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Jon and V Boat Conversions & Modifications
16' V hull FINALLY DONE!....for now 3/17....see final POST.
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<blockquote data-quote="Rat" data-source="post: 109470" data-attributes="member: 1914"><p>Tacoing {image of boat folding in half while underway} is a bit of a misnomer as well as, we tend to describe things in extremes. What usually happens when you remove the lateral support is "localized repetitive flexing" IOW you have a very small area that is prone to intense, repetitive flexing that will eventually lead to metal fatigue and failure. Riveted hulls are designed to flex, but the flex is engineered to be over a much larger area which keeps it from being either repetitive or localized. The two most common failures I have seen from side panel flexing are:</p><p>1) A crease or crack forms in the bottom of the hull in one of the lateral ribs very close to the longitudinal center line of the hull</p><p>2) A crease or crack forms in the bottom of the hull in one of the lateral ribs very close to the chine, usually accompanied by one on the opposite side.</p><p></p><p>I think these two stress fractures have different causes, but are both as a result of side panel flexing. In the first instance i think it is a trailering issue mostly and in the second caused when underway in heavy to moderate chop. </p><p></p><p>An easy way to check is to establish a baseline before you remove anything structural. I have used an old pull scale and ratchet straps to figure it out. Measure the beam at the sheer line of your hull, attach the scale and ratchet strap across the beam, tighten the strap until you have 10 pounds of pull on the scale, then measure the beam again. This will give you an amount of deflection for an amount of compression. Then you can design a brace system that will allow you the same results or, if you want to, go to a higher amount of deflection or compression. </p><p></p><p>For example, you have 2 inches of deflection for 10 pounds of compression. But, after you have removed the seats you can easily tell that maybe 4 inches at 10 pounds will be okay, then you can design to that. At least you have something to go back to if it all falls apart (not literally) or you want to change a design element.</p></blockquote><p></p>
[QUOTE="Rat, post: 109470, member: 1914"] Tacoing {image of boat folding in half while underway} is a bit of a misnomer as well as, we tend to describe things in extremes. What usually happens when you remove the lateral support is "localized repetitive flexing" IOW you have a very small area that is prone to intense, repetitive flexing that will eventually lead to metal fatigue and failure. Riveted hulls are designed to flex, but the flex is engineered to be over a much larger area which keeps it from being either repetitive or localized. The two most common failures I have seen from side panel flexing are: 1) A crease or crack forms in the bottom of the hull in one of the lateral ribs very close to the longitudinal center line of the hull 2) A crease or crack forms in the bottom of the hull in one of the lateral ribs very close to the chine, usually accompanied by one on the opposite side. I think these two stress fractures have different causes, but are both as a result of side panel flexing. In the first instance i think it is a trailering issue mostly and in the second caused when underway in heavy to moderate chop. An easy way to check is to establish a baseline before you remove anything structural. I have used an old pull scale and ratchet straps to figure it out. Measure the beam at the sheer line of your hull, attach the scale and ratchet strap across the beam, tighten the strap until you have 10 pounds of pull on the scale, then measure the beam again. This will give you an amount of deflection for an amount of compression. Then you can design a brace system that will allow you the same results or, if you want to, go to a higher amount of deflection or compression. For example, you have 2 inches of deflection for 10 pounds of compression. But, after you have removed the seats you can easily tell that maybe 4 inches at 10 pounds will be okay, then you can design to that. At least you have something to go back to if it all falls apart (not literally) or you want to change a design element. [/QUOTE]
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Jon and V Boat Conversions & Modifications
16' V hull FINALLY DONE!....for now 3/17....see final POST.
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