Topmast crosstree dimensions.

[Bluto 1790]

There is no indication in any of my plans/drawings as to the length of the topmast crosstrees relative to the width of the equivalent lower mast top.

So, in order that my question is clear I've inserted a picture below.

Can anyone give me a formula to calculate the topmast crosstrees for each of the 3 masts please?

I don't want to just bludgeon ahead and make them to the dimension that "I think" they might be - - - I'd rather they were more accurate than that!

[Mark P]

Greetings Bluto;

 

In Lees' Masting & Rigging,  he gives the length of the topmast trestletrees as 3 3/4" to every foot of the topmast's length;  the depth as 1" to every foot of the trestletree's length;  and its breadth as 2/3 of the depth.

 

For the crosstrees,  these are 1 2/3 of the length of the trestletrees;  the depth is 7/8 of the trestletree;  and the breadth is as the trestletrees.

 

My only caveat is that in his illustration of the topmast top,  the crosstrees don't look as though they are as deep as 7/8 of the trestletree,  more like about 3/4. 

 

All the best,

 

Mark P

[Bluto 1790]

Hi Mark,

 

Thanks for your input. As I said, my plans don't show any dimensions for the crosstrees -- only a vague indication as to the length of the trestletrees. See the pic below >>>

In that drawing, (which is at a scale of 1:160) the best measurement I can get of the trestletrees is around 7.5mm so I have to double that to get to the scale I'm working at and that gives me 15mm. So, on the basis of your info above, one and two thirds times that would bring it to 25mm for the crosstrees.

The top for the mizzen mast measures about 50mm across so that would make the topmast crosstrees about half of that - - - would that be about the correct relative proportion?

 

(In case you're wondering why I'm working at twice the scale of my plans -- I'M NOT ! . . . it's just that the drawings of the standing and running rigging are only at HALF of the scale of the rest of the ship. It's a bit of a bummer now that I'm at the rigging stage as I have no previous experience so I have to ask questions here, or rummage around in other build logs trying to see if I can get hints and answers there.)

 

Jim.

[Mark P]

Hi Bluto;

 

In your rigging drawing the topmast trestletrees appear to be about half the length of the lower ones.  It would therefore seem reasonable that the trestletrees should be likewise.

 

Lees states that from 1769 the lower tops were 1/3 of the topmast length in their athwartships dimension,  and 3/4 of that for their fore and aft dimension.

 

All the best,

 

Mark P

[JerseyCity Frankie]

Here is how I THINK you can arrive at the dimension you're looking for: look to the t'gallant shrouds, these are the ones that pass through the tips of your crosstrees. If they were to continue down to the hull on a mathematically straight line-after passing through the tips of the crosstrees- they would hit the channels on the same for-and-aft line as all the rest of the standing rigging lower deadeyes on the channels. So the imaginary line I'm describing is the Hypotenuse of a right triangle that uses the mast and the deck as the other two legs. You should be able to make a simple diagram using tracing paper over your plan, OR measure off the model itself if you have the mast components ready and you can measure them.