chainplate calculations for a jordan drogue

[HappySailor]

Originally Posted by asdf777

If somebody could verify my calculations for jordan drogue chainplates, it would be really great!

The boat is 30' sloop, 8600 lbs official displacement, but probably around 9,500-10,000 lbs fully loaded.

I'm thinking of the following:

1.5" x 0.25" x 12" with a 1/2" hole and 4-5 bolts. Crosby 7/16 209a shackle - the pin is 1/2". WLL ~= 6000lbs. The chainplate strength should be:

(1.5" - 1/2") * 0.25" * 30,000 lbs/in^2 (tensile strength for 316 without yielding) = 7,500 lbs.

Does it look right?

Many thanks!
Gleb

In a simplistic world yes...
But...
This is pure tension, statically loaded... You start adding dynamic flexural fatigue, take into consideration the stress induction of the pin hole, mounting holes, area reduction for chamfering, etc... maybe 2/3 of the 7.5klbs. Now don't forget your FS, 1.5x Together reduces the load capacity to = 3300 lb...

Of course this is overkill reduction wise but...