I have screw heads underneath my trim tabs, normal? (see pics)

[PhatboyC]

One thing I feel kind of odd on my Lenco trim tabs is the regular screw heads protruding underneath the tabs. Seems to create drag where there shouldn't be. I know, I know, not allot but still, why? I am thinking of simply changing to SS bolts with a flat head instead. Thats what they should have at least. I'm sure I can find some. Everyone with a Lenco setup has this?

My boat's Lenco's trim tabs:

Just to compare, same boat model but with Bennett trim tabs. The rear panel has a 90 degree bend. Different but at least no drag. On the other hand I don't like the side fins:

 

[Chris1956]

Re: I have screw heads underneath my trim tabs, normal? (see pics)

Phat, Yeah they will cause some small drag (they are pretty well hydronamic, BTW), but using your trim tabs ( with or without screw heads) will cause a whole lot more drag, especially when it pushes the stern up and the bow down.

 

[PhatboyC]

Re: I have screw heads underneath my trim tabs, normal? (see pics)

True.

It's when there are fully retracted and flush to the hull it bugs me. But your right, the head are somewhat aerodynamic. Come to think of it, when looking at the first picture it doesn't seem like the tab is flush with the bottom of the hull. Looks like there will always be in a down angle. Man I hope they didn't mess up the installation...!

 

[ziggy]

Re: I have screw heads underneath my trim tabs, normal? (see pics)

I know, I know, not allot but still, why?

what ya have look like ss pan head bolts.
your wanting to go to flathead it sounds like, so they're flush with the bottom of the tab. the reason i think they didn't do that from square one is cause the thickness of the tab won't allow ya to countersink the flathead screw far enough. basicly the taper of the flathead screw starts to contact the bottom of the mounting plate thereby leaveing the flathead screw slightly above flush. i suppose ya could countersink the mounting tab to allow for it. but that'd be my guess as to why.

i can't really think thems screw heads are gonna make any difference one way or the other regaurding anything on a 24' boat......that'd be my take from someone who don't have any tabs at all........

last note, in the industry i work in i use flathead screws to sometimes as fasteners of thin metals......the answer is undercut flathead screws. basicly the taper of the flathead screw is cutdown to the same diameter of the screw. lets it sit flush. problem with this is ya have to have a pretty big hole countersunk to get it flush....

 

[jeffnick]

Re: I have screw heads underneath my trim tabs, normal? (see pics)

Lenco

Bennett M-80 Sport Tab

The Bennetts are riveted, for less protrusion on the underside of the tab, but I'm not sure the difference is significant.

If you don't like the shape of the Bennetts, it's probably because you've never used them.

 

[Frank Acampora]

Re: I have screw heads underneath my trim tabs, normal? (see pics)

If they really bother you, try buttonhead ss. these have an elliptical head, not much higher than the pan heads, and lower than round heads, tapering to nothing at the perimeter--a little more aero/hydrodynamic. They are tightened with allen wrenches. You can find them at Fastenal stores.

They will look a little nicer, but personally, I don't think there will be any difference in performance. your depth finder transducer has more drag than either sets of screws.

 

[h2oboy]

Re: I have screw heads underneath my trim tabs, normal? (see pics)

Coming from a dragboat background, if you were looking to gain that extra edge it might make a difference in the 1/4 mile, but it is a lake boat. 6 screws really are not going to drop your mph at all or effect your ride.

 

[QC]

Re: I have screw heads underneath my trim tabs, normal? (see pics)

It's when there are fully retracted and flush to the hull it bugs me.

Actually they should be a few degrees up, and not "flush", when fully retracted. Check with a straight edge . . .

 

[PhatboyC]

Re: I have screw heads underneath my trim tabs, normal? (see pics)

Actually they should be a few degrees up, and not "flush", when fully retracted. Check with a straight edge . . .

Then I'm definitely worried now. Anyone that has Lencos; by looking at the ss shaft would you say there are all the way retracted already? Or do I have more play and the ss shaft goes in a bit more to hide the last inch or so showing? The boat is in shrinkwrap so I can't test it.

 

[QC]

Re: I have screw heads underneath my trim tabs, normal? (see pics)

I don't know if they are fully retracted as I don't have Lencos. I have installed a set before, but don't recall. IMHO, if they are fully retracted then Doral (I assume they mounted them) has messed up . . . If you look at pic 3 in your first post, they should be slightly inboard like that so that the upper mount of the cylinder can be higher. Yes, tabs should be mounted as far outboard as you can get, buuuuuuut they also need to be able to get completely out of the way, for a variety of reasons. One example is that if the boat is heavily loaded in the bow you want to get them all of the way up to negate any additional downward force. Also, it can be important for beaching and on some trailers . . . The fact is that there is additional drag caused by tabs anytime they are in a "positive" position. That doesn't mean that they are slowing a boat down though as they may also allow you higher trim settings which in turn is faster. Yes, some drag from the tabs, but the combo ends up faster, so who gives a flyin' flip . . .

