38DA - Upsizing Trim Tabs

[juggernaut1]

I did post some pics in the 380 thread but thought I would make a specific thread on a recent trim tab upsize.

The original specs were 24 x 12 and are canted due to the shape of the transom

The new are 26 x 15.5 (still canted) plus 3 inch drop fins - which translates to 40% more surface area plus the added benefit of the drop fins. I could't go any wider due to the limit on the outer edge.

Boat can stay on the plane down to around 15 knots and may go possibly lower - picked up 2 or 3 knots at the same rpm compared to no tabs and obviously a flat ride. Need to be on the ball when coming off the plane or run an auto trim tab controller - I'm running a Mente Marine controller but the new Bennett Pro controller would also be a great add on when using larger tabs.

 

[Doc O Rock]

Did you have to change or move the actuators? I have been thinking of doing the same to mine before the boat goes in the water.

 

[Bop]

I did post some pics in the 380 thread but thought I would make a specific thread on a recent trim tab upsize.

The original specs were 24 x 12 and are canted due to the shape of the transom

The new are 26 x 15.5 (still canted) plus 3 inch drop fins - which translates to 40% more surface area plus the added benefit of the drop fins. I could't go any wider due to the limit on the outer edge.

Boat can stay on the plane down to around 15 knots and may go possibly lower - picked up 2 or 3 knots at the same rpm compared to no tabs and obviously a flat ride. Need to be on the ball when coming off the plane or run an auto trim tab controller - I'm running a Mente Marine controller but the new Bennett Pro controller would also be a great add on when using larger tabs.

View attachment 48734

Did you paint your rudders/exhaust/tabs yellow or that just the way the pic is showing on my phone? If you did, is there a reason?


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[joeyleggz]

Did you paint your rudders/exhaust/tabs yellow or that just the way the pic is showing on my phone? If you did, is there a reason?


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It's prop speed heard it supposed to be fantastic for nothing adhering to it


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[joeyleggz]

My question is is this custom made ?if so do you have plans for this or is this an aftermarket purchase if so where do you source it? Nice paint job by the way!


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[juggernaut1]

Just chiming back in with responses:

No I didn't move the actuators - just had the new tab stitch welded to the existing tab for a quick mod. As you can see if I had moved the actuators I could have used more of the transom towards the tunnels for a greater span and used less chord to achieve the same area which is supposed to be more efficient.

Yes the tabs are custom and yes I do have rudimentary plans I gave to the fabricator which I can upload for you. That said, your tab sizing will be specific to your boat. I used the sizing charts on the Bennett and Turtle Marine websites.

Correct the coating on the running gear is PropSpeed. My boat is in the water all year except when hauled. After 16 months in the water the previous application of PropSpeed was virtually perfect as was the Micron 66 (salt water only) with a diver only going down once in this period back in November. PropSpeed is popular where I boat for very good reason. Micron 66 and Micron Extra are also popular and work well in our conditions too. Whilst more expensive I don't have to haul as often and will probably go to 18 months this season based on what I saw at 16 months. If your boating season is such that you have to haul annually regardless then I would probably use cheaper coatings/anti foul.

 

[juggernaut1]

Quick update - over the weekend I was able to get the boat to plane down to 12 knots with the tabs fully extended in perfect conditions with full water and 3/4 fuel and all our gear.

Fairly happy with the bigger tabs as it was previously ploughing at this speed with a fair bit of bow rise.

 

[Creekwood]

Just looking at your picture, I noticed that the underwater exhausts exit just ahead of the tabs. I believe it is like that on all similar inboard Sea Rays, mine included. Makes me wonder if the exhaust gas stream has any impact on the force that the tabs can exert.

 

[juggernaut1]

I thought they worked more like a Venturi, drawing out the ex gases :huh: