Transverse frame calculation

Yeah.......


we know..............

nothing new.

Boats do´nt flex in seaways?.... do´nt have to span throughs.............do´nt have to "hang over waves"...?


Go sailing, and come back after 40 years.

ähhhh
leave it, not worth.

 

Stuart
Keeping it away from ships (which is a pity). And only the hull not the machinery beds:

Bad welding, poor construction, poor design I’ve seen a lot of cracks from weld failure some from fatigue and some from poor welding practices/materials.

The best crack I saw was in a 35 footer here. They apparently heard a loud sharp bang. People on the boat said it sounded like it was hit by a large calibre bullet !

What actually happened was the keel to hull join was cracked for around 1.2 m on one side. It was still ok because of redundancy in the floors. That was the most extensive catastrophic weld failure I’ve seen on a small boat.

On another keel a vertical weld was split visibly for 150mm and on cleaning off the paint the hairline crack extended all the way to the keel base and upwards stopping just past the only longitudinal frame in the keel around 300mm total.
That weld was interesting as there was moisture in between the cement and the plate. It was away from the weld area where the concrete had been chipped, but they apparently had steam venting out of the prepared groove as they welded it ! A few days later just before re-launch it was cracked right up the middle of the nice new weld.

I've seen a lot of frame to plate welds cracked in various places and was looking at a 45' boat just last week that the deck has separated from the framing and successively broken all the chain welds either side of the mast step 2/3 of the way to the sheer. The deck is soft either side of the mast, that boat had been around the world twice and had experienced severe conditions on the way home last trip. They noticed it after this. Continuous welds would have been better in that region.

I've seen a number of smaller splits in welds, and fatigue cracks around bracket ends.

The framing adds the redundancy which is why these sorts of failures just get quietly repaired .

Redundancy is everything, and in the spirit of Brent here's an anecdotal tale:

I know a couple who were severely grounded in the Beagle channel with the keel trapped between rocks until rescued by the tide, it was a wood-epoxy herreschoff 38' they sailed on to England before they hauled the boat (daft) to find only two keel ballast bolts remaining and all the others broken !

Anyway I'm very interested in the load limits in the construction method Brent has been promoting.

 

The problem with statements like this, “these are boats are not ships”, is based upon the notation that the material in question, steel, is the best thing since sliced bread. Steel is tough as old boots, steel you’ll never bend a bit of 4x2 steel etc etc…all the usual anecdotes. I concur, ships boats, they all need addressing for the same, not different reasons.

Exactly.
A poor quality joint, is a poor quality joint, whether on a 10m yacht or a 100,000 tonne tanker. Poor quality does not respect size, only the details. As sadly noted in this MIAB report.


"….The fabricator changed the original design, and incorporated a fillet weld in a critical area. He did so to ease manufacture and reduce costs, but without the supporting calculations to assess the stresses to which the keel would be subjected. He did not consult with the designer on the changes. In 2005, 160kg of lead was added to the keel bulb for racing optimisation reasons. Once again there were no supporting calculations, nor were there detailed checks made against the “original” or “as built” designs to ensure that the modification was safe."

Fully concur. Regarless of size...

 

Hey

It's been done over and over again refining the class rules until they are at a bare minimum for safety.

Numerical methods...(Perchance I just passed another exam in that this morning ) are very close to the real world and FEA gives a very good indication of where the limits are. Providing the driver knows what they'r doing.

A longitudinal may even cause an earlier collapse by concentrating stresses in the panel in the axis of final collapse, but lacking the strength to resist the result.
A lot of structural design isn't as intuitive as some people may think.

6mm is a bit thick for a boat hull topsides. A 60 foot boat would often be plated in 5mm and 6mm for the lower hull.

Swain hulls look very weak in the fore part and that's what i'd be concentrating on.

Brent
I think it's a great idea to get the lines from you.
One things for sure, if any of those framing methods of yours ever went through survey they would demand transverse framing up in the foreward part for a start. Those longs you are specifiying are so slender they will only have very little effect. Even then only in low force impacts, the sort that would cause localised dents not the global collapse the class rules consider.

 

I did, and this is all I saw:

"happy to discuss with you but not in forum, when I first started building in 1972"

Since the subject is of interest to most of us here, I think we should discuss it openly.

