Transducer angle?

[DownWest]

Hi
Just fitting the transducer and no paperwork. The hull is horazontal across at this point, but angled up forward by about 12°.
So, is this within the allowance, or do I need to wedge it a bit?
Hull is ply and I will put a fairing on the projecting unit.
Thanks
DW

 

[Fr J Hackett]

There is little work involved so you might as well do it and bed it in epoxy not sikaflex.

 

[johnalison]

I take it you mean echosounder. If so, you may reduce its range by ? Cos 12 degrees, which is not much to worry about. If it is for speed, then the instrument’s calibration can be used to compensate.

 

[ChromeDome]

What transducer and what instrument at the other end?

 

[srm]

I take it you mean echosounder. If so, you may reduce its range by ? Cos 12 degrees, which is not much to worry about. If it is for speed, then the instrument’s calibration can be used to compensate.

Unlikely, the outgoing sound pulse spreads as a conical beam from a circular transducer face. The actual angle of spread is a function of the size of the transducer face and the wavelength. Basically, the larger the transducer face for a given wavelength the narrower the beam width. The instrument normally displays depth from the first return, which will be the vertical sounding in open water.

When mounting portable survey transducers we always gave them a few degrees rise at the front to prevent air bubbles and cavitation getting trapped against the face and absorbing the sound pulses. 12 degrees is a bit more than we would use, but for leisure navigation I would not be too concerned as the beam width is typically 20+ degrees.

When fitting an echosounder transducer a smooth fairing to give a clean water flow over the face and tilting the face slightly forward will reduce the risk of loosing the bottom due to cavitation or air bubbles absorbing the return signal.

 

[KompetentKrew]

Hi
Just fitting the transducer and no paperwork. The hull is horazontal across at this point, but angled up forward by about 12°.
So, is this within the allowance, or do I need to wedge it a bit?
Hull is ply and I will put a fairing on the projecting unit.
Thanks
DW

It may help you search if you know that this angle is referred to as the deadrise. A transducer is angled at the deadrise angle or with "a deadrise of x°" and in one email to me Garmin referred to the acceptable range of deadrise as the deadrise preference. Not trying to be clever, a month or so ago I didn't know this either.

If I'm understanding you correctly, it's the forward deadrise angle you're asking about. I think that distinction may be made, although I'm not sure if sideways deadrise is often a consideration.

For example, the Garmin GDT 43 has a deadrise preference of 0° - 20°. This is mentioned on the product page, but isn't obvious if you don't know what to look for, My guess is that probably all transducers have a similar deadrise preference, but IDK.

 

[DownWest]

Thanks all.
srm & KK's replies made me think a bit, as it was going to be well forward. That might put it a risk of aeration on one tack. So rethink and further back, which the would be more vertical. Just that the position would have been convenient.
Yes, it is a depth transducer. I do actually have a log unit with the surface transducer, but won't bother with that. GPS is enough. (this is old kit, but fun to use..)

 

[DownWest]

What transducer and what instrument at the other end?

Don't larf, but a Seafarer led spinner. Matching transducer from another forumite.

 

[srm]

Don't larf, but a Seafarer led spinner. Matching transducer from another forumite.

Nice little sounder, with a bit of practice the display could give a good indication of the sea bed. The transducer has a wide angle. Aways start on the deepest scale as its possible to get false readings, especially when over a hard sea bed. I once tried anchoring with my first boat but finished up with the hook and chain hanging vertically from the bows as I was reading the second returns on the shallow scale! I had them on three of my own boats, and a high spec survey sounder for work.