WTC height in the hull?

[Rhino]

Hi all,

Any advice as far as WTC placement in the hull goes? Is lower better? I can make the the WTC line up level with the drive shaft but it will raise the WTC about 3/4 to 1inch off the bottom of the hull. Alternatively I can put it low in the hull and use a u-joint.

is there a best practice?

thanks,

Ryan

[He Who Shall Not Be Named]

Just keep the ballast tank completely in the water with the boat in surface trim.

David

[trout]

Hi all,

Any advice as far as WTC placement in the hull goes? Is lower better? I can make the the WTC line up level with the drive shaft but it will raise the WTC about 3/4 to 1inch off the bottom of the hull. Alternatively I can put it low in the hull and use a u-joint.

is there a best practice?

thanks,

Ryan

The best practice is as David said, at surface the WTC should be completely submerged. That being said, I have seen subs that did not adhere to that rule. Is it bad? Yes and No. It is wasting your positive buoyancy because now you are lifting the WTC out of the water, however, you may have a slightly more stable sub, while submerged. So, to answer your question, if you can line up the shaft of your WTC with the shaft of your prop and the WTC will still remain fully submerged, that is a great outcome. If you still can raise your WTC higher and still be submerged, that is optimal for a stable boat. You are keeping ballast weight (sink) further away from foam (float) or ballast tank, it creates better metacentric height. The bigger (farther the distance of ballast weight verses float or foam) the height the more stable a sub will be.

[Rhino]

Thanks for the advice guys! Much appreciated

[RCSubGuy]

If you still can raise your WTC higher and still be submerged, that is optimal for a stable boat. You are keeping ballast weight (sink) further away from foam (float) or ballast tank, it creates better metacentric height. The bigger (farther the distance of ballast weight verses float or foam) the height the more stable a sub will be.

This is only applicable in surfaced trim with tanks empty. Once the tanks are filled, you've now added weight high in the hull versus low.

I, personally, put the cylinder in line with the output shaft or lower, never higher. It's much easier to stuff weight in a small area than foam. Putting the cylinder high restricts the volume where you can add foam.

Bob

[trout]

This is only applicable in surfaced trim with tanks empty. Once the tanks are filled, you've now added weight high in the hull versus low.

I have yet to have a cylinder with tanks full to be negatively buoyant. So, I do not see the weight high that you mention.

[RCSubGuy]

It doesn't have to be negatively buoyant for the center of weight to get higher when you fill the tank, or, perhaps more accurately, your righting buoyant force decreases as you fill the tank if the cylinder is mounted high in the hull.

Here are three options for mounting:

• Cylinder Low
  • Tank empty: less stable in surfaced trim
  • Tank full: More stable in submerged trim
• Cylinder along centerline:
  • Tank empty: no net change in stability
  • Tank full: no net change in stability
• Cylinder high:
  • Tank empty: more stable in surfaced trim
  • Tank full: less stable in surfaced trim

All of this is referring to stability about the longitudinal (roll) axis and not the pitch axis, which is a whole other ball of wax.