Okay, single or twin??

[Bay Pelican]

Krogen put twins on a big hull type that usually is a single and considered by most to be a long range boat. Do you honestly think Krogen offered the twin thinking it was inefficient?

Eric

I had heard that the twin engine arrangement for the 58 was to provide a lower draft option for those who were concerned about the boat's draft when going to the Bahamas.

The twin engine option reduces the draft by a full foot from 6' 4" to 5' 4".

 

[ranger58sb]

GB36s built here by Riviera usually had twin Cummins 5.9L engines,some had Volvo twin 165s.

GBs built by Riviera?

-Chris

 

[Art]

In this thread's posts, regarding high value boat builders, I've read of Volvo engines being factory originals. For years, in other threads' posts I'd learned of Volvo's being difficult to get service upon as well as poor Volvo factory assistance and expensive Volvo parts that take too long to get delivered. Therefore I've shied away from any Volvo powered boat.


What gives?? Am I missing something here?


Why would good boat builders offer Volvo engines if their upkeep is as difficult as I'd previously learned from other threads? Are Volvo engines superior performers when they are running correctly and do they not often need service?


Just wondering!


Art

 

[RT Firefly]

Greetings,
Mr. A. I was surprised at how many NEW builds that I've seen at recent boat shows have Volvo engines and have been wondering exactly the same thing. The first and only reason that comes to mind is that Volvo is the most cost effective for builders to install in their vessels (for the builders). No builders that I am aware of are the least bit concerned about aftermarket, off warranty "problems".

 

[Rustybarge]

In this thread's posts, regarding high value boat builders, I've read of Volvo engines being factory originals. For years, in other threads' posts I'd learned of Volvo's being difficult to get service upon as well as poor Volvo factory assistance and expensive Volvo parts that take too long to get delivered. Therefore I've shied away from any Volvo powered boat.


What gives?? Am I missing something here?


Why would good boat builders offer Volvo engines if their upkeep is as difficult as I'd previously learned from other threads? Are Volvo engines superior performers when they are running correctly and do they not often need service?


Just wondering!


Art

Toyota brought in ' just in time ' production methods on their car assembly lines.

Volvo brought in ' pay us when you get paid' deals for boat builders.

 

[Codger2]

This is a popular operational mode for a lot of Grand Banks boats in our harbor, particularly in the big charter fleet. They bomb on up to Desolation Sound at 14-16 knots in a day or two, a trip that takes us some four days at 8 knots, cruise around at 8 knots or so enjoying the place, and then bomb on home.

There's a big market here for boats that can do that.

......

 

[Panope]

Diesel fuel does not contain all that much more energy than gasoline.
http://www.diffen.com/difference/Diesel_vs_Petrol
Quote:
“Energy Content of petrol vs diesel
Gasoline contains about 34.6 megajoules per litre (MJ/l)while diesel contains about 38.6 megajoules per litre.”

True. Here are some other reasons why diesel engines are typically more efficient than gasoline engines.

-Diesels have a much higher compression ratio than gassers.

-Diesels have lower pumping losses. Unless operating at full throttle, a gas engine will have a throttle that restricts the flow of air into the engine. The energy required to pump this air past this restriction is not insignificant.

-Diesels operate in a "lean" air-fuel condition where as a gas engine usually operates with rich air fuel mixture (the unburnt, evaporating fuel is important for controlling temperature). Typically, a gas engine will be set up to run increasingly rich as power is increased.

Some modern automobile gas engines are running "lean burn technology". Also, some people (me) run their aircraft "lean of peak" at power settings of less than 60 or 70 percent.

Are any gasoline marine engines set up to run lean?

Steve

 

[go-planing]

I have seen the fuel burn numbers for comparing single to twin installs for the KK 52, Nordic Tug 52 and Nordhavn 55. Surprisingly close dependent upon speed but my takeaway in all 3 cases was a 10% differential favoring the single.

Efficiency of the larger prop on the single no doubt comes into play. Properly over-prop the twins or add larger variable pitch props and that number will become even smaller.

 

[cafesport]

cafesport

My observations are that the ER in a twin N55 was quite workable with engines one JD size down and get home eliminated. What are your thoughts?

Sun chaser, more spacious and workable for several reasons. Engines are a foot shorter in height and length no dry stack and a different tankage system.


Spell check via iPhone.

 

[Nomad Willy]

Steve wrote on post #187;
"-Diesels operate in a "lean" air-fuel condition where as a gas engine usually operates with rich air fuel mixture (the unburnt, evaporating fuel is important for controlling temperature). Typically, a gas engine will be set up to run increasingly rich as power is increased."

