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Waypoints for the Rio Dulce Bar

 
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Rule Britannia
Super Senior River Rat


Joined: 08 Sep 2009
Posts: 254

PostPosted: Thu Jun 03, 2010 2:19 pm    Post subject: Waypoints for the Rio Dulce Bar Reply with quote

Waypoints for the Rio Dulce Bar

Since it is the time of the season for the deep draft boats crossing the bar I would be interested to know what waypoints people are using. Especially boats drawing more than 6 feet

I have found 2 sources of waypoints (which are close).

Sources Waypoint
Eco Rio brochure Outside of the Bar N 15 49 299 W 88 44 734
Freya Rauscher Outside of the Bar N 15 50 080 W 88 43 890

Eco Rio brochure Inside of the bar N 15 50 100 W 88 43 960
Freya Rauscher Inside of the bar N 15 49 250 W 88 44 760

Eco Rio’s course coming in the river is 222ºM

Freya Rausher’s course coming in is 224ºM

Rumour has it that heading from the Sea Buoy to 2 houses to the south of the canyon entrance has a bit more water than heading to the south side of the canyon

What waypoints did you use and how did they work for you?
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elpolvo
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Joined: 18 Oct 2006
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Location: rio grande y rio dulce

PostPosted: Thu Jun 03, 2010 9:21 pm    Post subject: Reply with quote

rule B-

from my crossing experience, research and drinkin'-n-thinkin' sessions with people very familiar with the "BAR"
(if you know what i mean)... i've concluded that the bar is basically a flat, evenly spread out silt deposit with
normal underwater ripples and dunes that change frequently. there is no channel (dredged or natural) across the bar.

let's look at the sattelite photo from a year or two back...

here's EcoRio's course:



you can see, even without plotting it, that rauscher's course would not make much difference.

it looks like a dune has built up clear across the entrance but who knows if we're really seeing bottoms in this photo?
but just for the sake of conversation, let's say that we ARE seeing the bar through the water.

look closer, who's to say some southward jog around the dune might keep you in deeper water?
or is that shallower water? hmmmmmmm.



and who's to say the bottom across the bar hasn't changed since that picture was taken?

i think there's nothing better out there for bar crossing advice than casey's "Running the Bar" article.

if you can pick a crossing tide with east winds it will make that tide higher than forecast on tidetables.

have a plan B for what you'll do if you get stuck.

this could become an interesting and aromatic thread topic if we can get some of our "bar"mates to each chip in their two scents.
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ontno1
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Joined: 10 May 2007
Posts: 113
Location: Rio Dulce & Texas

PostPosted: Thu Jun 03, 2010 10:16 pm    Post subject: Reply with quote

I plowed across the bar last January using Brooks/Rauscher waypoints, there's not much difference between the two. Started at the sea bouy and headied toward the South promontory. I never found a channel, never found water deeper than 6'. With a 6' 4" draft I could only heel the boat as much as possible and wiggle through the soft mud bottom. The tide was about +1.2.
When I do it again, I will wait for the highest tide and try, as suggested by some Livingston locals, a little more South of the suggested route.
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Scoop
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Joined: 19 Oct 2006
Posts: 3747
Location: On board m/v Steel Magnolia, Rio Dulce

PostPosted: Fri Jun 04, 2010 8:01 am    Post subject: Reply with quote

elpolvo wrote:

Quote:
you can see, even without plotting it, that rauscher's course would not make much difference.


Even though it may not be apparent from high altitude photography, I'm convinced that it is a less "bumpy" ride using the EcoRio brochure's waypoints listed above instead of Rauscher's.

Elpolvo is correct ... there's not much difference on the chart -- but it seems to make a difference to simply move about 100 feet or so to the south of Rauscher's waypoints. We made several crossings last year on the Steel Magnolia towing disabled boats across the bar and heading to Estero Lagarto (elpolvo was onboard for a couple of them).

If we followed Rauscher's waypoints, we'd go bump. With EcoRio's waypoints, no bump.

I'm convinced there's a bit more water along that route -- perhaps a slight depression in the mud bank. Deeper draft vessels such as s/v Gertrude and s/v MoonBow followed us on that route and had no problem. It also appears to be the same route that the Livingston fishermen use early in the morning, even though they don't have the draft considerations that most cruisers do.

