Re: [PSUBS-MAILIST] Lengthwise internal supports

Stay with "T" rings and think about placing them on the out side, this is a standard procedure in most submarines. The ring web can be cut from plate in half and quarter circular sections and welded together than roll the flange and weld it before you slide it over the pressure vessel. If the welds are good it wont make much difference. And it makes the welding much simpler if the stiffeners are out side and has virtually the same effect. Longitudinal stiffeners add little to nothing when placed in a cylinder and will collapse. The plaiting of the cylinder will compress as you dive and the rings allow for an even distribution of pressure as the outside plating stretches. Longitudinal stiffeners create uneven stress around the cylinder plating and it will fail as it buckles in. It's a pressure vessel thing. The rings on the out side also allow for more room inside and you won't bang your head as often and they facilitate hanging all your stuff like batteries and tanks. Forget the longitudinal stringers, they have a place on steel boats but not in small submarines. Dave

Cliff McDonald <cmcdonald@applikonusa.com> wrote:

Hello psubbers,

I?ve got another mechanical engineering question for you:

I?ve been trying to think of a way to simplify the internal bracing on a cylindrical pressure hull. The ?T? rings that are commonly used for internal stiffening seem to be a difficult part to make and I can?t find a good (cheap) source for them. There are plenty of fabricators that would love to make several of them when I?m ready but the cost for this is greater than the total cost of a rolled cylinder and the endcap / bulkheads (which I can fab myself). I could reduce cost by cutting small sections of the ?flat ring? portion out of sheet steel, and try to roll the bands myself but this is going to take a lot of cutting, welding and piecing together. I think the total strength of a pieced together T-stiffener would be compromised as well.

Has anyone ever run the majority of internal bracing lengthwise through a cylinder? Since the main portion of the pressure hull is a straight cylinder, it would be pretty easy to run some ordinary channel or angle iron the length of the cylinder. Spaced about a foot apart and with internal bulkheads spaced at reasonable distances (for example, one bulkhead centered in a 48? OD by 96? long cylinder), I think this would be as strong as T-rings spaced every foot. It would be much easier to build and weld, should reduce flexing and twisting, and would make length wise tubing and wiring runs tuck away a little neater.

Thoughts?

Thanks and Kind Regards,

Cliff McDonald

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