Catamarans: better with an engine in each hull, or a retractable sail-drive?

[snowleopard]

One or more outboards mounted closer to midships is a better idea than right at the stern. There are various solutions to the problem including one which had the engines mounted at the back end of long pivoting pods with a tackle to lift them out of the water and adjust height according to conditions.

Even then I have seen people having trouble with cavitation. I had a tri with an outboard mounted through a slot in the side of the main hull about 10 ft forward of the stern. In a short chop she wouldn't make ground to windward at all. I once watched a Walker Wingsail in flat water inside a marina trying unsuccessfully to berth against a windward pontoon. It couldn't make any headway with twin wing-mounted outboards.

 

[bigwow]

Not a problem!

May not be a problem in the multihull centre of the universe, but up here in North Wales it's a different story. And I've just repaired the scars of the last try.:encouragement:

 

[snowleopard]

May not be a problem in the multihull centre of the universe, but up here in North Wales it's a different story. And I've just repaired the scars of the last try.:encouragement:

I finished building mine at Northney Marina where multis are rare. The problem was solved by using a Mobo trolley with similar hydraulics.

 

[catalac08]

4Henry... Not a good idea at all. In big seas the engines would probably be getting swamped one second and then the props out the water the next. There are very good reasons why 99% of cats have twin inboard diesels.

99% of cats have twin diesel engines- that may be true for bigger cats but in the smaller 8-9m range the figure is more like 50% with twin diesels, 25% with single diesel and a leg and 25% outboard engined.

 

[snowleopard]

99% of cats have twin diesel engines- that may be true for bigger cats but in the smaller 8-9m range the figure is more like 50% with twin diesels, 25% with single diesel and a leg and 25% outboard engined.

And among the racing fraternity I'd guess 80% outboards.

 

[4Henry]

Thanks to everyone who responded to my query re: HT with twin outboards off stern.
Very helpful to receive this knowledgeable input.

A particular reason for asking this question at the moment- just looked at an HT for sale.
She must be the MK IV, as she does have a crawl space- the owner didn't know the mark but said she was built 1985.

She sported twin 9.9 Yamahas low mounted off stern with heavy beefed brackets. Given this setup, I did baulk at weight issue, leveraged off stern- though owner says he's been in breaking 8 footer conditions [most he's experienced, coastal Florida], both running and powering into- and said no problems, no poop, no cavitation [mounted low], stern rose without problem in 8' seas....
But, of course, owners can sometimes be unaware of aspects of their own well-loved boat, especially when selling her. So the answers received here are most welcome.

I confess, as one gentleman pointed out, I do baulk at cost in repair, weight and accessories related to not one but two diesels- not quite as much as baulk at idea that engine may be subject to pooped when engines are needed most.

Without personal experience with the HT breed, I must bow to majority wisdom of those here who do have experience- twin outboards not a god idea.

[Twin SOMETHING seems requisite for maneuvering- be it outboards, diesels, hydraulic drives.]

THANKS TO ALL!
Great Reading.

 

[catalac08]

Whilst twin diesels will clealy be best for manoevering many get by on small cats with a single fixed outboard engine. I have had a single fixed outboard engine on an 8m cat for 12 years/10K nm and I get by mostly without problems berthing etc. Occassionally when I can see that something will be particularly difficult I will find an alternative and chicken (good judgement?) out. Yes from time to time the motor will buzz a little when it is very rough and it gets near the surface but it has a rev limiter so no problem. I have never picked up a line with the outboard but it should be easy to clear and I can always put a "get you home" small or tender outboard on a bracket if necessary.
I think at the bottom end of the market I would be much more interested in a cat with an outboard that could be replaced for a few £k than one with a pair of aging diesels with all of the expensive and time consuming problems inherent in them.

 

[Seajet]

4Henry,

I've said what I think about cat's, outboards and diesels etc - maybe on a HT in not too confined berths a central outboard might be best bet afterall, especially if you could steer it for vectored thrust ( which would still have a slow / minimal effect I fear ), but I hope you've seen all the nonsense about ' importing ' boats to Europe, VAT etc, a 1985 boat should be fine, but I can imagine long chats with jobsworths if that's what you're planning; or will she stay in the uncivilised New World ?

