Well this is important because you may dupe someone into building something dangerous.
I had drawn the tank and specified the angle iron webs in that design by that time in the plans I sold them, which they ignored. .
But thatís not the only boat it happened to is it ! It was an illustration of your approach to designing by mistakes. Iím just illustrating that your intuition was incorrect. You initially thought it would be strong enough because of the curvature, although any designer worth his salt could have foreseen the weakness and the consequent buckling of the supporting plate. Something you didnít grasp until it happened. I think itís a good example of where some sensible engineering would have helped you from the start.
So you modified the plans after it had happened to other boats.
Now you are pretending it only happened to one boat in extreme circumstances after you altered the plans and wrote this .
"Given the tendency for the trailing edges of the twin keels to be driven up into the boat when they collide with a rock, and the fact that they are far enough back to be under the pilothouse floor in the 36, putting a 3/16th plate web across them would reinforce them without being in the way of anything. The top of this web could be T'd with a piece of Ĺ inch by 4 inch flatbar, making it extremely strong."
The tops of the low aspect ratio keels on my 36 are 8 ft long. I have since seen them on that site , swooning over twin keelers which have about a foot of attachement to the hull, with a far higher aspect ratio.
How do you get a foot of attachement to a plastic hull ,with a far higher aspect ratio keel, to be stronger than 8 ft of attachement to a steel hull with a far lower aspect ratio keel?
You dont!( Mike the "Engineer?")
No Mike, with a track record like that ,I wouldn't want you "Engineering" any of my boats, any more that I would let a civil "engineer " do laser surgery on my eyes.
What exactly does this have to do with your earlier designs rotating their keels up into the boat ?
A friend posted several pictures of a couple of very successful origami 55 footers in aluminium on that site. One I last saw at Christmas Island after which he sailed back to BC in November. Jean Marc, the owner, has cruised enough miles in the Hecate straight area, year round to have done a circumnavigation, wiht zero structural problems .He loves sailing in full storms. Harvey , on the other origami 55 footer, cruises the west coast of Vancouver Island year round .
Completely demolishes your theory about them not being strong enough.
But you had nothing to do with these designs, and you canít say what framing was used, you are just borrowing them because they started life as origami, not frameless. They have exactly nothing to do with scaling your frameless designs.
Here are some quotes from a letter Steve on Silas Crosby sent me from the Straits of Magellan
"I thought you should know that Silas Crosby is amoung the smaller boats sailing around , but it seems to cause us less worry that most boats down here .
The ability to get in very shallow and even dry out , or just touch at low tide, is a quality that most people, even here , do not have a clue about.
While avoiding ice chunks near the Pia Glacier, I hit a rock dead on at 3 knots . A shrug and carried on. Thanks for your helping me get here . Good boat, good design."
This completely demolishes Mikes theory about my boats not being strong enough.
No you are being deceptive again I'm not saying your boats under 36í are not strong enough. I said a scaled up design sans frames wouldnít be strong enough.
I have shown that pre welding the longitudinals flat and then pulling them into a curve along with the plating is weaker than post welding after foldup and I showed you why. So your method is weaker than you could achieve with the same material, its why your designs will dent easily.
If you pre stress something its already under load, when you push in the middle of that member it deforms more easily and again I showed you and explained why. You had no comprehension about stress reversal nor about buckling. You still donít. The internal longs cannot stay in compression under load, if you push on the hull they can only work to resist the load by going into tension because they are not in enough of a curve to be self supporting like the arch. So by pre bending them along with the plate you make them weaker, they want to straighten which assists the load in deflecting the side of the hull rather than resisting it.
That the longitudinals are arches always in compression is the whole basis of your strength argument which is simply wrong.
This in important because itís easy to show that you cannot scale your boats to 60 feet as you claim. Simply because your structural arguments are completely flawed and based on intuition. I offered to model a hull and give the imploding depth in a bow dive, you didnít want to know.
Any frameless design scaled much over 36 feet will start to get quite weak without some transverse framing. Iím still happy to model it if it saves someones bacon.
So save your 3 knot collisions in sub 36í frameless origami boats, that's where it works, I don't have a problem with that. Even if you design weak boats for the material used they may well be strong enough becaue the material is so tough anyway.
Anyone who understands structures can explain to you why shell buckling renders thin shell monocoque unsafe if itís simply scaled . You can ask any naval arch mechanical or marine engineer. Youíll get the same information. Try it we are all approachable.
So who would you believe, someone who has sailed one of my boats from BC around Cape Horn, then home again via the western Aleutians , or some one who has never sailed on one , an armchair expert?........
Again what does this have to do with scaling your design or your misunderstanding of how structures work exactly ?