Trim Tabs

[betty boop]

They make a huge difference at slow speed, better handling and less wake, however if I remember correctly doesn't your boat have the large rounded rear that makes fitting them correctly pretty impossible?

yeah spot on - good memory they do 'fit' on but the problem is the dampeners are at too acute an angle to compress and allow the tab to raise under water pressure due to the bulged bum. I think there was enough movement to push them up by hand though. May be a fixed rod not dampener that I could remove with a pin set up may work. Boating will be about 60% river (or going on last year 100% over 3 trips ) so an improvement would be beneficial.

[_Ed_]

Interesting thread this. Pretty much all my thoughts have already been said. The only thing I would probably add is that my Fletcher runs much more level than it seemingly did before. My OH likes them a lot. What I did do however is initially I had the heaver 'black' springs, which I felt were too stiff for the little Fletcher, so when I lost one i replaced them for a lighter kit, and all is well. Not tried to see if I can get faster without them. Its a pain to change in the water. I like the tie up idea above.

Martins graphs got me thinking The speed vs rpm remains the same, as you would expect or you would be seeing a change in prop slip, however the MPG from the graphs seems worse on the tabs than without, except for only one area, around 2000 rpm.

[mlines]

Ed, I interpret that as:

1. At cruising speeds the tabs are slightly increasing drag = lower mpg

2. At 2000 rpm is where we are just coming over the hump so there is an mpg improvement as it is planing earlier compared with pushing the water.

All readings are actual fractions of a litre high or low so to all intents it makes little difference to the fuel, it's just the ride you experience.

Sent from my Nexus 6P using Tapatalk

[BruceK]

Don't use ropes for tying up. Use the PR500 retractor tab. This with a pull on the lever retract them horizontal or with a push drop them to the required 25 degrees



Although I have heard a lot of positive comments which I agree with, the main benefit to these systems keeps getting overlooked. They are dampers, like car shocks. They stop porpoising. Without wanting to raise any heckles, their use in slow speed handling is marginal and their requirement for that is more a reflection on the helmsman than actual worth. Boats dont steer like cars and if you have to drop what is essentially a drogue to steer then you're over compensating on steering.

In addition because they are dampers they will provide only a modicum of lift. for a 20 foot class boat each damper is rated at 25kg for full deflection. That is a 50 kg lift. Hole shot improvement will be marginal and if that is your issue trim tabs would be better because a 50 kg lift when trying to climb a bow wave in a boat is back to moving ballast about.

[Gazjen]

Bruce as much as I respect your thoughts the difference they made on my first Maxum was huge. I wish I could demonstrate them for you. Without them it was pretty much unbearable on the canal/river at 4-6 mph, constantly wandering and no amount of small inputs would make it travel in a straight line, so much so I made a rudder for river use as it got to the point where I just didn't want to drive it. With the tabs it was 90% gone you could actually take your hands off the wheel to fetch the rope or a drink etc. Bow rise was a thing of the past and it also made little difference to hole shot if everyone was sat on the rear seats. I believe the shorter and less powerful the boat the greater the results. I agree they didn't make a huge difference to the GTS20 but that has a 5.7 MPI fitted but it does go from standing start to plane now pretty much instantly

[BruceK]

Interesting and I wonder if that has more to do with the Maxim rather than the benefit of Smart Tabs. My Sea Ray cuddy of old did wander. But not as you describe and to be honest the benefit of smart tabs were marginal. Was your Maxim ballasted correctly? A bow heavy boat will wander more, forcing the bow in will exacerbate this. So harking back to my original post if this was the case you would have a short term benefit to slow speed handling at the price of a greater tendancy to broach during high speed manoeuvres. Do you see where I am going with this?

[Gazjen]

Not sure about the balance of the boat really, but I wouldn't imagine it was out of the ordinary seeing as I experienced wander and bow rise. It's been pretty much the same story for the ones I've fitted for friends too.

[Bigplumbs]

Now I just don't know what to do !

[_Ed_]

Ed, I interpret that as:

1. At cruising speeds the tabs are slightly increasing drag = lower mpg

2. At 2000 rpm is where we are just coming over the hump so there is an mpg improvement as it is planing earlier compared with pushing the water.

All readings are actual fractions of a litre high or low so to all intents it makes little difference to the fuel, it's just the ride you experience.

Sent from my Nexus 6P using Tapatalk

Understood. and also backs up my experience.

[betty boop]

Not sure about the balance of the boat really, but I wouldn't imagine it was out of the ordinary seeing as I experienced wander and bow rise. It's been pretty much the same story for the ones I've fitted for friends too.

blaming the Helm is a bit harsh and its definitely not the case, may be I haven't had too much experience of other vessels other than a 3.5T dual engined stern mounted jet rib but even that wandered in a head on 6-8knt tidal flow on a river, There as even a forum member who wrote that he was worried his non maxum was wandering and at fault. I think you'll find it is a consequence of the stern drive and prop introducing a torque steer effect to the vessel by being off the stern instead of a fixed prop under the hull and a rear rudder. I don't blame you if you disagree as my own father disagrees with his 40 years of marine police & Helm experience but it is written somewhere in the world I just can't point you to where.

As I see it, in my simple terms, in slow speed by adding the Tabs you would effectively be extending the stern to over the prop thus lowering that torque steer effect and at the same time countering any bad weight distribution by stabilising the bow rise/fall etc. Im always heavy in the bow with a dog + bags, in the old days it was kids etc. but she still wandered even empty. So much so that if i do get to remove the wandering Id probably crash straight into the bank as its 2nd nature now to constantly feather left in right on the wheel.

Not sure the cam brackets works or is available as it's fitted to the stainless Mk1 tabs and Im sure they are not for the plastic mk2 but I'll check that one.