Boat Design Forums  |  Boat Design Directory  |  Boat Design Gallery  |  Boat Design Book Store  |  Thanks to Our Site Sponsors

Go Back   Boat Design Forums > Design > Boat Design
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read Most Recent Posts Gallery Images Search

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 08-26-2005, 01:20 AM
TinyMan TinyMan is offline
Junior Member
 
Join Date: Aug 2005
Rep: 10 Posts: 4
Location: Pacific Northwest
Long skinny boats

Hello everyone, first time poster here. I have been reading these forums for a while and wanted to see what everyone thought about my personal crazy idea.

Would it be possible to build in steel a very long and skinny boat. I am thinking something like 82" long yet only 10-12" wide. I am fascinated by the high efficiency of displacement speed boats, and want to push the limits a bit.

I'm hoping that with a long waterline and very lean shape, it will be possible to push the boat to 1.5+ X displacement speed with very little power (200hp?)

So, what is wrong with my plan, and why don't I ever see boats designed like this. Stability was a concern of mine, but with 6' of draft and a very heavy keel/ballast, I would think that this shape has immense reserve stability. The rounded bottom might make for more overall roll, but it should be controlled. or will it?

My dream is to design a boat that can be cheaply constructed that will allow me to circle the globe, all while achieving good economy all around.

I've attached an image which highlights a design that I am considering.
Attached Thumbnails
Long skinny boats-long_skinny.gif  
Reply With Quote


  #2  
Old 08-26-2005, 11:49 AM
water addict water addict is offline
Naval Architect
 
Join Date: Jun 2004
Rep: 73 Posts: 313
Location: maryland
Quote:
Originally Posted by TinyMan
Hello everyone, first time poster here. I have been reading these forums for a while and wanted to see what everyone thought about my personal crazy idea.

Would it be possible to build in steel a very long and skinny boat. I am thinking something like 82" long yet only 10-12" wide. I am fascinated by the high efficiency of displacement speed boats, and want to push the limits a bit.

I'm hoping that with a long waterline and very lean shape, it will be possible to push the boat to 1.5+ X displacement speed with very little power (200hp?)

So, what is wrong with my plan, and why don't I ever see boats designed like this. Stability was a concern of mine, but with 6' of draft and a very heavy keel/ballast, I would think that this shape has immense reserve stability. The rounded bottom might make for more overall roll, but it should be controlled. or will it?

My dream is to design a boat that can be cheaply constructed that will allow me to circle the globe, all while achieving good economy all around.

I've attached an image which highlights a design that I am considering.
Your ideas aren't out of the ballpark, but your speed/power will likely not make it. Some naval combatants have geometries typical of what you are talking about. You can look on the federation of american scientists web site http://www.fas.org/man/dod-101/sys/ship/ where they have concise lists of navy ship dimensions. You can scale the ratios of L-B-T and displacement as well as speed and power to see what your design might be able to acheive.

For geometrically similar hull forms, L-B-T all scale as the ratio of Lm/Lp.
Power scales as (Lm/Lp)^(3.5). Speed scales as (Lm/Lp)^(0.5). This will not be exact, but will get you close.
Reply With Quote
  #3  
Old 09-24-2005, 07:49 AM
Bergalia's Avatar
Bergalia Bergalia is offline
Senior Member
 
Join Date: Aug 2005
Rep: 254 Posts: 2,517
Location: NSW Australia
Long skinny boats

I think the first question is, TinyMan - why a long skinny boat ?
For well over 3,000 years we've been taking to sea in short fat boats...Why are you trying to 'buck the tide' ?
I also assume that you mean a boat 82 FEET long - not 82"(inches) by ten to twelve FEET wide and not 10-12" (inches wide).
And while Water Addict's note on naval ship displacements may be valid for the US navy (a young service with much learn) the Royal Navy is seriously searching the efficiency virtues of shorter fatter vessels.
Reply With Quote
  #4  
Old 09-24-2005, 04:32 PM
marshmat's Avatar
marshmat marshmat is offline
Senior Member
 
