Just mount it inside on a bed of marine grade sealant.

Make sure to roll it onto the bed to eliminate any air bubbles.

Most Transom mounted transducers will fire through all material except steel. mount it as nsw said and you will proably even get temp. Mates one works through ferro, mine is ok in a ply epoxy dingy but I have to hang it of a stick of the transom of my steel vessel, it's a back up so I'm ok with that but I guess there's no reason it can't be hung from the stem and have forward scan

Bananabender said..
You have probably read enough to realise in hull will NOT transmit through wood of any kind with any accuracy . Airmar categorically state big no no for wood or cored fibreglass.
Option is a flip down transom transducer or through hull.

Thanks. Yes haven't found anyone who's had success with firing through wood. Hadn't thought of a flip down - could be a solution

Wood, even laminated plywood has pores and it therefore porous.
Those pores contain air.
A depthsounder can't shoot through the bubbles of air that are in wood.
(Actually, it can shoot through but the ray is scattered , I think.)

"Transom mount not an option as it's out of the water."
If that is the case, a through hull fitting might be your only choice.
Drilling an over sized hole, epoxying the exposed edges of the ply and fitting the transducer is not as bad as it sounds.

Gary

Wouldn't recommend that at all as the inner glass skin would be gone and the structural ramifications would be uncertain.

If you want to shoot through all epoxy maybe hole saw drill out the inner glass skin and the timber leaving the outer glass skin, fill the hole with epoxy glue strength filler up the the top level of the inner skin, re-apply the inner skin with epoxy resin and laminate same thickness as was there with biaxial mat, and shoot through that? Agree must be done on the slip.

The hole would probably be about twice the diameter of the puck - they are usually around 50mm diameter - of the transducer but it depends on the timber thickness and what the puck cone angle is. The inner skin epoxy resin laminate would be (say) a 200 to 300mm square to ensure structural continuity of the skin.

Drilling the inner skin and timber and not the outer skin and then inserting the puck is not the same structurally as installing a fully through hull puck with the timber epoxy sealed and the puck having flanges etc which are sealed outer and inner.

garymalmgren said..
Wood, even laminated plywood has pores and it therefore porous.
Those pores contain air.
A depthsounder can't shoot through the bubbles of air that are in wood.
(Actually, it can shoot through but the ray is scattered , I think.)

"Transom mount not an option as it's out of the water."
If that is the case, a through hull fitting might be your only choice.
Drilling an over sized hole, epoxying the exposed edges of the ply and fitting the transducer is not as bad as it sounds.

Gary

Yes it's a bummer. Before buying the boat I never even considered that having the transom up out of the water would present any issues - live and learn. I am always nervous about putting a hole below the waterline but as you say I might not have a choice.

r13 said..
If you want to shoot through all epoxy maybe hole saw drill out the inner glass skin and the timber leaving the outer glass skin, fill the hole with epoxy glue strength filler up the the top level of the inner skin, re-apply the inner skin with epoxy resin and laminate same thickness as was there with biaxial mat, and shoot through that?

That is what I had in mind. Leave the outer skin in tact. Maybe I didn't describe it well.

Achernar said..

r13 said..
If you want to shoot through all epoxy maybe hole saw drill out the inner glass skin and the timber leaving the outer glass skin, fill the hole with epoxy glue strength filler up the the top level of the inner skin, re-apply the inner skin with epoxy resin and laminate same thickness as was there with biaxial mat, and shoot through that?

That is what I had in mind. Leave the outer skin in tact. Maybe I didn't describe it well.

I realise you wrote to leave the outer skin in tact. The outer skin being what the water sees on the outside of the hull. The rest of my post remains.........

If dreamerdownunder is still around frankly I would not muck around and either a flip down transducer off the back or put in a thru hull. Being a ts I imagine its on a trailer so not to hard to drill a hole ,follow instructions and put one on. I have had for last couple of years a basic Hawk Eye in hull and it does the job, ie. tells me depth and has an alarm ,nothing else. Cost me US69 complete.
You can get one ,with temp.for around 110 US including transport .

www.ebay.com/itm/HawkEye-In-Dash-Depth-Finder-Sounder-with-Temperature-Thru-Hull-Transducer/254589567538?hash=item3b46b88232:g:xh0AAOSwdi5eVCA1

It so happens that when I bought mine they sent a through hull airmar P19 transducer by mistake
They sent the In hull but refused to pay for freight to return the thru hull .
Its still boxed, if you want it for cost of freight Bne to Vic. pm me.

Ps. Norcross marine were very good and efficient to deal with.

Bananabender said..
If dreamerdownunder is still around frankly I would not muck around and either a flip down transducer off the back or put in a thru hull. Being a ts I imagine its on a trailer so not to hard to drill a hole ,follow instructions and put one on. I have had for last couple of years a basic Hawk Eye in hull and it does the job, ie. tells me depth and has an alarm ,nothing else. Cost me US69 complete.
You can get one ,with temp.for around 110 US including transport .

www.ebay.com/itm/HawkEye-In-Dash-Depth-Finder-Sounder-with-Temperature-Thru-Hull-Transducer/254589567538?hash=item3b46b88232:g:xh0AAOSwdi5eVCA1

It so happens that when I bought mine they sent a through hull airmar P19 transducer by mistake
They sent the In hull but refused to pay for freight to return the thru hull .
Its still boxed, if you want it for cost of freight Bne to Vic. pm me.

Ps. Norcross marine were very good and efficient to deal with.

Thanks and Wow, cheap as chips. You're tempting me :).

I've found one of the US fleabay ads for a unit with a transom mount so I could get that and if it's too painful or doesn't work if I could get Your through hull I'll have that option as well.