Re: [PSUBS-MAILIST] Curved surfaces and ballast release

Rick,

I hear you, lot's of similarities. I am envisioning the longitudinal supports (minor stringers) only to maintain a fair surface since the framing is in essence, a plug. Still, I would like to not have to do that, but I cant see how to laminate the thin layers without them?

But, longitudinal support (major stringers) in addition to the monocoque skin is also length and weight dependent is it not?

'Now, I may be a little more concerned with the cockpit. I'll have to think this one out."

Any ambient ply design is going to need a "boatload" of lead. You and I need to be careful about structural integrity with regard to the concentrated ballast (and it's going to be a lot!). I don't think I could get away with purely monocoque at my length and be comfortable in any kind of wave action.

As I work this out on paper I am seeing either a short, squatty and lighter caricature of a military boat, or a longer truer to scale but more heavily constructed version with a tiny crew module and almost all flooded fairings. As they say in Texas, "big hat no cattle"!

Truly a lot of details to consider.

Joe

From: "Rick and Marcia" <empiricus@telus.net>
Reply-To: personal_submersibles@psubs.org
To: <personal_submersibles@psubs.org>
Subject: Re: [PSUBS-MAILIST] Curved surfaces and ballast release
Date: Sat, 17 Dec 2005 12:13:00 -0800

Joseph - it seems we're looking at building the same boat!!!

I'm avoiding longitudinals and sticking with a monocoque. I agree with all the transverse frames (bulkheads) being the main support or guides for the epoxied skins. Magical Child (i.e.: Typhoon) will have simple curves (arcs) both port and starboard, deck and bottom. The simple curve in the cold moulds will be sufficient support; IMHO, the longitudinals are extra work. Longitudinal strength comes from the skin.

Now, I may be a little more concerned with the cockpit. I'll have to think this one out.

Temporary support while the epoxy cures along the bulkhead edging will come from wrap-around straps or even cinched up rope (trucker's tightener). A good 60 grit sanding along the bulhead edging will give some tooth for the epoxy to hold.

I'll be using rather thin (1/4 inch) ply for bulkheads - should work as long as they're filleted with epoxy and glass strips. Cockpit bulkeads will be heavier.

Rick L

----- Original Message -----

From: Joseph Perkel

To: personal_submersibles@psubs.org

Sent: Saturday, December 10, 2005 6:14 AM

Subject: [PSUBS-MAILIST] Curved surfaces and ballast release

The recent discussion regarding spherical mock-up construction has me taking another look at something I had in mind.

To form the curved surfaces of my ambient marine ply design, I have in mind epoxy laminating thin layers of ply over longitudinal supports notched into traditional transverse frames. I need those frames to baffle a whole lot of free flooding spaces and soft tank spaces anyway, so they have to form the hull exterior. (The crew compartment is modular and hidden from view and structured to contain the lead ballast).

As I apply this to my 3d model, I see a lot of material taking up a a lot of displacement volume and therefore requiring additional compensation ballast.

Suggestions on how to cut down on the framework volume and still maintain fair curves with rigidity would be greatly appreciated.

A second question is regarding mechanisms for release of a heavy lead keel. If someone could point me to examples to look at?

Joe

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