Thailand longtail type propulsion pro/con?

[valhalla360]

For those who think they can't go fast:

https://www.youtube.com/watch?v=PbGLWHxeru0

[rslifkin]

For going fast, I'm not sure the longtail is necessarily a better solution than a conventional outboard, but it's certainly a heck of a lot cheaper. You can use any engine you can get enough power out of vs having to buy a pre-built, high powered outboard (or several) off the shelf for rather high prices.

[mikereed100]

Originally Posted by boatman61

I've always felt these would be great for Wharrams...

There was a Searunner cat knocking about SE Asia a while back with a single longtail mounted between the hulls. I think it would be even more suited to a Wharram with the simplicity vibe and all, especially in a Thailand build.

[black_sails]

Originally Posted by SailingHarmonie

You have decided. You want one. SO do it. What anybody else says does not matter. What do you want from here?

Umm further advice about future problems or troubles I may encounter? Ideas about how to mitigate or work around those problems if my situation still slants in favor of using a longtail propulsion? Finding other fans of the design who are probably out there but share what I assumed correctly to be an unpopular aesthetic because it's unfamiliar to those outside southeast asia?




I'll admit my biggest potential problem - the control method. Every video I see has a guy kneeling on a box with a long leverage handle to control the prop angle AND depth. This is no better than an outboard with a handle in the back of your fishing boat and NOT what i'm hoping to end up with, fine for a small lake, nothing i'd want to sit on more than 15-20 mins. The big ones on catamaran have guys just standing but they're still holding it like an old style rudder. So I find myself wondering how to convert it to a steering wheel and some kind of trim tab (which technically would make it controllable by an autopilot if I got that far anyway) without losing the ability of having the long prop shaft 'bounce up' when hitting an obstacle without damage.



I'm also unsure how a given amount of downward trim pressure rides through waves - you can see the guys leaning kinda hard when going high speed They're just doing it all by feel and instinct but it might actually be VERY critical to how well the prop performs in the water - again I don't know, not having a chance to interview people who use them.

[black_sails]

Originally Posted by valhalla360

For those who think they can't go fast:

Also a nice example of why the engine doesn't have to look ugly if you detail it. : P

[black_sails]

Originally Posted by skipperpete

I repowered a 40’ long Australian yacht that had a long tail with a 30 hp Diesel engine.


the owner liked it so much he did 2 trips to Bali from Singapore and finally up the straits of Malacca for his shiny new Yanmar to be installed.
There’s some peculiar ( to me) increase in efficiency with surface piercing propellers but it only seems to work well with high speed vessels like fast patrol boats...... and Thai cargo and racing boats[emoji848]

Sounds like an open ocean journey to me. >_> I wonder what sea states he encountered and how well the system worked. Clearly it DID work so i'm not just completely cracked thinking it's viable.


And you just said yourself "seems to be an increase in efficiency" from personal experience, yes? Thats why i'm wanting to document or talk about it/some people are kind of poo-pooing something they don't seem to have personal experience of and I think that's unfair. I just want it's merits to be fairly contrasted and compared to other solutions, it's not ONLY 'cheap'.

[black_sails]

Originally Posted by valhalla360

The big ones aren't really suitable to displacement cruising boats. A 200hp automotive engine is overkill to reach displacement speeds...and they are crazy noisy.

They use them out on rough water so the angle isn't that big of a deal.

I'd be curious if just using an engine larger displacement than necessary to be understressed, and i'm not sure why nobody has ever thought of putting a muffler on one. It's not like... banned by the design or anything... maybe even an underwater exhaust with pipes along the long prop shaft for when it's under at least then it's quiet, who knows.



I'm not planning on using one on anything like a trawler - but a slender hulled cat going above displacement speeds is likely in my future. I'm simultaneously not sure why one COULDN'T be used on a displacement monohull, other than they seem to come into their own at higher speeds.



How rough of water, what sea state or wave height? This seems to be a big potential argument "the prop will just bounce in and out of the waves and not get you anywhere" being implied.

Originally Posted by valhalla360

Probably the biggest issue is they are a workout to operate. It's a full body exercise to turn a 300lb V6 with a 15ft drive leg.

THAT I will completely agree with. I think i'd like to figure out a way to convert things to a steering wheel and some kind of power trim tab control while keeping their other benefits.

[mikereed100]

Keep in mind the old adage "need begets solutions", or did I just make that up? Longtails are used in Thailand because they are well suited to local conditions and ecomomy. They are pretty much exclusively operated in flat water on flat bottomed boats that are frequently beached. Plus, any engine they have lying around can be used without marinization. Downsides are that they are gawdawful noisy, clumsy to maneuver and take up a lot of space in the boat. I suspect if they could afford outboards they would use them, as they do in neighboring Malaysia.
For a world cruiser such as you are building, an inboard diesel makes more sense. I can't imagine trying to wrestle a longtail in a seaway. Keep in mind that close maneuvering is done by lifting the often still spinning prop out of the water, moving it to the side and dropping it back in again. On the cat I saw, the prop was fixed amidships and only raised up and down. Steering was done with the rudders. This boat was also used only in the flat waters around the Philippines.

