Reference point for measuring COG on Genesis

[JonD]

From what I can determine from these forums, about 30 - 32% seems to be a good starting point for the COG on a Genesis. But this is my first RC boat and I am still learing some of the terminology and fundamentals. What I am unsure of is where exactly is this full 100% length measured from (thereby determining where the 30% lies along the length of the boat).

On some postings it says the measurement is from the transom to the front. The rear of the Genesis overhangs beyond where the sponsons finish, by about 4 inches. So is the measurement for COG to be taken from the rear of the sponsons, or the transom where the strut attaches? I would have thought the rear of the sponsons.

Also, in determining the full 100% measurement, is this taken to very front front pointed tip of the sponsons. i.e. total length of sponson from very front, to where it exits the water at the stern?

Sorry for what must seem to be dumb questions to those that have been doing this for years........

Cheers,

Jon

[JonD]

Hi Ray,

That explains it well, and was exactly the info I was after. Would also explain why my stern was sitting so low in the water!

Many thanks,

Jon

[Mtwinste]

i did this today and ran it exactly at 250mm forward like stated but still porpoising so i went to about 260mm and still porpoising. need to go even more forward. got two 5S packs in there is really all. I guess 32% wouldn't be unheard of?

[JonD]

I believe that propshaft angle with respect to horizontal, and strut height, may also play an influence regards porpoising.

[Mtwinste]

how can one change the prop shaft angle? strut height is easy, i don't see how i can change the angle though

[JonD]

If you loosen the strut you should be able to tilt it slightly and thereby alter the propshaft angle (as well as raise and lower it) The stuffer tube may need a bit of "encouragement" by bending it slightly.

The subject was covered in this posting :-
http://forums.offshoreelectrics.com/...342#post323342

There's some good info in the whole thread, worth reading.

If you do some "Genesis" searching I think there are also some other threads/postings also relating to this.

Cheers,

Jon

[RayR]

It is not unheard of for a Genesis to balance at 34%. Each boat is different, and strut angle can also help eliminate the bounce. One adjustment at a time and test test test. You will find the right combo.

[Mtwinste]

Point prop further downward to stop bouncing I assume?