Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 03-10-2016, 08:45   #1
Registered User

Join Date: Dec 2015
Posts: 10
thinkness of hull steel

Hi Folks .. first time question on this forum. Appreciate any and all input. My question is related to the thickness of steel hull. I know there is no true answer but what is an optimum gauge. I see a 60' sailboat with 1/4" for the hull. It's a blue water vessel. I have also see 3/8" on other boats. Certainly seems thicker is better up to a point of diminishing returns. Seems 1/4 is small number. Thanks for feedback ... Dennis
__________________

__________________
kingofcary is offline   Reply With Quote
Old 03-10-2016, 09:31   #2
Registered User

Join Date: Aug 2014
Posts: 13
Re: thinkness of hull steel

Quote:
Originally Posted by kingofcary View Post
Hi Folks .. first time question on this forum. Appreciate any and all input. My question is related to the thickness of steel hull. I know there is no true answer but what is an optimum gauge. I see a 60' sailboat with 1/4" for the hull. It's a blue water vessel. I have also see 3/8" on other boats. Certainly seems thicker is better up to a point of diminishing returns. Seems 1/4 is small number. Thanks for feedback ... Dennis

From my time own steel boats the builder started off at the keel with thicker steel and the thickness decreased as the boat was built up. Cabin tops and cabin sides do not require much thickness unless your going to use the boat for other than recreational use. Access to inspect the steel for corrosion is more important than having thicker steel.


Sent from my iPad using Cruisers Sailing Forum
__________________

__________________
Keel Scraper is offline   Reply With Quote
Old 03-10-2016, 10:36   #3
Registered User

Join Date: Mar 2014
Location: Qatar
Posts: 163
Re: thinkness of hull steel

The thickness per the designer depends on the spacing of frames and longitudinal as well as the service requirement. But to give you an idea, my 65' was 3/16" throughout the hull. In general 1/4" plating on a 60' is excellent. Have not ever seen 3/8" except on specialized commercial vessels. Are you sure you didn't mean to say 3/16"?
__________________
makobuilders is offline   Reply With Quote
Old 03-10-2016, 10:59   #4
Senior Cruiser

Cruisers Forum Supporter

Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 16,839
Re: thinkness of hull steel

Quote:
Originally Posted by kingofcary View Post
Hi Folks .. first time question on this forum. Appreciate any and all input. My question is related to the thickness of steel hull. I know there is no true answer but what is an optimum gauge. I see a 60' sailboat with 1/4" for the hull. It's a blue water vessel. I have also see 3/8" on other boats. Certainly seems thicker is better up to a point of diminishing returns. Seems 1/4 is small number. Thanks for feedback ... Dennis
Thicker is better? Why?

I think thicker is heavier and heavier structures are more loaded.

Then again think about steel vs. steel. Are you comparing the same material and construction methods?

I think that both 3/8 and 1/4 are heaps. You simply give more structural support to 3/8 so it all may ballance out (or not). Unless you opt for 'stiffer' steel on the 3/8 and thus get a lighter and stronger structure.

The above my opinions, not facts.

b.
__________________
barnakiel is offline   Reply With Quote
Old 03-10-2016, 16:49   #5
Registered User

Join Date: Dec 2015
Posts: 10
Re: thinkness of hull steel

Great feedback all .. thx .. the 60 I am looking at is 1/4 .. the 3/8 could have been as suggested a more specialized hull. Also the point as to the structure that supports the steel is key. U gave me what I need in that all things equal the 3/8 is good ..


Sent from my iPhone using Cruisers Sailing Forum
__________________
kingofcary is offline   Reply With Quote
Old 03-10-2016, 16:58   #6
Senior Cruiser
 
StuM's Avatar

Cruisers Forum Supporter

Join Date: Nov 2013
Location: Port Moresby,Papua New Guinea
Boat: FP Belize Maestro 43
Posts: 6,133
Re: thinkness of hull steel

Quote:
Originally Posted by barnakiel View Post
I think that both 3/8 and 1/4 are heaps. You simply give more structural support to 3/8 so it all may ballance out (or not). Unless you opt for 'stiffer' steel on the 3/8 and thus get a lighter and stronger structure.

The above my opinions, not facts.

b.
3/8 is half as thick again as 1/4. Why do you need to give it more structural support?
How can adding more structural support to heavier plates "ballance [sic] out"?
How can you get a lighter structure with 3/8 compared to 1/4?


Did you mean 3/16?
__________________
StuM is offline   Reply With Quote
Old 03-10-2016, 17:00   #7
Senior Cruiser
 
StuM's Avatar

Cruisers Forum Supporter

Join Date: Nov 2013
Location: Port Moresby,Papua New Guinea
Boat: FP Belize Maestro 43
Posts: 6,133
Re: thinkness of hull steel

Quote:
Originally Posted by kingofcary View Post
Great feedback all .. thx .. the 60 I am looking at is 1/4 .. the 3/8 could have been as suggested a more specialized hull. Also the point as to the structure that supports the steel is key. U gave me what I need in that all things equal the 3/8 is good ..
And 50% heavier than 1/4
__________________
StuM is offline   Reply With Quote
Old 03-10-2016, 17:03   #8
Registered User

Join Date: Oct 2008
Boat: Custom cutter, 42'
Posts: 346
Re: thinkness of hull steel

As one of the other posters said, steel thickness typically is reduced higher on the hull. On a 60 footer the keel bottom will probably be 3/4", the keel sides will probably be 3/8" to 1/2", 1/4 to 3/8 on the bottom, 3/16 to 1/4 on the sides, usually I'd expect 1/8" on the decks. Strength where it's needed and the lowest practical center of gravity.
__________________
Pauls is offline   Reply With Quote
Old 04-10-2016, 08:56   #9
Registered User

