Deadrise

[MedDreamer]

I know everything in boat design is a compromise but what do you consider to be the optimum deadrise for a planing boat 26-36 feet. My 2855 spec show 21 degrees and compared to my old 2655 (18 degrees I think) it really cuts through rough water much better but I suppose the payoff is that it takes more power to get it up because the bottom is not as flat. (scope for a martynwhiteley type headline there).

I do not have a wide range of experience of how different boats ride but watching some larger "better quality" boats bouncing on the lake I am more than happy with my boats performance.

Do boats with smaller angles slam more?

Finally is there a key on my keyboard to show the degrees symbol? I cant find one.



<hr width=100% size=1>Martyn

 

[Questor]

Re: Degrees

Re the degree symbol, do you mean this one ° , as in 20°C

It's got to be there somewhere!!

R



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[MedDreamer]

Re: Degrees

Yes but I can't find it - where is it on your keyboard?

<hr width=100% size=1>Martyn

 

[Deleted User YDKXO]

Depends where you measure it. Most planing boats have variable deadrise (sometimes known as a 'warped bottom'), varying from maybe 45deg at the bow to maybe 20deg at the stern, the deadrise being flatter at the stern to give lift for efficient planing. More sporty boats have a constant deadrise (eg. some Sunseekers) such that the deadrise at the bow is the same as at the stern. This gives better rough water capability but needs nore power for planing. Deadrise isnt the whole story for rough water capability as spray rail/chine design, weight distribution and waterline length also have an effect
When manufacturers quote deadrise, normally they are quoting deadrise at the stern which is probably the case with your Bayliner and, obviously, a boat with 21deg deadrise will cut through the waves better than one with 18deg deadrise, all other things being equal
A deadrise of 18-20deg at the stern is typical for most variable deadrise planing cruisers

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[gjgm]

well, you first need to define the intended use of the boat. If its a racing powerboat you are after that will have to cope with top performance in tough sea conditions, or a comfortable cruiser where you are unlikely to risk damaging that precious plasma screen. The boats you mention might be bouncing more to to loading and/or incorrect trim, as much as hull design. Wouldnt say the deadrise is the only aspect of hull design that matters;more a question of balancing all the hull design aspects.

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[MedDreamer]

Fair point, I suppose I am thinking of comfortable cruising.

<hr width=100% size=1>Martyn

 

[martynwhiteley]

The Best Angle for your Bottom

To ensure a smooth passage!




'That good enough Mart ! /forums/images/icons/wink.gif

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[Questor]

Re: Degrees

Martin

Stop looking for it, as it's not there. There are many different symbols available by using the numbers keypad on the right of your keyboard. Mainly used by programmers.

The way to get the degree sign as in 20° is by:

1) turn on number lock
2) press and hold "Alt" key
3) then press 0 1 7 6
4) release the "Alt" key and there it is. Problem solved.

Next thing you'll want to know how to do a ±, or a Ý or a ╚ or even a ñ !!

Richard


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[MedDreamer]

The Best Angle for your Bottom

You really really really do not have enough work to do!!!

I think we should have a Christmas competition for the most "Carry On" post title to appear in the YBW home page summary.

In fact rather than a panto we should have a "Carry On" story this xmas., time to start thinking who's going to be the Kenneth Williams character etc. We already have the Sid James (ccscott49).

"Carry On Christmas Cruising" will do I think. I will make a diary reminder to kick it of mid December.

<hr width=100% size=1>Martyn

 

[martynwhiteley]

Not enough to do

You must have been talking to my MD Martyn!

We had our management 'restructure' meeting for 2004 yesterday, and I now manage 3 divisions not 2.

But the good news is, the new division 'Mechanical Engineering Services' includes the machine shop, very useful for making/repairing boat parts, and they have all the dynamical balancing/laser alignment stuff, so when we fit that diesel in your boat, you can count on low vibrations.

My existing two divisions are; 'Electrical & Instrumentation', and 'Leak Repairs UK'.

E&I have already rewired my shore power with new RCD's etc. Fortunately not needed the services of 'Leak Repairs' yet, but trying to avoid all the fridges and gas bottles when I come up the Ouse in a couple of weeks may change that!

Guess you don't find too many mwave filters in your binliner. Still, at least you can add up all the cost of your fuel on your company accounts package!


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[Kevin]

Hi

The hull shape at the bow also hugely affects ride and performance, it is especially, at lower speeds, the first point of contact with the water as the boat moves forward if the shaping is wrong no amount of deadrise angle will wholly compensate.

true offshore boats will have a shallow curving- back -of -the- hull at the bow as opposed to sweeping back early from above waterlevel this sets up the movement of water that will pass over the rest of the hull, most true performance boats wouldnt have a deadrise much below 24 degrees in my experience.

The problem with a large degree of deadrise is that unless you are prepared to have a larger draft the boats beam will normally have to be narrower which if on a cruiser isnt whats really wanted as space onboard is an important factor so I suppose most manufacturers compromise on performance, room and ride.

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[coombm]

Is this why the Doral 250 is quoted as 18 / 14 degrees?

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[Deleted User YDKXO]

Thats odd, because the deadrise at the bow should be a lot more than 18deg and 14deg sounds a bit low for the stern, especially on a sports cruiser. Best to ask the dealer

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