nicknorman

We were in Tixall last week, oodles of space. In fact this was problematic because it was too difficult to decide which bit to moor at. It is so much easier when there is just 1 space!

The duty cycle limit (actually, a field current limit in my case) has some “ramping” (ie low pass filtering) applied on the way up, but not on the way down. So if the rpm goes up the field current limit will ramp up slowly, but if the rpm goes down it will rapidly reduce the field current limit, to avoid a transient high mechanical load. This seems to avoid any issue with noticeable “hunting”. And anyway there are still a lot of counts between idle (850 engine rpm) and 1300rpm - the latter being the point at which field current restriction is lifted - so even without the ramping I don’t think hunting would be noticeable.

On the speed resolution thing, this is just a feature of the LIN interface standard not the internal workings of the chip. The data field is 8 bits but it is somewhat logarithmic so the alternator rpm that I am operating at is way up near the top where each bit is worth a lot of rpm. It is annoying because one can burn some programmable "OTP fuses" on the chip to specify the number of poles, which would bring the reported alternator rpm down to mid-range where the resolution is much better. But unfortunately for some reason I still dont understand, NXP don't include how you do this on the data sheet (only that you can do it, and give you the bits to change) and refused to tell me when I asked nicely. Still, it is of no real consequence as it doesn't affect the operation of the device beyond the logging data. I really only included the graph to make you jealous of the "taking full charge whilst at 98% SoC" thing that lithium batteries do!😁

Been down to the boat for a few days, thought I would generate some log data. The voltage and rpm data comes from the regulator chip - and the communication protocol does rather limit the resolution - and from the Mastershunt for the current and SoC. Graphs can be difficult to read when they have several different parameters but hopefully one gets the idea that the scale for current and SoC is on the left, and for volts and rpm on the right. I factored rpm by 100 to make it work alongside voltage. The batteries are already well charged at around 94%. At the LH side of the graph I flick the target SoC switch to 100% and it begins charging. We are cruising and rpm is up and down for moored boats etc, since the setup is on field current limit to 2A, the charge current varies quite a lot according to rpm. But note that the current remains at 75 to 95A until the SoC is 97% - the joys of Li! In fact you can see that the SoC jumps from 98% to 100% as the Mastershunt synchronises itself when the current falls to 5% capacity for a couple of minutes. So in fact, the SoC where the current starts to fall was around 98.5%! When the system detects fully charged (current below 5% for a couple of minutes) the regulated voltage changes to 13.3 which is less than battery voltage, so you can see the battery current is negative (discharging) and alternator output is zero. However the rpm readout from the chip is unaffected due to the "phase keep alive" function I mentioned previously. Whether the phase output would also be enough to operate a tacho I am not so sure. Oh and you can see there is a lot of smoothing on the current trace, this is a function of the Mastershunt. I really should use the BMV712 current which is much more instantaneous, but this “currently” only goes to the BMS, it doesn’t get passed on to the regulator. I’ll need to change the code a bit.

Many many narrow locks, lots of BCN stuff. We like locks! The rubbing strakes get scraped of course, and they may go a bit rusty, but that is what they are for. The main thing I notice with bitumen blacked boats is the line of rust at the waterline. You don’t get that with a 2-packed boat. Even when you scrape it a bit, if the surface is properly prepared (blasted) the stuff is sort of ingrained into the surface so whilst it might look a bit scratched, it doesn’t rust much.

We had our boat blasted and 2 packed by Aqueduct marina on the Middlewich branch, just a short detour off your route. They are expensive, but they did a good job. We took the boat out 6 years later but we needn’t have bothered, other than the blacking had gone quite grey. Once cleaned up and before re-coating, you couldn’t see where the waterline was. As I think you know (but maybe others don’t) there is no point in putting 2 pack blacking on anything other than properly prepared (grit blasted) bare steel, or well-abraided previously properly applied 2-pak.

How can you tell? His expression looks rather blank to me.

I’ve not tried smidge, I’ll give it a go this summer.

There will only be battery voltage on D+ when the engine is running and alternator is charging. To get the alternator to start charging you would normally have a warning light connected (other end of the warning light to battery + via the ignition switch) and then, with the ignition on but not running, you would get a volt or two on D+, rising to battery voltage after starting the engine.

Don’t forget that most rudders have a proportion in front of the pivot/hinge, which can catch on something whilst going ahead and ram the tiller hard over. This happened to me. Perhaps your rudder doesn’t have a bit in front of the pivot (IIRC you have a “non-standard” rudder. So I say this mostly for the benefit of others.

If you look at the flight schedule Bristol - Inverness, although there is only 1 flight per day the flight times vary a lot according to day of the week. For example on Thursday it is 15:50 departure and you are in Inverness by 17:20. Not sure how long it would take you to get to Bristol airport, but if you can do it by air it means you don’t have to spend 3 or 4 days of your holiday driving on the M5/M6/M74/A9. Which is pretty tedious and knackering! Wednesday the following week for return trip, 16:40 departure gets in at 18:00. Or for the full 7 night Thursday return 17:55 to 19:15

Bearing mind I live in Scotland and spend a lot of time in the Highlands I probably have a good insight into Scottish midges. People say Avon skin-so-soft works, but not for me (and it stinks). The only thing that works for me is the netting. i also lived for a year in Borneo so I have a good idea about mosquitoes and insect repellant. Anyway, if one has insect repellant and netting in one’s luggage, the effectiveness and choice can be made at the time with no obligation to use either. If one doesn’t have netting and the midges are bad, IMO this will be regretted. Rain is good, drizzle is not good!

Doesn’t work! You have no idea what west coast midges are like! They are not mosquitoes.

Obviously it depends on why you are going, but neither Inverness nor ft William have much to offer in themselves, other than as a base for exploring the countryside or the waterway. The NC500 is very popular and the top of Scotland is very nice - awesome even - so that would be my recommendation, but obviously you would need to drive up (long way) or fly/train up and hire a car or even a campervan. You can fly Bristol to Inverness direct on EasyJet for about £100 each return which IMO is a no-brainer if time is tight. Under 1.5 hrs flight time Midges tend to be worse on the west coat, but they don’t like wind. Just pray for gales and that keeps them grounded. You can get netting to put over your head, which also comes in handy if you have an urge to rob a bank. This sort of thing… https://www.amazon.co.uk/midge-hat/s?k=midge+hat but don’t have bare shoulders like the foolish lady in the pic!

Re pulling paint off, remove the tape as soon as you dare, while the paint is still wet -ish.