Canoe stern vs ????

[Jim Cate]

Re the stern slap (bass drum simulator) issue when in a marina berth with incoming seas:

Turn the boat around in the berth!

Seriously, we've had our current yacht for 21 years of liveaboard cruising and she has a sorta wide sugar scoop stern and yes, under the wrong conditions a noisy slap is heard. But in all those years it has happened only a few times, and I surely would not let that prospect influence my choice of designs. (And many skippers of such boats prefer to berth stern-in all the time, and this cures the problem for sure).

And in some 65,000 miles logged in this boat we have not had any issues of control or boarding seas when sailing downwind in sporty conditions. The a/p has been able to manage. We have not experienced anything worse than F8 for sustained conditions, though

Jim

[massnspace]

Well, my original question was chewed, stewed and brewed over….again and again….talk about thread drift!

Thanks to those who actually read and attempted to answer my original question, and “thanks” to the others who completely ignored it and ran to the east and north…

I am still looking for my next boat…..offshore capable….and will continue to look….considering several different categories of vessel…

[TJ D]

Well, since it went dormant for months, Some of us must have figured a little thread drift was ok... Good luck with your search.

[massnspace]

Originally Posted by TJ D

Well, since it went dormant for months, Some of us must have figured a little thread drift was ok... Good luck with your search.

That’s incorrect.

The thread drift started almost immediately (go back and see!). So it took a very, very long time for me to read any relevant posts….i don’t really respond to posts that have nothing to do with my original question….

[TJ D]

Ok, I'll bite. I think the shape of the stern is about #11 on considerations when trying to determine how a boat will handle offshore. I just don't think it matters very much, frankly. As Mr. Perry said, he did it for looks.


Far more important is the underwater profile of the hull, how much hull shape changes with degrees of heel, ballast/displacement ratio (more importantly, how deep the ballast is-where is the VCG of the boat?)


Foil efficiency, rudder area, rig CE in different sail configurations, in my view, every one of these things will easily impact a boat's performance more than stern shape.



I don't really think this is helpful to you, and I'm sorry about that, I just don't personally put the stern as a determining factor in how a boat will behave.



All the best-I do hope you find your perfect boat.

[El Pinguino]

Originally Posted by massnspace

That’s incorrect.

The thread drift started almost immediately (go back and see!). So it took a very, very long time for me to read any relevant posts….i don’t really respond to posts that have nothing to do with my original question….

I've gone back to the OQ and still don't understand it

' but some other boats have what I think is a referred to as a “wineglass” shape, and still others seemed pinched off really high.'

I've always thought that a 'wine glass shape' in this context referred to the midships hull cross section.

[sailingharry]

Originally Posted by El Pinguino

I've gone back to the OQ and still don't understand it

' but some other boats have what I think is a referred to as a “wineglass” shape, and still others seemed pinched off really high.'

I've always thought that a 'wine glass shape' in this context referred to the midships hull cross section.

I think you are correct. Or at least, you and I are in agreement, so who cares what the rest of the world thinks. There was a Cherubini Ketch in our creek yesterday, so they are in my mind. Here's a pic of one, with what I would call a "wineglass stern."

[Don C L]

That's funny, I thought a bunch of good responses to the original query were in there.

As far as pinched pretty high, I assume that refers to a boat like the Downeast 38?

[jordanbettis]

Originally Posted by massnspace

but some other boats have what I think is a referred to as a “wineglass” shape, and still others seemed pinched off really high.

My boat has a wineglass transom and while it's the prettiest kind of stern by far it's also not a good use of space. The lazarettes are small and awkward.


If your goal is lazarette space then the modern wide-ass wedge shape is the most efficient.

[Bowdrie]

Originally Posted by sailingharry

There was a Cherubini Ketch in our creek yesterday, so they are in my mind.

Be still my heart.
All the right curves in all the right places.

[Thomas1985]

Originally Posted by Don C L

That's funny, I thought a bunch of good responses to the original query were in there.

