Canoe (or double end) boats efficient?

[Nomad Willy]

I said this on post #42 (page 3) and consider it is a good observation of at least some of what hippo had to say. Short keels actually have advantages but they must be used together w other things that are part of the boats directional stability features. Like sails, their own keels and rudders. W/o the sails the sailboats would be all over the place w their rudders having little leverage.

From pg 3,
“You are very very much into sailboats to the extent that none of us have ever heard of what you speak of. And of course sailboats have sails .. and tall masts. All of this must be involved in what makes the most seaworthy boat. For example w sails up the pressure on the jib and mizzen on the aft end of a main will offer a great deal of directional stability. Trawlers lack that. Also sailboats having sails aloft receive a great deal of roll stability .. that trawlers also lack. Sure they heel way over but they are stably fixed as heeled and don’t roll back and forth. Furthermore they aren’t subject to the inertia of the dynamically rolling and yawing boat.”

 

[BrianG]

I said this on post #42 (page 3) and consider it is a good observation of at least some of what hippo had to say. Short keels actually have advantages but they must be used together w other things that are part of the boats directional stability features. Like sails, their own keels and rudders. W/o the sails the sailboats would be all over the place w their rudders having little leverage.

From pg 3,
“You are very very much into sailboats to the extent that none of us have ever heard of what you speak of. And of course sailboats have sails .. and tall masts. All of this must be involved in what makes the most seaworthy boat. For example w sails up the pressure on the jib and mizzen on the aft end of a main will offer a great deal of directional stability. Trawlers lack that. Also sailboats having sails aloft receive a great deal of roll stability .. that trawlers also lack. Sure they heel way over but they are stably fixed as heeled and don’t roll back and forth. Furthermore they aren’t subject to the inertia of the dynamically rolling and yawing boat.”

I should pay attention since my 29' trawler has about 24' of mast for it's *steadying* sail.

 

[marcoh]

Here a link to another discussion thread about a large 74 ft double ender for sale

https://www.trawlerforum.com/forums/s35/diesel-duck-ellemaid-30194.html

 

[skipperdiego]

double ender

I confirm, as owner of https://dixdesign.com/ancilla.htm, the double ender is the best form of hull in following sea. Previus boat https://nautipedia.it/index.php/PANDORA_(DREAMLAND) was a disaster, almost impossible to go in fol. sea, very dangerous when rolling and waves were resonant, there was a moltiplication effect of the rolling

 

[Hippocampus]

Thanks guys. It’s like giving up on any addiction.

Getting into trawlers is hard in this covid age. Put in an offer on a N40. It had a mishap. So when owner worked on that he did multiple improvements and some expensive servicing. Things like replacing the electronics and pumps and so forth. He expects to recover his outlay. But doesn’t understand he’s well above market. So much so the next owner can’t expect to recover even a small fraction of his outlay when the boat is sold again. I hope the boat will sit for a few months and he’ll get realistic. In the meantime went to Annapolis for a mini show of KKs. The boat we were interested in was deemed to small by the bride. The one two sizes up she liked. But her first choice is still the N40.
Know from past experience all the FaceTime walkthroughs just don’t cut it. You need to physically go to a boat and crawl around. But you need to be safe. I think airplanes are still off limits for now.

Would note this thread is about hydrodynamics and the sea is the sea regardless if you’re on home brew or a mega yacht. At that level when talking about hull forms the same physics apply to power or sail. Continue to believe the entire design should be judged not just one feature. Continue to believe canoe sterns are just one feature. There are canoe sterns that do poorly in a seaway and those that do well. Same for other sterns. Neglecting other features such as rocker, gyradius, metacenter, prismatic coefficient, diagonals, A/B, beam/length, LOA/LWL, reserve buoyancy and so on doesn’t capture the totality of the vessel.
I was a big fan of Crealock and Perry double enders. Owned both. But experience has shown me transom sterns are just as seaworthy and don’t require the concessions a canoe stern requires. Speaking only of trawlers would note from Beebe on the transom stern has been the preferred stern. Nordhavn built only one model with a canoe stern. We saw this model multiple times and it’s drop dead gorgeous. But it had a short run and all the other models are transom. Why? It’s not due to ease of construction, nor money, nor marketing. But rather both the seafarers and the NAs did not see a canoe as the best choice.

