Reply
 
Thread Tools Search this Thread
 
Old 03 September 2012, 18:13   #1
Member
 
Bucksribster's Avatar
 
Country: UK - England
Town: Thame
Make: Ribcraft 585
Length: 5m +
Engine: Suzuki 140
Join Date: Mar 2012
Posts: 217
Depth / Speed problems

I'm quite new to RIBs, so I'm not sure if this is normal. I have a Raytheon ST40 speed and depth unit fitted to my Avon Adventure 560. It had the sensors mounted on a bracket off the transom, just about level with the bottom of the boat. Hopefully the photo will upload

My problem is that both speed and depth work OK off the plane (although the speed is a little erratic), but as soon as the boat is on the plane, there is no speed or depth indication.

Any thoughts?
Attached Thumbnails
Click image for larger version

Name:	image-3405295394.jpg
Views:	158
Size:	65.1 KB
ID:	71847  
__________________

__________________
Bucksribster is offline   Reply With Quote
Old 03 September 2012, 20:44   #2
Member
 
Country: USA
Town: Oakland CA
Length: 3m +
Join Date: Feb 2005
Posts: 6,653
Can't really tell from the pic, but looks mounted way low to me.

Transducer centerline (the horizontal plane of the lower bulb part) should be about even with the hull; the paddlewheel fins (if it is a paddlewheel) should extend just under.

I suspect you're getting a vortex back over the top of the paddlewheel that's stopping it at speed. If it's a pitot type, then no idea.

Any chance you can post a more detailed pic(s)?

jky
__________________

__________________
jyasaki is offline   Reply With Quote
Old 04 September 2012, 01:35   #3
Member
 
Country: UK - England
Town: surrey
Length: 7m +
Join Date: Apr 2012
Posts: 322
i agree, too low. get a ruler or a block of wood and place that along the bottom of the boat so that it overhangs the back of the boat next to the transducer to act as a guide to the boat bottom. Adjust the transducer upwards so that the bottom of the transducer is only slightly lower than the bottom of the boat. On mine i put the front edge level and the back edge slightly lower (about) 2-5mm) you might have to use wedges (which are normally supplied with the transducer by raymarine) to get the right angle. (other point is if it's too low it's asking to get hit by debris in the water as well as the vortex problem mentioned by jyasaki). The back edge of the transducer needs to be slightly lower than the front to give the paddle wheel a clean flow of water although for depth finding it needs to be pointing straight down otherwise the return signal can get confused/erratic. I've got the raymarine instructions if you need them but they are available on raymarine website) Make sure the paddlewheel is spinning freely as well (not gunked up) They do say on the instructions to avoid mounting next to chines. I can't see on the picture but if your bottom is like my avon, it looks like yours might be mounted directly behind one?
__________________
wellhouse is offline   Reply With Quote
Old 04 September 2012, 15:14   #4
Member
 
Bucksribster's Avatar
 
Country: UK - England
Town: Thame
Make: Ribcraft 585
Length: 5m +
Engine: Suzuki 140
Join Date: Mar 2012
Posts: 217
Thanks for the advice.

I attach a couple if other photos. You guys are right- if I run a ruler out from the hull, the unit is below the level of the hull, even at the left side ( i.e. where the hull is at the lowest point).

It is a paddle wheel type, and the wheel is running freely.

So I assume the unit has to be horizontal for the depth sounder. If so, where should the unit be level with the hull? Left edge, centre or right edge? The unit seems to be held in place by three screws in slots, so the unit can be adjusted. Just not sure if it can be adjusted enough!

Thanks again for the help!
Attached Thumbnails
Click image for larger version

Name:	image-2127138793.jpg
Views:	117
Size:	55.1 KB
ID:	71866   Click image for larger version

Name:	image-391628393.jpg
Views:	112
Size:	35.9 KB
ID:	71867   Click image for larger version

Name:	image-103408264.jpg
Views:	112
Size:	48.6 KB
ID:	71868  
__________________
Bucksribster is offline   Reply With Quote
Old 04 September 2012, 15:54   #5
Member
 
Country: UK - England
Town: surrey
Length: 7m +
Join Date: Apr 2012
Posts: 322
try adjusting it up as far as the adjustment allows (looks like you have about 10mm to play with on the slot) if that doesn't work you may have to screw higher up but try that to start with.
__________________
wellhouse is offline   Reply With Quote
Old 04 September 2012, 17:33   #6
Member
 
Country: UK - England
Town: Poole
Boat name: Exodus
Make: Tohatsu
Length: 7m +
Engine: Evinrude 150
Join Date: May 2007
Posts: 275
Not sure which transducer you've got but try looking on the Airmar technology website for detailed instructions on location

This is the link for the P66 which is typical of the units Raymarine supply

P66 Transom Mount - Airmar Marine Transducers
__________________
Only two things are infinite, the universe and human stupidity, and I'm not sure about the former --- Albert Einstein
Into The Blue is offline   Reply With Quote
Old 05 September 2012, 18:12   #7
Member
 
Bucksribster's Avatar
 
Country: UK - England
Town: Thame
Make: Ribcraft 585
Length: 5m +
Engine: Suzuki 140
Join Date: Mar 2012
Posts: 217
Thanks for this guys. I undid the mounting screws today, and found a wedge behind the unit which was mounted with the thick side down. This might have been put in to compensate for the slope on the transom, but bearing in mind your comments, and the most useful web link instructions, I have taken the wedge out, and moved the unit up about as far as it will go. This looks to be about right according to the mounting instructions. Pointing slightly down, and the left edge level with the bottom of the boat.

So assuming this sunshine holds, I shall tow it down to Camber dock on Sunday and give it a try. I'll let you know how I get on.

Thanks again for the advice!
__________________
Bucksribster is offline   Reply With Quote
Old 06 September 2012, 01:34   #8
Member
 
Country: UK - England
Town: surrey
Length: 7m +
Join Date: Apr 2012
Posts: 322
glad it was of help, hope it sorts it for you.
__________________
wellhouse is offline   Reply With Quote
Old 10 September 2012, 18:11   #9
Member
 
Bucksribster's Avatar
 
Country: UK - England
Town: Thame
Make: Ribcraft 585
Length: 5m +
Engine: Suzuki 140
Join Date: Mar 2012
Posts: 217
Just a quick update. Had the boat out in the Solent on Sunday, and it works! Got speed all the time, and depth most if the time. So I now know I had the boat up to 40 knots before I lost my nerve. The scary bit that caused me to back off the throttle was the expression on my wife's face lol. Can't wait for a flat water day to go flat out :-)

Thanks again for the tips.
__________________
Bucksribster is offline   Reply With Quote
Old 11 September 2012, 01:46   #10
Member
 
Country: UK - England
Town: surrey
Length: 7m +
Join Date: Apr 2012
Posts: 322
did you launch/recover at saxon wharf on saturday?
__________________

__________________
wellhouse is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 13:47.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.