 

Redundancy in a strongly built transversely framed hull. The transverse framing limits the damage illustrated magnificently.

If this happened on a similar sized hull to the BS origami structural model (of no transverse frames and only slender stiffeners in the forward end of the hull) I think we'd see the collision damage coming out on the far side too. It would be very doubtful that the boat would even survive.

I reckon I can prove it if Brent gives us the details we are asking for.

 

How much difference would a frame make had the impact been between frames? Not much.
How much difference did the chine and deck edge make? Light years more than any framing.
I make a living selling plans. I don't give them away for free.I sure as hell don't post them on the internet, or all you guys will start building my boats without paying royalties.
The bows, with their conic shapes, are phenomenally strong.

 

Ah, good, now we are able to demonstrate very simple structural calculations against anecdotes.

Below, is a simply layout of a transverse frame system. It shows the plate, the longitudinals and the frames. This is for a simply supported laod. (there is some fixity, but for this example, it doesn't matter)



When an impact occurs, the plate wants to move inboard, but what is resisting this movement, the longitudinals. But, what is supporting those longitudinals from moving, the frames. So, the frames, support the longitudinals.

During an impact, like that shown in the nice photo above by Lyndon, we can take the impact as a “point load”. That is to say, the applied load is over a small area, rather than spanning frames. We can analyse this by using the simple formula, see below. This can be obtained from any good engineering/structural reference book.



So, if we assume a worse case, that the load is applied mid-span (or half way between frames) the "a" = L/2. Therefore the formula for the bending moment becomes WL/4. ( L = frame spacing)

Now, to calculate the stress, we need another formula, this is given below:




The term (y/I) is what we call the modulus, this can be reduced to the minimum modulus, called Z. The "y” being the distance from the neutral axis, and “I” being the second moment of area, of the structural member. So Z = I/y.

So, the bending stress is simply = bending moment/ modulus, or = WL/4Z

So, if the frame spacing is say 1.0m, and the applied load is 1.0N, the bending stress is 1.0x1.0/4xZ = 1/4Z. Or another way of looking at is this, to keep the stress levels the same, what modulus, or stiffness of the longitudinal, is required, as the spacing increases?

So, the formulae becomes Z = M/bending stress = WL/4x (design stress)

So, if we take the design stress to be 250MP, the formula then becomes:

Z = WL/1000. Since (4 x 250 = 1000)

So, when the frame spacing is 1.0m and the applied load is 1.0N, what modulus, or stiffness, do I need?

Z = 1.0x1.0/1000

If the frame spacing is increased to 2.0m, Z = 1.0x2.0/1000 or (2.0 x 1/1000)

If the frame spacing is increased to 4.0m, Z = 1.0x4.0/1000 or (4.0 x 1/1000)

So, what we can see is that increasing the span requires the stiffness of the longitudinal to be increased. In this simple example, if the frame spacing is increased from 1.0m to 4.0m, the stiffness required is increased by 4 times!

But you think this is:

I wouldn't say a 400% INCREASE in requirement over 4.0m span is NOT MUCH. What span are yours, some 10.0m!!!

So, the further apart the frame spacing, the higher the stiffness requirement of the longitudinal to keep the stress BELOW the design allowable.

If you have no frames then any longitudinal needs to be increased by a significant amount, to keep the stress levels low and safe and below the safe working stress limit. If you do not have any frames, then the longitudinals have very little affect in resisting an impact load, like that shown above.

The chines and deck do not support any longitudinal. ONLY a frame can do that.

 

Ad Hoc has shown you the light (hopefully ).
It makes a huge difference, they stop the side collapsing they limit the buckling and they transfer the laod safely in to the entire structure.They allow the plate to stretch and absorb impact energy rather than just collapsing. Jump on a metal trash can on it's side and it see how it goes absorbing your energy........it can't it just collapses (buckles). Put some very slender longitudinal frames in it.....make any difference? Nope not really. Put some ring frames in as well and suddenly its about 10 times stronger. You make a few small dents. ( Trash cans are conical too! )

By now it's clear you knew nothing about buckling at all. And never even considered it looking back at the rubbish you have written.

