placement and spacing of frames

You still want it centered over the harmonic as your basis point. Deciding width/stance plus also the interaction with other stations should be considered to address these issues. There is also a natural harmonic called the harmonic 5th that would probably be a good second station centerline. All creates balance. Counteracts point loading situations by creating natural flow paths for energy to travel. He wanted to know 'where best to place stringers' and upon the harmonic balance points is the answer.

 

Can this answer be demonstrated? Is there some paper which treats this subject in a more rigorous way?

You are using the vibrating string as a parallel. I am a guitar player and I know how is the distance between frets calculated and how to play harmonics. However, there's a huge difference between a string and a ship, in terms of shape, mass distribution, stiffness distribution, added mass due to water etc. What makes you think that the Golden Section rule remains valid for longitudinally asymmetric and non-homogeneus bodies like ships or, more generally, like anything else than a string?

So, again, a proof for your claims is necessary.

Cheers

 

If no one else will say it - I will, at the risk of incurring Capt Bills displeasure. The "golden ratio" has nothing to do with the design of boat hulls unless you want some kind of visual balance in the design.

The only basis for framing to a Fibonacci sequence is if the boat is growing by itself like a flower or seashell, where it is the most efficient method of organic growth.

And as for confusing boat design with a guitar string - there is no logic in that plan at all.

Some good commentary on the principles at this site ( good explanation at https://notes.utk.edu/Bio/greenberg.nsf/0/3ad194fabe1afec785256e9400823537?OpenDocument ), and also the history of the terminology, and debunking on some myths about the concept.

"Counteracts point loading situations by creating natural flow paths for energy to travel." - ???? give me strength

 

Okay I will say it. Alan, Capt. Bill is a nut job. His numbers are meaningless and bordering on absurd, which is fairly typical of his posts.

I'm still not sure what you are asking in regard to deviations to Geer's scantling rules, but as Dave Geer and I, in a previous post on this thread have suggested, the spacing can be adjusted (slightly) to accommodate areas that need attention. This might be as simple as the aft cabin bulkhead I mentioned or to absorb additional slamming loads based on target speeds or other use derived, additional load expectations you anticipate. Without the hydrodynamic understanding of the concepts, you're at a great disadvantage understanding the potential loads, so adhering to the scantling rules would be the wise course of action. Again, Geer's scantling rules will produce a slightly heavier boat then necessary, but not overly so. This is intentional on his part and does produce a wholesome, if not stout structure. In his book he covers most of the basic load increase or decrease adjustments, based on a few different factors. In terms of your end of the boat frame spacing, start at the bow perpendicular and erect your relatively equal frame spacing, from there. If you need to move something for convenience or accommodation or equipment do so, but decreasing spacing by 50% in the ends isn't justifiable without some fairly dramatic load anticipation expectation.

In short, if the Geer rule suggests you need 11 equally space frames on 24" centers, but you find 12 on 20" centers works out better for you, then no big deal. The only cost is the weight of a single frame. If you want you can "split the difference" and half the ends of the boat frame bays and center the new longitudinal frame dispersal, though this generally isn't necessary. Again and lastly, Capt. Bill is a nut job. (where's Richard when you need him . . . )

 

Why is it that this forum attracts a few nutters? It's something I've often pondered over, as unlike fora covering the design and construction of other forms of transport (and I'm actively involved in electric vehicles and was involved in aircraft design and construction for years), Boat Design seems to have more than it's fair share of often authoritative-sounding individuals who have little or no practical knowledge or experience to support their esoteric claims and views.

The OPs question is a relatively straightforward engineering one, yet seems to have been buried under a lot of meaningless drivel about harmonics and the golden ratio. Maybe we should embed special energy crystals at key points in the structure, too..............

 

Look at what you pro's are suggesting...

1) "Nuts and guitars are useless analogies for a boat hull" (absurdly false statement)
2) "You must be accredited by US and posses knowledge obtained from US and have a good reputation with US before we will ALLOW you to have a good boat. "
3) "You need to learn from XYZ college text to arrive at the figures that you need"

And I would never suggest that "proper schooling" is without it's merits. I just don't think people accept as an answer that they need to acquire advanced degrees and become 'worthy' of such advanced knowledge such as where to place stringers...I'm betting the man just wants an answer to the question.