 

[silverback]

I am sorry Hippo but You are wrong. The round the world racing yachts rarely if ever sail to windward as is generally understood.They reach almost constantly. Their huge wide sterns evolved from the transpac downhill sleds.
Nomad willy’s cathedral hull Got me pondering. What if you had a series of nozzles To break the surface tension? Would the effective wetted surface be diminished, thus less friction.
Dashew and others are very aware the the most efficient hull shape is a long skinny hull, which almost demands similar ends. Then all the compromises start. That is really where opinions vary.

 

[Nomad Willy]

Silverback,
How can that be?
To go a mile to windward it takes sooo much longer and while getting around one must travel south as much as north ect .......

 

[silverback]

They are so fast that they in effect create their own wind. They haul a following breeze forward. When course requires hard on the wind they crack the sheets to reach. Much faster and like multihulls the speed more than compensates for extra miles the have to cover. They are in my opinion bloody terrifying.
What do you reckon about the airbubble theory?

 

[Hippocampus]

https://cr4.globalspec.com/PostImag...ndMap_BEF2774F-FC75-7DCF-7A34E88CBAA5C069.jpg
Show me how you get to or leave the Southern Ocean without going to windward. Remember they start and finish in the North Atlantic. SB is spot on apparent wind moves forward as speed increases. From the sails point of view they’re beating. However, even allowing that as they go to and forth to the southern ocean they’re going to windward some of the time. The hulls aren’t the same sleds used for the transpac. Things have evolved quite a bit since the hulls used specifically for that race. For multiple reasons going DDW isn’t as fast as other points of sail.
SB is also right they would luff on a hard beat once they got going so vmg is better on a reach if judged by TWA but it’s a beat by AWA. Sheets come in as boat speed increases.

 

[Hippocampus]

Returning the the tread. Believe reserve buoyancy has a lot to due with how you feel on a boat with seas coming from astern or on the stern quarter. If the boat rises nicely and the wave passes by its no biggie. But if the stern lags you get green water. It’s harder to achieve reserve buoyancy with a canoe stern. Would think a canoe stern boat would be more sensitive to weight in the ends as well. You could get around this by having the canoe above the static water line but then would lose lwl for the same loa. Don’t have the experience you guys have under power but know all the canoe stern sailboats I’ve had swat really bad compared to transom stern boats under power. Also think they get squirrelly when surfing down wave faces. That maybe design specific but have thought because they don’t rise as fast as soon as you’re off the perpendicular just a little bit there’s more surface face presented to the wave so it’s harder to straighten out just when the rudder has less effect than usual. Thoughts?

 

[klee wyck]

Returning the the tread. Believe reserve buoyancy has a lot to due with how you feel on a boat with seas coming from astern or on the stern quarter. If the boat rises nicely and the wave passes by its no biggie. But if the stern lags you get green water. It’s harder to achieve reserve buoyancy with a canoe stern. Would think a canoe stern boat would be more sensitive to weight in the ends as well. You could get around this by having the canoe above the static water line but then would lose lwl for the same loa. Don’t have the experience you guys have under power but know all the canoe stern sailboats I’ve had swat really bad compared to transom stern boats under power. Also think they get squirrelly when surfing down wave faces. That maybe design specific but have thought because they don’t rise as fast as soon as you’re off the perpendicular just a little bit there’s more surface face presented to the wave so it’s harder to straighten out just when the rudder has less effect than usual. Thoughts?

