engineering student? first off, don't overthink it. this is the way a H16 is rigged. end of story. but since I also have a tendency to overthink things......



if that tang pulls out you'll have more to worry about than a MOD. but the tang won't fail. the tang isn't under any more appreciable load than without the trapeze. it's the shackle that experiences the change in load.



think through the free body diagram of the shackle.... the leeward shroud is generally slack, so ignore it. there's the tension of the headstay, which is countered by the tension of the mainsheet/sail/rig. there's also the tension of the windward shroud. all of these tensile forces are resisted by the compression of the mast. the tang transmits the rearward tension of the rig and the compression of the mast.



now add in the tension of the trapeze, assuming that the crew is trapped out amidships..... the load of the windward shroud is reduced, since this acts in basically the same direction. the load of the headstay increases slightly to accommodate the additional rearward pull of the trapeze.

There is some additional compression in the mast which is transmitted through the tang, but a couple of hundred pounds of crew doesn't matter much when it's already under a couple of thousand pounds of simple sailing stress. I suppose there's also some torsional stress caused by the eccentricity of the rotatating mast, but it's negligible. furthermore, this added stress on the tang's fasteners is fundamentally shear stress, not tensile stress. they'll be fine.