Canoe (or double end) boats efficient?

[Nomad Willy]

Depends entirely on the speed of the vessel ....
And all other elements of design like WLL, displacement and all else.

Most canoe sterned boats are very efficient about one knot below hull speed. Generally speaking more than any other nonohull.

 

[Jeff F]

The need to do that speaks to the inefficient nature of canoe sterns and lack of adequate reserve buoyancy . Just imagine a wave coming up from under and stressing that ugly thing.

I disagree. These boats are extremely efficient with small motors, which is their heritage. And recognized for tremendous seaworthiness, which doesn't point to issues with reserve buoyancy.

The need for the modification came when motors got bigger and they wanted to go faster. It's a giant permanent trim tab that allows higher speeds.

I wandered the docks in a few harbors in Iceland and many of the boats I saw had that feature. Lots of variations.

If it works for those guys I'm going to study and learn.

 

[RBack]

The need to do that speaks to the inefficient nature of canoe sterns and lack of adequate reserve buoyancy . Just imagine a wave coming up from under and stressing that ugly thing.

Such a fixed trim tab is certainly not about buoyancy. If buoyancy was the problem the solution would naturally be a completely different one.

But I do understand the misconception due to having mentioned that bigger engines led to the use of these trim tabs.

However in these boats the engines are very often quite far away from the stern. In my boat the engine is placed very much right in the middle - or just slightly aft.

Furthermore stronger engines didn't equal heavier engines. I those days it was often a matter of more efficient engines. So no need of additional byuoyancy due to a heavier boat.

And when hull speed is reached, it sure aint buoyancy that does the trick of stopping the stern to dig down too much.

However... This thread also discussed the efficiency of canoe stern boats travelling with the wind - with waves pushing. And in those circumstances a large fixed trim tab can actually cause some concern if the water (the wave) has enough surface to push on while moving downwards. I'm not aware of any accidents caused by that around here though. At least my boat behaves rather well in following waves. But it sure ain't perfect of course. What is? And boating in such conditions is also a matter of knowing how the boat behaves and act accordingly.

A well designed trim tab will contradict the forces that pulls the stern downwards when reaching hull speed. But then it also adds some hydrodynamic resistance since these sterns were not originally designed for trim tabs. This means that the water flow at speed would want to go one way according to the hull shape but is forced another way (down) by the trim tab. This will inevitably cause some drag.

None the less. That additional drag seems to overrule other hydrodynamic forces connected to maximum hull speed thus allowing some extra speed. So think of it as a foil.

The crudely made trim tab on my boat is certainly not as effective as it can be. So if a new one is fitted, it wil surely be more of a thin foil shaped version. It will be slightly smaller as well.

 

[BrianG]

However in these boats the engines are very often quite far away from the stern. In my boat the engine is placed very much right in the middle - or just slightly aft.

I have a vintage Monterey double ender trawler, yes, my engine is far from the stern. I can attest.

 

[RBack]

Depends entirely on the speed of the vessel ....
And all other elements of design like WLL, displacement and all else.

Most canoe sterned boats are very efficient about one knot below hull speed. Generally speaking more than any other nonohull.

Well, I'm a total nerd in terms of efficiency at cruise speed.
There are several small adjustments I'd like to do on the submerged parts of the hull - especially around the prop and the rudder.

It's not about speed - it's about gliding as effortless as possible through water.

 

[RBack]

I have a vintage Monterey double ender trawler, yes, my engine is far from the stern. I can attest.

1903 if I remember correctly?
That surely turns my 1962 construction into a true modernity.

I think your trawler has entered my "boats I'd very much like to own list".
It looks gorgeous.

 

[BrianG]

1903 if I remember correctly?
That surely turns my 1962 construction into a true modernity.

I think your trawler has entered my "boats I'd very much like to own list".
It looks gorgeous.

The boat in my avatar is the original 1903 from which my boat got her lines and inspiration.

