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Old 12 January 2022, 17:35   #1
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SIB mounted transducer question

Another transducer mounting question, sorry!

So I am setting up my Elling for next season and I need to mount the (very large) 3 in 1 sidescan transducer for my HDS unit. I've realised that on this "cat like" hull, the transom really isn't low enough to use the same solution that I had on the Honwave. Not only would the transducer perhaps be too high above the water at speed, but worse is that the tubes and the central "sausage" keel would likely block much of the sidescan (being able to view and record high quality sidescan is very important to me). I also had some issues with the engine blocking sidescan to port on the Honwave, because of the distance that the transducer protrudes from the transom.

It seems like the guy in this video had similar issues on his Elling, and came up with quite a neat solution (see 10 mins on in the vid, or pics below). Transducer is mounted centrally and reversed (front/back), so that it sits directly underneath the sausage. It has a totally unobstructed view, and hopefully gets clean water when under way. The sleeve arrangement glued to the underside probably makes this rather secure also:





I want to do the same, but I've got a couple of issues. 1/ the transom plate is much deeper on my version of the Elling, so I can't fit one of the borika mounts between bung and transom plate and 2/ I don't think I quite have the clearance engine/transom to allow it in any case (I need to check this).

My proposed solution is to mount HDPE blocks, one each side of the bung hole. Then make a sort of T section, probably out of 4-5mm alu bar, which attaches to the blocks and also the transducer. Transducer then slots into a simple sleeve of PVC that I glue to the sausage. This should be a very low profile mount.

My transom:


A very rough idea of the mount:


A simple, open fronted sleeve that is glued in such a way to be snug to the transducer but still allow removal:


My transducer:


Questions!

How best to attach the aluminium T bracket + transducer to the transom blocks. This has to be tooless and removable. One idea I have is to get some threaded brass inserts for the HDPE, and some stainless thumb bolts. Should work? I worry it won't be secure enough and may work loose through vibration, but is there a better way? It needs to be fairly low profile, also.

I am hoping I can arrange things so that the transducer is snug to the underside of the keel, and within the sleeve. If this works out, I think it should be fairly secure and not kick up a lot of extra spray etc. Any thoughts? If water can get in at the top, I imagine that may apply a fair bit of pressure when underway which might pop the transducer out. Perhaps it is worth trying to craft some sort of fairing at the front? Followup question, how will the sleeve behave with no transducer mounted?

Open to any bright ideas!
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Old 12 January 2022, 17:59   #2
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Have you considered ratchet strapping the bare transducer to the back of one tube and testing if that gives clearance from the outboard for sidescan? There are btw other shapes of transom engine mounting plates that would give you more room if you were using a mount between it and the drain bung but I dont see that you could easily gain the space needed if the outboard was in pin hole 1, too close to the leg I would think.
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Old 12 January 2022, 18:04   #3
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Thanks for the response. Yes, I have considered it and it would probably work, but I think it would work better centrally in terms of image and sonar usability (I'd have a metre offset to one side if tube mounted). Also I'm not convinced it would be much/any easier to achieve? Certainly I couldn't use the existing bracket, so would I just go over the transducer or fashion something with a slot that sits above? The other thing that worried me was trailing the wire up. All in all I think central on the keel would win on a few fronts, if I could achieve it neatly (and no issues with wires, or transducer rooster tails etc because it would all be neatly placed behind the sausage).
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Old 12 January 2022, 18:07   #4
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Quote:
Originally Posted by Oldman2 View Post
Have you considered ratchet strapping the bare transducer to the back of one tube and testing if that gives clearance from the outboard for sidescan? There are btw other shapes of transom engine mounting plates that would give you more room if you were using a mount between it and the drain bung but I dont see that you could easily gain the space needed if the outboard was in pin hole 1, too close to the leg I would think.
Similar to the thought I had except split the bracket and strap or monster cable tie it to the underside of a tube, not to the rear of it. Wow it's a monster! You win on top trumps.
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Old 12 January 2022, 18:12   #5
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Originally Posted by Limecc View Post
Similar to the thought I had except split the bracket and strap or monster cable tie it to the underside of a tube, not to the rear of it. Wow it's a monster!
It's horrendous, but a lot of them are now! Humminbird do a much smaller sidescan transducer than the rest, but I did hear a rumour that they have a patent on whatever tech it is that allows them to do it, which is why they are the only ones. Their sidescan is probably the best in the business as well.

Could remove the ducer from the bracket which leaves a smooth plastic top, then ratchet over it. It might work OK but there would be a fairly fat trailing wire which would need a bit of management.

Central is still the ideal - lots of hard boat users now glueing their ss transducers to the keel in a similar manner. A bit less up and down movement with boat rock in that position, which helps the image - although probably not a huge issue at the sort of speeds you use sidescan.
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Old Today, 05:13   #6
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OK, reviving this one with a few more pics now I have got the boat out and taken a look. I had forgotten/never realised that the "sausage" on the Elling is actually "free floating" towards the transom, which opens up the possibility of strapping the transducer on, in a similar way to strapping to the main tubes. Main tubes are confirmed as not a great option for my boat, given strakes immediately fore, and also probably issues with getting it perfectly level etc.

Current plan is to go with the original idea:

Enlarge the openings in the side of the bracket on both sides, so that they can take (velcro?) straps. Stick a length of 10mm closed cell foam inside the bracket also, to fill the void between transducer/keel and protect the underside of the boat.



Go with the original idea of fitting a pair of hdpe blocks to the transom either side of the bung with brass threaded inserts (M6) in each. Attach a cross member of hdpe using M6 star knobs, far enough off centre to be out of the way of the engine (they'll poke out a bit):



And that's it. should be quite easy, and I'm hopeful it will work well. The question now is which sort of straps? There are some velcro elasticated ones around on the usual sites which look promising.

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Old Today, 05:52   #7
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Not wishing to pe* on your parade but the sausage on my Elling is awful close to the outboard even on pin hole 2 on the saddle. Are you sure you will have the clearance to your outboard after mounting the transducer there?

yam on elling sausage clearance.jpg
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Old Today, 05:54   #8
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I remember your post on that one Oldman. Mine isn't - it is at least two inches further back than yours - so I *think* I'll get away with it, although I haven't put the motor on the boat along with my mockup to actually test it yet (have done a bit of measuring though). I'll probably end up using a 3mm stainless plate from cross member to transducer, which should keep the profile down a bit, so fingers crossed it will be OK. You're right tho, I don't think this would work with your sausage..

Edit: 2 inches may be an exaggeration, but you can see from the top pic in my last post that the sausage almost reached the edge of the black lip at bottom of transom.
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