tane
Super Anarchist
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- 352
...& do you know what "transom hung" is?
Loss of S/V Raindancer (KP44)
- Thread starter Boats13
- Start date
mckenzie.keith
Aspiring Anarchist
No problem. We will get a grant.Yeah you have to test if against a simulated whale. How much would a ballastic gel whale cost?
It's just gelatin powder and water. You might need a lot.
Clear Ballistics
www.clearballistics.com
View attachment 581053
Good thinking "Whale Injury Mitigation - Effects of Varied Hull Forms". Then whack it with bigger and bigger boats. That's got to be worth some serious cash. Should the whale be a big rectangle? Does it really need to be whale shaped?
We'd need a big mold. Perhaps a cylindrical whale? Borrow a fuel tanker truck that is due to be scrapped. This idea has promise.
We'd need a big mold. Perhaps a cylindrical whale? Borrow a fuel tanker truck that is due to be scrapped. This idea has promise.
Diarmuid
Super Anarchist
TheDragon
Super Anarchist
One of the many things I like about my boat is that it will sail itself upwind and even on a close reach. But I was a complete failure at getting it to sail itself on a reach, let alone a broad reach.
Crossing the Pacific from Panama to FP last year my Windpilot windvane broke north of the Galapagos (the 1/4 inch diameter stainless steel rod that connects the vane to the rudder broke) and later that day the tiller autopilot stopped working (long story). So for a week I let her sail herself with the tiller unconstrained, day and night, while I tried to fix the Windpilot. You can see from my track that we curved slowly SW. It would have been almost impossible to get to FP like that. I tried to get sheet-to-tiller steering to work, but failed. My first repair only worked somewhat but allowed sailing on a reach in the SE trades for another week down to 10S. My final repair worked as well as new and allowed 2.5 weeks on a broad reach straight to Nuku Hiva.
estarzinger
Super Anarchist
- 7,793
- 1,230
Disclaimer - I am no expert on materials and structures.
My opinion(s) are (a) it is more of a design and construction quality question - made 'properly' either composite or metal can be as near indestructible as you want. Made 'poorly' they can both come apart easily. And (b) that it is generally easier to make a metal structure nearly indestructible while it takes more money, skill & care to make an equal composite structure.
Hawk almost certainly would have fared better, as would any expedition-type vessel (or 'near-expedition' which is really where Hawk was). They are generally designed and built to account for and survive somewhat routine groundings and ice impacts.
I do not know enough about the Boreal/Garcia/Bestevaer specs to say for sure. I have a couple of friends with Bestevaer' and they both increased the structural specs above 'stock', which the yard is happy to do, but it suggested to me that the 'stock' structure is more 'performance' and less 'expedition' oriented. But that is all 2nd hand and as I said I don't know enough about them to really have a valid opinion.
Beating a panel resting on the ground shows more the toughness of the material. If your whale has the bad fortune to choose a spot on your hull backed up by a full bulkhead, one might expect a better outcome (though perhaps still a tough day). If it fortuitously picks a panel between bulkheads, now the fun begins. To keep from being holed, that panel has to absorb the energy of the collision, either stopping the whale, or accelerating the boat to whale speed, or a combination. Both are energy problems. Usually hull plating is sized for deflection, not so much strength. Fiberglass is likely to be around 2x aluminum thickness, to achieve near the same stiffness.
Energy is absorbed by elastic deformation (springs back) and inelastic (stays deformed). The problem with fiberglass is the elastic deformation part is very limited and inelastic pretty much zero, it stretches only about 1 - 2% before failure. 5052 aluminum will stretch 12% before failure. Energy absorbed is the resistance provided by the material times the distance stretched. The fiberglass plate is roughly twice as strong in tensile as the aluminum, being twice as thick and about the same psi yield. But the aluminum will stretch 6 times as far before rupture, so it will absorb 3x the energy when it does fail (1/2 tensile x 6x distance). Enough for a whale? I guess, it depends on the whale.
Those considerations are also why a glass laminate is preferable to carbon for energy absorption (stretches much further) and why S glass is better than E glass.
A better test for Steve is to take a panel of each, clamp it firmly to span two frames, then drop a bowling ball on it from increasing heights until the fiberglass breaks. I'd expect the aluminum to fare much better.