Join Date: Sep 2014
Posts: 373
Re: thinkness of hull steel

1/4 inch plate is 10 lbs per sq ft


3/8 inch plate is 15 lbs per sq ft.


so why do you need the extras weight
__________________
bsurvey is offline   Reply With Quote
Old 04-10-2016, 09:20   #10
Registered User

Join Date: Jul 2016
Posts: 697
Re: thinkness of hull steel

Structural keel and the frame(ribs) are what gives a steel boat strength - not the thickness of its hull. Thicker hull plates, unless needed for ice protection, is pointless beyond what's needed to prevent deflection at expected loads with the designed ribbing. Adding thickness unnecessarily just increases keel and frame design requirements without adding any performance or safety.
__________________
We are sailors, constantly moving forward while looking back. We travel alone, together and as one - to satisfy our curiosity, and ward off our fear of what should happen if we don't.
SV DestinyAscen is offline   Reply With Quote
Old 04-10-2016, 09:24   #11
Registered User

Join Date: Feb 2012
Location: Carrabelle, Florida
Boat: Self-built 44' steel trawler
Posts: 852
Re: thinkness of hull steel

My 44' 60,000 lb dry trawler is 6mm in the hull and 4mm in the superstructure, built on 30" frame spacing and 16" stringer spacing. It will crush anything made of fiberglass and most docks as well. Rusting really is only a problem above the waterline - with a generous supply of aluminum anodes and a resulting >1.0 volts on the test electrode, even bare metal under water does not rust.
__________________
tkeithlu is offline   Reply With Quote
Old 04-10-2016, 10:49   #12
Registered User

Join Date: Sep 2008
Location: Surrey, B.C. Canada
Boat: Passage 24/30 Cutter
Posts: 387
Re: thinkness of hull steel

Unless you're designing the boat yourself, the plate thickness will be specified by the NA who considers all aspects of the vessel and its future use when first he sets out to design it.
__________________
Sailorbob8599 is offline   Reply With Quote
Old 04-10-2016, 13:45   #13
Senior Cruiser
 
hpeer's Avatar

Cruisers Forum Supporter

Join Date: Dec 2008
Location: Philadelphia
Boat: Murray 33-Chouette & Pape Steelmaid-44-Safara-both steel cutters
Posts: 3,674
Re: thinkness of hull steel

Plate thickness is a function of size and strength needed and. Instruction practices.

Small steel boats will use down to 10gage steel. I'm told that below 10 gage the welding heat distortion becomes too difficult to control. 10 gage is a wee bit thicker than 1/8".

At about 38' - 40' you will typically see 3/-16" plate, although I've seen boats up to 50' in 10 gage.

Our 33'er is 10 gage, the 44'er is 1/4" below the water line and 3/16" above.

Small steel boat in 10 ga, say below about 35', will be overbuilt for the required scantlings.

60' is a whole pile of steel boat. So many questions come to mind.
__________________
hpeer is offline   Reply With Quote
Old 04-10-2016, 14:19   #14
Registered User
 
Manos1955's Avatar

Join Date: Jul 2012
Location: Thessalonki Greece
Boat: Westerly Centaur 26
Posts: 153
Send a message via Skype™ to Manos1955
Re: thinkness of hull steel

I have seen last year in Curacao a steel sailboat about 55feet on deck with its side plates so badly bended - deformed because of the waves that I passed the opportunity to buy her for 12,000 USD
Thin plates and a wide spacing between the ribs created the problem.
__________________
Manos1955 is offline   Reply With Quote
Old 04-10-2016, 14:38   #15
Registered User
 
UNCIVILIZED's Avatar

Join Date: Jun 2014
Location: Up the mast, looking for clean wind.
Boat: Currently Shopping, & Heavily in LUST!
Posts: 4,946
Re: thinkness of hull steel

Once you get past the point where the hull is strong enough to keep out the water, as well as survive some moderate knocks, weight becomes the enemy. With the exception of having a tiny extra bit o thickness in the plating for losses to corrosion over time. But this applies priarily to commercial steel vessels.

So then 1/4" plate weighs 6lb/sqft, plus; frames, stringers, insulation, fairing, primer & paint, & the boat's interior. Thus the all up weight of a section of the hull ill be well above this 10lb/sqft figure. Whereas with a boat made from cored composites can easily be as little as 2-3lb/sqft, including; fairing, primer & paint, & the interior. In other words, about what the interior, plus paint, etc. weighs in the steel boat, once it's hull's built.

That kind of weight differential makes it impossible to have a small steel vessel (under 40-50ft) perform at anywhere near the levels of boats made from other materials. Which is why small steel boats are uncommon, & my comment on weight being the enemy comes from.
You just can't make something that heavy sail well in less than 15-20kts of wind.
__________________

__________________

The Uncommon Thing, The Hard Thing, The Important Thing (in Life): Making Promises to Yourself, And Keeping Them.
UNCIVILIZED is offline   Reply With Quote
Reply

Tags
hull, steel

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Steel boat with stainless steel chainplates steve77 Construction, Maintenance & Refit 22 23-11-2015 07:45
Steering Cables - Steel or Stainless Steel ? sailorchic34 Construction, Maintenance & Refit 46 14-01-2014 16:46
Aluminum Hull or Steel Hull ? Lt. Monohull Sailboats 13 30-10-2011 12:55
steinless steel fittings on steel boat Gregoris Construction, Maintenance & Refit 5 14-03-2009 06:03


Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 01:42.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.