Twin Prop - Single Engine

[valter.f]

Hello friends,

Do you have information on this system? Is it functional?...

According to the manufacturer, the main advantage is the fuel economy with small improvement in speed, but it would be fantastic to propel two catamaran hulls
with a only central diesel engine or even to distribute the power engine in monohulls of large transom.... Is there something like in the market?...

http://www.mastry.com/page.asp?p_key=8AEE52E40AC14966A362CACFD957550F

Thanks,
Valter.

 

[Mr Efficiency]

I suppose it depends on what losses you accumulate down the drive train(s). It could also become a problem if you damage one propellor, I suppose. The VTOL Osprey aircraft has the two props connected, I understand, so that an engine failure won't doom the thing, which of course is a slightly different situation to this boat set-up, but a hell of a lot more complex engineering wise, I imagine.

 

[kapnD]

Cool concept, widely used in heavy equipment applications.
Dorado Boats in Tampa area built some very interesting craft using this system, even double-double outdrives!
Apparently they didnt hit the market well, havent heard anything about them in a long time.
If you look at realistic drag calcs, it is obvious that there is no efficiency gain to be obtained by using two props instead of one.
Shallow draft and docking maneuverability are the advantages I see.
Catamaran application would require the use of even more angled driveshaft joints, another horsepower killer, as well as putting the powerplant high and in the middle of the deck.
How about a trimaran with the perpendicular shafts enclosed in foils?

 

[valter.f]

Hi,

I think both of is correct in their placements.

It's strange how something that seems so common always be as complex as the gears, reducers and his functioning in engines.

I do not like trimarans and I'm thinking of building an open-deck catamaran, but if I can keep the central hull just for commands and engine,
can be a good idea. I need to examine friction and the cost of another hull. At the end, the installation a second engine can be more economical.

Regarding the use of only one engine, I doubt if the idea of Aspen (2 hulls 1 engine) does not really affect the navigation or the boat structure. What do yours think?

Thanks,
Valter.

 

[rubenova]

Look at http://www.philbrooks.com/Yard-Services/Geared-Up-Systems. Also search this forum " single engine twin screw "

 

[kapnD]

I think the Aspen design is a "laboratory rat".
Might be feasible to design the hulls to offset the off-center propulsion, but would go to hell quickly in anything but flat calm water, not to mention the problem of docking the beast.
A quirky hull design like that will likely be speed specific as well, performing poorly at above or below design target speed.
As for your catamaran, I dont see how it will not be at least somewhat of a trimaran with the motor mounted in the center of the deck, and require an engine room pod hanging down to keep the weight low and the driveshafts in line with the final drives.
Maybe someday they will develop bluetooth drives that require no mechanical connections!

 

[WestVanHan]

I think the Aspen design is a "laboratory rat".
Might be feasible to design the hulls to offset the off-center propulsion, but would go to hell quickly in anything but flat calm water, not to mention the problem of docking the beast.
!

I suspect you haven't spent much time in the area Kapn....


"The wind built as they rounded Cape Scott and into the open Pacific Ocean, at the northwest corner of Vancouver Island. While it was nothing like the previous evening’s 60-knot (100+ kmph) winds, as the team worked their way south around the Brooks Peninsula the wind built to 35+ knots.

The sea state on this section of the north coast included a ground swell of five to eight feet rolling in from a storm in the Gulf of Alaska, combined with a southwest swell of two to three feet, as well as a brisk south-southeast wind chop of three to five feet flowing right up the island’s coast line.

“It was something to see, the seas were so confused they simply imploded on each other creating vertical curling spouts five-feet high,” said Graf. “This was something I’ve never seen in 30 years of boating in three oceans, and our course took us straight into them.”"

http://www.pacificyachting.com/aspe...mplete-pacific-yachting___s-pacific-challenge

 

[Mr Efficiency]

You can run a single diesel in a power cat without dual drives, or asymmetrical hulls. It was done in the "Shark Cat" line of planing cats from 7 metres up, using Volvo sterndrives fitted with a special extended (deep) drive leg, some Duoprop as well. The idea was fuel savings, and keeping the prop in clean water necessitated the modified leg. The downside was a sluggish boat compared to twin outboard power, but it works. Boats are now sold as "Noosa Cat".

