Bulkhead Thickness

hi all.

need to spec bulkheads for my transom truss for my cat.

i want to bolt ply bulkheads either side of an aluminium truss, somewhere between 9 and 18mm ply i imagine, but what i'm worried about is the bolts crushing light weight wood.

esp over time, the steel bolts vibrating, chafeing and fatigueing the bolt holes in softwood thin ply.

i'm thinking maybe even meranti ply is not good enough fo 40 years of steel bolts moving against the holes
so hoop pine ply or heavier harder timber ply




so the question is,
how thick, and how heavy a ply should i use? (heavier equals harder wood)





onya,
mal



(
cat specs;
3 tons a hull, 21 x 44, aluminium truss 10cmx60cm
)

[Tad]

First of all you need to know the load on each bolt....a realistic load backed up with real experience over time......

Once you know the load you can calculate the required bolting area for a given species using mechanical properties of wood tables....Pay attention to load direction and wood grain direction because wood is not isotropic (of equal strength in all directions) Don't forget a safety factor to account for imperfections in wood. Then pay an engineer to look over your calculations....

First go through this (Multihulls) forum and read every thread on designing and building crossbeams.

thanks tad
thats all i need,

i'll google wood tables and take it from there.

onya,
m