placement and spacing of frames

Yeah but I have a good textbook plus a working hull to PROVE that it works...it's called Noah's Ark. The hull of the Ark is STILL FUNCTIONAL to this very day. Can you build a boat hull that is 515 ft long out of wood and have it functional (well sort of anyway) 4000 year later?

I take that as a compliment you telling everyone that I am the ONLY source for engineering a boat of the Ark's calibre....makes my whole day.

But yes, i must give Noah his credit....I am simply copying his design/build tecniques which are unbeatable.

Would you like a full color hydrostatic performance analysis as proof?
Google Earth it.

 

How ignorant can you get? You're giving structural advice, yet obviously know nothing of structures.

I have no idea what you're on about with all this fraternity stuff, anyone with any knowledge at all about minimising deflection in a beam will know of George Biddell Airy and his contribution to our understanding of mechanics. His ratio for spacing supports to minimise deflection is to have supports arranged symmetrically around the centre of a beam with a distance between them of 0.577 x the length of the beam. Not exactly your golden ratio, is it?

 

For goodness sake Capatain Bill - if you actually went and looked at "Noahs Ark" you would see it is nothing of the sort. Noahs Ark gets 'discovered' every 50 years or so, and its always rubbish.

check out http://www.answersingenesis.org/creation/v14/i4/report.asp for some commentary on one site ( looks like the one you are quoting, but who can say)

Even if it WAS Noahs Ark, - it wasnt built to the "Golden Ratio". That term wasnt even invented till the 1900's, and Mr Fibbonaci was born a long time after Noahs Ark. And NO, Pyramids, Greek Architecture and the like werent built according to these concepts either.

I cant believe there are still some people in this age of boundless Web knowledge that can still be so deluded. I ask you again to peddle your unsubstantiated concepts in a more appropriate forum.

 

I'm not really sure it's still functional, but whatever the wood aging problem it might have it's nothing that PAR couldn't fix. The only glitch - to whom should he send the invoice?

 

If you really know what your doing you just have the invoice sent to the old lady....

Song of Solomon 8: 8 ¶We have a little sister, and she hath no breasts: what shall we do for our sister in the day when she shall be spoken for?
9 If she be a wall, we will build upon her a palace of silver: and if she be a door, we will inclose her with boards of cedar.
10 I am a wall, and my breasts like towers: then was I in his eyes as one that found favour.
11 Solomon had a vineyard at Baal–hamon; he let out the vineyard unto keepers; every one for the fruit thereof was to bring a thousand pieces of silver.

Put a little jingle in your pocket...

But you will never manage that without understanding the Golden section first.

 

PAR,

I know its probably a typo,

Dave was my instructor at Westlawn he is also Director, his last name is spelled Gerr.

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Like you talked about, there are other reasons for frame spacing, in looking at the overall vessel design including systems. For aluminum vessels 60 to 80 feet (semi-planning), I have been trying to push tighter frame spacing (more frames) of thinner material, but at comparable weight/strength through lighting holes and minimal/strategic use of frame web welds.

Why more frames?

Frame design is key to overall systems integration. Using 3D visualization you can see very easily how the proper design of frames for systems can significantly reduce assembly time and ease component routing, and produce a more efficient and compact design. If it were my project I would not commit to the final design without a complete 3D routing study. The word "route" in 3D vessel construction, is a CAD Designer way to say how are all the Electrical and P&ID (plus misc pertaining to a specific design type), is managed in overall design.

Frame design considerations (beyond hull/structure requirements):

Quick list:

Tankage + Fuel piping + Transfer and fill.
Engine Beds, Keel cooling, Reservoirs, Running gear
Firewall bulkheads
Water tight bulkheads
Electrical AC and DC (grounds, bonding, cableways, boxes, lights, ........)
Water; Fresh, Salt, Gray, Dark. (hoses, connections, tanks)
HVAC + Refrigeration (Water cooled condensers)
Floors/Ceilings/Panels/Stairs/joinery: Including all assembly methods.
Hydraulic piping.

Mark

 

And this is based upon what….looking at a 3D image? Please define ”Proper”….

You are forgetting the most obvious (or perhaps not forgetting, you’re just unaware of this) is that increasing the number of frames does several things.

1) Increase in fabrication time
2) Increase in distortion of hull plating
3) Makes fabrication more difficult when tightly packed
4) Does not guarantee thinner and lighter, there are minimum scantlings one does not go below, regardless of vessel size.

You need to design a hull structure with variation of frame spacing and stiffener spacing. Then once you have done this, do a weight check of each. You will be surprised.

Frame design is based upon the SOR of the vessel.

 

Ad Hoc,

To answer your questions:

Systems considerations are brought in after a preliminary first look at framing, after hull design faring and developable considerations. The basic hull SOR is satisfied.

3D real time visualization using solid models of the proposed first cut hull and equipment allows placement as per CG of elements, and trail routing of all components relative to one another. The models can be fully rotated in 3D space, and interferences detected, and perhaps more importantly the system layout can be reviewed with the responsible engineer to verify specification intent per each system. In the end we have an overall 3D assembly of all the major components, their routing, location, and proximity to one another.