 

[Sailor of Fortune]

Well, I'm a total nerd in terms of efficiency at cruise speed.
There are several small adjustments I'd like to do on the submerged parts of the hull - especially around the prop and the rudder.

It's not about speed - it's about gliding as effortless as possible through water.

I couldn't imagine a more easily driven hull than yours . Very nice lines. It will be interesting to hear the results of your mods around the prop and rudder. Please keep us posted

 

[Hippocampus]

In a earlier post I pointed out due to absence of volume, reserve buoyancy and need to maintain a reasonable gyradius that will allow reasonable behavior in a seaway canoe sterns are inefficient. Light ends ( both bow and sterns) improve gyradius. I’ve point out in extreme conditions they do worst than other designs. I’ve pointed out they increase parasitic drag. I’ve pointed out for boats of equal LOA they have less LWL hence lower hull speeds at more expense. I’ve pointed out there are no canoe stern trawlers in current series production. I’ve pointed out you should judge all aspects of a design not just one feature but this feature causes other design concessions that impede function.
There’s no doubt aesthetically they are much prettier than other designs if done right. I understand the dinghy factor where a boat must make your heart sing as you leave her and look back at her. Otherwise why put in the work and money involved. All the examples here are decades old. Some older than this dust farter. They are magnificently beautiful but still of only historical interest. I come to this discussion having owned and made multiple open ocean passages on canoe stern boats and other designs. From experience I continue to state this feature doesn’t improve tracking, nor sea kindliness, nor safety nor hp requirements nor behavior while surfing nor usable volume and leads to loss of useable volume and othe unfavorable design concessions. I continue to hope a NA or other person more knowledgeable than me could join this discussion to elucidate the hydrodynamics of this.

 

[RBack]

In a earlier post...

I wrote a long reply to this. But it somehow got lost when it was submitted due to som log in thing.

In short...
For some reason it seems like the owners of canoe sterned boats would need to defend the ownership of such boats.
I'm not going to do that.

But I can say as much that if I for some reason would need to encounter really rough seas, there are a number of factors that are much more likely to cause problems way before the hull fails one way or another. Furthermore I don't care about the impracticalities, the "waste of space" that a double ended boat like mine "provides" or that it's an old boat of only "historical interest".

Neiither am I trying to say that this is the type of hull every boater should own.

boat owners purpose of owning boats are different and the preferences in terms of practicalities are not the same.

I'm experiencing really smooth and nice rides in both headwind and tailwind. Fuel consumtion is on par with the most fuel efficient contemporary equivalents despite the engine from 1962.

There is no reason this construction, made in and for the Baltic sea, wouldn't be able to travel around here for many, many years (or decades) to come.

 

[Hippocampus]

Owned. 12 1/2 for awhile for the same reason. A design over 100 years old. Beautiful and totally served my purpose. Strong community of fellow lovers of herreshoff designs. Wonderful experience. No need to explain RBack. Totally get it. Please realize my comments are only directed at the original question “are they efficient “. Not are they good boats to own or do they give joy. End of day it’s recreational boating. Its an emotional not logical decision to even own a boat. If I could pick up a redningskoite converted motor lifeboat in good shape at reasonable cost I’d look real seriously at it. They just seem to have something “right” about them. They look so salty to my eye.

 

[Nomad Willy]

The canoe stern is more efficient at slower speeds.

By slower speeds I’m talking about 1 1/2 to 2 or 3 knots below hull speed depending on hull length.
The significant thing about this is that is that it’s so slow nobody goes that speed.
At hull speed we all (irregardless of hull type) have a significant bow wave that represents wave making resistance. But there’s wave making resistance at the stern too. With a square stern and some significant immersed transom this turbulence looks like boiling water to varying degrees depending on boat size, speed, displacement and hull shape. If you look over your transom (square stern) You will see water close to the transom actually moving fwd toward the boat. It takes More power to move a boat that drags water fwd underway. Same thing happens w a big van box truck on the road. Stand near a truck going by and you’ll experience a rush of air just as the truck passes moving in the same direction of the truck. Same w a boat in a different fluid.

