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PostPosted: Wed Jun 27, 2018 8:47 am 
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Old boats break down over time and the signature crunch sound is a sure indicator of delimitation. But how much flex is normal? Are the hulls truly rock solid on new hobies? Or is there a slight flex 1/16 to 1/4 of an inch to be expected on the larger surfaces? Is an older boat that flexes but has no crunch sound delaminated or is it just fine?


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PostPosted: Thu Jun 28, 2018 1:17 am 
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Location: Opelika/Lake Martin, Alabama
Of course, when you have two hulls connected together, there is going to be some sort of flex. My boat is an 84 model. When it is sitting on the trailer and I lift up on one hull, sure, it has some flex, or give, until the other hull lifts, but it isn't much and I dont make a practice of it either, I would imagine that is putting undue stress on the connections that hold the whole thing together. If your boat has a lot of flex, there are methods of tightening it all up by gluing specific parts. I am not concerned with the little flex of mine because it's pretty tight anyway, and I'm not racing so, I really dont care about a little flex. Solid hulls, little flex, okay with me. That being said, I would expect an older model would definitely have some flex to it especially if it has been sailed hard. It's to be expected. Glue it or shim it if you want to diminish any flex.

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PostPosted: Thu Jun 28, 2018 7:41 am 
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Location: Jersey Shore
I would say 1/16 - 1/8” of flex on the broad hull surfaces is normal when pushing down moderately hard. New boats are quite rigid, but some flex on older boats is acceptable and doesn’t mean the boat is going to disintegrate.

The most important areas to keep an eye on are right ahead of the bow (deck and hull) and the inside of the hulls between the crossbars (the areas of the hull where you would stand when righting).

sm


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PostPosted: Thu Jun 28, 2018 10:30 am 
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Okay, I am unclear here. Are you talking about flex at the trampoline frame or pylons, or are you talking about the actual fiberglass? I was talking about crossbar/pylon flex.

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1984 H16 Yellow Nationals Redline, "Yellow Fever"
Lake Martin, 'Bama.


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PostPosted: Thu Jun 28, 2018 11:04 am 
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I was referring to the fiberglass itself, specifically in regard to determining delimitation of the hull or just "normal" flex of the fiberglass. Although the total flex of the frame and pylons are important to know.


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PostPosted: Thu Jun 28, 2018 12:26 pm 
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Another way of checking for delamination is to use the “coin tap test.” This simple test is actually commonly used in the composites industry.

Hold a quarter between your thumb and first finger. Then rap the edge of the coin against the hull rapidly. If you hear a nice crisp note, then the composite is good. If you hear a dull thud, then you have delam.

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PostPosted: Thu Jun 28, 2018 12:30 pm 
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Joined: Wed Aug 08, 2007 10:20 pm
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Location: South Boardman, Mi
You will know a soft spot when you find it.

It will likely be much softer than the surrounding area, and the gel coat may be cracked around the perimeter of the damage.

Whereas normal hull flexing is generally not localized, and the stiffness of an area on one hull is equal to the same area on the other hull.


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