Transverse frame calculation

Do I see framing added into that boat in some of the photos?

 

I opened that link, I read(a small error in pattern that resulted etc) what a flaming mess
Why is it that people build such very ugly things
i mean it actually cost the same to BUILD A BEAUTIFUL yacht as it does to do this sort of thing
I will answer my own quastion
They do it because the dwgs are el cheapo, what they do not take into consideration is, that, the boat will be worth a fraction of what a properly designed yacht will be worth upon resale
In other words, it is a poor investment indeed
i want to stand on a cliff, look at my creation down there in the bay, and be proud of her Her, how on earth could you be proud of this bent piece of recyled toyotas

 

I have come to this same conclusion however, I am not sure the "You Get What You Pay For" is universal in the yacht design industry. I have yet to determine what you really get.

 

I just modelled this further

I estimated the curvature and framing, here's one frame attached to 400mm of plating.

Both methods of construction are run together for comparison, they are the same material and the same dimensions.

The top frame is pre-bent then welded to the plate, the lower is welded flat and then pulled into shape.
The plate edges are partially restrained to stop them buckling as the adjacent plate would.

There's a cross section of the structure in one of the pics.

Note that the ends are restrained and in both cases the frames stay pretty much in shape towards the ends becasue of this restraint. That's probably being a bit generous since it would need to be very well bracketed.

The pre-fabricated framed structure has deflected a little but still has a large reserve of strength.

The pre welded structure sprung into place simply collapses under the same load.

The analysis is non-linear (for the FEA buffs) and it is definately required for this type of analysis. Non linear FEA is the great leveller of qustionable structural arguments.

I'm not sure what else should be said except that the cautions about scaling and weaker framing methods hold.

I'll look at this again later time allowing and try and put a number on just how much weaker this is.

 

Thankyou mike for doing the modelling and showing the performance of that kind of structure under load. What was the load required to get to that point?

 

Yes probably needed more support because of the bilge keels

 

LyndonJ I didn’t say the deck was a transverse frame in fact I said it wasn’t.
I am not sure what you mean by the large brackets on the topside plate.
I couldn’t comment on what a class society would or wouldn’t classify but then very few amateur built boats probably would bother.
Your statement” Just because it has been built doesn't mean its safe or durable or best use of material “I quite agree with but up to this point a 60-foot boat was unlikely to be achieved.
I am not advocating this method of boat construction over any other but it seems these boats have to perform to a greater standard than most other recreational craft in order to justify their construction.

 

These deck/topside brackets are called "poor practise" in EN ISO 12215-6 standard (because they dont end to stiffener on topside).

http://www.submarineboat.com/images/sailboat/Pauls_Boat/IMG_5466.JPG

Is this structure completed?

 

http://www.submarineboat.com/images/sailboat/Pauls_Boat/IMG_5466.JPG

I was wondering when Paul's boat would be brought into the discussion. In fact, this was the rabbit that I expected Brent to pull out of his hat, but I suppose it is not finished & sailing, yet? Everytime I read an update on this boat, the loa has changed, again. The owner/builder has had a major learning curve to overcome in regard to this build, yet, is not shy to the challenge.

The reader will note that this boat was designed with two partial chines per side, in comparison to the single chine that Brent utilizes in his designs.

Perhaps, Jack Carson, the designer of Paul's boat, has done the math & either he or Paul would be willing to offer some of these numbers up? Regardless, this boat would certainly not be a good figurehead for the speed of construction of frameless boats(7 years+), nor do I believe that it will, in the end, be a boat without some form of transverse framing. tank sides, bulkheads, supports, etc., will serve the purpose of stiffening up hull sections, though how much math will be involved is the ken of the owner & his designer. If I recall correctly, the hull plating is all 3/16"(4.75mm). Would Paul have been further ahead, today, if he had chosen to build a similar-size "traditional" design? I believe so. The supporting steelwork & superstructures/components added to the hulls & decks would have required less guess-work. One of the benefits would have been much less templating & scribe work required when fitting the interior.

I spent a few days welding parts of this boat. Though my opinion should not be viewed as a critique of this particular hull, it was at that time that I decided that this method of construction was not for me, due to what I felt was a lot of guesswork. For Paul, I'd think that the creation of such a unique vessel is truly a labour of love!(it's gotta be love, if you met his girlfriend you'd wonder why he wastes time with boatbuilding!) I would hope that he'd consider talking to one of the mainstream designers, better yet NAs, well-versed in steel marine vessels, before fitting out the interior, if only to have an educated, written opinion for the future buyer. Regardless, assuming Paul finishes this build, he can be guaranteed to own a boat that will be the subject of much discussion and anecdotal evidence on this construction method for +-60 foot boats, for years, if not decades to come.
Mike

 

At least the top sides brackets are on the deck beams, Unless my eyes are decieving me I dont see a long along the bottom sides of brackets, hopefully he will add them!
Tom

 

I should add I scaled the displacment up by 20 times and it's a comparison of methods. I wasn't particulalry interested in the final load I just told the program to keep incrementing the load untill the strain starts increasing faster than stress.

To make a guess the pre-compressed frames aree around 1/4 the stifness of the pre bent/pre cut to shape frames. The killer is the stress reversal when the frame goes into tension it transfers all the compressive stress away before it starts resisting the load, that transferred stress ends up on the other side of the stress reversal.

I think there are a few other areas of high stress low structural contribution with this method. I need to look at the end reactions. There are going to be some very high stressed welds in places and you'd want some nice curved stress paths in the bracketing.

That boat 'Pauls boat' you posted the link to is a good example of poor practice based on best intent but ignorance of loads and stress paths and structures.

They need to carry those transverses up to the deck brackets and stiffen the topsides. I'd look at adding more floors too such as they have behind the engine in one of those photo's. A simple grillage analsysis of the topsides alone would easily convince anybody that this needs more stiffeners/strengtheners.

How can anyone produce such an in-built fatigue mechanism such as those deck-topside brackets? They are bull nosed when they should taper gently out ( but they really should carry on down to the bottom transverse frames end on a frame ).

I could go on. Presumably the 'designer' is self taught ? Or did he leave the builder to put whatever frames they needed in and just designed the shell ?

 

Yes to be fair it isn't finished yet and there may be transverses welded to the side of the brackets in the final form ( sure hope so).

 

Is that a 4 SALE sign written on the front of the boat in this picture?

http://www.submarineboat.com/images/sailboat/Pauls_Boat/mar30port2.jpg

 

welder/fitter thanks for the first hand observations and thoughts on that boat. It seems the empirical evidence is proving the case for the scepticism for the sixty footer. It may turn out to be a “less frame” boat rather than a “frameless”.
MikeJ the reason I asked about what load was being put on the longitudinal frames was to get an idea of what load caused them to fail and what other added structure could be added to increase their performance to an acceptable level. As you point out adding a pre bent /cut frame would be a start.
LyndonJ sorry I hadn’t seen that pic of the brackets. I think enough has been written about them.

 

Cheap I feel for them if it's a dream gone bad.
I can't help feeling that for the same effort and with plans from a decent designer they could have had an asset instead of a liability.