Energy is absorbed by elastic deformation (springs back) and inelastic (stays deformed). The problem with fiberglass is the elastic deformation part is very limited and inelastic pretty much zero, it stretches only about 1 - 2% before failure. 5052 aluminum will stretch 12% before failure. Energy absorbed is the resistance provided by the material times the distance stretched. The fiberglass plate is roughly twice as strong in tensile as the aluminum, being twice as thick and about the same psi yield. But the aluminum will stretch 6 times as far before rupture, so it will absorb 3x the energy when it does fail (1/2 tensile x 6x distance). Enough for a whale? I guess, it depends on the whale.
Those considerations are also why a glass laminate is preferable to carbon for energy absorption (stretches much further) and why S glass is better than E glass.
A better test for Steve is to take a panel of each, clamp it firmly to span two frames, then drop a bowling ball on it from increasing heights until the fiberglass breaks. I'd expect the aluminum to fare much better.
fufkin
Super Anarchist
My understanding is that Kevlar re enforced carbon, from the inside layer of the carbon layup (as a membrane in tension) as opposed to on the outside (as a shield), can help with the ultimate breach/brittleness factor of carbon. (I’m no materials expert)...probably still not nearly as malleable/pliable(probably the wrong terminology) as aluminum but better than pure carbon.
And yeah, re enforced areas like in front of the keel are one thing, but if you were going to re enforce for a whale, you don’t really know where or at what angle it’s gonna hit. Unlike debris where you can predict the likely collision area, with a whale, you’d have to re enforce the whole hull.
I suppose one more realistic measure that has been taken to get beyond the average safety factor would be strategically placed double walled fuel/water tanks built into the hull.
And yeah, re enforced areas like in front of the keel are one thing, but if you were going to re enforce for a whale, you don’t really know where or at what angle it’s gonna hit. Unlike debris where you can predict the likely collision area, with a whale, you’d have to re enforce the whole hull.
I suppose one more realistic measure that has been taken to get beyond the average safety factor would be strategically placed double walled fuel/water tanks built into the hull.
Fah Kiew Tu
Curmudgeon, First Rank
FWIW a small steel boat's plating is sized on weldability and rust allowance a lot more than deflection and strength. That's why they're so massively strong.
3mm plate, even 2.5mm would be more than adequate structurally but it'd be damn near impossible to weld fair. The difference in weldability between 4mm and 3mm thickness is quite surprising. My hull is all 4mm and is quite fair without filler, the only bog is a small amount on the butt joint welds.
FKT
RedRackham
New member
I think this should be handled like NHTSA crash tests, but with ballistic gel whales coming in from all angles. That's the only way to be sure.
Panope
Super Anarchist
mckenzie.keith
Aspiring Anarchist
Maybe we can use a deceased beached whale as a plug for the mold? Also we could possibly calibrate and validate the first item synthetic whale against the deceased whale.
Panope
Super Anarchist
The problem, is finding sacrificial boats to test.
The impact device is easy:
Tie a couple of old mattresses (to simulate whale skin) to the grill of an old junk car (that still runs) and ram the shit out of soon to be demolished boats.
I think one would learn pretty quick what works and what does not.
The impact device is easy:
Tie a couple of old mattresses (to simulate whale skin) to the grill of an old junk car (that still runs) and ram the shit out of soon to be demolished boats.
I think one would learn pretty quick what works and what does not.
RedRackham
New member
I just assumed we'd be testing on Hunters and MacGregors?
Panope
Super Anarchist
Hunters and Hinkleys
Bestevaers and Brent Boats
Pogo's and Pacific Seacrafts
Woodies, Ferro, Cored, Cold molded
Backyard Hack Jobs, production, Bespoke
I want to ram them all.
Panope
Super Anarchist
I'd take that job.
Let's see, if we lash a log to the roof of the car we get a good simulation of a Dead Head impact.
Let's see, if we lash a log to the roof of the car we get a good simulation of a Dead Head impact.
WhoaTed
Antichrist
Dare say Walmart may have some folks who’d be interested in participating in a scientific study for your $10.
167149
Super Anarchist
defrost chicken first
