Origami Metal Boat Construction

[bangkaboat]

Originally Posted by SaltyMonkey

... And the only thing that bothers me about the design is the welding at the bottom of the V, but that may be mute because the weld should be stronger than the steel itself.

Please correct me...

"...the weld should be stronger than the steel itself." Please elaborate, Kim(?).
Mike

[DeepFrz]

A tank can't be taken as a structural member in that case since it is under the fulcrum (hinge) of the end of the frame. These frames should have been reunited and braced together by a floor.

I think Daniel's training and experience should lend a great deal of credibility to his words.

DeepFrz - on the other thread we just discussed that these days best practice is to not have them integrated. Granted, this is probably from an older design of Brent's

That may or may not be true but I still bet that most metal boats (pleasure boats) being built today are built with integral tanks. Can you cite a reference? I know that 2 of North America's premier metal boat builders incorporate integral tanks (fuel, not holding tanks and am not sure about water tanks). Waterline yachts builds with steel and Kanter boats builds mainly with aluminum, but also in steel. I believe that Kasten specs. integral tanks in his designs as well.

[SaltyMonkey]

The Mild steel will most likely stress and fracture before the good weld will (ER70S-n).

[SaltyMonkey]

DeepFrz - Why dont you go read the end of this thread?

http://www.cruisersforum.com/forums/...-41747-29.html

[bangkaboat]

Originally Posted by SaltyMonkey

The Mild steel will most likely stress and fracture before the good weld will (ER70S-n).

Well, assuming that you are able to lay in good welds, while pulling the hulls together, the welds should be close to, maybe even as strong as, the parent metal. Stronger? No. But, one should really qualify the use of the term "stronger" as it is often erroneously used in such forums to describe any, or all, of a material's physical and mechanical properties. Using GMAW? As good a choice as any, provided you can tell a solid weld from swiss cheese when you are laying it in. I've seen welds that looked good on the face, like an aero bar below the surface. If I recall, correctly, kmorin & Murielle(M&MOvenden) are on these forums and each built/build with solid wire. Wynand may have, as well.
Mike

[SaltyMonkey]

Can we get back on topic? This is floundering....

[bangkaboat]

Originally Posted by SaltyMonkey

Can we get back on topic? This is floundering....

"Origami metal boat construction" Looks like the right topic to me. Unless, of course, the intent is to sell Brent's plans, not discuss the construction of his boats in comparison to more traditional designs(The thread title doesn't specify). If the latter, discussion over the centerline weld & how the hulls are pulled together seems valid. "floundering" lol, one word you don't want to hear on a boat forum!

[anjou]

When you have a fold at such a shallow angle, you need to add a member on the third side to triangluate and therefore deflect compression loads, and also to redistribute tension loads
.
Always think of creating angles, no matter what you build. Roof trusses, aircraft wings, fusilages, bridges, etc

Originally Posted by SaltyMonkey

Ok, let me reflect some of this back to you.

The two portions of the hull are welded into a "V" = "\" + "/". To strengthen the two sides of the hull together you need frame portions and bulkheads - one side welded to "\"...the other side welded to "/" of the "V".

To keep the frame reinforced you are saying that a floor is necessary - like a stringer between frames? And the tank is not proper structurally for the job?

But, a tank is not taking up the complete hull, so I don't see how a tank is the issue here throughout the complete hull?

And I don't see how a floor really adds that much structurally to the design.

I do question why a tank is integrated into the design and its purpose, but that's not so much an engineering issue as a maintenance one. And the only thing that bothers me about the design is the welding at the bottom of the V, but that may be mute because the weld should be stronger than the steel itself.

Please correct me...

[dskira]

Originally Posted by SaltyMonkey

So what does the 3/16 PL on Brent's sketch indicate? Looks like a floor to me

No it is a cover plate on top of the tank.
Look very attentively the other design where it say: floor.
I know the arrow can be confusing since it show only the top of the floor. the arrow refer to the whole triangular plate going from the arrow to the keel.
As you can see the floor is not horizontal, it is a vertical plate from one side to the other side of the hull.
Daniel

[DeepFrz]

DeepFrz - Why dont you go read the end of this thread?

Talk about floundering. I don't see how that thread addresses this issue at all, although I'm not going to read it all. Seems like a good discussion on welding steel boats though.

[SaltyMonkey]

Originally Posted by anjou

When you have a fold at such a shallow angle, you need to add a member on the third side to triangluate and therefore deflect compression loads, and also to redistribute tension loads
.
Always think of creating angles, no matter what you build. Roof trusses, aircraft wings, fusilages, bridges, etc

Yes, but isn't a solid triangular frame acting in this capacity? It's basically an upside down roof truss that's been filled in by king posts. You don't need a welded in "floor" connecting these frames to support the sides of the hull, just a number of spaced frames at the stations or maybe more between.

[SaltyMonkey]

Originally Posted by dskira

No it is a cover plate on top of the tank.
Look very attentively the other design where it say: floor.
I know the arrow can be confusing since it show only the top of the floor. the arrow refer to the whole triangular plate going from the arrow to the keel.
As you can see the floor is not horizontal, it is a vertical plate from one side to the other side of the hull.
Daniel

I'm sorry, but I don't see how a horizontal floor welded on top of the vertical frames is going to add any structural improvement into the design. And it's only going to make getting to the bilge an issue. Cutting holes in the added floor to get at the bilge will decrease any benefits you are suggesting. The solid frames are deflecting forces adequately. It's a matter of having enough of them and spaced accordingly. If you are worried about the frames somehow folding - which I believe will not happen given the number, thickness, and nature of forces in the "arch" - then simply add a bit of horizontal plate on top of the frame making a "T" (tab) should be adequate...say 2-4 inches...which is basically a mini floor.

[David M]

If you guys want to debate the merits of this type of construction in a thoughtful and gentlemanly manner then that's fine, but please leave the personal attacks, insults, snide remarks and innuendos out of the discussion.

Most of you doing this have been around long enough to know better. Please don't force us to have to close this thread.

[Brent Swain]

The 3/16th tank top is the equivalent of a fully welded horizontal bulkhead , structurally. Some have asked me "Why not put in a removable stainless tank?" When you do that you make the area under the tank completely inaccessible and have no way of knowing what is going on under it until it becomes problem. With the built in tank, and a clear port in the inspection pate, you can see the hull( tank bottom) any time by simply lifting a floor board.
The top of the built in tank adds a huge amount of structural strength to the ends and baffle, making the equivalent of a huge floor, to support the keels, something which a removable tank doesn't do. The joint between the tank top and the hull is an extremely strong point , as strong as or stronger than the centreline, which lets you end the keel webs there, tied in for and aft with longitudinal gussets, along the tank top- hull seam.Without the tank top, the webs would have to reach all the way to the centre line, greatly extending their span, and making it hard to use the space as tankage, and if it is not used as tankage, then tankage has to go somewhere else, taking up valuable storage space. The area under the floor is not too useful for anything but tankage . Other spaces are far more usefull for storage.

[SaltyMonkey]

Thank you Brent for your eloquent, professional and clear answer, and being patient with those less involved building boats for a living.

I still do not see why any floor is necessary if framing is constructed w/ T-beam in mind - similar to a mesh construction.