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 What is deadrise and what does it mean?
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Billylll

RO# 24494



Posted - Dec 18 2009 :  22:11:39  Show Profile  Reply with Quote
I know this is probably a silly question but what is deadrise in a boat and what is the effect of say a low number compared to a higher number? My boat has an 18 degree deadrise.
Bill
WIRELESS ONE,
36 Gulfstar
Trawler
Little Egg, N.J.

Homeport: Tuckerton, N.J.

Capt. Bill1

RO# 2017

Posted - Dec 18 2009 :  22:20:10  Show Profile  Reply with Quote
A simple answer would be, the more deadrise or angle carried aft the smoother the ride in a chop or rough sea.

The less deadrise carried aft, or the flatter the aft section of the hull, the less horse power it takes to plane off the boat and the more stable (or less tender) it would be at anchor.



Homeport: Sarasota/Ft. Lauderdale Go to Top of Page

Grady Wahoo

RO# 16408

Posted - Dec 18 2009 :  22:22:46  Show Profile  Reply with Quote
The measurement of the angle between the bottom of a boat and its widest beam. A vessel with a 0 deadrise has a flat bottom, high numbers indicate deep V shaped hulls.

Obviously a flat bottom won't "cut" through the water at all, I think the original Ray Hunt "deep V" was around 25 degrees, my 35 Bertram's around 18 degree's, and considered a "deep V" by some. I would have guessed the Mainship was a little less, I'll assume you don't have the "trawler" model.


Mike
1971 35' Bertram Caribe
"Black Bart"

Homeport: .Salem, MA Go to Top of Page

Billylll

RO# 24494



Posted - Dec 18 2009 :  23:17:14  Show Profile  Reply with Quote
Nope a Sedan Bridge. My aft section about 1/3 of the boat is almost flat the other 2/3rds transition into a deep Vee 18% degrees is what the specs say on the brochure.
Bill


WIRELESS ONE,
36 Gulfstar
Trawler
Little Egg, N.J.

Homeport: Tuckerton, N.J. Go to Top of Page

Ghost

RO# 689



Posted - Dec 19 2009 :  02:38:49  Show Profile  Reply with Quote
Bill, true hull deadrise is measured at the stern. A lot of people like to look at the pointy end of the boat and proclaim about how much of a "deep v" it is. That's just not correct. That's what you call a fine entry and while important, is not correctly referred to as deadrise.

To really learn about deadrise, look up the story of Richard Bertram and his foray into what at the time was revolutionary in a planing powerboat design. He carried the V of the hull all the way to the stern, and not just a little either it was a "deep V". Today we call anything approximately 18 degrees or so and greater to be a deep v hull. That kind of V allows the boat to really carve through waves that usually make a planing boat have to slow down to keep from pounding. It's what allowed Richard Bertram to win races and build a market niche of boats that gained a reputation of going out on days everyone else was running for cover.

But as with a lot of boat spec's, if you want to know your deadrise, you likely have to go measure it with a compass yourself. On boats 40 foot and greater, you don't usually see a deep v. Oh sure, there are sportfish battlewagons that have it, but while it makes for a nice cut through the waves, it also tends to make the boat roll more and consumes a lot more energy and fuel to push that through the water. My old twin diesel 28 had 18 degrees of deadrise and I would get a kick of carrying 22 knots in 4 footers. Not something I want on the 48, but I can still appreciate it.

Again, the correct measurement is at the stern.


What part of GALE WARNING did you not understand?

Homeport: Everett Wa Go to Top of Page

MikeeH

RO# 6342



Posted - Dec 19 2009 :  05:57:54  Show Profile  Reply with Quote
Capt. Bill and Ghost have pretty much nailed it. Our Carver 3257 had near no dead rise and was super stable at anchor. I used to love blowing by my buddy with his Sea Ray 310 when the water was flat... typical SR guy he could never figure our how a boat with the same LOA but a larger beam and the same power such as our Carver would blow his shorts off. When the water was rough or if I was in his wake there was no way I could keep up because we'd bang in the chop or if a wake hit us at all near beam on it would actually push and roll us around.

Like everything else on a boat, the amount of or lack of deadrise brings compromises.


Mike

I recently realized that at this stage of my life I'm now wise enough to know better, but old enough not to give a damn.

