Adding Drop Fins to my Trim Tabs ...from another thread-gctid810469

[CptCrunchie]

After engaging the other current thread on trim tabs, I've decided to add drop fins to my Boat Levelers. While I could make them longer than the 9" chord, if I get even Ôàô more lift from the drop fins, I'm not sure I really need more length.

I just picked up 4 pieces of 12ga stainless plate from my local scrap dealer, ....$30! I I also picked up two dozen ┬╝" x 1" SS bolts and locknuts, so I will be bolting them to the existing tabs.



To even out the stress on the piston, I'm doing a Ôàô-Ôàö, 4" and 8". I'm also angling ┬¢" of the inner fin so the angular flow from the dead rise will go under the tab rather than over it and create spray.



Now I'm off to do some metal cutting .....in my wood shop. Fun, fun, fun. B)

[Dadrock33]

Sounds interesting Crunchie . . keep us appraised of your progress with pictures, please. One thing that I noticed while looking at a video of mine - the drop fins seem to "not be in line with the water coming out from under the boat" . . . . don't know if that makes sense to you but it almost seems as if the whole tab and the drop fins are "angled" a bit off the center line . . . probably just an optical illusion but my opinion anyway.

[CptCrunchie]

"Dadrock33" post=810490 wrote:
Sounds interesting Crunchie . . keep us appraised of your progress with pictures, please. One thing that I noticed while looking at a video of mine - the drop fins seem to "not be in line with the water coming out from under the boat" . . . . don't know if that makes sense to you but it almost seems as if the whole tab and the drop fins are "angled" a bit off the center line . . . probably just an optical illusion but my opinion anyway.

I thought the same thing, but that doesn't make sense to me. FWIU, the drop fins 'catch' the water climbing the dead rise, and that would create lift. To angle them with the flow would lose that, and to angle them against that would create more drag than lift.

[CptCrunchie]

Got 'em cut to size and marked for bending. Thought it would be more difficult to cut, but my little 4.5" angle grinder with a thin cutting blade, followed by a sanding wheel make quick work of it.



Tomorrow I'll take them over to get them bent.

[Guest]

Get the holes punched into them if you can. Stainless steel is no fun to drill.

[CptCrunchie]

"pjumper" post=810506 wrote:
Get the holes punched into them if you can. Stainless steel is no fun to drill.

Not a problem. I have lots of ┬╝" titanium and cobalt bits, my drill press slowest speed is 400rpm, and I have about a pint of cutting oil. I also have a diamond wheel bit sharpener.

I even have the polishing wheel and compounds to give them a really nice mirror finish shine .....if I suddenly get that much needed rush of enthusiasm to do that, .... :whistle:

[Guest]

Sounds like you have it covered. Let us know how the tabs work out

[builderdude]

Crunchie, you can sharpen drill bits?? I'll send my 5 gallon bucket of used ones over pronto. :lol:

[CptCrunchie]

"builderdude" post=810517 wrote:
Crunchie, you can sharpen drill bits?? I'll send my 5 gallon bucket of used ones over pronto. :lol:

LMAO! Yeah, but results say I rarely do. I buy more than I sharpen, and I mostly sharpen the bigger ones and the expensive ones. I picked up ahttp://www.grizzly.com/products/Prof...ctor sharpener from Grizzly Tools awhile back. Works good, though it took a LOT of practice.

[SprinterX]

the objective of drop down fins is to capture the water flow under the tab rather than allowing it to blow out the sides. by maintaining this captured water flow you increase the lift. the fins need to be on the outer edges of each tab to be most effective.


Attached files

[CptCrunchie]

"SprinterX" post=810535 wrote:
the objective of drop down fins is to capture the water flow under the tab rather than allowing it to blow out the sides. by maintaining this captured water flow you increase the lift. the fins need to be on the outer edges of each tab to be most effective.

All due respect, I disagree. http://www.baylinerownersclub.org/in...s sense to me, so I'm going to try it. It's just bolts and some stainless steel and I can always change it.

[CptCrunchie]

Next step completed, they are bent!



My friend couldn't do them, because his brake takes up to 16ga. After visiting 4 other shops, I found a sheet metal company who had a brake that was older then both of us put together. Total cost: $18!

I stopped by the boat to mark where the holes need to go, and discovered the piston mount has pan-head bolts, and they need to be drilled through the drop fins too. I also need longer bolts ...which I have.

I also discovered the current tabs have an 8" chord; I thought they were 9".

Now I'm off to drill some holes. Yeehaw!

[CptCrunchie]

Drilled and buffed.



Next is put holes in the tabs. I'll be drilling them in place, so I'm sure my arms and back will need a hot tub after. The tabs are on there so securely, I'd rather not disturb them.

[builderdude]

Crunchie, looks good, you gonna angle the leading edge of the drop fin a bit?

[joe]

hope you are using 316 ss. or they will rust.