Impact and buclking resistance of your designs will be way lower than a conventional boat (and that for the 36 foot version). The larger versions based on the no-transverse framig method will be shockingly weak and structurally deficiant even dangerous at sea. Then you really are promoting gross misinformation based on wilful ignorance just to sell your plans.

Your Pre-stessed arch argument collapsed very quickly and you now know that they are in fact weaker. So now all you have left is this conics rhetoric. 'Conic shapes' inferring 'phenominal strength.'
How exactly did you infer phenominal strength from conic development? It's not an argument you can support either. I'm happy to show you that it's not applicable as you use it.

It's just more nonsensical structural ignorance.
How did it ever get this far beats me.
Why didn't anyone consider that a high profile engineer like McNoughton gave you curry over your structural ignorance publically and safely. Why didn't you sue the pant of him all those years ago?

The radius you have to use infers very little strength to a thin shell and conic development is a very common feature on metal boats, but you can't claim it replaces framing. Understand conic development is not a cone it's a method of using flat plates not a phenominal strength feature.

Hey you dont need to post your lines here , just send them to one of the people able to tell you how your design compares. Any professionals will respect your intellectual property they won't build your boat just analyse it and tell you just how much weaker it actually is.

This is a free offer to try your design, by now everyone understands the result will be a fair and accurate enough comparison

I think you know what the result will be !

So either stop all the endless rhetoric and nonsense, or put your design where your mouth is for a change. And we'll do a proper tortue test for once rather than the tall tale versions.

 

This seems like a very reasonable & sensible suggestion. If such a "professional" suggested changes that would improve a design, why wouldn't the designer give consideration to incorporating the changes, with the ultimate benefit of improving the final product?

I noticed, some time ago, that Bruce Roberts has now offered a skeg design that is supposed to be an improvement on many of the boat designs he sells. Putting aside one's opinion on the quality of designs sold by BR, one can consider that this modification was done for a specific reason, or reasons, with the desire to improve the final product.

I recall that, on occasion, my father, a metallurgical engineer, would be contacted by other engineers to get his opinion on a project or specific issue. At no time would my father suggest to me that this showed him to be a better engineer than the person seeking his opinion, rather, he would point out to me that no engineer that he had met had cornered the market on knowledge of steel construction & that it could as easily be him seeking the opinion of another.

This website's greatest value, imho, is the vast resource of knowledge from all levels of boat design, construction and repair. If a member with adequate knowledge were offering to assist another in making improvements to their design or boat, why wouldn't one embrace such an opportunity? Isn't "building a better mousetrap" the reason behind each member's reason for belonging to these forums?

Mike

 

Anyone interested in the shape of my hulls can make a model from the pattern in post 190, from sheet metal , or bleach bottle , cardboard etc taped together. That should only a take a minute or so, then you will know what shape you are talking about ,for the first time ever. The picture above shows a flat topside, which has little resemblace to any part of my hulls.
On a flat topside and bottom , yes the frames are definitely the only thing which supports the longitudinals. On a curved surface, anything which maintains the curved shape supports the longitudinals , including chines and decks. Enough logitudinal curve constitutes the same stiffness as a frame betweent chine and deck. What part of "Curve" do you not understand?
You say curves don't add to strength. So go ahead and weld up a 16 guage square propane bottle, fill it and then tell us there is no structrual difference between that and a rounder one. Some have concave bottoms, for the same structural advantage as my conic bows. Curves don't add strength? "Busted" Curved topsides dont have any structural advantage over flat?" Busted"
Look up "curve" in the dictionary or wikepedia. Then ,possibly ,a slight ray of understanding may just begin to penetrate the super thick ivory.
Tell those who put the pre stress in the structural steel in concrete, that they have it all wrong and they are actually weakening it.
So much for that arguement. "Busted."
Bruce Roberts only began to redesign his skegs, after I pointed out on several sites the statement in his latest book that he designs his skegs to fall off when they hit anything. Others began to tell us of incidents of skegs on relatively new boats falling off, sometimes with the loss of the boat, on metalboatsociety.org. Roberts is someone who follows your rules, to the omission of common sense, and logic, and is highly respected as a designer for that reason.
My keel sides are made from a single sheet. The only seams are the leading edge and the trailing edge. In the 3 dozen steel boats I've put together with my own hands, many welded by their owners, who had little welding experience before bulding, and many more, built by others, also welded by inexperienced welders, many of which ended up doing tens of thousands of offshore miles, sometimes in extreme conditions, a weld has never failed. That shows how likely the odd of of a weld failure is and how little extreme tension the welds are under, chicken littles. No the sky is not falling, noir is it likely to..
The attachement to the hull is a major factor in strength. High aspect ratio keels are always having problems with this. The amount of rocker and width ( curve ) in the attachement point also add considerably to the strength of the attachement. On my 36 the keel at the attachement point is 18 inches wide by 12 feet long with nearly a foot of rocker. There is no comparison between the strength of that ,and a high aspect ratio keel with little rocker or width to it. Mine will never fail . 16 days of pounding in up to 12 foot seas with the keel buried in sand almost too hard to make a foot print in didn't do it. But you say, if the numbers say your high aspect short cord keel is stronger, then that is the best way to go? You say that keels which have a habit of falling off without hitting anything, are stronger, if the numbers say so?"TOTAL BULSHIT".
So when is one of you going to accept my challenge of a demolition derby with an approved glass or wood boat against my unapproved steel origami boat? One couldn't ask for more definite proof that you have little faith in your own ********.

