Your On-Line Port'o'Call

Previous Thread
Next Thread
Print Thread
Rate This Thread
#526808 - 01/14/12 01:39 AM Hull Designs  
Joined: Nov 2003
Posts: 15,509
GoFirstClass Offline
Retired Boating Bum
GoFirstClass  Offline
Retired Boating Bum
Grand Poobah

Joined: Nov 2003
Posts: 15,509
Pasco, WA
From time to time a question comes up about what makes one boat better than another or what makes one boat more expensive than another. Since most boats in a given size range have similar engines (say from Merc or Volvo) that's not going to make a huge difference, and the instruments tend to be from just a few companies so there's no big difference there.

Part of the difference in price comes from the carpets and vinyls and interior finishings. But also a big difference in price comes from what went into making the hull, and not only the materials that went into the hull and how it was put together, but how much went into the actual design of the hull before the molds were even created.

Here's an example, and I'm not going to mention boat manufacturer names because I don't want to start a "Chevy vs Ford" debate.

When a manufacturer designs a hull there are many parts to the design. The bow entry (narrow vs a wide bow), the design of the chines (soft, rounded, hard, reverse, etc.), the forefoot, the way the hull changes from a very sharp V at the bow to a flatter V at the stern, etc.

One boat maker has, for many years, made boat hulls with a very rounded chine. IMHO part of the reason they do this is it's easier to lay up the fiberglass and resin in a rounded chine mould plus it's easier to get the hull out of a mold when it has rounded chines. That may not sound like a big deal until you're talking an extra day or so in the manufacturing process to work with a hard chine hull compared to the rounded chine, then having to prep the hull for the next boat.

A cottage industry has sprung up that makes additions to the hull to improve the ride. Any boat can ride well in a calm sea, but when you hit a chop get into waves that are in the 4'-8' range and you're in a quartering sea or following sea is where you find out how well a boat rides.

The first two pictures are of a 38' model from this manufacturer and show one modification that has been made to make the boat ride better. A hull extension and swim platform have been added. This creates lift, gives the boat a longer running surface and results in a higher hull speed and planing speed. The company that made this hull extension chose to keep the same chine layout as the boat maker did.

This design does make the boat ride a bit better, but the rounded chines still make for a ride that has a lot of side-to-side rolling action.





Here's another 38' boat from the same manufacturer. This boat has had hull extensions added, but rather than extending the length of the running surface, they added pieces to each side that made a hard chine out of the rounded chine. That has increased the effective running surface without extending the length of the hull.

This design does a better job of controlling the rolling motion of the boat than the first one and provides similar lift and a similar increase in planing speed because of the extra lift.



The downside to both of those types of hull modifications is they're VERY expensive. I think you could figure somewhere north of $25K to have either of them done, and it wouldn't surprise me to see a bill for either of these to run towards $40K.

I couldn't find an example of a hard chine or reverse chine hull in that same length from a manufacturer that produces that type of hull so I'm putting in a pic of my hull. You can see the difference if you look closely at the outside edge of the hull, in the area outboard of the trim tab. My boat has a very slight reverse chine to it, but essentially it's a flat chine design. This provides lift for the hull as it travels at planing speeds, and also slows down the side to side rolling motion of the boat at hull speed or when stopped.


So, in this instance, the lower purchase price of the first two boats has been partially offset by the owners as they tried to improve the ride.

So this is just one thing to keep in mind and look for when you go boat shopping. Narrow boats tend to rock more than boats with a wider beam, but also boats with a rounded chine or soft chine tend to rock more than boats with a reverse chine.

Questions? pc


"Beachcomber" 1995 Sea Ray 550 Sedan Bridge


Anchor's down......Bottoms Up!
#526811 - 01/14/12 02:58 AM Re: Hull Designs [Re: GoFirstClass]  
Joined: Jul 2009
Posts: 744
SALTY_DAWG Offline
Admiral
SALTY_DAWG  Offline
Admiral

Joined: Jul 2009
Posts: 744
Lincolnshire, IL
On smaller boats the chine design has a big effect on how the boat handles in a hard turn at speed. Some hulls are very controllable and predictable and some can be quite surprising.


