Twin vs single

CaptainSEA said:

Twins can also have shaft and prop. Protected as per photo of my Selene

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A rare beast.

markpierce said:

A rare beast.

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That’s the beauty of dealing with Selene yard, a complete FD semi customed boat at the price of a production boat...

These double keeled twins probably aren’t as fuel efficient.

The difference on a single v/s twin w one keel is fly-stuff. Some twins are probably more efficient than singles.
Lots of variables to stack up.

markpierce said:

A rare beast.

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Not really. KKs and Nordhavns can come this way too if one is so inclined.

Singles with perfect designs can have strike issues too. A good friends Nordhavn 55 hit some ice near Petersburg AK this summer. Both main and get home drive trains damaged.

CaptainSEA said:

That’s the beauty of dealing with Selene yard, a complete FD semi customed boat at the price of a production boat...

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Are Selens full displacement?

I thought they were semi.

CaptainSEA said:

Twins can also have shaft and prop. Protected as per photo of my Selene

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Unreliable memory of the one or two past "twins vs single" chats is that Gulfstars have protected twin props. Never seen one for myself, probably never will.

sunchaser said:

Singles with perfect designs can have strike issues too. A good friends Nordhavn 55 hit some ice near Petersburg AK this summer. Both main and get home drive trains damaged.

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A friend of ours wrecked their prop and shaft on their keel/skeg protected single engine trawler on the ICW a few years ago (and, no, not on the Rock Pile, which is the first thing I asked when he told me about it). They still don't know what they hit.

I told him I would have bet that what happened to him was darn nigh impossible, before it happened.

CaptainSEA said:

Twins can also have shaft and prop. Protected as per photo of my Selene

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Also mine.

Soo-Valley said:

Know your boat.
Unless there was a 'V' in a reef that I threaded the keel into the props are protected as the forward part of the keel would hit first. Sure run aground and have the tide drop. lean over prop shaft damage. Sure run over a water logged object and it may take out one of the shafts. A lot must all conspire against you. But please stop saying props are unprotected suggesting imminent damage awaiting.

View attachment 94547

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Also have well protected twin props and rudders:

syjos wrote;
“Are Selens full displacement?

I thought they were semi.”

The one in post #59 is not even close to FD. SD to be sure.
The GH in #69 is clearly FD.
The one above in #70 is also SD....
IMO

The Seaton above has a very interesting fore and aft support for the lower shoe. Never seen that before. Probably too much drag for much in the way of SD speeds. But w props that far inbd. she probably runs straighter than most running one engine.

Here are my twins on a KK42. They only built 5 like this. A good 2’ to the bottom of the keel. You can see the blank in the center where a single shaft would exit

Art said:

Go for the Gusto... Go With Twins!

16 to 17 knots [on full plain] = 1 nmpg

When we have desire to get there more than twice as quick... #3 works well.

I do really like the many speed levels as well as hard chine handling capabilities when on full-plain and hard chine stability while at anchor that exists with planing hull and twins.

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Although I really agree with the advantages of a single engine trawler, Art's post above & the performance of a twin and what it can bring to the party are traits that I'm addicted to.

Nomad Willy said:

syjos wrote;
“Are Selens full displacement?

I thought they were semi.”

The one in post #59 is not even close to FD. SD to be sure.
The GH in #69 is clearly FD.
The one above in #70 is also SD....
IMO

The Seaton above has a very interesting fore and aft support for the lower shoe. Never seen that before. Probably too much drag for much in the way of SD speeds. But w props that far inbd. she probably runs straighter than most running one engine.

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My Selene 80 in post #59 is a full displacement hull, twin engines!!!
Almost all Selene, no matter the size are FD, may be you should go and visit the shipyard in Zuhai, China and check by yourself...
Please check your sources before posting such wrong and misleading informations

The Selene 49 and 54 with near 47' WLL advertises an 11.5 knot top speed and a 9 knot cruise.

Of course when you put small enough engines in any boat they're all pretty much displacement. .. But that doesn't mean their hull shape is.

CaptianSEA,
You’re welcome to your opinion.

Meridian, nice setup.
Most floating debris works it’s way outboard as the boat moves fwd so a centered propeller has the advantage. But your setup may be as good or better hitting things not floating.

Nomad Willy said:

CaptianSEA,
You’re welcome to your opinion.

Meridian, nice setup.

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Opinions are different from facts!!! Don’t know where you got your sources from but please check again, as far as I am concerned as well as hundred of Selene owners, we know pretty well the technical specs of our boats.
Have a good day.

psneeld said:

The Selene 49 and 54 with near 47' WLL advertises an 11.5 knot top speed and a 9 knot cruise.

Of course when you put small enough engines in any boat they're all pretty much displacement. .. But that doesn't mean their hull shape is.

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Understood, but at 2 meters draft, 2 x 450 hp for a speed of max 12.5 kts and bulbous bow, a 2500 nm range and an FD hull design I would not classify my boat as an SD as stated earlier or would you also consider a Nordhavn 64 or 76 as an SD boat???