Homeport: Still Pond, MD Go to Top of Page

pdecat

RO# 842



Posted - Dec 19 2009 :  08:55:21  Show Profile  Reply with Quote
It' not simple Billy, Most modern boats have been built with variable dead rise. Sharp entry gradually flattening to very shallow at the transom. Flatter shapes create more lift so boat designers have been using sharp entry to part waves and flatter sterns for lift. Carrying deep V all the way aft probably adds unnecessarily to drag while offering little in rough water ride since the stern is rarely breaking waves.

Flatter sections aft produces a more level running attitude where as deep aft sections produced bow high running. Tunnels decrease lift aft as well which accounts for the reputation of many sea rays as wakemekers. Another aspect of sea keeping design is a deep forefoot. Pointy bows may look nice but how far forward the bow is carried under water is important for better ride.

Flatter bottoms require less fuel to maintain speed on plane. Like everything else bottom shape is a compromise that designers have been debating forever.

Where to measure deadrise on a variable form hull is an open question.



Bruce



Edited by - pdecat on Dec 19 2009 08:59:02

Homeport: Gulf Coast FL Go to Top of Page

Silver Lining

RO# 29390



Posted - Dec 19 2009 :  09:59:51  Show Profile  Reply with Quote
Bill the comments covered deadrise pretty well. I would second the importance of the forefoot. The deadrise aft at the transom helps the boat track well and does have some effect on the ride in rougher water. But the forefoot (2/3 to 3/4 forward) really has the most affect on how the boat rides in a head sea. When we bought our Viking I spent a lot of time studying this and measured lots of boats with an angle gauge because I really wanted a boat that would expand our weather window. Almost all of the boats carry the transom deadrise constant to about 2/3 forward. Some like the Regal have two angles at the stern, or a flat section right at the keel. Also a hard chine or a reverse chine has a big effect on both hydrdynamic lift and stability at speed.

Our Viking Sport Cruiser has an 18 or 19 degree deadrise aft but 28 to 30 degrees in the forefoot with a 45 to 48 degree entry. Similar numbers to a sport fish so we can go 22 knts in steeper 3 footers without pounding but the converse is the fuel mileage is not as good. The other noticeable effect when we sea trialed a few boats in the 40 to 50 foot range was that the flatter the deadrise aft, the worse the boats track. The nice deep vee boats at WOT are surprisingly responsive at full lock, they dont feel like they are slipping. While our 50 foot Viking is great in rougher conditions and handles very well, it does roll more to a beam sea at anchor although is very stable at speed as a result of the hard chines. We also get OK fuel mileage (not as bad as a sport fish because they tend to have huge engines weigh more).


-Rick

Viking Sport Cruiser 50FY
"Silver Lining"

Homeport: Chesapeake, MD Go to Top of Page

HOGAN

RO# 3813



Posted - Dec 19 2009 :  10:10:43  Show Profile  Reply with Quote
Why do the call it "deadrise"?

_________________________


1999 Trojan 440 Express
2005 Scout 175 Sportfish
Achilles LEX 96
MMSI# 338049724




Surly to bed, surly to rise...

Homeport: SS3 @ PennyBridge Marina, Stony Point, NY Go to Top of Page

Capt. Art

RO# 25924

Posted - Dec 19 2009 :  10:11:33  Show Profile  Reply with Quote
While on the topic how does the stepping of the hull help the boat plane? They always look like a strange place to make cuts into the hull?


Homeport: Staten Island, NY Go to Top of Page

pdecat

RO# 842



Posted - Dec 19 2009 :  10:25:25  Show Profile  Reply with Quote
Here are some PIX of forefoot to stern with a lot of transition and a stern with both some V for tracking and flat sections for lift. The stepped chines increase roll resistance at rest but are up out of the water at speed for less drag.