#526815 - 01/14/12 08:38 AM Re: Hull Designs [Re: GoFirstClass]  
Joined: Jul 2003
Posts: 6,673
Dave R Offline
Admiral
Dave R  Offline
Admiral

Joined: Jul 2003
Posts: 6,673
Raymond NH

It's clear that the owners of the examples shown both had better ride and higher speed in mind when they had the extensions built, but I'd guess the folks with the soft chine extension prefer to spend more time at displacement speeds than the folks with the hard chine extension. I have to wonder if the original hull was too short for its beam right from the start...


"Mischief Managed II"
1992 Tollycraft 44 Cockpit Motor Yacht
Twin CAT 3208TA inboards
#526823 - 01/14/12 12:04 PM Re: Hull Designs [Re: GoFirstClass]  
Joined: Nov 2003
Posts: 15,509
GoFirstClass Offline
Retired Boating Bum
GoFirstClass  Offline
Retired Boating Bum
Grand Poobah

Joined: Nov 2003
Posts: 15,509
Pasco, WA
Salty, you nailed it. A boat that has a soft (or rounded) chine will slide sideways when put into a hard turn at planing speeds. It also will be very tippy at hull speeds or when it's stopped.

Dave, the company that made the first two hulls has been around for a long time and has produced thousands of "bigger boats" (I'll use that term to describe cruiers as opposed to runabouts). Their hulls aren't "overly wide" for the length, they just have chosen to use a very rounded chine.

Your statement about people who buy the soft chine boats desiring to spend more time at hull speeds may be partially true. I think the fact is that most people don't understand how chines work and the effect they can have on how a boat rides. Mosts cruiser buyers look at a few things (interior layout, space, and cost) and don't consider the hull form.

The aftermarket companies that make the hull extensions have attacked the problem from two directions. The first by lengthening the hull, the second by changing the chine form. A person who wants a bit more hull speed and a soft ride might do better for the first type of modification. The owner who wants to run on plane more frequently would probably do better to get the second type where they change the chine form.


I drew up some hull designs and will give a couple of pro's and cons to them.



A. Flat Bottom. Usually found on small fishing boats
pro--great in shallow water, very stable when stopped or at slow speeds, turns well
con--noisy at planing speeds, hard ride in any chop
B. Rounded (or soft) Chine with flat bottom.
pro--quiet, soft ride
con--tippy at all speeds, slides in a turn at planing speed, hard ride due to the flat bottom. Tends to slap in a chop.
C. Round Chine with V bottom
pro--better ride than hull B, but handles chop better than B
con--Still very tippy, less flotation at planing speeds than a hard chine.
D. Hard Chine with Deep V Hull
pro--good ride in chop, turns better than a soft chine boat, better flotation than a soft chine boat.
con--the deeper the "V", the more tippy they are when stopped or at hull speeds, they tend to wander at idle speeds
E. Reverse Chine
pro--better floatation at planing speeds, holds better in a turn, more stable when stopped
con--tends to slap more at planing speeds, noisier than a hard chine boat. If the chines extend to near the bow it can be very noisy when stopped due to waves being trapped in the chine.
F. Cathedral Hull--this is the classic Boston Whaler hull.
pro--very stable when stopped or at low speeds
con--hard ride in a chop when at planing speeds

Too get and idea of how a hull rides, picture it moving through the water at planing speeds. We're all familiar with running on plane and seeing the water that squooshes (is that a word???) out to the sides of the boat. The more water that squooshes out to the side, the less flotation there is so the hull rides deeper in the water, and that's less efficient when on plane.

A. A flat bottom boat won't have much water going out the sides at planing speed due to the excellent flotation of the hull.