You are digging your hole deeper here Hip....
More reserve buoyancy since the taper in the 'canoe' is not just to the center line but also from the water line to aft continuing above the water line, of course. On my two there is 4'and 5' more length on deck than there is at the water line. That is alot more hull (reserve buoyancy) to respond to that sea as it attacks from astern and makes the whole hull more resistant to extra weight, not less.
Isn't this the entire reason a bow is shaped like it is on all boats and serves the vessel well when pounding into head seas? Ever seen a sea boat with a square bow?
For fast boats, no need for this on the stern, but for slow boats like mine, the waves can hit from ahead or astern so perhaps it make some sense that both ends look the same.

 

[BruceK]

.... Ever seen a sea boat with a square bow?
....

This gets close. It`s the replica of Captain Cook`s Endeavour:

 

[silverback]

Hip, i have explained it. I know you must go to windward to circumnavigate. But if you reach in a fast light displacement hull you will cover more miles but get there quicker. Again the wider transom is for running and reaching speeds.
Klee, that is correct.

 

[hollywood8118]

You are digging your hole deeper here Hip....
More reserve buoyancy since the taper in the 'canoe' is not just to the center line but also from the water line to aft continuing above the water line, of course. On my two there is 4'and 5' more length on deck than there is at the water line. That is alot more hull (reserve buoyancy) to respond to that sea as it attacks from astern and makes the whole hull more resistant to extra weight, not less.
Isn't this the entire reason a bow is shaped like it is on all boats and serves the vessel well when pounding into head seas? Ever seen a sea boat with a square bow?
For fast boats, no need for this on the stern, but for slow boats like mine, the waves can hit from ahead or astern so perhaps it make some sense that both ends look the same.

Actually a bow doesn't need to flare out to provide reserve buoyancy.
HOLLYWOOD

 

[klee wyck]

This gets close. It`s the replica of Captain Cook`s Endeavour:

With a canoe stern, no less.....
And didn’t that Captain end up on a reef somewhere North of you?

 

[klee wyck]

Actually a bow doesn't need to flare out to provide reserve buoyancy.
HOLLYWOOD

Canoe bow....upside down, but water tight to 40’ above the water line.

 

[hollywood8118]

Actually those maxi, open 60, and all those round the world boats are designed to plane. Think of them as a really big windsurfer. They plane upwind, downwind, on a broad reach where they typically have the best VMG.


HOLLYWOOD

 

[BruceK]

With a canoe stern, no less.....
And didn’t that Captain end up on a reef somewhere North of you?

Yes, the ship hit a reef under his command, fortunately they got it off and effected repairs. Here`s a pic of the stern:

 

[psneeld]

Seems li,like, some of the discussion diverges when discussing large waves/swells and breaking waves.

All the reserve buoyancy can't get you above a breaking wave quick enough from keeping you from taking a big one aboard.

But pointed stern will probably be better than flat.

Then .....when a boat gets big enough, things become less worrisome.

 

[FF]

"Actually those maxi, open 60, and all those round the world boats are designed to plane. Think of them as a really big windsurfer. They plane upwind, downwind, on a broad reach where they typically have the best VMG."


I see them as a modern version of an old sandbagger which rolled up on the hull to lift the rest of the boat out of the water. More like a one hulled catamaran from underwater.

 

[Hippocampus]

Think we need a NA to chime in. If beam is brought all the way aft and then abruptly stops it’s a transom stern. If it tapers is a gradual curve it’s a canoe. The transom will have more volume and more reserve buoyancy. This will be even more apparent when the curve on each side meets in a line (double ender). I’ve lived with all three. It’s very evident when you want to put stuff in a lazerette. One of the boats had a bit of tumblehome making for even less volume aft.

Before passage we’ve learned to take all the heavy stuff out of the lazerette and unweight the stern to the degree possible. I know from experience this improves behavior making steering much easier and boat drier in following seas. This has been true with all the sterns I’ve sailed with.

