Had some long lulls at Boombas today, so I stopped at Narimba Cay and walked around the three star-pickets at the middle point.






Her's the Cays co-ords



here's the Cays distance from shore







Here's the distance from shore of the outside star-picket (no 5), there are 4 others closer to shore, my tracks go to no 4 and no 3






The co-ords are
outside starpicket (5) -32.63112, 115.72020
(4) -32.63135, 115.72035
(3) -32.63152, 115.72042

I'll try to rember some plastic pipe to mark them next time we're there.

thank you for your efforts Mike.
How do I use those coordinates with the GT 31 to avoid hitting the cay?
Is that tip of the white area the shallowest spot? because the reef certainly extends ESE of there along that light coloured strip

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Windxtasy said..
thank you for your efforts Mike.
How do I use those coordinates with the GT 31 to avoid hitting the cay?

You have to have it set to "Navigation", the co-ordinates are then displayed. I think you can set the proximity alarm to warn when you get close.
But unless you have 2 units, you won't know your speed.
The main reason I got the co-ords is so I can find it again with some plastic pipe in my hand. And measure the distance out, some people have a very good idea of how far 700m is

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Is that tip of the white area the shallowest spot? because the reef certainly extends ESE of there along that light coloured strip

No that's just the end of my tracks, where my fin found some limestone. I didn't go walking around to discover the limestone's extent.

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decrepit said..

Windxtasy said..
thank you for your efforts Mike.
How do I use those coordinates with the GT 31 to avoid hitting the cay?

You have to have it set to "Navigation", the co-ordinates are then displayed. I think you can set the proximity alarm to warn when you get close.
But unless you have 2 units, you won't know your speed.
The main reason I got the co-ords is so I can find it again with some plastic pipe in my hand. And measure the distance out, some people have a very good idea of how far 700m is

I do have two units..

Is that tip of the white area the shallowest spot? because the reef certainly extends ESE of there along that light coloured strip

No that's just the end of my tracks, where my fin found some limestone. I didn't go walking around to discover the limestone's extent.

If you look at my track from May gpsteamchallenge.com.au/sailor_session/show?date=2016-05-23&team=12 we were crossing the reef further along and there was still limestone you could feel underfoot, although it was covered by mud and you couldn't see it.

Yes I guess we should do a bit of investigating to discover depths over the whole area. But I think a marker on the edge will at least warn us how far out it is.

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decrepit said..
Yes I guess we should do a bit of investigating to discover depths over the whole area. But I think a marker on the edge will at least warn us how far out it is.

yes please. One at each end would be great - it looks linear

I'll have to see how easy it is transporting pipe on a windsurfer. I suspect I'll only manage one at a time, And I think the star pickets are a higher priority than 2 markers at the Cay.
Unless I get some help of course?

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decrepit said..
I'll have to see how easy it is transporting pipe on a windsurfer. I suspect I'll only manage one at a time, And I think the star pickets are a higher priority than 2 markers at the Cay.
Unless I get some help of course?

Are you planning to put pipe over the star pickets? I thought they were fairly obvious when I was there an a 0.8 tide
I'd be happy to help if there are good Boombas conditions and I have a day off. Let me know next time you are planning to go there

How many did you see? we counted 5 on Wednesday on a medium tide.
They are easily seen in the right light if the tide isn't too deep, I almost hit one last week on the way back, and Wednesday I lost sight of them completely on the way back, on a high surge tide the outside one is completely submerged. Joe has come up with a nice bright orange post that will go over the outside one, and I've found a length of PVC that will be one marker for the Cay. I'm sorting my junk at the moment and may well find another length of pipe, we'll see.

I'll help too, I can bring my small boat over if it will be any help.

Hey Gav, you the man!!!!!!!!!!!!!!!!!! A small boat is just what's needed, as long as it doesn't need more than knee depth.

Text me when you want to do it, it'll be easy for the two of us with a boat.

I'll be free Wednesday and Saturday. I haven't seen the spot, so you pick a time the tide and surge will be good. The boat is not super low draft but should get in to knee deep with the motor tilted.

Has it got oars? not much point having to get out and push, I'll see what's happening wednesday, I'm free late morning.

No oars, it's not ideal if the shallows extend far at that area but will have to do unless someone can offer a punt or kayak?

Wednesday is showing a .73m tide around 1100, if positive storm surge as well that should be fine, but if it's negative probably too shallow.

The Cay is inside a nature reserve, I'll have to check the rules, I forget if it's a 5kt speed limit, or no motorised craft. If motorised craft aren't allowed in, we can probably walk to the Cay, or take my biggest board and a paddle.

