Topic: hello evry towfish men

[abraquelebout]

if whe want to make a standart of our method, ?
i begin:
for my towfish, 60 m of cable (196 feet), 1197 si
the probe past   at 3 or 4 meter deph , speed no more than 2 knts for a best definition, and 25 meter range, 455 khz
i use hbsi sonar converter, son 2 xtf, yellow fin, deepview, si view and humviwer
for more deph to the probe i use an hydrolic winch with lest.
i joint 2 picture of a nother unknow wreek at 20 m deph. make  the 30 07 2010
who talk of is method?

[Rickard]

Hi!

You seem to have been very successful with your system! I'm not sure what you mean by "making a standard of our method", but if you suggest we should collect our experiences from our towfish projects I think that's a good idea. There are postings on towfish projects on several places in this forum and in other forums, and, which is a typical problem with forums, it's sometimes difficult to get an overview of a subject with the search tool.

I have presented my system in other posts in this section of the forum, so I just repeat the most essential data: 50 m with ethernet cable and a steel wire. Towfish weights 10 kg. The effective range is about 30 m at 455 kHz. Performance is comparable to yours, it seems.

There are some interesting details in your images (apart from the wreck itself, of course). You have no trouble with interference, congratulations. The primary return from the surface is visible, as well as the secondary return from the seafloor (that return has hit the bottom, bounced and hit the surface and finally reached the transducer). You rarely see the secondary bottom returns. The extra returns can be informative, and can be eliminated easily with a cork roof on the transducer if you don't want to see them.

I wish more people would present their towfish images, you should be honored for doing it!

Rickard

[abraquelebout]

hi rickard
thanks for the information for the cork on the roof , i want do it as fast is possible
yes, it's interesting to compare the diferent method for pepole who want to make her own towfish and adjust  our own method whit other idea.
whe have some problem with the ship, it goes faster (3,4 knts) by puting into gear, if whe want to go at 2 knt whe must play whit gear(its an old 1960 baudouin 50  cv motor started whit compressed air), that's explain wave on picture. the probe is not stable in deph.
i espere other picture and method of other towfish men on this forum.
whe are working in ED 50 gps reference, when whe convert the film,the result in deepview are in WGS 84, i think the unit work in WGS and register in this format...

[Rickard]

Right,

too high speed although you are idling is an issue with most boats, also with mine. I have a small vessel (8 m, 2 tons) with a 12 hp petrol engine and have to use extreme carburettor and ignition settings to bring down speed to "towfish level" (< 3 Knots). This is not healthy for the machinery in the long run. I also use a foldable Porta-bote (easy to transport on a roof rack anywhere) with a 4 hp 2-stroke engine (the boat planes!) and a MinnKota 40 Maxxum in calm waters. The electric MinnKota is very suitable for low speed towfish scanning, but the light Porta-bote is difficult (but not dangerous) to use at sea and large lakes, mostly because of the winds. The typical towing speed with the Porta-bote and the MinnKota is 1.5-2.0 Knots.

Map datum (the coordinate system used in a GPS) must, of course, be the same as the system used in GoogleEarth (WGS84). I did some scanning one day with wrong system setting in my external GPS (Garmin, I have a 981 and have to feed the sonar with positions from an external source) and the track was shown far up in the wood in GoogleEarth!! Such mistakes are hard to detect when you scan far from the shore...

Rickard

[abraquelebout]

yes , i just want to make an adjustment.
fore locate some wreek , when fishermen give us the point, it's in ED 50 (for old fishermen, young have her GPS in WGS 84)
then whe put de 1197 si in ED50, but the record film is in WGS 84 on deepviewer or humviewer or other system.
whe find it when whe go to dive on the first anomalie
the record film dont take care to the referencement of the gps.

[Rickard]

Hi,

The 981 and the towfish system generated this nice image from a "violin" paddle steamer named Östergöthland. The steamer was launched is 1829 and sank in the gulf of Slätbaken in Sweden in 1862. Depth is about 14 meters. I used the light Portabote in really bad conditions, rain and strong wind, but could still get good results.

Rickard

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[abraquelebout]

hi rickard
nice picture
i thinq the wreck in your country are in better condition than mine
the picture i join on these post are a ship who sunk probably in 1875 ?
whe don't know his name, whe find it there 3 years whith magnetometer
the sonar help us and whe find other part of this wreck at 35 meter of the ship.
im working in sub marine archeology in my hobby
now i modify my towfish.
more lest and 4 mm dyneema rope for traction.
i send you a nother post to talk about this

[Kimi]

Thanks a lot guys for "new" and very useful in formations. Nice pics!
(learn as long as live) 

i think the wreck in your country are in better condition than mine

Wrecks in the Baltic sea (great lakes etc) are in better conditions than elsewhere.
Because of no shipworms, low current, darkwater-low UV light, low oxygen, and cold water. There are ships in the Baltic sea that sunk over 200 years ago and are still in good shape!

http://www.nba.fi/tiedostot/a8e45ede.pdf


Kimi..