Diesels run at 50-1 and 60-1 fuel-air ratios at idle. They are very close to gas engines only at WOT. Consequiently they use little fuel at mid power.
Related to this is the fact that at low power they run w low fuel levels they also have low heat levels. That's the source of the issue of potential problems at low load w diesels. With so little fuel injected you're not going to fry any eggs on exhaust manifolds .. at low loads.

Interestingly though at full bore they (gas and diesel) engines burn about the same amount of fuel mostly because their fuel ratio is about the same .. 15-1.

 

[sunchaser]

Sun chaser, more spacious and workable for several reasons. Engines are a foot shorter in height and length no dry stack and a different tankage system.

I was surprised similarly by the plans for "quite workable' ER space in the KK 52 with smaller twins and the get home not there.

It would seem from the space standpoint the same well designed hull with twins vs a larger single with get home, is not a shoe box stuffed with Imelda's closet.

Also, two years ago I was considering a new design Nordhavn 52 with an aft cabin arrangement. The ER space with twin 4045s was amazing when compared to the traditional N47/52, Nordhavn agreed. Those plans are now available on the Nordhavn website for those interested.

 

[Liberty2015]

GBs built by Riviera?

-Chris

Hi Chris,

Bruce K is correct , under license here in Australia Riviera did build theGB 36 ,and I think from memory GB 42's Europa style, but with out the covered side and rear decks. They were quite popular in the 80's early 90's from here, still got a few here in Newport Sydney and still bring good prices. They were quite fast compared to the traditional GB's

Cheers Chris D Liberty

 

[Ski in NC]

Interestingly though at full bore they (gas and diesel) engines burn about the same amount of fuel mostly because their fuel ratio is about the same .. 15-1.

Thermodynamic efficiency is largely influenced by compression ratio, not so much by fuel/air ratio. Three things really nail gasser efficiency: Lower CR by design. And CR effectively drops further when at part throttle. And at full power, timing is reduced and fuel/air mix richened to limit detonation and control piston/head/valve temps.

Throttling the inlet air is an energy loss, but the larger effect in most areas of the map is driven by the lower effective compression ratio. At 10" HG manifold vacuum, the piston does not start compressing anything until a third of the way up. So a 9:1 CR turns into a 6:1, roughly. That's the main reason gasser efficiency is so bad at light load.

I'm amazed we use gas engines as much as we do. Good for chainsaws, lawnmowers, weedeaters, outboards and fun weekend cars. Anything where efficiency matters should be diesel. IMHO...

 

[ranger58sb]

Hi Chris,

Bruce K is correct , under license here in Australia Riviera did build theGB 36 ,and I think from memory GB 42's Europa style, but with out the covered side and rear decks. They were quite popular in the 80's early 90's from here, still got a few here in Newport Sydney and still bring good prices. They were quite fast compared to the traditional GB's

Interesting, never knew that any were built outside the normal Asian yards...

-Chris

 

[Nomad Willy]

Thanks Ski for #193.

This new stuff gets better all the time. Love the new Yanmar OB and I can't believe the millage my 2013 Accord gets and the turbo Jetta that came before it. A CVT type transmission may work wonders in a boat as the advantages of a straight drive and a variable pitch prop could perhaps both be realized. The CVT probably would be more expensive than pod drives and vari-pitch props.

I've always thought a twin w engines close in by the keel one ahead of the other (staggered if you will) would solve the space problem in the engine room/compartment of twin engined boats. Anybody ever heard of one? No new technology would be required.


With the staggered fore and aft twin .. propellers could be very close to the keel offering grounding capabilities basically the same as a single. A slightly longer single rudder would be mostly out of the prop wash except when turning so it should be more efficient than a single. No prop wash pulling the rudder backwards. The average handy man could do this to an existing boat too.

 

[BruceK]

GBs built by Riviera?

-Chris

Here`s one listed for sale:Used Grand Banks 36 for Sale | Boats For Sale | Yachthub
Check the pic of the electrical switchboard.

 

[Marin]

I just learned the other week that there is a Riviera Grand Banks 36 in our harbor. Took a look at it the other weekend and it's just like the one in Bruce's link. Don't know what it has for engines. I met the owner but this was before I was told what his boat actually is. The configuration is what Grand Banks would have called a Sedan.

 

[markpierce]

We should all have a camera handy. Interesting sightings happen almost constantly.

