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Post Posted: Mon Mar 27, 2017 9:11 pm 
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I thought to calculate the COG by using the vessel's length and dry weight, however, this would assume the weight is symmetrical across its length. But I have doubts this is correct since the hull is heavier aft of its center.

Does anyone know the COG axis point for a '76 170? If not, any boat builders out there know how to make this calculation with only knowing the hull's dry weight, beam and length? Thanks

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Post Posted: Sat Apr 01, 2017 7:05 pm 
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JB the only way to figure it out is to weigh it with a bathroom scale and a beam.. There are a ton of YouTube videos on how to do that so you don't bust Mama's good scale...

Measure/ weigh 3 places. One on each chine, dead in the stern and one under the forefoot at the most forward safe place to push up on the bow.

The key is to get the boat level and then measure back from the bow to where the forward scale is gonna go and make a mark.. Drop a plumb bob off the bow (Forward Perpendicular FP) and measure back from that to the stern. The distance from the FP to where you place the jack/scale is called the arm..

Now, the only way that it is gonna be accurate is to up on three jacks at once but for most of us that ain't practical.. So you can cheat when do this with the bow jack point by getting everything level, put the jack under, put a little pressure on it then lower the tongue of the trailer a bit and see what happens.. When the scale stops going up and the boat is level and clear of the rollers your have to bow done..

The stern is more of a challenge and after a day in the shop and a bunch of beer it is beyond me at the moment :1992_beer_cheer: ..

Once you get the numbers multiply the weight times the arm and that gives you a moment. Add up the weights of the two stern weights and use one moment, then add that them to the weight and moment of the forward jack point. The sum of the two weights and moments after the totals, divide the moment by the weight and that is the CG....

If this doesn't make sense, I will edit tomorrow... Omegang Dubble in a big bottle does not make for easy tech writing when it is gone.... sFi_wwe :beermugl: ...

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