Looking at this Grand Banks 46: lots been done to it

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Kit_L

Guru
Joined
Mar 12, 2016
Messages
535
Location
Australia
Vessel Name
Suu Kyi
Vessel Make
Custom 40' catamaran

My big question is, what are these like offshore in relatively rough or confused seas? This is not stabilised, and I have never had a semi-planing hull before. An aside: the term "semi-displacement" has become so common in trawlers that can cruise at 12kn, but is 'semi-planing' a bit more accurate?

My wife likes the idea of being able to "zip" from one harbour to another (typically here 75nm), but she gets seasick. The last three times I have been offshore we have left in 1.5–2m swells, but wind picked up, the swells got larger and a sea developed on top. Anyone who has cruised up and down the East coast of Australia will be familiar with this!

All comments, especially about offshore handling, will be gratefully received!
 
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Apparently they are a wet ride, lots of spray but of course that in itself is not a huge deal. At trawler speeds, say 8 kn, they will have a lot of motion in the seas you describe. Going to 10kn will use a lot more fuel but ought to improve ride. Personally I would want stabilisers......

With 750 HP available I suspect going faster will give a quite reasonable ride unless its rough wind against tide in fairly shallow water such as inside the GBR here in Qld. Probably around 15kn will be close to a planing sweet spot. Something like the magnus effect stabilisers, retracted for those speeds, and with some fairing around their hubs would work well IMO.

I do like the 46's, just that little bit of increase in dimensions compared to the 42's are a huge plus. It reads like its had a lot of money thrown at it by the current owner, always a bonus.
 
Insequent wrote: At trawler speeds, say 8 kn, they will have a lot of motion in the seas you describe.

That's what I thought. I have been in contact with the local magnus effect stabilisers rep (DMS has a local person here now) and that is a good idea. They are not cheap, though.

As a live-aboard boat, it looks excellent. I'd prefer galley up, but can live with the present arrangement.

The fact that the tanks are new, and the engines were pulled out at the same time is very encouraging. Like all things, I'd really like to try it out in typical seas, but that is really difficult to organise—especially when the boat's in Melbourne.
 
For a liveaboard, it offers excellent space, comfort, and plenty of facilities. It`s essentially a handsome traditional boat, not as modern in design as some.
It would take a lot of energy to run at 15 knots. It`s less "semi planing" and more "semi displacement" imo. I`ve seen a GB52 "semi planing", an awesome water displacing fuel consuming sight. I`ve also been on that boat, GB build quality is impressive.
The advert doesn`t disclose engine hours, the advertiser chose to delete that item by not completing it, you need to know. The omission suggests it has some hours on it.
What is the condition of the gelcoat? It doesn`t appear particularly shiny. Painting it will not be cheap.
I seem to recall TF member ? Howard, the man who lost his shoes during a shoes off boat inspection, owned one and went bigger. Perhaps he will contribute.
Port Philip Bay gets some awful weather, a local test run could be informative of seaway behavior.
 
The broker told me the Cat 3208s have 3,500 hours on them, and when the engines were out of the boat, compression was tested and all cylinders tested perfectly. That is not reflected in the paperwork that I have seen, though.

Re. the gelcoat: I'd have to look in person.

Re. your comment, "It would take a lot of energy to run at 15 knots", all I can say is "yes!". Our current vessel at 15 kn offshore uses about 70 litres/hr, both engines. The broker says 12l/hr at 7kn; 16 at 8kn. He claims that the current owner did not run the boat at faster speeds enough to know what the consumption is at 12–15kn. The turbos were "stripped and inspected" (again, according to the broker), and they looked fine. I think that if the engines were used gently, as they seem to have been by the current owner, the number of hours is not critical, I think.

I do hope Howard comments.
 
The S/S tanks are less than optimal IMO due to problems welding S/S. I would much rather have the proper alloy aluminum for the tanks. Do some research on the tanks.
 
Apparently they are a wet ride, lots of spray but of course that in itself is not a huge deal.

GBs do have a wet ride but thats because their bow is plumb and relatively fine without flare so reduced reserve bouyancy. The result is the it cleaves waves and goes through them rather than bounce up and over. Along the US West coast, the traditional salmon fleet shared a similar design approach as a strategy to deal with the ubiquitous 6-foot chop from the north.

