The Great Debate

[MYTraveler]

If we own a single, we say single. Twins...twins. The circle is complete.

The more interesting question is what is the answer of the guy who has not yet bought.

 

[rslifkin]

I thought the debate had been resolved and the winner being a single with a capable get-home and thrusters.

Such set up will have the redundancy and maneuverability of twins and the prop protection of a single. Although many twins have keels that hang lower than their props.

No, no, no. The ideal is a twin, but either diesel-electric or diesel-hydraulic drive and with protected props (either skegs or just a keel deeper than the props). That would give the best of all worlds, in that you don't lose any maneuverability with an engine shut down, you just lose half of your power.

 

[Open-d]

No, no, no. The ideal is a twin, but either diesel-electric or diesel-hydraulic drive and with protected props (either skegs or just a keel deeper than the props). That would give the best of all worlds, in that you don't lose any maneuverability with an engine shut down, you just lose half of your power.

How much loss of efficiency do you experience in such a situation?

 

[rslifkin]

How much loss of efficiency do you experience in such a situation?

Good question. That would depend on how efficient you could make the drive system compared to conventional transmissions. Plus any gains from being able to shut one engine down and run the other at higher load (potentially giving better efficiency) when full power isn't needed.

 

[Open-d]

Yes. But not twins. Not even fraternal. More like big brother and little brother.

If one was halfway to, say, Hi, would the wing engine have enough endurance to do the job, or are they strictly for shorter trips.

 

[Lollygag1]

I will check back in a day when there are 500 replies and still no consensus.

 

[mahal]

If one was halfway to, say, Hi, would the wing engine have enough endurance to do the job, or are they strictly for shorter trips.

I don't have a get-home system, so this question would be better answered by others here that do, like Twistedtree. But I don't see a reason why you can't continue an ocean crossing on a properly sized wing engine. You will be slower especially in rough weather, but better than being dead on the water.

 

[syjos]

Real men don't need no stinkin' twins!

 

[boatbrain]

Obviously a computer hacked by the Russians.

could of been hacked by the Chinese

 

[BruceK]

could of been hacked by the Chinese

Aha, that would be a computer virus! I recall the "Corona" brand typewriter (remember typewriters?). Spooky.

 

[FlyWright]

It's a lot like asking who's better...a blonde, a brunette or a redhead?

It all depends.

 

[koliver]

It isn't about a get home system.
It is about whether or not you lose a season or a vacation if you have a serious failure.
The answer is easy if you have twins, not so easy if you have a single.

 

[Kapn]

I’ve always heard that hull design and chosen cruising speed have more to do with fuel burn than the number of engines. Some manufacturers offer the same boat design with single or twins. Has anyone researched the fuel burn differences under real world conditions with this in mind?
Clearly there is a difference of maintaining two engines, initial cost, etc. but when it comes to actual fuel burn, 2 is not usually double, but what is it actually?

 

[rslifkin]

I’ve always heard that hull design and chosen cruising speed have more to do with fuel burn than the number of engines. Some manufacturers offer the same boat design with single or twins. Has anyone researched the fuel burn differences under real world conditions with this in mind?
Clearly there is a difference of maintaining two engines, initial cost, etc. but when it comes to actual fuel burn, 2 is not usually double, but what is it actually?

Assuming both the single and twins are properly sized (meaning 2 smaller engines, not 2 of the same engine used for a single), it should be a couple percent penalty at most. Basically whatever the extra drag is from the second shaft, cutlass bearing, strut, prop, gearbox power loss, etc. In some cases, getting the prop away from the keel might improve prop efficiency and make up some of the difference.

There's also another thing: 2 props for the same (or only slightly more) total power means smaller diameter props. So depending on hull design, etc. it might be possible to reduce draft by a couple of inches with twins.

 

[Nomad Willy]

Real men don't need no stinkin' twins!

When you take a look at the attitude radiating from the “I support singles” talk it’s obvious the most manly go forth w only one propulsion engine is heavily entrenched in the question. Fear is for sissies.

More will attest to preferring singles more readily than not as it establishes that the talker is manly enough to go forth risking being dead in the water as opposed to being identified as a wuss or sissy that feels safer w two engines. And if you don’t believe me go back and read the comments on this and see that risk taking behavior and manliness is at the center of it all.

The same is alive and well in the sport aviation world. Out of five ultralight aircraft I had the last was a twin. Two 9hp engines.
But I was far more manly just by flying ultralights than the single engine trawler skipper. HaHa

After all that I’m going to dismiss my need for manliness by admitting that if I could afford it I’d have a twin. But most all twin engine trawlers are very overpowered and I’ll have none of that so it’s a single for me. Two 20hp four cylinder engines would be nice but I don’t think they exist.

 

[rslifkin]

After all that I’m going to dismiss my need for manliness by admitting that if I could afford it I’d have a twin. But most all twin engine trawlers are very overpowered and I’ll have none of that so it’s a single for me. Two 20hp four cylinder engines would be nice but I don’t think they exist.

Sounds like the boat for you is something cheap with a pair of worn out engines ready for replacement with a pair of appropriately selected sailboat-sized ones.

 

[RT Firefly]

Greetings,
When we were buying 13 years ago a single was near the top of my must have list for the very reason mentioned by Mr. O in post #3. "...more room to move around the engine..." We were moving from a 34' Marine Trader with a single Lehman, which wasn't hard to work on once you wiggled into the space on either side of the engine. It was the wiggling INTO that space that that was the problem.