Join Date: Apr 2005
Rep: 2008 Posts: 4,132
Location: Ontario
I personally agree with the long skinny boat idea. I do think that attempting to push the hull beyond its natural hull speed will not work too well; speed/length ratio of 1.34 would be its natural preference but to get over 1.5 would require disgustingly huge motors.
TinyMan- It's an interesting direction you're taking there; I would go for more rounded sections and fewer sharp corners below waterline. I like to think of such a hull as a series of foil sections revolved around the boat's longitudinal axis; this might be an interesting way to visualize your hull. I honestly don't see a huge advantage to short and fat except for marina fees (I'd sooner have 80'x12' than 60'x16' for the same deck area).
Reply With Quote
  #5  
Old 09-25-2005, 06:15 AM
FAST FRED FAST FRED is offline
Senior Member
 
Join Date: Oct 2002
Rep: 925 Posts: 3,997
Location: Conn in summers , Ortona FL in winter , with big dock & room for O'nite stop .
"I do think that attempting to push the hull beyond its natural hull speed will not work too well; speed/length ratio of 1.34 would be its natural preference but to get over 1.5 would require disgustingly huge motors."

That 1.34 is for fat piggy boats that are 3 or 4 times as long as they are wide.

Once the L/B ratio gets to 8-1 (or better) "Hull Speed" is probably closer to 1.8 times the LWL ,
so easy fast cruising , with out hundreds of HP are feasable.

There was another Long Skinney Boats thread about a year ago that has some fine ideas and concepts.

The real question is stability , should it be done with depth and a keel , or with small Ammas (trimiran floats).

My opinion is the Tri would be better as their far easier in rolly harbor conditions , and the vessel could be lighter with no weighted keel.

Some stability for sails is needed as their far easier to use as a "get Home" than spare engines , gensets with hyd shaft coupling or the other systems.

While its not a cruising requirement, the TOP speed of a LSB would be higher if the hull was as light as can be.

Not EZ to do when 2000 to 4000 G of fuel needs a home , but still a thought.


With shallow draft the Bottom of the boat would be better if heavy enough to stand repeated groundings, there is seldom space for 65 to 85 ft boats in many harbors , but if you only draw 3 ft and can take the ground , there would be little competition for your mooring area.

FAST FRED
Reply With Quote
  #6  
Old 09-25-2005, 12:01 PM
fcfc fcfc is offline
Senior Member
 
Join Date: Feb 2005
Rep: 399 Posts: 744
Location: france,europe
See http://www.dieselducks.com/ellemaid.html
or http://www.gerrmarine.com/images/boa...66voyagerB.GIF

Also, going higher than 1.3 has a big efficiency penalty ,even for a 1:12 B:LWL boat. with a D/L ratio of 20.
http://www.sname.org/newsletter/Savitskyreport.pdf
Reply With Quote
  #7  
Old 09-25-2005, 02:16 PM
Leo Lazauskas's Avatar
Leo Lazauskas Leo Lazauskas is offline
Senior Member
 
Join Date: Jan 2002
Rep: 2122 Posts: 2,465
Location: Adelaide, South Australia
Quote:
Originally Posted by TinyMan
Hello everyone, first time poster here. I have been reading these forums for a while and wanted to see what everyone thought about my personal crazy idea.

Would it be possible to build in steel a very long and skinny boat. I am thinking something like 82" long yet only 10-12" wide. I am fascinated by the high efficiency of displacement speed boats, and want to push the limits a bit.

I'm hoping that with a long waterline and very lean shape, it will be possible to push the boat to 1.5+ X displacement speed with very little power (200hp?)

So, what is wrong with my plan, and why don't I ever see boats designed like this. Stability was a concern of mine, but with 6' of draft and a very heavy keel/ballast, I would think that this shape has immense reserve stability. The rounded bottom might make for more overall roll, but it should be controlled. or will it?
There are many designs for vessels with large L/B. The proceedings of the "FAST" series of conferences are a very good start if you want to see comparisons with multihulls and other types of high-speed vessels.

