DNT99611
Senior Member
Can the V-drive be set off vertical? If it could, and a down angle tranny were used, could you then get an almost flat prop shaft and still have the engine in the stern?
kapnd wrote;
“Installing vee drives is a decision driven by space and weight distribution factors.”
Re space no new space is created. But space is made available amidships where it usually is considered more valuable.
“Weight distribution factors” is a much more serious matter.
Ideally you should be able to pull your engine and trans out of the boat and the new waterline would be parallel to the W/L w the engine installed. Most all boats will vary a little but having the weight bias a small bit aft is better. Perhaps almost essential. But reinstalling the engines far aft (as in most all Vdrives) is bad to very bad IMO.
Ideally and desirably the CG would be very close to the center of buoyancy. The downside to having the weight aft is mostly related to the boat running at inefficient angles of attack or running angles. Such boats will frequently be reluctant to get on plane. Being a trawler forum we’re not concerned about that but running at high angles of attack will be quite to very inefficient re fuel burn.
And I might add that most Vdrive boats will have tanks of fluid, batteries and other heavy equipment well fwd to compensate for the aft CG resulting from the Vdrive engines. One would think (as I did for years) that having all the heavy stuff in a boat in the middle of the boat would be ideal. Not so. As the sea heaves and rolls a boat is set in motion or should I say motions. A boat w all the weight amidships and little at the ends will be way too prone to yawing and pitching. EXCESSIVE yawing and pitching. Also a boat w most of the weight at the ends is a pig at the helm. Will be very reluctant to turn and once the yaw for a turn is in motion will be difficult to stop or reverse the action. And in pitching a lot of weight in the bow will send the bow deep into a steep sea.
Re the above it’s obvious that a seasoned NA needs to incorporate into a boat a good balance of weight distribution to give a boat desirable motions at sea and minimizing undesirable motions.
Above I probably painted the vdrive boat as undesirable. They are for many other reasons not mentioned but some Vdrive boats are quite to very good designs. They come to pass as the result of unusual circumstances like having a very low power requirement (like a sailboat or possibly a FD trawler) whereas a small and light engine like many Yanmars could result in excellent weight distribution. But w big 6 or 8cyl engines it’s not likely. Despite liking outboard powered boats a lot l’m very prone to say engines belong amidships in any arrangement that is somewhat close to ideal. And ideal weight distribution something one shouldn’t stray very far from.
Lbs per hour. There must be a flyboy in our midst. [emoji108]