Old vs New Circle jet setups
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Old vs New Circle jet setups

  1. #1
    Just Me snoc653's Avatar
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    Default Old vs New Circle jet setups

    Finally got a day that was above 50 so started working on the Eliminator. First order of real business was to clean it and analyze what it needs. As I was presurewashing the hull interior, I noticed two small holes that had been filled in the centerline of the bottom about right between the front seats. I crawled under the boat and it appears to have had turn fin(s) mounted about there. I know on the newer Comp Jet boats that the fins are well aft towards the front of the intake. Is this a change due to what works better? Any other changes that I should incorporate into the new build such as single mid tank vs two saddle tanks? Finally how far back from the dash should the steeringwheel be as to not get tangled in the dash on an unplanned departure from the boat?

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    Ultimate Squirter ScorpionJet1's Avatar
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    Default eliminator??

    What type of eliminator are you building I am currently in Arizona with my boat doing all the fiberglass work and and new stringers , paint etc I will post some more pics tomorrow when its light out to show my progress. Would also like to see pics of your ride and hopefully this summer we can get together and hit the big river.

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    Just Me snoc653's Avatar
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    It is an Eliminator Sprint. It has a long way to go as with the bitter cold this winter nothing got started except some engine work is underway. I'm hoping to get it going towards late summer and then take leave to head out west after our boating season is over and get at least one race on it. Here is what she looked like when I picked her up.

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    Crazy Eights Brad @ SCJB's Avatar
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    There are many things to consider when building a circle boat.

    turn fin placement is key. though i have never installed one, i have heard many theorys on what determins the 'sweet spot' is.

    As every boats bottom, balance and construction is different, i think its safe to say there isnt an exact measurement to go by (ex xx inches from the leading edge of the intake) that will work for every boat.

    one of the theorys ive heard was to load the boat up like its ready to go racing (fully suited driver, full tanks, etc) and jack it up with a car jack on a 2x4. the center of gravity will be your sweet spot for your turn fin.

    i have always throught the best rule of thumb is to keep all the weight center on the keel, including the battery, tank(s) and driver. If you have noticed, this has been the idea for most of the boats in the class. cj313, cj426, and cj21 all have center steering with most of (if not all) the weight between the stringers.

    When selecting a tank, go for one that doesnt allow for a lot of slosh. side gunnel tanks are probably the worst to run circles with in my opinion. This is because if you have a 10 or 15 gallon tank, thats about 6 lbs per gallon (60 lbs if you have 10 gallons)....thats 60 lbs of weight changing your center of gravity as you decellerate and accellerate through the turns.

    I picked up a hallet barron thats identical to your eliminator that I am not sure what I am going to do with just yet. When I bought it, I was going to make it stricly a circle boat, but I've had a change of heart since. We'll see. Goog luck with your build.

  7. #5
    Just Me snoc653's Avatar
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    Quote Originally Posted by Brad @ SCJB View Post
    There are many things to consider when building a circle boat.

    turn fin placement is key. though i have never installed one, i have heard many theorys on what determins the 'sweet spot' is.

    As every boats bottom, balance and construction is different, i think its safe to say there isnt an exact measurement to go by (ex xx inches from the leading edge of the intake) that will work for every boat.

    one of the theorys ive heard was to load the boat up like its ready to go racing (fully suited driver, full tanks, etc) and jack it up with a car jack on a 2x4. the center of gravity will be your sweet spot for your turn fin.

    i have always throught the best rule of thumb is to keep all the weight center on the keel, including the battery, tank(s) and driver. If you have noticed, this has been the idea for most of the boats in the class. cj313, cj426, and cj21 all have center steering with most of (if not all) the weight between the stringers.

    When selecting a tank, go for one that doesnt allow for a lot of slosh. side gunnel tanks are probably the worst to run circles with in my opinion. This is because if you have a 10 or 15 gallon tank, thats about 6 lbs per gallon (60 lbs if you have 10 gallons)....thats 60 lbs of weight changing your center of gravity as you decellerate and accellerate through the turns.

    I picked up a hallet barron thats identical to your eliminator that I am not sure what I am going to do with just yet. When I bought it, I was going to make it stricly a circle boat, but I've had a change of heart since. We'll see. Goog luck with your build.
    I have heard the center of gravity theory for the turn fin before as well. I was planning to try something along those lines and find the ballance point that would keep the boat level between the lowest part of the spoon shap in the keel and the back edge of the intake grate opening. Once the hull was ballancing in this configuration I would mark the CG and use aircraft type weight and ballance to keep the ballance within an acceptable range of that CG. Factoring in some basic thrust and lift vectors I should be able to set the fin at the CG and keep the boat ballancing at or just in front of the CG at full thottle and just aft of it at partial throttle to maximize loading the intake. Center steering is a good thought and one I'll definately be rethinking now. I wonder why more of the flats don't go to center steer. Was the Hallet a splash of the Eliminator and if so does yours have a turn fin?

  8. #6
    Crazy Eights Brad @ SCJB's Avatar
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    Quote Originally Posted by snoc653 View Post
    I wonder why more of the flats don't go to center steer. Was the Hallet a splash of the Eliminator and if so does yours have a turn fin?
    i wondered the same thing about the flats (v-drives)....well, someone pointed out the obvious to me ...they would be sitting on the v-drive.

    i dont know who splashed who....i dont know the history of either hull. havent really had a chance to look into it...only thing ive been told is they werent run in compjet but where run in more endurance style events.

  9. #7
    Boat Nut sleekcrafter's Avatar
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    Did the Sanger Hydro Jet boat compete in the circle racing? I know some had a fin on the bottom, and they seem to do ok in the rough water. With the addition of a turn fin on the sponson, you would think they would corner kind of well.

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