Stability is, as you mention, a concern. Nigel Gee (and others) have proposed a high-speed pentamaran, which is a large central hull with four small amas. (The amas are not immersed when the vessel is travelling in calm water.)

Regards,
Leo.
Reply With Quote
  #8  
Old 09-26-2005, 06:38 AM
FAST FRED FAST FRED is offline
Senior Member
 
Join Date: Oct 2002
Rep: 925 Posts: 3,997
Location: Conn in summers , Ortona FL in winter , with big dock & room for O'nite stop .
Leo,

My "dream boat" would be 65 LOA and 8 BWL with an overall beam of just under 12ft to allow surface transportation.
An old Commuter in style/profile but with offshore scantlings and range.

Cost is ofcourse a problem , but NOT if weight can be carried.

Very light construction costs loads more than just using 3/8 aluminum plate for the borrom that may see the ground and 1/4 for the hull & deck.

To cruise at 12 to 14K what would be the power requirements to shove a 20,000lb boat comparted to a far less costly to construct 30,000 lb boat?

I'm dreaming of a design that can get 5nm per gallon at cruise speed.

Thanks,

FAST FRED
Reply With Quote
  #9  
Old 09-26-2005, 08:22 AM
water addict water addict is offline
Naval Architect
 
Join Date: Jun 2004
Rep: 73 Posts: 313
Location: maryland
Quote:
Originally Posted by Bergalia
I think the first question is, TinyMan - why a long skinny boat ?
For well over 3,000 years we've been taking to sea in short fat boats...Why are you trying to 'buck the tide' ?
I also assume that you mean a boat 82 FEET long - not 82"(inches) by ten to twelve FEET wide and not 10-12" (inches wide).
And while Water Addict's note on naval ship displacements may be valid for the US navy (a young service with much learn) the Royal Navy is seriously searching the efficiency virtues of shorter fatter vessels.
Give us an example of the Royal Navy's search regarding short/fat vessels. I would be interested to hear. Of course I take issue with respect to your comment on the US navy, especially versus the Royal Navy, which is laughable by comparison (you asked for it).
Reply With Quote
  #10  
Old 09-26-2005, 09:17 AM
lewisboats's Avatar
lewisboats lewisboats is online now
Obsessed Member
 
Join Date: Oct 2002
Rep: 1587 Posts: 2,245
Location: Iowa
"I think the first question is, TinyMan - why a long skinny boat ?
For well over 3,000 years we've been taking to sea in short fat boats...Why are you trying to 'buck the tide' ?
I also assume that you mean a boat 82 FEET long - not 82"(inches) by ten to twelve FEET wide and not 10-12" (inches wide).
And while Water Addict's note on naval ship displacements may be valid for the US navy (a young service with much learn) the Royal Navy is seriously searching the efficiency virtues of shorter fatter vessels. "


"Give us an example of the Royal Navy's search regarding short/fat vessels. I would be interested to hear. Of course I take issue with respect to your comment on the US navy, especially versus the Royal Navy, which is laughable by comparison (you asked for it)."




Oooooo...This otta be good!
Aaaaannndd In this corner....wearing red, white and blue trunks... we have the brawny youngster packing 4 carrier groups (Nuke SuperCarrier, Guided missle cruiser, 2 guided missle destroyers, attack sub, and supply ship) and many smaller surface craft.
In the other corner, also wearing red, white and blue trunks is the Past Master with upteen centuries of experience... although having lost a little mass recently, with only 3 smaller carriers, 14 frigates and 8 destroyers along with misc smaller surface craft.

Gentlemen...shake hands, go to your corners and at the sound of the bell, come out swinging...

