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Thread: Trim tabs?

  1. #1
    Moderator AKmud's Avatar
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    Default Trim tabs?

    I'm thinking about adding fixed trim tabs to the back of our river boat to help lift the transom in the shallow stuff. My question is how thick of plate do I need to use for it to be durable and able to take the occasional bottom bump at speed? I was thinking 3/16-1/4" aluminum would be plenty but not sure. Also, what size of tab is overkill? I was planning on the tabs being full width of the boat each side of the motor swing and then about 10" back from the existing transom. I'll put a gussett on each end and possibly in the middle if there is too much flex.

    Ideas/suggestions?
    AKmud
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    Member fullbush's Avatar
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    Trim tabs don't work in shallow water. Your bow goes down and your stern lifts naturally w/o trim tabs when you get skinny. Those of us that forget to raise our trim tabs in shallow water usually rip them off (trust me I speak from experience) That was w/ Bennet trim tabs, then I got smart and went w/ 1/4" aluminum plate and Aurora stainless steel rams, now I only pretzel the ram when there down i n the shallows instead of breaking it like the plastic Bennet ram





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  3. #3
    Moderator bkmail's Avatar
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    And they become a PITA when you do get the boat stuck on a sandbar. They do not like reverse when you are trying to offload on the Lil Su either. As fullbush stated, in skinny water they don't help. Not trying to deter you, but there is a reason they don't run 'em on lil riverboats that frequent skinny water.
    Sure, the big 'ol Thunderjets and Weldcrafts have them but it is mostly to run salt or large rivers/lakes where there is deeper water vs. skinny rivers like the Lil Su where it can be inches deep where you are running.
    BK

  4. #4
    Member fullbush's Avatar
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    SS_7_Large.JPG
    I use the ram on the far left I have twin jets w/ a trim tab under each jet w/ 2 rams per tab mounted on 1/4" aluminum plate heres the link http://www.auroraair.com/Products/SS/sspicture.html

    I
    forgot to mention I power my trim tabs w/ an after market Volvo trim pump I think its Autolite or something I found it online It was like 100bucks and provide ample hydraulic pressure to power 2 rams at a time





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  5. #5
    Member Laker Taker's Avatar
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    Sounds to me like you need a set of flotation pods....

    http://forums.outdoorsdirectory.com/...flotation-pods

  6. #6
    Member alaskabliss's Avatar
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    I have learned the hard way that trim tabs and shallow water do not mix on a flat bottom boat.
    You really can't go with a fixed trim tab because varibles change and what worked today to help get on step won't tommorow.
    I have a Tjet and still refuse to put them on that. Anything that hangs in the water to provide lift also provides drag. Drag burns fuel. I distribute weigh in the boat to maximize getting on step quik and planning. Try this the next time your in shallow water and empty or full, doesn't matter. Go through the shallow spot at half throttle. You will really feel the boat lift, plane out level and your speed will increase. Trim tabs won't plane a boat out as effiecent or cheap as a foot of water will. I do this all day long with a big ole inboard and a foot of water.

  7. #7
    Moderator AKmud's Avatar
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    Quote Originally Posted by Laker Taker View Post
    Sounds to me like you need a set of flotation pods....

    http://forums.outdoorsdirectory.com/...flotation-pods
    I've thought about those.... A buddy said to make sure you have drain plugs in them though.

    I don't need the tabs to help get on step (17' with a 115 jet), I was hoping to gain another 1" or two in the skinny stuff with some extra leverage on the stern. A friend of mine has them on his boat and said they work pretty well helping to keep the foot out of the gravel.
    AKmud
    http://i78.photobucket.com/albums/j96/AKmud/213700RMK1-1.jpg


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    Moderator bkmail's Avatar
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    If you are trying to keep bthe foot out of the gravel then a tunnel hull is what you need.
    Aside form that, the pods would be the next best thing, but they add bouyancy and a slightly larger planing footprint for the boat.
    TUNNEL HULL the 'ol girl! Mike at Great Land welding builds nice river boats and might be able to help you with the tunnel hull design if you want to copy a proven set-up.
    BK

  9. #9
    Member pacific23's Avatar
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    Not saying you need these but here is a NEW type of tab and the work awesome.
    http://www.great-water.com/pages/QL/QL_Trim_Sys.htm

  10. #10
    Moderator AKmud's Avatar
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    This is what I am thinking about (just not enclosing them, bottom surface only) -

    AKmud
    http://i78.photobucket.com/albums/j96/AKmud/213700RMK1-1.jpg


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  11. #11
    Member JOAT's Avatar
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    I don't understand why you wouldn't want to enclose them? You don't need anything more than 3/16" bottom mtl and 1/8" for the upper box. Boxes like the photo you posted above can be entirely 1/8" and work just fine. It gives you all the benefit of a swim step and the additional planing surface. Plus, the flotation of the boxes also works while you're off step.
    Winter is Coming...

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  12. #12
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    Check out Lenco trim tabs on the internet. I put a set of the adjustable 9" x 12" on my G3 tunnel hull driven by a 90/65 Yamaha. It vastly improved the so-called hole shot, and I've used my GPS to check speed before and after installation, and convinced myself that I gained a couple mph by way of adjusting the trim and also the the angle of the trim tabs from the helm. The river I live next to has some rough shallow stretches, but no real mud flats, so I've not had to worry about getting stuck in the muck. I've had no problems getting started in a foot of water either, at least I've not seen gravel damage on my impeller or tabs.

  13. #13
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    I put a set of pods on mine from beavertail, they have drain plugs and let me tell you remarkable difference, LOVE THEM, got on step quicker, increased payload, and allows my boat to float evenly no back sag, 18/52 alweld 70 yamaha jet and I loaded 3 adult men and complete moose camp and supplys for 8 days no issues, dropeed the waterline a good 3-4 inches

  14. #14
    Moderator LuJon's Avatar
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    Be interesting to incorporate some aluminum tube into a framework for the design with the "tab" panel welded to the bottom so it formed a rack of sorts and was beefy enough to a rope-a-long to. The bottom of my boat extends about 6" beyond the transom and it is a PITA trying to drag it backwards off a sand bar! Perhaps having the tab tilt up in the rear would be the best of both worlds.

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