 

Brent

It would be nice if you could stop the diatribe and concentrate on the reality of what we are trying to show here.

We aren't discussing Roberts ( who changed his designs by the way and recommended retrofits as you have been informed before ). His design team is now fully ISO compliant and based in Europe.
The changes to skeg design came from a USCG report not from you and there was no death just a loss of vessel.
So get your fact right. Even then it was attributed to poor welding and a design with little allowance for poor welding in a high fatigue area. Now that's something you could learn from too. Promoting larger versions of your 36 foot based on the same structural reasonig.


Now the Demolition Derby
Can't you see that What is being offered is exactly that. Just no-one needs to get killed or property damaged. Your defence to patently obvious poor structural design is to suggest a demonstration that no one would accept.

We have a better way. We can destroy your hull in a myriad of creative ways which emulate more important real life scenarios.

You have just about every structural argument either completely wrong or so distorted its not applicable. Consider your target audience. You are not trying to sell designs to impressionable first time amatuer boatbuilders here.

So email me your lines or preferably a 3D shell and you will have your demolition derby in detail.

 

Smash up boats to prove what exactly? Will it prove that the front half is at risk of a structural collaps in heavy weather.............

We don't need anymore than simple observation. The lines would have showed this but the photo will do anyway.

The hull from the mast to the bow is lightly stiffenned by a few very slender 1 inch by 1 inch by 1/4 L frames .

This build has at least has a full transverse at the mast. But the remaining panel is unsupported, it should have several full ring frames to support the longitudinals before they can do anything.

As for the phenominally strong conic section , it's not even there. Where did it go?

Curvature in thin shells is a catch, the radius to thickness is too large to get any support and it can buckle very easily. This is because theres more material around and it can collapse happily without having to stretch anything, (you can demonstrate this easily with some metal foil).

The hard Chine stops at the mast frame, the curved chine that carries on could count for a foot as a chine but after that its another shallow curve. Yet its treated apparently as a full structural member all the way to the forefoot. Absolutely astonishing, any class surveyor would collapse in a laughing heap at that.
There's no way these designs would pass any scrutiny, To imply that they have passed any structural survey as Brent designs them ( not necessarily as built ) is really dishonest.

It's all total myth. This "supposed" design is weak beyond belief while Brent Swain claims they are stronger, because of longitudinals always under compression , phenominally strong conic sections , the deck as a transverse bulkhead

Brent you think you can scale this mess up to 60 feet? Yeah we already saw the poor bloke who is trying that, what a mess that is. And you were a consultant !

How many other rank amatuers have bought these structural arguments and are going to get caught with horribly weak boats?

Thats what we have to kill here, the structural arguments used by Brent are patent nonsense. You cannot design a robust hull to them.

 

Oh dear, here we go again. Just more words, not facts.

Perhaps everyone should ignore the material and just make the hulls out of bleach bottles.??

