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Old 09-21-2015, 06:15 AM   #41
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Semi,
Yes the rudders do look bigger than on the Hatt.
As to double chine the OA pictured is not what I had in mind but very similar. A much wider flat between the bottom and the topsides as found on the Payson "Diablo" skiff. Would have the dynamics of a much narrower boat. The more I think about it the more I can't understand why it's not common. There are reasons of course and it's probably not just because no one has thought out of the box. But that's always a remote posibility. Kinda like a prospector finding the mother lode but I suspect most good NA's probably get well known by designing convential hulls.

I agree w Kevin and Marin that anticipation is the name of the game on following seas and in other circumstances like plunging into a strong side current.

HOLLYWOOD,
The Hatt is a very popular and respected boat. And got there by being a very good design.

Rusty Barge,
Thanks so much for the very interesting link.
What is puzzling to me is how the exit lines at the aft end of the bulge would not be enough drag to prevent the boat from getting anywhere near 20 knots. The abrupt termination of the bulge would be too much drag .. IMO. But appearently it's not. However if shown the lines beforehand I would have said the speed would be limited to 13 or 14 knots
.
What's even more surprising is the original power installed...

>'The engines favoured by the original builders were twin 106 hp Volvo Penta D32s, linked to sterndrives, and 105 hp Mercedes-Benz OM352s, with V-drives, top speed being about 16 knots in each case. This configuration generally required more use of the trim tabs to travel at the optimum angle'

That's some efficient hull!
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Old 09-27-2015, 06:00 AM   #42
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Our Halvorsen 57 will tend to wander when in a following sea , but they need to be fairly big sea's. On my last boat a 50 footer when originaly launched it apparently tendered to broach , round up. So the original owner had the keel extended to almost a full length keel and this fixed the problem to a point where it was one of the most straight tracking vessels I have ever had. It had twin 210 hp cummins and was a pleasure to be on in following sea's, the bigger the better. I suppose when docking it needed a bit of extra grunt to kick the stern around , but still fairly responsive.
I have been considering doing the same with Liberty, and I recently had the original Owner who commissioned Liberty on board for a couple of weeks whilst Circumnavigating Tasmania and he agreed with me that extending the keel in length may make her shoot straighter in a following sea.
We have active stabiliser fins, but they still have the original control system which reacts to roll. We have been advised that if we were to update the control system this would dramatically improve the performance in following sea's also.
So these are two items I have on the agenda at present.
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Old 09-27-2015, 07:04 AM   #43
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As has been posted...Trim for "bow up" in a following sea. Also, trimming in a quartering sea really helps with the ride.
You're right Walt. More by necessity and good luck than intention, because most of my tankage is in the aft part of the hull, (PO did not remove the old fuel tanks, so they are still there as just buoyancy now), while not giving an obvious bow up trim, it does put more weight than usual aft, and my Clipper tracks beautifully in a following or quartering sea. I have seen over 11 kn, actually surfing, on big following waves, with a nice light feel on the wheel, and not a hint of broaching. Although I must admit Marin's comments re anticipating rudder corrections are spot on.
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Old 09-27-2015, 08:00 AM   #44
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Best way to control yawing in following seas I have found is to tow a drogue.
We used to take a 39' Mariner full displacement down to Tasmania annually and whenever we had following seas (and they were big!) (we were young and stupid) we deployed a torpedo shaped hard plastic drogue called a Sea Squid, made in New Zealand.

As soon as it is deployed on a long line, with bridle, and chain just ahead of it to keep t down it is happy days! Literally straightens the boat, autopilot just steers happily, where without it forget it, no hope, you would have to steer all night long. Much harder to hand steer downwind at night without any reference points for anticipation. The drogue is incredible.

Limits speed to no more than 10 knots , it just hauls the back of the boat back straight. If quatering seas just set it to one side with bridle.

For long passages well worth the effort to deploy it, not so for a short run locally or in crowded waterways where someone might get caught up in the tow line, we deploy it out around 100 meters at sea so it is pulling through swells well behind you, its magic.

