What are trim tabs for ??

[Alfa Spirit]

The question is in the title, can trim tabs decrease torque effect for a mono hull? Thanks

[ScarabChris]

Trim tabs are to correct or adjust the running attitude of the boat. Yes they can compensate for torque lean on a mono. Put the tab down on the low side of the boat. They can also keep the bow down on stern heavy boats and eliminate proposing (hopping of the bow) at higher speeds by putting both tabs down.

They are very effective on real boats for leveling the boat with an uneven weight load or to adjust the ride attitude at high speeds. They can also increase rough water performance because they extend the running surface of the hull.

[Alfa Spirit]

Ok, this is for a 39" MHZ deep vee hull. Is this model from OSE will work, 37mm wide x 30mm long x 12mm tall? Motor is a Castle Creations 1717.

[ScarabChris]

Putting the biggest tabs you can fit is always a good rule of thumb. The bigger they are the less adjustment they need. When mounting them make sure the bottom of the tab is slightly higher than the hull bottom. This way if an adjustment is not needed they will not impact the boats attitude much if at all.

These are the basics for trim tabs in general for real boats, shouldn't be any different in model boats. Someone with the same setup as you are building might be able to comment on those particular tabs.

[Alfa Spirit]

I understand but the MHZ Fountain Electro is a semi scale hull and big tabs isn' t very nice... That' s why I am looking to descent size tabs

With a FOUNTAIN boat this will be bad looking

[DISAR]

I would suggest to run the boat first and then decide if tabs are needed or not.

[ScarabChris]

Well the transom of RC boats rarely look scale so the tab size won't matter because that single stinger drive and offset rudder won't look scale either.

And I say rarely because I like a scale look. Here are my boats.

This is my Scarab Sport replica of my real boat. The hull is 31" long and those tabs work very well.


This is the transom of my current build. 54" Fountain with z drives and those are MHZ tabs. It will be a week or so before I can see how they work.

[sailr]

Where did you get those outboards!?

[forescott]

You can buy those ep-1 outboards here on ose.

http://www.offshoreelectrics.com/pro...od=dh-aqub7861

[ScarabChris]

Yes they are the EP1 outboards shown above. I put brushless motors in them and painted them to match my real Evinrudes.

[AlanN]

I understand but the MHZ Fountain Electro is a semi scale hull and big tabs isn' t very nice... That' s why I am looking to descent size tabs

With a FOUNTAIN boat this will be bad looking

Slide the trim tabs farther out from the strut. Let the strut and prop see the water first. Then mount the tabs 1/16"-1/8" higher than the bottom of the boat. This allows the hull to settle in the water and then you can adjust the tabs from there. Looking from the rear....the left one adjust for striaghts and the right one adjust for ride attitude in the turns. Be careful how low you adjust them, too much and they cause too much drag. I prefer 4 individual tabs but what you picked out will work. When using 4 tabs adjust the inside tabs first and you should not have the outside tabs set any lower than the inside ones.

[m4a1usr]

Chris,

The cav plates on your outboards behave just like trim tabs if the prop is running submerged. Not sure if you were aware.

John

[ScarabChris]

Chris,

The cav plates on your outboards behave just like trim tabs if the prop is running submerged. Not sure if you were aware.

John

You are correct and yes I am aware of that. I have been running real boats my entire life. Adjusting the trim angle will have similar effects as adjusting the tabs. Having both adjustable tabs and drives means you can dial in a sweet spot.

[Alfa Spirit]

Slide the trim tabs farther out from the strut. Let the strut and prop see the water first. Then mount the tabs 1/16"-1/8" higher than the bottom of the boat. This allows the hull to settle in the water and then you can adjust the tabs from there. Looking from the rear....the left one adjust for striaghts and the right one adjust for ride attitude in the turns. Be careful how low you adjust them, too much and they cause too much drag. I prefer 4 individual tabs but what you picked out will work. When using 4 tabs adjust the inside tabs first and you should not have the outside tabs set any lower than the inside ones.

Thank you, I think trim tabs can be used like this. The stinger is a Speedmaster with 2 rudders.

[john finch]

The question is in the title, can trim tabs decrease torque effect for a mono hull? Thanks

Yes to a degree. Most all model boats with a single prop will torque to the right as viewed from the rear of the boat as you know or you would not be asking this question. The right trim tab should be down about 1/16th to 1/32 of an inch more that the left tab. This will help with torque. Also, moving the strut just a bit to the right of centerline will lift the right side of the boat a bit resisting the torque. Also, mounting the rudder more to the right of the strut will tend to lift the right side of the boat thus also helping to give a level ride. Note, I am just talking about torque roll, which is what you asked for. These combinations in harmony will let the boat run without torque roll issues.