To the OP - if you will be regularly making 75nm open water runs, you really want a stabilized boat. I know of no one who has owned a stabilized boat who believes stabilization would be optional on their next boat. That said, depending on the severity of your wife's seasickness, stabilization may not make enough of a difference. I have a friend who chose a power cat hoping his wife's seasickness would abate. Short day trips in protected water are fine but anything over a few hours in open water turns her green. Poor gal - she really wants it to be different but ends up very ill. Breaks his heart to see her like that.

Peter
 
The shape of the GB bow is bluff, rather than flared, which yields noticeably more space inside the forward compartment. Hop below on an Albin of equivalent size, or similar design, and you'll instantly see the difference. Also, and I grant that it's a small point, but the reduced flare means the bulwarks on the foredeck are more nearly vertical, which means that when working on the foredeck your feet and everything attached to them are closer to the caprails, stanchions, and etc. I just think it feels more secure.

Going to weather, the GB is definitely a wetter ride than comparable motor cruisers with more flared bows.

Having spent some time in the engine compartment of a GB 46 with the 3208TA Cats, I found it too crowded in there to work comfortably. The 3208 is a great engine (although they become more demanding in every respect as you add turbocharging and after-cooling). But they are bulky, especially with all the TA hardware hanging off them. You can get similar power and performance out of a growing list of inline six-cylinder engines, which are more accessible for whoever is doing the maintenance.

When conditions are boisterous, any unstabilized Grand Banks is going to be a lively ride. Increased speed will tend to transfer the motion a bit more into the longitudinal dimension, and if nothing else, at least will result in getting through the experience sooner!
 
I am cooling on this vessel, I have to say. The ad. says, "max. speed: 18kn; cruise 12–13", but the broker cannot provide fuel consumption figures at the cruise speed. The figures are excellent for displacement speed, as you'd expect. I drive one of the Marine Rescue boats here, and once it's planing, it is very stable in rough seas—but it's got two modern Yanmar 450hp, and it's a relatively light boat. I was hoping that the flattened aft sections of the GB would work in a similar way, but the rescue boat is about eight tonnes, and this boat is about—what? 25 tonnes loaded? That is a guess, and that figure's not part of the specifications.

An aside here: why is displacement often not listed, and holding tank volume almost never? Anyone who lives aboard will definitely want to know holding tank volume!

Peter wrote, if you will be regularly making 75nm open water runs, you really want a stabilized boat.
I agree, and this is how we want to use the boat. Like your friend, I bought a power cat for the same reason, the advertised stability. But what many people don't mention, is that a power cat in confused seas has fast vertical acceleration forces in the longitudinal plane, and some people (like my wife) find these movements just as bad, seasickness-wise, as a relatively slow roll. I built paravanes for our last vessel—it's movement was quite comfortable. We sold her because her accommodation was unworkable for us.

Blissboat wrote, Having spent some time in the engine compartment of a GB 46 with the 3208TA Cats, I found it too crowded in there to work comfortably.
Having been a practitioner of boat yoga with our KAD-300s in narrow hulls for the last few years (replaced the alternator and supercharger belts yesterday), I definitely do not want a repeat of that. Still thinking, but going cold, I have to say.
 
The Grand Banks is basically a planing hull, just with a deep keel (more drag), heavy, and without any lift adding features like strakes, big chine flats, or a reverse chine forward. So it's a planing hull, just not one that planes particularly well (and the combo of being heavy and lacking lifting devices means it takes a lot of power to plane).

I'd expect a GB 46 to have a pretty decent ride in terms of avoiding excessive pitching, as it's got a long waterline for its length and the bow isn't overly full or flared. Roll behavior is where I'd expect comfort problems, but the roll shouldn't be quite as quick and snappy as your powercat. I do see quite a few of the bigger GBs with stabilizers though. Roll comfort does tend to improve in planing hulls as you increase speed. The motion becomes better damped and gets closer to a series of gentle tilting motions rather than true rolling (and it's less snappy at the end of the roll on plane typically).