 

[jeffnick]

Re: I have screw heads underneath my trim tabs, normal? (see pics)

Fully retracted Lencos:

 

[PhatboyC]

Re: I have screw heads underneath my trim tabs, normal? (see pics)

Thanks for the pics Jeffnick. Your spacing is the same as mine right now. That means I have a problem. They where installed at the Doral dealer. But I still see two problems with this; one it is 3 hours away and second I don't want more holes in my new hull.

I wonder if I can remove the ss horizontal plate from the hinge like you can with a door? If so I can just get them to ship me new plates with the 3 holes all the way at the end. Or a longer plate. This would allow for the shaft to have to reach further, hence lifting the angle on the plate.

 

[Dhadley]

Re: I have screw heads underneath my trim tabs, normal? (see pics)

This is what drives me nuts about trim tab installations. They are not supposed to be flush with the bottom. They are supposed to be mounted up at least a 1/4". Otherwise you can never get them out of the water. IE - they're always affecting the attitude of the hull.

In my opinion the best option is the recessed tabs. When they're fully up they become part of the hull. Nothing behind the transom. Gotta love a Hewes.

 

[QC]

Re: I have screw heads underneath my trim tabs, normal? (see pics)

Even if the hinge doesn't come apart, you could reninstall the whole plate without much hassle, pain etc. Pretty simple just put some 5200 Sealant or similar on the threads when you go back together.

Here is Lenco's manual: 'http://lencomarine.com/trolln_tabs_pgs/tnt_pre_d_archives/Resources/OwnersManual207.pdf'

If the dealer gives you any BS, read them Page 8 #3. It says the trailing edge needs to be 5/8 inch above the hull . . .

 

[PhatboyC]

Re: I have screw heads underneath my trim tabs, normal? (see pics)

3 weeks ago I purchase a used snowmobile so I can get to the boat at the cottage to clean the snow off the shrink rap. Ok ok not really the only reason I bough the snowmobile for.

Last time I was at the cottage I finally got around to taking more pictures of my improperly installed trim tabs. So I can send to the Doral dealer. I am in no rush since I'm still having fun with all the snow we had.

I called Lenco to confirm my options to correct my situation. I want to remove my negative angle for a positive one. Or at the very least flush. I though I could install longer ones 12"x12" to replace my 9"x12". But the rep said the distance of the holes in the bottom mount would be the same. They simply extended the tab 3" longer not the mount point. So the only option I have is to install what they call their edge mount tab. The bottom mount sits at the edge of the tab. Same as what jeffnick has posted above. I still have to see which one I need either the 9"x12" edge mount or the 12"x12" edge mount.

But before I go further, I would like your advice if I should go through this or leave it be. With the new pics I took do you think it will affect my ride right now?

 

[jeffnick]

Re: I have screw heads underneath my trim tabs, normal? (see pics)

I'm no expert, but I'd think you might lose a tiny bit of top end.

If the hole pattern on the transom is the same for the replacement (edgemount) tabs, I'd do the swap if they'd supply the tabs. Otherwise, I'd be inclined to wait and see if it still bothered me at the end of next season.

 

[ziggy]

Re: I have screw heads underneath my trim tabs, normal? (see pics)

I'm no expert, but I'd think you might lose a tiny bit of top end.

If the hole pattern on the transom is the same for the replacement (edgemount) tabs, I'd do the swap if they'd supply the tabs. Otherwise, I'd be inclined to wait and see if it still bothered me at the end of next season.

that the way i feel about it too. i'd hate the extra holes in my transom more than i'd dislike the tabs being slightly down. unless there's a performance issue or the other design bolts up exactly..... i'd still do the wait and see idea too...

 

[PhatboyC]

Re: I have screw heads underneath my trim tabs, normal? (see pics)

Thanks for your input guys. Yes the bolt pattern is the same with the edge mount.

 

[QC]

Re: I have screw heads underneath my trim tabs, normal? (see pics)

Not to make you feel worse, but they'd bug me, and they will affect performance as is. It is possible the boat balance will like that setting, but if the tabs were right and she porpoised badly with them all the way up, then I'd adjust the balance to get it right. I guess I am saying that I want my boats setup right, and the way I have learned to set my boats up is to get them to just barely porpoise at WOT and full trim with the tabs all of the way up . . . What does Doral say? They can fix this without messing up your transom. Heck they fix hulls with holes as big as basketballs in 'em . . . bigger

 

[Solittle]

Re: I have screw heads underneath my trim tabs, normal? (see pics)

Put a 2x4 or somthing else that has a long strait edge along the bottom of the hull out to the bottom edge of the tab. That will graphically show you how far it is out. Email this to your dealer and ask him what he plans to do.