Longtail Evolution

No multi-cored flexible shaft is involved.

Here's a way I developed and have been using to handle and get me home from very shallow water for decades, which works better than any conventional short/ long tails for my applications. But of course it may not work for everyone! Video clip at post 53 and 54,

Prop Shaft Systems. https://www.boatdesign.net/threads/prop-shaft-systems.24636/page-4#post-286133

The "guest" written explanation commentary is from Rick Willoughby, a mechanical engineer and former member of this list. It took me a couple of years to convince Rick that what I was already using, actually worked, ha! He later used the concept to build a boat which set a new human powered boat speed record many years ago, which still stands, AFAIK..

Ps. The Prop in the videos above is from my Thai longtail, and it works the best of all that I have tried for shallow water, it seems to find openings between and around protruding rocks and other debris. But it is not as efficient as a correctly selected and tested model RC prop, matched by trial and error to each of my particular boats.

 

I thought you were referring to the Mud Skipper "Twister" in your post based on the link you used. It has a flexible inner shaft. I see now that it is something completely different.

 

A good explanation of how a properly trimmed longtail works and how shaft length is so important.

 

Gawd, I've heard that before!

 

Here's an interesting short tail that can run in reverse,

Pro-Drive Outboards Full Power Reverse motors https://prodriveoutboards.com/outboard-motors/full-power-reverse-shallow-water-boat/

Something like that might be useful, in shallow waters where getting stuck is an issue.

 

Getting stuck is only an issue if you run a big heavy rig. That's the beauty of these boats.
The import Thai longtail is the clear winner here. To design a drive that the surface piercing prop runs in the crest of the wake behind the boat and which is higher then the bottom of the boat is pure genius. Not to mention the cost. You can get into this type of rig for half the cost of the alternative and it's a true surface drive. This of course is purely my opinion.

 

Curious to know if a long tail prop can somehow be automatically set to run in the crest of the wake without a constantly adjusting a tiller? As a senior citizen, I haven't found a Speedy boat tiller system that has the comfort and ergonomics which allows for me to have a relaxing day on the water. I like to have a comfortable seat and back with large, close by downward water views facing forward, especially when traveling at speed in very shallow water.. Guess I'm just persnickety, and not as physically flexible anymore, it comes with age, ha!

 

You definitely have to drive a longtail. The gimbal takes some getting used to. That's what I like about my surface drive. Even though it's gimballed, the extension spring and trim adjuster take care of the up and down. That and a little left rudder on the skeg to cancel out the tiller torque it's like operating a regular outboard.

 

No.

 

That's an average of about 3.5 miles per hour not taking into account whatever the river flow rate happens to be? There's got to be a better/ faster way to do it on the water, JMHO? Maybe there's just something I'm missing, (allowance for night time, portaging, resting, Etc)?

Ps. Myself also currently holds first and last (undocumented) speed records for a battery powered motorized vessel going both up and downstream in at least a dozen River sections on several different rivers in the USA and PR. But it might be because almost all other powered or unpowered water vessels- can't get there, ha!

 

Cool! Your hobby, commercial product, or both?

 

Well, they had to eat and sleep everyday. My first guess would have been a jet boat but for some reason that hasn't been done. Rugged country. I can only speculate about portages etc. As far as your following posts question, it's my hobby (unless someone wants to order a bolt on kit). I made my living fabricating and installing craft breweries. This one's my fifth boat.

 

The commentary sucks but the footage is great!

 

Actually, yes!......
A propeller approaching the surface will generate a thrust vector directed slightly upwards (and often to the side as well), unless specifically designed for a downforce. Maximum vertical composant occurs at about 50% submergence, depending on blade design. This was "discovered" in the racing community and led to the evolution of the "propriders". Here the vertical force is strong enough to balance the hull, which consequently is supported by three points; the two sponsons and the prop.