 

[Marin]

The fellow who owns the Riviera GB36 is from the SFO Bay area, apparently. I was introduced to him by another GB36 owner we have come to know who's in the same part of the marina we are. The fellow with the Riviera GB is a few slips down from him.

So we were standing there talking--- this was a few weeks ago and I was on my way back down the main dock from fetching our groundpower cord from our slip to take to our boat which we had just parked on the yard's Travelift dock after our attempt to sink it out in the bay--- and after we were introduced the Riviera owner asked if our boat was the older GB a few docks farther out. I said yes it was, that's it over there, and pointed across to the Travelift dock. He looked over and said, "I know that boat. It's from San Francisco Bay, right? It used to be named Westwind."

I said that it had had three or four owners before us but the only previous names I remembered were Grand Destiny (when we bought it in Alameda) and Christopher Robin (when it had been in Sausalito).

He said, "It has that really neat dropdown radar mount over the helm, right?" I said, "Yes, it does." He said, "That's the Westwind. I remember that mount. I've never seen another GB with that type of mount."

He took off and that's when my friend told me that this guy had a GB36 Riviera and that it's the only one in the US. Also according to my friend, the Riviera owner knows or knows about just about every Grand Banks in the US, particularly the older ones so it was no surprise that he knew our boat from years past.

When I walked over to look more closely at the Riviera the next weekend at first it just looked like a stock GB36 Sedan. But then I started noticing different details, one of which is the pair of blue stripes around the base of the flying bridge instead of the usual teak trim.

 

[BruceK]

I believe the 36 was the only GB Riviera built under license. Riv construction is quite good, though I was told by a broker that both the Aust. and Singapore built boats get osmosis, one gets occasional big blisters, the other tiny ones all over, I can`t recall which is which.
The original (not the current)principal of Riviera was Bill Barry Cotter, now of Maritimo. Before Riviera, he ran Mariner, and as well as its planing cruisers it sold trawlers under the Mariner name, 36, 39 and a 46,most likely built in in Asia, they look somewhat C&L. The 36 and 39s look nice boats, there was also a sundeck 39, Lehmans were fitted.

 

[Art]

Anything where efficiency matters should be diesel[/B]. IMHO...

Efficiency and diesel engines matter (especially to thems that must keep eye on their wallet… that is) in boats that are doing 400 to a 1000 or more hours per year... or, to long term cruisers who virtually never stop cruising… or, to larger boats that need the torque that diesels can provide – as compared to gas engines. But to weekend/summer-vacation boaters who average from 100 to 400 hours max per year the words “fuel-efficiency” do not really enter into the picture. The words speed and pleasure do!

Sooo... let's just use as example... boats cruised average 200 hours per year:

1. At 1 nmpg doing 17 knots = 17 gal per hr X 200 hr = 3,400 gal a yr X $4 per gal = $13,600 Distance traveled for pleasure cruising = 3400 mi = Costs a bit of $$$, but much pleasure boat travel accomplished for the year! Fairly often visiting places up to a couple hundred miles away not out of the picture at all.

2. At 2 nmpg doing 12 knots = 6 gal per hr X 200 hr = 1,200 gal a yr X $4 per gal = $4,800 Distance traveled for pleasure cruising = 2400 mi = Costs a fair amount of less $$$ than #1… but less pleasure boat travel accomplished for the year as compared to 17 knot cruiser mentioned above.

3. At 3 nmpg doing 7 knots = 2.33 gal per hr X 200 hr = 467 gal a yr X $4 per gal = $1,867 Distance traveled for pleasure cruising = 1400 mi = Costs way less $$$ than #1 and good deal less than #2… but pleasure boat travel accomplished for the year greatly reduced and capability to visit places more than 50 to 70 miles away really becomes long-slow cruise affair.

Hope all my #s and calcs are correct – but, you get the picture.

For #1 the most expensive pleasure boat rendition depicted here the fuel cost extrapolates to only $1133 per month to use a REALLY fun way for getting onto the water and visiting places a fair distance away while still having time to enjoy the location visited.

Pleasure Boating ain’t cheap! Then, of course, we can always get into discussing the huge expense of diesel motors compared to gas motors… But, Please NO.

Basically it all comes out in the wash… prop wash that is!

 

[markpierce]

My boating expenses are 95+ percent fixed, operating 125 hours with a single engine consuming well less than $500 of fuel a year. Regardless, I like the exhaust sound and the added safety of a diesel. Besides, purchasing the boat with a gasoline-powered engine was not an option since I wanted a boat with good railings, wide decks, hull strength, and endurance.