Another discussion of the waypoints is here: http://riodulcechisme.com/bbs/viewtopic.php?t=3065

Don't rely on the position or color of the sea bouy. It changes periodically.

And ignore those little floating markers with the flags -- they aren't "channel" markers but rather fishermen's markers. I made the mistake of following them the first time I crossed the bar seven years ago and quickly ran aground. Had to get the local lancheros to tie onto our mast and heel us over to get back into deeper water.

Thanks for starting this thread, Rule Britannia. We certainly hope to hear from the 6' 6" and 7 foot draft boats and learn which waypoints they use.
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Rule Britannia
Super Senior River Rat


Joined: 08 Sep 2009
Posts: 254

PostPosted: Fri Jun 04, 2010 10:23 am    Post subject: 2 Bars or 1 ? Reply with quote

I went out with Mike from Texan Bay a couple of years ago to help a boat of 7 foot draft across the Bar

When we got to the boat it was firmly aground in 6 foot of water, we got the crew to sit on the bow and swivelled the bow off to the south of their track where there was a little bit more water, once they where moving again no problem

Before we tried to get them off using Mike’s depth sounder on the Luancha we actually found 2 bars.

The first is roughly in line with the first headlands to the north and south of the river as you leave Livingston. The second is in line with the next 2 headlands further away.
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Deadly Nightshade
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Joined: 07 Jun 2010
Posts: 3
Location: Rio Dulce y Somerset

PostPosted: Wed Jun 09, 2010 7:43 am    Post subject: Waypoints for the Rio Dulce Bar Reply with quote

Rio Dulce Entrance:

An important contribution, but it looks as though Rule Britannia has inadvertently transposed two of the waypoints – namely those he attributes to Eco Rio. The one given as outside the bar is, in fact, inside it and vice versa!

Our own vessel draws between 6ft 10 inches and 7 feet depending on load carried – water, fuel, spares, crew, etc. so we fall within the range where we need to consider carefully when and how to cross the bar. So far we have come in, or rather through, the bar twice and out once. On each occasion totally under our own steam.

The issues we consider are, where is the best route, what is the best time and what is the influence of the weather.

As to route, having decided on a suitable time (see below), we have used the same sources as previously mentioned, and the waypoints for our three crossings are – for entry:

1. Outside the bar WPT outside 15 deg 50.183 mins N; 088 deg 43.941 mins W
2. Inside the bar 1 WPT inside 1 15 deg 49.360 mins N; 088 deg 44.729 mins W
3. Inside the bar 2 WPT inside 2 15 deg 49.301 mins N; 088 deg 44.914 mins W

On the way in we look for the point where the two red and white cell-phone towers come in to line, which is about ‘WPT inside 1’ then head in towards the town.

To respond to the satellite view shown previously, another recent one appears to show two possible parallel channels – one close to the routes we have been using and another one directly towards the gorge? Could be a useful project for a sortie out into the entrance on a calm day with a handheld echo sounder and make a transit between the headlands either side?

I guess we would all agree the best time is on a rising tide and for us it needs to be within the hour preceding high water.

The times and heights for high water are given on the Maya Paradise site. Both the times and heights are predicted and theoretical, i.e. they are estimates and ONLY estimates. They are also both affected by the present and previous weather history so for captains of vessels as deep as ours they should be used with caution! For example, taking a tidal height to two significant figures of decimal point as fact is pointless, if not irresponsible.

As well as looking at the Maya Paradise site there is also a useful, and free, tidal program on the net called WXTide32 that I have known work well elsewhere. Interestingly, it gives the same tidal heights (to just one decimal point) as Maya Paradise, but about an hour later. It would be interesting to know what the true times really are. Again, they are both theoretical times and I tend to opt for a notional Time of High Water between the two and start our crossing near the earlier one.

On the matter of height of tide, the heights predicted by both the sources quoted take no account of the present or previous weather, nor of barometric pressure. For those WAFI’s familiar with cruising the East Coast of the UK in the North Sea it is no surprise that changes in the barometric pressure can affect a tidal height by up to 12 inches. Fortunately at the Rio entrance the barometric pressure may not vary by much more than 10 mbar, but this could still lead to a 4 inch change in the predicted tidal height.

