Trim Tab Experiment.

[scottar]

Since I purchased my rig (Seafarer Victory wit E-Tec 200HO) I have been constantly tinkering to modify some of the handling traits that have been induced primarily by transom weight. Modifications to date have included various prop trials, the trialing of various foils and the fitment of trim tabs. The end game has been to increase hull efficiency at slow planing speeds and thus reduce fuel consumption when offshore and the going gets "tough" so to speak.

The latest "addition" has been to fit extra plates under the trim tabs to increase their size from 12x9's to 12x12's. This has also reduced the amount of distance the front edge of the tab is mounted above the transom when fully retracted to almost nothing. While I have only done one trip, results thus far are encouraging with the following traits noticed -

- less tab angle required to achieve a level plane
- A slower achievable planing speed
- A slight increase in fuel economy when running slow - Last weekends fuel consumption for a trip I have done a few times now was down from typically 100 litres to 90 and conditions offshore were rougher than I would normally fish.
- For the first time ever, the necessary reduction of tab angle for running in a following sea. It was a bit rougher on Saturday but it was the first time I have had the boat "steered" by a wave even running with near full tabs down.

Apart from the following sea experience, which was easily rectified, at this stage I would say it has been a positive result and is swaying my opinion towards "bigger is better" when it comes to tabs.

[Moejoes]

Hi Scottar,
Not that I'm any expert, which I'm sure one of those stalkers will surely comment on soooooonnnnnnnnn!!!!!!!!! ;D
I'm actually shocked you were running with tabs deployed in a following sea.
A dangerous tactic.
Probably the reason why you experienced what you did and would not recommend it as you are pushing the nose deeper into the water.
You want the nose up in a following sea, nose down in a head sea which also stops the banging but you will burn more fuel in the process.
There are pro's & con's with large tab plates.
Pro's will give you better planning lift and better fuel economy.
Con's will give you more arse end lift in a following sea which you do not want hence the experience you had.
Even having them fully up can still create lift in heavy following seas as you have more surface area in the rear.
Just my 2 cents worth from experience :P
Cheers Rob

[scottar]

Hi Scottar,
Not that I'm any expert, which I'm sure one of those stalkers will surely comment on soooooonnnnnnnnn!!!!!!!!! ;D
I'm actually shocked you were running with tabs deployed in a following sea.
A dangerous tactic.
Probably the reason why you experienced what you did and would not recommend it as you are pushing the nose deeper into the water.
You want the nose up in a following sea, nose down in a head sea which also stops the banging but you will burn more fuel in the process.
There are pro's & con's with large tab plates.
Pro's will give you better planning lift and better fuel economy.
Con's will give you more arse end lift in a following sea which you do not want hence the experience you had.
Even having them fully up can still create lift in heavy following seas as you have more surface area in the rear.
Just my 2 cents worth from experience :P
Cheers Rob

Cheers Rob. I do understand the issue - it's just never been a problem with the 12x9's. I set the tabs for ride/speed as per sea conditions and in reality with the smaller size I had to try pretty hard to upset the boat in the sort of conditions I would normally be out in. At the right speed running in a following sea has never produced any exciting moments even with near full tabs down - indeed if you took tab off at the speed I was doing you would then fall off the plane. With the extra area of the larger plane there is obviously (well it's obvious now ::)) enough there for the water to catch and have an effect. Once I reduced the tab angle a bit (not right off though) handling returned to "normal" for the run home.

Into a head sea as far as fuel burn is concerned - it seemed the more the better. I would be regularly running around full tab down in any sort of chop - even more so if the bait tanks were full. I actually use less fuel (a lot less - about half) due to the hull planing properly and not pushing water with the bow in the air at the sort of speeds I travel at when it gets choppy. Moving more weight forward isn't really an option - we do take the odd bit of water over the bow at displacement speeds already if it's rough - the girl is big boned. Now I don't need as much angle and I suspect the drag is less because of this - hence the better economy.