 

[kapnD]

Van Halen,
I did not say that it couldn't be done, mankind has pulled off some radical stunts in some pretty unsophisticated equipment, just that the idea does not look to be optimal in terms of practical engineering.
The OP did not leave a link for the Aspen idea, I just based my comments on the descriptive drawing provided above. Thanks for the link, those guys must have had some serious white knuckles on that voyage!
I am totally foreign to the Vancouver Island area, but have spent countless hours in very nasty open ocean waters, and have developed some distinct preferences as to what is safe and comfortable for me in those conditions.
A boat that "knows it's head", and can easily hold its course in bad conditions will get my vote over one that is obviously going to be tender in some points of sail.

 

[valter.f]

Hi Rube,
This system seems more effective than the former. In the side gear also has the reducers. Unfortunately the stringers for use in catamarans are also not mentioned.
Tks.,
Valter

 

[valter.f]

West,

I have two passions: Catamarans and Lobster boats. It's amazing how the C100 has plenty of both. Unlike many companies, Aspen has the courage to maintain a catamaran with small beam when others come to your maximum in most projects.
As a prize, their boats are exclusively longilineal and elegant. It is also easy to see the quality of the productos used in all models, including the L90 launch.

I did not know the Pacific Yachting and for me it is new. What is not new, it is know that a catamaran achieved this feat. Monohulls are a passion, a culture difficult to change, but I think any experienced sailor knows the infinite advantages of a
catamaran, especially a sailing.

The C100 has the right measure for a challenge like this. First it is a catamaran with all its majesty and stability of two hulls. Due to its narrow beam, manages to be even lighter and faster than their peers. 32 foot, is the optimal length for seas
as he faced, keeping a good average speed, leading crews, equipment and incredible 1,000 liters of fuel to meet your single Volvo Penta.

It is impossible to say that this boat has not undergone a major test and the use of a single engine is not functional, but I agree with our friend KAPND, when he says that Aspen been doing an experiment.

I do not know if the pilots felt the torsion while sailing, but we know it exists. What is not known is whether this torsion will cause structural problems or other in future, since it is impossible to simulate a test with "all its variables" like waves,
random shocks along with the torsion, heat, cold, unstable spinning propellers followed up by kicks and hundreds more . I think sincerely that only time can answer this question.

Valter.

 

[valter.f]

Mr Efficiency,

You could indicate a link. I did not find much about the subject.

Thanks buddy,
Valter.

 

[Mr Efficiency]

http://www.boatlocator.com.au/item/94-sold/AU/1-victoria/15167
http://www.boatsonline.com.au/boats-for-sale/used/trailer-boats/sharkcat-2600/125540

Some pix in those, hope the links work. The drive legs were specially made by/for Volvo to get the prop deeper, without excessive appendage drag. Not sure what kind of cat you are interested in, these are reasonably small planing boats.

 

[valter.f]

I have a 35 ft hull custom design by Paul Fisher to construct a skiff cat twin vee. I had looked at the boats of Livingston using an outboard motor protected by a appendage and I figured that could build this deeper appendage and install there axle
and propeller of a diesel engine I already have, but now looking to this system with sterndrive, I see a better idea. Can I use my engine, reduce friction with a lower appendage and have the great benefit of berth in beach.

Thanks Mr.

 

[Moneymakerspy]

I would think the value in a single engine/dual drives would be largely in the ability to run the drives in opposite directions, or for each drive to shift gears F/R independently.

Having the maneuverability of twin screws in a single engine vessel would be something of value I would think.

There may also be something to be gained in the size of the drives/props for shallow water applications (someone else mentioned shallow water - was this why) as you may be able to have smaller drives and props.

I like the comparison to heavy equipment, why is this not considered an efficient concept once it gets wet? Aside from the Dorado Boat Co. experiment, are there any other examples of single engine multi-drives?