Boat Projects Forum

Fitting Smart Tabs

by argonaut » 25 Apr 2015, 21:28

Fitting Smart Tabs (avail as pdf : http://tinyurl.com/qg3ubqu )

Image


My boat a Maxum 1800 SR3 while a great runabout suffered from serious bow rise on initial power on, if you are trying to pull a deep water start mono-skier out of the water .... you will lose all forward vision .. as the bow points skywards – even though fully trimmed in.
This is very undesirable for 2 key reasons ... firstly it is dangerous as you have no view of anything in front of you, and secondly the boat is very slow to get on plane when it is pointing to the sky.
Once on plane the boat handles well.

One solution would be a lot more Hp .......... not an option for me.
The other option is to modify the hulls planning characteristics by fitting Trim Tabs.

If you are not familiar with these, they work by providing a plate on the transom that the water coming along the hull hits, it then lifts the stern of the boat, which in turn lowers the bow ... the size of plates, position, angle all affect the trim adjustment.

For many years you could have fixed tabs ... but while the boat got onto plane, they then provided drag .. and affected top end, and resulted in poorer fuel consumption.

The option was to have adjustable Tabs that you lowered to get boat on plane then raised once boat up to speed adjuating as you ran, to tune the hull position in the water......... these typically have expensive electrical or hydraulic actuators.

Then there came Nauticus ... and Smart Tabs

These are Tabs that are fitted with a damper, and by sizing correctly they can push Tabs down while at rest allowing boat to have max lift at stern, then once underway the force of the water pushes Tab up out of running line so they provide no drag.
This automatic function also by its nature keeps hull balanced in cross running seas for example.
The big bonus is no cabling, electrics or hydraulics ... simplicity for install.
Nauticus provide multiple sizes of Tabs and different dampers .......... you put your boat details into their chart and it advise the correct items.

http://www.nauticusinc.com/index.html

Video of them working is here:
https://www.youtube.com/watch?v=sbOInDmFIVE#action=share

I salt water boat so I chose the SX range – nothing to corrode


Fitting

The fitting of them really is pretty simple ....
There is a video on-line
http://www.nauticusinc.com/smart_tabsSX_automatic_trim_tabs.htm


I started off by identifying on my Transom where I would fit the Tabs
The ideal location is as far out on the transom as you can get them, as long as there is no interference from the Chine line ........ the further they are away from keel line the better they work.

On my hull I decided to fit them as shown below by A & B marks:

Image



The immediate issue will you notice is that the proposed position then interferes with the tie-down points.

I worked around this by fitting 2 stainless steel eye bolts to the rear trailer chassis cross beam, in such a position to avoid the tie down straps fouling on the tabs.


Image



I then as per the video fitted the mounting plates, and the Tab actuator bracket


Image

I went for the added option of fitting PR500 retractors .. these allow you to fully retract the Tab so if you want to beach your boat for example there is no risk to damaging the Tabs.

The Retractors arrived in a pretty dull finish stainless steel – I polished them up to a mirror finish so they matched the other bright work on the boat.


Here is a pic of the Tabs in the normal down ‘run’ position: Image



And here they are retracted up into the ‘out of use’ position: Image


This picture also shows the 5 holes on the TAB, this can be used to tune the response ... and if required ‘stiffer’ or ‘softer’ dampers can be fitted.
In my case Nauticus had experience of my boat, matched the correct damper and advised the hole No. 3 ... and it worked fine.


The fitting was easy enough ... mark out position with masking tape ... measure, re-measure and then measure again ........ making sure the proposed Tab position allows the actuator bracket to fit without fouling anything. Mark holes position with a felt pen.
There is a paper template in the kit to aid marking out ... key point is that finished Tab lower edge is flush with running surface of the hull.

You use a 1/8” pilot drill to pierce the Gel coat and then drill accurately with a 3/16” drill to just longer than screw length. Countersink holes in Gel coat to prevent crazing, apply a marine adhesive mastic and fix the screws.

Then go use !


Results

Immediate extremely noticeable reduction in bow rise, the amount of bow rise was significantly reduced, and what there was .. happened for much less time as boat planed in a greatly reduced time.

This made towed sports markedly better – totally transformed the hull performance.

The boat was much more stable, on that key period between applying full throttle and coming up on plane.

This was an incredible improvement to the Maxum.

The facts quoted are:
    • Smoother and Faster Acceleration - (Great for Skiing)
    • 40% less Bow Rise and 35% Lower On Plane Speed - (Great for Tubing )
    • More Top Speed and No Porpoising or Chine Walking
    • Improves Handling and Smoother Ride In Any Water
    • Improved Fuel Economy (11% +)
My results support all the claims (although no hard figured for fuel consumption)



The cost
The pair of Tabs (9510-60 sx ) were £65
And £20.. for the PR500 retractors

That means the system cost less than the cost of a tank of fuel, and made an amazing difference.

They do all that they claim to do – if your hull has bow rise, these are a superb investment.
Monterey 194fs with Monster MTK tower + water and SkySki = fun ...... towed by JEEP Cherokee Limited
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argonaut
 
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by SpiD » 01 Nov 2015, 15:20

Well known product, useful for boats in your size range and good value for their use.

If looking for other common funtioncs of trim tabs (like compensating a list when planing in side winds or uneven weight distribution), you need tabs that can be controlled individually from the helm.
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by argonaut » 01 Nov 2015, 16:53

I can't comment on other boats .. but on the Maxum I put them on they stopped any list when running against a beam on sea.

The dampers self adjust within in a range .
So once set up they do their thing.

As watersports is my thing didn't try in 4' swells or similar... but for my use they were superb.

My current boat didn't need them but would have no issue recommending them if your boat does have bow rise.
Monterey 194fs with Monster MTK tower + water and SkySki = fun ...... towed by JEEP Cherokee Limited
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by Dave » 09 Feb 2016, 12:57

Although not applicable to my boat, I have to say that this is a really well written and laid out useful thread, with great pictures and information, and it made me want to read it all, even though I was not going to be able to use the product.

Excellent post. Thanks
Voodoo Doll - Sea Ray Sundancer
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Location: Upper Hamble River


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