 

[4Henry]

Thanks again, all.

Please accept my apology for so long to respond.
I still haven't figured how to "subscribe" to a thread so to be alerted to new posts; when I do want to check in, I get lost trying to return to the thread in which was conversing.

Computers and I have an understanding: I do things the hard way and they won't tax my low frustration threshold.

SeaJet:
No, not thinking about bringing a boat back to civilized world. Going the other way. My plan is neither to sail a boat to civilization in Europe nor to remain in gladiator-training of the lower 48 states.

My home of last 45years is an island 1,200 mile north of Seattle. But... what with being an island, need a boat. What with being old[er] and no longer given to open boats or sitting in cold or working on old wood commercial boats; what with liking to have a get-home rig [if fuel was cheap and if I could find a part for every engine problem, why on earth would I want to wrap my frozen fingers round a halyard instead of a throttle?]; I am looking for a next -and most likely last- "sailboat"- in quotes cause a motor sailor in cat guise might be more accurate.

Cats, accommodatons for length [cold and dark, spend time below], shallow draft [river flats only place to duck in], easily single-handed rig- seem a workable compromise. Specifically, Catillac and HT's: old, slow, plodders, that will still get you home if you do something stupid [which i've been known to do, even when i was less old and slow myself].

Drawbacks [in my view] to cats are limited carrying capacity; slamming and hobby-horsing; and, finally, the controversy that is the subject of this thread-

what is "best" [is there such a thing?] configuration for what is essentially, in my view, a motor-sailor?
I don't spend much time in and out of strange marinas. And anyone on the dock would assume that soon enough if they are watching the way any boat I'm steering "maneuvers". "That boy has not practised much, has he?" he/she would think.
And I've never even owned a cat yet!

So questions, please:
-Am i correct in what have listed above about advantages/disadvantages of the older plodder cats?
-And are twin outboards really so great a sin?
Catillacs [the 9m, intrigues] seem to do with one outboard off the stern.
-Bow thrusters?

I'm floundering in the decision.
My straits and sounds, with fast tide current and channeled winds, can get as nasty as any waters, i guess [though haven't been to all waters, or even many waters]. And seas over bar can be dizzying-steep. Plunging down into black depths, hoping bow will rise again is to be avoided
- but will the cat keep me alive?
- Even with an outboard [or 2] astern?

Some experienced hands have weighed in here, but still... these are blue water men of wide range.
I'm in sight of land most of the time [not necessarily a blessing if the land of which one is in sight is nothing but rocks].

I can usually choose my weather. Though, what with being stupid, sometimes the weather chooses me. And then I'm slowed down. And so I don't make cover before tide turn- and then there you might be?
-Hoping your decision to use twin outboards wasn't as stupid as others have suggested.

As always, any feedback or comments or suggestions- all welcome.
Thanks to all who have taken time to write- every comment is valuable.

 

[Mudisox]

I have an older "plodder" cat although have owned and sailed a variety of other multihulls. It has two small diesel engines and am currently renovating both. Two is infinitely better than one in any configuration. Servicing and work on one is easier if you have another to refer to or rely on to get you home/ or for economics. Ditched the Brunton props after 2 seasons, so I "drag" fixed ones which give not only excellent manoeuvrability as already observed but also cheaper, more easily maintained propulsion.
Diesels also provide much better electrical input than an outboard, with a safer, more easily obtained fuel. Normally I still get around 6kts on passage, and this is not really trying.
Do I get change from my 6d with this 3ps worth?

 

[snowleopard]

My experience of outboards on offshore boats is that in choppy conditions they can cavitate and you can't make to windward. Some owners claim it isn't a problem so I guess it's down to the design of the boat. You need to check with other owners (and beware the 'my boat is perfect, criticise my wife if you like but never my boat'). You can be certain you'll continue to get propulsion with inboards.