[Back In Black]

No seriously Scottar, listen to Moejoes cause he knows;D;D;D

[Moejoes]

What did I just say Scottar.
Big baits are sometimes better :P
That's one hooked up, now just for the other to take the bait hahahahahahaha


No seriously Scottar, listen to Moejoes cause he knows;D;D;D

[Moejoes]

All boats run and handle differently.
My frigate didn't have as much of a problem until I put 12x12's on mine ( My opinion ).
It obviously gave me more area at the rear hence the arse lift in heavy following seas, even fully up.
I use the twin motors to trim.
Like I said, Pros & Cons.
The Pros out weighed my Cons so I left them on and started looking at other avenues to combat the problem.
Eg; Planning strakes, adjusting engine heights
Now looking at slightly heavier and more powerful motors on the rear for the better I can only hope ::)
I'm going to even pull that stupid remote search light ( that never works ) off the front to lighten it up as I'm sure it equates to 20 plus kgs up front when you calculate how far off centre of gravity it is ( 4 to 5 meters ).
For me, it's a case of getting in a certain sea and I think can I improve it just that little better.
It all adds up and helps towards the end result of a better riding boat all round.
Maybe I drive mine too hard in certain conditions and should maybe slow down that little, as going up to 10kms slower does make a huge difference in rough conditions.
All you can do is keep trying different things in different sea conditions.
Hopefully you'll end up with something you are happy with.
Let us know how you go.

[scottar]

Will do Rob. Like I said - early days but positive so far. Main reason for the extension was that I was running around at full tab down fairly frequently - figured a bit more would be worth a shot. Just got to iron out the "bugs". Every time I have made a modification there has been some sort of learning period attached with the changes in handling that have come about.

[Back In Black]

Don't mention planing strakes!! Bannana will get involved & drop another 50K off your already devalued tub:o:o:o

[Moejoes]

What???? You mean I'll have to pay someone $50k to take it off me :P


Don't mention planing strakes!! Bannana will get involved & drop another 50K off your already devalued tub:o:o:o

[Moejoes]

So true, all trial & error.
Then once you get it right, you sell it and start again as you get bored and have nothing left to do ;D


Will do Rob. Like I said - early days but positive so far. Main reason for the extension was that I was running around at full tab down fairly frequently - figured a bit more would be worth a shot. Just got to iron out the "bugs". Every time I have made a modification there has been some sort of learning period attached with the changes in handling that have come about.

[Vitamin Sea]

Moejoes is 100% here, dangerous to run tabs down with a following sea, not recommended at all.

[soulfish]

I know how to fix your problems Scottar & Moejoes...just buy a Cat..i know deep down you both want one..and you wont need trim tabs!...just think of all that money your wasting on your overseas holiDAYS (yes 2 planned & payed for with banana ,moejoes)...I hope you don't get dementia rob and forget your adventures with banana after outlaying all that money...on the other hand if you buy a cat you can look at it everyday in the shed and your body will thank you for it when your older....money well spent.

[Back In Black]

When I heard you guys were off to the US, I assumed you were taking Moejoes down to the Fort Lauderdale boat show to pick up a cat cause he loves yours so much:smitten:

[Crunchy]

It will be very boat dependant, the 12x9's I got are almost too active, by that I mean just a touch on the button has a big impact, if fully deplpoyed they wouild stop the boat!

[scottar]

I know how to fix your problems Scottar & Moejoes...just buy a Cat..i know deep down you both want one..and you wont need trim tabs!...just think of all that money your wasting on your overseas holiDAYS (yes 2 planned & payed for with banana ,moejoes)...I hope you don't get dementia rob and forget your adventures with banana after outlaying all that money...on the other hand if you buy a cat you can look at it everyday in the shed and your body will thank you for it when your older....money well spent.

Bahahahahah. I would - but no.

[scottar]

It will be very boat dependant, the 12x9's I got are almost too active, by that I mean just a touch on the button has a big impact, if fully deplpoyed they wouild stop the boat!

You need more horsepower then;D

[Chimo]

With two motors on the Vag it felt to be affected by slower speeds when in rougher water. Like you I wished the stern to be higher and the nose lower to better penetrate waves.
The foils that were fitted to both motors lifted the stern about an inch or so and after getting used to them being in place Seafarer fitted a set of trim tabs. These even when up and level with the bottom have added to the stern lift. One of the benefits has been a marked reduction in spray blowing into the boat and onto and under the seat which also wet the batteries and oil storage.

The tabs fitted were only 9 by 9 Lencos as that was what was recommended. Playing with them soon after they were fitted it seemed that it would be possible to tip the boat over if only one was dropped. That feeling led me to accept that the size was adequate.

Even with the tabs up and no doubt with the foils in place the motors hardly need to be trimmed in to easily plane the boat.

The bigger tabs will certainly gain greater lift. Would a set of foils on the motor also give benefits? Mine are above the surface of the water when the motors are trimmed out so no extra drag has resulted and the foils do their thing at lower speeds when they add to stern lift.