I gave him that. I gave ACTUAL numbers. You offered nothing except a rabbid attempt to take these numbers away from him.

Why don't you just give the man an answer to his question? Most people can't afford to hire a Naval architect for restoring a pleasure boat. That doesn't mean they should be disallowed access to basic understandings of math as it applies to a boat hull.

I have a theory on why you don't give him some numbers...because they will turn out to be the SAME NUMBERS I gave, or real close. Or they had better be. Otherwise they will be 'out of the ballpark' or less than optimal.

But hey, being pros and all, you should be able to disprove the numbers instead of attaching lables to me in an attempt to discredit the numbers.

 

i am new to this place ,i was looking for some answers on how to build a catamaran ,but i am none the wiser after reading this lot

 

Ok, if all this golden ratio crap is so relevant to simple structural calculations, explain to me why the Airy point doesn't follow your golden rule?

Hey, whilst you're at it, take a look at the spacing of any structural members in any stiffness limited structure and you'll soon see that your golden ratio stuff is just mystical crap.

Structures are pretty simple, all that's needed is knowledge of the applied loads and their distribution (often the hardest part to pin down) and some high school level maths and physics. What's morally wrong is trying to make out that some mystical ratio, surrounded by ******** about "harmonics" and "energy" is a safe and viable way of informing structural design decisions. In fact, giving such advice to the unwary who may then go on to use them without checking with other more reliable sources is tantamount to reckless endangerment.

Before you make some off-the-wall comment about NA's, I have no connection with boat design (other than as an amateur, where I just used first principles to determine frame spacing based on allowable inter-frame structure deflection limits I set myself), but have designed and built aircraft and do have a reasonably good understanding of structures.

 

Have you seen the logo and name of their fraternity (Airy Point)?...Yada Yada PHI

In other words, the answer to this question may be based on the first principles of their fraternity, KEEP ANYTHING "Hi-PHI" FOR US ONLY and attack those thinking they are gonna take OUR PHI....or at least make them pay us lots and lots of money for it.

(I assume Airy Point is some consortium/thinktank organization concerning hull form practices)

 

I'm sorry to hear that, because I think that at least these points should be pretty clear to you by now.

This is a monohull:


This is a catamaran (what you're interested into):


This is a trimaran:


A quadrimaran (skipper visible too):


And finally (I didn't know it existed actually), a pentamaran:


Life is beautiful because every new day will show you something you didn't know.
Cheers!

 

Very true. Question is which is a more reliable source, the math itself, or some fraternal organization?...So it is reckless to use these numbers without approval (translate $$$) of some group of men who stand around 'approving themselves' as the keepers of this knowledge.

Truth is that you should have learned your golden section tables about the same time you learned you multiplication tables...what, second grade? But no this has been WITHHELD on purpose so you cannot understand this more intuitive shortcut to get the same calculated results....so they can charge you for it, perpetually.

 

So in other words 'I already knew that, but i will pretend I don't, and let the one's in the know know that I know by responding to this thread with a vague cryptic statemen like "I'm none the wiser"....they will know what I mean '

He's playing stupid to the masses while subtily letting the other 'knowers of everything' present here.....None the wiser....doesn't mean he learned nothing new....he is very vraftily telling you HE ALREADY KNEW THAT....get it?

Why respond at all otherwise?

 

Build it like a guitar, like a firecracker box or like a house if you want...
But in any case don't forget to equip it with all the accessories this catamaran has on-board: http://www.boatdesign.net/forums/op...-todays-sailing-anarchy-38697.html#post471384



P.S.
Just kidding. If you have some specific questions related to cat design and building, all you have to do is to place the question on the forum.

 

Capt Bill - I wont argue with your phsycho analysis of people and organisations, and your opinion on lifes big mysteries.

But, since you are the only one in the world who engineers boats using arcane mathematical concepts, does that not give you a bit of a clue about your engineering philosophy ?

Will you stop with the phsychology please ? We are talking about framing boats ! If you have any sound engineering concepts to impart, please do, but otherwise can you send your posts to a forum more suited to your areas of interest.

 

Yeah but do you really want to end up out on the water to end up in a debate over who is the 'accessory' and who is the Captain of your boat....assuming you don't end up the 'accessory' in the equation.


HAHAHA