12' rocket launch

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RodBow
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12' rocket launch

Post by RodBow »

OK, I will admit up front that this is probably knowledge that everybody should be born with... I was the last of five kids, so maybe it got run out before I got some.

You may have seen a post the other day about running my 12' deepvee aluminum Starcraft with the 15 'rude. When I'm by myself it looks (and feels) like I'm trying to lift off from the Cape until up on plane. Ofcourse I also have to play the "don't slow down too quick - or swamp over the stern game" when stopping. :smt039

The question: About the trim notches on the motor. City boy logic has it that the closer - or less - the tilt of the motor in relation to the transom the more the bow of the boat should stay down. Is this correct? I'm starting to second guess because there's four other notches going away from the transom the other way (I'm in the very first closest notch).

Any wise words appreciated..
RB
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tin can
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Post by tin can »

Rod, that's normally the way it works. But there are other considerations. Type of boat, boat length, and weight distribution, to mention a few. Try moving some of the load up front when you're by yourself.

My son has a 16' flat bottom aluminum. It doesn't ride nose high, but it bounces terribly. He has about 75 pounds of lead under his front deck to stop the bounce. That's where he came up with the name LedSled.
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dstockwell
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Post by dstockwell »

Where does the cavitation plate sit in relationship to the bottom of the "V" should be level or real close. If its to low lots a drag, to high no bite.
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RodBow
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Post by RodBow »

Don, Thanks for pointing out that I know less than I thought!
There's two plates. 1 just above the prop is 2" below the bottom of the boat and the other (up higher) is 1" above the bottom of the boat. I guess one of these is the cavitation plate...?
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dstockwell
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Post by dstockwell »

2" below does not seem all that bad, but if moving the motor up to the next mounting hole would get it closer that may work better. Not sure how you trim, but I always trim up 4 or so clicks, I found that to be the best speed to RPM setting. On mine guage thats 3 bars, but I have the digital so not sure what that would be for you.
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RodBow
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Post by RodBow »

I think you're thinking way more modern and digital than what I got.
This is a '85 model Johnson Sea-Horse with 2 motor mounting clampscrews - there are no other mounting holes.

To bring the plate up the inch or two, I guess I could block the top edge of the transon under the mounts...

Maybe the 75 lbs in the front of the boat would be the quick solution when live ballast isn't available.
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tin can
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Post by tin can »

Rod, you might also want to try some quick and easy home made trim tabs. There's nothing to it, and the cost is less than $10. PM me if you're interested.
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Post by CSMarine »

Rod, had a 12 foot Alumacraft, with a 6 horse Johnson. It would do the same thing. Bought a Dolefin for it and it stopped. If the trim pin is in the last hole closer to the transom, and it still "tail stands" it most likely just needs a bigger cavitaion plate to get the back end up so it will plane faster. The Dolefin would help with that. If your nose is digging after you adjust your trim pin it's in too far.
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RodBow
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Post by RodBow »

OK, finally got the trim tabs from Metal Supermarket. What a great bunch of guys and accommodating too. Thanks to TinCan for stearing me their way. These guys can do small piece work for stuff like we all need from time to time.

The question now is, where to put them. On the boat there is a runner going the lengthwise on both sides of center.

Should the tabs go to the inside or to the outside of the runners?
Thanks,
(drill in hand)
I asked Len at Metal Supermarket if they needed a drafting guy... After I showed him my picture drawing ability he didn't seem very interested..?
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Post by sharkboy »

You definitely want to go to the outside to avoid disturbing flow to the prop.
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mjsigns
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Post by mjsigns »

Something that might help is to take some of your sons’ weights (maybe 200#), bind them together and tie them in the bow. The trim tabs you are considering will not likely be effective until you get up enough speed on the water, and you will still probably have to play the stopping game.

PS do still want to borrow that high-speed cuter we were talking about?
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