Single or Twin engines

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Re: False Sense of Redundancy

Err not received wisdom but observation, I suppose you could call it received but it was received from a volvo service centre guys who told me that they have more issues with twin boats than singles and the problems are invariably not solely mechanical linked to one of two engines.

Since when has your experience been the 'standard' I think your experience proves that you get more trouble with a twin set up than a single. This is true in aviation also.

No with a twin you have to compare statistically the chances of one engine failur and two if you want to compare a problem vs no problem statistic. The twin will never win this argument. I have been boating with a well maintained single for 5 years never missed a beat, that is my received wisdow, but boy i;ve seen a lot of boats with twins limping as you would say.

Most twin set ups these days use EDC controls, these are integrated units with a single circuit board, if that fails you loose both engines throttle controls fact.
I fyou have a fuel contamination then its a bit late switch the valve off once both engines have stopped to isolate the tanks!!!!

Sterring, throttles (EDCs), fuel, electrics all shared these days so you are kidding yourself on a modernish boat if you think your invulnerable. FACT ( I am beginning to sound like Gludy) /forums/images/graemlins/smile.gif
 
Re: False Sense of Redundancy

Maybe I have'nt explained myself very well. I entirely accept that one of the engines in a twin set-up is more likely to fail than a single engine but this is'nt the issue. Surely the issue here is not which system gives more problems per se but which system is least likely to leave you stranded without power and there's no way a single engine is going to fail less often than BOTH engines at the same time in a twin set-up. Its a bit like saying a single engine aircraft is safer than a twin or a twin is safer than a four and, yes, I know multiple levels of redundancy are built into aircraft systems
Partially agree with you on EDC but its not good practice to leave the cross over valve open anyway for reasons of cross contamination
Nobody's kidding themselves that they're invulnerable with twins, its just they're inherently safer
 
Re: False Sense of Redundancy

Nope, running out of fuel was my crass stupidity, failed engine mountings was my fault for not inspecting them regularly and failed drive belt was as a result of a relatively new alternator failing
My point was first that these are not fuel related and second that they equally would have happened with a single engine. With a twin set-up, you get home, with a single you call the RNLI
 
Re: False Sense of Redundancy

You couldn't put a new drive belt on at sea? Certainly you may chose not to on a twin of course - but is it necessarily and RNLI/Seastart job?

Rick
 
Re: False Sense of Redundancy

Actually, there's plenty of evidence that modern single engined aircraft are statistically just as safe as twins. It's a bit different in that a twin-engined aircraft in assymetric flight can be very difficult to control (and certainly to land) and there are countless examples of 'plane crashes where the pilot lost control due to this difficulty. I believe the CAA are currently considering allowing single engine commercial operations - a practice that is carried out in most other western countries (and Oz, I think) - due to the extremely high safety record of single turboprop aircraft.

I think everyone's a little paranoid on here. I agree that safety is the most important thing to consider when boating but if everyone who flies aircraft thought that an aircraft with a single engine was "dangerous" then general aviation would die! And believe me, I'd rather be on a broken single-engined boat than a broken single-engined 'plane!

tinstaafl
 
Seems to me that there is a good and bad side to both setups. I think either is ok you just have to change your way of thinking depending on which setup you have. The thing that worries me with twins is that if you foul a rope across both props and the rope then goes tight I imagine you could cause a lot of damage. But with a single you may have to get a tow but your shaft and prop will live to fight another day.
 
Also, can I just add that a mate of mine had a single engine for 32 years and no major problems. He bought a boat about a year ago with twins and has had nothing but trouble with one engine or another. And if the engines worked then one or other of his outdrives played up.
He now is not as convinced as he was before about the reliabilty.
 
Re: False Sense of Redundancy

You certainly can. I lost one while coming back from visiting Haydn and LongJohn at Salcombe as I came past the Needles some years back. Only breakdown I've ever had at sea, and got it sorted before Seastart turned up...Seastart insisted on turning up anyway
 
Re: False Sense of Redundancy

No, not on this particular boat. The front end of the engine was tight up against a forward bulkhead and the engineer who eventually changed had to lie on the other engine to do the job - not advisable to do when hot and certainly not when the boat is wallowing around at sea
In any case it didnt matter because we had the other engine to get us back
 
Re: False Sense of Redundancy

The CAA may allow it but its not because single engined planes are inherently safer than twins, its because engines have become more reliable
Next, we'll be arguing about whether its better to walk on one leg rather than two!
 
Re: False Sense of Redundancy

My point was that I don't belive you can extrapolate the difficulty in changing a belt on a specific twin installation to mean that a belt failure on a single engined boat results in an RNLI call out.

Rick
 
Re: False Sense of Redundancy

Well, it IS safer to walk on one leg rather than two. For instance, you are only half as likely to stand on a nail sticking out of a plank of wood...

And so on /forums/images/graemlins/wink.gif

tinstaafl
 
Personally I'd always go for two, a simple rope round a prop can have dire results if your caught out in a nasty slop. Can still happen with two but a heck of alot less likely. I knew a RNLI cox who said that most call outs to boats in trouble (pleasure) were to petrol powered boats, singles with either rope round the prop or jammed/damaged rudder, fuel starvation/contamination or lost in fog/bad weather. If you had twin desiels you could eliminate two of the above which is a 50 % better chance of coming home un-aided.
 
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