It is not the shape but how to acquire the shape that is in question. The hull shape in my post of 190 (which you refuse to provide to anyone yourself), or rather the method to acquire the shape you require, clearly demonstrates poor quality detailing and promotes poor quality fabrication and does not in any way constitute “good shipbuilding practice”. This has been demonstrated endlessly by many authorities around the world, including TWI (ref’s given), and is the principal reason why Class does not accept this method of jointing/fabrication.

So, your retort is simply, ignore the poor quality, ignore these poor quality joints, ignore the fact that Class will not accept these joints, and ignore the fact that your philosophy of build (not structural ‘design’) promotes poor fabrication practice, which in turn leads to a poor quality structure with zero redundancy. Ok, now we understand your position.

Quality means nothing to you, only your method of build is acceptable. Regardless of the consequences.

We have noted that you need to use a dictionary far more frequently than anyone else to ascertain the meaning of words and their definitions. Since you cannot even use the correct terminology when referring to boats, let alone English comprehension.

By calling a transverse weld a “seam”, that is the most basic definition any fabricator knows. It is called a “butt”, not a seam. But then that points to being trained properly and correct procedures and quality and good shipyard practice. But as we can see, you’re not an advocate of quality or professional training.

I think you had better retract that statement and go and apologise to the family members of the person that lost his life onboard the 10m yacht noted in the MAIB report I gave above. (But since you have no respect for quality of fabrication, why would you have respect of quality of life?)

The reasons, which you like to ignore, are given in the conclusions/summary are plain for all to read (see post above for MAIB report):


...Yacht designers should ensure component designs satisfy the appropriate standard safety factor requirements. In this case, the keel steel’s full ultimate tensile strength was used in the calculations instead of yield strength, and thus an artificially high safety factor was achieved. Changes to critical parts such as hollow, highly stressed keels, should be properly worked through and supported with calculations to ensure their suitability. Owners should seek expert professional advice, and wherever possible, reference should be made to design drawings, and the designer/builder consulted to check construction details and suitability of the modification. Do not dismiss the importance of keel coating detachment, or evidence of cracking of the coatings at the keel to hull interface; this may indicate more deep seated keel structural problems. Seek expert advice – you may need to use non-destructive procedures to check that the keel structure is sound....


All you do is show contempt and wish to ignore this advice, just like you wish to ignore the effects of poor quality joints. That is very unprofessional.

As I have noted in my post 129, but since you find it difficult to understand, I’ll post it again:-

Ok, here is a nice GRP boat to compare yours with:



However, since you keep claiming size makes no effect, this should be an easy challenge.

 

Paul a has pretty well ignored advice I gave him to beef up the keel webs, so I don't consider myself responsible for his decisions.
None of the cheap interior filler I have used anyhwere in my entire interior has shown any cracks, in nine trips to Haida Gwai, one to mexico and back and two to Tonga and back to BC, and 26 years cruising full time, so that shows how much the hull is not flexing. So when is it going to flex? When the sky falls?
The span ( from deck to chine) is less than a meter.
Transport Canada surveyors had no problem passing an aluminium 53 footer for Charter work. A vancouver surveyor had no problem passing a 36 which he surveyed thruout the building proccess., The US coast Guard, when they checked out Quarante Dos , one of my 31 footers , wrote in their report "This is one of the best built boats we have ever stopped. "
If the bow can buckle very easily, then why didn't it buckel in the 16 days it spent pounding on the west coast of Baja in up to 12 foot surf? Why didn't it buckle in the 300 meters it spent pounding across a Fijian coral reef. Why didn't it buckle in the circumnavigations and single season passage thru the NW passage? Why didn't it buckle in the two trips to Tonga and back, 8,000 miles to windward against strong NE trade winds. Why has it never buckled in 30 years and hundreds of boats sailing anywhere they pleased? When is it going to buckle? When the sky falls? I wont lose any sleep over that likelihood.
In order to buckle at any point, all surounding metal has to compress on edge, at 60,000 psi.
There is no shortage of fibreglas hulls with far less curve in their topsides and no fames nor longitudinals . It's only the totally flat ones that flex, despite FG having a fraction the strength of steel.
Demolition derby would do no major harm to my boat , but would destroy your "approved" fibreglas boat which would prove my point, and totally disprove yours.
God forbid, we could never do anything which would allow that too happen!