Ballast Tank w/ Itchy Forearms

[devovino]

SO the last step of my upholstry job is redoing the rear seat, and rebuilding it larger and taller. I had planned on adding a solid tank below the rear seat. In pulling up the floor,and foam, I run into the infamous outer stringer rot at the cross brace which I expected. My plan was to mortise and tenon supports into the existing stringers, to support the rear seat and potentially the weight of the hard tank. My question is.... how much does the exterior stringer add to the structural integrity of the hull? Or are they just there to help hold up the floor. Initially I was going to add a hard tank that was approx 72 x 10 x 48, which works out to be 34560 cu in. which would give me a weight of roughly 800 lbs.Just using the space below the rear seat on the old floor. I had thought about making a box that eliminates the exterior stringers,which would give me more room for ballast, into the area where the foam is in the rear. I would obviousley compensate for the strenght by using stronger material like 2x12 and 2x8's, just thought I would get some feedback or thoughts on this. Better to get the opinions of the masses who have gone before me!

[Salty87]

hi devovino,

the outter stringers obviously aren't as important as the main stringers but they're necessary. that said, i'm sure you can design ballast support that would serve their purpose as well. i wouldn't get rid of them, esp with the extra weight you're looking to carry back there.

[chrisk]

I'm confused about the 48" dimension you have, how do you have room for something that wide back there?

[Okie Boarder]

If you remove any of the outer stringers just under the seat, be sure to add some support back in to compensate. You might consider adding material to the hull and tying it to cross braces that box in the tank. If you tie the tank to the supports and/ or stringers that will make it all one unit too. The thing I would think you want to be cautious of is having that weight back there trying to push down on just the rear of the hull without spreading the load. Kind of think load leveling bars for hauling a trailer. I hope that makes sense.

[devovino]

Well I agree, eliminating the stringers all together would not be a good thing.Especially if I intent to add much more weightback there. I am thinking if I eliminate the outer stringers, I am going to replace with several shorter stringers in the area I remove them from. Measuring the existing stringer, it only seems to be 1in. thick (which makes me think Supra use plywood as they did in many areas) so replicating or increasing the strength will not be hard to do.To be able to displace the weight of the tank, essentialy my thinking is using 2x12 for the front and rear supports for the seat base, and notching them out so they interlock with the main stringers. I will be able to cut out for the exhaust, and be able to slip the 2x12 all the way to the actual floor of the hull. Then connecting the side with 2x8, and a 2x6 in the middle on side to support the middle of the seat. if you follow great, its kinda hard to explain. But I will fabricate the tank out of Aluminum much like the gas tank, it will have flanges around the top perimeter which will attach to the seat base. Well its late I am tired, tomorrow is tearing up the passenger side rear floor and foam. I have found that using a sawzall and cutting the foam into little pieces like a tic-tack-toe board make it managable to remove, also I have been using a post hole digger to remove the foam, its works pretty bad ass.!!!!!!!8)

[Okie Boarder]

An air chisel works pretty good too, with a fairly long spade blade on it.