Can you identify these? - Ships Nostalgia
11:12

Welcome
Welcome!Welcome to Ships Nostalgia, the world's greatest online community for people worldwide with an interest in ships and shipping. Whether you are crew, ex-crew, ship enthusiasts or cruisers, this is the forum for you. And what's more, it's completely FREE.

Click here to go to the forums home page and find out more.
Click here to join.
Log in
User Name Password

Can you identify these?

Reply
 
Thread Tools
  #1  
Old 23rd March 2006, 14:15
BarryM BarryM is offline  
Senior Member
 
Join Date: Jan 2006
Posts: 118
Can you identify these?

The attached is a detail from a plan of a WW2 Steam Gunboat (the "Denny" Grey Class) showing upper superstructure and mast/mast stays. My question is, what are the round black objects shown halfway up each of the eight mast stays? Photos of the Class show that most of the vessels had these round 'black blobs' while a few had elongated (sausage) shapes that must have been about 2-3 feet long. I'm well on with making a model of the class and like to know that I'm getting it right. One suggestion was 'silencers' to cut down rigging noise but what do you think? I will place a pint behind the bar of my local for the most convincing answer. Cheers!
Attached Images
File Type: jpg Stays detail.jpg (59.1 KB, 110 views)
Reply With Quote
  #2  
Old 23rd March 2006, 14:48
Paedrig's Avatar
Paedrig Paedrig is offline  
Senior Member
 
Join Date: Jan 2006
Posts: 186
Look as though they should be aerial stay insulators.
Reply With Quote
  #3  
Old 23rd March 2006, 14:49
jocksenior's Avatar
jocksenior jocksenior is offline  
Member
 
Join Date: Mar 2006
Posts: 35
I think they are insulators. had them on the plans of a Whale Catcher I built, I used split lead shot fishing wieghts, they do look the part.
Reply With Quote
  #4  
Old 23rd March 2006, 14:58
BarryM BarryM is offline  
Senior Member
 
Join Date: Jan 2006
Posts: 118
Gents,

The Class had its aerials slung fore and aft via the mast. As far as available plans and photographs show, at the upper end the stays terminate at mast brackets and at the lower end to the deck via rigging screws. If it helps, there were 4 upper stays (2 fore/2aft) and 4 lower stays (2 fore/2 aft). If these are insulators, thats an awful lot of aerials?
Reply With Quote
  #5  
Old 23rd March 2006, 15:23
Paedrig's Avatar
Paedrig Paedrig is offline  
Senior Member
 
Join Date: Jan 2006
Posts: 186
Take your point about a lot of aerials! But I recall one of our elderly tugs (1950s) having Ceramic insulators on the mast stays...irritating thing is I cant remember why
Reply With Quote
  #6  
Old 23rd March 2006, 16:55
John Rogers's Avatar
John Rogers John Rogers is offline  
Senior Member
Organisation: Merchant Navy
Department: Engineering
Active: 1947 - 1954
 
Join Date: May 2004
My location
Posts: 8,322
Could they be lightning arresters.
John
Reply With Quote
  #7  
Old 23rd March 2006, 19:30
Mad Landsman's Avatar
Mad Landsman Mad Landsman is online now  
Senior Member
 
Join Date: Dec 2005
Posts: 2,865
Many years ago, early 60s I think, I was aquainted with a radio engineer who had a shop but had done his time in the RN.
He told me about some experiments they had been involved in before WWII using more & more power to try to increase range. One day as he hit the key there was a big flash like lightning outside and he realised that they had got to the limit! Apparently some of this depended on the weather, relative humidity, etc.
From this I recall him telling me that the stay wires had 'egg' ceramic insulators fitted to stop the power on the main aerials from going to deck. I assumed that the masts were non-conductive.
Interesting point about lightning arresters - Thinking about it just how did the lightning get to ground if the main route down was insulated? Unless the insulators were fitted with lightning bypass rods and that's getting silly.
Reply With Quote
  #8  
Old 23rd March 2006, 19:51
gwzm gwzm is offline  
Senior Member
 
Join Date: Nov 2005
My location
Posts: 563
Any metallic rigging or metal bodies near the transmitting aerials will have eddy-currents induced in them. These currents in turn react with the current in the aerials themselves causing losses in the system and also losses in received signals. To prevent these losses, metallic shrouds and rigging near the transmitting aerials are broken up with insulators. These are usually made of glazed ceramic for strength and high insulation value. They also need to be kept clean to prevent electrical leakage across them.

From the Admiralty Handbook of Wireless Telegraphy, Volume 2, R24, e, iii:
"When transmission is taking place in a ship, all the stays, etc. will be set in oscillation at a frequency depending on their length. Stays should, therefore, be divided up into sections of such a length that minimum interference is caused to reception of short waves."

Hope this helps,

John/gwzm (ex-Brocklebank R/O)
Reply With Quote
  #9  
Old 23rd March 2006, 23:10
King Ratt's Avatar
King Ratt
 
Join Date: Aug 2005
My location
Posts: 1,233
These insulators were to break up the electrical length of the stays to minimise the re radiation of frequencies which affected the Direction Finder. that operated in the Medium Frequency band of 285-512 Khz. The DF loop can be seen clearly in the sketch.
Reply With Quote
  #10  
Old 23rd March 2006, 23:19
BarryM BarryM is offline  
Senior Member
 
Join Date: Jan 2006
Posts: 118
Ratty,

I go along with the idea of insulators but there is no DF loop on the plan. You must be confusing it with something else.

Thanks to all who replied, especially John/gwzm who wins the pint. I can now model away happily in the knowledge that I now know what I'm making. Cheers!
Reply With Quote
  #11  
Old 23rd March 2006, 23:27
billyboy's Avatar
Bilge Rat
Organisation: Merchant Navy
Department: Engineering
Active: 1957 - 1963
 
Join Date: Jul 2005
My location
Posts: 33,494
Hmmmm, grey class. there was one commanded by sir peter scott. he used to close in shore and get pictures of ducks. think he was based in dover at that time. the grey goose was at newhaven for a while then went round to shoreham, near the lady bee boatyard. I cant remember if she had these insulators or in fact if she is still in shoreham (probably a rich mans gin palace now) perhaps one of our southern members can throw a bit light on that one for you.
__________________
"Imagination is more important than knowledge". A. Einstein.
Reply With Quote
  #12  
Old 24th March 2006, 06:23
R651400's Avatar
R651400 R651400 is online now  
Senior Member
 
Join Date: Jun 2005
Posts: 5,119
Isn't that a DF loop under the lower arrow?
Looks like a swinging loop rather than Bellini-Tosi.
Reply With Quote
  #13  
Old 24th March 2006, 09:17
BarryM BarryM is offline  
Senior Member
 
Join Date: Jan 2006
Posts: 118
R651400 - Sorry, that "DF Loop" is an 18" searchlight seen in side elevation!

Billyboy - The Grey Goose outlasted all her sisters until 1955 when she was used as a floating testbed for gas turbine propulsion. As far as I know, she was scrapped on completion of trials.
Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

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

vB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Can any identify the ussc ships berthed in Lyttleton lagerstedt Union Steam ship Co Of New Zealand LTD 24 1st December 2005 03:42
Can you identify this sailing ship for me pse. lagerstedt Preserved Vessels & Restoration Projects 4 23rd November 2005 08:28



Search the net with ask.com
Support SN
Ask.com and get


Powered by vBulletin® Version 3.6.8
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.