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Old 03-27-2023, 08:25 PM   #41
whswhs
 
Join Date: Jun 2005
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Default Re: Gurps vehicles to design boats?

Quote:
Originally Posted by David L Pulver View Post
Sure, isn't that the simplest solution?
Yes, I'm fine with that as a formula. But I'd like to have guidelines for flotation/weight ratios for broad categories of ships. You have such guidelines for Mediocre, Average, Fine, and Very Fine lines, so I don't see why we can't provide similar guidelines for how low in the water ships ride.
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Old 03-28-2023, 11:51 AM   #42
hal
 
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Default Re: Gurps vehicles to design boats?

I went a different route of sorts with regards to this question of "Draft".

I reasoned that I should be able to take a known ship, and attempt to create a GURPS analog of it using the rules. One of the first things I did was throw out (sorry David!) the rules for Draft.

To reiterate here what those numerical formula rules are:

"Draft in feet = [(cube root of Lwt.)/15] x Hl."

So, to get a historical draft of 23 feet as is had by the HMS VICTORY, we fill in the values of:

31 Million pounds for Loaded Weight and 1.1 for HI. Net result is 23.037 feet.

Somehow, I very much doubt that the HMS VICTORY weighs some 13,839.29 long tons.

The real issue here is that if you designate the dimensions of the ship's hull to the extent that you know that it has a given cubic foot volume for the entire hull, and you know its carried load in pounds - the max load of that hull will be 64 lbs (one cubic foot of salt water weighs 64 lbs) per cubic foot of volume. If the hull needs to have a given amount of freeboard - then the formula will need to determine how much of a ship's volume is under the water line, and how much is over.

In the end? I can give you the amount of ballast weight recorded for the HMS VICTORY before she received her yards and masts and sails. As more things were added to the ship, more of her ballast was removed such that she road at her ideal water line.

If you know for example, the weight of all of her guns - then you will know just how much ballast they had to remove in order to match the weight of the guns themselves. If you know how much food stores the ship carried to feed 880 men for 6 months, you will likely know too, that the HMS VICTORY was riding higher because half of her stores were gone. If each man was allotted roughly 3 lbs of food per day, that is 880 x 3 lbs x 3 months or about 91 days worth. Total weight lost for food alone was 107.25 long tons. That doesn't include the weight lost due to fresh water or alcohol consumed.

LINE OF BATTLE gives us the usual British shot and powder allocations for the British Warships - and I'm guessing that were I to read that Owners Manual for the HMS VICTORY - I'll find out just how much powder was stored, how much shots, wads, etc. (heck, in one post, I did mention how much the HMS VICTORY fired during Trafalgar - which had been given to me by a curator aboard the HMS VICTORY).

So, problem the first is determining how many cubic feet real life ships had, before you can assign the GURPS amount as well. This data is something they NEVER provided. Short of building ships from the draughts stored at the British Admiralty, and then measuring their volume to modern stanards, we're never going to be able to do more than GUESS at the actual hull volume for real world ships.

When they measured ships by their keel length, and their beam, and then by their depth in hold (usually about 1/2 their Beam) - the British only cared about how much the ship could carry by weight. A tun was conveniently equal to about one long ton (one tun of wine was about 2240 lbs in weight). Now for the fun part...

252 gallons of liquid occupies about 33.69 cubic feet in volume.

That is what the British Expected to be able to carry within its holds more or less, and rated at 2142 tuns burthen.

From that alone, we can estimate the hull contained at least 72,163 cubic feet in volume. This includes SOME of the ship above the water line.

In the end? It takes lot of the work to try and build a ship that matches to a large degree, the age of sail ships. Putting this into perspective? Going from memory, the ballast placed in the HMS Victory during its building phase without masts, rigging etc - was about 800 tons. This would have been Relatively close to the standard draft of 23 feet for the vessel as it was an attempt to keep it as close as to what it would be in the sea "standards".

I can do more research if anyone wants - or they can simply email me privately if they're interested.

Hal

PS - Per the rules, The ratio of Shp's Keel to its Beam was almost 3:1. It was actually closer to 2.9 to 1 if that helps.
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Last edited by hal; 03-28-2023 at 11:53 AM. Reason: PS...
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Old 04-03-2023, 10:37 PM   #43
hal
 
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Location: Buffalo, New York
Default Re: Gurps vehicles to design boats?