But w the double end boat almost none of this “backdraft” water or air occurs so the energy expended doing that is not a part of resistance or efficiency for double ended boats.

So because the double ended hull (for all practical purposes) dosn’t drag water along w it. That work not required is efficiency gained.
So because or what I’ve said above I’m of the opinion that typical canoe sterned boats are more efficient.
That said they are only more efficient at speeds unattractive to most boaters so dosn’t have the impact that this otherwise would have. Sailboats do, however travel at these slow speeds because of lack of power to do otherwise (most of the time). When you see a sailboat under sail you’ll see almost no wake. So as you compare boats, those w less wake will be the most efficient. Those will (depending on speed) be the most efficient and usually be canoe sterned boats.

 

[psneeld]

I dont believe a canoe stern is more efficient than a transom boat that could have the same or similar underwater hull shape. Above the waterline hull shape only matters in chopper or worse seas or when heeling.

Tweeking underwater shapes can take on all sorts of forms.

Wouldn't take much for this to be a canoe stern....and many other including modern designs that aren't sleds.

 

[RBack]

Here's the Loxo 32 by the french sailboat manufacturer Pogo Structures. It's an atempt to make a seaworthy light and extremely fuel efficient motor boat. There are three engine alternatives and even one electrical version.

It's quite equal to my boat in terms of dimensions - but a bit more beam and space aft. It's also more box shaped and gives more efficient space for crew and passengers.

It seems to be very seaworthy and has traveled on the North sea in quite rough weather.
Cruising speed is 10-12 knots and fuel consumption at 12 knots is 0,5 l/h with both singel engine options.
At 8 knots (the cruising speed of my boat) this one uses 0,38 l/h with the 50 hp engine. The engine in my boat is 52 hp.
At 8 knots my engine currently burns 0,5 l/hour. Hope to tweek it down a bit after hull restauration and some small engine maintenance/tuning.

Now... it would be insteresting to know how much of that difference in fuel consumtion at 8 knots is due to the different engines and/or difference in hull shape.
Mine is a 4 cyl, 3,6 l, 1962 Parsons Pike Marine (Ford Trader/Fordson Super Major).
The 50 hp Loxo 32 uses a Volvo D2-50 (4 cyl, 2,2 l).

The Volvo is for sure much more fuel efficient from the start. But how much is hard to say. If I swapped to a Volvo D2-50, would I then also enjoy about 0,38 l/h?

Its (the Loxos) box shaped stern is only marginally below the water surface and therefore it won't drag a lot of water with it. Furthermore it can reach up to 16 knots with the 50 hp alternative and 20 knots with stronger engines. So it's of course a much more versatile creature than my canoe sterned thing.

I think its fair to say that the Pogo hull might be a bit tricky to use on a heavier trawlerish construction. Part of its efficiency is due to the ridiculously low weight (1,65 t) and ability to float high on the water. My boat weighs in at around 3-3,5 t.

As far as I can see, this is the kind of boat/hull that can outperform mine in terms of fuel efficiency if we look at size and speed - if we talk about single hull constructions that is.

 

[Al]

When I was at Coast Guard Station Ketchikan in the 1980's there were many old double ender wooden boats from the 1930's. They were still out commercial fishing after all those years and countless storms. They had to be very well built on a very good design to survive as long as they did.

Thanks for your service and making Ketchikan a temporary home away from home. The community of Ketchikan is with title of "A Coast Guard City" for reason. we enjoy a wonderful relationship and respect for the "Coasties".
Come again for a visit and see the improvements (On going)

Still a few double enders about though less in number, as horse power has taken over the design eliminating the elegant efficiency of a canoe effect through the water.

 

[Nomad Willy]

RBack,
You made a good point ... perhaps not realizing it.
There’s a road to very inexpensive trawler utilizing some of what you said above.