Yes, hobby horsing is a problem with short boats. It's particularly bad with boats that have a canoe form, i.e. same shape at bow and stern, the HT is one such. For weight carrying, if you want performance, drill holes in your toothbrush but cats will carry a lot of weight, they'll just become slower. I have a friend with a HT that is habitually loaded way below its marks. It goes slowly but gets there and he lives in some style.

 

[4Henry]

Thanks for responses,
replying to Mudisox and SnowLeopard:

Mudisox:
thanks. Yes, two engines better than one regardless of type engine, seems requisite on any double hulled craft. Also good reminder about electrical input from diesels- a notable consideration. [Unfortunately, I am not familiar enough with 6d and 3pence to be able to offer change at this time]
Also noted, your mention of fixed props. Thanks.

Snow Leopard:
That I did not realize. I had been under illusion that over-weighting a small cat, such as with twin outboards hanging from stern, would put her in danger in seas. If I read your response correctly, not so much will she be in more danger, as she will just go slower. Forfeiting a knot [say, 20% slower if cruising speed averages 5k] for the "luxuries" afforded by accommodations on cat is, for myself, a reasonable trade.
A paraphrase of the old expression "a gentleman never sails to windward" might be inserted here, but I'll refrain for fear of changing topic of this thread and subjecting myself to deserved condemnation.

Also thanks for mention that canoe stern small cat [eg, Heavenly Twins] more subject to hobby horse than, say, Catalac cat.

Comments on this thread both thoughtful and helpful- and indeed, I have changed focus from HT with twin outboards to Caddy 9 or 10 [10 may be out of price target, but the 8 and 9 are all cockpit- which, in cold climate, unless tightly tented, is just so much wasted space].
The determinant will be finding one or the other on the continent's west coast-
preferably cheap, in "perfect" condition, well-equipped, new engines and nearby. And cheap.
[Odds of a boat meeting all those criteria boat showing up?

 

[Spice Cat]

Just to add my ha'penny worth.
Choice of propulsion method depends on your sailing activities, size of boat and sailing area. I mainly sail in the Thames estuary area and have a a single outboard on my Comanche and would have it no other way. I do a lot of Club racing and the other club multis also all have single outboards.
Last summer I went to an Iroquois rally and the majority there had single outboards.
I did think of getting two 9.9 yamahas when I changed my outboard last year but Yamaha do not now sell the high thust version so bought a single 25.
Wonder if more of us that race will start considering inboards now that handicaps are performance based, which means that you can still do well even if you are slower?

 

[Seajet]

A retractable engine drive on each hull sounds wonderul, if a tad expensivel...

However I wouldn't trust the guages until I was well used to it...

Calibration is the answer to a great many problems !

 

[Rum_Pirate]

Many of the cats (LOA 40'0" plus) here have a central 'sled', fixed on the transom, which can be raised (completely out of water) and lowered.

An outboard engine is bolted on to the 'sled'.

The outboard engine can also be raised lowered.

The outboard engine can also be steered.

No drag when sailing. No snagging pot markers etc etc.

 

[snowleopard]

My abiding memory of single-outboard propulsion was trying to enter Cowes in a fresh southerly. I was singlehanded in a 40 foot tri so tacking through moorings, ferries etc was out of the question. As I tried to motor in with my 20hp outboard I came to a complete standstill with the engine screaming as it cavitated at every short wave. That was it for me and Snow Leopard had to have inboards whatever the cost.

 

[Spice Cat]

Ventilation/Cavitation is an issue for outboards on large multis in short seas. IMHO OB shaft needs to be at least xlong, xxlong better.
Trying an anti-ventilation plate next year. Use high thrust for better grip and reverse. In my area I think I would go inboard if length > 11M. (Cats)

 

[brian eiland]

Hi,

We have a Gemini 105Mc.... single engine, Selette leg, lifts up.... I believe there are more Gems made than any other Cat at over 1000... mine is #763

maybe not the best made boat in the world, but I have to say imho as a coastal cruising cat, they are hard to beat.... we get about 7kts under power

Steerable, Lifting leg, lifting centerboards, good sail plan, I think they sail very well for a 35fter... also a queen size double, very comfy

It would be great to have two engines, but they would take up a lot of room under the bunks, as well as the issue of twice the servicing costs, extra wait... and lets be honest, there are quite a few yachts that seem to manage quite well with a single lump

If you get a chance, maybe you could add one to your list to look at?

