why does this 1986 steel Junk have holes in rudder?

[Squidly-Diddly]

Hull seems to be "character" instead of modern, but what is with the perforated rudder???

Is that the only piece of steel they had?





http://chinesejunkboats.tripod.com/i...target=tlx_new

[hoytedow]

Maybe it was too big and this was the easiest way to reduce surface area?

Or termites.

[michael pierzga]

aww jeez...dont you know anything !!!.. The two obvious technical reasons for holes......first, its cheaper to antifoul because of the reduced surface area and secondly , fish on port side can fearlessly crack jokes and tell sea stories with their mates on starboard side without swimming all the way around the rudder, huffing and puffing, exposed to young boys with nets.

[Submarine Tom]

To make it lighter?

Gosh, they're not even holes, they're diamonds!

-Tom

[Angélique]

Think Quest ---> Rudder

.... Another traditional Chinese invention was the 'fenestrated rudder', which is simply a rudder with holes made in it. The Chinese soon discovered that while easing the task of turning the rudder through the water, the holes did not appreciably diminish its steering function. However, it was not until 1901 that fenestrated rudders were introduced to the West. Until that time, a coal-fired torpedo boat traveling at 30 knots was unable to turn its rudder at speed. Fenestration made this possible.

Wikipedia Junk

.... From sometime in the 13th-15th centuries, many junks began incorporating "fenestrated" rudders (rudders with holes in them), probably adopted to lessen the force needed to direct the steering of the rudder. ....

Wikipedia Rudder

.... Also, many junks incorporated "fenestrated rudders" (rudders with holes in them, supposedly allowing for better control). ....

Google "fenestrated rudder" for more info...

Cheers,
Angel

[hoytedow]

Thanks, Angélique!

[Angélique]

Continuation of the first link above.....

The earliest rudders in China were what is called 'balanced' rudders. This means that part of the blade projected in front of the post. Such rudders are easier to use, but Europeans did not adopt them until the nineteenth century. One of the earliest ships to use such a rudder was the Great Britain of 1843. The British were in the forefront when it came to adopting Chinese inventions for naval use, with this as well as the square-pallet chain pump as a bilge pump and watertight compartments in hulls. It is no exaggeration to say that the superiority of the British Navy was to a large extent due to its readiness to adopt Chinese inventions more rapidly than other European powers.

Cheers,
Angel

[yipster]

some USA wwII divebombers also used ,,what was that word,, perforated arelons
less power against force and more resoning like boundery layer flow, there is more on the I net
smart boats those junks

[Angélique]

She looks like a Colvin . . . .

Multi-chine and round bottom junks, based on the Hainan junks, range from 42’ to 150’ in length. The most popular ones are OOTHOON at 41’ (shown above), K’UNG FU-TSE at 48’ (shown below), and LUK CHIN at 54’ which have been built in both steel and aluminum. The 54' junk has also been built as a round bottom steel hull. The larger sizes are usually round bottom since, in larger sizes, most builders prefer this type of construction and are equipped to handle the bending of round bottom frames. These are excellent sea boats. The larger ones incorporate daggerboards, while on the smaller ones used for yachting I have substituted a long shallow keel which opens up the whole interior to an infinite variety of arrangements. Most of them have made long voyages and, as such, I like to keep the engine and fuel tanks very close to the center of floatation and center of buoyancy. I also use the engine room with bulkheads at each end to isolate all machinery. This provides good working conditions around the engine. Most vessels have access doors for passage through the engine room; whereas, in others the engine room bulkhead is not pierced and access is from the deck only.

Cheers,
Angel

[Angélique]

Think I found the boat or something similar . . . .


click pic to enlarge


click pic to enlarge

Cheers,
Angel

[Angélique]

Ah, the one in post#1 is a little bigger and she's for sale . . . .



Cheers,
Angel

PS - Yipster, the word was "fenestrated" - - ‘‘ pierced with one or more openings ’’ -

---> fenestrae ~ windowlike openings

[tom kane]

Inboard powerboats use the same idea in the USA.

[Angélique]

Besides the benefits of lighter steering I think fenestration also adds drag . . ? ?

Cheers,
Angel

[Squidly-Diddly]

Seems like a 1986 steel boat should be able to turn the rudder without trouble or drag inducing holes.

How can all those holes being blasted by prop NOT reduce steering and create drag VS solid rudder?

[rwatson]

Its just a bit of inefficient nostalgia since the trim tab

http://en.wikipedia.org/wiki/File:Control-tab.png