How to make wooden trim tabs

[sdowney717]

My old bennet tabs are badly crevice coroded.
I would like to make some out of 3/4 ply or I have some red oak I can use.
How would you go about making the hinge where it meets the transom?
thanks for some ideas. I was wondering about a rubber hinge screwed into the back of the transom and then screwed into the wood. Or does anyone have another idea for a hinge, perhaps using something fairly common.

[pcford]

My old bennet tabs are badly crevice coroded.
I would like to make some out of 3/4 ply or I have some red oak I can use.
How would you go about making the hinge where it meets the transom?
thanks for some ideas. I was wondering about a rubber hinge screwed into the back of the transom and then screwed into the wood. Or does anyone have another idea for a hinge, perhaps using something fairly common.

You should fix your power tabs.

If for some reason you can not do this, in the old days a "shingle" was applied which was a wedge about 1/2 inch thick tapering out to nothing about 18" forward of transom.

[sdowney717]

I really dont like the wedge idea.
I do like the idea of adjustable tabs.
I called Hampton rubber, they sell sheet rubber reinforced with fabric by the square foot at a reasonable price.
2 strips 1/4 " by 6" by 4 foot is 15$ comes off a giant roll. So I could screw the rubber into the transom with a backing piece, then attach 2 3/4 plywood board to the rubber perhaps like a sandwitch. (rubber in the middle). Put a short piece along the back edge for support.
My current tabs are 9 inchs wide and 4 foot long. I am thinking I would like 12 inch wide. Would wider tabs give a longer water line length? What is the effect of wider tabs?

[Gary E]

Go to a Sheetmetal Shop and FIX what you have, what you are proposing is a cobbled together idea that is garanteed to fail as soon as the first wave falls on them when you pull the throttle back, if not sooner in a following sea.

And wether you like the wedges or not, they DO WORK. and are never busted off from following seas and the pilings you will back into.

[sdowney717]

I have a thick fat 2 inch thick teak swim platform that overextends the tabs by quite a bit.
backing in would hit the platform. I actually rebuilt the edge of the platform and have a black thick rubber vinyl strip I could reaatach to the swim platform, should I reattach this, or just leave the wood edge bare?

How much force do you think 2 layers of 3/4 inch plywood screwed togeher can handle? With the fabric reinforced rubber hinge, I dont think this would rip out. I dont really know unless I try.
The black plastic benet cylinders look to me the weakest link in the system.

The current tabs are SS and are channeled out crevice coroded, probably still functional but who knows. I just dont like SS in the water, the zincs dont last, the steel just dissolves.

[Gary E]

I am guessing that you ought to put the rubber bummber back on if you fear backing into a piling, I did one time on purpose but I dont have tabs or a swim platform.

As for is your idea strong enough? Who knows... maybe the Shaddow :)
I still think that a Sheetmetal shop can fix your Tabs for less than your gona spend on a cobbled together idea. And as for the zincs disolving, or the SS disolving that indicates other problems, dont blame the tabs, they have been around for 40 yrs or more.

Sounds like your getting closer to being finished?

[rbgarr]

Is your trim tab system connected by a conductor to your bonding system, if any? It shouldn't be. That could be contributing to the hinge problem.
Or perhaps you've got erosion instead of corrosion problem. Are the forward edges of the tabs (where the hinges are) mounted below the transom edge so they are in the flow of water? They should be mounted about an eighth of an inch above the flow at the hinge.

Re making the tabs 12'' vs 9": You might ask Bennett about doing that. 4'x9"=3 square feet per tab while 4'x 12"= 4 square feet per tab, so your increasing the potential thrust by more than 30%. It would certainly void any warranty on your system if that still applies, and might just bust your cylinders anyway.

[sdowney717]

these tabs attach right on the bottom boards and there is no appreciable lip to speak of. They are really guite simple design, a sheetmetal shop could easily bend new ones, but I think the material cost of the SS would be high. I would prefer 1/8 inch copper sheeting.

Yes, the boat would actually float now. I am almost done. I am working now on the keel bottom.
I need to paint the hull, the bottom is finished!
Looks good, the marina owner was so impressed I saw it thru. Most people he said would have given up. I am looking to go back in in the next 2 months.

[sdowney717]

these tabs are not bonded. They have a zinc you attach to protect, but see they are from 1970 so, the years have gotten to them.

[Gary E]

Copper is much top weak, and SS does not really cost all that much and SS will cost a lot less than anything copper...
Go visit a Sheetmetal Shop

Glad your almost floatin, bet you are too :)

[rbgarr]

I'm pretty sure the zincs on the trim tabs are unnecessary, but I see that the Bennett website suggests them ("you may need them") and perhaps bonding to prevent 'electrolytic corrosion' (there's no such thing... it's galvanic corrosion) so go figure.

[Peter Malcolm Jardine]

Trim tabs are made out of stainless steel. That's it, that's all.