AIS CPA and TCPA for Solo Sailors

[GILow]

Originally Posted by roland stockham

I have used AIS quite a bit both solo and 2 handed. Not found the CPA alarm very useful. The way I use it is to alert me to the presence of ANY shipping in the vacinity. I usually have it set at 30m offshore but reduce the distance to 15m approaching coastal areas. If there is nothing visable on AIS I am happy to sleep withe ste radar guard set (looking out for non AIS vessels such as other Yachts). If there is anything on the screen I am on watch athough I may catnap. I can go 2 or 3 days like this but then need a full 8hr. The balance has to be knowing when a full watch is essential butnot getting so tired you start making serious mistakes.

Excellent! A very nuanced approach, thank you. I think I for one will be trying this out, just to see how it feels. Not how I would have originally considered using AIS myself.

[Wotname]

Originally Posted by GILow

How's this?

Looks almost perfect. I can't tell from the picture but is there any gap at all between the bottom of the rudder and the hull i.e. how is the bottom of the rudder attached to the keel

[GILow]

Originally Posted by Wotname

Looks almost perfect. I can't tell from the picture but is there any gap at all between the bottom of the rudder and the hull i.e. how is the bottom of the rudder attached to the keel

It's pretty well flush with a slight jump up from the base of the keel to the rudder from memory. Maybe an inch or two up, and a small gap, also an inch between the back of the keel and the leading edge of the rudder. So there's a gap, but it is small.

I remember when we collected the boat from Melbourne, we had to navigate the lobster field from Melbourne to Adelaide. Luck was on our side, there was another Swanson 42 in the yard on the hard stand so we were able to plan our lobster pot snag recovery by looking at the underside of an identical boat. Looking at it, we felt that we'd be unlikely to snag anything unless we were very unlucky and as it was, it had been a bumper season and all the lobster quotas had been fulfilled so we only saw a handful of pots on the whole journey.

Fingers crossed.

[Jim Cate]

Matt, you might consider putting a deflector plate, mounted to the keel and extending aft across the gap. This would pretty well eliminate the possibility of a line getting caught in the gap, and the rest of your hull looks pretty snag free.

Just a short length of say 25x6 s/s bar with a couple of screws into the glass would do the trick. We have a sorta similar device covering the vertical gap between our partial skeg and the lower part of the rudder. Very simple and very effective.

Jim

[GILow]

Originally Posted by Jim Cate

Matt, you might consider putting a deflector plate, mounted to the keel and extending aft across the gap. This would pretty well eliminate the possibility of a line getting caught in the gap, and the rest of your hull looks pretty snag free.

Just a short length of say 25x6 s/s bar with a couple of screws into the glass would do the trick. We have a sorta similar device covering the vertical gap between our partial skeg and the lower part of the rudder. Very simple and very effective.

Jim

Thanks Jim, that’s a great idea. I was toying with the idea of a quick pressure clean before the journey. Not essential, she’s pretty clean, but if I do I’ll add what you suggest.

[JPA Cate]

Originally Posted by GILow

Thank you Jim. A different mix of numbers again to those previously suggested. And from one of the faster boats in the fleet on CF.

Interesting to try to interpret that if I can. Will think some more.

If you do that, see if you can put some bottom paint on it, too.

Ann

[Albro359]

This thread has deteriorated..it's no longer about the OP's question.....
We set a proximity alarm 15nm....then look and see what's going on...don;t worry about CPA or TCPA alarms at all
AND if solo at night I always have the radar on watchman...does a scan every few minutes....
BECAUSE where I sail there are a lot of Asian fishing boats, no doubt fishing illegally, that turn their AIS off !
I was surprised one dark rainy morning in south Vanuatu to see a fishing boat, big one, lurch out of the murk about 100m behind us...no AIS, no lights, nothing.

[GILow]

Originally Posted by Albro359

This thread has deteriorated..it's no longer about the OP's question.....

We set a proximity alarm 15nm....then look and see what's going on...don;t worry about CPA or TCPA alarms at all

Ouch! I had that coming! Fair call. [emoji846]

Another interesting approach to AIS alarms to consider too. Thank you.

[GILow]

Can I just say, in my defence, I didn’t say anything against thread drift per se. I just mentioned that the whole “to solo or not to solo” debate is raging elsewhere and I didn’t want it to creep in and hijack this thread. Given the nature of the question I posed I saw this as a real risk.

[mrm]

Threads often go at a tangent to the question, but still have good advice. For example the mention of being awake/rested enough to interpret situation correctly when alarmed is spot on, so let me add another non-direct but related post. I think it is worthwhile to ensure your nav lights are as bright as possible and I would prefer a tricolor on top of mast to the separate deck level lights for those times when you really need a longer nap. Anything to help other vessels pick our presence well in advance is good.

[Jim Cate]

I am a bit nonplussed by all the folks who don't pay attention to CPA alarms. IMO, if you are napping and in real need of sleep, being awakened by proximity alarms generated by vessels who are not going to come anywhere near you is counter productive.

Hence the CPA alarm: if the boat isn't being threatened by a distant ship, why wake up to discover that fact?

Jim

[GILow]

Originally Posted by Jim Cate

Hence the CPA alarm: if the boat isn't being threatened by a distant ship, why wake up to discover that fact?

Jim

Begs the question, if a ship passes in the night, and the CPA alarm doesn’t sound....

Actually, I’m not sure where I was going with that.

[Wotname]

^^ ya need a nap

[Wotname]

Originally Posted by GILow

It's pretty well flush with a slight jump up from the base of the keel to the rudder from memory. Maybe an inch or two up, and a small gap, also an inch between the back of the keel and the leading edge of the rudder. So there's a gap, but it is small.
......

IMHO, that gap is way too big. If you can, take Jim's advice and fit a deflector plate or stay away from cray fields at night. I fitted something similar and it worked well.

Maybe my fears are not warranted but having been anchored by the rudder in the past in the dark in fresh weather with a hostile lee shore, I would hate for you to have to go though the same.

[El Pinguino]

Set the CPA alarm for 10 miles..... and I'll be suprised if it goes off more than twice on your trip... when 'off soundings'...

Moderate traffic? We used to call the waters between the bottom left hand corner of Straya and Cape Otway the 'Empty Quarter' .. due to the lack of traffic.

Speaking of 'off soundings'.... stay well off the shelf for as long as you can... that sorts a lot of the problems re pots'n'stuff.... and gives you sea room if the weather goes T/U and you have to hove to.

You will of course be keeping a constant lookout by eye, ear, nose and throat? If you don't they shall throw you in the slammer on arrival in Hobart Town and you-- won't--come--out.......