We looked at Defevers which DO have larger ER's but some were still a bit tight on the outboard sides with twin engines. Livable, but tight. What really surprised me, at the time was the very cramped ER quarters in a 62' Nordhavn. Aside from price, that was a deal killer right there.


We ended up with twin Lehmans in an ER 15'W X 8'D X 6'H. Lots of room. Solved 98% of my maintenance access issues.

Redundant power plants, extra maintenance and fuel costs and so called "better" maneuverability are really secondary issues, at least for me. Being able to quickly and easily change a broken fan belt, for example, in a hot ER without having to revert to pretzel-like yoga positions while bobbing along in an excited sea state takes precedence.

 

[sunchaser]

I’ve always heard that hull design and chosen cruising speed have more to do with fuel burn than the number of engines. Some manufacturers offer the same boat design with single or twins. Has anyone researched the fuel burn differences under real world conditions with this in mind?
Clearly there is a difference of maintaining two engines, initial cost, etc. but when it comes to actual fuel burn, 2 is not usually double, but what is it actually?

I've seen two detailed instrumented comparisons for single vs twin on the same hull. One was on an NT 52/54 and written up in PMM about 12 years ago. The other was on a KK52 hull with a twin keel setup. The difference was about 10% in both cases. In both cases the twin version had smaller engines as compared to the single.

A few years ago when contemplating a Nordhavn 55 we received information from PAE that the twin version was "about" 5% less fuel efficient. In this case the Gori prop get home was replaced with a twin keel setup thus changing the underwater hull design a bit more than just an additional large prop and rudder. I'd guess PAE has lots more data now as world travelers report back.

Maybe TT can weigh in on what Nordhavn's current data shows. I've heard via the grapevine that tank testing on the new hull N41 showed "little" difference between a single and twin.

 

[Action]

Yes. But not twins. Not even fraternal. More like big brother and little brother.

Siblings

 

[rgano]

If we own a single, we say single. Twins...twins. The circle is complete.

Oh no! I have owned both. What a conundrum!!!

 

[rgano]

I've been away from the forum for some time, and wonder if the debate between between single and twins has been decided once-and-for-all yet, and if so, what is the decision? I am still a bit on the fence, but leaning more towards a single than before.

Since you want to throw bombs, you might as well go full stroke and re-ignite the best dinghy question too? I don't have one anymore; so no dog in that hunt.

 

[BandB]

It's a lot like asking who's better...a blonde, a brunette or a redhead?

It all depends.

Wifey B: Blonde....

Actually I like blondes, brunettes and redheads and although hubby prefers blondes for obvious reasons he also likes the others.

 

[Open-d]

Since you want to throw bombs, you might as well go full stroke and re-ignite the best dinghy question too? I don't have one anymore; so no dog in that hunt.

I coldn't care less about your dinghy or lack thereof. My interest is in considering the feedback about this issue. Sorry to wake you up. Go back to sleep.

 

[Nomad Willy]

Sounds like the boat for you is something cheap with a pair of worn out engines ready for replacement with a pair of appropriately selected sailboat-sized ones.

That’s what happened but single before and single after.
Not much choice on a 30’ diesel inboard.

But I was talking bout TF in general.

 

[rsn48]

You can't have too many engines.

The four big engines are to push the weight of all the engines, its the small engines that provide the speed.... lol.

 

[keith c]

Having owned a GB 36/single/no BT and a Mainship/twins/noBT, When boat shopping I would purchase the boat which is in the best shape and is the best value. These should be the desiding factors. not single/twin. That being said any single must have a BT!

 

[rgano]

I coldn't care less about your dinghy or lack thereof. My interest is in considering the feedback about this issue. Sorry to wake you up. Go back to sleep.

Hey, dude, lighten UP! You apparently didn't see the smiley, meaning no offense, just joshing. If your skin is that thin, well, you are in for some tough sledding around here.

I hope you find an answer you like.

 

[syjos]

Originally posted by Open-d. "I've been away from the forum for some time, and wonder if the debate between between single and twins has been decided once-and-for-all yet, and if so, what is the decision? I am still a bit on the fence, but leaning more towards a single than before."

I coldn't care less about your dinghy or lack thereof. My interest is in considering the feedback about this issue. Sorry to wake you up. Go back to sleep.

With your lack of humor, you didn't stay away from the forum long enough.

 

[Open-d]

Hey, dude, lighten UP! You apparently didn't see the smiley, meaning no offense, just joshing. If your skin is that thin, well, you are in for some tough sledding around here.

I hope you find an answer you like.

Here's your post accusing me of throwing bombs. No smiley face, just an insult. So YOU lighten up and be a bit respectful.

Since you want to throw bombs, you might as well go full stroke and re-ignite the best dinghy question too? I don't have one anymore; so no dog in that hunt.
__________________
Rich Gano
FROLIC (2005 MainShip 30 Pilot II)
Panama City area


Go back at look. Post 51

 

[Open-d]

Originally posted by Open-d. "I've been away from the forum for some time, and wonder if the debate between between single and twins has been decided once-and-for-all yet, and if so, what is the decision? I am still a bit on the fence, but leaning more towards a single than before."





With your lack of humor, you didn't stay away from the forum long enough.

Whatever!