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Bertram31.com General Bulletin Board
Re: New Tank Installation ? More Support *LINK*
Posted By: Mike Dolan In Response To: Re: New Tank Installation ? More Support (Joe j)
Date: Thursday, 29 June 2006, at 9:30 a.m.
Guys,
The LightningShack tank was actualled foamed in place.
It was a while back, so I'll do my best to recall my rationale.
I'm sure you could make a strong argument for other approaches, but if this rationale doesn’t help, well it can’t hurt.
To properly restrain a mass of this size under the inertial and impact forces it will see crashing through waves would require extremely robust restraints. Having fixed mechanical bracing strong enough to restrain the tank from these loads, yet still providing enough degrees of freedom so that the tank doesn’t experience strain while the hull is loaded and flexed seemed to challenging to me. (Not to say, that it can't be done)
I felt that Pascoe's procedure was not entirely suited for a tank of this size. The weight is so heavy that I didn't feel that the glue on the tabs would do an adequate job of holding the tank in place. The overall length is to long to expect a good weight distribution over the tabs, especially when you consider the rigidity of the tank as compared with that of the flexing hull.
The foam bedding allowed me to evenly distribute the weight over the hull. The tabs on the bottom were imbedded in the foam which prevents the tank from moving forward or aft. Any load that is transmitted through the hull to the tank is dampened by the foam interface, insuring that the tank is not strained in any unexpected ways.
I followed Capt’ Pat’s suggestions and encased the tank in plastic before filling the void with foam. This plastic prevents the foam from sticking to the tank, this way tank replacement or maintenance is possible without re-foaming and the associated clean up. After foaming I then removed the tank to remove the plastic, while the tank was back out I knifed some grooves in any of the low spots in the foam so that water can’t get trapped near the tank.
The compromise I made was on the corrosion liability, as the tank is not totally encased with air. I felt that this was unlikely to be a real problem because of the very thick Devtar coating I applied. I also felt that this tank was easy to replace and inexensive to fabricate, thus a 10 year replacement shedule should be implemented anyway. That is if Diesels don't find there way onboard sometime before that, and with Gas prices this the way the are, this is looking like the only way to go.
Good Luck
Mike DolanAnyway
Hope this helps.
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