What kind of sea state (both wave height and period) would your longer open water runs typically be in?
 
Agree on the V8 vs Inline 6. I have inline 6s in my boat and they can be tough to access the outboard sides. I would not even consider my boat with V8s. My beam is 14’.
 
Agree on the V8 vs Inline 6. I have inline 6s in my boat and they can be tough to access the outboard sides. I would not even consider my boat with V8s. My beam is 14’.
It depends a lot on what else is mounted around the engines too. My boat is also a 14' beam, but with 2 gas V8s in the bilge. There's just as much room outboard of each one as there is in between (about 2.5 feet), so plenty of room to sit out there and work on stuff. However, I don't have saddle tanks for fuel outboard of the engines, my tanks are mounted elsewhere. Just some plumbing for thru hulls and the mufflers (next to the transmissions) outboard of the engines, the rest of the space out there is empty.

A GB 46 is 14'9" beam from what I can find, so if the fuel tanks are outboard of the engines, I could see access being a problem, especially if there's not good access to the outboard sides from above.
 
Agree. It has been a while since I have seen a 3208TA but I think that they are quite a bit bigger than a V8 gas engine. And location or fuel tanks can make a difference. I have never been on that model GB either so I can’t say for sure how much access there is but it is something to consider. Also as we get older what used to be fairly good access when we were 50 is terrible when we are 70…
 
Agree. It has been a while since I have seen a 3208TA but I think that they are quite a bit bigger than a V8 gas engine. And location or fuel tanks can make a difference. I have never been on that model GB either so I can’t say for sure how much access there is but it is something to consider. Also as we get older what used to be fairly good access when we were 50 is terrible when we are 70…

Agreed, 3208TAs are pretty bulky engines. Although depending on the equipment layout, a V block isn't always much wider than an inline engine (as the V engine has some of the manifolds and other equipment on top vs sticking off to the side on an inline engine). A quick search turns up that a 3208TA is about 38 inches wide fully assembled. Looks like your Cummins 450Cs should be about 36 inches wide with everything bolted on. So the 3208s are wider, but only a little bit.
 
@rslifkin: your analysis (post #10) seems very sound to me. Given the GB's displacement, there is no way around the cost of the fuel needed to plane. And at displacement speeds, it will roll, though perhaps not as badly as our previous rounded bilge 49' wooden boat. It had a deep keel, too, but it still rolled, too much to be comfortable for my wife.

You asked what sort of seas I'd be expecting in our harbour hops: when boating for pleasure, I don't leave the mooring if the forecast is over 2m, but the last three times I did, by the time I was halfway, the sea state had become confused and the wind had picked up; this can happen very quickly here as you've probably heard. The last trip the 1.5–2m seas had picked up to 2.5, and sometimes more—and I saw 21.8kn SOG going down the face of one of them. As it was a following sea, and this cat has legs (never again) the autopilot could not hold a course, so I was really 'on the wheel' for the last few hours.

The ER pics the broker sent of the GB 47 show enough area around both engines for servicing, I think; I will post here. I don't know if the hatches above the engines lift for headroom; I assume they do.
 

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The ER pics the broker sent of the GB 47 show enough area around both engines for servicing, I think; I will post here. I don't know if the hatches above the engines lift for headroom; I assume they do.
Those ER pics do look good, but I encourage you to get aboard, hop down there yourself, and do a full lap of the engine compartment before rendering a verdict.
 
@Blissboat: I would, for sure.

I will also think about getting magnus effect stabilisers, too, if we did go ahead with this—if stabilised, and treated as a displacement boat rather than the "two-speed" boat my wife would prefer, might be OK. DMS have a local agent here now.
 
Views differ about operating speeds and weather can be an influence but for me it`s difficult to imagine operating this boat above hull speed. It`s designed to cruise distances comfortably, and I`m sure it will. Following Kevin Sanders success with his Bayliner 4788 (admittedly a more rounded hull going aft) you could try bilge rolling chocks first.
Noting you sold the last monohull because of accommodation issues, I wonder about the size and convenience of the GB "double" in the second cabin. A personal issue worth thought at inspection.
In fairness, it seems a nice well kept boat and a shame to pass up without an inspection. We recently drove to Melbourne(Geelong actually, 100km further to the Tasmania ferry), overnight in Albury, easy drive except for the speed cameras.
I think the possible TF GB 46 owner was Howard Mason.
 
