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New to RC boats got BJ 26

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New to RC boats got BJ 26

Old 09-08-2008, 06:04 PM
  #26  
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Default RE: New to RC boats got BJ 26

how do i put negative thrust or change the cup on the prop. Sorry, I am new to the RC boat world and am still learning about all this. The BJ 26 is out of the box..no mods and I bought it used. So still trying to figure it out.
Old 09-09-2008, 02:02 PM
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Default RE: New to RC boats got BJ 26

Negative thrust is pointing the prop & shaft down slightly, rather than level - try VERY small changes (like 1/2 degree increments); The cup of a prop is the the amount of curve in the blades from front edge to rear edge. Obviously your new to this, so read Piper Chuck's sticky thread on this forum about props before you try to change you prop's pitch.

The reason I suggested making these changes is from a story I was told this weekend by a fellew boater (Larry) who went to the Mendota IL races a few weeks ago. While there, Larry's favorite prop came off and was lost. So Chris Wood (a well known boater/racer/boat builder) asked what Larry had for other props. Larry told Chris and Chris chose one. They threw the tunnel hull in but all it would do is cavaitate and not get any speed nor launch worth a... Then Chris added more cup to the prop and added some negative thrust, and not only did the boat NOT cavitate, but Larry said he picked up 7MPH more than he had ever had. So I tossed this out for you to consider.

BTW Increasing the cup of a prop makes the "thrust cone" smaller.... Think of a flashlight - if you shine it on a wall, you'll see a lit up circle on the wall that is larger than the lens on the flashlight (a cone). Water coming off a prop acts the same way.... the narrower the cone - the more thrust you get - that is what adding cup does.... focuses the water more. Tweaking props is something that can have a really dramatic effect on your boat BUT before you go bending and unbending your props, READ all you can, where to bend etc.
Old 09-09-2008, 02:05 PM
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Default RE: New to RC boats got BJ 26

Negative thrust is pointing the prop & shaft down slightly, rather than level - try VERY small changes; The cup of a prop is the amount of curve in the blades from front edge to rear edge. Obviously your new to this, so read Piper Chuck's sticky thread on this forum about props before you try to change you prop's pitch.

The reason I suggested making these changes is from a story I was told this weekend by a fellew boater (Larry) who went to the Mendota IL races a few weeks ago. While there, Larry's favorite prop came off and was lost. So Chris Wood (a well known boater/racer/boat builder) asked what Larry had for other props. Larry told Chris and Chris chose one. They threw the tunnel hull in but all it would do is cavitate and not get any speed nor launch worth a... Then Chris added more cup to the prop and added some negative thrust, and not only did the boat NOT cavitate, but Larry said he picked up 7MPH more than he had ever had. So I tossed this out for you to consider.

BTW Increasing the cup of a prop makes the "thrust cone" smaller.... Think of a flashlight - if you shine it on a wall, you'll see a lit up circle on the wall that is larger than the lens on the flashlight (a cone). Water coming off a prop acts the same way.... the narrower the cone - the more thrust you get - that is what adding cup does.... focuses the water more. Tweaking props is something that can have a really dramatic effect on your boat BUT before you go bending and unbending your props, READ all you can, where to bend etc.

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