Still have it, still use it, it transforms any boat at or under 10 knots, we did use it on our Bayliner 4788 with great success up to 12 knots.
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Old 10-09-2015, 11:54 PM   #45
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A photo of an Ed Monk designed Ocean Alexander hull. The boat cruises on the "inner" hull width/chine at slow speeds. When it begins to squat with application of higher power, the outer width provides additional lift.........

So, here's a hull with some genuine engineering applied to the efficiency aspect of design. When you read an OA ad that says engineering and performance are their overriding design objectives, they aren't blowing smoke. ]
My OA 42 Altus is one of the best rides I've ever had on the water. (I believe, however, that the Offshore 48 has a better ride!)

Transitioning from 8 knots to 17 knots and on plane is a delight! Just an increase in speed with little to no bow rise. No tabs needed except for countering quarterly seas.
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Old 10-10-2015, 02:09 AM   #46
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Sounds good,

What do you believe makes the difference with the ride, I am interested in your thoughts?

Cheers Chris D Liberty
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Old 10-10-2015, 02:38 AM   #47
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My only solution to that other than a new course is to raise the bow as high as I can to try and avoid bow steer.
I'd say those are your only options to minimise the yawing, along the the anticipated steering.

Every boat seems to have one type of water it doesn't like. With yours it's quartering seas.

With me, if the seas are quartering or more aft, the boat loves it. I leave it on AP with no yawing unless its very nasty. Anything more on the beam, is where I run into rolling problems.

Tough to find a boat that is steady in all conditions without some sort of stabilization.
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Old 10-10-2015, 11:45 AM   #48
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Walt's good ride (and I'm not talking about a car) is probably because the boat's big and somewhat heavy but speed probably has more to do w it than anything else. The dynamics of boat motion favors speed ... up to a point that is probably higher than most trawlers cruise. Those big props probably have a stabilizing effect also.
Interestingly many boats have been built that are very similar but quite different in that the lower chine is soft .. Instead of hard. And for a different reason than the OA I think. The double chine lower being soft is to reduce the velocity of beam wise water velocity for the purpose of reducing spray and holding more water under the boat giving more lift. The hard chine low may be mostly for reducing wetted surface. Don't know if it works that way though.

AusCan,
I mirror your thoughts almost exactly. And for the obvious reason ... our boats are very similar.
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Old 10-10-2015, 12:57 PM   #49
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Walt's good ride (and I'm not talking about a car) is probably because the boat's big and somewhat heavy but speed probably has more to do w it than anything else.
Couldn't agree more! The ability to alter one's speed to varying sea conditions is huge! When the sea is dead calm I run at trawler speeds and enjoy the noise reduction and the super smooth ride. But when things start to get a little bumpy, I put more coal on the fire to smooth things out. Both my wife and I really enjoy our boat's ability to do this.

With both engines running this is our speed range.
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Old 10-10-2015, 01:24 PM   #50
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Walt actually that's not what I meant. However your point is well taken.

I'm talking about a dynamic form of stability that's present well above hull speed. A boat at rest or below hull speed rocks and pitches around sort of wallowing between waves but a big chunk of that wallowing motion disappears when a boat goes fast enough to leave the froth behind and leave her transom exposed to the air and sunlight. I don't have a name for it and don't recall reading about it either. Perhaps it's all just in my head wallowing around??? I like the motion of boats a little faster than FD excluding higher speeds w pounding and porpoising.

Walt maybe Larry could get rid of that rubber Duckie in the next slip in your avatar. Or you could take another picture. It dosn't flatter your boat.
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Old 10-10-2015, 01:30 PM   #51
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Walt maybe Larry could get rid of that rubber Duckie in the next slip in your avatar. Or you could take another picture. It dosn't flatter your boat.
Will do! How's this?
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Old 10-10-2015, 02:33 PM   #52
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Now take a pic w a little bit more .........

Naw just kidd'in.

Did you do that Walt? You're ahead of me.
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