The addition of a compass to Olympic and Britannic


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Bob_Read

Guest
Early Olympic and Titanic had their standard compass mounted atop a compass platform amidships. After Olympic’s 1913 refit and in Britannic’s initial configuration, an additional compass was added on the roof of the navigating bridge. The amidships compass was retained on both ships. What was the purpose of the additional compass on the roof of the navigating bridge of both these ships?
 

Jim Currie

Member
Can't say for sure, Bob, but I can offer 2 reasons.

1: the standard compass on the top of the wheelhouse would have fewer induced magnetism errors and
2.: A standard compass on top of the bridge would allow the fitting of a periscope-type reflector viewer leading down to the steering position on the open bridge in front of the enclosed wheelhouse.

Thus the man on the wheel could view the standard course direct via a viewing mirror in front of his eyes. He would still have a steering compass but the error between the two would be very easy to ascertain.
These eventually became standard in every ship. They looked a bit like this.
1569864612650.png
 
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Bob_Read

Guest
Hi Jim: I found a discussion in the ET forum archives primarily between David G. Brown and Sam Halpern and the question that couldn’t be answered was if the compass on the roof of the navigating bridge was more desirable as a standard compass then why retain the midship compass?
 

Jim Currie

Member
That's a good question, Bob. I can only guess that it was left there because it was less costly than removing it and perhaps they thought it might serve as an extra conning position in the event of a bridge fire or something. Just guessing.
 
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Bob_Read

Guest
Hi Jim: Speculation is about all anybody has been able to come up with. David G. Brown has a novel theory that I can’t buy but beyond that it remains a mystery.
 
The only reason they had a compass on an amidships platform was that it was thought to have less deviation error than any other location. The funnels made that location not too desirable for taking bearings looking forward, and the amidship's compass still had some deviation error that needed to be compensated for. Then there came the gyro compass which gave true headings. They still had a compass comparison book for Olympic where they recorded steering and standard compass reading against the gyro readings. If I recall, heading entries were recorded about every 4 hours.
 
Bob, are you asking if they had a gyro compass why would they have a standard magnetic compass? Or, are you asking if they had a standard compass amidships why have another standard compass on over the navigating bridge?
 
OK, thanks for the clarification.
The compass added over the wheelhouse was a 10-inch Kelvin patent standard compass, same as amidships. Standard compasses were equipped with an azimuth mirror to take stellar bearings. My guess, as was Jim's, is that the amidship's compass was left as a backup, being more costly to remove it.
The advantage of placing the "standard" above the wheelhouse was that it eliminated the clumsy push-bell signaling used when steadying the ship by standard. Course laid out were always done so by standard, including when heading down channel waters. When turning onto a new course heading the ship needed to be steadied by standard. When done from the amidship's platform it used that push-bell method with required the officer on the platform to signal the bridge in a similar method used by the lookouts on the bell in the nest, 1-bell to turn to starboard, 2-bells to turn to port, 3-bells when on-course straight ahead. It was clumsy method and took some time to do.
 
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Bob_Read

Guest
Hi Sam: I could maybe buy your Olympic explanation if it weren’t for Britannic. Both compasses were installed on her from the start and both were planned for RMS Britannic according to her Specification Book. Do you buy David G. Brown’s contention that the midship compass was left so as not to raise suspicion that the midship placement of the standard compass was actually the cause of the collision with the iceberg by Titanic?
 
Do you buy David G. Brown’s contention that the midship compass was left so as not to raise suspicion that the midship placement of the standard compass was actually the cause of the collision with the iceberg by Titanic?
Just saw this Bob. My simple answer to your question is, no, I don't buy that.
 
Sajm, I suspect you don't buy my vuew ihaving two standard compasses as preposterous from the point of view of seamanship or navigation simply because I said it. But, you can't defend two standards by referring to standard nautical practices. So, why leave the platform compass? My hypothesis is based on the very real problem of tort law, even under Admiralty Law. Truth is the first victim when something is argued in court -- so why not leave the redundant old standard compass in place to avoid the stupidity of the legal profession? Just hunch on my part, but it certainly was not done for safety at sea.

Somebody else suggested it may have been left in position to save the cost of removiing it. This implies that buying a new binnacle and accompanying compass instrument. This iopposed to unbolting a full working setup and carrying it about 250 feet forward to the roof of the officers quarters. An, then removing the platform for the high scrap value of its non-magnetic parts.

Sometimes the best way to hide something is in plain sight.

-- David G. Brown
 
Or perhaps, David, the amidships location was thought to produce less deviation error that other compasses could be compared to, thus being 'the standard compass' on the ship, while placing a compass on top of the wheelhouse made the job of steadying up much easier, and gave an almost an unobstructed view when taking compass bearings ahead.
 
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Bob_Read

Guest
Would a telephone between the compass platform and the wheelhouse interfere with the accuracy of the standard compass on the compass platform?
 
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