New Rigging for a former fishing boat (built 1936)

Hello, Fellows !

... got a job from my boat neighbour to prepare a former fishing boat (built in steel in Netherlands) to a gaff rigged motor sailor.

So far the first checks showed, it seems possible, the owner had bought 2nd hand wooden mast, of 9.90 meter height. As the wheel house roof is around nearby 2 meters above deck, the mast is anchored in a welded metal case with a joint the main boom can swing free above the wheel house, very typical in Netherlands to lay down the mast quickly with all the bridges.

The ship is of 17-18 meters long, 4.50 m width, and weights around 20 tons ...

The owner made the mistake to use just one single shroud on starboard and backboard side, without any aft stay. I suggested him to reset the standing rigging for stabilizing the mast safely.

The wooden mast, I suppose originally from a Dutch flat bottom ship (e.g. Lemster Aark or Tjalk), has no Saling. So we cant attach lower, intermediate or cap shrouts.

The idea now is - because of the given geometry - to use "kind of" two lowers, Fore- and Aft-Lowers, - without back stays. The lowers shall be connected via terminals with chain plaits which will be welded on the side walls of the fishing boat.

Can you give some hints pls about the configuration of the stb/bb shrouds, angle of attack to the mast top, distance between and dimensions of the chain plates ?

What is the distance between this fore- and aft lower shroud on the level of the attachment points of the chain plates ?

Are there any calculations or tables available to get the right measurements and get it done well with the best angle of attack to the mast top ?

Tks in advance for your feedback.

Greetings from NL
JR