Its all about trial and hopefully limited error isn't it.

Cheers
Chimo

[scottar]

Permatrim is already fitted Chimo. Took it off briefly after fitting the tabs. Promptly put it back on after the first snotty day. After much experimentation i have found peak low speed economy to be achieved by using tab angle to get the bow down thus allowing the thrust direction to be optimised for forward motion rather than lift. In heavy weather I was regularly running around with full tab down on at least one side. Curiosity got the better of me wondering whether there would be a drag reduction by running a larger plane at less angle
. So far so good.

[Chimo]

With Lencos or Bennetts there is a lot less drag than with the other type.

Peter Webster tested the speed reduction / drag increase on one of his boats with the other type a while ago so you could conclude that lengthening the hull, in this case using trim tabs, has a positive affect once one is moving and less down angle (lift) is needed as speed increases.

Foils do similar but can create drag if you cannot lift them out of the water by trimming the motor back as speed increases. Another reason to have motors as high as possible.

I set up an Al 5.6 m boat I had years ago so that it would turn hard at speed when water skiing in fresh water but if you did the same turns in salt the prop would ventilate / cavitate as the boat sat that much higher in the salt water.

[Moejoes]

Yeah, try pulling the anchor up first next time Crunchy ;D


You need more horsepower then;D

[Moejoes]

Mate, I don't want a cat sitting in my garage doing nothing and looking at it all day long?
The other week I was in a crappy head sea and thought "Thank Christ I don't own a cat!!!!" and wish you were in it with me :P
Yes, all boats have good and bad and maybe my next boat will be a cat - well, one day if I can ever sell mine ( Or give it away ) when I decide to depart with it :-[
.


I know how to fix your problems Scottar & Moejoes...just buy a Cat..i know deep down you both want one..and you wont need trim tabs!...just think of all that money your wasting on your overseas holiDAYS (yes 2 planned & payed for with banana ,moejoes)...I hope you don't get dementia rob and forget your adventures with banana after outlaying all that money...on the other hand if you buy a cat you can look at it everyday in the shed and your body will thank you for it when your older....money well spent.

[Moejoes]

Oh no Tony,
I want to do Miami Boat Show.
Coming?

Jason would rather sit in his shed and look at his pussy all day long ;D


When I heard you guys were off to the US, I assumed you were taking Moejoes down to the Fort Lauderdale boat show to pick up a cat cause he loves yours so much:smitten:

[MyWay]

Since I purchased my rig (Seafarer Victory wit E-Tec 200HO) I have been constantly tinkering to modify some of the handling traits that have been induced primarily by transom weight. Modifications to date have included various prop trials, the trialing of various foils and the fitment of trim tabs. The end game has been to increase hull efficiency at slow planing speeds and thus reduce fuel consumption when offshore and the going gets "tough" so to speak.

The latest "addition" has been to fit extra plates under the trim tabs to increase their size from 12x9's to 12x12's. This has also reduced the amount of distance the front edge of the tab is mounted above the transom when fully retracted to almost nothing. While I have only done one trip, results thus far are encouraging with the following traits noticed -

- less tab angle required to achieve a level plane
- A slower achievable planing speed
- A slight increase in fuel economy when running slow - Last weekends fuel consumption for a trip I have done a few times now was down from typically 100 litres to 90 and conditions offshore were rougher than I would normally fish.
- For the first time ever, the necessary reduction of tab angle for running in a following sea. It was a bit rougher on Saturday but it was the first time I have had the boat "steered" by a wave even running with near full tabs down.

Apart from the following sea experience, which was easily rectified, at this stage I would say it has been a positive result and is swaying my opinion towards "bigger is better" when it comes to tabs.

can you please take some photos

I had the same idea for a long time now but can't make my mind up on how to fix the bigger plate to the existing plates
do i weld it on or to bolt it on

[scottar]

Am away from the boat for a bit MyWay. A mate knocked the plates up for me out of some 5mm aluminium he had laying around from the last boat he built. I have utilized the existing actuator bolt holes and drilled a couple of new holes about 15mm from the leading edge corners of the existing planes and used countersunk head metal threads and nylocks. Only thing you need to make sure of is that the added plate is not so far forward that it fouls the transom at full tab down. Apart from getting the plates in alloy at the right price I didn't want to attach them permanently - at least not initially - just in case it was a brain explosion rather than a brainwave so to speak.

