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Old 05-10-2013, 06:39 PM   #41
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At about 4-6 kts coming out from my slip, down the fairway and into the channel requires using the two engines for steering. At this speed, the rudders are useless and I rarely even use the wheel for this maneuvering.
While I think the term "Motoryacht" is being used incorrectly here to differentiate fast boats from slow ones (Grand Banks boats with full-width aft cabins are called motoryachts, for example) the notion that the rudders on fast boats can be nearly useless for slow-speed maneuvering is valid and is not a new problem. I've been told more stories by WWII PT boat vets about the pathetic maneuverability and subsequent accidents, some funny, some not, of these boats at slow speeds than stories about any other aspect of the boats.

The 80' Elco was the worst with its tiny spade rudders placed behind each of the three props. At speed I've been told by the guys that drove them that the boats handled beautifully. At idle they were an absolute bitch. As Tony describes above, steering was done with the outboard engines, the center engine being used only in the event they had to stop or back the boat away from a collision with something.

The problem was compounded by the fact that all three props on a PT turned the same way. So there was a degree of prop walk that had to be contened with as well.

Most diesel cruisers--- like GBs for example--- have rudders sized to be effective at speeds from dead idle to 15 knots or so. Faster than that and the spade GB rudders are probably getting way too draggy and dangerously influential. The photo is of our boat. This shape and size of rudder is common to most of the GB line other than the current models. They were made of bronze but at some point they changed to fiberglass. Ours are bronze.



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Old 05-10-2013, 07:12 PM   #42
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Why does every posting having to devolve into a discussion of twin versus single.
The never ending debate. Ok I get it. The poor guy actually asked some very good questions that many of you have so much experitise, but instead bla, bla bla.

OK, so my two cents and it have nothing to do with twin vs single, well sort of nothing.:-)

When I finally decided on our 42' krogen, it was because I realized we needed the efficiency of the hull and engine. I needed a boat that could be BELOW 2 gal an hour, otherwise I would not be able to afford to go anyplace on my pension and the whole point was to blow this Popsicle stand.

My 42' Krogen will do 6 knots at 1 gal per hour; 7 knots at 1.5 gal/hr and 8 knots at 1.8 and hull speed (8.3 kts) at just above 2.

This clearly is a function of the hull design (more than just full displacement) and the engine sizing (no un-useful horsepower).

In reading most posts in this forum the last few months, many of you have some really nice and affordable boats. i find myself thinking, did I check that boat out??

But it always gets back to the fuel and design efficiency.

If yo have an engine that will push the boat at 15 to 20 kts, it will not be as efficient at 7 knots. AND then if you have two of them, let's talk about twins vs singles.

feeling feisty now


Now answer the rest of his questions. i would love to hear the debate.



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Old 05-10-2013, 08:03 PM   #43
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Why does every posting having to devolve into a discussion of twin versus single. The never ending debate..... The poor guy actually asked some very good questions...
Re-reading Pluto's original post it seems he had two basic questions. Paraphrased, they were how vulnerable in reality is the running gear on the so-called go-fast boats, and can a go-fast boat be controlled accurately and safely at slow speeds?

My short answers are "very" and "it depends."

Having never run a V-bottom go fast boat other than our Arima fishing boat, I can only say that the Arima slides all over the place at slow speeds while maneuvering. At slow speeds, by which I mean the 4 knots that is so often the speed limit in harbors, the boat "wanders" in terms of heading and requires ongoing helm corrections although they are not serious. I assume a larger boat of the same no-keel, V-hull configuration will be somewhat similar.

The friends we boat with have a 36' lobsterboat. Commercial lobsterboat hull with a larger house and forecabin on it for cruising. It is a semi-planing hull made to go about 15 knots with 420 hp. With fuel prices the way they are, they run the boat these days at about 8-9 knots. The boat seems to be quite steady at that speed in terms of holding a heading.

But..... being a lobsterboat hull it has a fairly substantial keel. So it tracks well at any speed.

When the water gets rough, however, they kick it up to 12 to 15 knots because at slow speeds in rougher water the hull really wallows around despite the keel. So speed is the solution to smoothing out the ride and tracking accurately in his boat.

In our heavy (30,000 pound), deep keel (comparatively speaking), boat, the tracking in rough water is just as good as the tracking in smooth water unless the waves are coming from astern and trying to knock the boat into a broach. But where we get knocked around constantly by following waves, our friend simply speeds up to where he is going faster than the waves. End of problem.

The exposed running gear on a twin and the risk thereoff is a question that relates only to twins--- it's not a single vs twin question. To that, the only answer can be, "It depends on the boat and the waters the owner is cruising in." Up here, there is a lot of stuff in the water. I know that in our Arima at 30 mph, we have to be pretty alert to what's out ahead of us. We bought the boat new in 1987 and haven't hit anything damaging yet but we've had to do a few hard (sliding) turns to avoid something that got past our distance scan.

The GB at 8 knots is a much easier platform to see what's out there and have plenty of time to avoid it. And there is no slide to its turns and the rudders are big so it's easy to maneuver precisely in tight quarters or to thread one's way through a crab pot float field or miss the deadhead Mark illustrated on the first page of this thread.