 

[Marin]

I was told by a broker that both the Aust. and Singapore built boats get osmosis, one gets occasional big blisters, the other tiny ones all over, I can`t recall which is which.

If there is a blistering issue with American Marine (Singapore)-built GBs I suspect it has more to do with when a particular hull was made than a general sort of situation.

Howard Abby left the company in mid-1974 after designing and building the molds for the GB36 and 42 and then personally supervising the manufacture of every GB36 and 42 hull starting with the first one in mid-1973, GB36-360. After his departure American Marine's hull quality started wandering all over the map, so to speak. A couple of times they had so many problems they brought Howard back to straighten things out.

According to an interview I read with Howard some time ago, the first time he got them back on track before he left to go home to the US. The second time he claims he threw up his hands in frustration and departed in pretty short order.

What effect their problems with hull manufacturing had relative to blistering I don't know. But apparently their hull quality wavered around some for a number of years.

This is comparatively speaking of course--- compared to many other manufacturers during the same time period I suspect GB's overall hull quality was pretty damn good despite whatever manufacturing problems they may have been experiencing.

 

[Ski in NC]

Art, the key point in my statement was "where efficiency matters.." In some boats, as you noted, it is not the major cost and gas efficiency is ok.

In my case, over 8yrs since build I have logged about 2300hrs. I run a mix of 7.7kts at 1.9gph or 20kts at 11gph. Let's figure half and half. 1150hrs at slow, same at fast. That's 2185gal at slow, 12650gal at fast. Total of 14835gal. At avg of $3/gal, total of $44505. If a gas engine used 25% more, that would be $55611. Difference is $11126, assuming same price per gal, conservative considering dock prices. And 25% efficiency difference is conservative, too.

I bought the used diesel for $14000. A gasser in similar condition might be $4000. Diesel is the win in my case. Already in payback mode. Fuel savings already paid for the diesel premium.

In a year or two, engine will have paid for its whole purchase price in fuel savings alone, and that is at a modest 280hrs a year, avg.

Run a boat 50hrs a year or so, numbers are different as you noted, gas gets the win.

 

[Liberty2015]

I believe the 36 was the only GB Riviera built under license. Riv construction is quite good, though I was told by a broker that both the Aust. and Singapore built boats get osmosis, one gets occasional big blisters, the other tiny ones all over, I can`t recall which is which.
The original (not the current)principal of Riviera was Bill Barry Cotter, now of Maritimo. Before Riviera, he ran Mariner, and as well as its planing cruisers it sold trawlers under the Mariner name, 36, 39 and a 46,most likely built in in Asia, they look somewhat C&L. The 36 and 39s look nice boats, there was also a sundeck 39, Lehmans were fitted.

Bruce,

Riviera also did a 42 GB sedan , there was one kept at the RMYC Newport for quite a while, I think it sold last year and has moved on , it was in excellent condition the vessel was called Aquaris I think

here's a link to one that sold Grand Banks Flybridge Cruiser 42 Sedan Sold: Power Boats | Boats Online for Sale | Fibreglass | New South Wales (NSW) - Church Point Nsw

Cheers Chris D Liberty

 

[BruceK]

Bruce,

Riviera also did a 42 GB sedan , there was one kept at the RMYC Newport for quite a while, I think it sold last year and has moved on...http://www.boatsonline.com.au/boats...-banks-flybridge-cruiser-42-sedan-sold/166382

Apologies for my error, the Riv built GB42 unmistakably reflects the Riv cabin design of the 36, I`d never seen one.

 

[ranger58sb]

Here`s one listed for sale:Used Grand Banks 36 for Sale | Boats For Sale | Yachthub
Check the pic of the electrical switchboard.

Interesting. Looks nice.

-C

 

[Nomad Willy]

Just got an issue of Boating Magazine and there's an article on single v/s twin. It's 100% stupid as they compared a single w a 300hp OB to a twin w two 225hp outboards. They compared top speed, "useful cruising speed", hole shot, towing power, purchase price, maint costs, reliability and fuel economy. Can you guess the outcome? Of course. Even the Barista's at Starbucks could figure that one out.

IMO nothing will be learned unless both boats have the same total power. Often here on TF 240hp boats are compared to 120hp boats and the conversation reads like it's an apples to apples comparison.

If any good comparison comes to pass single and twin w the same power on the same boat I'd like to see it but I know of no such apples to apples comparison.