Bruce



Edited by - pdecat on Dec 19 2009 12:52:09

Homeport: Gulf Coast FL Go to Top of Page

unkle buck

RO# 19709

Posted - Dec 19 2009 :  12:47:00  Show Profile  Reply with Quote
nice job of edumacating me on this...thanks...some pictures of the butt and front end of my boat (while being surveyed). No clue what was going on with the design of this hull, but it rides nice enuff for me. Caught in some 6-9s head seas around Cape Canerval a few years back, had to slow to 11k but made it ok







John

68 Lazzara

Homeport: Go to Top of Page

Billylll

RO# 24494



Posted - Dec 19 2009 :  13:09:36  Show Profile  Reply with Quote
In the rear under the cockpit where then engines are think of a almost flat bottomed box but where the trim tabs are it comes up verticle almost 18" at a 90 degree angle then there is a slight rake to the sidewall of the boat from there but very little probably 24" each side and the boat has a 13'6" beam. Now from the Salon forward the V continues growing to the front of the boat.
I have the original cut sheets and advertising for the boat and even Mainship's current board if you go to older models click on 1993-1999 40 Sedan Bridge and it says 18 degrees deadrise. I have no prop pockets and I assume the aft box with the 90 degree verticle before it is almost straight again is where the props sit. I fact I know that is where the props sit but because of the prop size the bottom part of the hulls aft box does not protect the props. The boat is very stable in wind and doesn't rock much at anchor or slow cruising hul speeds on plane she handles very well and most spray in rough water is pushed away from the topsides by the front V. Since I can't post pictures here I'm trying to draw a mental picture and I am probably doing a poor job of it. But thanks for all the explenations.
Bill


WIRELESS ONE,
36 Gulfstar
Trawler
Little Egg, N.J.

Homeport: Tuckerton, N.J. Go to Top of Page

Billylll

RO# 24494



Posted - Dec 19 2009 :  13:15:52  Show Profile  Reply with Quote
Bruce your pictures look similar to my hull almost flat at the aft. Prop position is similar.

WIRELESS ONE,
36 Gulfstar
Trawler
Little Egg, N.J.

Homeport: Tuckerton, N.J. Go to Top of Page

Maycpa

RO# 3197

Posted - Dec 19 2009 :  13:18:57  Show Profile  Reply with Quote
goto wikipedia and lookup deadrise.

Arnold May
"After Taxes"
2001 Silverton 453
USCG 50ton Master License

Homeport: Ottawa, IL Go to Top of Page

Hyperfishing

RO# 3223

Posted - Dec 19 2009 :  13:21:00  Show Profile  Reply with Quote
Proper steps in a high performance speedboat hull, "inject" air under the hull to decrease water resistance. The steps also decrease effective water resistance as they break up the effective planing surface. Float planes have had steps on their floats for many years, as it is easier for them to break free of the water surface tension.

Stepped hull speedboats are definately faster, but many of these boats tend to slide around, are tricky to drive, and can spin out in a fast turn.

Some manufacturers do steps better than others. Outerlimits are the tops, and their 42 foot V hulls commonly do over 160 MPH. Impossible to attain these speeds without step introduced air under the hull.


Chris

Homeport: Sand Bar, Great South Bay Go to Top of Page

MikeeH

RO# 6342



Posted - Dec 19 2009 :  16:50:03  Show Profile  Reply with Quote
Uncle Buck,

Prop pockets. My Silverton had a similar hull with prop pockets. They have a couple of functions. First, they reduce the angle of the shaft so the prop thrust is more direct than a boat with a more severe shaft angle. Second, they reduce the overall draft of the boat as the props are not extending as far below the hull. Not sure what the downside is but I'm sure there is one..... its a boat so there's always compromises.


Mike

I recently realized that at this stage of my life I'm now wise enough to know better, but old enough not to give a damn.

Homeport: Still Pond, MD Go to Top of Page

pdecat

RO# 842



Posted - Dec 19 2009 :  17:10:22  Show Profile  Reply with Quote

Mike:
They are also supposed to increase prop efficiency. The downside is less maneuverability when docking and less lift aft.



Bruce



Homeport: Gulf Coast FL Go to Top of Page

btoran

RO# 19401

Posted - Dec 19 2009 :  18:38:24  Show Profile  Reply with Quote
deadrise is what happens with zombies if you don't bury them deep enough.

Bruce Toran
1996 Carver 320 Voyager
-------------------------
"Don't Eat Anything Bigger Than Your Head"


Homeport: Northport, NY Go to Top of Page

Capt. Bill1

RO# 2017

Posted - Dec 19 2009 :  19:39:40  Show Profile  Reply with Quote
quote:
Originally posted by HOGAN

Why do the call it "deadrise"?



My guess is as you go up from dead flat the angle rises.



Homeport: Sarasota/Ft. Lauderdale Go to Top of Page

PascalG

RO# 12212



Posted - Dec 19 2009 :  20:13:24  Show Profile  Reply with Quote
the downside of pockets can be less maneuvrability and some wandering at low speed.

