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What does this mean?

A

AllanKP69

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In reading a contract for a 30 foot pinnace written in 1790 I came across scantlings for which I have no idea what they mean.

Depth of the Keel: 5 ins breadth 4 ins, Scantlings of the timbers 1 ½ ins Roome and space 13ins, depth of the Gunwales up & down 4½: ins in and out 2 ins & 1½ in

I understand the keel and frames as well as the room and space. I also get the gunwale dimension up and down at 4.5" But, what does the gunwale in and out 2 inches and 1½ inches mean? Is it a total of 3.5" or something altogether different? Steel gives dimensions for a 28 foot pinnace of 3½ inches deep by 1½ inches thick.

I wonder if the contract is describing the gunwale being in and out a different amount such as 2 inches at the bow, but less for the remainder of the gunwale.

Some choices follow for various contemporary boat plans but they are all launches, not pinnaces. Any and all ideas are welcome.

Thank you
Allan



1755108689835.png
 
Well Allan, if you don’t know I doubt that anyone else does. So I asked ChatGPT5 and it said:



I think I can help untangle this — the wording in 18th-century boat scantling lists often sounds opaque because they mix shipwright jargon with a “you know what I mean” shorthand that was never meant for outsiders.

Let’s break your example down step-by-step:

1. “Gunwale up & down 4½ inches”

That’s straightforward: this is the vertical dimension (depth) of the gunwale timber.


2. “In and out 2 ins & 1½ ins”

Here “in and out” is the horizontal dimension — the breadth of the timber measured across the boat from inside to outside.

But the fact that there are two figures given means they are telling you that the in-and-out breadth varies along the boat. This could be:


  • a) Two different stations — e.g., 2 inches at the midship sections, 1½ inches toward the ends (common in small craft to save weight and because less strength is needed at the extremities).
  • b) Inner and outer members — e.g., an outer gunwale strip and an inner gunwale (or “inwale”), each with its own thickness. However, contracts usually label these separately as “gunwale” and “inwale,” so I think this is less likely here.

3. Why I think it’s a fore-and-aft variation

In contemporary contracts and mould loft records for cutters, gigs, and launches, you often see things like:

“Gunwale up & down 3½ in. in & out 2 in. amidships, 1½ in. at ends.”

It’s shorthand, assuming the builder knows where to make the change. Often the wider amidships section also has more depth; but here, depth is fixed at 4½″, only breadth changes.

4. How this matches Steel’s figures

Steel’s Elements and Practice of Naval Architecture (for a 28-ft pinnace: 3½″ × 1½″) gives a single amidships dimension. That would be roughly your 4½″ × 1½″ end dimension if we think of your contract’s “reduced” ends. Your contract’s 2″ breadth amidships is actually stouter than Steel’s.

Conclusion:


Most likely, “in and out 2 ins & 1½ ins” means 2″ breadth amidships, tapering to 1½″ breadth at the bow and stern. It’s not an additive measurement (so not 3½″ total).

Is that helpful?
 
Sorry for complicating things but the gunwale could taper like some of your posted sections with 1-1/2” the top thickness and 2” the bottom.

Roger
 
Corporal Smith's analysis makes sense. I thought the same without the help of ChatGPT, which I wouldn't consider an absolute authority, but, in this case, it makes sense. It also makes sense that a bit of "beef" would be added amidships since that's where the boat is most likely to bang up against anything, fendered or not. Also, from a visual perspective, a fair widening matching the widening of the hull is undoubtedly more visually pleasing. The same width bent around the lenth of the hull's curve would look... well... "carpenterish." :D
 
Corporal Smith said:
a) Two different stations — e.g., 2 inches at the midship sections, 1½ inches toward the ends (common in small craft to save weight and because less strength is needed at the extremities).
Click to expand...
Bob Cleek said:
It also makes sense that a bit of "beef" would be added amidships since that's where the boat is most likely to bang up against anything, fendered or not. Also, from a visual perspective, a fair widening matching the widening of the hull is undoubtedly more visually pleasing. The same width bent around the lenth of the hull's curve would look... well... "carpenterish." :D
Click to expand...
Exactly right! Many long pieces of wood on a ship are tapered, including spars. This is because the maximum bending stress is at or near the middle if it's acting as a simply supported beam. If such a member is the same cross section over its entire length it would be either too weak near the middle or too strong (and too heavy) near the ends. A mast acts as a cantilever beam with maximum stress at the partners. Regarding the concept of tapering being visually pleasing, I suggest that this is an example of physics in the natural world affecting aesthetics. Things in nature like tree trunks, tree limbs, and human limbs evolved as tapered to optimize for physics; therefore humans are inclined to see that as normal and pleasing to the eye. Fair winds!
 
Bob Cleek said:
ChatGPT, which I wouldn't consider an absolute authority,
Click to expand...

Quite right. AI ‘thinks’ like us and makes informed guesses so it inevitably makes some mistakes, often hilariously. That’s why I mentioned where I’d got the info.

Curiously, it took a very long time reading all the contracts it could find and looking for patterns in the wording before delivering its opinion. It was at least a minute.
 
Corporal Smith said:
Quite right. AI ‘thinks’ like us and makes informed guesses so it inevitably makes some mistakes, often hilariously. That’s why I mentioned where I’d got the info.

Curiously, it took a very long time reading all the contracts it could find and looking for patterns in the wording before delivering its opinion. It was at least a minute.
Click to expand...
It surprised me too! I've found that it often comes up with some totally off the wall responses to such arcane questions.
 
Hey friends,

AI doesn't know everything. If you want to know exactly, you have to do your own research. AI only ever serves as an aid.

Cheers, Günther! Ship-1
 
The best way to remind yourself of the limitations of artificial intelligence is to ask it to tell you a joke. Humour is one area where it always fails the Turing test.
 
THANKS to everyone who has responded. I LOVE the conversation in general and the responses which are so well thought out.
Allan
 
AllanKP69 said:
Bob and Andy,
Is the below what you are suggesting?
Thanks
Allan
View attachment 537853
Click to expand...

Yes. Ditto to what Andy said. It seems to be the most logical explanation. I'll also add at this juncture that if the part is to be bent into place, the tapering ends are going to make that a much easier task.

I share your enjoyment to the discussion. Learning something new is always fun and it keeps the mind supple as well! ;)
 
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