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Father
30-03-2016, 05:03 AM
My son bought me a copy of 'Complete Wreck Diving: A Guide to Diving Wrecks'. In talking about ways to search for wrecks it talks about dive sleds.

I'm a member of the Kwajalein MIA Project. In the past we have used a borrowed side-scan sonar system. However we don't have access to it all the time. We're exploring financial options to purchase our own, but in the meantime, after reading about dive sleds, I thought that might be a viable option to consider.

I'm not so much looking for a design as much as information, although I'm open to ideas. I'm more interested in any tips, recommendations, stories, experiences, etc. that would help determine if this would be a good option for searches.

How difficult are these to maneuver side to side?

My concern is getting pulled into a coral mound. Obviously going up and over it, depending on the size, could cause some serious problems. So going around it would be ideal.

How do you signal the boat when you let go? I've read some people saying the driver will immediately notice the difference. Depending how it's made I thought one way to signal the driver would be to have a line zip-tied the length of the tow rope that connects to a light or buzzer. Have the line attached to a switch of some sort (maybe like the kill switch on a jet-ski). When you let go, it trips the switch and the boat knows to stop. Depending how far it got before stopping you could re-mount the sled and re-attach the switch signaling the driver to resume.

Anyone have any success stories using one to find wrecks?

Tens
31-03-2016, 08:56 PM
First thought is: why not just tow an smb behind you. When you let go of the sled, the driver will see the smb disappearing into the distance.

I wouldn't have thought a sled would have any side to side manoeuvrability. Not unless it has an aerofoil section and banking it will create lift to the side. Sounds like it might be a bit of a difficult thing to control.

I was told a story a few years ago of divers making a bit of money by looking for lost concrete moorings in zero visibility being towed behind a rib. They used thin string and when their head hit the concrete block, the string would break. They then sent an smb up and marked the mooring. This particular bloke had scars on his forehead to prove it. But it might have been him winding me up.....

Steve C
01-04-2016, 02:44 AM
Hi, firstly I am just on my way back from Palau where I met members of the Bent Propeller Club so much cudos for you for what you are doing in Kwajalein.

Some years ago a group of us made what we called a “Manta Board” using some heavy duty marine ply.

A quick look on google came up with this link.

https://en.wikipedia.org/wiki/Towboard

This is a rather more feature rich version of what we made:

http://2.bp.blogspot.com/_m5SP3FgQSPY/S9DgSAQJHHI/AAAAAAAAARA/Peoz2-s-P98/s1600/Towboarder.jpg

We use the board with two divers but one is probably easier. The key design issue is to have the bridle coming from just forward of the lateral centre line of the board. This allows you to easily control depth by flexing the board with your forearms.

You need plenty of line at least 5 times the operating depth you are planning to go to. We used floating polyprop line.

You also need a quick disconnect…we had a steel ring on the tow line connected to the board using an on-load release similar to these:
http://www.downwindmarine.com/images/P/216403.jpg

or
https://www.s3i.co.uk/image/s3i/Snap%20Shackle%20Swivel%20Shackle%20Main.jpg

In use it is possible to “fly” the board up and down and also from side to side. The controls are a combination of the angle of the board on your forearms and your body / fins. You can get the thing moving quite well after a little practise. The trick is not to get greedy on speed… the boat isn’t going to be going too fast but you can cover a lot of distance. You need reasonable visibility to let you fly over / around any obstacles. Go too fast and you get mask issues and freeflowing regs depending on your reg design. It is also knackering! don't be tempted to connect yourself to the board or tow line directly!

The boat will definitely know when you have released …and we just let go of the board after coming to a stop. I guess you could send up a DSMB for them to drop the board back down to you if you want to carry on again.

If you want more info then feel free to drop me a PM.

Cheers Steve

DaveBarber
01-04-2016, 08:03 AM
Equalising is quite a challenge. You need both hands for hanging on!

Mikael
01-04-2016, 08:18 AM
Equalising is quite a challenge. You need both hands for hanging on!

Surely you could just have a loop at the rear of the board at the end its centre line. If you held on with one hand here the board should stay stable and the other is free to equalise. As long as the boat is rocketing along and you have the gripping arm fully extended rather than trying any pull up nonsense you should have sufficient strength to hold on.

Or at least that is my speculation.

DaveBarber
01-04-2016, 04:58 PM
When I did this we rigged an old window board on a yoke and used 2 massive bolts for handles.
Equalising you trapped one of the bolts in the crook of your elbow.
To go deeper you held the bolts high up to increase the leaverage and vice versa.
Ascent rates were very high

Father
01-04-2016, 09:49 PM
Unless I'm missing what's being said I usually just equalize by short/quick exhales out of my nose on a fast descent.
I do it every time I use a DPV.