[Crunchy]

Yeah, try pulling the anchor up first next time Crunchy ;D

Perhaps you should have mentioned that a few months ago, would have saved me $1200 on a new winch motor, chain and rope!

[juggernaut]

I did a similar mod to the Bennett tabs on my cruiser, albeit on a bigger scale - from 26 x 12's to 28 X 15.5s. I also had the plates bent up with 3 inch drop fins, just like the Bennett aftermarket bolt ons. I had the larger plates stitch welded to the existing tabs.

The difference is naturally most obvious at slower speeds and can now semi-plane down to 12 knots with the tabs fully dug in and despite this fuel economy has improved at these speeds as the boat isn't plowing. I also run the Mente Marine auto trim tab controller for tab automation which shows the new tabs are generally fully retracted at normal planing speeds.

A pic and plans of my tab mods showing the sizing and features. The larger tab plates were sized according to the Bennett recommendations for heavy arsed boats.

[gofishin]

If you 'got the alloy plates at the right price' scotty, get another set and have them turned down at the sides like juggernaut has done, as you will get better results again - greater lift again and not at the expense of the drag as would be found from flat plates.

Minn Kotas tab plates are like this, albeit with a centre 'bulb' as well for even more lift (from greater surface area generating more lift). Awesome performance, really stoked with mine over the last ~9 years (soon anyway).

Just make sure oldmate uses a decent bend radius when he turns the sides down though in 5mm, else if too tight your side drop fins may break off one day [emoji16]. 3mm ss would give better results I reckon, but turn up the trailing edge for better lateral stiffness/strength (like juggernaut has done). Happy days [emoji16][emoji6].
Cheers
Brendon



Sent from my iPad using Ausfish mobile app (http://r.tapatalk.com/byo?rid=91595)

[scottar]

If you 'got the alloy plates at the right price' scotty, get another set and have them turned down at the sides like juggernaut has done, as you will get better results again - greater lift again and not at the expense of the drag as would be found from flat plates.

Minn Kotas tab plates are like this, albeit with a centre 'bulb' as well for even more lift (from greater surface area generating more lift). Awesome performance, really stoked with mine over the last ~9 years (soon anyway).

Just make sure oldmate uses a decent bend radius when he turns the sides down though in 5mm, else if too tight your side drop fins may break off one day [emoji16]. 3mm ss would give better results I reckon, but turn up the trailing edge for better lateral stiffness/strength (like juggernaut has done). Happy days [emoji16][emoji6].
Cheers
Brendon



Sent from my iPad using Ausfish mobile app (http://r.tapatalk.com/byo?rid=91595)



I did think about it Brendon but as the Victory's transom is not square to the water flow and I couldn't be bothered fabricating mounting wedges to rectify it, decided not to bother. Not sure how much drag they would generate but it would have to be some.

116051

[gofishin]

Yeah ok didn't realise the Victory transom was not square, the fins would also give you extra steering then too... maybe not so good [emoji16].


Sent from my iPad using Ausfish forums

[juggernaut]

It may not be apparent, but the transom is not square on my boat either. Bennett supplied the tabs to the original boat (SeaRay) and are in the shape of a paralellogram. The original tabs had a bent down fin on the outer and a turned up fin on the inner. The larger tab mods by myself followed the original parallellogram shape with added 3 inch drop fins. The drop fins also keep the boat tracking straighter at slower speeds too. Tom McGow (Bennett) chimed in on the trim tab mod threads on clubsearay.com.au. which is where i gathered most of my data before spec'ing my own tabs. IIRC the drops fins are akin to going from a 9 inch chord to a 12 inch chord tab. He also mentioned the drop fins have the biggest effect on smaller tabs and tabs with longer chords.

Tom (Bennett) doesn't condone the use of tabs with greater than a 12 inch chord due to the stress placed on the single actuator setups principally when backing down and building up pressure on the top of the tab and snapping the actuator shaft. For this reason he recommended going a wider tab rather than a tab with a chord longer than 12 inches. Although I saw some of the mods where 18 inch (and larger) chord tabs mods were used without issue. In any case, the auto trim tab controller I have auto retracts the tabs when off the plane so they are fully retracted when I reverse into the pen or backing up when anchoring thereby overcoming the potential issue.

[Smithy]

Fadil, I did that on my boat after your suggestion a while ago. We just through bolted in four places and a bit of SS plate. I ended up tearing them off backing up on marlin though so am just back at standard 12"x12" Bennets!