Charmer has no pockets... the boat handles like a dream, I can litteraly move the bow or the stern jsut a few inches if i need with incredible precision, which I need coming back in the slip here since i have a few inches clearance altogether. She tracks extremely well too, requiring very little steering input. despite having a fairly flat aft section.

on the other hand, fully loaded, i have to deal with a 6 1/4 to 6 1/2 draft.

My old Jack Hargrave designed 53' Hatteras hull on the other hand is also pretty flat aft but has a keel. Props are protected, 4' draft and the boat tracks and handles very well.

i took these picture last year, Charmer on the right, a late model Hatteras on the left. huge difference in hull design and performance. the hatt probably tops aroudn 22kts, vs 30kts, but cut thru the chop like it's not even there. See how the props are protected by the keel in the second picture...






Pascal
1970 Hatteras 53 MY
26' Starfish sloop
12' Westphal Catboat
16' Hobie Cat
13' Sandbarhopper

Homeport: Miami, FL Go to Top of Page

Capt. Bill1

RO# 2017

Posted - Dec 19 2009 :  21:26:13  Show Profile  Reply with Quote
Yeah that is flat. No wonder it's so fast. And it must be stable at anchor as well. But not much fun in a head sea or a steep chop.

I've been meaning to ask you, everything I've read in the passed about the 70' Johnson's mentions either a 5' or a 5'1/2" draft. Did you or the PO add something to it that increased it's weight that make it draw more? Or do you just add a foot or so for a fudge factor?



Homeport: Sarasota/Ft. Lauderdale Go to Top of Page

walterv

RO# 12640



Posted - Dec 19 2009 :  21:35:11  Show Profile  Reply with Quote
Why you asking Bill?

And always remember, life is not measured by the number of breaths we take, but by those moments that take our breath away.

George Carlin

Homeport: Go to Top of Page

Capt. Bill1

RO# 2017

Posted - Dec 19 2009 :  21:47:17  Show Profile  Reply with Quote
Because like I said, everything seems to say 5' to 5' 5" so I was wondering what was different about "Charmer".

Of course the 5' to 5' 5" numbers could come from the manufacturer when the boat is light. And used to make it look like a better boat for use in shallow water cruising areas like in the Bahamas.


Since you are not Pascal, why do you care what I ask him?




Edited by - Capt. Bill1 on Dec 20 2009 07:19:18

Homeport: Sarasota/Ft. Lauderdale Go to Top of Page

tugboat kevin

RO# 24998

Posted - Dec 20 2009 :  08:06:53  Show Profile  Reply with Quote
There are many variations of bottoms kinda like women all perform different(some drasticaly) it really depends on what you do with the boat most of the time, and its very true you can,t have everything i think one classic design thats great at slow speeds yet planes easy can be driven on one engine(12inch keel) has very shallow shaft angle yet jumps up on plane is the old egg harbor bottom the 33 we have with 19,000 hrs still amazes me a lot of newer stepped hiney heavy bubble or nike boats perform terrible till you get them up to a speed where the steps work. after thinking on this i think its easier to compare females if you are allowed too! now what bottom is the redhead or blonde or oriental or swedish or spanish can,t forget those brazilian's from south beach! now theres a bottom....


Homeport: oswego ny Go to Top of Page

HOGAN

RO# 3813



Posted - Dec 20 2009 :  08:15:05  Show Profile  Reply with Quote
quote:
Originally posted by Capt. Bill1




Since you are not Pascal, why do you care what I ask him?





Wow, somebody got up on the wrong side of the boat today!

Perhaps Walter was curious?


_________________________


1999 Trojan 440 Express
2005 Scout 175 Sportfish
Achilles LEX 96
MMSI# 338049724




Surly to bed, surly to rise...

Homeport: SS3 @ PennyBridge Marina, Stony Point, NY Go to Top of Page

PascalG

RO# 12212



Posted - Dec 20 2009 :  08:27:07  Show Profile  Reply with Quote
ROFL! nothing wrong with the question.

everytime the boat is out of the water, I look at the draft again, hoping it's not 6'+... it's not. Charmer is a little heavier since we have a Jetski on board, plus the 15' RIB. Plus 16 golf cart batteries for the inverter bank.

