Confessional: admit to boat-related things you've never quite understood...

[RAI]

Why is there not a decent 12V DC plug and socket? Using a cigar lighter socket is ridiculous.

 

[laika]

Which way round should you wire a 2 pin dri-plug? Obviously if you're wiring up a plug and socket it's whatever you want. According to the manufacturers there is no convention. But I can't help feeling there should be (e.g. +ve to the right looking into a socket).

 

[xeitosaphil]

" Coach bolts have a domed head, almost flat so they look neat and tidy when assembled, underneath which is a square section which pulls into a square hole so it doesn't rotate when the nut is tightened at the other end."

These can also be called " CUP CUT SQUARE " Bolts

 

[RAI]

Which way round should you wire a 2 pin dri-plug?

I have some through deck sockets that use thick and thin pins, so there is only one way round for the plugs. I chose to wire fat = positive. Maybe it should be the other way? However these are a bit bulky for internal use. I am pondering the virtues of using telephone jacks. The question is driven by a cooler box that draws 5 amperes and cooks its cigar lighter plug.

 

[RAI]

Look up "flemings right hand rule" for alternators. Think of the plumbing in your house for wiring.

I'd rather not water and leccy don't go well together. I am currently revising for my Nigel Calder exam.
All alternators are not equal.

 

[RAI]

You can see it if you bend over.

Does this require jeans?

 

[Roberto]

But... I still don't understand why the heck I should care?

You may well skip all the calculations and button pushing, in practice what is most important is to have a rough idea of the magnitude of the difference between the two.
Suppose you are sailing downwind at 7kt, full sails, you feel a nice breeze say 15-20kt (apparent as wikipedia instructs).
Then you want to turn by about 90°-120°-180° around that cape at the end of an island to head for a sheltered anchorage in the lee of the island.
Once you get to the cape (even without local effects) and begin turning to beat towards the anchorage, the apparent transforms into 25/30kt while you are with full sails...

I suppose it's one of the reasons one sees so many engines started at that point

 

[Melleman]

I can never quite get my head around prop-walk when in reverse.

http://www.ybw.com/forums/showthread.php?341281-Prop-walk-Pysical-reason-why-does-this-happen/page5&highlight=fysics+propwalk

Post #42 and #11

 

[TonyBuckley]

You may well skip all the calculations and button pushing, in practice what is most important is to have a rough idea of the magnitude of the difference between the two.
Suppose you are sailing downwind at 7kt, full sails, you feel a nice breeze say 15-20kt (apparent as wikipedia instructs).
Then you want to turn by about 90°-120°-180° around that cape at the end of an island to head for a sheltered anchorage in the lee of the island.
Once you get to the cape (even without local effects) and begin turning to beat towards the anchorage, the apparent transforms into 25/30kt while you are with full sails...

I suppose it's one of the reasons one sees so many engines started at that point

Excellent description. "Apparently" (sorry) I understood this without realising. It's just sailing! I get it now and don't need maths - woohoo. What a fab diverse thread!

 

[Avocet]

Can just about remember the Carnot cycle from my thermodynamics lectures, but no, I'm not confusing the two. If the engine is running colder, the cylinder walls, head and manifold will be a bit colder too - which all helps keeps the heat gain of the incoming mixture to a minimum. The effect isn't great, as you say, but there are usually a few more horses to be had.

 

[NormanS]

Main use of true wind is when motoring due to lack of breeze, but hoping it will fill in enough to be able to sail. The apparent wind from moving forward keeps tempting you into thinking that you'd be able to sail; the true wind display tells you whether there really is.

Personally I wish I could set my ST60 to display apparent wind direction with the dial, but true wind speed in the LCD window. I rarely care about the true wind direction or the apparent wind speed; without this mode I'm always flicking back and forth.

Pete

My burgee and bits of ribbon on the shrouds, are firmly locked on to apparent wind.

 

[winsbury]

I get how an instrument measures apparent wind but how on earth does it know true wind without some nifty sog calcs?
.

 

[Humblebee]

Does that mean Apparent Wind, is a red bus?

Can't speak for other boats but the old Royal Yacht had one in the engine room. Purely decorative!

 

[Stork_III]

I get how an instrument measures apparent wind but how on earth does it know true wind without some nifty sog calcs?
.

Exactly how it works Using SOG and Track, or STW if no GPS signal.

 

[winsbury]

Thank you...I had assumed it was all done in the wind instrument without external assistance, it makes sense now.

 

[ChiPete]

I can only imagine I'm in the company of emeritus mathematicians - 156 posts and no-one's said the dreaded word......celestial navigation

Here's the challenge - explain celestial navigation in the same succinct manner that allowed me to understand lee bow.

Re true and apparent, it's my understanding that when beating the wind moves forward so you have to trim the sails accordingly. I do find myself checking the ST60 as SWMBON switches to true. Mind you she always seems to get another knot out of the boat

 

[VO5]

I can only imagine I'm in the company of emeritus mathematicians - 156 posts and no-one's said the dreaded word......astro

Here's the challenge - explain astro in the same succinct manner that allowed me to understand lee bow.

Re true and apparent, it's my understanding that when beating the wind moves forward so you have to trim the sails accordingly. I do find myself checking the ST60 as SWMBON switches to true. Mind you she always seems to get another knot out of the boat

It is not "astro"...it is Celestial Navigation...if you don't mind.

"Astro" is seagoing slang.

 

[Woodlouse]

Exactly how it works Using SOG and Track, or STW if no GPS signal.

Pretty sure they use speed through the water and heading rather than SOG and COG.

 

[ChiPete]

It is not "astro"...it is Celestial Navigation...if you don't mind.

"Astro" is seagoing slang.

My abject apologies VO5, I am guilty of the nautical equivalent of text speak! Duly edited.

So, vocabulary fixed, what's the answer???

 

[AntarcticPilot]

Pretty sure they use speed through the water and heading rather than SOG and COG.

The ST60 certainly only uses log speed, not SOG from the GP. I know because my log has been playing up and I don't get true wind without it. You don't need heading as the angles are given relative to the boat, not to North. So the things you need are Wind speed, Wind direction (both from the wind instrument) and speed (from the log).