Captian SEA,
Speeds or speeds attainable is not an identifying element of FD/SD definition.
It’s all about hullform. If you don’t at least have some QBBL angle aft the hull is either planing or SD. Not ever FD.
I don’t follow Nordhavns. Show me a pic of their stern below the WL and I’ll comment. In a new thread. This is not on topic.

CaptainSEA said:

Understood, but at 2 meters draft, 2 x 450 hp for a speed of max 12.5 kts and bulbous bow, a 2500 nm range and an FD hull design I would not classify my boat as an SD as stated earlier or would you also consider a Nordhavn 64 or 76 as an SD boat???

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I just stated manufacturer specs, whether they are facts or not.

I also didn't comment on all Selenes....just those 2

Despite your physical description of your boat...do you consider boats that can go 1.7 times the square root of the WLL full or semi displacement?

From the Selene website, under "Yachts/The Selene Advantage:"


Didn't look at individual model descriptions...

-Chris

Nomad Willy said:

syjos wrote;
“Are Selens full displacement?

I thought they were semi.”

The one in post #59 is not even close to FD. SD to be sure.
The GH in #69 is clearly FD.
The one above in #70 is also SD....
IMO

The Seaton above has a very interesting fore and aft support for the lower shoe. Never seen that before. Probably too much drag for much in the way of SD speeds. But w props that far inbd. she probably runs straighter than most running one engine.

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Not sure whether displacement or semi-displacement. Best I can tell from photos the QBBL angle is around 6 degrees. Regardless, there will be no semi-displacement speeds for us. With 50' LWL and 300 hp to push 45 tons we cruise 6-7 knots, topping out around 10 knots.

DCDC,
I started another thread on FD/SD.

Nomad Willy said:

Captian SEA,
Speeds or speeds attainable is not an identifying element of FD/SD definition.
It’s all about hullform. If you don’t at least have some QBBL angle aft the hull is either planing or SD. Not ever FD.
I don’t follow Nordhavns. Show me a pic of their stern below the WL and I’ll comment. In a new thread. This is not on topic.

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Hi,
Your answer regarding not following Nordhavn tells me all....

Thank you anyway for your contribution.

ranger42c said:

From the Selene website, under "Yachts/The Selene Advantage:"

The design incorporates the fuel efficiency of a full-displacement hull. A full-displacement hull is designed to remain fully in the water throughout its entire range of speed. This requires a fraction of the horsepower that semi-displacement or planing hull requires to attain optimum speed. A full-displacement hull will be capable of maintaining speeds in the 7- to l2-knot range while burning a minimum of fuel.​

Didn't look at individual model descriptions...

-Chris

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Thanks for your post, in fact just making a quick surch on the net and it will become clear that Selene are FD, unless the articles and reviews from Passagemaker and the like are all fake!!! I am sure that Howard Shen, the world renowned Naval Architect and owner of Jet Tern Marine (Selene Brand) would be happy to learn that according to a TF member, his designs are not what he thinks, I will send him a quick note today to let him know...

CaptainSEA,
I started another thread for you to address your concerns.
Called SD/FD and I’ll transfer your post here over there.

It's all personal preference. Each of us values pros and cons differently.

Single props and rudders are better protected, but my first twin was 1961 and I never damaged a prop. I operate in log country and more recently Japanese tsunami debris. I have purposely grounded, carefully on mud and sand banks for various reasons and sometimes by accident. But the bow grounds long before the props are in range of the bottom. When a friend was on watch, hit a big log in Canada in my current boat without damage. I have a monel plate on the bow. No damage to the bow or props.
The fuel savings is not that great for a single. And a single can be a handicap if you operate in places with strong currents. My boat on one engine goes less than half the speed with two and that's freewheeling the prop.

With twins, in remote places, you can make repairs between parts of the two engines to get one running.

I have a day tank and feed all mains and generators from that. And that's the setup I usually have in all boats/ships I've owned, built or operated for others. I've never had a bad fuel problem in 58 years of running my own boats. Those that have should maybe question their methods and maintenance.

Lepke
Seems you're a good experienced skipper who can make about any drive train setup work quite satisfactorily. Good post.

Nomad Willy said:

The GH in #69 is clearly FD.

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Willy, can you explain why post 69 is FD. I read the brochure on it and it says FD, but any description of FD says rounded bottom.
Looking to learn something.

Soo-Valley said:

Know your boat.
Unless there was a 'V' in a reef that I threaded the keel into the props are protected as the forward part of the keel would hit first. Sure run aground and have the tide drop. lean over prop shaft damage. Sure run over a water logged object and it may take out one of the shafts. A lot must all conspire against you. But please stop saying props are unprotected suggesting imminent damage awaiting.

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This exactly. We spend most of our boating time in the Bahamas and Florida. I've run hard aground twice and bumped many many times. It's the price of entry where we go. I only did prop damage once and I would have damaged a single then as well.

The keel is lower than the props and rudders.