If a boat is light enough a typical old plywood cruiser like a Sabre Craft, Owens, and many others that can be found on Craig’s List for sale cheap. $500. — $1000 you name it even free. Some are usable.
Take the old gas engine out and find a 25 to 45hp diesel auxiliary. Good engines can be had for cheap too. And many are lightweight Yanmar’s.

There’s many light wood boats with planing hulls that are very inefficient at the speeds they were designed for. But keep them light and slow them down a lot and you’d have a boat with many of the features of a trawler. Lacking big time seaworthyness and other trawler pluses.
But good point Rback .. a square sterned planing hull can be as efficient as a typical trawler.

Gas engines generally burn about twice as much fuel as a diesel so all you need to have a trawler kinda-sorta that dosn’t look like a trawler is the above boat and engine. My trawler weighs over 15,000lbs so if you had a 26 (or so) that weighed 4000lbs it should be (miles per gallon wise) it would be more or less the equal of a trawler.

There’s a boat (club sorta) called terminal trawlers. Basically they make trawlers out of old sailboats ... they can be found so cheap.

The picture below is of a sailboat that the owner (Terminal Trawler guy) raised the foredeck and put a cruiser/trawler cabin on it. Has nice proportions I think.

Sorry my post is a little chopped up.

 

[mvweebles]

The exam question was are canoe sterns efficient? The answer is emphatically yes. For 100 years, designers have known its important to return flow back in place in a mannerly fashion. It's why wings have tapered trailing edges, why helmets on high speed skiers have torpedo training edges, and why ships and some trawlers are double ended at the waterline despite having a transom.

Personally, I think people spend too much time on design attributes and too little time developing seamanship skills. Almost seems like people try to buy their way into safety. As mentioned before, Joshua Slocum, one of the great single handers of all time, completed his circumnavigation on a near derelict hay barge. Good thing he didn't have TF to tell him the errors of his ways and how he needed twin rudders and a broad beam.

Peter

 

[hollywood8118]

But imagine how happy he would of been if he had them both
HOLLYWOOD

 

[hollywood8118]

Here's the Loxo 32 by the french sailboat manufacturer Pogo Structures. It's an atempt to make a seaworthy light and extremely fuel efficient motor boat. There are three engine alternatives and even one electrical version.

It's quite equal to my boat in terms of dimensions - but a bit more beam and space aft. It's also more box shaped and gives more efficient space for crew and passengers.

It seems to be very seaworthy and has traveled on the North sea in quite rough weather.
Cruising speed is 10-12 knots and fuel consumption at 12 knots is 0,5 l/h with both singel engine options.
At 8 knots (the cruising speed of my boat) this one uses 0,38 l/h with the 50 hp engine. The engine in my boat is 52 hp.
At 8 knots my engine currently burns 0,5 l/hour. Hope to tweek it down a bit after hull restauration and some small engine maintenance/tuning.

Now... it would be insteresting to know how much of that difference in fuel consumtion at 8 knots is due to the different engines and/or difference in hull shape.
Mine is a 4 cyl, 3,6 l, 1962 Parsons Pike Marine (Ford Trader/Fordson Super Major).
The 50 hp Loxo 32 uses a Volvo D2-50 (4 cyl, 2,2 l).

The Volvo is for sure much more fuel efficient from the start. But how much is hard to say. If I swapped to a Volvo D2-50, would I then also enjoy about 0,38 l/h?

Its (the Loxos) box shaped stern is only marginally below the water surface and therefore it won't drag a lot of water with it. Furthermore it can reach up to 16 knots with the 50 hp alternative and 20 knots with stronger engines. So it's of course a much more versatile creature than my canoe sterned thing.

I think its fair to say that the Pogo hull might be a bit tricky to use on a heavier trawlerish construction. Part of its efficiency is due to the ridiculously low weight (1,65 t) and ability to float high on the water. My boat weighs in at around 3-3,5 t.

As far as I can see, this is the kind of boat/hull that can outperform mine in terms of fuel efficiency if we look at size and speed - if we talk about single hull constructions that is.

