Twin tab question
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Twin tab question

  1. #1
    Senior Member Scapegoat's Avatar
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    Default Twin tab question

    What's the difference on setup. Some angled some straight. Always wondered if it would be worth the investment on my cheetah. Would I want them over the tunnel or outside the tunnel. What the benefit of one over the other. How would it help at upper speeds?


    Thanks

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    what are you trying to accomplish? over the tunnel may help speeds by getting the bow up (trapping air). I can't see them helping speed on the sponsons. they might make it ride better though
    Last edited by professor_speed; 10-18-2012 at 04:40 PM.

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    Goes plenty fast for me(85), looking for better ride for cruising. Will handling be affected, if and how so.
    my sponsons are 12" wide and the tunnels are around 20".
    If I were to put some on the sponson would I put them angled like the sponson or straight.

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    Quote Originally Posted by Scapegoat View Post
    Goes plenty fast for me(85), looking for better ride for cruising. Will handling be affected, if and how so.
    my sponsons are 12" wide and the tunnels are around 20".
    If I were to put some on the sponson would I put them angled like the sponson or straight.
    Put the tabs over the tunnels and you wont lose speed and you will be able to put down force on the front of the boat for rough water and get a smoother ride! Also if you have any kind of porpoise you can get rid of it by slowing the air down in the tunnels!

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    I would put them over the tunnel. the only reason to put them on sponsors would be an attempt to extend the running surface to keep the boat on top of the waves. or if trying to stay on plane at lower speeds. although with tunnel tabs you will probably be able to stay on plane at a lower speed too. As far canted vs parallel typically parallel will be a hair faster cause they will be out of the water completely when on plane and positioned neutral or higher. the down side is that you have to make sure you pay attention to where they are positioned when cornering. as the boat leans in you now have a rudder like object in the water vs. if they were canted they are basically more running surface and less likely to cause a steering effect. obviously the bigger the tab the greater effect. Tunnel tabs will always be parallel but cats/tunnels don't lean in like a v so its a none an issue. with tunnel tabs you have to worry about the boat tripping on the tabs.they should not have much if any angle of attack at high speeds. obviously the speed and type of water you are in will dictate where you position the tabs. Daytona 22-25's have a similar looking transom and tunnel depth they seem to get good results with tunnel tabs

    whats cruising speed for you?

    Also have you called Cheetah? Im sure they will have some info, they probably have tried it both ways. I called the other day with a question, the guy that answered could not answer, so Bob got on the phone.

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    Thanks professor,
    i cruise between 60 & 70
    run havasu mostly, would like to handle chop a bit better. Plane better and cruise at lower speed.
    I was contemplating fix tabs on the tunnel and maybe some adjustable on the sponsons.
    whats tripping?
    havent called cheetah yet. Will do.

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    tunnel tabs work the opposite of trim tabs they trap air and lift the hull when they contact water the push the bow down. if they have a strong angle of attack and they hit enough water the push the bow down at a rapid rate and cause a "trip"

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    The tunnel tabs act the same as if they were a trimtab they force the nose down! maybe at a high speed they could create some stearn lift? Just put them on you will be happy!

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    Quote Originally Posted by riotact View Post
    The tunnel tabs act the same as if they were a trimtab they force the nose down! maybe at a high speed they could create some stearn lift? Just put them on you will be happy!
    At low speeds they act like regular tabs, the point of putting them above tunnels allows them lift out of the water when on plane if you put them down a small about, you can trap more air in the tunnel in turn lifting the hull, The tab position will help to move the center of gravity and help the hull be more efficient, but if they catch enough water they can counter act the lifting effect Dangers of Tunnel Tab on 36 Spectre Cat? - Offshoreonly.com lots of info here.

    at the speeds you cruise at and what you want to accomplish tabs on the sponsors may be more useful.( if you do cant them to match your sponson dead rise and mount the an inch above the bottom) you have not described a porpoise issue or the need to trap more air, and small loss of speed is of little concern.

    Don't forget to report back on how it works out

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