I am so proud of myself...

I made the mistake of looking at ship models online from Amazon, only to neglect to remember that Amazon records those things you look at and then sends emails to say "hey, buy this".

What did Amazon suggest I buy? A 1:450 scale model of the HMS Victory.

So why am I proud of myself? I honestly considered purchasing the model so I could glue the hull together, and buy a scientific beaker to measure liquids with on the premise that I could use the 1:450 scale methodology of measuring the internal volume of the model. While it would not be entirely scientific overall, it would at least offer me the possibility of an insight of what the internal volume would be approximately.

Dang, but I dodged a bullet on that one. The only reason I didn't pick up that model for $23.50 plus S&H is because it lacked any rigging for it. That and "where would I put the finished model?
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Old 04-04-2023, 01:45 AM   #44
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Default Re: Gurps vehicles to design boats?

Quote:
Originally Posted by hal View Post
I honestly considered purchasing the model so I could glue the hull together, and buy a scientific beaker to measure liquids with on the premise that I could use the 1:450 scale methodology of measuring the internal volume of the model.
I've been below-decks on the actual ship. Quite a bit of the internal volume is taken up with supporting structure for the hull, decks, and masts.
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Old 04-04-2023, 03:23 AM   #45
hal
 
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Default Re: Gurps vehicles to design boats?

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Originally Posted by johndallman View Post
I've been below-decks on the actual ship. Quite a bit of the internal volume is taken up with supporting structure for the hull, decks, and masts.
That makes me feel even better. Thanks

:)
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Old 04-17-2023, 05:28 AM   #46
hal
 
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Default Re: Gurps vehicles to design boats?

I've been coming back to this topic from time to time, re-reading some reference books, and event starting to input data into a spreadsheet so that eventually, I can try to see what the relationship is between the "tons" value of a ship vs the cost per ton values, and other aspects where possible.

DEANE'S DOCTRINE OF NAVAL ARCHITECTURE, 1670 has an appendix listing some 107 ships, their guns, required crew, length of keel, breadth of beam, depth in hold, etc. Formula for a ship's tonnage was such that it was: (length of keel x breadth of beam x 1/2 Breadth of beam)/94. If you look at the wikipedia article on Builider's Old Measure, there is another formula listed, than the one I did, but gives a result VERY close to the one I listed here.

So, for example, A ketch listed as Wivenhoe Ketch (build in Wivenhoe England and priced at about £1037 fully rigged and lacking 10 guns) measured as 50' keel, 17.5' Beam, 9' depth of hold - had a draft of 8.33 (8' 4") feet - Calculated Tons (Builder's old measure) works out to 81.44 tons, while the book lists the ship's tons as 79. What is even more of interest to me is that the book lists "Tuns and Tunnage" as a unit of measure that was equal to 105 tuns. This implies to me that a ship rated as say, 80 tons builder's old measure, could carry about 1 third again as much weight as a matter of course.

This in turn had me digging into a book titled "The Sailor's Word Book" by Admiral W.H. Smyth - originally published (If I read it right) 1867. This is what the Book of Words has to say about Burden (which was reference when I looked up Tonnage)

Burden. Is the quantity of contents or number of tons or weight of goods or munitions which a ship will carry when loaded to a proper sea-trim: and this is ascertained by certain fixed rules of measurement. The precise burden or burthen is about twice the tonnage, but then a vessel would be deemed deeply laden.

and

TON, or TUN [from the Anglo-Saxon Tunne]. In commerce, 20 cwt, or 2240 lbs, but in the cubical contents of a ship, it is the weight of water equal to 2000 lbs, by which the general standard for liquids. A tun of wine or oil contains 4 hogsheads. A ton or load of timber is a measure of 40 cubic feet of in the rough, and of 50 when sawn; 42 cubic feet of articles equals one ton in shipment.

Which brings me to another point...

Alternative formula for calculating tonnage loosely based on Builder's old Measure (see Wikipedia article of Builder's Old Measure).

