mobile sonar unit

[Alun]

i've attached a photo of a mobile sonar unit i've built. the model is a humminbird max10 - costs around $100. it came from the US and unfortunately depth and temperature measurements are in imperial only. apart from that minor inconvenience it's great!

as you can see i built a little floating platform for it. the prototype is a little rough and i may make a better final version. basically it's just 2 pieces of wood sandwiching some polystyrene ceiling tiles... all bolted together.

i tested it today and it worked perfectly. the spot where i normally dive is about 93m according to this. it's so sensitive that it even registered the weights at the bottom of the rope, which happened to be at 60m today. i then slowed down the scrolling speed and did a quick dive. when i surfaced i could see a fine well defined line tracing a V-shaped profile (of depth versus time).

the unit needs a 12v power source. for this i bought a battery holder for 8xAA batteries. these are stored inside a watertight box (designed for electrical systems). the box was screwed down to the wood. excess cables were coiled up inside the platform to keep things neat.

i have no doubt that this will be a really handy piece of kit for improving safety. it will take a little time to learn to interpret the signals, but already i am beginning to learn. for example, today i often saw a series of lines on the display near steep gradients. (in Dorothea - a slate quarry). these signals are produced by series of slate 'terraces'.

if you've ever thought about using a fish finder in this way then i would recommend the piranha max 10.

ps: it can measure depth to 180m and the scale is variable. when diving deep we will be using the 360ft range, so i've stuck on our own scale in metres for an easy way to measure depth.

[land shark]

lol alun
dont forget at least some of old codgers like imperial measurements

jim

[portinfer]

Very cool Alun ! So if there were fish moving below you would see them on the sonar ? - (I am a little ignorant of these type of gadgets...) I guess it could be fixed to a standard diving/spearfishing float - or does it mind being immersed ? I know that some GPS dont mind a splash but dont like immersion. Also reeeeespect for 93m The spot I normally dive is about a tenth of that.

Also - got me thinking of mapping an area that you dive regularly - in your case I guess the quarry is relatively small ? It might be good to make a map... ??

[Alun]

yes, it can detect fish. it can even distinguish between different size fish, apparently!
this unit is waterproof to 1m for 30mins (that's some form of standard). i.e. it's splashproof/rainproof which is good enough. it's always clear of the water but inevitably gets wet.

i was using it today to find that deepest part which is over 100m. i think i found it. Dorothea is about 400m across at it's widest. you could probably fit 4-5 football pitches in there.
http://www.kierman.co.uk/data/galler...N8864_JPG.html

i think it could also be very useful for spearing in deep water where the visibility may not be too good. maybe it's not really in the spirit of the sport?

[Absolute]

Good job! They also make those units with a built in GPS, that would make finding that deep hole just that much easier the next time.

Beautiful diving spot! Looks a little cold for my blood though.

Are you getting to that 100m mark in CW?

[Alun]

yes a GPS would be useful. i think we'll use a separate GPS unit to map our the site. mind you given that the site itself is relatively small they may be of limited use... depends on the resolution i suppose.

100m CW... i'm afraid not! 100m in tropical waters is pretty deep, but in somewhere like Dorothea it's a whole other ball game! the water was 46F yesterday or 7-8C.

[miles]

Hiya

Great idea!!!

There are now a number of small portable echo sounders available quite cheaply. Many of them are designed for the growing sport of kayak fishing. They normally use normal AA batteries and are quite small. Most are splash proof as well. Well worth looking at too!!

http://www.sportfishingmag.com/article.jsp?ID=8679
http://www.dealtime.com/xPC-Humminbi...st_Fish_Finder

Regards
miles

[Absolute]

That is unbelieveable! 4freakin6 degF!

Here the water temp is 84 - 82F.

Probably all the way to the 100m mark!

I'll let you know when I get there. lol

[Alun]

it's still going down too... it won't stop until it reaches 39-40F!

84F sounds nice... 28C.

are you really located near the Marianas trench? somewhere in the Philippines? what's the diving like there? good viz? lots of marine life?

[Absolute]

I am sitting just on the edge of the Marianas Trench. I think the deepest part of the trench is about 50miles south east of here. Here is a link to a sketch http://www.cnmi-guide.com/info/sketc...nastrench.html

Primarily most of the diving is done in the Philippine Sea. West side of Guam, the east side is the pacific ocean side, windy and rough most of the time. The visibility is from 30 to 50m and just a few hundred yards outside the harbor is deep deep water. Like thousands of feet. Most of the diving is done by boat rather than swim out. There are lots of dive companies with boats around for reasonable prices (40$ for bottle nauts) here but during the summer the water will be so calm that you could kayak out to the drop off too. There are certian times of the year when pilot whales can be seen but of course there are the resident dolphins, sharks, reef fishies and yellowfin,mahimahi,whaoo. etc

The place to dive is behind orote cliffs. The current can be strong depending on the moon but plenty of room to drift around. This place is on the leeward side so the strong tradewinds do not give you a hard time while breathing up on the surface and it is DEEP. That is where Guam's Blue Hole is http://www.mdaguam.com/bluehole.htm
This place rocks! Top of the hole is 20m and the bottom...it drops off so fast there it is hard to get to it. I did 80m on scuba a long time ago and was not even close to the bottom. So yea this is a cool place to dive and live you just have to deal with the occasional typhoon!

Sorry for the long post. I can go on an on about diving here.

Cheers!
Jay

[laminar]

Alun,

Great post and great work. This is something that should be mandatory for competitions in my humble opinion. Especially, in places where the water column is dark, like sambuca.

How long does the battery last?

Pete

[Alun]

thanks Pete.

yeah, i think it would be a good asset for competitions and records. you'd need a clear and well defined protocol for its usage though.

when i tested it i used 8 half-charged standard AA batteries i found lying around. it was on for about an hour in total with no signs of fading. so at the moment i can't really answer that question. i've bought some NiMH rechargable batteries (2000mAh) and so i'll see how long they last. i'll try to keep track of the hours. i would imagine the batteries suffer in the cold, but fortunately the battery box is insulated from the water. maybe you could even pop a chemical hand warmer in there to maintain a decent temperature. i think this particular unit has some form of battery alarm. you can set a minimum voltage below which the alarm sounds. i need to read the manual again to find out more about it.

i'll be using it again on wednesday. i will try to get a good screen shot whilst people are underwater so you can see what it's like.

[naiad]

Rechargeable batteries are different from standard batteries in that they tend to run out suddenly instead of gradually. This might make it harder to know how much battery power is left, but if you know how many hours they normally last, it would be easy to estimate.

I have to go to Dorothea sometime...

Lucia

[Aquagenic]

Better yet, how about something like this?

http://www.dealtime.com/xPC-Humminbi...st_Fish_Finder

Does anybody have any experience with stuff like this, I must confess I'm clueless.

~James

EDIT: After doing a little more research this specific unit seems to be very unreliable. A neat idea though, if they could get the bugs worked out.

[land shark]

Alun and Laminar,
Up here in the north woods when the water gets hard <Winter> We take the finders off our boats and put them in our ice shacks. I use a Gel Cell 12v they around and cost about 40 bucks US. But you have to bear in mind the voltages have to be the same.
The Gel Cell comes in a motorcyle size casing. Is recharger friendly and lasts for hours.
They are recharged with a small trickel charger, (1 amp). I even run my old flasher sonar off it for hours. ok mabey 4 or 5 hours continous.
they are sealed construction as well.

jim