Bow sections laminate

30boat

30boat

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I was at a marina in Spain last weekend and having nothing better to do and remembering the recent thread on a bow that fell off I went about knocking on the bows of the (unoccupied) yachts on my pontoon.It amazed me that a well known make gave off a very thin sound and could be pressed in with two fingers right before the stem.I then moved on to a French model that felt a bit thicker and more rigid but not by a lot.A 90s Italian boat was wood like in stifness .Hardly scientific I know but at least to me very enlightening.
 
Be careful. I crew on a boat that has a false bow made of foam which is just filled & painted. You really could press it in with two fingers, but the owner might consider hanging too good for the culprit.
 
I'd be very wary of drawing conclusions about the boats' seaworthiness from this.

I'm speculating here (in keeping with the nature of this thread). Not all the hull has to be equally thick to take the rig loads. The bow is an area of the boat where the builder would be looking to save weight, and the laminate could well be very thin there - but that doesn't really imply the boat is flimsy - it may be that it has extra reinforcement along certain points to efficiently take the loads (i.e. along the gunwhales, and up the stem), rather than having the entire bow area thicker than needed.
 
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sighmoon said:
I'd be very wary of drawing conclusions about the boats' seaworthiness from this.

I'm speculating here (in keeping with the nature of this thread). Not all the hull has to be equally thick to take the rig loads. The bow is an area of the boat where the builder would be looking to save weight, and the laminate could well be very thin there - but that doesn't really imply the boat is flimsy - it may be that it has extra reinforcement along certain points to efficiently take the loads (i.e. along the gunwhales, and up the stem), rather than having the entire bow area thicker than needed.
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I agree,that's why I didn't name the boats.I can't believe these yards will skimp dangerously on materials and indeed bows do not fall off on a regular basis.My point was that ,as noted on the other thread ,laminates can be quite thin where you'd think they wouldn't be.
 
Thinness At The Bow Is Not An Issue

Most of the forestay stress is straight down the stem, along the keelson and into the keel, the shroud chain plates stress is down the hull (localised) to the keel, the back stay stress is down the stern along the keelson and into the keel.

In simple terms the rest of the hull is just filled to keep the boat afloat i.e. it does not contribute to the stress distribution if the keelson, stem and stern is stiff enough. On some very light yachts a frame exists which triangulates the mast support and stay anchors thus eliminating the hull from any rigging stresses.

So thinness on the bow immediately aft of the stem is likely not to be an issue on a properly designed yacht with a stiff keelson, stem and stern. The loads dont go into the bow. If there is flex in the keelson then minor compression loads could be transmitted into the laminate of the bow which are resisted by form stiffness e.g. a brick balanced on a cardboard loo role tube.

After that thread about the bav bow failure I looked up some design information and the above is a very amateurish summary.
 
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