Pear Anode - Which way round?

[flyingscampi]

I've surveyed my yard and it's about a 50% split between the large or small end towards the bow. Mine was previously fitted with the small end facing forward but it doesn't seem right...

I know I shouldn't worry about this sort of thing but I can't help it /forums/images/graemlins/grin.gif

 

[sailorman]

fat end forward

 

[wotayottie]

think of the way that nature shaped a fish!

 

[AIDY]

fat end forward... less drag that way /forums/images/graemlins/grin.gif think of the extra knot /forums/images/graemlins/grin.gif

 

[richardabeattie]

Definitely fat end forwards. If you were to put the fat end aft you would create vortices behind it - that would be a real drag.

 

[Sailfree]

Got to comment I know your answer is right BUT

Why is it for anodes is blunt end in front and sharp end at the rear and for boats its sharp end in front and blunt end at the rear!! /forums/images/graemlins/laugh.gif

 

[StugeronSteve]

Just make sure you fix it with the flat side up. /forums/images/graemlins/grin.gif

 

[AIDY]

are you talking from experience /forums/images/graemlins/blush.gif

 

[flyingscampi]

That one's sorted then!

Next question is should I mount the prop shaft anode next to the P bracket to reduce drag or leave enough space to withdraw the shaft from the coupling in case I need to remove the gearbox?

 

[sailorman]

the latter is properbly correct. i dont but will do nxt time

 

[philip_stevens]

Close to the P bracket, leaving about half inch for water to go through the Cutlass bearing.

 

[William_H]

The classic aerofoil is the name for the shape of minimum drag through a fluid. Cars aeroplanes or boats. It involves a rounded leading edge and a long tapered trailing edge. Tear drop shaped. This is because the drag is more significant as it reforms to its original position after the passage of the object.
The leading edge can be a semicircle and still be efficient but it must have the long taper at the stern. You need to look in 2 dimensions of the cross seectional area for the tapering.

Real boats (sailing or low speed displaceement hulls.) Do have this essential profile. Usually a long tapering of the depth up to the water line and often a tapering in to the stern. It is the cross sectional area in the water that tapers. Even though the transom is square.

However when you get to Mobo designed to lift themselves out of the water the stern sections are often flat making a plane surface to lift up on. As such they are often very inefficient at low speeds (large drag) where you will see the water swirling back to fill the void left by the departing transom.

So the other lesson for a sail boat is don't allow the transom to drag low in the water with too much weight aft. good luck olewill