[Fortunate One]

I'm curoius how the Ocean 48 rides with very little deadrise at the transom.

If any owners answer I would like to know what HP are you running.

I hear so much about how deadrise at the transom makes for a good head sea boat. I hear the Viking about this size has a lot of deadrise at the transom and is a great running boat, until you put the hook out, then she truns into a rock and roller.

The reason I'm asking is I'm having a custom one-off express built. Deadrise from the bow , midship and transom is as follows: 63 deg., 18 Deg, 3 Deg.

The naval architect expects only a 3 degree bow rise at cruise. Idea is to keep the pointy end of the boat in the water instead of riding Bow up like many express boats do.

I was told that the Ocean 48 has a similar displacement and beam along with similar deadrise. Only difference I see is in a lot of the pictures of the 48's I see they are running with more than a 3 degree bow rise.

I realise we'll be leaving more of the bow in the water and therefore burn more fuel but the architrect said this is will help in a great deal in a head sea.

We're looking to power her with at least 800 Hp. Fuel tank is about 925 Gallons so we can reach the far northeast canyoun and stay for a couple of days.

Can anyone give me any honest opinions on how their 48 Super Sport rides?

[AMG]

I have no experience with the Oceans, but in general you shouldn´t be afraid of getting the bow up. If this will be too much it can be corrected with a small extension or with trimtabs, or by moving the center of gravity forward, with a trim tank or just moving some gadgets a bit.

If the boat should go nose down, it is not easy to correct afterwards...

Maybe I should add that 3 degrees is just fine, faster boats rise only 2 degrees.

[Fortunate One]

AMG,

Thank you for the reply.

The designer is placing systems in locations that will work with a bow rise as I have listed. I think the Donzi 58' Express also has very little bow rise and I really like the ride profile of that boat.

Do you have any thoughts on the slight transom deadrise. I'm concerned about the boat pounding. The architect states the boat will not pound. He said it's similar to the hull of some of the Rybovich boats.

[AMG]

Not pounding is a relative expression. I have been on a 172 metre cruise ship that was pounding and actually got the whole bow bent in a seaway. But I think he means not pounding in a normal sea at the design cruising speed.

Adding more power than she was designed for can be good if used as reserve power for bad conditions, but bad if you will exceed the design speed. This is the big difference to a deeper V that normally just go faster with more power.

Pounding also depends on the total weight of the boat, is it a heavy built boat, 3 degrees stern deadrise is no problems since it rarely becomes totally airborn.

[YachtForums]

The new Rybo hulls were designed by Donald Blount, a member of YachtForums. They are fast and ride very level, with minimal bow rise. I have the pleasure of watching a wide variety of large sportfish boats running on-plane everyday, as I live near a major inlet that has no speed restrictions. Without question, Rybo’s appear to be running faster than most. It’s possible the owners are pushing their boats harder than the rest, but these boats are running noticeably more level, along with some Merritt’s.

Each of today’s builders try to strike a combination of a good wave-penetrating ride and stability at rest. There are so many factors that figure into this equation, including weight, CG, shaft angle, horsepower, deadrise, entry, hull flair, chines, strakes, etc.

For sportfish boats, I think one of the more important additions include tunnel-pocketed props. They reduce shaft angle, allow a shallower draft and help to recess protruding appendages. Tunnels can also help induce ventilation, which can increase RPM’s. As a side benefit, tunnels can actually help a sportfish back-down better, as they provide a nominal amount of lift when the props are reversed. The forward section of the tunnel helps divert reversed water downward, which should add some lift when backing down. As a by-product, the exit point of the tunnels reduces the overall surface area of the transom, which can also offer less resistance when backing down.

For the express boat you’re building, you need to consider where you will be operating the boat and what your expected cruise speed will be. If your native waters are rough and you will be running at higher speeds, then the simple answer is go with a deeper deadrise, sharper entry and reduced beam. If your waters are calmer, or if achieving higher top speeds and stability are a greater priority, then the opposite may apply. But… deadrise, entry and beam are simple parts of the equation. Your designer will need to consider all of the parameters mentioned above and more. Weight, CG, hp and operational speed must also be factored in.