Now bring in an influence due to strong winds and currents coming in from the North East – that could help us quite a bit by pushing water back into the bay, conversely SW winds could take it out.

Hope this helps!
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elpolvo
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Joined: 18 Oct 2006
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Location: rio grande y rio dulce

PostPosted: Wed Jun 09, 2010 11:48 am    Post subject: Reply with quote

deadly-

that's a very informative and thought provoking post. thanks. i never gave a
thought to the barometric pressure's effect on sea levels. sometimes
every inch is important.

here's something i googled up on it:


The effect of air pressure on tidal height is substantial and all too easy to forgetten. The invisible medium in which we live has a not inconsiderable weight causing an effect which can be embarrassing at times!

The weight of the atmosphere creates a force pushing down on the sea. Perhaps surprisingly, one cubic metre of air at sea level weighs about one kilogram. A rough guide is that a change in pressure of one hectoPascal (one millibar in days gone by) will change the sea level by one centimetre. Tide tables assume a standard pressure of 1013 millibars. This means that a pressure of 1040 mb, pretty high but not abnormally so, could give a sea level lower by nearly 30 cms than expected. That could make the difference between crossing the sill and ignominiously hitting it.

The lowest pressure recorded around the British Isles is about 925 mb which would give sea levels nearly a metre above tide table predictions. This can be an important factor in storm surge conditions when the East Coast is threatened. Unless air clearance is critical, a skipper is unlikely to worry overmuch about too much rise of tide. The highest pressure around the UK is about 1050 mb which would give sea levels about 40 cm lower.

In a nutshell, worry about the pressure effect if the pressure is higher than 1020 mb and your depth is getting critical. I speak as one who just touched the sill at St Peter Port and had to be helped off!.


http://weather.mailasail.com/Franks-Weather/Pressure-And-Tides
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elpolvo
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Joined: 18 Oct 2006
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Location: rio grande y rio dulce

PostPosted: Wed Jun 09, 2010 12:05 pm    Post subject: Reply with quote

another little thing worth mentioning on this topic...

having another boat pass by close to you and send its wake
in your direction can give you just enough buoyancy to keep
making progress (or get unstuck).

last time i crossed with scoop on the steel magnolia, we were
at mid-to-low tide. the ship was touching bottom and dredging
a small trench with the keel. scoop added more power from the
diesel cats as we began to slow down. we almost came to a stop
just before we got inside the bar... then, one of the colectivo water-taxis
crossed our path at 90 degrees about 50 yards in front of us.
the resulting wake gave us enough lift to pick up a little more
speed and make it over the bar without getting stuck.

i think it was an intentional courtesy on the part of the colectivo
driver ...a classy move by a fellow boater.

-polvo
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mots
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Joined: 19 Oct 2006
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PostPosted: Wed Jun 09, 2010 3:54 pm    Post subject: Reply with quote

The Web Footed one wrote:

Quote:
sometimes
every inch is important.


Please, Kind Sir, quit teasing Peaches. It seems to give Mama the vapors.
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Celtic Dancer
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Joined: 15 Jun 2010
Posts: 380
Location: Rio Dulce

PostPosted: Fri Jul 16, 2010 2:16 pm    Post subject: The Celtic Way of crossing the bar Reply with quote

Ok first be un celtic and keep the drinks for when u are alongside yeeha
I came across the Bar 6 weeks ago on a good tide. My boat draws 7 ft 3in and I had a simple trick up my sleeve. Before crossing I put a dingy over the side but still in the air. Then with a few buckets of water dumped into it I connected the boom to the halyard and pushed it out and the boat leaned 22 degrees. One boat ahead had to get towed over as he got stuck with 5ft5 draft and the two boats behind me also got stuck with 5 ft 7 and 6 ft drafts. I never even touched. When I was over the bar I simply pulled the bung out and emptied the dingy.
Tips..
Use the topping lift or main halyard to hepl support the end of the boom.
Make sure u have a balanced sling made up for your dingy to support and recommend 3 lifting points.
All the best and have fun.
Cool
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Catamariner
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Joined: 04 Jan 2008
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Location: Anadromous

PostPosted: Wed Aug 04, 2010 11:53 pm    Post subject: Reply with quote

That's the Okeechobee Limbo with a more extreme lever arm Smile
http://www.youtube.com/watch?v=ZpX_2akoPzA
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