I will admit I love the thought of a LWL lightweight passage maker bit the LOXO probably suffers if the crew brings more aboard than a toothbrush and a travel sized tooth paste.
Cool Idea for sure though
HOLLYWOOD

 

[BrianG]

But imagine how happy he would of been if he had them both
HOLLYWOOD

I love Slocum and have committed a few paragraphs to memory. But didn't he disappear at sea?

 

[Hippocampus]

Pogo has taken what was learned from the open RTW racers and applied it to recreational craft. Please note their motor boat is NOT a canoe stern. Nor is the Artnautica nor the Arksen nor was the Dashew designs. All the current motor boat designs aimed at providing super high efficiency allowing relative low hp engines are NOT canoe sterns. These boats were drawn on a blank page. All did NOT choose a canoe stern.
Please compare nmpg of these craft to canoe stern vessels. Doesn’t matter if you compare by displacement (weight) or LOA or LWL. In all cases the canoe stern vessels are more inefficient. Once you take emotion out of it it’s clear that design feature doesn’t lead to to peak efficiency.

 

[psneeld]

I think we have left the ballpark...

 

[mvweebles]

If "pizza slice" with broad transom is the most efficient and sea kindly, then we should all be looking at something like this. Perhaps repowered with a pair of JD4044NAs?

https://www.yachtworld.com/boats/2008/sunseeker-manhattan-60-3610817/

 

[RBack]

.. a square sterned planing hull can be as efficient as a typical trawler.

Yes, a planing hull can be as fuel efficient as a double ended boat (canoe stern) within the efficient speed range of the latter. The Loxo 32 is a good example of that. It doesn't drag much water in its wake and the turbulence is minimized.
In other words it's a construction that works very well within its own hull speed (before planing). The Loxo 32 is most certainly having a soft - perhaps barely noticeable - treshold over to planing when speeding up.

So...

If the hull shape of such a boat reduces turbulence by the same amount as an equally sized double ended boat, it can be as fuel efficient - easily driven through water at or below hull speed. If they're equal in that term, then the area of wet surface will probably play a relatively larger role regarding drag.

There are some limits then it komes to floating high like a cork in the water though. The water surface it self is fairly tricky when it comes to drag. But

Any how... such constructions lie the Loxo 32 are still however rather rare - for some reason.

I could pick any square ended boat that equals mine in terms of size/dimensions around the coast here and be fairly sure none of them would be able to be as fuel efficient at (let's say) 8,5 knots. All the "normal", local square ended motorboats of that size are dragging half of the Baltic sea behind them at that speed. Many of them are furthermore a bit wiggly at that speed. They're simply not made for it.

Then we haven't even discussed how the boats behave in rougher seas.
Well, the Loxo 32 is said to behave well and to be seaworthy. What else would they say? But it seems like it is actually very good. But seaworthiness (security) aside, it's also a matter of preference when it comes to how a hull should handle rough seas. I think the Dashews has got this rather well explained when it comes to their philosophy regarding those FPBs.

But in a world where fuel prices rise and CO2 emissions needs drastical reduction, there is surely a market for hulls being efficient also within hull speed range an not only at planing speed. The Loxo 32 is a good example. Cats are probably also getting more popular. And they're even better at fuel efficiency.

 

[Hippocampus]

The pizza slice actually makes a poor cruising hull. There was a long thread on this and several articles on attainable adventures. The thread involved Bob Perry a most remarkable NAs who designed many very famous canoe stern boats including Valiant. That boat caused the paradigm change from full keel to fin . He said( to paraphrase)
Displacement is required for a good cruising boat. That allows adequate stores, fluids, tools and comforts .
LWL is important. Overhangs make no sense given loss of hull speed, poor behavior in a seaway, expense. They were done to escape racing rules.
Attainable adventures points out as monohulls approach the hydrodynamics of multi hulls the difficulties in multihull design start to take effect. The old saying among blue waters sailors was “ a mono takes care of you.....you take care of a multi”. Although that may no longer apply in some designs for most performance models it does. These ocean going designs require exotics in construction, are very sensitive to weight and where it’s placed and more operator input. All things against the desires of cruisers. This has driven AP design and software but also made for the need of truly athletic, alert, smart crew with great endurance. The AA articles further point out the production designs that use the visual cues of the racers but not the constraints are unsafe as compared to the transom sterned, balanced hull developed through the late 80s -90s.

