Center of Gravity

[chunkymonkey28]

Hello,

I've come to realize that CG is pretty important on these boats, and I'm wondering where the ideal CG for a 27" mono is approximately? Should it be more towards the back or front?

Thanks in advance

[Fluid]

It depends on the hull design and the speed, but try to keep it between 7.5" and 8.5" forward of the transom. This will get you close.



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[chunkymonkey28]

sorry but what's the transom? I'm a bit new to boating.... thank you!

[LST XXL]

i'm pretty sure the transom is the back of the boat...

[Fluid]

Sorry - yes the transom is the flat surface at the back end of the boat onto which the rudder and trim tabs are attached.


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[LST XXL]

ok well instead of making a new thread to ask the same question i'll just ask it here...where abouts it the ideal CG on a 27 inch cat?

[bustitup]

ok well instead of making a new thread to ask the same question i'll just ask it here...where abouts it the ideal CG on a 27 inch cat?

I say between 8 1/2 and 9" approx 33%

[chunkymonkey28]

Sounds good thanks Fluid

[M.M.]

Me too!!

What would be the CG for a 25 mono? here: http://cgi.ebay.com/ws/eBayISAPI.dll...m=300268910685

[Simon.O.]

Me too!!

What would be the CG for a 25 mono?

It is approx 30 % forward of the transom as a starting point.
For a 25" that will be 7.5"

[M.M.]

So do i place a battery on each side approx. 7" inches to the back or center of the battery?

[LST XXL]

i think it would be to the center of the batery

[Simon.O.]

So do i place a battery on each side approx. 7" inches to the back or center of the battery?

Battery position will be dependant on where the boats balances.
Batteries are usually the best way to adjust and set Cg.
Have the boat ready to run as such so that includes Rx pack etc.
Place the batteries where they can be moved back and forth and see where the boat balances.
Use the packs to get the Cg point that you want and mark their position. Sort out your securing method, commonly velcro straps, and fit.

My new 30" mono has a 4S pack in front of the motor on its own "bed" and has the ability to move my Cg from 27-33% If I need a Cg outside hese parameters i will have to use ballast.

[nate]

Bath tub testing time!!!!

[Simon.O.]

Bath tubs are great for lateral stability checks. left to right balance, and to check a hulls self righting ability if any. Leaks show up real fast in the bath too.
A float test will not normally get you your Cg setting.

For a good estimate you mark the edges of the hull and place your fingers under this point(s) This gives you a very good idea of the fore/aft (forward / rearwards) balance point.
I'll not go into the long side of it but a true centre of gravity is very different to a centre of balance that we usually refer to in model boat hulls.
Cg, CoB, CofG are all very common terms to describe the same thing that we are often after.
Fingers or better yet is pencils under the nominated balance point and then move the batteries to get the balance.
I do a Cg check of my riggers before ALL runs to ensure that it is good to go.

If I have confussed anyone please sing out and I'll grab the camera and do a pictorial version of this description.

I am always keen to help.....and learn more.