B & C. A rounded chine boat has quite a bit of water going out to the sides because the hull doesn't have good flotation and rides lower in the water. This is less efficient at planing speeds than a hard chine boat.

D & E. Hard chine and reverse chine boats have better flotation than the rounded chines so they ride higher in the water and have less water going out to the sides. They're more efficient at planing speeds but at the cost of a stiffer ride than a soft chine.

F. This hull has very little water going out to the sides because it gets trapped beneath the hull. That's good for flotation but gives a horrible ride in a chop.

Because of the lower lifing ability of a rounded chine boat and the softer ride they provide, they tend to be better for boats that run at displacement speeds where lift isn't needed.

Questions/comments??? pc


"Beachcomber" 1995 Sea Ray 550 Sedan Bridge


Anchor's down......Bottoms Up!
#526824 - 01/14/12 12:16 PM Re: Hull Designs [Re: GoFirstClass]  
Joined: Sep 2003
Posts: 7,270
MarkHB Offline
Dressed for dinner
MarkHB  Offline
Dressed for dinner
Admiral

Joined: Sep 2003
Posts: 7,270
Norris Lake, TN
I thought of commercial shipping and hull shape and how that relates to fuel economy. Most shipping I have seen out of the water are similar to hull shape "B" with perpendicular sides. I also wonder how much research is currently underway into commercial hull shapes now that these rotton, stickin, thievin oil companies have jacked up the price of oil. w

Last edited by MarkHB; 01/14/12 12:17 PM.

24' Monterey Explorer
Honda PWC
http://www.picturetrail.com/markhb

Golf!! Waste of a good gun range.
#526825 - 01/14/12 12:19 PM Re: Hull Designs [Re: GoFirstClass]  
Joined: Sep 2003
Posts: 7,270
MarkHB Offline
Dressed for dinner
MarkHB  Offline
Dressed for dinner
Admiral

Joined: Sep 2003
Posts: 7,270
Norris Lake, TN
Originally Posted By: GoFirstClass



Now I know those pics you posted sometime ago of Beachcomber underway was pushing so much water. You need to retract the wheels. roflmao


24' Monterey Explorer
Honda PWC
http://www.picturetrail.com/markhb

Golf!! Waste of a good gun range.
#526838 - 01/14/12 04:13 PM Re: Hull Designs [Re: GoFirstClass]  
Joined: Nov 2003
Posts: 15,509
GoFirstClass Offline
Retired Boating Bum
GoFirstClass  Offline
Retired Boating Bum
Grand Poobah

Joined: Nov 2003
Posts: 15,509
Pasco, WA
Dang, I bet that would help the fuel economy, wouldn't it.


"Beachcomber" 1995 Sea Ray 550 Sedan Bridge


Anchor's down......Bottoms Up!
#526865 - 01/15/12 12:56 PM Re: Hull Designs [Re: GoFirstClass]  
Joined: Aug 2011
Posts: 231
smitch466 Offline
Cap'n Smitch
smitch466  Offline
Cap'n Smitch
Vice Admiral

Joined: Aug 2011
Posts: 231
PA
I recently read a good article on hull form, but can't remember whether it was in Yachting, Soundings, or Passagemaker.

In any case, the author covered much of the same information in respect to chines v. displacement v. planing performance. The focus was on companies that are working on combining hull forms. Companies like Beneteau and their Swift Trawler line.

The author also looked at the shape of the bow and stern and their impact on performance. Just as the cross section of the hull from port to starboard has an impact on ride and roll, the cross section from bow to stern has an impact on handling.

As I recall from the article, a more vertical bow and stern may be okay when taking on head seas, and perhaps okay against the beam, but a following sea will make things difficult. The pressure against the stern cannot be dissipated quickly enough and the vertical bow takes more energy to control as it tries to follow the path of least resistance.

