"Sternz up, Bowz Down!"

If you don't have at least a mild interest in half-baked physics, skip this post

Those were Snoop Dogg's exact words when I called him to ask for advice on our boat's weight distribution. I thanked him earnestly and began thinking about the situation. As far as I could surmise, the problem was that the moments exerted by the motor, stern leg and (to a lesser extent) the battery, were all significantly behind the boats centre of buoyancy; the pivot about which these torques are applied.

I ran a string line along the boat's bottom and its current waterline, and worked out the rough cross-sectional area every 0.5m. By averaging these and mutiplying them by the waterline length, I came up a point 1.2m from the transom as the boat's centre of buoyancy. I then worked out the torques on the sketch below:

The negative number reflects the torque's direction, ie pushing the stern down. I estimate (based on no evidence whatsoever) that if that were reduced by half or more then the boat would sit about right. But how?

A few options spring to mind:                

1. Move the engine forward

2. Add ballast to the front of the boat to balance it

3. Find a lighter engine, or even modify the transom for an outboard

4. Add displaced volume behind the centre of buoyancy.

I am lucky to have a buddy who works for a prominent yacht building company, and he suggested considering extending the hull, but boxing in the stern leg where it is. I had had a bit too much to drink at the time that this chat took place, so possibly missed some useful tips that might have made the process easier, but I came up with this the next day:

Essentially the plan was to build two hull extension box things, to around half the transom height, and pass it off as a swim platform. I sketched them and came up with dimensions, and found they'd add around 70kg of buoyancy each when submerged. Those with experience in reading kindergarten-quality technical diagrams will see above that they restore net torque on the system to just -20Nm, in conjunction with the battery being moved to the bow.

I can't be sure this will work, since its an assumption made upon previous assumptions, but it will definitely help. If need be the issue can be mitigated with other measures from the list above.

Snoop will be so pleased :D , see ya next time!