If it all possible, try to minimize tabs. If a good hull form is achieved and the CG is right, you will need very little tab. Yes, they are helpful for getting on plane, but they should not be relied on to set the proper ride angle of the hull. Speaking of... I really like the underwater exhaust systems that use exhaust pressure under the hull (near the transom) to add lift when coming on-plane and help ventilate some of the running surface too. There’s at least one company (can’t remember the name) that is marketing re-fit kits for this, as well as OEM components to incorporate the system into new builds.

Among other considerations is how the hull works above the waterline too, such as spray and wave deflection. A narrower beam boat tends to be a little wetter, especially in choppy, quartering seas with windy conditions. Builders such as Buddy Davis address this with pronounced (Carolina) bow flairs and tumblehome transoms.

I’ve only touched on a couple of areas and Lars has already provided some good advice. The plethora of design considerations is the reason most people opt to purchase boats from existing builders with a refined and proven history. But… that doesn’t mean they can’t improve on their existing designs… or you and your designer can’t build something better.

Good luck!

[Loren Schweizer]

I can't resist putting my "two cents" worth in here.
The naval architects here are right, of course, and they even sometimes hit the bullseye.
Some (not in this forum!)do not, however. A famous boatbuilder once took their 43 Convertible and decided to come out with an Express version back in the late '80s.
The original hull worked just fine, and the Express prototype, surprisingly, did not.
Due to weights & balances, engine location & shaft angle, SOMETHING went awry and she ran way too flat.
The powers that be, or were, at the time, had to add some rocker to her.
Think of a straight line--her keelson-- ending with a slight upsweep ending at the transom.
\______________


This allowed some bow-up attitude. Just a little change produced a noticeable result.

If she had had the opposite problem, heading for the moon, they would have contemplated adding some hook.
_________________
/

Talk to someone who ran (still runs?) an old 46 Post. Out of the water, her transom is as sharp as Dick Tracy's chin...flatter than Twiggy,even.
Ask that guy how he handles head seas. He'd tell you how he sticks her nose into it with the tabs to allow Russel Post's forefoot take the bite out.

This famous boatbuilder earlier mentioned (oh, OK, Brand 'B') came out with very few hull designs that hit it perfect, right out of the box, as it were, as told to this writer by it's head engineers and naval architect, over a beer, back in the day.

So, Fortunate One, if your boat is not perfect, do not despair. The hull can be tweaked and/or you can learn how 'ol Bessie wants to be ridden.

[Fortunate One]

Thank you all for replying to the post.

I continue to learn new things from this project.

I hope she has a ride profile like a Rybovich.

This is a once in a lifetime thing and she'll certainly be one of a kind.

I'm ordering the power this week. I've decided to go with the new 720Hp Yanmar 6 cylinders. It will give me enough power and yet be relatively economical on fuel. Plus service is readily available in my area. I’ll have 30” between engines so there will be plenty of room to get around.

The bottom plywood is being installed. She’ll be ready to roll over in 4 weeks and then the real fun begins.

[AMGinfl]

Hi everyone. This post caught my eye as my broker (whom I've been working with for the past year) has also pointed me to take a peak at a 1998 Ocean 45 Super Sport.

Can anyone speak of the ride for this hull as it's deadrise is only 1.5 degress. Any input would be greatly appreciated.

[Ocean48]

Hi,
I have a 1988 Ocean 48 Super Sport with twin 485hp 6-71TI's and it handles rough seas well. We ran the boat from Florida to St.Kitts logging some 1500 miles, and the last leg from Punta Cana DR was smooth until we got south of Puerto Rico where the seas turned very nasty.

The 48ss handled herself well for over 18 hours of heavy head seas.Yes we had some slamming but after slowing down to 12knots the ride was more comfortable. The newer Oceans are even better and have plenty more power and fuel capacity.

[Fortunate One]

Thanks for the response Tony.

How do you find the handling in a following sea?

When you indicate "nasty Seas" are you refering to a tight wave group or large waves?

Thanks

Michael

[Ocean48]

Michael,
As long as the trim tabs are all the way up, the boat handles fine in a following sea.

To answer your second question, I was refering to big waves coming stright at us that was close enough to cause enough slamming to pull screws from the foredeck that held the dingy tie down cables in place.

[SportFishdaze]

Originally Posted by YachtForums

I have the pleasure of watching a wide variety of large sportfish boats running on-plane everyday, as I live near a major inlet that has no speed restrictions.

That's got to be very nice!