Stu

Hi Stu,
Just joined this forum, and came about it as a result of researching some newest info in consideration of a single engine installation on cats under 35-40 feet. I have some new ideas I want to consider for this size boat, for as you say twins can be space consuming.

BTW I was in the multihull business big time based out of Annapolis MD, .....Tony Smith's head quarters as well. I knew him and his wife very well. We where known as Chesapeake Catamarans at that time 1979 -1991.

Brian
Running Tide Yachts

 

[langstonelayabout]

I was looking at two old Prouts for sale

Sorry, wrong thread. I thought you said two old trouts. I thought for a moment that my two ex-wives were up for sale... Lol

 

[brian eiland]

Hi Stu,
Just joined this forum, and came about it as a result of researching some newest info in consideration of a single engine installation on cats under 35-40 feet. I have some new ideas I want to consider for this size boat, for as you say twins can be space consuming.

Email letter I just sent to FisherPanda, Oceanvolt, Vetus

Electric Motor Propulsion for 40 foot sailing catamaran

Dear Sirs,
I am working on a design for a 35-40 foot catamaran that I term a picnic/weekender catamaran. The concept will be somewhat similar to this one I found in Thailand a few years ago. I posted it on several boating forums a few years ago.
[url]http://www.yachtforums.com/threads/weekender-picnic-powercat.13966/#post-173670[/URL]









This particular catamaran was a powercat. I will be adding a sailing rig to it. I will also adding a trolling/fishing chair area to rear deck area,... so that pictured Zodiac dinghy will be relocated, and the two outboard engines need to be eliminated.

I need to repower this cat design, both for close quarters docking situations, and for some motor/sailing situations.
I have had a very long time interest in the rim-drive propulsion concept.
[url]http://www.yachtforums.com/threads/rim-driven-propellers.3961/[/URL]

What I have in mind at this moment is how I might adapt this Vetus Rim Drive unit to be my single primary propulsion propeller. I would like to mount it in the aft portion of a of the wingdeck of the vessel, and make it steerable upon demand, and also retractable when sailing. Naturally it requires an electrical supply, which as I understand it under present technology can come from a combination of battery power and a relatively small DE power plant. This power plant would be located in its own insulated (heat and sound) box up on the flat deck of the catamaran.

So here are a list of questions I have at the moment:
1) Can such a rim-drive propulsor be run continuous without overheating? It is my understanding that the Vetus unit can do that now.
2) Whether it is the Vetus rim-drive, or another electric drive motor, is it possible to operate such a 'DE system' with very little battery supplements?
3) How few batteries are required (in the interest to keep added weight down) ?
4) Is it possible to 'direct drive' this 'electric prop' with the DE power plant, or are batteries required.
5) I realize Vetus has its own DE power plant, but it appears that FisherPanda has an even greater selection of small DE power plants. Can these systems be mixed?
7) Should the Vetus rimdrive prove not powerful enough, what are the other alternatives that anyone would suggest??

As an example of why I might be considering this approach, I will offer this personal experience of mine. I was the original importer to the USA of French catamaran line,... the original model was a 37 foot boat called the Louisiane 37. I placed a 9,9 hp Yamaha 4 stroke Hi-Thrust outboard engine on it. It was a limited production outboard they made with an extra gear reduction in the output prop shaft so it could turn a bigger propeller. It worked pretty good as we got 7 knots out of the vessel in calm conditions. The engine was mounted in the center on a rear beam of the vessel, and soft lines were lead from the engine to the rudder arms so when docking the engine would steer along with the rudders. Maneuverability was VERY good. It made me a believer in 'steerable engine', verses twins,...an alternative to consider.



Brian Eiland
RunningTideYachts.com