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!!!!!!!!!
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
Cheers Rob

[scottar]

Hi Scottar,
Not that I'm any expert, which I'm sure one of those stalkers will surely comment on soooooonnnnnnnnn!!!!!!!!!
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
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

[Moejoes]

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

No seriously Scottar, listen to Moejoes cause he knows

[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

[Moejoes]

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

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

[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

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

[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.