It was interesting that in that same magazine there were advertisements from two different yacht companies that have new launches with relatively vertical bows. From what I have been able to find online their stern design looks like a problem too. They are beautiful boats, but there's something to be said for function being more important than form... or is it form over function... confused

By the way, hull form matters in water sports too. It's actually been one of the main factors in our last couple of purchases. Not only does it impact the ride and handling of a boat, hull form also makes a difference in the wake that you get to play in. Or for you skiers... the lack of wake.


Temporarily Boat-less but working to change that status.
#526867 - 01/15/12 01:06 PM Re: Hull Designs [Re: smitch466]  
Joined: Dec 2002
Posts: 12,416
KCook Offline
Admiral
KCook  Offline
Admiral

Joined: Dec 2002
Posts: 12,416
Phoenix
"... vertical bow takes more energy to control as it tries to follow the path of least resistance ..."

Commonly known as "bow steer". Everything about hull design is a compromise.

Kelly Cook

#526903 - 01/16/12 08:55 AM Re: Hull Designs [Re: GoFirstClass]  
Joined: Jul 2003
Posts: 6,673
Dave R Offline
Admiral
Dave R  Offline
Admiral

Joined: Jul 2003
Posts: 6,673
Raymond NH
A few years ago, I read about a new hull design that was very unique. The boat had a very sharp entry and the deadrise flattened toward the middle, went completely flat at some point and then kept warping as it continued aft until it ended in an inverted V. It basically had a single deep V bow and a tunnel hull stern, (or hard inverted chines at the stern that never turned back downward). It was a planing hull that supposedly never squatted and never plowed. The faster the boat went, the higher it came out of the water. The builder planned to experiment with surface piercing propulsion on the boat. Never heard any more about it and wonder what ever happened with the design.

Edit: Found the boat, see: http://www.shannonyachts.com/38ph.html and my post about it from 2005


Last edited by Dave R; 01/16/12 09:03 AM.

"Mischief Managed II"
1992 Tollycraft 44 Cockpit Motor Yacht
Twin CAT 3208TA inboards
#526905 - 01/16/12 11:39 AM Re: Hull Designs [Re: Dave R]  
Joined: Dec 2002
Posts: 12,416
KCook Offline
Admiral
KCook  Offline
Admiral

Joined: Dec 2002
Posts: 12,416
Phoenix
That hull configuration sounds like a modified catamaran, but with a whole lot more wetted surface. Could be a great setup for chop, big sea handling would be interesting.

doubtful

#526910 - 01/16/12 12:59 PM Re: Hull Designs [Re: GoFirstClass]  
Joined: Nov 2003
Posts: 15,509
GoFirstClass Offline
Retired Boating Bum
GoFirstClass  Offline
Retired Boating Bum
Grand Poobah

Joined: Nov 2003
Posts: 15,509
Pasco, WA
Dave, I looked at the Shannon website and interestingly, there are zero pictures of the hull on their site. I'd think they would post numerous pics of something they tout as being so radically different.

I did find a pic in an article listing several reviews of the boat written in 2005 I found when I googled it. This shot of the stern shows what you described. At hull speed it would be quite stable and at planing speed the hull would provide a lot of lift.


It's also interesting that, despite the great reviews in the article, a check of Yachtworld boat listings showed ZERO listings of Shannon power boats made since the late 80's. The reviews in the articles I linked to were all written around 2005, but it appears no boats were made using that hull. There must have been some problems with creating the hull or in the design or performance that caused it to be shelved.

I wonder why. idn


"Beachcomber" 1995 Sea Ray 550 Sedan Bridge


Anchor's down......Bottoms Up!
#526912 - 01/16/12 03:35 PM Re: Hull Designs [Re: GoFirstClass]  
Joined: Aug 2011
Posts: 231
smitch466 Offline
Cap'n Smitch
smitch466  Offline
Cap'n Smitch
Vice Admiral

Joined: Aug 2011
Posts: 231
PA

I believe this is a rendering of a side view of the boat in question.



