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Blocks and Tackle and How Are They Measured

Kurt Konrath

Kurt Konrath

Kurt Konrath
Joined
Feb 11, 2020
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Location
Oklahoma City OK
OK, looking for help from some more knowledgeable members than me.

I have had this question many times and now see others struggling with it.

So when we say a block is single, double or triple, that is not hard to understand, but when they say a 2mm block, is that height, or width, and if so, how is it measured, from top to bottom of block body or from size of the wheel inside the block?

Any help or guidance welcome for us novice builders.
 
I agree with YT. I am no where near my books for a while so cannot get at the details, but I am pretty sure it was standard operating procedure to use ratios on the three dimensions of the block and the sheaves based on the circumference of the rope.
Round numbers
The length of the block was about 3X the rope circumference
Sheave diameter 2/3 the length of the block
Block Width: Approximately 2/3 the length of the block
Block thickness (single blocks) approximately 1/2 the length

The hard part for me was finding the rope circumference until about 25 years ago. The most complete source I have ever found to date are the formulas from main mast to ropes in James Lees' The Masting and Rigging book. There are other sources, but not as complete as Lees' work considering the changes that took place over about 200 years. His book is for English ships from the mid 17th century to the mid 19th century so may not be applicable for other nations.
Hope this helps.
Allan
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So then a 2mm block is measured by the external height of the block.

That is what I thought, and hopefully this will help others who have the same questions.

Thanks all for helping to clarify for sure how this is done.
 
Kurt Konrath said:
OK, looking for help from some more knowledgeable members than me.

I have had this question many times and now see others struggling with it.

So when we say a block is single, double or triple, that is not hard to understand, but when they say a 2mm block, is that height, or width, and if so, how is it measured, from top to bottom of block body or from size of the wheel inside the block?

Any help or guidance welcome for us novice builders.
Click to expand...
For me blocks are measured in "Dammits" It is a scale in which the smaller the block the more the Dammits as I try to thread a line through it.

Rob
 
Rob444 said:
For me blocks are measured in "Dammits" It is a scale in which the smaller the block the more the Dammits as I try to thread a line through it.

Rob
Click to expand...
Well at least that word won't fill the swear jar as full! If that is what you say when you thread a needle thru the eye and stick your finger, or drop one on the floor never to be seen again, and it the last one you had, as I speak from experience. :D
 
It's a good question. I have had a couple of people buy 1.7mm blocks, which are about the size of a poppy seed, who clearly wanted something considerably bigger. With one exception all of mine are the top to bottom height measurement of the block. The exception are open hearts. Because these are essentially a closed heart with the narrow end chopped off, and often paired with closed hearts, I name them the same, even though their actual height is quite a bit shorter.
 
Geeze! I just about have the sizes of the mast parts figured out,(all proportional) and now you throw this in the mix. I wonder why Crothers didn't cover this in one of his books? I haven't seen anything in the two books that I have about block sizes at all. I am also looking for info on door sizes on the weather deck. The deck house walls are all 6" 6" high but there is a 12" wall across the opening to keep water from entering the cabin. That leaves 5"6" with no jamb at the top. Were all the sailors only 5" tall? Ya gotta have a door jamb don't ya? I also don't see how the roof was built either. Lots of "Dammits" in this build.
 
not sure if this will help, but I made a spreadsheet and posted it here a while back.

Rope diameters for Block attachment

I have just completed the wood construction phase of my first ship build and now getting prepared for the Rigging Phase... Is there a chart out there that indicates correct rope size for rigging the various blocks (seized to eyebolts etc) - looking for rope diameter specifically? I'm able to...
shipsofscale.com
 
Yes, blocks are measured on the longest side. Top to bottom like Ismaele posted. I just confirmed this www.woodenmodelshipkit.com because I might be low on blocks for my current kit. Measured in millimeter or sometimes fractions on various supply sites.
 
Mikeyt said:
sewing needle threader
Click to expand...
Those are fine for most block sizes but too large for micro-blocks i.e. less than about 3mm, where the hole is only about 0.5mm. I expect most people on here are familiar with the following method but it may be handy for those who aren't;

Run the first inch of the end of the thread through a small pool of medium CA glue. While it's still wet, roll it between finger and thumb, pulling it longways at the same time. Keep rolling, rolling, rolling until dry or your fingers will get stuck. You're aiming to make a thin stiff rod. Once dry, with a sharp blade cut it diagonally against the lay. The aim is to get a nice sharp point so the more acute the angle, the better, within reason. Provided the rope is small enough for the block, it'll now go through easy as pie.
 
There is no rule that says that you can’t open up the hole in the block a little. A wire sized drill or even a needle mounted in a pin vise.

I don’t use CA glues. A dab of clear nail polish or shellac is a less noxious choice.

Roger
 
The needle threaders I use are the ones with an wire with an aluminiumtab and the threading wire is .0004. I also have a threader which has a plasitic handle about the size of a nickle with a thread cutting blade it and a threading wire that is .0002, these are both in inches, the smallest drill I have is #80 which is 0.04". threrfore there is no problem a thread and the 0.0002" wire through min The wire in the plastic housing sizes @ 0.011mm Mikeyt
 
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