@BruceK: I am strongly inclining to treating this boat as you suggest: a displacement vessel that will have an economical cruise of around 8kn. The size of the second cabin would not worry me (the Admiral gets the main cabin, of course). Still thinking on this.
 
We have had 2 GB 46's, one with 210 HP 3208N's, galley up, 3 staterooms, and the other with 375 HP 3208TA's, galley down, 2 staterooms. Both had the centerline queen in the MSR. We lived on the galley down version for 2+ years but were able to cruise very little. Both got about 5 GPH at 8.5 knots and 10 GPH at 10 knots. We saw 15-16 knots on the sea trial with the TA's but 44 GPH. Never went over 10 knots again. Both had holding plate refrigeration which is a POS system in my opinion. Both were in Puget Sound, mostly protected, I would not consider one without stabilization for any offshore work. But lesser boats have done long distances so YMMV. Also both had smallish holding tanks. GB's are well built boats. Good luck!
Regards,
Scott
 
@Endeavor GB 32: thanks for your input. We don't have river systems like yours over here, so we go offshore regularly. 44GPH at 15kn! Thanks for that datum point; that's gold.
I would not consider one without stabilization for any offshore work.
That's the point I'm at now. Plus that galley down is a negative for us. And why, oh why, do so many live-aboard boats have small holding tanks?
 
Probably because the designers never have stayed on a boat long term.

Gotta love faster boats. The fuel consumption can be staggering…
 
@Comodave: you wrote, "Gotta love faster boats. The fuel consumption can be staggering…"

Indeed. 44GPH is ~160+ litres/hour. This just seems wasteful! Not to mention costly. Perhaps the boat I am looking for is a unicorn—might be better to look for a stabilised full displacement hull, with the accommodation and galley we need. And yes: most designers never experience the anxiety of being 40nm up a river, and finding the holding tank full.
 
I have twin 450hp engines in my boat. We usually cruise at a slow plane, but it still uses quite a bit of fuel.

If you want a boat with stabilizers then I would look for one that already has them. It will likely be much less than installing them will be. Even the routine service on stabilizers isn’t cheap.
 
100% agree, @Comodave. I have decided that I will look for a stabilised boat around 45'.
 
I think that is a good choice and you will save some money. Just make sure that the stabilizers have been serviced regularly.
 
I am just having my Naiad stabilsers serviced now. Cost is A$2600 for the 3 year service which inspects the system and replaces the outer seals. The 9 year service pumps grease through the whole system and does other stuff. But if you adhere to the 3 year interval you will be unlikely to encounter additional (expensive) maintenance.
 
The Alaska line of boats has some appeal,this 45 in a different price range, lacks stabilizers, but would go port to port quickly, noting hull design and engines fitted. No FB should reduce movement.
There is an older 42 at 380K, but with 3 cabins, reducing living space.
Perhaps worth consideration long term, if a good one pops up.
 
I am just having my Naiad stabilsers serviced now. Cost is A$2600 for the 3 year service which inspects the system and replaces the outer seals. The 9 year service pumps grease through the whole system and does other stuff. But if you adhere to the 3 year interval you will be unlikely to encounter additional (expensive) maintenance.
I just watched a video of a guy servicing his stabilizers. He has a 70’ Burger, I think. Check out the youtube channel “In too deep”. It didn’t look too difficult to do for the 3 year service.
 
@BruceK, I have been looking at that other one (the older one at $380K; it's named "Tainui"). I have had extensive back and forth with the broker, and like the GB we're talking about here, the ad describes its fast cruise at 16kn, and top speed as 23kn. The raw water sides of both engines were done, but five years ago—and perhaps longer. In our area, five years is the limit, and three better. It is colder in Kettering, though.

Fuel curves better than the GB; about the same consumption at 15kn as the present boat.

16.5 tonnes.

The reservation is that quite a few of the images are of a sister ship—I have asked the broker to ask the owner to re-do these, but nothing so far. No holding tank info.
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