In 1678 Thames shipbuilders used a method assuming that a ship's burden would be 3/5 of its displacement. Since tonnage is calculated by multiplying length × beam × draft × block coefficient, all divided by 35 ft3 per ton of seawater


And finally, as food for thought:

LADEN. The state of a ship when charged with material equal to her capacity. If the goods be heavy, her burden is determined by weight; but if light, she carries as much as she can conveniently stow. A ton in measure is estimated at 2000 lbs in weight; a vessel of 200 tons ought therefore to carry a weight equal to 400,000 lbs in weight; but if she cannot float high enough with as great a quantity of it as her hold will contain, then a diminution of it becomes necessary. Vessels carry heavy goods by the ton of 20 cwt*, but lighter goods by a ton of cubic feet, which varies by the custom of the port; in London it is 40, in India from 50 to 52, depending on the goods. Vessels may carry (not safely) twice their tonnage.

*cwt = hundredweight or 112 lbs
1 Pound Sterling (£) is equal to 240 pence or 20 shillings, there being 12 pence per shilling.

Hope this helps.
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Old 04-17-2023, 10:19 AM   #47
Rupert
 
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Default Re: Gurps vehicles to design boats?

When it comes to cargo densities, I found this:

From _Ship Construction and Calculations, 7th edition_, by George Nicol (1942, Brown, Son & Ferguson):

Rates of Stowage

Cargo No. of Cubic Feet per Ton (Imperial - 2240 lbs)
Coal, Scotch 44
Coal, Welsh 40
Coal, Newcastle 44
Manchester Bales 50 (may go as high as 150)
Pig Iron 9
Alkali in Casks 47
Wheat 46 (varies from 40 to 52)
Flour 45
Maize 46
Barley 58
Oats 72
Tea 83-120
Raw Sugar in Baskets 50
Cotton, American 130
Cotton, Indian 60 (machine pressed)
Cotton, Egyptian 70-220
Jute 49-77 (the lower if strongly machine pressed)
Wool, undumped 235
Wool, washed & dumped 100
Wool, greasy & dumped 84
Potatoes 50
Bacon & Hams in cases 64
Peas and Beans 43-53
Beef, frozen & packed 90-95
Beef, chilled & hung 120
Mutton, New Zealand 105-110
Mutton, River Plate 115
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Old 05-07-2023, 12:34 AM   #48
ArtosApNab
 
Join Date: Apr 2019
Default Re: Gurps vehicles to design boats?

I bet a minimum of 50% of all low tech ships have wrong stats. And i'd like to know how the many auctors calculate the stats of vehicles written in product we buy with MONEY (and i'm talking about Low Tech Companions, Vehicles- Transport of Fantasy, Vehicles- War Galleys).
For example, if you write rules about boarding, without describing how tall is a ship (NOT the draft, the draft+freeboard, am i asking too much to PRO rpg auctors?), without describing how many decks a ships has, etc.etc., the result i must to break my brain on LWT, EWT,LWT.not funny at all.
For the Spaceships they built a whole system to build up vessels to hunt aliens, but nothing for a sailships.
I'm disappointed.
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Old 05-07-2023, 12:38 AM   #49
ArtosApNab
 
Join Date: Apr 2019
Default Re: Gurps vehicles to design boats?

Quote:
Originally Posted by Fred Brackin View Post
Ve2 will give you mass and a simple answer for volume as well as HP and DR. It will handle crew size, cargo capacity, accommodations and armament and other things like that in pretty good detail. You would need Expansions I for more detail about sailing.

You might also want the Gurps Vehicle Builder program to automate all the stuff..

http://www.sjgames.com/gurps/vehiclebuilder/

I'm afraid it's a fairly old program now but I beleive it still works.
what a pity...very good productfor 3E but u must to convert the dates in 4e rules. welcome in the Year 19 AFE (after fourth edition)
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Old 05-07-2023, 12:39 AM   #50
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Default Re: Gurps vehicles to design boats?

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Originally Posted by whswhs View Post

The formula on p. 16 of Vehicles gives it a volume of 35 cf per displacement ton, or 2719.5 cf. Applying a multiplier of 1.3 for Fine lines gets us to 3535.35 cf. We'll use the larger figure.

Draft is the cube root of loaded weight in pounds, divided by 15, times 1.3 for Fine lines. That comes out to 4'8".

Multiplying draft by flotation, which is 169,696.8 lbs. or 84.85 tons, and dividing by 77.7 tons, gives height of 5'10". Since draft is 4'8", freeboard is 1'2".

.
sorry, mister, where u found out "169,696.8 lbs"?
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