well go for it. smile.gif smile.gif

[Bradley]

Back in '91 i designed and built a 19ft, wooden flatbottom skiff and i have logged over 50,000nm of open ocean travel in that skiff since then.

One of the most important properties of my design is that water accumulates in the belly of the skiff while at rest. Virtually all production outboard skiffs have a common design flaw in that any water entering the hull immediately goes to the transom where the likelyhood of capsizing will be increased in porportion to the actual weight of the water. The effect is exponential. It is THE single most common reason for small vessel capsizing. If the center of buoyancy is in the center of the skiff, you will be able to take on much more water before capsizing, saving precious moments in WCS.. You may never need it, but if you do it will be the deciding factor. One other advantage is no matter how big or sharp the swell is, she will up and over from the transom without taking on any water. One of the reasons double-enders sit it out so well in WCS.

The way i acheived that centered buoyancy in a flattbottom skiff starts with the rocker. View from the side. 2/3 bottom length forward of the transom is the 'impact point', the widest part of the bottom (8" wider than the transom). The horizontal datum plane touches the bottom at the impact point them makes a flat line (planing surface) rising 3" at the transom. From the impact point fwd, the hull rises parabolically to 6" at the bow stem.

There are other factors and design implimentations that make the good skiff work so well in rough seas. I use a tiller rather than remote steering because it allows articulate throttle control as well as instant lock-to-lock steering capability in WCS.

When you run the seas in earnest, worst case scenario (WCS) is your guiding reference whether you have ever needed it or not.

Because, there is nothing like the feeling of utter security on a tumultuous sea~