As far as pinched pretty high, I assume that refers to a boat like the Downeast 38?

It cracks me up looking at our boat in line at a marina. There’s no missing it lol

[Toccata]

Quote
Quote:
Originally Posted by TJ D View Post
Well, since it went dormant for months, Some of us must have figured a little thread drift was ok... Good luck with your search.
That’s incorrect.

The thread drift started almost immediately (go back and see!). So it took a very, very long time for me to read any relevant posts….i don’t really respond to posts that have nothing to do with my original question….

Reply
My fault!
I thought as I'd just finished a 2 year restoration of a boat that has a canoe stern, I'd post a photo on the subject to continue a nice rambling discussion about boat design features.....intended to be a neutral chat amongst online acquaintances.
Not wishing to start a fight at all.
The canoe stern seems to leave one less ripple in the water compared to the square transom of my motorsailer, but that is quite probably as much a feature of the underwater shape as thew stern.
The motorsailer has a scheel keel not quite as small (fore/aft) as a true fin and a separate skeg hung, she sails beautifully on all points.

[K_V_B]

Originally Posted by Briis

As said above, double ender's rear becomes your front when the situation turns into utter s*it sailing with bare poles in Force 10 with 30-foot crashing waves pooping you over like a temporary submarine, with or without drogue. Your nice shiny fancy fiddly wide and large plastic flat rear plate becomes your death sentence once the 15-ton wave crashes on you.

I do not know of any case of a flat transom being stove in by a wave. I don't think you know either. In fact, hulls suffering major structural damage through wave action alone is not something that really happens as far as I am aware.

No wonder the heavy-weather and survival/life- boats are almost all double enders throughout history.

If Colin Archer were alive today he would probably not be designing double enders. His present day colleagues certainly aren't. Life boats nowadays rarely have pointed rears. They often even don't have pointed fronts either. Or are completely round, or square, as all they need to do is stay afloat.

Every design is a compromise that is partly dictated by the constraints the designer is working under. We are not bound by the same constraints as 19th century mariners.

[K_V_B]

Originally Posted by rslifkin

A narrow stern has efficiency advantages at low speed and in following seas may behave a bit better,
.

The thing is that "following seas" is largely an illusion. As long as you show a wake you are still moving forward through water.

As a kid we would sail optimists in the North Sea. One thing I quickly got is that those waves coming at you aren't actually coming at you. That is an illusion. Waves are caused by water moving up and down, and phase differences in the movement along the water plane give the illusion that the waves are moving in a particular direction. But they aren't.

Just throw a cork over board and see what it does. Us kids in optimists would bob around as corks on the waves, moving up and down with them, and learning not to fear them.

So when sailing down wind the waves aren't really overtaking you. You are actually still overtaking the waves.

[rslifkin]

Originally Posted by K_V_B

The thing is that "following seas" is largely an illusion. As long as you show a wake you are still moving forward through water.

As a kid we would sail optimists in the North Sea. One thing I quickly got is that those waves coming at you aren't actually coming at you. That is an illusion. Waves are caused by water moving up and down, and phase differences in the movement along the water plane give the illusion that the waves are moving in a particular direction. But they aren't.

Just throw a cork over board and see what it does. Us kids in optimists would bob around as corks on the waves, moving up and down with them, and learning not to fear them.

So when sailing down wind the waves aren't really overtaking you. You are actually still overtaking the waves.

The issue isn't actually one of how the water is moving. It's a matter of how the boat encounters the wave. Boats behave differently when the front side of the wave lifts the bow first vs when it lifts the stern first (and the stern or bow respectively ends up on the back side of the wave last as it passes).

The game also changes in a really small boat where it's much smaller relative to the wave. Then it's like a cork. But with a longer boat the wave will induce a pitch change as one end of the boat is on the wave while the other is in the trough in the worst case ratio of boat size to wave length.