All in fun now

Steve
Reply With Quote
  #11  
Old 09-26-2005, 09:37 AM
Leo Lazauskas's Avatar
Leo Lazauskas Leo Lazauskas is offline
Senior Member
 
Join Date: Jan 2002
Rep: 2122 Posts: 2,465
Location: Adelaide, South Australia
Quote:
Originally Posted by FAST FRED
Leo,

My "dream boat" would be 65 LOA and 8 BWL with an overall beam of just under 12ft to allow surface transportation.
An old Commuter in style/profile but with offshore scantlings and range.

Cost is ofcourse a problem , but NOT if weight can be carried.

Very light construction costs loads more than just using 3/8 aluminum plate for the borrom that may see the ground and 1/4 for the hull & deck.

To cruise at 12 to 14K what would be the power requirements to shove a 20,000lb boat comparted to a far less costly to construct 30,000 lb boat?

I'm dreaming of a design that can get 5nm per gallon at cruise speed.

Thanks,

FAST FRED
It's not too difficult to calculate the drag and power requirements for vessels with your desired dimensions using a program like my "Michlet".

If you are serious about researching the topic have a look at the High-Speed Sealift workshop proceedings at:

http://www.ccdott.org/content/CS_fr.html

Good luck,
Leo.
Reply With Quote
  #12  
Old 09-26-2005, 11:35 AM
Bergalia's Avatar
Bergalia Bergalia is offline
Senior Member
 
Join Date: Aug 2005
Rep: 254 Posts: 2,517
Location: NSW Australia
Long skinny boats

Quote:
Originally Posted by water addict
Give us an example of the Royal Navy's search regarding short/fat vessels. I would be interested to hear. Of course I take issue with respect to your comment on the US navy, especially versus the Royal Navy, which is laughable by comparison (you asked for it).

Their Lords - the Admiralty (RN) have been debating the virtues of short fat/long thins - since the mid-1980's - but due to frequent deaths among the assembly have so far failed to reach a final decision - though lower deck 'scuttlebutt' has it that any new ships ordred will be of the short fat variety. Alas, however, under the Mad Cow Thatcher most RN ships were decommissioned - and under the Phoney Blair no new ships have been ordered. So for the time being my argument must remain on hold.
As for my tilt at the shortcomings of the US Navy... come on... can't you see when someone is pulling your leg.
Trust me, I've been drunk enough in the company of US swabs, in more disgusting establishments, on more continents, than my old mum could wave a stick at. But you still don't know how to play darts...
Reply With Quote
  #13  
Old 09-27-2005, 03:51 AM
Packeteer Packeteer is offline
Junior Member
 
Join Date: May 2005
Rep: 10 Posts: 64
Location: S33 E151
for an example of a successful long skinny powerboat look here: http://setsail.com/dashew/do_PARADIGM.html
Reply With Quote
  #14  
Old 09-27-2005, 08:06 AM
fcfc fcfc is offline
Senior Member
 
Join Date: Feb 2005
Rep: 399 Posts: 744
Location: france,europe
This one too : http://www.idlewildexpedition.ca/theboat.htm
And I fear much much less expensive.
Reply With Quote


  #15  
Old 09-28-2005, 05:49 PM
blared's Avatar
blared blared is offline
ALFA
 
Join Date: Aug 2005
Rep: 14 Posts: 2,693
Location: Orlando
The thing with the skinny boats is that they shake too much. If its a ship no problem but if its a small boat I prefer the wide ones, more confy and less shaky.
Reply With Quote
Reply



Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
Auto engine marinization DIY Marinizing 231 07-01-2010 08:34 PM
Long - Skinny Power Boats SAQuestor Boat Design 164 11-12-2009 06:28 PM
Boat building project in Sri Lanka gamage Post-Tsunami 82 11-20-2008 02:58 AM
Prices of used boats, US vs UK... Aquatek Open Discussion: All Things Boats & Boating 3 09-05-2005 06:57 PM
Long and skinny powerBoats (BIS) fcfc Boat Design 0 11-08-2004 05:16 AM


All times are GMT -4. The time now is 10:40 AM.


Powered by: vBulletin Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Web Site Design and Content Copyright ©1999 - 2014 Boat Design Net