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View Full Version : Arneson Rocker Plates--Why Won't Regular Tabs Do the Same Thing??



rustnrot
08-19-2007, 06:11 PM
Until today, I thought the so-called Arneson Rocker Plates were actually something that attached to their surface drive assembly. Not so.

http://www.arneson-industries.com/page.php?type=products&id=rocker

They show them being utilized with I/O's as well. If I install "regular" trim tabs flush to the bottom of the hull, why can't I create my own "Poor Man's Rocker Plates"?

MOP
08-19-2007, 07:07 PM
Tom the rockers are mounted dead flush with the transom, when lowered they do basically the same thing as standard tab. But when raised the water flow stays attached which pulls down on the stern raising the bow, on many surface drive applications they are an absolute must.

Phil

rustnrot
08-19-2007, 07:30 PM
Phil, I agree. But why won't regular tabs, if mounted flush with the bottom of the transom do the same thing???

drew0982
08-19-2007, 07:46 PM
speaking of rocker-plates and trim tabs... are these any good?

http://cgi.ebay.com/ebaymotors/Instatrim-boating-marine-trim-tab-kit-12-x11-New_W0QQcmdZViewItemQQcategoryZ31283QQihZ018QQitem Z280143438845QQrdZ1QQsspagenameZWDVW

http://cgi.ebay.com/ebaymotors/Smart-Tab-trim-tabs-st1290-60-12-x-9-17ft-22-ft-NEW_W0QQcmdZViewItemQQcategoryZ31283QQihZ003QQitem Z130142624876QQrdZ1QQsspagenameZWDVW

rustnrot
08-19-2007, 08:00 PM
I know very little about trim tabs but with 2 hours to go, I know a friend who has the Insta-Tabs on his cruiser for years and they work fine, but I'd stay away from the SmartTabs...

MOP
08-19-2007, 09:15 PM
Tom if he does not need bow lift to get max performance buy regular tabs. I would have liked to have tried rockers when I had the BH on mine, they were to pricey to experiment with.

Phil

BigGrizzly
08-19-2007, 09:23 PM
The real answer is the rocker plates have no void to let air in. not just flush there is no air gap and no hinge plus They actually bend in an arc hence rockerplates

Sweet little 16
08-19-2007, 09:42 PM
like Grizzly said rocker plates bend they can be bent or curled into a rocker shape I think some models can add hook as well as the fulcrum on a trim tab is at the transom and the fulcrum on a rocker plate is in the middle of the plate and the lever is at the end hence it can bend up around the fulcrum "rocker" or down around the fulcrum "hook"

Lenny
08-19-2007, 10:40 PM
...and for 4K$ they should be a "bit" different. I'll let you know how they work for me.

:)

DonCig
08-20-2007, 08:35 AM
I have never used the Arneson rocker plates, but in discussins with George; one thing that came out of the conversation is that you need a smooth lake surface to create the bow lift; and if you loose the surface tension of the water the bow comes dropping down. The last time I looked at the lakes that I boat on; there were very few glass water days. I could be wrong on this subject so I would reccomend further due diligence if you are going to purchase these for your boat. And loosing bow lift at high speed has been known to make one age a few years immediately.

Don

Lenny
08-20-2007, 08:46 AM
And loosing bow lift at high speed has been known to make one age a few years immediately.
Don

not to mention the clothing change required and the Angina pills.

HallJ
08-20-2007, 11:40 AM
Phil, I agree. But why won't regular tabs, if mounted flush with the bottom of the transom do the same thing???



The reason regular tabs don't do the same thing is,
the change in angle from the running surface of the hull to the bottom suface of the tab is too abrupt to keep the water flow attached to the tab. Thus the low pressure area under the tab is eliminated and will not generate the bow lift effect.

Jeff

rustnrot
08-20-2007, 12:14 PM
...got it. In the pic the actuator is the "warper" of the bottom plate (tab) so to speak. Looks like it can "warp positive"--I'll call that "upward", or "warp negative"--I'll call that "downward"

"Scotty-give me warp 2 positive"!!

Simple concept, I can see where surface tension could come into play also. I can also see building a home-brew version for far, far less than $4k!

Formula Jr
08-20-2007, 07:09 PM
Love the idea as a sneaky way to get Rocker Plates, but Bennetts don't lock in both up and down directions like outdrive trim. Outdrive trim has two hydrolic lines on both top and bottom of the ram cylinders. Both fill and drain, which moves the piston in the sleave and holds the ram in place both fore and aft of the cylinder. Bennetts only "fill" and "drain" from the top and only " pressure lock" against positve force against the bottom of the tab.
A low pressure zone, needed for effective rocker, on the bottom of the tabs would just work against the internal springs. Bennetts are just not designed to work in the way you are thinking.

http://www.epud.net/~owens/rocker.gif

So if you got the right kind of rams, this could work.

rustnrot
08-20-2007, 08:00 PM
The type of cylinder needed is what is inside the Pulse Drive surface drive and lifts the drive up and down. There is a fitting on the bottom also, you just cannot see it in the pic. This cylinder is driven by a simple trim pump.

http://i104.photobucket.com/albums/m178/rustnrot/bateau%20XK18%20Photos/xk18_drive_1.jpg

Formula Jr
08-20-2007, 08:49 PM
Oh! Thats right, you are running a pulse drive. I Gotta think about that a bit more....

rustnrot
08-20-2007, 09:02 PM
Pulse Drive, yes, and at this time I have no idea whether I will need to add any rocker or not.

Interestingly, the hull originally had approx 1/8" pockets with a stainless steel plate on each side (did not go past transom edge). Plate was adjustable from inside turning nuts on through-bolts method and provided maybe an extra 1/8" to 1/4" hook on the plates. I look at that as a Good Thing in that the hull ran bow-high and this seems like an afterthought way of correcting the problem...dunno.

Fast forward to now. Methinks leave the pockets there after blueprinting the hull as perhaps they will add some faux rocker? Or should I fill in flat?

Or (and probably this would be most prudent)...rig the boat enough to run it with engine/drive combo temporarily before doing a complete resto to see how it goes....

http://i104.photobucket.com/albums/m178/rustnrot/bateau%20XK18%20Photos/xk18_drive_2.jpg