Before you commit, why not take a trip to Thailand and have a look? Worst case scenario you come home with a sunburn and cornrolls.

[valhalla360]

Originally Posted by black_sails

Also a nice example of why the engine doesn't have to look ugly if you detail it. : P

Keep in mind, the race boats are not average Thais but the HiSo guys with money to burn.

[valhalla360]

Originally Posted by black_sails

I'd be curious if just using an engine larger displacement than necessary to be understressed, and i'm not sure why nobody has ever thought of putting a muffler on one. It's not like... banned by the design or anything... maybe even an underwater exhaust with pipes along the long prop shaft for when it's under at least then it's quiet, who knows.

I'm not planning on using one on anything like a trawler - but a slender hulled cat going above displacement speeds is likely in my future. I'm simultaneously not sure why one COULDN'T be used on a displacement monohull, other than they seem to come into their own at higher speeds.

How rough of water, what sea state or wave height? This seems to be a big potential argument "the prop will just bounce in and out of the waves and not get you anywhere" being implied.

THAT I will completely agree with. I think i'd like to figure out a way to convert things to a steering wheel and some kind of power trim tab control while keeping their other benefits.

I think the issue is they pull them from old cars and not many 30-50hp cars kicking around.

While I'm sure you could fit a muffler, probably not as simple as you imply. With a car, there's a whole structure and design for mounting and taking care of it. With a standard inboard, the motor is relatively fixed, so the muffler can be also. Much simpler just to put a straight pipe and not worry about it.

You could certainly use one on a displacement vessel but as stated, 200+ hp is overkill.

I'm not sure how rough but the gulf of Thailand and the Andaman sea are pretty big bodies of water.

On larger boats, I have seen them incorporate helms (typically the entire steering stalk from a toyota) and then with a lot of rebar welded together with pulleys, they can steer remotely.

[NevilleCat]

Originally Posted by boatman61

I've always felt these would be great for Wharrams...

There are something similar around, in that the engine is on the bridge deck and the shaft is on a uni joint and drops down or raises completely out as required.
In Australia Owen Easton had this concept in some of his Aluminium catamarans

[Celestialsailor]

Certainly a lot of opinions on this thread but I wonder how many have actually been in/on one. I have used these often during my trips to Thailand in the past. The ones I have been on seemed to be made of a darker hardwood, possibly teak. When they accelerate, they visibly twist A LOT! Many of them have a child aboard (5-8yrs of age) with a scoop to bail they constant water flowing in from the seams. To be honest they are more of a novelty for tourist. In smaller towns with less tourist, they are used for fishing.

[Franziska]

Originally Posted by black_sails

What do people here think about the type of propulsion used on thai longtail boats? It's used elsewhere in southeast asia too but seems to have a really strong following in thailand.




Personally I like them alot and I see many practical advantages. The aesthetics could be hit or miss/whether someone minds being different, but since it looks different i'm used to people probably thinking they'd rather not have one even if it saved tens of thousands of dollars. What would you think if something with a motor like that pulled next to you in the marina?



I'm not saying that it has to look JUST like this with the engine's naked rumpus hanging out in the wind, a person could make fiberglass or metal cowls or coverings just like outboards have, it could look downright swoopy, but this design would still have the proportions of the long prop shaft. I'm willing to overlook aesthetics to have performance, cost savings, and practical advantages though. First I just wondered what the general consensus was.

Just came across this. Scroll down the pictures. Subject is dinghy wheels, BUT, someone seems to have done what you have in mind:
https://www.beachmaster.com/boat-lau...stomers-photos

[IslandHopper]

And for those that want electric.....

https://www.youtube.com/watch?v=T3SfSZNx2os

https://www.youtube.com/watch?v=aJI8ncGYtMM

[valhalla360]

Originally Posted by Celestialsailor

Certainly a lot of opinions on this thread but I wonder how many have actually been in/on one. I have used these often during my trips to Thailand in the past. The ones I have been on seemed to be made of a darker hardwood, possibly teak. When they accelerate, they visibly twist A LOT! Many of them have a child aboard (5-8yrs of age) with a scoop to bail they constant water flowing in from the seams. To be honest they are more of a novelty for tourist. In smaller towns with less tourist, they are used for fishing.

Been on several over the last 3-4 months while in Thailand & Vietnam. Haven't seen any noticeable twisting, nor any with a small child-bilge pumps. They don't seem to leak any more than western wood boats once they have been in the water long enough for the wood to swell up and close the seams.

I'm sure if you are only in tourist areas, they may appear to be tourist novelties but we've seen them used commonly by locals for fishing and other utilitarian purposes.