HMS Terror by clearway - FINISHED - OcCre - 1:75 - upgraded

[clearway]

You could maybe have the door open slightly and roll up bits of cigarette paper to imitate the charts😇. How does the Azimuth compass box compare to yours size wise?

 

Keith

[Keith S]

I haven't made anything for that table yet, but the azimuth compass I saw in Greenwich was in a box about 30cm square, about the size of an RN lifeboat compass. As I understand it, its function was to compare magnetic North with True North, to plot isogonal lines. In aviation we have a machine called an "astrocompass" that is used in extreme North and South latitudes to find true direction because magnetic direction is so unreliable. (They are solid brass and more-or-less immortal: mine still functions perfectly and its first inspection stamp is by a Royal Navy inspector in 1943) The azimuth compass looks like a stylish version of one of those, but mounted on a gimballed magnetic compass. I guess its function is somewhat the reverse of an astrocompass: we use azimuth, latitude, and local hour angle from charts to set the astro and it gives us direction. I imagine the crew of Terror and other ships used the azimuth compass to make observations for future navigators. Celestial navigation is not my strong suit however so I may not be entirely correct. Maybe it was a navigational tool, observation tool, or both! But we know that one of the Terror's responsibilities was to make magnetic observations. 

 

So, anyway, 30cm in 1:75 scale would be 4mm, which seems to me to be pretty close to the size of the box you've mounted on your table. I will probably do the same. 

[Keith S]

As a postscript, I have been scrutinizing the plans and I can't find any evidence that Craig is incorrect about there being a post penetrating that table for some purpose, either. (Although I admit that I originally found it preposterous that someone would punch a post through a perfectly good chart-table).  I wouldn't glue the azimuth compass box down, quite yet. Maybe it is not a co-incidence that the size of the box and the diameter of that mystery post are roughly equivalent. Let's do more research on Azimuth compasses and their use, and then debate about it some more. 

 

If that post turns out to be some kind of mounting structure for the azimuth compass, AND it turns out that the azimuth compass is for steering as well as observing, it might solve the problem of where to put the ship's compass in general!

 

Well, what else do we have to do? I'm trapped in an airport at the minute. 

Edited August 21, 2022 by Keith S

[clearway]

I am thinking along them lines as well Keith but does seem a bit bizarre having a long post like that going through a table but hey we are dealing with Terror and Erebus here!

I am sooooooo glad i didnt belay the main braces yet because they will definitely get in the way. 

 

ouch at being stuck in airport m8.

 

Keith

[Keith S]

Well, HERE is some information. I don't know why it didn't occur to me to look at Wikipedia before, other than since I already knew about Compasses I guess I reckoned I didn't need to. Anyway, I finally DID look at Wikipedia, and I found this paragraph, which seems as though it might be relevant. 😵‍

 

I hi-lighted the relevant text: Perhaps the installation of the engine and maybe the bow plating introduced enough iron to the ship that it became necessary to elevate the a-compass onto a post, as it says here. Although that makes me wonder: why not just adjust it? Is the "pedestal" our mystery post??

Edited August 21, 2022 by Keith S

[clearway]

i was thinking along them lines Keith as there is a bloody great steam engine right below them, that is one reason i was going to mount a binnacle on the elevated bridge but it really is too narrow so the post could be for mounting the compass and pedestal on, but still seems odd putting it through the middle of a table ....ahhh the conundrum of our little Terrors continues😎

You will see a raised platform on the old steamers, ocean liners and warships which was to keep the compass away from the ironwork, later they used magnets to offset the effect of the iron/ steel work.

Keith

[Keith Black]

 

52 minutes ago, clearway said:

later they used magnets to offset the effect of the iron/ steel work.

 Lord Kelvin invented his compensating balls in the 1880's. Interesting bit of history in the below. 

 

https://southstreetseaportmuseum.org/the-ships-compass-and-its-binnacle/

[DanielD]

Good afternoon Keith(s), all of you…

 

Great work on all the research on the ice bridge and this compass post! 

[clearway]

Thanks Daniel and Keith B , who would have thought a compass and plank of wood could have caused so much debate😁. Also it is great to see my other long suffering Terror compadre back on the scene after his long break .

 

Keith

[iMustBeCrazy]

3 hours ago, Keith S said:

As a postscript, I have been scrutinizing the plans and I can't find any evidence that Craig is incorrect about there being a post penetrating that table for some purpose, either. (Although I admit that I originally found it preposterous that someone would punch a post through a perfectly good chart-table).  I wouldn't glue the azimuth compass box down, quite yet. Maybe it is not a co-incidence that the size of the box and the diameter of that mystery post are roughly equivalent. Let's do more research on Azimuth compasses and their use, and then debate about it some more. 

 

If that post turns out to be some kind of mounting structure for the azimuth compass, AND it turns out that the azimuth compass is for steering as well as observing, it might solve the problem of where to put the ship's compass in general!

I did a search on 19th Century Azimuth compasses yesterday and most had sights for taking bearings. The post is too tall to take bearings while standing on the deck and too low for taking bearings from the bridge so I hypothesise (one of those 'middle of the night' thoughts) that the table is actually a platform to stand on while taking bearings, giving 360° views with a higher line of sight. It also explains why the post comes through the middle of the table.

