Explain trim tabs to me.

[megaxyu]

Hi all,

I am new to boating and looking at getting a 12' Saturn SD365 with a 15hp engine. I understand that it will be difficult for the boat to get on plane when it is loaded.

I am thinking about making my own trim tabs but don't quite understand how they work. From what I gather one would generally want them to be at a slight down angle when getting on plane and then raise them up ones the boat is on plane. Is this the reason to use an actuator? Will the pressure on the trim tabs once the boat is on plane cause them to move up?
Is there a set angle that these should be set at when getting on plane? Will the angle matter afterwards?

Any input is appreciated

Cheers,

Mike

 

[Peter_C]

Re: Explain trim tabs to me.

The majority of the people that want added lift on their SIB use a wing mounted on the outboard lower leg to create lift.

http://www.iboats.com/Hydrofoil-Sta...3211756--session_id.407191812--view_id.217147

There are some trim tabs available for small boats, but I am not familiar with their use myself.

 

[likalar]

Re: Explain trim tabs to me.

Normally tabs or foils are installed after a true need is realized. I would do some trials with the stock set-up. Try different positions for the load (fuel tank, people, etc.). Also, try different trim positions for the engine. If you decide you need tabs (or a foil), it seems you have a good understanding of them. Yes, the pressure should cause the tabs to move up automatically, but from what I've been reading, results often vary. I have an 11' Rib with a 20hp, and no extra hardware was needed. Conversely, our 14' tinny with a 20hp benefited greatly from a foil (just me and the dog; with too much weight in the stern). I had looked into tabs, but decided on a small Doel-fin, which did the trick. I wish I could advise you better about tabs. Somebody will chime in. I just watched a You-Tube video; nice looking boat! Good luck.
Larry

 

[Lyle29464]

Re: Explain trim tabs to me.

The tilt setting on your engine will do all you will need.

 

[nobrainsd]

Re: Explain trim tabs to me.

Using the tilt setting or a foil like Doelfin does have it drawbacks. You may end up with the outboard in a position that keeps your bow down, but is not the ideal position for performance. This can affect your top end speed and may generate more splashing. Also, unless you have power trim it is not easy to adjust the angle of the outboard when underway to optimize the position of the outboard. How much forward tilt or foil angle you need will change as you get up on a plane and in different sea states. I ran with a foil on my outboard for a while, but did not like adjusting the tilt all of the time (even with power trim). In addition, if you run anywhere with much kelp those hydrofoils are great kelp catchers.

The smart tabs I have work great and keep my bow down on hole shots and work well with the outboard trimmed properly for a fast splash reduced run. The smart tabs have adjustable resistance for different boats and power combinations. They also do not grab kelp. They are a little more of a hassle to install and need to be removed to roll up a boat, but for me the performance advantage made it more than worthwhile. My 'whale tail" just sits on a shelf.

A properly balanced load in your boat is still the most important first step.

 

[megaxyu]

Re: Explain trim tabs to me.

The smart tabs have adjustable resistance for different boats and power combinations

This is where I'm struggling to understand. How would I know how much resistance should be applied to the smart tabs ? would this resistance need to vary ? couldn't I just have them set at a certain angle to get on plane and have a second position that is out of the way ?

 

[davezz]

Re: Explain trim tabs to me.

Here's the Mfr site for Smart Tabs. Read, look, and learn. I have them on my 19' runabout and they do help. I just got my 9' SIB and will be experimenting with planing.
http://www.nauticusinc.com/

Contact Nauticus if you have more questions. They are very helpful.

 

[nobrainsd]

Re: Explain trim tabs to me.

In the end I installed my smart tabs, guessed at a setting and then looked over the transom to see what was happening when on a plane. I now have them set so they come up at speed, but still vary their angle while I'm moving. My top end doesn't suffer much at all, maybe 1 mph. I think the boat handles better in waves with the tabs active. You can certainly pull them up all the way if you rig them for beaching (it's in the instructions). But I let them down when I launch and forget them until I'm beaching or trailering. If you don't like your bow rise on take off and you want to plane faster they do work. I suppose if you are really under powered and barely getting on a plane it might be nice to raise them and pick up a little top end speed, but it would have to be a really borderline proposition to make that worthwhile IMO.