Deadrise ?

[wakeup]

I am about to change my sports boat and I have been studing the specifications of prospective boats. All of them quote a deadrise figure in degrees some between 16 and 22.

Although I've had a boat for the last two years and have picked up much of the jargon along the way I still don't know what dearise is and why it might be important.

The boat I've got at the moment is a 21 ft run around but I intend to buy a bigger boat 28 - 30 ft and I want to make sure I understand the specifications being presented to me by various vendors and what the implications are.

Can anyone help this near novice out with this one. Thanks in advance.

 

[paulineb]

Deadrise is basically the angle that the 'V' bottom of your boat makes with the horizontal. On a boat designed for the sea, deadrise is important if you want to preserve your spine. The nearer the boat is to flat bottomed, then the more it will slam. The greater the deadrise, the more gently she will hit the sea again after taking off from a wave. However, the deeper the 'V', that is the greater the angle of the deadrise, then the more power the boat will need to get up onto the plane. The different shaped angles of the hull also have an impact on accommodation space.


Pxx

 

[boatone]

not just a pretty face then.<BG>.......

TonyR
boatone@boatsontheweb.com
www.boatsonthethames.co.uk

 

[wakeup]

Pauline,

Thanks.

BTW does anyone recommend a sweet spot for this angle on a 28ft + boat?

Thanks again in advance.

 

[tcm]

varies with what you want to do - flat bottomed (small deadrise) for waterskiing on lakes, bigger for the sea, but need more power.

 

[hlb]

Hell Pauline, your not just a prity face.
But will this help with raising the dead and will Viagra help!!
Also on the question of "Bottoms" Is the flat bottom or V bottom best for when coming off the chandelier!!

Haydn

 

[paulineb]

Chandeliers

Haydn, I've tried this many times and I personally think that bare bottomed is best for coming off the chandelier - or even on the chandelier ;-)

Pxx

 

[wakeup]

Basically I am a fair weather boater who sticks to the shoreline and coastal waters.

One of the boats I am considering has a deadrise of 16deg whereas others have a deadrise of 20 degress. Didn't seem like a big difference when I didn't know what it meant!!

Would a boat with a deadrise of 16degress be suitable for coastal waters?

Thanks

 

[hlb]

Re: Chandeliers

Sounds a bit dangerous with all that glass and hot light bulbes. But will give it a try later. Any thoughts about the landing strip??

Haydn

 

[paulineb]

Re: Chandeliers

Yep. The West Ham away kit ;-)

Pxx

 

[byron]

In brief, the more the deadrise the better the ride. Think of a knife, the sharper it is the easier it cuts ;-)

ô¿ô

 

[tcm]

Lots of people are too scared to go on a boat at all, so you may well find yourself wanting to go further out to sea. The bigger-deadrise boat will cut thru waves better.

Exactly what boats have the 16 and 20 degrees? Do tell.

 

[jfm]

Agree all the other posts

But deadrise is rarely constant. It is generally lower closer to transom (except on a few boats, aptly referred to as "constant deadrise"). So you have to look at deadrise along the boat. When you ask about 16 or 20 deg, is that at the bow or the transom? Usually, when no other info is given, it means transom, and the numbers you quote are quite transomish sounding

A serious cigarette type racer would have a deadrise higher than 25, maybe even 30, as far back as the transom. This helps cornering and soft landing off waves, but is more suited to 60mph boating than 20knots. A 20deg deadrise is reasonably sporty for normal boating, and 16deg is getting quite flat, though pretty common in leisure boats. However, that's all rough and ready because the soft-landing off waves depends more on the forward deadrise than the transom deadrise, and we are talking here in transom numbers. You would want 40% ish deadrise right at the bow to have a soft landing off waves

Manufacturers rarely quote bow deadrise, or rate of change of deadrise, so the quoted transom deadrise is all you get written down, and you have to use it as a rough guide

 

[kimhollamby]

Where are they measuring it?

It's not that simple (you knew someone was going to post that).

Depends on where they are measuring the deadrise. If at the transom that would usually indicate sharper sections forward (depending on the hull design). If midships 16 degrees is still not a disaster by any stretch but 20 degrees might be more comfortable in a chop. However, again depends on the design and...

...on the length of the boat. Frankly you cannot beat size and weight for comfort, more often than not. Taking that to extremes some large motor yachts are almost completely flat-bottomed aft but don't usually slam because they don't leave the water. That could start a whole new thread.

Rather than get too fragged by brochure bumph get sea trials on both. If you haven't got a more experienced friend to take with you you'll still be surprised just how much a combination of your tummy and bottom can tell you about how a boat will feel at sea.

Associate Publisher ybw.com websites kim_hollamby@ipcmedia.com

 

[wakeup]

Re: Where are they measuring it?

Well this is the first time i've used the forum and I am increibly impressed that I've received such comprehensive a response.

Thanks to all respondents.

The boats I am looking at are Sealine S28, Fairline Targa 29 and at the cheaper end of the scale a BMB 27 and a Maxum 2700.

If anyone has any experiences of these boats I would really appreciate some feedback. Sorry MBY I would have bought the reports if they exisited

wakeup

 

[jfm]

Re: Targa/ some more questions

Get the Targa imho.

What ages are they, approx? And/or what budget are you sticking to (or trying to stick to, you will of couse exceed it in practice)? Also what location, and have you had boats before?

 

[DepSol]

Re: Where are they measuring it?

wouldnt trust maxum myself, my mates 2300 came apart after 5 weeks the top removed itself from the bottom and maxums warranty wasnt worth much at the end of it.

 

[wakeup]

Re: Targa/ some more questions

trying to stick to sub £70k and i am based in Penarth Marina so we are limited in terms of places to go.

I want to keep it to a single engine to keep the servicing costs down.

I am not a serious boatie, I am definitely a 50 hour a year fair weather costal wimp.

I feel that the targa whilst being with out doubt the best quality , would be seriously over engineered and under utlized.

 

[tcm]

Re: Targa

The targa is also at the very bottom end on the fairline range, so fairly easy peasy for them. They've also stopped making these, and tghey were popular but not as profitable as larger boats, so demnd isn't being satisfied. 50 hours isn't massive, but there are wimpier coastal types, and Cardiff isn't what I'd call wimp waters. The targa should be easier to sell.

Bear in mind also that you ae the ultimate fab buyer at this (and only this) time because a) you haven't got a part exchange b) you aren't too picky, esp if planning on 50hrs per year and of course c) you have got the loot.

So this transalates into fat discount. if it's up for 80k, 70k will easily buy it, and praps some morring fees and a day of a bloke on board showing you whats what and going out and even (gasp) gettem to fiit an automatic bilge pump under the saloon floor somewhere, which we have found out isn't standard, there's only one in the engine compartment. Bilge pumps automatically pump out any water, useful if a fitting gives way and the boat springs a leak.

 

[wakeup]

Re: Targa

Thanks tcm.

You obviously know a bit about fairlines.

How do you think the targa 29 compares to the 30 with its new layout and engine access but less space in the cockpit? Is it worht the extra money or is it less practical?