Finding balance point for tunnels

[rumrunner]

What's the percentage for finding the balance point of a tunnel is it 29%? And is that the same place as

The cg

Thanks Shane

 

[jaxracer]

Yeah, balance point, cg, it's all the same. But from hull to hull the optimal cg % is different but a good starting point is usually anywhere from 26%-30%. At least that's been my experience. I know the old school mark used to be 33% from what I was told when I first got into the tunnels like 12+ years ago but I've found better cornering and overall hull characteristics from running the cg farther back. I utilize weight and motor height to compensate for the cg being farther back so I'm able to keep the boat aired out down the straights without worrying about blowing it over.

-Jr.

 

[rumrunner]

Thanks Jr

 

[HTV Boats]

Jr is on the right track. Better to setup with weight to the rear and pull some forward rather than fight ill handling cornering trying to balance to a certain point. I have 12-15 fairly competative hulls in my workroom and I couldn't tell you what the CG is on any one of them. I rig em and run em then make the needed changes at the pond. CG is a guideline not the bible.

Mic

 

[TUNLBOTR]

food for thought.....

use fuel load as CG inverter,as fuel drops CG moves slightly forward. Set up for optimal balance for lap 5 and 6. I run it slightly on the heels (CG back) and let it get better as the heat unfolds...

 

[rumrunner]

That 's. All I was looking for was a ball park , but like you guys said I don't want the weight to far

Forward , so do you think is a starting point? Htb 360 is11inches ,my boat is 36 inches

Thanks

 

[jaxracer]

If that's what the boat weighs in at with no fuel and no weight added then yeah, try it. Especially if that's for the 101. If the boat is too flighty, don't be scared to drop the motor. That's a lot of power for that boat so the prop sitting at or below the sponsons won't hurt a thing.

Consider the fact that a prop deeper in the water means a more continuous blade in the water, therefore a more continuous power band. One of the reasons why we run our .21 engines so high is because the engines are all RPM based with minimum bottom end torque, so in order to pull the bigger props that a lot of guys want to pull like the 1440s or the x442s, the motor has to be raised for the engine to unload, which in turn causes a lot of handling issues for many.

With a big engine like that, you've got plenty of torque to go around so setting that prop deeper in the water to keep the boat on the water down the straights shouldn't hurt a thing, while also keeping the cg farther back in the boat and therefore improving cornering characteristics by helping to keep the nose up and the back end down preventing hooking, rolling, etc.

-Jr.

 

[rumrunner]

Thanks guys you've been a lot of help ,once I get all the radio gear in and I,ll go from there ,write know it,s 8.5 -9.0

Thank shane

 

[Richie R]

If that is where you are at, it will be nose down till you get the speed up. Probably will not handle to well at slow speeds. Plus it also depends on what kind of prop you use. I run mine with a cmb 67 at 10.5 to 11". It will do a good 60 but you have to really watch it when you are racing though. Hope this helps.

Richie R

 

[rumrunner]

Before I had my mac84 on my hornet I had it on a htb360 and I started 11inches after I did testing at WTC I end up putting two full sticks of lead on each sponson and it still only run on the prop, I guess it

Still is trail and error

Thanks shane