School Boats and Tidal Heights?

[nealeb]

Years back I did a Coastal Skipper course out of the Yealm. It was my turn to navigate, and I did the sums to get us into Looe. We arrived early and the instructor told us just to try going in anyway - no sense in stooging around if there was, in fact, enough water. We touched and stuck for a little while and eventually did manage to get in at about the expected time, and reached the chippy well before closing time. On the other hand, it was a fairly calm evening, no swell, the tide was rising, and we knew what the bottom was like in the entrance. After all, just as there "might" have been a shallow patch, there "might" have been a deeper patch! Instructor reckoned that if she didn't go aground at least once on a course, she wasn't trying hard enough. In retrospect, seems like a reasonable attitude as long as you understand what you are doing and where.

Not sure that I would back out and take a run-up at a known obstruction, though...

 

[srm]

"Instructor reckoned that if she didn't go aground at least once on a course, she wasn't trying hard enough."

Obviously not her boat.

Is deliberatly risking running aground just to see if you can get in early realy a reasonable or seamanlike attitude? There may also have been a hard patch and / or a large mobo slowing just enough to drag its maximum sized sternwave which will increase in the shallows . . .

Not something I would choose to do or teach, (with the exception of parking a catamaran with reinforced keels as close to a sandy beach as possible).

 

[jimi]

Are'nt you being overly cautious? Soft bottom,rising tide,flat calm ... what's the problem?

 

[Elessar]

Do you do tidal heights and sec port calc's or are they a waste of time?

Without the luxury of a lead keel, my 2 £500+ each props touch the bottom first so knowing how much water there is is quite important to me. Even a soft bottom is not good to touch as props damage easily.

But I only work out secondary ports properly when doing a passage plan in advance where the height may effect me and I want to make a decision about timing or work out a window.

To know what the tide is right now or what it will be when I get somewhere I just look up the nearest T diamond on the chartplotter. So easy to do, why mess around?

 

[Poignard]

Jimi wrote: Are'nt you being overly cautious? Soft bottom,rising tide,flat calm ... what's the problem?
________________________________________________________________

As you say: 'what's the problem'

The problem is that of people who don't seem able to make rational 'judgements' about when something is important and when it isn't.

Feeling your way upriver on a rising tide is perfectly ok in my book, as long as you ground on the weather side of the river. It's not the end of the world if you do ground on the lee shore but you have to go to the trouble of running a kedge out. Being early also gives the advantage that you can often see the course of the river ahead.

For example going up to Totnes under sail this summer under sail I got aground twice and just backed the jib and off she came. Despite having a long-keeler I get a lot of pleasure out of exploring rivers that are not charted, where secondary port calculations are only of limited use.

I think part of the trouble lies with the RYA theory courses making students calculate tidal heights to within a few inches. This spurious level of accuracy seems pointless, because the real world isn't that accurate. Atmospheric pressure, wind strength, rivers in flood, human error all combine to screw up the most careful calculations. Surely it would be much better to teach students to glance at the almanac and do a simple mental estimate and get back on deck, instead of wasting time at the chart table drawing graphs etc.

As somebody once said: "An ounce of experience is worth a pound of learning'

 

[Refueler]

Jimi wrote: Are'nt you being overly cautious? Soft bottom,rising tide,flat calm ... what's the problem?
________________________________________________________________

As you say: 'what's the problem'

The problem is that of people who don't seem able to make rational 'judgements' about when something is important and when it isn't.

Feeling your way upriver on a rising tide is perfectly ok in my book, as long as you ground on the weather side of the river. It's not the end of the world if you do ground on the lee shore but you have to go to the trouble of running a kedge out. Being early also gives the advantage that you can often see the course of the river ahead.

For example going up to Totnes under sail this summer under sail I got aground twice and just backed the jib and off she came. Despite having a long-keeler I get a lot of pleasure out of exploring rivers that are not charted, where secondary port calculations are only of limited use.

I think part of the trouble lies with the RYA theory courses making students calculate tidal heights to within a few inches. This spurious level of accuracy seems pointless, because the real world isn't that accurate. Atmospheric pressure, wind strength, rivers in flood, human error all combine to screw up the most careful calculations. Surely it would be much better to teach students to glance at the almanac and do a simple mental estimate and get back on deck, instead of wasting time at the chart table drawing graphs etc.

As somebody once said: "An ounce of experience is worth a pound of learning'

Breath of fresh air ! Even Jimi - I have to agree with .... now that's saying something !

Ok - I have one of those 'orrid bilge keelers and I am famous for 'pushing mud' with the keels. Many a time getting into / out of Ryde Marina - I've been moving through mud. Getting in / out of berth at HYCO. Departing Newport Town Quay .... I've proved many a time that I can push through 20cms of mud ....
My home berth out here - when river level falls - I find that boat has keels into river bed. There is also a shallow patch as I exit my private canal ... boat just lifts and over as keel rides it.
Terrible I know ... but what to do ? I have no tides here in Latvia, but wind can drive water level + / - 40cms ...

Over many years - I've edged way into unknown havens .... with various types and styles of boats. As I stated in other threads - trusting Secondary Calcs is false security - it is only an indicator in IDEAL text-book conditions - which rarely exist. I prefer to look at nearest standard port tide table either side of where I'm going in ... mentally interpolate time ... then set my movement in as x hrs before / after HW / LW ... keeping it simple and not wasting time ...