Dummies guide to a starting point with trim,,, legs and tabs

[Ian MacAulay]

Ever since owning the boat my tabs have not worked so I have just been using the trim on the legs

now I have tabs working what's the best and correct way to correctly trim...? Do I trim on the legs and then fine tune on the tabs or other way round also start with the tabs right up?

sorry for dumb question but have no experience with tabs


thanks

Ian

 

[BruceK]

What boat / size do you have. I find on mine (36 LOA) that trimming legs makes virtually no difference to bow attitude unless taken to the extremes and for the tabs to have sufficient effect they are also trimmed too far out which can cause driver induced oscillation when coming off the throttle. Trimming is mostly for levelling the boat out across the beam in which case trimming the legs makes no difference.

 

[CX54WEK]

We tend to leave the trim tabs well alone on our S23.

 

[julians]

Use the tabs to correct left/right listing due to Un even weight distribution,wind,waves etc.

And use a combination of leg trim and tabs combined when you want to adjust the hulls angle of attack on the water.ie bow up or bow down.

 

[CharlieAlpha]

I'm sure there are text book answers and I'm not an expert but I think Ian (the OP) would like some guidance so here goes
Every boat is different so these are only indicators. On a calm day (flattish seas) set boat trim all the way up, well you accelerate onto the plane leg trims tucked all the way in (say -5) [I always keep leg trim same on both engines] until you get to your 'normal cruising speed say 23knts, leave throttles alone a adjust both leg trims out at 1 or 2 intervals and watch the boats speed it should increase until you get to about +2 or +3 fine tune legs in and out until you discover the max speed was about +1 on mine (remember all boats are different). So you end up with a leg trim level that you can use for your starting point for the next time you get onto the plane.

Now use the boat trim to level the boat horizontally, if the port or starboard side is higher or lower than the other due to loading of crew etc, trim down on the low side which will lift that side.

If you want to go slower say 18knts and stay on the plane you are going to have to apply some nose down boat trim (or adjust leg trim) on both otherwise the nose will rise and slow the boat down even more. Also in big head on seas you will get a more comfortable ride with the nose down and of course can go slower and stay on the plane.

Hope that has given you a starting point from then on it experimental, these days I cheat as I have the luxury of auto trim

 

[Sailorsam101]

I use the tabs on my Targa 33 to bring the bow down if it's rough. It does have a big effect and works well at stopping waves over the bow and to reduce slamming which is what the Mrs hates.

As for leg trim..never used it while underway

 

[CX54WEK]

I use the tabs on my Targa 33 to bring the bow down if it's rough. It does have a big effect and works well at stopping waves over the bow and to reduce slamming which is what the Mrs hates.

As for leg trim..never used it while underway

On our single engined boat we use the leg trim to have the same effect.

 

[lionelz]

I have to use my trim tabs quite a lot, they are used for keeping the boat level across the beam, however on my boat I have to use them as well to assist in getting on the plane especially if I have weight on the boat. By using the trim tabs, it raises the rear of the boat out of the water. I know a lot of people say don't use them if you don't have to but I find them very useful and help a lot in getting the best ride. Remember that by lowering your port tap, you will raise the port side! Although funny enough on my boat for whatever reason the previous owner cross wired the tabs so my port switch operates my starboard side tab. In regards to outdrive trim, I always have it fully trimmed down/in until on the plane and then trim out/up slightly. In basic term, trim tabs raise and lower the aft of the boat, outdrive trim raises and lowers the bow.

 

[julians]

Although funny enough on my boat for whatever reason the previous owner cross wired the tabs so my port switch operates my starboard side tab.

Thats standard practice, the vast majority of tab installs (or certainly every Bennett trim tab install I have used ) are like that. Its so that the buttons reflect the movement of the boat ,not the movement of the tab. Ie press the upper half of the left hand button makes the boat lean to the left (ie starboard tab is lowered) . I' d much rather they were wired so they reflect the movement of the tabs not the boat.

 

[lionelz]

Thats standard practice, the vast majority of tab installs (or certainly every Bennett trim tab install I have used ) are like that. Its so that the buttons reflect the movement of the boat ,not the movement of the tab. Ie press the upper half of the left hand button makes the boat lean to the left (ie starboard tab is lowered) . I' d much rather they were wired so they reflect the movement of the tabs not the boat.

Mine are lenco ones, but I spent my time learning what the tabs do and now have to think about doing it rather that my normal thought process of left low pressure that button, now I have to say left low pressure right button. When you are as simple thinking as me that's a challenge ?

 

[Ian MacAulay]

Thank you all for taking the time to offer help and there are some very very helpful pointers. The boat is a Cranchi Aquamarina 31 and only the other week i had it out to fit a thruster and get tabs working again so all learning for me.

Thank you CharlieAlpha for this great reply its exactly the help i need on where to start and how to go about things and its spot on.

I'm sure there are text book answers and I'm not an expert but I think Ian (the OP) would like some guidance so here goes
Every boat is different so these are only indicators. On a calm day (flattish seas) set boat trim all the way up, well you accelerate onto the plane leg trims tucked all the way in (say -5) [I always keep leg trim same on both engines] until you get to your 'normal cruising speed say 23knts, leave throttles alone a adjust both leg trims out at 1 or 2 intervals and watch the boats speed it should increase until you get to about +2 or +3 fine tune legs in and out until you discover the max speed was about +1 on mine (remember all boats are different). So you end up with a leg trim level that you can use for your starting point for the next time you get onto the plane.

Now use the boat trim to level the boat horizontally, if the port or starboard side is higher or lower than the other due to loading of crew etc, trim down on the low side which will lift that side.

If you want to go slower say 18knts and stay on the plane you are going to have to apply some nose down boat trim (or adjust leg trim) on both otherwise the nose will rise and slow the boat down even more. Also in big head on seas you will get a more comfortable ride with the nose down and of course can go slower and stay on the plane.

Hope that has given you a starting point from then on it experimental, these days I cheat as I have the luxury of auto trim