420/44 DB Owners Club

boaterholic said:
When you say it’s a matter of getting extra power to operate them what did you mean?
I ask because I’m getting ready to increase size if my tabs by attaching larger plates to my factory tabs. They will be 2” wider (side to side)and 3 1/2” longer, or 26” x 15 1/2”. They have 2” drop fins. Another member said they made same size add on plate and still worked with the original single cylinder.
Click to expand...

I gave Bennett the size of your tabs as those dimensions are not far off mine and this is what they came back with:

“26 x 16 is WELL OUTSIDE of the capabilities of the CLASSIC HYDRAULIC trim tab system you are working with, so that is most likely the issue in your case.”

They are saying I should add a 3rd Actuator per Tab !! … Yes, seriously

I’m still in discussion with them….
 
It would be fun to know the actual dynamic load on those tabs in a 30,000 Lb boat at 30 knots. I can totally see where 3 actuators would be required as well as a much larger reservoir for the fluid than what a standard Bennett pump comes with.
 
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Carpediem44DB said:
It would be fun to know the actual dynamic load on those tabs in a 30,000 Lb boat at 30 knots. I can totally see where 3 actuators would be required as well as a much larger reservoir for the fluid than what a standard Bennett pump comes with.
Click to expand...

Surprise for me is a 30% bigger tab requires 300% more power …
 
Carpediem44DB said:
It would be fun to know the actual dynamic load on those tabs in a 30,000 Lb boat at 30 knots. I can totally see where 3 actuators would be required as well as a much larger reservoir for the fluid than what a standard Bennett pump comes with.
Click to expand...
It could be roughly calculated with some assumptions. The weight of the boat would be irrelevant. Use a constant speed. Should be a basic drag calculation with angle of attack...one force backwards, one up...then some trig to determine the force along the line of action of the actuator.
 
AEO said:
Surprise for me is a 30% bigger tab requires 300% more power …
Click to expand...
Sounds like a lot. For a constant speed, the increase in force should be directly proportional to the surface area (and the square of velocity)...if I remember well, which I may not!
 
AEO said:
When underway the tabs won’t go down past 50% - If you put them full down they will stay there but the problem arises once you start operating them. I added an extra ram but same result so we are looking at increasing the power. Bigger pump perhaps? Someone mentioned a second pump but in hindsight that does sound a little weird.

I have the Bennett automatic levelling system with indicators.

Bennett say rule of thumb is 1” width for each foot of boat but as you can see from the pic there isn’t a lot of room. They say it’s better to be wider than longer because the water escapes (the fins may help there).

Please let me know your thoughts and advice as I’m really at a loss to know where to go from here ….


View attachment 125066
Click to expand...
They look similar width. I’ll try getting picture up.
 
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boaterholic said:
They look similar width. I’ll try getting picture up.
Click to expand...
9F481973-BF27-4984-A369-592CB07A062E.jpeg
26819EE8-33DC-4D7B-A3F0-0267F9143E93.jpeg
 
AEO said:
I gave Bennett the size of your tabs as those dimensions are not far off mine and this is what they came back with:

“26 x 16 is WELL OUTSIDE of the capabilities of the CLASSIC HYDRAULIC trim tab system you are working with, so that is most likely the issue in your case.”

They are saying I should add a 3rd Actuator per Tab !! … Yes, seriously

I’m still in discussion with them….
Click to expand...
Interesting they are telling you to add a third actuator and mine seems to be working with a single.
 
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I just spoke with Grayson(spelling?) at tech support for Bennett. I asked him how many actuators on the classic 30 x 12. Told me single actuator, I think up to the 36 x 12. Then I asked him if I removed the 24x12 could I use the same single actuator on a 30x12. He said same actuator and same pump and reservoir.
That said I believe I should be ok for my custom sized add ons. Worst case scenario if too much as is I can start by cutting off the drop fins and if still too much I’ll remove the added plates and fill the holes with the removed bolts used to hold the plates together.
 
It seems like the actuator angle is off. If the cylinder was pushing down on the tab instead of pushing outward on the tab it would have more down force. A longer cylinder mounted higher on the transom seems more afective.
 
boaterholic said:
I just spoke with Grayson(spelling?) at tech support for Bennett. I asked him how many actuators on the classic 30 x 12. Told me single actuator, I think up to the 36 x 12. Then I asked him if I removed the 24x12 could I use the same single actuator on a 30x12. He said same actuator and same pump and reservoir.
That said I believe I should be ok for my custom sized add ons. Worst case scenario if too much as is I can start by cutting off the drop fins and if still too much I’ll remove the added plates and fill the holes with the removed bolts used to hold the plates together.
Click to expand...


boaterholic said:
I just spoke with Grayson(spelling?) at tech support for Bennett. I asked him how many actuators on the classic 30 x 12. Told me single actuator, I think up to the 36 x 12. Then I asked him if I removed the 24x12 could I use the same single actuator on a 30x12. He said same actuator and same pump and reservoir.
That said I believe I should be ok for my custom sized add ons. Worst case scenario if too much as is I can start by cutting off the drop fins and if still too much I’ll remove the added plates and fill the holes with the removed bolts used to hold the plates together.
Click to expand...

Interesting that he is contradicting the Yamaha-Motor Bennet Client Services guy (an M.J Thomas). I don’t want to start making my tab smaller again so I’m stuck with their advice…

Because the info and experiences amongst us is so varying I might consider a third actuator. I am reluctant to bore any more holes in my transom (up, down or otherwise). However my hand may be forced.

