How vertical is your depth transducer?

[Jabs]

I need to fit a depth transducer on a high rise hull.

How important is it that the sensor is vertical at rest?

I understand the arguments abut being heeled on one tack vs the other tack but what is the real acceptance angle for a depth transducer?

I am fitting a Raymarine ST60+ and have the Airmar P79 type but am concerned about getting the angles correct!

Thanks.

Tony.

 

[David2452]

Depends just how far off you are, the cone takes an average anyway and in shallow water where a simple depth finder is more important the differential is less pronounced. However, a fishfinder at depth has a much more critical angle as it's then more about relationship to the boat's position. All that said the transducer should be as close to vertical as possible and it's usually possible to acheave via some method or other, depends on how much work you want. The 79 will cope perfectly with up to about 25 degrees without modification of the mount.

 

[Avocet]

I've a vague feeling a lot of traditional transducers have a 45 degree cone, so 22.5 degrees either side. Of course, if you heel more than that, it won't give a true reading. If it's already inclined to start with, you'll get false readings earlier on the "bad" tack.

 

[Cardo]

If people don't mind, I'd like to steal this thread as it's a very similar question to mine...
I'd like to stick an Airmar DST800 on my boat to replace the current log only jobby. The current thru-hull is probably on the least angled bit of the boat, to one side and to the front of the keel. The angle is probably around 10º to 15º. Would this be acceptable?

 

[VicS]

Mine is dead upright, but its on the centre line of the boat!

Instructions for the old Seafarer 3 are to mount is as close to upright as possible.

They say the angle of sound radiation is 45 degrees giving a reading from a single transducer up to 22.5 degrees of heel but that care is required to avoid reflection off the keel(s)

If two transducers are fitted ( one each side of the keel) it is suggested that they should be angled outwards at 15 degrees and be connected by an automatic change-over switch to give a reading up to 47.5 degrees of heel.

SEE HERE

 

[westhinder]

If two transducers are fitted ( one each side of the keel) it is suggested that they should be angled outwards at 15 degrees and be connected by an automatic change-over switch to give a reading up to 47.5 degrees of heel.

SEE HERE

My previous boat had a twin transducer system and I was very pleased with it. Only on very rare occasions with the boat upright but the mercury switch apparently not yet settled would it not give a secure reading and start blinking. With the boat heeled it worked flawlessly.

 

[David2452]

The DST800 could present an issue with deadrise as it has no real provision for adjustment unless you provide a block but that would be easily overcome by using the B744 with it's fairing block trimmed, more expensive agreed but I have fitted them in 25 degree deadrise hulls and kept them vertical. As for cone angles, let's assume 200 khz which is what most people run at unless in really deep water, (not 45 but 12 degrees BTW, 45 degrees is 50 khz) then the diameter of seabed covered is around 5 times the depth, the signals are then averaged as I said earlier to give a single number. Also be careful not to mask the cone by fitting too close to the keel if on a yacht.

 

[VicS]

45 degrees is 50 khz

I think you will find that the old Seafarer one is 150kHz

 

[Markpollock]

The DST800 would be easily overcome by using the B744 with it's fairing block trimmed, more expensive agreed.
flight training
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http://www.waterkant.net/suriname/forum/viewtopic.php?pid=256842#p256842

 

[David2452]

I think you will find that the old Seafarer one is 150kHz

Indeed, but the OP & the supplementary question concern relatively modern transducers, both of which transmit at 600w 200/50 selectable or combined depending on the processing option of the head.

 

[Poignard]

My NASA transducer is mounted in a plastic oil-filled tube inside the hull which enables it to be vertical.

But the manufacturers should be able to give advice about mounting angles.

 

[gjgm]

If people don't mind, I'd like to steal this thread as it's a very similar question to mine...
I'd like to stick an Airmar DST800 on my boat to replace the current log only jobby. The current thru-hull is probably on the least angled bit of the boat, to one side and to the front of the keel. The angle is probably around 10º to 15º. Would this be acceptable?

Yes, fine. Just check the arrow on the cap.. I think it actually needs to backwards, not forwards.

 

[David2452]

I’ve often wondered why a transducer for yachts isn’t available for in hull fitting in an enclosed bath and able to swing in it so as to compensate for them falling over a bit when the wind blows. I may experiment. It wouldn’t be beyond the wit of the manufacturers to have clinometers in the head to compensate using the processor either.

 

[David2452]

My NASA transducer is mounted in a plastic oil-filled tube inside the hull which enables it to be vertical.

But the manufacturers should be able to give advice about mounting angles.

The OP's proposed P79 transducer uses that arrangement (abait a bit more sophistocated)

 

[David2452]

Yes, fine. Just check the arrow on the cap.. I think it actually needs to backwards, not forwards.

If you want to know the speed in reverse, I guess that would be an option.

 

[geoid96]

Yes, fine. Just check the arrow on the cap.. I think it actually needs to backwards, not forwards.

I'm not familiar with the P79 refered to by the OP. However I'm not sure that the statement about the DST800 above is correct. On mine the arrow points to the bow. The important thing is that the flats on the paddlewheel face forward. As it's difficult to see the arrow when at arms reach in bottom of bilge I rely on the position of the cable which come out the front of the transducer.

 

[David2452]

I'm not familiar with the P79 refered to by the OP. However I'm not sure that the statement about the DST800 above is correct. On mine the arrow points to the bow. The important thing is that the flats on the paddlewheel face forward. As it's difficult to see the arrow when at arms reach in bottom of bilge I rely on the position of the cable which come out the front of the transducer.

You are quite correct re the Depth Speed Temperature 800, the P79 is depth only and has no specific orientation other than the case needs to be fixed to compensate for deadrise.

 

[gjgm]

If you want to know the speed in reverse, I guess that would be an option.

Actually, yes you are right.. on the dst 800 it does face forward, sorry.
On other models it faces sideways for example, to align the angle of the sensor I guess.

 

[gjgm]

You are quite correct re the Depth Speed Temperature 800, the P79 is depth only and has no specific orientation other than the case needs to be fixed to compensate for deadrise.

Presumably though the ceramic sensor is fixed in the casing, not floating...? But if it is fixed at an angle, how come it isnt specified which side of the hull it needs to be fixed? I see installation says which way to "face" the transducer, but surely it would "double" the angle if it isnt facing the right way, and is on the "wrong" side ?

 

[David2452]

The element simply produces a cone (sidescan & structure scan apart, but yachts dont need to worry about that) so it's "clock" position for want of a better description is an irrelevance really, the important thing is that it points down, most manufacturers have it that 5 degrees off vertical is acceptable but a wee bit more makes little difference. With a yacht it is difficult due to the varying heel angle so an over reading is almost inevitable with a standard install, I guess you could set the offset so that under normal cruising heel it would be more accurate but what is normal cruising heel, or indeed is there a normal cruising heel at all. For a fin keel sailing boat, dead centre and a bit foreward of the keel is what I aim for to get best results but even then it's not perfect and it's also usually quite thick so an in hull transducer is not the best option. Motorboats are so much easier, but even then you need to find some place with undisturbed water on the hull for best results at speed.