bigmarv

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18 Whiner

About bigmarv

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    at sea
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    sailing

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  1. Yes, I can see flooding working, although not quickly if on the hard like Mala. As much improved as they are, lithiums are still a greater fire risk than lead batteries and fire at sea is bad. On an otherwise unsinkable multi it's the worst. I'd gladly destroy/abandon batteries that otherwise risked burning uncontrollably. Not being able to start the engine is small beer by comparison.
  2. Maybe. But your comparisons are off. Weight and complexity compared to what? Extinguishing and flooding systems as above? And as for not starting engines afterwards, a fire will likely be the end of the burning bank either way. Lithiums are relatively light so low siting less important. And their highest loads probably are as near the bridge deck as anywhere (capstan, winches). If boats had the same maintenance budget and regime as commercial jets then that comparison might make sense, but they don't. Given the loss on Mala, and that another poster is planning an actual flooding mechanism, the idea of a disconnection and dump doesn't seem much more costly or complex. But whatever, if you like this sort of boat you're right on top of avoiding complexity and cost.
  3. On a cat lithium batteries could be in a box that can be jettisoned in a fire rather than low and flooded inside.
  4. bigmarv

    Gunboat 68

    Agreed, although most boats aren't faced with it ever because they don't claim to and can't go that fast. In this context, the 20 knots is invoked as an illustration of what it means by those who say boards would not break. Here, the better question is probably at what speed the boards, drives and rudders will break. If that's below a scary speed, then impact injuries are no issue. If it's within realistic cruising speeds ranges, then for anybody who does want to cruise far and wide it's worth thinking about. when far from help, exposed foils like that are not that smart imho. All probably not an issue for GB owners because they're unlikely to be really cruising and have bought the boat for showing off. Like their maserati, unreliability, high repair bills and depreciation are acceptable downsides of looking like the guy in the ad.
  5. bigmarv

    Gunboat 68

    Yes, although more complex for more highly loaded gb ones. plus you need to get the builder the design files (easier if original builder solvent). then get to airport, somehow install if no hoist etc. Kickup boards are a bigger compromise and harder, but kickup rudders have been successfully executed on a range of fast cruising tris and cats. There's not much performance compromise and relatively speaking not that much expense for the most important moving part on a boat.
  6. bigmarv

    Gunboat 68

    Yep, agreed. But most of them are lucky to do a 200m day so when they hit something it's different. At very high speeds hitting a whale/log/container/growler involves phenomenal loads. You can design a keel or foil to survive an 8 knot collision. Doubling or tripling that speed and it's not the same. Losing keels/fins/rudders seems an acceptable risk for ocean racers, but family boats rightly get conservative. I agree kick up foils compromises performance, but I think a lot of people would let the boat run faster on average on passage if the boat was more likely to tolerate a bump. The drinking tea while doing 20 knots stuff from gunboat is sales patter, and they're not first and foremost a race boat. Their ocean passage speeds don't seem to be that fast, especially with an owner onboard, for all the obvious reasons. If you want to cruise fast and not risk 6 months out rebuilding rudders with a boat that doesn't fit lots of hoists, kick up seems like money well spent.
  7. bigmarv

    Gunboat 68

    It seems pretty obvious that if you're wanting to be far from help and yet sail fast it's unsafe to be choosing between either a sudden stop or catastrophic failure. Kick up foils just make sense. Rudders are important, and so is keeping the water out. And a dead stop from speed would be really ugly. What does your spinal column do if you're in your bunk and slam head first into a bulkhead at 20knts? Anyway, gunboats aren't for that sort of sailing. They're for showing off near the islands and then having paid crew do the long miles, then paying others to do the endless maintenance. The whole concept offers almost no lessons for people who don't have that ethos.
  8. bigmarv

    Gunboat 68

    dcnblues, you seem to be in the final stages of designing your breakthrough catamaran. can you post some renderings?
  9. bigmarv

    Expedition style motor yacht thread?

    You're saying that even the worst emitters should not do anything to reduce needless emissions because somebody else is emitting something. Fabulous. On that basis the worst emitters can justify business as usual while the world cooks because there's a hypocrite out there, or because they're only a small percentage of emissions. You won't need to do much thinking or reading to see that your argument is absurd. The climate change stakes are now very high and needless burning for pleasure is a menace. It should be called out.
  10. bigmarv

    Expedition style motor yacht thread?

    You total wally. The problem with massive consumption isn't just about scarcity, it's about climate change. The reefs are dying right now, you idiot.
  11. bigmarv

    Gunboat 68

    when you're too timid or fat to pay to be carried up everest...
  12. good stuff boardhead. sounds great.
  13. Sail4 - if you can easily and cheaply manage that with your 28 foot bulb keel boat then go for it, but you can't. The point here is that you can with fast multis. It's pretty different if you leave local waters. a bent rudder shaft, or a hole ripped in the bottom of a boat a long way from a hoist or help is not funny. Different rudder risks on your mono with a keel always in the way. but then what modern thin keel could withstand a dead stop hit at 25 knots?
  14. if rudders only ever hit on the tip a few inches' movement before stopping is not much at those speeds and forces. and unless the spring is extraordinary most of the velocity will still be there when it hits the stop, so I really don't think he's hitting something massive and solid (gentle sloping sand, quite different) at the high speeds and being relaxed. a break off tip on a rudder only protects against low impact. fast low rocker multis will take most floating objects higher up. have a look at the diameter shaft on monos designed to survive rudder impact at much lower speeds. you just can't fit that on a good high speed foil. i seems very obvious that a kick up rudder can be designed robustly and that it will cope with impact better and more safely. True, you might have low impact risk where you are especially if the whales are gone, but in the rest of the world it's not like that. whales, containers, ice, whatever. waterlogged logs from major rivers that roll easily under the hull barely slowing you until they hit the board or rudder. that sort of thing. if you`re coastal sailing where you are then care in the shallows covers much risk. on long passages and in many areas not so. rob`s just right about that i think.