aluminium thickness to prevent plate buckling

[rasorinc]

Well you could define a strip most subject to damage and fit a piece of Corrugated to take the blows. PS looks might be a problem.

 

[myark]

Hello,

I'm currently designing a 22m aluminium explorer yacht with a bare aluminium hull.

The topsides of the aft half of the hull are completely planar and I'm worried that the hull's skin will start buckling as fenders and dinghys will apply pressure. (see example in picture attached)


The idea is to add some one-directional curvature to the skin (retaining developable surfaces for easy of construction) to give the plate some additional form stability.

Is there any data available for how much radius I need for a given aluminium plate thickness to withstand a certain normal force?

Hope someone can help!

From the look of the boat shape there is not much curve to be added so the simple answer is you do not to need to go thicker plate but add a series of stringers, say 4mm X 75mm in the regions you believe will be knocked with out side force.
An example of a 10.m Myark folding trailer barge is a 4mm 5021 tread plate aluminum deck, with a 13 ton digger load on top which I placed 4mm X 60mm stringers 100 m apart and did not leave any damage with a 13 ton load on top but maintained the lightness I needed to be legally towed on road.
I did place a 5mm hull bottom but that was because of a sharp object may puncture the hull when the ocean tied would go out leaving the barge sitting on top of rocks with weight on top need extra strength.
The picture of barge weight is under 2000kg folded in trailer form.
Many people think a thick deck solves plate from a sailing shape, and place few stringers that will still make a sail shape in the panel when load on top and is not the answer as the answer is making it like the door of a house where they have cardboard stringers or honey comb shape cardboard close together that makes the thin panels very strong but also very light and low cost.

 

[Armada01]

Ok, thanks to all of you for your input!

 

[Bendigonian]

Just as an afterthought for anyone finding this thread. Research into transitory pressures generated by hull slamming, (search for 'Tests on Yacht Hull Plating -SNAME'), seems to indicate that curvature in one dimension may help in structural strength, but sometimes can actually reduce plate resilience. Buckling in single curved surfaces can occur at a much lower pressure than deformation of flat plate.
Compound curvature helps a lot but at a large increase in construction complexity.
They also report that while ply and GRP don't deform as much, or as plastically, this is often at the expense of potential frame and stringer damage and de-lamination; the slamming energy has to go somewhere!
This may explain the 'hungry-horse' look of some aluminium work boats. Even 'tho the frames and stringers are up to spec, 4 or 5mm plate may be thick enough for structural strength but maybe not be for sufficient stiffness to withstand transitory slamming pressures and still remain fair.
Possibly the only answer is to decrease the spacing between stringers, and also increase stringer width, beyond what is required in the schedules. Another option is to go the 'Strongall' route and massively increase plate thickness and do without most stringers and some frames. Haven't seen any hungry-horse Strongall examples, or welding distortion. Think 15mm hull bottom plates, 12mm hull sides and 10mm deck plates on a 14m hull. Icebreaker country!!