I agree with GFC though, you would think they would have lots of photos touting this design. But they do have a link kind of hidden at the bottom of the page that discusses their hull design -

http://www.shannonyachts.com/shannon_srd_technology.html


Temporarily Boat-less but working to change that status.
#526913 - 01/16/12 03:55 PM Re: Hull Designs [Re: GoFirstClass]  
Joined: Nov 2003
Posts: 15,509
GoFirstClass Offline
Retired Boating Bum
GoFirstClass  Offline
Retired Boating Bum
Grand Poobah

Joined: Nov 2003
Posts: 15,509
Pasco, WA
I followed that link and then another that was supposed to go to Shannon Yachts brokerage site. I went there and no boats were listed for sale. There was a link to a YachtWorld page, but it went to a web page with a design they haven't used for years.

Let me do some checking and see what I can find.


"Beachcomber" 1995 Sea Ray 550 Sedan Bridge


Anchor's down......Bottoms Up!
#526917 - 01/16/12 06:48 PM Re: Hull Designs [Re: GoFirstClass]  
Joined: Dec 2002
Posts: 12,416
KCook Offline
Admiral
KCook  Offline
Admiral

Joined: Dec 2002
Posts: 12,416
Phoenix
So ... I will quote myself ... "big sea handling would be interesting"

#526922 - 01/16/12 09:18 PM Re: Hull Designs [Re: GoFirstClass]  
Joined: Nov 2003
Posts: 15,509
GoFirstClass Offline
Retired Boating Bum
GoFirstClass  Offline
Retired Boating Bum
Grand Poobah

Joined: Nov 2003
Posts: 15,509
Pasco, WA
Apparently Shannon Yachts is still alive and well in Bristol, RI.

While checking out Shannon I posted a thread on YachtForums, a boating site Kelly and I both belong to. They provided a link to a thread from 2005 that had a very good discussion about the type of hull that Shannon Yachts was working on. If you want to read some very deep material on hull design (OK, that was a bad pun, sorry!) check out the thread linked to below. While you're reading it you'll find a post on there from Kelly.....

http://www.yachtforums.com/forums/technical-discussion/3180-breakthru-hull-design.html


"Beachcomber" 1995 Sea Ray 550 Sedan Bridge


Anchor's down......Bottoms Up!
#526937 - 01/17/12 02:36 AM Re: Hull Designs [Re: GoFirstClass]  
Joined: Dec 2002
Posts: 12,416
KCook Offline
Admiral
KCook  Offline
Admiral

Joined: Dec 2002
Posts: 12,416
Phoenix
Pulled that thread out of the catacombs!


Moderated by  Admin 

Sponsors
New Topics
Want to go for a boat ride?
by GoFirstClass. 07/06/20 04:17 PM
Uninvited Guests
by Dock Holiday. 07/06/20 12:31 PM
Boats Sales In 2020
by Dock Holiday. 07/04/20 04:14 PM
This guy just conviced me to spray---
by Frantically Relaxing. 07/03/20 07:04 PM
RVingABC
by Jack T. 06/29/20 04:27 PM
Expensive day at the lake for someone.
by captkevin. 06/23/20 08:59 AM
Knocking in the outdrive
by WaterWing. 06/16/20 10:28 PM
Tohatsu M40D2 3000 RPM Max
by BCassity. 06/12/20 03:34 PM
Extending Trailer Tongue
by Silverbullet. 06/12/20 02:04 PM
Looking at driveable street rods
by Frantically Relaxing. 06/10/20 01:03 AM
Who's Online Now
0 registered members (), 52 guests, and 3 spiders.
Key: Admin, Global Mod, Mod
Newest Members
FourCs, BlackEyedEd, Two2Fly, RPalmer, BCassity
5524 Registered Users
Forum Statistics
Forums23
Topics37,378
Posts565,225
Members5,525
Most Online252
Aug 5th, 2017
Powered by UBB.threads™ PHP Forum Software 7.6.0