The Dreadnought Project Forum Index The Dreadnought Project
Naval History in the years 1890-1920
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   Reg1sterReg1ster 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

Published ship dimensions

 
Post new topic   Reply to topic    The Dreadnought Project Forum Index -> Discussion
View previous topic :: View next topic  
Author Message
Horsa



Joined: 09 Dec 2005
Posts: 32
Location: England

PostPosted: Fri May 18, 2007 6:15 am    Post subject: Published ship dimensions Reply with quote

I'm finding that books tend to quote two figures for ship length
"pp" and "oa"

Could anyone tell me what these refer to ?

Thanks
Back to top
View user's profile Send private message Send e-mail
Harley



Joined: 23 Oct 2005
Posts: 131
Location: Great Britain

PostPosted: Fri May 18, 2007 8:32 am    Post subject: Reply with quote

Conveniently copied from somewhere (I can't remember if it was Wikipedia)...

o/a
o/a, o.a. or oa is an abbreviation for overall, and is used when describing the length of a ship. This term refers to the maximum length of a vessel from the two points on the hull most distant from each other, measured perpendicular to the waterline.

p/p
p/p, p.p., pp or lbp is an abbreviation for length between perpendiculars, and is used when describing the length of a ship. This term refers to the length of a vessel along the waterline from the forward surface of the stem, or main bow perpendicular member, to the after surface of the sternpost, or main stern perpendicular member. This was believed to give a reasonable idea of the ship's carrying capacity, as it excluded the small, often unusable volume contained in her overhanging ends. On some types of vessels this is, for all practical purposes, a waterline measurement. In a ship with raked stems, naturally this length changes as the draught of the ship changes, therefore it is measured from a defined loaded condition.

Simon
Back to top
View user's profile Send private message AIM Address MSN Messenger
Horsa



Joined: 09 Dec 2005
Posts: 32
Location: England

PostPosted: Fri May 18, 2007 9:09 am    Post subject: Reply with quote

Thanks

It's a relief to know that its not one of those obvious things you never knew but had never dared ask. :D
Back to top
View user's profile Send private message Send e-mail
maxyang



Joined: 31 Oct 2004
Posts: 100
Location: Shanghai, China

PostPosted: Fri May 18, 2007 11:03 am    Post subject: Reply with quote

Harley wrote:

p/p
p/p, p.p., pp or lbp is an abbreviation for length between perpendiculars, and is used when describing the length of a ship. This term refers to the length of a vessel along the waterline from the forward surface of the stem, or main bow perpendicular member, to the after surface of the sternpost, or main stern perpendicular member. This was believed to give a reasonable idea of the ship's carrying capacity, as it excluded the small, often unusable volume contained in her overhanging ends. On some types of vessels this is, for all practical purposes, a waterline measurement. In a ship with raked stems, naturally this length changes as the draught of the ship changes, therefore it is measured from a defined loaded condition.

Simon


I have a different description for p/p. The first p stands for front perpendicular, shorted for FP, which is usually the vertical line pass through the point where bow intersects with waterline. The second p stands for after perpendicular, shorted for AP, which is usually the rudder centerline. You can find them on AOTS Fuso, drawing B1-1 and the Queen Mary drawing attached with Robert's 'Battlecruiser'. The purpose of using perpendiculars is what Simon said.

Max
Back to top
View user's profile Send private message Visit poster's website MSN Messenger
tone
Site Admin


Joined: 29 Oct 2004
Posts: 479
Location: Boston

PostPosted: Fri May 18, 2007 3:29 pm    Post subject: Reply with quote

Yes, overall is if you put the ship on a shelf and slid two billboards toward each end. When they strike the ship (wherever they do), the overall length is the distance between the billboards.

And, with pp, I think I agree with Max when I say the aft one (as I understood this) is essentially the rudder's post, or axis of revolution.

tone
Back to top
View user's profile Send private message Send e-mail Visit poster's website AIM Address
Display posts from previous:   
Post new topic   Reply to topic    The Dreadnought Project Forum Index -> Discussion All times are GMT - 5 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group