Adding trim tabs, positioning, transducer placement, etc.

[Thirsty Endgrain]

I was going to add a hydrofoil, the SE sport 300 to help with lifting the heavy rear of my boat and planing better, but I decided on trim tabs instead, which seem like a better all around choice with better stability.

Im trying to figure out how to locate everything. I don't have a super wide boat, and the transom sticks out from the back so I'm going to have to do some starboard engineering to fur out. If I locate the tabs where they suggest, 5" in from the outside it will force locating the transducer even closer the the LU than it is now, which is already 5" too close from the suggested distance from propeller. Ideally it should be 15" away, and right now it's 10" away from the outside edge of the prop. If I went with the above scenario it would only be about 7" from the edge of prop.

Below shows what I'm thinking, and I've stared long enough that I can't see anymore and would appreciate input. This seems like the only compromise I can find. Nauticus says that the tabs should be located a minimum of 10" away from the center of the boat. So In my little doodle I have them 12" from center. Then the xducer a couple inches to it's right. That puts the xducer almost right above the strake, which I'm also not crazy about. I may loose the ability to read bottom at speed, which I'd like to not loose. You can't see the strake in the pic, but it's right at about 27". If I move the xducer even closer to the trim tab, I'll probably also loose signal. For that part I'll probably just have to temporarily locate the xducer and play around with what works before setting it for good.


The kicker will now need a mounting bracket, great, another thing. Otherwise it will land right on the trim tab on the port side.



And the bait pump will have to move somewhere, real estate is pretty limited back here. Can anyone shed light on anything I might be missing, or a better idea than I've come up with? Would be appreciated. Thanks.

And here's the bigger picture.

 

[froggy1150]

I would ponder either a thru the hull transducer (drill hole) or a thru hull (bond to bilge)

 

[Texasmark]

Take your existing transducer and locate a space near the keel (centerline of the hull area) and adjacent to the transom inside the boat. Clean the spot on the hull thoroughly, and rough up the surfaces of that spot on the hull and the bottom of the transducer.

Get a JB weld package and weld it to the hull. Squish out a big blob of it, mix it up good, make a big pile of it on the hull and depress the ducer into it till it quits sinking. Since you are working with 50-200 kHz sound waves, the steel in the JB gives you better conductivity than if you used plain epoxy. Mine is as I say herein. Course if you are using a multifunctional ducer (side looking etc.) obviously this wouldn't work. Signal loss is minimal and depth readings at speed are excellent.

 

[dingbat]

What transducer are you running that requires you to be that far off center line?

I’m running 12x12 tabs, 4” in on each side

Side scan transducer is centered 15” off keel, 7” off edge of prop. Leaves me almost 18” between transducer and tab on each side

 

[Bondo]

Ayuh,.... Trim tabs work the Best, when mounted as wide as possible,.....

 

[Thirsty Endgrain]

Take your existing transducer and locate a space near the keel (centerline of the hull area) and adjacent to the transom inside the boat. Clean the spot on the hull thoroughly, and rough up the surfaces of that spot on the hull and the bottom of the transducer.

Get a JB weld package and weld it to the hull. Squish out a big blob of it, mix it up good, make a big pile of it on the hull and depress the ducer into it till it quits sinking. Since you are working with 50-200 kHz sound waves, the steel in the JB gives you better conductivity than if you used plain epoxy. Mine is as I say herein. Course if you are using a multifunctional ducer (side looking etc.) obviously this wouldn't work. Signal loss is minimal and depth readings at speed are excellent.

What transducer are you running that requires you to be that far off center line?

I’m running 12x12 tabs, 4” in on each side

Side scan transducer is centered 15” off keel, 7” off edge of prop. Leaves me almost 18” between transducer and tab on each side

The xducer is a Garmin GT54UHD-TM. It does have sidescan capability so I don't think gluing it to the inside of the hull is an option for me. The requirement off of centerline that I'm referencing is the suggested 15" from the side of the prop to reduce cavitation. Mine is currently 10". I do see many pictures of folks running them even closer than that, butI would think that much closer and you would run into potential cavitation/prop slip issue territory?

What about mounting the tabs almost to the chines? Someone else suggested that to me who has the same boat. I'd have to just kinda span the strake a bit, so it's not the optimal location, but given the constraints maybe it would be fine? Something like this:

 

[Thirsty Endgrain]

Doh! Nevermind, it would cover my drain plug

 

[dingbat]

The xducer is a Garmin GT54UHD-TM.

I’m running GT51-M-TM. Basically the same setup.

The requirement off of centerline that I'm referencing is the suggested 15" from the side of the prop to reduce cavitation.

Pretty sure that is a typo in the documentation.

Had issues with SV clipping the out drive on my original install. Called Garmin Tech support who said the transducer was too far off center. Told me to mount as close to center line as possible w/o getting inside the radius of the prop.

Have always used 3-5” clearance on transom mounts as noted below.

My conventional thru hull transducer is center line, 18” forward of the transom

 

[JimS123]

The configuration of your transom is not ideally suited for trim tabs. Besides, do you really want to relocate things that currently work well, and then drill many more holes in the transom?

Your first idea was the best one. Except, skip the SE Sport 300 and install a DoelFin instead. If it turns out you don't like it, you can always take it off and all you lost was 39 bucks.

(60+ boat years on 5 different boats and I'm still enjoying the benefits. I read the directions (novel idea) and have not had any of the negatives that are often reported)

 

[Thirsty Endgrain]

Appreciate everyone's input, experience, and advice. Here's what I ended up with. Had to modify smart tab mounting brackets, trimming around my odd transom a little. Made a starboard mount for the transducer in case I need to move this way or that. Xducer is 3.5" or so from tab, and about 6"-7" outside the prop radius. All in all I think it should work, will see tomorrow morning or weds. Dog making weird face for scale.