 

It would be impractical for it to be used by the helmsman so I think that puzzle remains.

Edited August 21, 2022 by iMustBeCrazy

[Keith S]

12 minutes ago, iMustBeCrazy said:

I did a search on 19th Century Azimuth compasses yesterday and most had sights for taking bearings. The post is too tall to take bearings while standing on the deck and too low for taking bearings from the bridge so I hypothesise (one of those 'middle of the night' thoughts) that the table is actually a platform to stand on while taking bearings, giving 360° views with a higher line of sight. It also explains why the post comes through the middle of the table.

 

It would be impractical for it to be used by the helmsman so I think that puzzle remains.

 

That is a very interesting idea, AND it makes a lot of sense. You'd need to be able to take sights at a variety of angles, so it would be sensible to have it mounted at eyeball height. It's like the pelorus on the bridge of a modern ship. 

 

As far as "taking measurements" is concerned, I think I've been getting the azimuth compass mixed up with the "dip needle compass". I have learned that an "azimuth compass" is basically a magnetic compass combined with an astrocompass. 

 

I have been thinking about it all day, and I think you are 100% right about that table with the post sticking out of it. Elevating the compass away from the steam engine, and making a platform (like a pelorus) that a standing man can use to sight the azimuth part, as well as Keith Black's point that correcting magnets weren't invented until the 1880s: it all makes sense. This will be an exciting detail to add to our models!

Edited August 21, 2022 by Keith S

[iMustBeCrazy]

1 hour ago, Keith S said:

AND it makes a lot of sense.

And the more you think about it:

It answers the question as to why the bridge didn't use it as a support, it answers the question as to why a post would be put in the middle of the 'chart table', it even answers the question as to why the post was rounded.

 

Part of the problem we had was thinking that the table was a chart table, but would they really have taken such valuable charts on deck? Far more likely they made notes and sketches in a notebook and used those to update the charts in the cabin out of the wind and weather.

 

[Keith Black]

 Who needs underwater archeological data? Just give you guys a set of arcane plans and a couple of etch a sketch drawings......... I'm duly impressed. 

[clearway]

Thanks everyone- looks like my table is getting a hole in it!!!! I have been thinking if the post is for a pelorus that

is mounted on top of the post, someone standing on the bridge will be able to get his line of sight and shout down to helmsman "mark" while also communicating with navigators at the table? The bridge will be just as good as the top of the table for observing and if someone said to me "stand on that table and take bearings" while at sea i would be court martialled for offensive language 😁

 

Keith

Edited August 22, 2022 by clearway
missed info

[clearway]

Thanks for the likes, comments and looking in folks. Craig i would like to thank you for your input (they do say a fresh pair of eyes looking at a problem works wonders).  Also thanks to Keith S (we are getting there Keith)!

Had a play about recreating the azimuth compass column (thanks again Craig, have been trying to figure out for two years what that column was for, as they say "say what you see"... it was all there)! Bad part is that skid beam i put in 3 mm too far has come back to bite me😬 so will have to put the hole in the table forward of centre....... Now how long to make that bridge!

 

 

 

Take care all

 

Keith

 

P.S.Keith B i have been chuckling at this comment for a couple of days now "Lord Kelvin invented his compensating balls" God bless school boy humour🤣

Edited August 22, 2022 by clearway
typo

[iMustBeCrazy]

1 hour ago, clearway said:

Bad part is that skid beam i put in 3 mm too far has come back to bite me

It seems to be more an issue with the kit, for it all to fit as drawn the aft side of the skid beam should almost touch the mast. I'm not sure what exactly the cause is, perhaps slightly oversize deadeyes?

 

I would probably shave off a few half millimeters where I could, notch the davit post so the skid beam fits flush, shave half millimeter off the skid beam, notch the skid beam another half millimeter where it meets the davit post, shave a bit more off the bridge, make the compass post a half millimeter smaller etc. The profile plan shows about a 15 inch gap between the bridge and compass post to get your head up to take a site at 1:75 call it 5mm.

 

2 hours ago, clearway said:

Now how long to make that bridge!

Up to you but I would say the original was most likely about 42 feet.

 

 

 

[iMustBeCrazy]

I've also been playing with the bridge, it doesn't really work but I thought I'd open it up for discussion.

 

 

[Keith Black]

2 hours ago, clearway said:

how long to make that bridge

Careful, Keith, don't make it a bridge too far. 

[clearway]

Thanks for the input Craig and certainly can't be ruled out. I have been looking at the owen stanley pics of Terror and Erebus again and noticed a couple of things.

it shows the two skid beam support posts and what looks like a diagonal rod going from the bridge end to the support post. Also the davit arms are held by halliards leading to the mizzen aka hms victory davit style.

 

Regards the handrail will stick with a single row of stanchions with rope handrails and iron rod supports either side of midships.

 

Take care all Keith

[iMustBeCrazy]

1 hour ago, clearway said:

it shows the two skid beam support posts and what looks like a diagonal rod going from the bridge end to the support post.

