so in my recent research into ranger tugs and mini tugs their building in the states , im curious about the design benefits of a round stern , thinking it was older style for clinker boats and displacement hulls , any reason why it could work on a modern powerboat,
now to buy a ranger tug 21 will set you back $85K anyone know of any hulls around up to 16 ft that has these round stern shapes
I'd say that its all about drag at displacement speeds. Planing hulls suck a lot of water along behind them until they get on the plane (out of displacement mode). Slower displacement hulls benefit from the tucked-in canoe-stern, which doesn't cause water to be dragged along behind.
Hello catshark,
from my reading a rounded stern's main advantage is to part overtaking seas in a slow displacement boat.
They have no benefit whatsoever to a modern planing boat.
For a given length of boat they reduce usable space and reduce planning area where it is most needed.
There are successful canoe stern planing boats, lookup Bartender boats, but these are a thing of the past.
If a modern planning hull has a rounded stern it is only a styling exercise.
I have seen rounded stern planning hulls in Europe and they needed hull extensions no perform, why bother?
In general, no advantage, plenty of disadvantages.
Lots of old pro fishing boats were round stern, reasons varied, lots of big trawlers had to pull nets with the stern into the wind/sea, old setline boats reversed to pull up their lines, and almost all had a bar to cross with break walls like today, and a round stern let waves pass when coming in, and allowed "surfing" without broaching, and fuel economy was a big deal, a round stern reduced drag considerably none of those things are relevant today. There is a few different styles of round stern, there was canoe stern, counter stern and a double ender that was the same both ends (think Manly Ferry) lots of modern Tugs are kind of round-ish and can go backwards, sideways or frontwards with ease.
That design is all good until the weather gets harsh then is hobby horseing and rock and rolling all the way home.
Why?? can't see any reason for that to happen.Originally Posted by chris69
well few different reasons quite interesting , yes off course the ferrys yes
Double enders are carval hulls thats why, there's no chine for a bit of stability that's the way they used to build the old trawlers they defiantly don't build them that now for that reason.
Almost any boat over about 18' long and under 70' and built out of timber is of Carvel construction, Carvel is just the way the planks are butted edge to edge, not over lapped (Clinker) not many decent timber boats are built now, most are steel, fibreglass or aluminium. Being Carvel will not make a boat "hobby horse" but, being round bilge (no chines) they can roll a bit, but underwater design can mitigate roll, being deep draft displacement hulls, even this had two designs when it came to the keel, (planked heel, or deadwood). Most "hard chine" workboats were either ply or strip planked, laid diagonally, usually multi layer in different directions, having a chine kind of negates a round stern construction, both have advantages, but cost to build is seeing most of these timber boats disappearing from use, plus most big trawlers are not operating these days with license buyouts and so on.
A planing hill would still see a reduction to drag with a curved bum. Unless you are going sufficiently fast so as to avoid displacing any water (i.e. race boat doing 200 km/h) you are still losing efficiency with a square bum. The bigger the rooster tail you see behind your boat, the more energy is being wasted. Like comparing a hatchback to a tear drop shaped supercar, the drag of the hatchback is vastly greater.
With any outboard powered boat, it would be near impossible to make a tangible reduction to drag while still leaving space for the motor (which happens to sit in the highest drag location anyhow). So in theory, you could make a slightly faster and more efficient hull but too many compromises along the way, hence the lack of hulls designed in that manner...
been checking out some carval hull shapes too some mighty fine craft work back in the day
like these Nordic 21 style of boats too , make a nice river cruise but i think these are fibreglass , be choice to buy a project hull like this and make up a little wheel house for it but again its ones aspiratons vs ones limitations but then again when you got an itch you just gotta scratch it
cheers thanks for sharing , in my town i keep an eye on a older gentleman who works on wood boats still caulking and doing bits and what not . wooden boats are charming
Timber boat building was an art, no doubt about it, most timber boat builders have gone now, there was a couple of pretty famous names around, I think there is only 2 big timber trawlers in Wollongong now, there used to be about 10, well built and will last near forever until neglect kills them off. I once worked weekends with a builder doing a 65' Tuna boat, standard Carvel planked, but, all planks were full length, not a join in them, he had the timber cut, milled and dried to his specs, all copper nailed and "rovings" (washer kind of things) riveted over on the inside, all done with a hammer, and a big "dolly" to bend the end on the inside, never did see it launched, and I heard it sunk a few years later after a collision somewhere.
Finn 7's or Finn 8's would be the smallest double enders I know of in this country. Very sea kindly shape for a displacement hull. There was a double ended trawler called the Trader Horn which has now rotted away in Yamba that the older blokes couldn't say enough about it's ability to work rough water. It was a Woodnutt build.
nil carborundum illegitimi
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