Trim Tabs experience. Anyone know of a good make?

[solent fisher]

Hi, can anyone recommend a set of trim tabs or has anyone got experience using them?

 

My boat suffers from listing and porposing and i'm considering a set of Bennett http://www.magicmarine.co.uk/trimtabs/trim...xplanation.html but as they're quite expensive i want some advise and maybe look an alternative brand which may be cheaper or better.

 

Cheers,

James

[Ian Burrett]

Hi, can anyone recommend a set of trim tabs or has anyone got experience using them?

 

My boat suffers from listing and porposing and i'm considering a set of Bennett http://www.magicmarine.co.uk/trimtabs/trim...xplanation.html but as they're quite expensive i want some advise and maybe look an alternative brand which may be cheaper or better.

 

Cheers,

James

 

What size is the boat and what is the means of propulsion

[solent fisher]

What size is the boat and what is the means of propulsion

 

Hello. I own a small 16ft open cuddy fast fishing boat

which has a hybrid planning hull. The boat has a deep vee bow section which

tapers off to a mild catherdral at the stern. The boat gets on the plane

very easiliy but when its there suffers from porpoising at speeds greater

than 20 knots which can just be trimmed out with full engine tilt (down) and

moving a little weight forward. The porposing even accurs when the water is

perfectly flat and this is when it gets a bit hairy with no waves to drag

the hull and cut the speed bringing back control. I also need to correct

listing from beam/wind on seas and/or uneven weight distribution (worse when

one of fuel tank runs dry and I then lose the movable ballast). I'm always

on/off plane and ajusting speed for different sea conditions and weight is

always moving - lots of fishing gear, 2 x 25 litres fuel tanks plus I'm a

light weight and my fishing partner isn't! Boat is fitted with a Mercury 2

stroke 60hp which is the max HP for the boat.

[Dan]

I'm no expert but trim tabs might not be the solution! Why do you need such a big outboard? have you tried a 40? What does the manufacturer say about setting it up? What was that line from Jaws? oh yeah.............. we need a bigger boat! :)

 

Dan

Edited February 11, 2006 by Dan

[Manxman]

Sounds like you may be a little over engined, but not by that much. Do you have to have the engine on top revs to get 20 knots.

 

One reasonably cheap solution is to fit Dole Fins to your motor, they come in two sizes, for under 50hp and over 50hp. Takes twenty minutes to fit them.

 

I fitted them on my Honda 50hp, on a Seahog made a great difference to stability.

[solent fisher]

One reasonably cheap solution is to fit Dole Fins to your motor, they come in two sizes, for under 50hp and over 50hp. Takes twenty minutes to fit them.

 

I fitted them on my Honda 50hp, on a Seahog made a great difference to stability.

 

Using Dole Fins won't correct listing which is the main reason for fitting tabs also using these fins by using engine tilt to raise the stern is inefficient use of the thrust and leads to prop slip. Why do we think the boat is overpowered? It a planning hull similar to a warrier 165, not semi displacement and the boat cruises nicely at 4,000rpm. Yes a 40hp will get it up on the plane (just) but will be overworked and struggle when the boat is loaded.

[Fastd]

I have to agree with the previous suggestion of a dole fin. Fitting trim tabs would be very expensive and you would still have to alter them every time someone moves in the boat. They only affect the horizontal position of the boat when at speed

 

Trim tabs are designed for use on larger motor cruisers where the hull weight is a far greater proportion of the total all up weight of the boat. With a 16footer witha hull weight of say 450 kg the effect of someone moving from one side to the other is going to be quite dramatic. The only answer is to get a bigger heavier boat.

 

The problem of porpoising is different as this suggests that the boat is falling off the plane. The trim and position of the engine are the main reasons for the way the boat planes. Check with the manufacturer for the recommended prop pitch and its depth. It could be that the prop is not at the correct depth below the hull.

 

 

 

I had major problems with balance in my boat when I first bought it as someone in their wisdom had decided the wheel, batteries, fuel tank and auxiliary mounting looked best when positioned to the right. By the time you add the driver to this you have one major list built in. I have now moved evrything but the wheel and the boat with pilot now runs straight.

 

 

 

Face the fact that small boats will always move with different weight distribution. I have recently been driving a 28 ft cruiser with twin volvo stern drives and even on this boat you have to occasionally adjust individuall drive trims to balance the boat.

 

 

 

Dave

[Guest sandpipper]

Fastd,i was about it sounds like the engine is set too low below the hull which would make the boat a bit unstable.

solent fisher have you thought about making some fixed trim tabs it worked for me.

[Steve Coppolo]

Before you start messing with trim tabs, etc, make sure that you've got the right prop on your outboard and that the outboard is set at the optimum height on the transom.

 

You need to find out what the maufacturers recommended (full throttle) RPM is for that engine and compare it to what you are getting. You may not be getting enough RPM's in which case you need to drop down in pitch on your prop.

 

A good guide for height of the engine on the transom is the anti cavitation plate being level with the bottom of the hull. If the engine is set up like this you can move it up or down a hole and see which gets the best results.

 

You need to do these things anyway, so it's not a waste of time. If it doesn't improve things then you can start playing with trim tabs, etc, although a 16ft outboard driven boat really shouldn't need them.

[chris parker]

I have a set of Bennett Hydraulic on my boat, great for trimming side to side rather than moving stuff around. They slow the boat though when I use them. Don't know if they stop porpoising as my rig didn't suffer from it before I fitted them.