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MathiasW

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About MathiasW

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    Bluewater
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    living aboard and everything around it

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  1. Well, if you say so... The boat parameters are entering the equation, so yes, it does depend on the boat. And more so than the stupid 3:1 scope rule... The keel will affect how the vessel will move at anchor, but this is also entering the equation via the vessel velocity at anchor. So, in a first approximation, it is all taken care of. Anyway, I know not all will appreciate this, but I hope some will find it useful.
  2. Sentinel, or kellet, is something that helps, but not a lot. If you want it to use to reduce shock loads, you need to place it in the middle of the chain. If it is for reducing the swinging circle, you need to place it as close to the anchor, but not touching the ground. In both cases its maximal effect is that of a chain with the same total weight. So, if the kellet weighs 10 kp, and you are using a chain that is 2 kp per running metre in water (i.e. 10 mm chain), then your kellet is more or less equivalent to 10/2 = 5 metres of the 10 mm chain, at best. To me this is only a marginal improvem
  3. On the first point, I cannot agree. The snubber's main and primary function is not to protect the windlass or the bow roller, but rather to reduce the maximal anchor load to begin with. As a consequence, the bow roller and the windlass will be less strained as well. But it is the reduction of anchor load, which is the main thing, as this will determine whether the anchor holds or not. And yes, 100 metres of chain in 10 metres of water is good. Chain likes depth. Only then can the catenary effect really unfold. On this point I am fully with you. To understand this - consider a chain t
  4. Well, that's what he is using when push comes to shove. His bridle is also running on the entire boat length, and so only half of it is in the water. It is not his normal day-to-day bridle. Sounds like your snubber is perhaps 15 metres long. Same as my bridle. With a maximum stretch of 20% this yields 3 metres of stretch that is allowed! Now, if your snubber is made of too thick material, it will never stretch that much. But it really should stretch in the range of metres to keep the loads at bay.
  5. Chain catenary is at the core of the calculations, actually. This, plus adding the snubber / bridle with matching loads is essentially the model. And if you have not seen a snubber that stretches to 1.6 metres, then you have not seen an excellent snubber yet. These long stretches are needed to absorb enough energy in the snubber whilst still keeping the load reasonably low. Have a look at what Jonathan Neeves says about snubbers. His snubber is 30 metres long.
  6. Anchoring is a very controversial topic, I know! Still, I would like to put forward a free tutorial tool my son and I have created that allows one to estimate the maximal anchor load and the minimally required chain length after providing input parameters for the vessel as well as sea and weather conditions (i.e. swell and wind / gusts). It works with various physical units, like daN (deka Newton), kp (kilo pond), or imperial units of pound and feet - the button on the top far right. Depending on which country you are coming from, the tool will try to make an intelligent guess to set the defa
  7. For iPhone I have now settled for AnchorSentry.
  8. They do have anchor alarm, but afaik you can not position the anchor after the fact. They only allow a circle around the current position of the boat. If you have moved away from the anchor position already, you are screwed.
  9. GPS as built into phones are for sure not as accurate as a GPS with a proper antenna of a boat. However, GPS measures position and not movement, which is only a derived quantity, so it does not matter how slow you creep. It will catch it. Not with a metre accuracy, but with a few meters accuracy.
  10. Added SafeAnchor for Android to the overview. It has quite some features, but a rather unusual way of defining the anchor radius and anchor position, which takes some time getting used to. https://trimaran-san.de/anchor-alarm-apps-overview/
  11. Some hate anchor alarm apps, other love them. For us, living on a boat with just two persons, electronic aids are a must. We cannot afford to be awake half of the night, every night, for years on end. Thus, for us, anchor alarm apps are just one more arrow in the quiver, nothing more, nothing less. And they can operate even when we switch off all other electronics in a thunder storm. So, in an effort to get a better overview of all the anchor alarms available, I have done a survey of most anchor alarms for iOS and Android and put all this in a long chart where I just list the feature
  12. Sorry to be late to this, but I have recently done an extensive feature survey of some 50 Anchor Alarm Apps that I could find for iOS and Android. I hope this will be useful for the community. Here is the link: https://trimaran-san.de/anchor-alarm-apps-overview/ Cheers, Mathias
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