5 1/2 is probably the draft for a standard J70, with light fuel. fully loaded, we're at a solid 6 1/4. In fact when we do the bottom paint in the spring, i'm going to have them raise the line a little higher to keep it cleaner.

the draft listed in teh manual is 1.7m which is about 5' 9" I know from looking at the WL that light to full fuel adds about 3"... figures the inverter bank adds an inch, same for the PWC...



Pascal
1970 Hatteras 53 MY
26' Starfish sloop
12' Westphal Catboat
16' Hobie Cat
13' Sandbarhopper

Homeport: Miami, FL Go to Top of Page

pdecat

RO# 842



Posted - Dec 20 2009 :  09:57:51  Show Profile  Reply with Quote
As Kevin points out weight distribution is as important as hull shape. Those wakemaker sea rays with prop pockets frequently have V drives placing all the weight far aft where the flotation and lift is reduced because of pockets. Is there any wonder why they dont steer well off plane and make big wakes??

I wish I could see the botoms better in Pascals PIX.



Bruce



Homeport: Gulf Coast FL Go to Top of Page

Capt. Bill1

RO# 2017

Posted - Dec 20 2009 :  13:08:11  Show Profile  Reply with Quote
quote:
Originally posted by HOGAN

quote:
Originally posted by Capt. Bill1




Since you are not Pascal, why do you care what I ask him?





Wow, somebody got up on the wrong side of the boat today!

Perhaps Walter was curious?




You're right. Actually I've been getting up to early and going to bed too late for the passed few weeks.

So sorry Walter if I miss read your tone.

Thanks Pascal. I forgot about the big battery bank and the ski. At least the batteries add weight down low.

We draw 6' - 6'6" as well. Which as you know is perfectly doable in the Bahamas. But does limit you to anchoring farther off some of the coves and beaches there.

Have you been into Compass Key Marina lately? I was thinking of going in this trip but I'm not sure if the channel in can still carry 6'+ even at high tide any more.




Homeport: Sarasota/Ft. Lauderdale Go to Top of Page

PascalG

RO# 12212



Posted - Dec 20 2009 :  13:23:41  Show Profile  Reply with Quote
nope, we might on this trip. if so, i may anchor out and run the channel with the tender first to see what they really have.

Bahamas are ok, the keys is were anything over 5' really kills you since it puts most of florida bay out of reach...

bruce, i'll try to post more later on, i have to resize/upload them first, busy getting ready today...



Pascal
1970 Hatteras 53 MY
26' Starfish sloop
12' Westphal Catboat
16' Hobie Cat
13' Sandbarhopper

Homeport: Miami, FL Go to Top of Page

Capt. Bill1

RO# 2017

Posted - Dec 20 2009 :  15:07:08  Show Profile  Reply with Quote
"nope, we might on this trip. if so, i may anchor out and run the channel with the tender first to see what they really have."

Yeah, I've never gone in with anything that draws over 6'. They dug the channel out a few years back as I recall. But I'm not sure if they maintained it in any way. They will, or at least used to, come out and lead you in if you draw a lot of water. Once you're in it's plenty deep. Great beach on the sound side of the island.

Keep an eye out if you go into Sampson as well. Last time I was there the channel in had move to the North.



Homeport: Sarasota/Ft. Lauderdale Go to Top of Page

walterv

RO# 12640



Posted - Dec 20 2009 :  16:50:44  Show Profile  Reply with Quote
Bill 1
Actually my question was directed to BillyIII, are posts were 9 seconds apart, so I was still typing when you posted. The reason I asked Billy III the question was I was feeling he is on the hunt for another boat.

Walter


And always remember, life is not measured by the number of breaths we take, but by those moments that take our breath away.

George Carlin

Homeport: Go to Top of Page

walterv

RO# 12640



Posted - Dec 20 2009 :  16:53:53  Show Profile  Reply with Quote
PS, Bill 1

No problem, I have very thick skin. :)


And always remember, life is not measured by the number of breaths we take, but by those moments that take our breath away.

George Carlin

Homeport: Go to Top of Page

Capt. Bill1

RO# 2017

Posted - Dec 21 2009 :  12:29:39  Show Profile  Reply with Quote
quote:
Originally posted by walterv

PS, Bill 1

No problem, I have very thick skin. :)



Again sorry to be snippy. And Merry Christmas.



Homeport: Sarasota/Ft. Lauderdale Go to Top of Page
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