RM30 and Standing rig size on Tayana FD-12

[phorvati]

Hi, first of all i would like to thank you for answering questions on this forum. I find discussion to be very insightful and full of great information.
I am in the process of sorting out the rig on a boat i recently purchased, FD-12 1980 (50' Tayana). Surveyors recommendation was to replace the rig and chain plates due to age and fatigue. Chain plates are out and rig is fully disassembled so i am not in position to do an incline test to determine RM.
Current wire sizes don't make any sense and i am going through the RM30 calculations from Riggers apprentice to see how to make it right. Any feed back would be greatly appreciated.

All measurements below are imperial.
Displacement is 36k lbs, Ballast 14.4k.
LWL=42', beam is 14.4' but mast to chain plate is only 4.5'

Based on the graph I am at around 105k for RM30
total load on the chain plate would be 105k*1.5/4.5 = 35k lbs.
if i moved chain plates to the gunwale, i would get to divide by 7 and get 22k. That seems like a considerable factor but spreaders would have to be extended.

V1
At the moment, V1 is 1x19ss, 16mm discontinuous on a 7/8"-14 screw/pin turnbuckle.
35k*0.3*2.5 = 26.5k lbs. It seems 304 1x19 1/2" or 316 1x19 9/16" wire would do.

V2/D3 and D2.
V2/D3 is single piece and only 8mm. Also D2 is only 8mm on a 5/8-18 screw/pin turnbuckle. I am assuming this is bad.
Everywhere I read, I see that the same factor is used for these as for V1 so 0.3. Form experience usually D2s are smaller. In the case of my rig going from 16mm to 8mm seems very odd. Any idea why they did this?

D1s
Both forward and aft D1s are 10mm on a bronze turnbuckle with 5/8-18 thread and 5/8 pin. Seems inadequate.
35k * 0.25 * 2.5= 24k lbs. I would go with 316 1x19 1/2" wire, 3/4-16 turnbuckles and 3/4" pin toggles.

In the apprentice book headstay is at 0.3 so i would follow V1 and cap shroud sizes. At the moment its 11mm on a 3/4"-16 turnbuckle and 3/4" pin toggle. Profurl NC42 is on it and I am not sure if getting larger inserts for the foil is possible. 11mm to 9/16.

In the book, backstay and inner forestay is shown at 0.25 so I would follow the D1 sizes, 316 1x19 1/2" wire. Or maybe go with 0.3 factor since the rig seems tall. I=58.67', P=53.87'. This would yield 316 1x19 9/16" wire.
Currently Inner forestay is 8mm and has NC31 profurl. I would have to try and find larger inserts but I fear 8mm to 1/2" or 9/16" is a big step.

backstay is 14mm on a 3/4-16 turnbuckle and 3/4" pin toggle. This seems to be the only stay that is adequate.
Because of the split backstay and where the delta plate is, i would need 3 insulators which appear pricey at 9/16 wire. Any thoughts of going with dual backstay and lowering wire to 1/2" or 7/16" so that I can get away with 2 insulators.

Checkstays share the D1 aft chain plate and those bulkheads are in bad shape, my guess is angle is too steep. Also chainplate is showing stress cracks at the weld. I will consider Spectra for runners and see if i can keep the 0.25 factor.

Thanks very much,
Petar