Psneeld is right boarding breaking waves are a different kettle of fish. Sometimes you can’t rise fast enough or you don’t have adequate freeboard to escape being pooped. However, the more reserved buoyancy the faster you will rise and the faster you will clear the decks. Also it’s now real common for current sailing transom sterns to not be dependent on scuppers. The aft end of the cockpit being entirely or partially open. We did a Marion Bermuda on my Tayana canoe stern. Got repeatedly pooped . Scary as all get out to be at the wheel and have the entire boat under water as you wait for it to rise.


Hollywood is right these boats plane as soon as there’s enough wind. For them it’s all about wetted surface and parasitic drag.

Take a box and put it in the water. Have a third in the water and 2/3 above. Have a wave strike it from any direction except perpendicular to a face. Wave strikes a triangular face at an angle. There will be less force trying to get it off track.
Take a lens or lozenge shaped object. Again floats 1/3 in the water. Get the opposite. Except when struck exactly parallel to its long axis it will present more surface area at a less acute angle to the wave face.
To get around all this both the sterns on the Pacific SeaCraft and the Tayana had the canoe part of the canoe stern out of the water. Then it did provide reserve buoyancy. But at the expense of hull speed. Returning to the OP these boats are inefficient.

 

[psneeld]

Another consideration is whether or not you are trailing a drogue.

 

[Hippocampus]

Best thing since sliced bread. Had a Jordan series drogue on the last boat. Beautifully made. Only problem is it’s heavy. Not supposed to use dyneema to decrease weight as that makes retrieving it more difficult and can’t use a trip line to retrieve it backwards. When last boat was built for me had large backing plates installed under stern cleats. Had solid grp instead core for that section of deck. Had cleats moved all the way aft to prevent chafe. So it’s not just getting a drogue.
Will probably get both a drogue and a sea anchor if we do passage on next boat. Friends tell me to be truly effective a sea anchor needs to be quite large. Makes retrieving it nearly impossible. Needs to be much larger than what fish boats use to stay near good fishing grounds when they need to take a break.
Have dragged warps to make steering easier. Never deployed the JSD in anger but did try it out to make sure we could do it. It’s not a trivial thing to do. Takes at least two unless you’re Superman. Probably easier on a powerboat that has there’s no windvane or other obstacles.
If you’re interested there’s a good discussion at attainable adventures about it.

 

[psneeld]

Every drogue I have ever used kept the stern square to the waves or aligned with the direction of travel.

 

[FF]

As a boat increases speed the bow begins to climb its own wave , when out of power the bow is high and the stern is lower. How much lower depends on its underwater volume.

The depressed stern drags water with it , the dragged water contains energy which holds the boat back.

The energy placed in the water will be dissipated in the boats wake ,only after a while.

At speed the energy can be enough to cause the following wave to break, the reason double enders are frequently awash aft.

Herrishoff put overboard trim tabs on a few of his boats at owners request but gave up on it as the boats were still slow.

 

[RBack]

This double ended thing came out of the water a few days ago and is now going to receive a long awaited restauration of the hull.

 

[BrianG]

This double ended thing came out of the water a few days ago and is now going to receive a long awaited restauration of the hull.

What is that big flap/tab called on the stern? haven't seen that before. What's it do?

 

[RBack]

What is that big flap/tab called on the stern? haven't seen that before. What's it do?

Its quite common around here on this type of hull. At least it became common when the old traditional double ended fishing boats got new and stronger engines. It prevents the stern to dig down when hull speed is about to be exceeded. In some constructions it can probably add a tiny tad of speed, but not much really. I don't know if my boat actually benefits in terms of any speed whatsoever. I would need to do some sea trials with and without.

This one is about to be removed since it's in a rather bad condition. I'm not entirely sure if it'll be replaced or not.

 

[Nomad Willy]

Think of it as a Dole Finn on steroids.

 

[Hippocampus]

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.