Kieth, first thing to remember is it's an artists impression, useful for things like curved davits, the face the bridge existed and some details like the halliards. But the davits are shown as inside the bulwarks when we're pretty sure they were outside and the davits are way out of proportion, the skid beams and post don't seem to be shown but perhaps two support posts for the bridge are? Perhaps they removed the skids and used the to operate the davits?

 

I agree with iron stanchions with rope handrails (that's what I tried to depict above) but how many to provide support, you could tension the rope better if you had a diagonal support at the outer posts which would need less stanchions.

 

Anyway, here's an enlargement of the drawing:

 

 

[Keith S]

It's true. I suspect the artists drew a rough outline and then fleshed out the details like rigging later in their cabin, based on their knowledge of standard ship practice. 

 

Another explanation for that "diagonal" line you see in the picture: the davit arms themselves would have had a chain or line connecting them, as well as stabilizing line or chain going from each davit to the bulwark. I am still stuck in an airport (I don't think I'm getting home alive) but I have a book at home showing davit arrangements (I think) and the vertical posts on Terror make the halyards from the mizzen head redundant. They also show the stabilizing chains. I will try to find it, if I am spared.

 

Another curious thing about those pictures: where are the whaleboats? Aren't they supposed to be stacked up on the "skid beams" at this point? Are they being stored on the supply ship for the Atlantic part of the voyage?

 

 

Edited August 23, 2022 by Keith S

[clearway]

2 hours ago, Keith S said:

Another curious thing about those pictures: where are the whaleboats? Aren't they supposed to be stacked up on the "skid beams" at this point? Are they being stored on the supply ship for the Atlantic part of the voyage?

 

That is a very good point Keith - they also seem absent on the "our friend the pitcher" drawing. 🤪🤨🤪- ouch my friend you are still stuck in the airport!!!!!

 

Keith

[Keith S]

I have been trying hard to find on the internet a reference to azimuth compasses being raised above the deck for any reason, just because that mysterious post on the 1939 plans continues to perplex me. I found this sentence in a paragraph describing Ross' attempts to make his compasses show something consistent and sensible compared with one another:

 

 

[DanielD]

Great work Keith S, Keith (Clearway) and Craig (iMustBeCrazy). You guys are awesome in research and finding the odd piece of information to fill in the blanks. Again, thanks for all your hard work on the Terror project.

 

[clearway]

Thankyou Daniel, intriguing Keith and it might help explain why upon refitting to the 1839 plans terror and Erebus ended up with a bridge and a pedestal to mount the compass on. I suspect there should be another compass for the helmsman as well and the portable Royal navy one we were discussing what feels like centuries ago could be very likely.

 

I was just thinking guys that we might be the first people (along i imagine with Matthew Betts) to seriously look into the ice bridge / compass conundrum since 1845?

 

keith

[clearway]

just found this on the mystic seaport website,

In fact, it is common for the standard compass to be mounted away from the helm position even on modern vessels. Also note that in addition to her main compass  which was remote from the helm, Wavertree was equipped with two steering compasses located by the helm on the quarterdeck. These would be the references the helmsman would use to steer a steady course. 

Left: This image shows one of a pair of steering binnacles by the wheel on Wavertree’s sister ship, the Leicester. (South Street Seaport Museum Archives)

In fact there may also be other compasses aboard a ship such as a “Tell-Tale Compass”  in the Captain’s quarters by which the Master could see the course being steered without going on deck. Some larger ships are required to carry a spare compass in addition to thor standard compass to this day.

 

and a drawing of hms beagle

 hmmm food for thought!

 

Keith

Edited August 23, 2022 by clearway

[iMustBeCrazy]

Well, it seems I have been rather lacking, I have been limiting myself to those lovely high resolution scans from wiki commons and ignoring the low res ones at the RMG.

 

Specifically ZAZ5672 of which there are two versions, the first shows the bridge details in red the second in black which leads me to think it depicts section A-A (or thereabouts) below.

 

[Keith S]

I ordered high-resolution prints of those. I received a lovely big high-resolution rolled-up one of the more modern side-view, but the other ones were clearly just copied from the horrible pictures on the website. I was a bit annoyed about that. Also those older ones of "Terror" have A LOT of differences, like the cut-down bulwark midships and the forward ladderway being 90 degrees to how it wound up later. Absurdly the modifications to the stern for the screw are drawn on the OLDER plans. It's like they just did whatever they wanted...and were afraid to waste paper!

 

Just out of interest, I was snooping around on Park Canada's website and found these helpful drawings. Anyone looking for the confounded bridge will have to look a bit harder! 

 

 

Edited August 24, 2022 by Keith S

[iMustBeCrazy]

Ok, a different version, a little closer perhaps:

 

 

[clearway]

Hmmm the idea of the stanchions ion the skid beam looks like a winner and would make mounting a ladder safer- i'm considering it massively. Also Keith did you see the earlier post regards binnacles and i have looked at those parks Canada sketches a few times and wondered what is that square in a square set up abaft the officers mess skylight? I am going to change the base of the compass post to a square footing as opposed to the hat stand style feet i have at the moment.

 

Take care all Keith