Did you talk to Lectro about mounting on a reverse angle? Did you need a different actuator size?
Yes, and yes. Let me know if you have any trouble finding the info in the thread I posted.
Dan and Clairborne at Lectrotab are most helpful.
The new hulls are not as robust as the older, so I would probably stick with the
exact dimensions and layout I provided, it's been tested fairly extensively and works very well.
https://jetboaters.net/threads/trim-tabs-options-wake-surfing-and-cruising.12031/page-2
Page 2, post #31 has most of the detail:
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We are working off of the Lectrotab design of
@Bruce and Dan Roberts of Linear Devices Corp (parent company making Lectrotabs). The standard tab dimensions in that kit are 12"x12" (chord x span), 14" actuator, and the attachment point is at 7.75" from the hinge/hull.
Those work really well for boat attitude adjustments, or as regular trim tabs. However, there are several issues with the above tabs/actuators if used as wake tabs, the way I see it. Most notably, those overall dimensions would NOT be compatible and potentially interfere with other wake shaping devices. For example, Gantlin Wake Wedge install would NOT be possible. Or other devices, such as an adjustable ASP-like platform (AKA Swatski's Tail, LOL), etc.
Shortening the actuators, the ONLY readily available solution, would dramatically reduce the tabs' range of motion due to the reduced stroke of the "short" actuator, 2.25" standard vs 1.5" "short". The only way to compensate for that is to move the attachment point closer to the hinge/hull, which would also weaken the load rating, which needs to be compensated for with the shorter chord (but longer span to retain the surface..). Etc, etc.
So, long and short, here are some considerations and solutions we came up with.
SPAN
The general recommendation is using tabs that are 9 inches in chord (distance from transom to trailing edge of the tab) the tabs should be one inch in span (width port to starboard) for each foot of boat. Accordingly, tabs for my boat should be 24" x 9".
The largest span of the tab that can be easily fitted is 16" (again, that is the width, or port to stbd measurement).
Making the tabs
16" x 9" would do the trick, close enough to 216 square inches to make a noticeable difference in lift without placing undue stress on the system. 16x9 is also the same surface as 12x12 that works extremely well in the above mentioned 23/24' Yamaha boats.
Importantly, 16" is also the largest span to fit exactly flush with the transom (in my 2016 240).
TABS PLACEMENT
On boats powered by outboards or sterndrives it is necessary the trim tabs not be placed too close to the drive unit to avoid disturbing the water flow to the propeller thus causing ventilation. This is usually no closer than 7”. General rule is no less than 8" from the center of the drive. 16x9 tabs would fulfill those criteria, however that is probably an overkill anyway as the intakes in our jetboats are far removed and would not be obstructed with tabs. I have learned however to be conservative with any such estimates. That said, looking at the picture from
@Williamsone46 (in an above post) - the tabs would be out of the water and out of the way of intakes FOR SURE at planning speeds. So, 16x9 tabs would work well here.
SHORT vs STANDARD ACTUATOR STROKE vs RANGE OF MOTION
This has been the trickiest item to tackle and plan around. Standard actuator has a stroke of 2.25" (fully extended) and affords approximately 16.6 degrees of tab movement, I think (see below). To determine how a switch to the short actuator (with a 1.5" stroke) affects the range, we did a little back-of-the-envelope calculation here (where
a is the measurement between the hinge/transom and the actuator attachment point in the tab):
(this was drafted by my son, as we were driving and talking, he just whipped this up on his tablet)
Basically (some oversimplifications notwithstanding, such as ignoring the change in the actuator angle of attack - which should be fine as it only moves a total of <20% of its length, etc.):
The current standard actuator attached at 7.75" affords the range of motion of approximately 16.6 deg.
This would be mostly retained by using short actuator attached at 6" from the hinge/hull.
That is the final "best case" scenario we could came up with:
1. 16"x9" tabs
2. short 10" actuators with 1.5" stroke
3. 6" attachment point (in the center of the tab's span)
Additional considerations are a few. Taper would be initially bend up, but possible "drop fin" add-ons (AKA "DF12" in Bennett parts) would be considered, etc, all pending test results in the water. Chine overlap is not an issue with this design (I believe). Internal hull fiberglass enforcements of actuator attachments are strait forward, not discussed here.
Here is a rough sketch of tabs' placement:
(Short actuators' attachment points in the hull would not interfere w/ Wake Wedge mounting points / tie down eyes, and tabs would not interfere with fins)
"
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I had to modify a couple of things on my install to clear the step in my AR230 hull, but yours will not be like that. Good luck