I haven’t moved my actuators from the Searay factory install as I’m sure all the contributors here haven’t either so moving them higher seems futile - And that’d be 4 more holes …

Mr Thomas has asked me to call him which I’ll will. I’ll keep you posted..
 
AEO said:
Very similar width. I spoke with the guy who modified mine and it looks like they may have added 4” to the chord (fwd-aft) only. That would make them 24 x 16.

Reading between the lines with everyones comments and experiences it appears changes to the chord are the problem. Span not so much.
Click to expand...

AEO,

I don't know how much, if any I can be of assistance as I have a 48DA that weighs in at 40k lbs in the slings at winter haul out after we unload our stuff but still have full fuel. Three years ago I added 3" to the cord along with 3" drop fins to both of the tabs. (The 48DA comes standard with twin cylinders.) Prior to making these mods any attempt to change to running attitude via trimming the tabs was futile. After the mods I can actually lower the bow to an uncomfortable place if I'm not careful. I believe the most worthwhile part of the mod for me was adding the drop fins in that they now direct the water instead of just letting it splay off to the sides.

Not a good pic, but I'm sure you get the idea. (It was dark in the storage building when I stopped to take it for you.)
IMG_3306.jpeg

Hope this helps, and best wishes finding a solution.

-Tom
 
Mark.60 said:
It seems like the actuator angle is off. If the cylinder was pushing down on the tab instead of pushing outward on the tab it would have more down force. A longer cylinder mounted higher on the transom seems more afective.
Click to expand...
If you’re posting this regarding my pictures, mine are working fine. I believe this is the original instal from Sea Ray. They just don’t seem to be large enough so I therefore run more tab down than I think is normal.
 
TNT8808 said:
AEO,

I don't know how much, if any I can be of assistance as I have a 48DA that weighs in at 40k lbs in the slings at winter haul out after we unload our stuff but still have full fuel. Three years ago I added 3" to the cord along with 3" drop fins to both of the tabs. (The 48DA comes standard with twin cylinders.) Prior to making these mods any attempt to change to running attitude via trimming the tabs was futile. After the mods I can actually lower the bow to an uncomfortable place if I'm not careful. I believe the most worthwhile part of the mod for me was adding the drop fins in that they now direct the water instead of just letting it splay off to the sides.

Not a good pic, but I'm sure you get the idea. (It was dark in the storage building when I stopped to take it for you.)
View attachment 125208
Hope this helps, and best wishes finding a solution.

-Tom
Click to expand...
Very interesting how your side fins also slightly come above the plate as well.
 
boaterholic said:
Very interesting how your side fins also slightly come above the plate as well.
Click to expand...

That feature is part of the original design (I assume for strength), and I had the 3" drop fins welded on from there.
 
TNT8808 said:
AEO,

I don't know how much, if any I can be of assistance as I have a 48DA that weighs in at 40k lbs in the slings at winter haul out after we unload our stuff but still have full fuel. Three years ago I added 3" to the cord along with 3" drop fins to both of the tabs. (The 48DA comes standard with twin cylinders.) Prior to making these mods any attempt to change to running attitude via trimming the tabs was futile. After the mods I can actually lower the bow to an uncomfortable place if I'm not careful. I believe the most worthwhile part of the mod for me was adding the drop fins in that they now direct the water instead of just letting it splay off to the sides.

Not a good pic, but I'm sure you get the idea. (It was dark in the storage building when I stopped to take it for you.)
View attachment 125208
Hope this helps, and best wishes finding a solution.

-Tom
Click to expand...

Hi Tom, thanks for the pictures and info. Interesting that you added 3” and they still operated fine. Even with the extended drop fins which I’m assuming would increase pressure slightly more. Mine are only 1” longer in the chord than yours (4” total) and yet they won’t go beyond halfway…

I’m beginning to wonder if my HPU is a little at fault. Although the capital letters in Bennett’s reply to me can’t be ignored.

/// Edited to add: Did you install that second actuator? ///
 
Last edited:
bajturner said:
Sounds like a lot. For a constant speed, the increase in force should be directly proportional to the surface area (and the square of velocity)...if I remember well, which I may not!
Click to expand...
boaterholic said:
I just spoke with Grayson(spelling?) at tech support for Bennett. I asked him how many actuators on the classic 30 x 12. Told me single actuator, I think up to the 36 x 12. Then I asked him if I removed the 24x12 could I use the same single actuator on a 30x12. He said same actuator and same pump and reservoir.
That said I believe I should be ok for my custom sized add ons. Worst case scenario if too much as is I can start by cutting off the drop fins and if still too much I’ll remove the added plates and fill the holes with the removed bolts used to hold the plates together.
Click to expand...

I rang Bennett to talk to Mr Thomas and got Grayson - He is saying I need to install a third actuator too ….

I guess that’s it then, a third actuator it is :-/
 
AEO said:
Hi Tom, thanks for the pictures and info. Interesting that you added 3” and they still operated fine. Even with the extended drop fins which I’m assuming would increase pressure slightly more. Mine are only 1” longer in the chord than yours (4” total) and yet they won’t go beyond halfway…

I’m beginning to wonder if my HPU is a little at fault. Although the capital letters in Bennett’s reply to me can’t be ignored.

/// Edited to add: Did you install that second actuator? ///
Click to expand...

The second actuator was standard on the 48DA.
 
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AEO said:
I rang Bennett to talk to Mr Thomas and got Grayson - He is saying I need to install a third actuator too ….

I guess that’s it then, a third actuator it is :-/
Click to expand...
I’m guessing since you already have two and not working as you need that is why they are saying add a third one.
I’m hoping since my singles worked fine that they still will with the extra added on. Time will tell. Don’t expect to get boat back in water for close to two weeks.
 
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