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When tunnel hulls first hit the model scean we saw all kinds of air dams, spoilers, wings etc. The reason the original 3 point hydroplanes were called spoon bills was because they took advantage of the air lifting the boat out of the water for greater speeds. As techology pushed performance the spoon bill design became too lifting and so they notched back the decking to reduce the excessive lift, hence the pickle fork. The summary of this story is there always will be the weak link in a design. Yours is the short boat length with an abundance of horse power. Part of the reason that the Genesis model is very fast is same reason the full scale Mystic 50 foot cat is the world record holder. Exactly what the proboat Miss Geico and other short and wide cats bring to the table performance wise has nothing to do with the proportions of the full scale Mystic 50 or and model using those same proportions. Not that I am a scale advocate my point is just that from a design point of view the long and skinny proportions of the Genesis are exactly the same as the full scale Mystic. Approx. 3.5 to 1. That is the boat is 3.5 times as long as it is wide. The proboat and other shorter but wider in proportion boat all suffer some of the same problem you are experiencing. The critics of the Genesis say it is too narrow and prone to rolling over to the side in the turns so it is a better SAW type boat than a heat racer. The wider cats may be less prone to roll over but they are also prone to blow overs as well. Therefore all things considered every design has what is called it critical speed factor. As funny as CatMan tried to be his point wasproblem if you don't try to go that fast. My point as is yours believe that the boat is not yet near its critical speed therefore with a little effort we should be able to increase the speed and still not flip.
Now in case anyone missed my earlier concern it is really very simple. With negative prop thrust you introduce two different forces to over come one bad habit. The two forces are related but different. One is pushing the bow of the boat downward--that would seem logical to offset the bow lifting up and over. The second force which goes hand in hand with the for every action there is an oposite and equal action --- that is the lifting of the stern from negative thrust, Again just think about it for a minute. How do you change the ride attitude with the prop thrust if not by forcing up the stern of the boat to leverage the front end in a downward direction. The bow does not want to go under the water so it bounces back up to the point that porposing or hobby horsing is just part of the normal expected result. In my opinion this is never going to fix your problem only make it worse.
jcald2000 suggested the air dam. I remember when the first full scale hydros added a angled wedge under the forward deck and they called them spoilers . These can be made from thin aluminum bent at a 45 degree angle towards the rear. Two different concepts in truth but each affect the riding attitude of the boat in the straight away high speed runs by breaking up the lifting forces at the nose of the boat. This could produce a result for your problem that will satisfy you. Stick these air dam sections under the nose with two stick servo tape. 2 minutes will tell you if this will produce your desired objective.If you like this then we can tweak the air dam for a more permanent solution.
A few questions, what is your actual boat called? I want to do some checking. I expect you run the boat with a full cowel, can you take a picture with it mounted. Just one good profile shot would be helpful. Was this originally a outboard hull? Do you know how much it weighs? Remember, small steps.
Dave
Now in case anyone missed my earlier concern it is really very simple. With negative prop thrust you introduce two different forces to over come one bad habit. The two forces are related but different. One is pushing the bow of the boat downward--that would seem logical to offset the bow lifting up and over. The second force which goes hand in hand with the for every action there is an oposite and equal action --- that is the lifting of the stern from negative thrust, Again just think about it for a minute. How do you change the ride attitude with the prop thrust if not by forcing up the stern of the boat to leverage the front end in a downward direction. The bow does not want to go under the water so it bounces back up to the point that porposing or hobby horsing is just part of the normal expected result. In my opinion this is never going to fix your problem only make it worse.
jcald2000 suggested the air dam. I remember when the first full scale hydros added a angled wedge under the forward deck and they called them spoilers . These can be made from thin aluminum bent at a 45 degree angle towards the rear. Two different concepts in truth but each affect the riding attitude of the boat in the straight away high speed runs by breaking up the lifting forces at the nose of the boat. This could produce a result for your problem that will satisfy you. Stick these air dam sections under the nose with two stick servo tape. 2 minutes will tell you if this will produce your desired objective.If you like this then we can tweak the air dam for a more permanent solution.
A few questions, what is your actual boat called? I want to do some checking. I expect you run the boat with a full cowel, can you take a picture with it mounted. Just one good profile shot would be helpful. Was this originally a outboard hull? Do you know how much it weighs? Remember, small steps.
Dave
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