In the end I think Pluto has to decide what kind of boating he wants to do. Fast, slow, or somewhere in between. GBs can be run fast (like 15, 16 knots) if you put enough engine power in them but the fuel consumption goes thorugh the roof. A late model GB42 with the stock 400-plus hp Cats in it burns about 6-7 gph to go about 9 knots. These engines will push the hull up to a continuous cruising speed of 15 knots or so very comfortably, but now the fuel burn is 23-24 gph. So not quite twice the speed for almost four times the fuel burn.
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Old 05-10-2013, 08:20 PM   #44
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Marin - can you do 25 words or less?
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Old 05-10-2013, 08:26 PM   #45
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Sure. But I'd rather answer all the follow-on questions up front rather than have to keep explaining myself later.
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Old 05-10-2013, 09:15 PM   #46
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Sure. But I'd rather answer all the follow-on questions up front rather than have to keep explaining myself later.
Really?
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Old 05-10-2013, 09:20 PM   #47
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Really?
No worries mate. Only 103 posts left to go and then I'm done.
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Old 05-10-2013, 09:56 PM   #48
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Marin's answer:

"My short answers are "very" and "it depends."


That sums it up pretty neatly. So, I guess this thread should be over if other comments are not allowed.

I didn't miss the significance of Marin's number. Marin while 10.000 is a milestone there is nothing magic about it. It's not the number but the content that matters.
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Old 05-11-2013, 01:34 AM   #49
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No worries mate. Only 103 posts left to go and then I'm done.
At 10K Bon Voyage Marin!
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Old 05-11-2013, 01:39 AM   #50
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I don't believe it: not until every boater has replaced their Bruce/Claw anchor, has acquired a dual-engined boat, and shunned forward-leaning pilothouse windows.

Contrary to Marin, I'm the antithesis of those philosophies.

Prediction: Marin will aim for at least 100,000 posts, or more.
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Old 05-11-2013, 02:12 AM   #51
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Prediction: Marin will aim for at least 100,000 posts, or more.
Nope. 9,999. It's a promise I made to myself several years ago to not break 10,000. I mean, come on. Ten thousand posts to an Internet forum? That borders on sick.

It remains to be seen if I can do it but I'm sure as hell going to try. The GB owners forum should take care of any Internet connection I want to the boating world. And I only post there a couple of times a month on average.

So just 101 posts to go. I'll try to use them wisely.

I suspect the only thing I'll really miss is sharing photos because we occasionally get some nice ones on our halibut fishing trips up the north end of Vancouver Island and cruises into lower BC.
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Old 05-11-2013, 02:27 AM   #52
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Nope. 9,999. It's a promise I made to myself several years ago to not break 10,000. I mean, come on. Ten thousand posts to an Internet forum? That borders on sick.

It remains to be seen if I can do it but I'm sure as hell going to try.
Borders????

Crap - Don't do it Marin!! You'll have cold sweats and headaches! Every Forum deserves to experience/have the ying and yang of contributors... You're always one or the other... usually the other - LOL!
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Old 05-11-2013, 04:41 AM   #53
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Nope. 9,999. It's a promise I made to myself several years ago to not break 10,000. I mean, come on. Ten thousand posts to an Internet forum? That borders on sick.

It remains to be seen if I can do it but I'm sure as hell going to try. The GB owners forum should take care of any Internet connection I want to the boating world. And I only post there a couple of times a month on average.

So just 101 posts to go. I'll try to use them wisely.

I suspect the only thing I'll really miss is sharing photos because we occasionally get some nice ones on our halibut fishing trips up the north end of Vancouver Island and cruises into lower BC.
10k posts on an internet forum is nothing.

On other forums many posters have 100k +
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Old 05-11-2013, 09:21 AM   #54
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Should this actually happen (and I think it will) I, for one, will miss his writings as they are well thought out and always informative. I have learned from his travels but won't go to the GB Forum to continue the process.

I can say the same for Moonstruck, Flywright, dwhatty, and a few others that escape me at the moment. Marin's posts are somewhat lengthy at times but don't most of us wish we had a little more length? (ops)
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Old 05-11-2013, 10:50 AM   #55
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You know why they round over the aft top edge of rudders... So they won't pierce the hull when you bend over the shaft in a good hard grounding.
So true!
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Old 05-11-2013, 11:00 AM   #56
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We're thinking about keeping it south during the winter so we can do a few trips to some different places each year.
Good idea. You are only a couple or 3 hours drive from most anywhere in south Florida. Cars are much more economical to run than boats. Moonstruck has no permanent "home port". We leave her in various area for several months to explore before moving on. Living in Florida, you can do both.
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Old 05-11-2013, 11:48 AM   #57
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Thank you all for your comments. Since our "mission" will be to live aboard for a few months at a time, and our cruising area will be the Bahamas and the Loop, I think we will be better off with a heavy displacement type boat that can take some licks. I have been boating long enough to know that shit WILL happen. I do like the modern interiors of some of the Sea Ray, Baytliner types though.
Now, would you suggest a single or a twin engine?
JUST KIDDING!
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Old 05-11-2013, 07:54 PM   #58
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Good idea. You are only a couple or 3 hours drive from most anywhere in south Florida. Cars are much more economical to run than boats. Moonstruck has no permanent "home port". We leave her in various area for several months to explore before moving on. Living in Florida, you can do both.
We are excited about the prospect of doing the same. Pretty much anywhere on the St John's River is within a 40-60 minute drive, so that's on the agenda!
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Old 05-11-2013, 08:05 PM   #59
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No worries mate. Only 103 posts left to go and then I'm done.
Really? Can we hold you to that? I thought you were done when the "project" was over weeks ago.
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Old 05-11-2013, 08:15 PM   #60
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Nope. 9,999. It's a promise I made to myself several years ago to not break 10,000. I mean, come on. Ten thousand posts to an Internet forum? That borders on sick.
We'll drink to that.

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