This question is inspired by something in the James Bond film The Man with the Golden Gun, but the question has nothing to do with the movie, so GQ seemed the best bet.
In the scene where they are having a boat chase through the canals of Bangkok, the boat motors have long–perhaps ten feet or more–driveshafts with propellors on the end, extending straight back out of the engine’s crankshaft.
Is this common on boats in the Bangkok canals; and if so, why? What would impede a differential arrangement, such as in a regular outboard motor? Are the canals so shallow that this is the best way to get a propellor in the water?
I don’t know if canal boats are still powered this way–I was only in Bangkok once, 15 years ago–but the “swallowtail boats” you describe are powered by automobile engines which can’t be submerged or near the water, so they have a long propeller shaft coming off them. The shaft must be long so that the angle of attack (not the right term I’m sure) of the propeller blades is effective in pushing the boat through the water.
I was there in 2009 and took a ride on a major river there. Yes there where long narrow tour boats that had long shafts attached to car engines there. They were common on the river.
Yes. They’re called long tail motors. The wiki explains a great deal:
Basically, they are cheap and practical. The prop can be lifted out of the water to avoid obstructions or shallows. In the US, Mud Buddy motors are more popular for similar applications (but specifically for duck hunting). Youtube has videos of them going through four inches of soup and weeds. Go Devil makes a long tail motor that is about the most similar (though way better engineered) motor to a long tail that you’ll find in the states.
Both Mud Buddies and long tails are inferior to a traditional outboard in power. They rule the shallows, but if you have to navigate open water in a stiff wind with a aluminum plate boat full of hunters, dogs, and gear, you’ll be moving slow.
I was in Bangkok 1 - 2 years ago. Our guide explained that the rivers / canals in Bangkok were subject to plant infestations. I want to say something like water lilies, but I think that’s not exactly correct. The long tail boats are designed that way so that the propellers can be lifted out of the water to avoid snarling on the prop. (And also, perhaps, to allow easy cleaning if they do get snarled.)
I road in a couple of those boats and they’re pretty fun.
I’m trying to think what those are called. “Water lettuce,” I think. Maybe. Just asked the wife, and being a city girl, she’s not even sure what they’re called in Thai. But I have heard they were introduced in the mid- to late 19th century from Japan – I have a vague recollection that some of the plants were a gift from one royal to another – but soon flourished into pest status. They can be a problem.
I imagine it was an economy move too. Simpler to weld/bolt a simple long shaft to a car engine (from a derelict car?) than to somehow acquire a pair of 90-degree differentials in protective casings. The normal outboard motors are designed to run vertical (or have the dual 90-degree gears) but most other engines want the sump on the bottom. At least in North America, a new outboard motor is more expensive than a very old car whose transmission is dying. I assume the same goes for over there?
Aha! I think this is it: Water hyacinth. Particularly this. And I’m not sure if the original plants were a gift from Japan or if the seeds were deposited from the hulls of visiting Japanese ships, but Japan was somehow involved.
