Trim Tabs Again

[kernr]

Hello All -

A slow day in the NE with it being cold and COVID all around us. So I have been thinking about what I should do with the Trim Tabs on our GB 47 Europa. To be honest I don't often cruise at over 10 knots and usually closer to 8 - 9 knots. At those speeds I would not think they have much of an effect. They continue to be a fouling nightmare as you will see in photos. The Port Tab is not easy to move and I think the hinge might be binding up due to corrosion. I have contacted GB Malaysia and they gave me the following Bennett TT info:

Item No. 21500-038
Item name: Bennett Trim Tab 29" X 15.1/8" GB 47H

After considerable correspondence with Honda - Bennett TT folks they can't seem to find the drawings for this TT. They suggest I take them off and have a local machine shop manufacture new ones. looking closely at them I am not sure they will come off easily and probably have 5200 or equivalent under the mounting plate screws.

What do you think should be done. I guess I would like to keep them on because the boat will get up and go 25 knots with a clean bottom and you definitely need them at that speed. Photos attached. Any suggestions on how to get them off?

 

[ScottC]

Wow - I'm absolutely ASTOUNDED that a GB Europa can get up to 25 knots!!!

I appreciate this is a tough decision! Big investment to preserve and maintain something you never routinely use!

If I were in your shoes, I would consider long-term cruising plans. If they include distances significantly away from shore/harbors, then you might find that someday you will need to rely on the 25 knots to try to outrun bad weather. Unlikely -- but certainly a nice option to have. This, of course, implies that you keep the tabs.

 

[rslifkin]

If you want a permanent (but expensive) solution to the fouling problems, remove the tabs, fill in the recesses and mount new tabs to the transom so they extend past the bottom. Then you won't have the confined pockets to encourage growth, and any that does occur on top of the tabs is out in the open and easy to clean.

Wow - I'm absolutely ASTOUNDED that a GB Europa can get up to 25 knots!!!

The GB 47 is not the old school GB hull, it's pretty much a planing hull. And has more power typically, so it's a faster boat than what most of us think when we hear "Grand Banks".

 

[Keysdisease]

Those are the traditional Bennett "rolled" bottom mount hinges with the retention devices that act as hard stops behind the actuators so the tabs can't be overextended in reverse.
No machine shop anywhere can reproduce that rolled hinge, and it is very reliable and durable, much more so than a piano hinge.
The screws are just self tapping screws. One of them may be a machine screw that goes all the way through and connects the bonding system.
The travel of the actuator is only 2-1/2" so it may not be binding at all, or just work it while installed. Taking the tab off the hinge involves some "persuasion" which may be challenging

Call Bennett and talk to Thomas, send him the photos and take precise measurements. The part number GB gave you sounds correct, and before Yamaha bought Bennett they would make replacement mounts no problem.

I have seem Propspeed and equivalents work well on trim tabs for fouling

 

[kernr]

TT Again

ScottC - Yep saw it with my own eyes - Sea Trials in Feb 2020 when we bought her. The TT worked great and from a later trial she squatted down aft w/o TTs and we did only 22Knots. So the TTs are worth three knots at the top end. The CAT C9s love to get up on their superchargers but the problem is the diesel fuel burn rate at about 50 Gallons an hour.

In general, I agree with you to keep them on.

Keysdisease - I have been talking with Thomas for about two months now but their engineering department is unable to come up with the drawings and I gave them all the info from GB Malaysia. He was the person that suggested I go local to have them made. he is taking a look at the obsolete file to see if he can locate them. Our boat is Hull # 50 so they made over 100 back in 2007 / 2008 - not sure when they changed from our hull design to the next one but she is pretty flat back aft - thus speed capability.

Bob

 

[HeadedToTexas]

My boat rarely goes over 9 knots and typically only 7 knots. At that speed, do you guys really fiddle with trim tabs? I would be tempted to remove them and all the complexity involved (including helm space) if that wasn’t so expensive. Mine are essentially abandoned in place.

 

[rslifkin]

My boat rarely goes over 9 knots and typically only 7 knots. At that speed, do you guys really fiddle with trim tabs? I would be tempted to remove them and all the complexity involved (including helm space) if that wasn’t so expensive. Mine are essentially abandoned in place.

I should probably experiment to see if they do anything beneficial at slow cruise (6.5 - 7 kts for us). Normally when we're running at that speed they're just left fully retracted. But we do sometimes get up and run, and at least on my boat, the tabs are very necessary when running up on plane.

 

[Seevee]

I could make an argument to support rslifkin's idea. Spend the buck and put a new system on.

Have you priced this option? Kits are in the $1000 range, and guessing on install.... $500 to $800? Haul $500? So, ball park, you'd have new tabs in the $2500 range. Absolutely, do it.



It could be cost effective instead of special machining and futzing with an old system to repair it.


And, Bennett is a great company to deal with.


And, spend more time on plane using them. Just curious, wonder what the fuel burn would be if you're just barely a bit over planning speed... perhaps 16 knots? Might be reasonable.

 

[Nomad Willy]

Trim tabs need’nt be mentioned on trawler forum.

 

[HeadedToTexas]

That’s my experience too.

 

[Keysdisease]

As GB was supportive with the part number, perhaps they could supply a drawing of the Trim Tabs from Bennett. They would have had to sign off on them before ordering. If they supply drawing to you and you to Bennett then they should be able to make replacements.

Still not sure you need replacements, those look in pretty good shape to me from just the pictures.

Seems when Yamaha bought Bennett some things fell through the cracks in transition.

Keysdisease - I have been talking with Thomas for about two months now but their engineering department is unable to come up with the drawings and I gave them all the info from GB Malaysia. He was the person that suggested I go local to have them made. he is taking a look at the obsolete file to see if he can locate them. Our boat is Hull # 50 so they made over 100 back in 2007 / 2008 - not sure when they changed from our hull design to the next one but she is pretty flat back aft - thus speed capability.
Bob

 

[kernr]

TT Again

Keysdisease -

I have learned a lot in the past few days about Trim Tabs and how they operate. You specifically have been very helpful - thank you. The other help I received came from Nazri Abu at Grand Banks Malaysia - he promptly responded to me with all of the information they have on the Bennett Trim Tabs installed on the GB 47 Europa - See attached. So, I place them here so others can understand the configuration.

Thanks,
Bob

 

[Keysdisease]

Excellent, file for future reference, maybe send to Bennett just to confirm this is adequate to fabricate you new units when/if necessary.

You do need to confirm the drawing is what you have. Parallelograms are common custom tabs, but you do need to double check while you can

Tell Thomas I said hello