Retractable Marine Drives

Any loss of drive efficiency in terms of dollars per mile for fuel might easily be made up by the advantages of having a hyd system on board.

No white smoke from an anchor windlass, EZ cruise generator underway , EZ powering heavy loads like water maker , scuba air ,refrigeration, and deck winches for sail handling .

The total cost of operation and repairs might be lower over the years of traveling, especial;ly as fuel should stay cheap for a long time.

 

Just a quick observation about the use of such a pump on a sailboat (or even a larger powerboat).

I was in the retail marine business in Annapolis MD when the 40' Condor Trimarans were being built right next door. They experimented with a 'jet drive' propulsion unit on one of their vessels in lieu of the outboards. Their conclusion,...it made docking very haphazard as the jet pump had no 'grip' on the water, and thus the boat was very 'skiddish' in close maneuvering.

 

Below is a comment on the Condor 40 with a jet drive engine. Noise appears to be an issue. I have a hard time believing that a jet would only push a light cat at 3 - 4 knots without some serious issues in the installation or a mismatched jet for the application.

A jet for say a seadoo would not be the correct application as they are a high speed pump.

{I've heard the first Condor 40 had a jet-drive engine?
Yes. It was called the "Wolfpack Jet Engine." It was the brainchild of an engineer from the Midwest, but had never been tried out in a boat of any kind. Unfortunately, it was a case of "great on the drawing board, lousy in practice." The engine was reportedly louder than an AC/DC concert and a 747 at take-off -- COMBINED. And it would only push the Condor at 3-4 knots max. So, the jet-drive was yanked out, and Yamaha 9.9 outboard(s) were installed on the aft crossbeams.}



Jets have been used in 300 foot fast ferries for years and in many commercial and military forces as well.

 

Wärtsilä launches retractable thruster
not exactly sized for our yachts, but the concept is expanding

 

lots of racing yachts have retractable drives, big Stainless CV with seals and long folding deadwood so when its up its all flush.
Certainly takes up some room inside but prop out of the water when moored
Certainly not as efficient as straight shaft as they are usually on steeper angle.

 

Yes I had a number of photos, dwgs of such, but I can't remember where I put them...

 

Awhile back I was on a delivery after a Cabo race and was holed up waiting for weather in San Juanico. One of the boats there was a Maxi that had a diesel MercCruiser I/O that could be lowered for powering and raised up into the hull when under sail. I think the boat was the Max80 (I could be wrong on that) and it was built by Dencho Marine. I have no details on how it worked.

 

Nothing new with these ideas?

 

Dear Steyr marine,.
.......
I have returned to this idea of designing such a boat, and document some of this restart here on that old subject thread. One important aspect that might very well affect this design, is how will it be powered,...twins, singles, outboard, inboard, etc.
Weekender/Picnic Power and Sailing Cat
Weekender/Picnic PowerCat https://www.boatdesign.net/threads/weekender-picnic-powercat.33751/

Single Engines vs Twins
Weekender/Picnic PowerCat https://www.boatdesign.net/threads/weekender-picnic-powercat.33751/page-4#post-873086
Weekender/Picnic PowerCat https://www.boatdesign.net/threads/weekender-picnic-powercat.33751/page-4#post-873087


I am a fan of a 'steerable single engine'.
I believe the 'powerhead' of that single engine could be located up on the deckhouse floor, and some sort of strut arrangement transferring the power to the prop,...perhaps something like this,
Weekender/Picnic PowerCat https://www.boatdesign.net/threads/weekender-picnic-powercat.33751/page-4#post-873103
Goetz's Red Foiling Catamaran https://www.boatdesign.net/threads/goetzs-red-foiling-catamaran.63645/

I believe your new common rail 4cyl engine could be made to be the 'powerhead'? Its light weight, its got enough power (70-160 hp), and it could possible be made to operate in a variety of attitudes/angles if necessary. I'm trying to imagine how it might be linked up with long vertical out-drive-leg connected to an existing duo-prop propeller lower unit??

Would you have any ideas, and/or examples of anyone having tried such a idea??
got enough power (70-160 hp), and it could possible be made to operate in a variety of attitudes/angles if necessary. I'm trying to imagine how it might be linked up with long vertical out-drive-leg connected to an existing duo-prop propeller lower unit.

Would you have any ideas, and/or examples of anyone having tried such a idea??

 

Abel Tasman Sea Shuttle working in the Abel Tasman National Park uses belt drives on some of their larger aluminum catamaran passenger ferries.
Basically they take passengers around the coastline of the park and drop them off on SHALLOW sandy beaches by beaching the boat.

Their problem was to be able to get their ferries close enough to shore to allow the passenger to disembark but not have the propellers digging up the sand.

They designed a belt drive system to be able to lift the props partially out of the water for shallow water operation.

Actually they designed and built two different types of drives, As this was several years ago there is a chance that some of what I put into this comment might pertain to one or the other type of drive as to length of boat etc but will get this information into the thread as to the viability of a belt drive system.

I rode on both of these taxis, one out and one back several years ago

Belt drive
25 meter aluminum catamaran, 150 passenger, twin Scania 485kw/600 hp diesels
The motors were above the prop shafts in an engine compartment that hinges just ahead of the front of the engines. When coming to shore the engine compartments were pivoted UP by hydraulic rams lifting the props partially out of the water.Ie the motor and props lifted up

I spoke to the captain about this unique drive and he put in a dvd on the in cabin screen that showed the entire build process of the boat and drive system.

Again from memory, I would expect that the ferry cruised at maybe 20 knots and the captain said that they had several thousands of hours on a set of Kevlar belts

Side pivot taxi
Not sure on the size of this boat ( maybe 15 meters) the engines were fixed but their outdrives which were designed by the owners, actually pivoted around the axis of the input shaft to lift the props clear of the water.

The above I had written back in 2015 on a different post regarding belt drives. If the outdrive leg, similar to a stern drive, could be rotated 180 degrees, the drag would be minimized.

 

I seem to recall your mentioning this previously as well,...and I think you were going to see if we could get a copy of that DVD. Don't think we ever did that??

 

I had sent them a couple of emails but no response, this was a long time ago

 

unique marine drive abel tasman new zealand aqua shuttle taxi - Google Search!

ok this is the site for the Abel Tasman Shuttle and in one of the pictures, there is a boat that shows the drives

 

I recall seeing a patent from around 1915 with retractable drives very similar to that.