moving the mass

[valkie]

Hi Guys;

I have a small problem, at 3/4 throttle or over I get a bit of porposing in my 4.3 m runabout.

I have fiddled with trim and all sorts of stuff with no success.
The only relief I have had is when I put my spare full fuel tank up front last weekend.
This takes up quite a bit of room and I dont like fuel up front with me so I thought perhaps to move the battery.

I have been told that moving mass to the front may help, this is where I would like to move the battery from the rear of the boat to up under the bow.
There is room for it to sit nicely, I could secure it so that it would not move and it would bring the damn heavy battery from the back to the front.

I have purchased some serious cable to run the 4 metres to the back and would just like to know if anyone has attempted this before or if there is any possible issues I would need to consider.

Thanks

 

[generator12]

Re: moving the mass

Take a look here: http://www.nauticusinc.com/

Smart tabs! This is a trim tab that doesn't require manual attention. I put a pair on mine and it helped with porpoising as well as low speed maneuvering. Do a search for "smart tabs" on this forum and you'll get an idea what they can do.

 

[glenn property of pam]

Re: moving the mass

never done it because they say the battery can not take the beating in the front of the boat but many people have argued that it takes a beating under the hood of a truck so im on the fence as im tempted to move my batterys up front for better ballance while the boat is stopped as i like to fish on a level boat. smart tabs will proberly work better for porposing then moving the battery as they adjust the force. if you do move the battery make sure it is secured in case you catch a wave.

 

[valkie]

Re: moving the mass

Hi Guys;

Moved the battery last weekend.
I used some serious cable to ensure no loss of power through the 4.5m of cables running from front to back.
I secured the battery up under the front end and ran the cables through the hull under the flooring.

The result......
I found better performance in that it no longer porposes as bad.
At full throttle I get a small bounce, but only when I go over wakes and it dies down pretty quick.
The front end feels a bit heavier (as would be expected), but the handling seems unaffected.
It planes as good as before and has less effort to get on the plane.
It used to plane at 3500, it does it now at around 3000RPM.

Overall, what I expected and Im happy.

Cheers.

 

[pootnic]

Re: moving the mass

Was the battery a starting motor battery or for electronics and such?
I'm only asking because I wonder what size wire you did use.Serious cable does sound big enough but there are formulas to figure out exactly what size wire/cable you should use.Things like amp draw,length of wire,voltage,etc all come into play,wouldn't want things to get hot.
Moving the battery(like you've already done) isn't a problem though,glad it has helped you with your problem.

 

[valkie]

Re: moving the mass

Was the battery a starting motor battery or for electronics and such?
I'm only asking because I wonder what size wire you did use.Serious cable does sound big enough but there are formulas to figure out exactly what size wire/cable you should use.Things like amp draw,length of wire,voltage,etc all come into play,wouldn't want things to get hot.
Moving the battery(like you've already done) isn't a problem though,glad it has helped you with your problem.

The battery is used for both starting and running electronics.
I used cable which is used in mining for transferring 48000 volts to mining equipment.
I dont know the actual specifications but some basic dimensions are
Conductors are each about .25mm
There are enough to bundle into a cross section of 9mm.
I carefully tinned each bundle, tinned the connector and soldered both together.
At the lowest possible setting on my multimeter I get no loss from front to back, but the standard cable I used to have connected showed some loss/ impedence over the 1.5 meters of its length.

I use cable 1/2 this thickness for jumper leads on my car, they are 5 meters long and still never even get warm when repeatidly trying to start a car.

I was advised by the electrician that the only problem I may encounter with this cable is that it would add about 3 kilo of weight to the boat.

 

[Fl_Richard]

Re: moving the mass

Sounds like its done right to me. Enjoy!

 

[glenn property of pam]

Re: moving the mass

sound like the electrician is cheap and should have given him nickel tool wire but free is good