Just noticed something

[Don Case]

In modern woodworking if we are making a beam (like a joist) we put the largest dimension vertically because it has more strength that way. A 4x6" beam would have the 6" dimension vertically. On these ships it's the other way. All the deck beams are on the flat. I just noticed this on the trestletrees and crosstrees, they are wider than they are tall. Makes me wonder when they/we discovered that the other way was stronger. (Well, as long as it was supported sideways )

 

[Don Case]

I was pursuing this because I noticed that Dan Vadas' trestletrees on the Vulture look deeper than they are wide. His crosstrees are still on the flat though. I got my dimensions from Anderson's 1600-1720 rigging book and that precedes my Discovery and the Vulture by 50 years. I looked in all my books and most of them show the trestletrees on edge but that may just be because the artist was from the 20th century. Does anyone have any ideas about this? Maybe the trestletrees are deeper because they have to be notched for the crosstrees.

 

[Don Case]

I found a post on MSW by DR PR where he gave the trestletree dimensions from 8 different authors, and they all have the width greater than the height.

 

[Kurt Konrath]

Could the difference in direction of the strong side, be based on difference of stress being applied, latterly versus vertically, most ships don't suffer from huge vertical loads, as they do from longitude and latitude loads on the hull and decks to hold shape.

 

[Don Case]

Yes, that could explain it. The biggest load on the top, for example, would be from the topmast stays and that would be sideways. Deck beams would be subject to loads kind off diagonally across the deck. Yeah, I think you nailed it, thanks.

 

[Encre de Chine]

... also it could be linked to the need to bend the beams for deck camber.
Putting the beams upright and cutting the camber would weaken the structure and increase work and waste

 

[Donnie]

Don,
very good observation - I never even thought or even occurred to me. But, it seems to me at least the Trestle-tree(s) are oriented with the widest vertical (??)
As far as the Beams go, again that is a good observation as well. Good thinking !!!

 

[ChrisP]

the misunderstanding stems from the word "beam". In a structural engineering context a beam supports the weight from above. Correct term for the horizontal pieces of a ship's structure would be "cross-member". Similarly a stiffening (and non-loadbearing) member in a building structure is not referred to as a beam.

 

[Don Case]

Thanks guys. I've learned something today

 

[Signet]

I'm certain they knew which way was stronger. But vertical height either decreases the headroom between decks or increases the overall height, neither of which is desirable. And frames constituted the majority of the length of the ship; that is, there are more beams than open space, meaning vertical strength near that of a huge, continuous beam near 3/4 the length of the ship. So they have a very strong vertical strength as well. Add that to other bracing, diagonal and otherwise, and the structure is very robust.

 

[Stuart Little]

It just shows what we take for granted, I'm in the process of converting Bounty's full size mast top dimensions to 1:50 scale (mm), so I took a closer look; the fore lwr. top crosstrees are 5.5" w x 3.625" deep, the tresseltrees are 5.5" w x 8" deep. We all learn something every day.