Can't find any info on the big yellow buoys that mark the reserve, but the transport dept advice just shows 5kts, with the area in question obliterated by random notes.

I wasn't counting the star pickets but I would say about 5, evenly spaced. Sorry but I am working on Wednesday.

Looks like Wednesday is going to be a bit miserable with negative storm surge, so we'll try for the weekend.
I've found a couple more posts, so if we can get in with Gav's boat, it will be relatively easy to mark each end of the Cay, as well as the outside picket.

And figured out how to use the GT31, first you have to convert the decimal degrees into deg min and sec, leave the GT31 on satellites and scroll thru to 3rd page (GPS Fixed Info) that shows,

Time in UTC
Date in UTC,
Heading
Velocity, Altitude
Current Location
Coordinates
(in DDMM.MMM)

So the Cay is now 32deg 37' 40.404" X 115deg 43' 57.684"
And the outside picket is 32deg 37' 52.032" X 115deg 43' 12.72"

There is going to be negative storm surge on the weekend too. We should shoot for the morning when the tide is higher. At 0.8 m the water around the cay is only knee deep, and not much deeper near the star pickets, so we need about that much tide or it's a lot of wading.
I can probably do Saturday morning but not Sunday morning.
I also have a flat bottomed kayak which may be useful to get in closer if the draft of the boat is too deep.

Keep fingers crossed the storm surge isn't too great then, I'm not good at early starts! But there is a tidal delay across the estuary, I have a feeling Boombas is about an hour behind, 0900 is a bit more doable.
Gavin will probably launch from Novara, more later.

Forecast is now showing much better tides on Monday, higher, later with lower barometric pressure, and sunny, So it'll probably happen Monday morning.

BIG!!! thanks to Gavin, Basil and I joined him at Novara, and he took us to Boombas in his boat, water was a bit too low but we made it to the pickets without too much trouble. The pickets looked a little different since I was last there, there was now 6 of them, the outside one bent towards the east and only a mm or so above the water.

Either this was the same outside one we saw last week and it's got bent over, or it was always there hiding under the water. The other difference was the next one in was actually a twin, two posts very close together one short one long. I'll check my tracks later and see exactly what's happened.
Any way the result is, that Gavin in trying to straighten the outside one so we could place the marker over it actually pulled it out. We then tried the marker on the small post which was the next outside one, But it looked too low, probably would have been covered at high tide. So the marker is now on the high picket which is a good 5m further in.
SO DO NOT sail within 10m of the marker!!!!!

The boat only managed to get us half way to the Cay, with Gavin towing it. after it started to scrape the bottom, Basil and I donned wetsuits and we walked the rest of the way. so now there are 4 posts marking the southern end of the Cay, this is where the limestone is, the Northern end is just a very shallow sandbank, although we didn't walk the full length. 3 of the posts are in deeper water at the edge of the Cay, staying inside these should be safe, there's another one further in that marks 3 old broken starpickets, it's on the shallow sandbank so at high tide you may just be able to sail there, but coming off on the 3 rusty stumps wouldn't be good!
When I get chance to look at my tracks I'll post a pic.

Great work guys! Sounds like the lower tide was actually a bonus, revealing some previously hidden hazards.

The cay would have been out of the water in parts yesterday wouldn't it?
What was the time and tide when you were over at Boombas?
What have you used as markers, and how high are they above the bottom?
How far is the northern end of the cay from your markers?

Thanks for the info.
Boombas will now be a much less hazardous place to sail.

OK Anita I'm finaly back again with my track pics.
Here's the pickets and Cay




and here's the Cay








Not quite out of the water, but we were walking in water only toe deep in places.

We were there just after midday looking at the storm surge data it was 0nly 0.35m in Mandurah on a falling tide, so with the delay Boombas may have been 0.4 to 0.45.

The picket marker is on the tallest picket I'm not sure how far off the bottom Gavin secured but it should be visible on a very high tide. The plastic pipes around the cay are driven into the mud/sand bottom as far as we could, they started out around 1.8m and probably went into the bottom .3m so they too should be well visible on high tides.

Distance to the northern end is anybody's guess, I suppose it depends where you define the end.





but from google earth it looks to be around 700m

Those markers should make estimating the position of the cay a lot easier.
Where I crossed the cay was further to the south of your marks and also Limestone, you could feel the rock under foot.
Never the less, having the markers will make it a lot easier to guess where the rest of it is.

Anita to me it looks more like you went very close to our easterly marker. If you send me your file I'll superimpose it on the markers, and we can see for sure.

Here's Windxtasy's tracks and the new markers, looks like she just missed the bad stuff.