Installing a depth sounder in a Tomahawk 25

[mdonnelly]

Wondering where best to site the transducer. Doesn't seem to be a place forward of the keel to bond to the hull. Anybody any advice?
Thanks

 

[VicS]

Wondering where best to site the transducer. Doesn't seem to be a place forward of the keel to bond to the hull. Anybody any advice?
Thanks

Read the instructions for guidance on suitable locations and places to avoid where turbulence might affect the reading.


Test possible locations by sticking it down temporarily with chewing gum, or perhaps holding it in candidate positions with a dollop of water based personal lubricant* to couple it with the hull.

*Or the stuff they use with ultrasound scanners

 

[Seajet]

If forward of the keels - a good idea as it's out of the turbulence they create - the hull is almost certainly too veed to just stick the transducer to the hull, so you would probably require the traditional method for in - hull mounting using a tube with a scarfed end to fit vertically from the hull inside, filled with something like castor oil and with a firm lid.

If you fit the transducer aft of the keels where the hull is much flatter you get 0.0001 secs less warning of running aground, but as long as the transducer is not directly behind a keel, skin fitting or log impeller it should be OK and you can simply stick it straight to the hull inside with silicone sealant which ain't half less hassle !

 

[earlybird]

I had a twin keeled Tomahawk in the early 90's To the best of my recall, the oil-bath transducer was under the floorboard of the heads compartment. This would put it just forward, and about in line with the st'bd keel. As said, the hull is fairly vee'd, the transducer was mounted vertically, but worked OK for the several years I owned the boat.
I also fitted a log paddle-wheel, can't for the life of me remember where though!

 

[mdonnelly]

Thanks for replies. This is a fin keel. The only suitable area to bond directly to the hull is aft of the keel where it's flat. Will water turbulence make a significant problem?

 

[Seajet]

It would be OK if slightly to one side of the keel, best not directly behind.

It doesn't have to be completely horizontal, I believe the sounder beam describes a 45 degree cone - though everyone has a diffent figure !

I have 1 sounder direct to the very slightly veed aft hull and one in a scarfed tube & oil bath forward of the keel and just offset to avoid the thick grp central ridge - as it was the same price I prefer 2 seperate systems rather than a repeater - both work fine.

 

[mdonnelly]

It would be OK if slightly to one side of the keel, best not directly behind.

It doesn't have to be completely horizontal, I believe the sounder beam describes a 45 degree cone - though everyone has a diffent figure !

I have 1 sounder direct to the very slightly veed aft hull and one in a scarfed tube & oil bath forward of the keel and just offset to avoid the thick grp central ridge - as it was the same price I prefer 2 seperate systems rather than a repeater - both work fine.

Thanks, that's very useful.

 

[Len Ingalls]

View attachment 49788

30yrs+ marine electronics-this is my boat with thru hull bronze t-ducer mounted about 1/2 way back on hull & out from keel where bottom is most flat.
You could mount an inside t-ducer in same area,with poorer performance(being inside) if your hull is NOT cored.I do some fishing,hence the thru hull,but if you just want depth,inside is OK.
You do not want anything ahead of t-ducer closer than 3ft,or you will experience broken picture from air bubble/turbulence.
Google transducer mounting-lots of info on web. Cheers/Len

 

[<152587>]

Sold a Tomahawk few years ago, transducer was fitted in front of keel thru hull.

 

[oldsaltoz]

You can test what sort of a signal is available by sticking the thing into a plastic bag and sliding it around inside the hull tii you find the sweet spot.

Air is your enemy, eliminate that and you fine.

Good luck and fair winds.

 

[mdonnelly]

You can test what sort of a signal is available by sticking the thing into a plastic bag and sliding it around inside the hull tii you find the sweet spot.

Air is your enemy, eliminate that and you fine.

Good luck and fair winds.

Thanks for advice. Boat belongs to my old mate Bill. He's approaching 78 and we're planning a weeks sailing in July. Normally he comes with me but this year he's hoping to take his Tomahawk so getting her ready for a trip around the Clyde. We really are looking for the easiest option so offset behind the keel will be our first option.