 

[Hippocampus]

The argument about turbulent flow at the stern with a “square”” ending is not borne out in modeling nor tank testing. That’s one of the reasons it’s been abandoned by all modern NAs in power and sail. Please read up on fluid dynamics and water air interface dynamics. Please read any of the boat builder sites. Please read the works of the NAs. To explain why the opinion of post #144 isn’t borne out by the physics, testing, experience and modern design would take longer than I’m willing to type. Please do your own homework. But basically you need to consider that you want laminar attached flow over the largest amount of your hull. You want to leave the least and weakest vortexes at all your trailing edges. When you look back on your boat you see the surface interface between air and water. Here it’s much more complicated as the totality of the exit of the entire hull is what’s important in determining parasitic drag. At the expense of being redundant tank testing, cad/cam, experience in the real world shows the transom to produce less parasitic drag when properly designed.

 

[mvweebles]

The argument about turbulent flow at the stern with a “square”” ending is not borne out in modeling nor tank testing. That’s one of the reasons it’s been abandoned by all modern NAs in power and sail. Please read up on fluid dynamics and water air interface dynamics. Please read any of the boat builder sites. Please read the works of the NAs. To explain why the opinion of post #144 isn’t borne out by the physics, testing, experience and modern design would take longer than I’m willing to type. Please do your own homework. But basically you need to consider that you want laminar attached flow over the largest amount of your hull. You want to leave the least and weakest vortexes at all your trailing edges. When you look back on your boat you see the surface interface between air and water. Here it’s much more complicated as the totality of the exit of the entire hull is what’s important in determining parasitic drag. At the expense of being redundant tank testing, cad/cam, experience in the real world shows the transom to produce less parasitic drag when properly designed.

One credible citation that a barge is more efficient than a double ender would be great. Would solve many things.

Thanks in advance

 

[RBack]

Perhaps there is too much focus on the stern alone here?
The functionality of the stern is still affected by the rest of the submerged part of the hull. Both in terms of drag and how it behaves in following waves.

Then there is a question of how deep the transom goes.
Is it completely above the WL, in level with the WL or are parts of it submerged - and in that case - how much?
How much can be chopped off of a cruiser stern before it's called a transom?
How do each and everyone define what they actually mean and do we even talk about the same things?
How wide and/or tapered can a cruiser stern be?
How is it tapered? Predominantly vertical with a keel, horizontally up towards the WL (with a broad transom) or something in between?

Oh, all those endlessly numerous factors!

Which anchor is the best anchor on a specific stern construction?

 

[psneeld]

Perhaps there is too much focus on the stern alone here?
The functionality of the stern is still affected by the rest of the submerged part of the hull. Both in terms of drag and how it behaves in following waves.

Then there is a question of how deep the transom goes.
Is it completely above the WL, in level with the WL or are parts of it submerged - and in that case - how much?
How much can be chopped off of a cruiser stern before it's called a transom?
How do each and everyone define what they actually mean and do we even talk about the same things?
How wide and/or tapered can a cruiser stern be?
How is it tapered? Predominantly vertical with a keel, horizontally up towards the WL (with a broad transom) or something in between?

Oh, all those endlessly numerous factors!

Which anchor is the best anchor on a specific stern construction?

Absolutely....I said it in a post before.....

It was also said by Hippocampus back in post post #14...... " The ocean doesn't see what's above the waterline too often if you are doing things right".

The discussion has gone into the many intricacies of hull design and you have to be way more specific than some general description of how a hull ends from a dock walker point of view.

 

[RBack]

Truly sorry in advance... but I couln't help it...

Sketching on improvements of the stern.