Do you not use 3D assembly CAD modeling?

The discoveries for the structural and systems designers are significant at this stage. They can see where their "vision" was incorrect, we then look at alternatives and these include structures (framing).

So there is some design iteration where we can really polish the design before fabricating. Many times what is forgotten is crew access, equipment maintenance, and repair.

Assembly time for the frame is a consideration, but it may be offset by time savings elsewhere.

Let me be a little more clear. If for example the normal frame spacing requirement was 20 inches, but it was found that there were advantages to more frames at 18 inches, we would then take a closer look. The structural engineer in charge would have to okay the change before it went for final approval. But once he sees the overall advantages he will rerun his analysis and its usually not an issue. However, as normal, he will expect a level of frame performance per his new requirements.

For the frame assemblies it is trivial with the software to find out weight, moments of inertia, CG, and many other parameters. I can easily change the thickness to a common plate size, use a different alloy, move lightening holes and check preliminary FEA for stress risers. Takes a few minutes to rerun. No problems or surprises.

Mark

 

I’m sorry but this is just “sales” talk. It does not have any bearing on my job as a naval architect. It may impress a gradate or a newbbie though, since all that is, is detailing. Detailing is either good or bad, just depends upon the skill and experience of the detail designer, beit: mechanical, electrical, outfit etc. The 3D software just makes it “easier” for them to arrive at a conclusion, that is all. It is just another ‘tool’ for them to say ..yah..or nay. The design drives the details. Get the design wrong and it doesn’t matter a hoot how easy it is to detail in 3D, it is all wrong to start with. Thus you need to know how to ‘design’ correctly to begin with. 3D doesn’t do that…it is just a tool.

No….not necessary.
If you know how to visualise and know what is required…basic 2D CAD is plenty good enough. 3D cad has more outputs such as BOMs etc..but those issues have no bearing on my job or how to achieve the goal. It may help others, such as those doing the detailing or BOMs etc..but doesn’t do the “job” any better nor quicker than I can do myself.

Such as..?

 

What package do you use ?

I had a call from a SolidWorks salesperson the other day.

 

It is better to use more longitudinals than more transverse frames. With longitudinal system of stiffeners (common for alu high speed craft) spacing between frames does not effect thickness of plating once condition l/b>2 is satisfied (where l is length of unsupported panel, b - beam of unsupported panel).

 

It really is good to lose the nice visual-front software and know how to do it with a compass and a square. Not that many points, actually , if you build points for a couple bezier curves. and most of the points are repeated/shared too.

Can you 3d model one of the right here?



And now that you mention it, wouldn't a stringer system like a wallnut be the ultimate ideal anyway?

 

Alik,

I was not really addressing high speed planing craft with my frame discussion.

rwatson,

I am fluent (over 8 years experience) in the following:

AutoCAD2D, AutoCAD3D, Inventor, Mechanical Desktop (old).
Solidworks
Rhino, Orca3D (4Y), T-Splines (3Y)
Altium Designer
MathCAD
Microsoft; Office; Excel+....
Adobe; Acrobat, Photoshop, Illustrator, In-Design, Frame (old).

I can interface to Maxsurf and Shipconstructor. However, I am not responsible for final hull hydrostatics, hydrodynamics, or stability. I only do CAD solid modeling in this respect.

Sign off for these studies require NA+PE.

I am not an NA, nor have I ever claimed to be.

My background is BSEE,EET,Mechanical + HVACR,ABYC Master Technician.

What would you like to do? Perhaps I can help?

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As far as Marine CAD design at this point I can only discuss what is in the public domain. Palmer and Discovery have done the AutoCAD thing and have discovered the speed advantage with Solidworks for 3D solid modeling.

But I should qualify my remarks.

The real issue with CAD is compute power. What is needed is for Solidworks and AutoCAD/Shipconstructor is run on a desktop Cray Supercomputer, if such a thing existed.

So why is this important. Without the compute power the design work to remain productive is split into smaller workstation tasks assigned to individual designers, doing small components and assemblies.

When a larger assembly is moved to AutoCAD Shipconstructor in my opinion it can be too slow. So things are done in small chunks (Solidworks) and then brought into AutoCad Shipconstructor which is used for large assemblies.

The larger the assembly generally the longer it takes to render.

Mark

 

You know, I definitely am no pro at 3d for sure, more like someone trying to find the best all around approach for 3d and hullforming, before committing to some particular software package. I have looked into (downloaded/tinkered with) everything possible from the net and the Rhino + T-Spines + Grasshopper is probably the best combination of tools all in all. Haven't tried many of the high-end packages.

If you havent tried Grasshopper in Rhino yet you should really check it out. The TSplines guys have TSplines and Grasshopper working well together.

 

Well, it is fully applicable to displacement and semi-planing craft as well. Use longitudinal system with ring frames; starting from certain condition spacing of ring frames does not effect the thickness of plating.