Bennett tab extension
 

Well, after a lot of investigation and thought, I am going to extend the Bennett tabs on my boat. I have an extra set of tabs, and have stripped the powder coating and will give this template to a local fab shop and have them tig some extra length onto them, Add a few strengthening ribs and should be good to go.
I realize that replacing with K planes would be better, but this is too involved and costly now....maybe later if I see that the improvements in length is worth it. Season is getting too short, and I want to see about how this will work. I really want to get rid of the proposing tendency of the 292. It all goes away at 50mph, but I would like to move the proposing threshold(new term?....like it?) lower. Not sure if this will help, but I am willing to try.
As a reference, these will move to 17.75", or an additional 6.25" and are 12" wide and taper to 10" to assure no issue with drive collision. K-planes are 19.25" long and 9" wide at the tip as a reference. That is too long to extend these, as I worry about the Rams and mounting hardware.

More to come.

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I like your thinking. I have done this and discovered in rough water single Rams won't cut it...the tabs hold up and do a great job until you push them as I did...ripped the single ram to shreds. You need to also increase the number of mounting screws to the transom hinge...another failure point.

I'll try to find a damage pic to show you.

Great point, I also have another set of transom plates. Sounds like I should drill more holes in them and add screws. Also, mine has double Rams....maybe that will help keep them together. Pictures would be great. Thanks

I have a pair of Lenco? tabs (no rams) that are close to 280 K plane dimensions. Mounting is a little sturdier than Bennetts . If you can make these work , just pay shipping from Fla. Good Luck,W. http://i1172.photobucket.com/albums/...psgbzns80c.jpghttp://i1172.photobucket.com/albums/...pspae558ih.jpghttp://i1172.photobucket.com/albums/...psixrv27bb.jpg 941-681-1870

The double ram has a better chance of survival than the single of course. I had a folded single ram at the "hinge" upper mount in my 242SS. Maybe the double can spread enough load to make it work, good luck.

http://www.bennetttrimtabs.com/wp-co...stallation.pdf

Concerned about the mounting screws, Big #10s. K planes are Lagged or through bolted. There is a reason why. Bennett's are sheet metal screwed into the transom. Much less pull on the small tab........until you extend it.

Trim your drives down a little will likely stop the porpoising at lower speeds.

Are saying it is OK to lag bolt K-Planes on? I had thought they were always thru-bolted.

Some manufactures do lag bolt...They should be through bolted because of the load..

When installing K Planes , always drill pilot holes first . Many times , when you position it where it needs to be , you will have a bolt hole going directly in a stringer. You can lag that hole and thru- bolt the rest , unless you already drilled it 1/2"....

On mine I have a flooring (basically) from the top of stringers to the side of boat making access to lower bolts very difficult, it would require cutting an access hole and re glassing so I decided not to go with K-Planes. I wonder how lagging the lowers where there is no access and thru-bolting the uppers, if accessible, would work.

Can you cover hole with 4" deck plate? Gives you inspection access in the future.

I don't understand, why fool with the Bennet tabs? I also don't understand why Formula put them on in the first place. They are a good product but IMO a high performance offshore boat is not the correct application.

I have recently seen some used Dana tabs and pumps advertised in the forums. Get them and be done with it, JMO.

Padraig

lenco upper ram mounts screw in like the bennets..

I have blown the upper mounts off the back of the boat before. I now run k planes.

For god sakes just buy some tabs and enjoy your boat....

I extended my bennetts on my 242. Worked great.

I went from ST-12 to ST-16 Bennet tabs on my 26' Sonic years ago. It was a noticeable difference.

But I also blew out one of the hose fittings inside the bilge on one of my ST-12s before the upgrade. This was on a bit of a rough landing on that side of the boat on a river run.

Your bigger tab is going to put more pressure on your hydraulics system.
The ST-16 comes with a mounting plate with two rows of screws, not just one row like the ST-12s.

Call Bennett directly before you do anything with a fabricator. They set the standard for Customer Service in this industry. They also chime in here on OSO from time to time.

Yeah, what does the boat do without tabs and the drives trimmed a notch or 2 out? Trim in to clear it up.
You do know that Formula sets the spacer in the trim pivot in a + trim out position....

Well, all good advice. I appreciate it.

I called Bennett and talked to one of the tech guys and he said that they sell a 16" tab that uses the same two cylinder design...so the hydraulics are good for the 4" longer tab. He then said that the 16 tabs could be purchased, but the location of the cylinders is a little different, so where they mount to the transom would have to move....he said it would be better to simply weld an extension on the ones I have. Lastly, he wanted to use the transom plate from the 16" tabs, which has double the number of screws, so there is no issues with them pulling out. My goal is not simple, but this will be a fairly quick upgrade. the idea of wiring for two pumps, all new hydraulics etc is a lot...

I am happy with this....as I was almost ready to pull the trigger for a set of Kplanes. While that may still be in the cards for the future, this modification will work.

Thanks for the advice. I will now resize the tabs, order the plates and get on with it.

With the extended tabs you will need indicators, Oh wait, I have a set of New Bennett indicators in the swap shop for $250. Good luck and keep us posted.

Back in the day, it was a simple upgrade for me to go to the ST-16s from the ST-12s. They had the same mounting plate hole location for the transom, (just add more screws), and the mounting point for the twin rams was the same distance from the transom.

It sounds like this had changed a bit.

Just be wary of the additional stress placed on all of the hydraulics inside the system now with the bigger tabs.

The 16" plates simply have two rows of screws and a larger plate.

Is it normal to use 5200 or 4200 to glue the screws in...or some other material? I am pretty sure these is nothing on them now...as I backed them out a little and did not see anything.



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I put mine on with 4200 way back when.

What's nice about the 2-rows of screws on the bigger plate is that the bottom row lines up with the holes from the 1-row of screws on the smaller tabs.
At least it used to.

The new backing plates are here, and the tabs are out to get welded. Total cost will be under $250. I will be able to see if the tabs really make the difference, and then decide if further upgrades are needed. Here is a shot of the new plates. I will install them with some 4200 on the plates and screws...they should hold fine. I will post a picture when the tabs are done and ready to go on the boat. This should happen next week. [ATTACH=CONFIG]558979[/ATTACH]

Tabs are done. I will probably polish them for a little bling. Added 4.5" to them. Wont be on for this weekend, but soon. More to come.[ATTACH=CONFIG]558999[/ATTACH]

Tabs are now done. Double row screws, all joints have 4200 to help keep them in place. They look good. Hope to be able to try them out in a week. Local fab shop did a nice job extending and reinforcing them. [ATTACH=CONFIG]559478[/ATTACH][ATTACH=CONFIG]559479[/ATTACH]

Looks good Kai. I guarantee you'll notice a difference

OK! Found your Tab thread. How did the modified Tabs work? Still have them on?

I'm wanting to start the same project on my ST12s & extend them...
How did yours work & what can you tell me to do or not to do that would help me out?
Thanks