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Where Should My Center Of Gravity Be?

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Old 07-08-2012, 11:46 AM
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MadDogDan
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Default Where Should My Center Of Gravity Be?

I originally set my Revolt 30 up with a rather heavy Garmin GPS in front of the batteries so I could see which prop would give me the most mph. Now that Ihave chosen a prop which works quite well I took the Garmin out. Went to run the boat today and noticed a little problem. It runs smooth and true at half throttle but when running WOT the bow gets a little too light and the whole boat rocks violently from side to side. If I don't back off on the throttle it will get airborn. Before I adjust the plane tabs in the back I thought Iwould find out if my CG was even close to where it should be. On a 30" hull without the Garmin weighing the front down my CG was about 8" from the stern. I decided to shift the batteries forward in the tray and now the CG is 9 1/2" from the stern. I will test it out tomorrow but just wanted to ask if there was a general rule where the CG should be?

Thanks in advance for your help,
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Old 07-08-2012, 11:55 AM
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Default RE: Where Should My Center Of Gravity Be?

A good rule of thumb is 28%-33%, 28 being 8.4" from transom, 33 being 9.9" from transom for a 30" hull.
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Old 07-08-2012, 12:09 PM
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Default RE: Where Should My Center Of Gravity Be?

Thanks, that is what I needed to know. It looks like I was 27% but now set up better at 31.5%.

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Old 07-08-2012, 06:36 PM
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Default RE: Where Should My Center Of Gravity Be?

also the prop can toss the hull around like your describing
a prop with more lift will cause the boat to run loose
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Old 07-08-2012, 09:25 PM
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MadDogDan
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Default RE: Where Should My Center Of Gravity Be?

srt10:

I thought about the prop but the boat was very stable with the weight of the Garmin in front of the Lipos. The problem started when Iremoved the Garmin. I have shifted the Lipos forward changing the CG and will test it out tomorrow. Iwill report back after tomorrows run.

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Old 07-09-2012, 05:40 AM
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keep us posted bro
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Old 07-09-2012, 12:46 PM
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Default RE: Where Should My Center Of Gravity Be?

Well, it looks like I got the CG correct. Runs like a dream WOT. Very stable and fast, nose comes up so the last 1/3 of the boat is in the water but will not get airbornand will turn on a dime on command. My only goof up today was that I ran it WOT until the batteries were depleted which caused the batt / ESCwires to get so hot they melted some of the floatation noodles I had stuffed down the sides. Next time if I run WOT it will be for 6 minutes max.

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Old 07-09-2012, 03:58 PM
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Default RE: Where Should My Center Of Gravity Be?

Awesome news!!
What prop did you go with Dan?
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Old 07-09-2012, 08:57 PM
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Default RE: Where Should My Center Of Gravity Be?

I got a prop from Chris that he sharpened and balanced for his Revolt 30. It isa 47x50 and Ibelieve the stock prop is a 42x55. Not positive about those sizes but my GPS shows a definite increase in speed.

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