Need some trim tab location help

[xo4001]

Hi all
Try to find out what is the best location for the tabs
Since I have limited space to mount them
I have the st 12 want to fit them with only one hydraulic cylinder
Moved the cylinder already to the far outside to make the foot land on the transom
Doin't know if this is a good thing?
Still the tab go's over the chine about 3''!!
Want to get some ideas what the possibility's are

http://i774.photobucket.com/albums/yy27 ... CN0264.jpg

http://i774.photobucket.com/albums/yy27 ... CN0262.jpg

http://i774.photobucket.com/albums/yy27 ... CN0261.jpg

http://i774.photobucket.com/albums/yy27 ... CN0265.jpg

Thanks

[seabob4]

Martin,
From your pics, it is kinda hard to tell what I'm looking at.  Does your transom angle forward just before the bracket (I assume it's a bracket)?  A shot of the whole back end would help.

[seabob4]

Makes it a little easier on all of us...

[Capt. Bob]

This is the 240 with the recessed transom.
viewtopic.php?p=31996#p31996

The tabs ought to be quite interesting.

[xo4001]

Martin,
From your pics, it is kinda hard to tell what I'm looking at.  Does your transom angle forward just before the bracket (I assume it's a bracket)?  A shot of the whole back end would help.

Yes bob the little part where the tab go angle forward
Will take larger shot tomorrow
For now maybe this will do


And thanks for letting the pictures show

[seabob4]

Oh man, Martin, that IS a challenge!  I wouldn't recommend offsetting the actuators as I would think Bennett would want the force exerted by the actuators to be centered on the tab.  I shall email tabman and get his input on this one...

[Aswaff400]

we have a couple boats in the marina that have the actuators offset due to hull shape, swim platform, or twin motors wouldnt allow clearance to fit in the center so i would think it should be ok...

[seabob4]

I see Tom has shown up, I want to read his recommendations.  In reading the install manual, we note that the recommended distance inboard from the chine is 3"-4"...http://www.bennetttrimtabs.com/pdf/inst ... lation.pdf

[Tabman]

Martin,

I take it you already have the ST12s.  If we were starting from scratch the M120s 10" side to side x 12" fore to aft would fit better.

OK, with the ST12, while we really don't recommend offsetting the actuator, those Tabs are quite ridged, so you should be OK.

The location is OK, but it is a bit too far outboard and will make some spray and the outboard side of the Tab will be running in aerated water flow and won't be as effective as it would if it started where the chine flat ends.

The mounting plates will probably be OK where the "run off" the transom on the inboard side, just a little funny looking.

This is why the narrower span M120 would be a good choice.

But the big issue is the forward angle of the mounting point!  It really needs to be perpendicular to the center-line of the hull.  The Trim Tabs will be toed out and make a lot of spray and ventilate the underside of the Trim Plane greatly decreasing their lift if they are mounted that way.

They will need to be shimmed so they a square with the center-line to work.

Tom
Bennett Marine

[xo4001]

Martin,

I take it you already have the ST12s.  If we were starting from scratch the M120s 10" side to side x 12" fore to aft would fit better.

OK, with the ST12, while we really don't recommend offsetting the actuator, those Tabs are quite ridged, so you should be OK.

The location is OK, but it is a bit too far outboard and will make some spray and the outboard side of the Tab will be running in aerated water flow and won't be as effective as it would if it started where the chine flat ends.

The mounting plates will probably be OK where the "run off" the transom on the inboard side, just a little funny looking.

This is why the narrower span M120 would be a good choice.

But the big issue is the forward angle of the mounting point!  It really needs to be perpendicular to the center-line of the hull.  The Trim Tabs will be toed out and make a lot of spray and ventilate the underside of the Trim Plane greatly decreasing their lift if they are mounted that way.

They will need to be shimmed so they a square with the center-line to work.

Tom
Bennett Marine

Tom,
Thanks for your advise
I will take it seriously
Will think about the material to make the shim and then I can move it inward also a bit
What would be the (realistically) distance that the tab need to be from the chine

Best
Martin

[Tabman]

Martin,

The best would be if the outboard edge of the Trim Tab was right where the Chine Flat ends and the Vee of the deadrise starts.

Tom
Bennett Marine

[love2fish]

While you are in the rebuild/construction phase now, why not do a little glass work and make a bigger area to mount the tab? You could "easily" extend that bumped out area of each side of the transom to accomodate the tab hinge. Then the actuator could be mounted in the correct spot.
Or if yiu have access to it, you could build a shim/pad outbof starboard to allow proper placement/alignment.

[Capt. Bob]

Might be a little reluctant to mess up that new blue paint.

[love2fish]

Good point Bob! Sorry, i was reading this on my phone at lunch and didnt realize the Blue boat pics were his boat.

[xo4001]

Tom,

I think I have to make a choice between two bad

 

This is the position starting at the chine going down with a proper shim as you recomended
Now I have the actuator all the way to the edge
Was thinking if I make the bottom of the tab not in line withe bottom of the boat
Say make the inboard side of the tab a little higher from the bottom that will turn my actuator more to the outside and give me maybe the possibility to bring the actuator more to the center
So the big question is,is this a good option and if so how much can this be ofset
Or shall I just average my tab between where I can fit it a litle over the chine
I think this transom is not designed for tabs