Twin screw handling question?

The 56 is also an 18'2". A bit of a tub and a handful in current and/or wind. I rate myself about a 5 out of 10 on close quarter handling, a little dyslexia and ADD being the issue. But somehow just the wife and I have managed over the years. She is much more likely to "push the button" than I. Why not? It's there and we spend money maintaining it. I just forget about it now and then.

Screw Drive Solution!

Chrysler Corporation Advert 2 - YouTube

Funded by DARPA...

I've pivoted 200 tons off of a wood piling, if the conditions are not super windy, you're not really putting that much force on the piling to pivot the boat if you do it nice and easy...... Think about it, you can pull in the stern of a 100' boat with just 1 person or by steping on the line with 1 foot, providing the winds not howling.

And on snow??

So what happened? Why didn't we use it in the rice pattys and delta in Viet Nam in the 60's?

Why... it looked like it would work... and "no good DoD program ever takes less than 20 years... never is ready for the war its needed for... costs less than an order of magnitude of its estimated cost... So it had to be cancelled as soon as it showed its stuff".

Government

If only this wasn't so true!

Egg Beater

I always liked the egg beater principle...
Voith Schneider Propellors - YouTube

Yes exactly, the greater water pressure exerted on the bottom of the props allows for a better "bite"

I have a simple question about pivoting (turning on a dime) re most SFs.

I currently have a GB trawler, full keel. If I want to turn to back into a slip for instance, I have to use my rudder hard over or else it will turn only sluggishly if I'm just using my gears. My understanding is that with most SFs one can turn on a dime with gears alone and not messing with rudders...

I suspect that since SFs vary (Hatts have a keel, Oceans and other Jersy's pretty flat aft of amidships) the responsiveness to gears alone will vary. My guess is the Hatts might need some rudder whereas the Oceans no. Is this true?

Probably more important than water density. The downward angle of the shaft changes the size of the prop bite on the port and stbd sides of the prop relative to the horizontal forward movement of the vessel. The stbd side has a larger bite, and therefore creates more thrust on the stbd side of a right hand prop (clockwise as viewed from astern).
Think and.sketch it like this... If a prop had a bite of 5 degrees, and the shaft had a downward angle of 5 degrees then relative to horizontal (or the movement pf theboat) the stbd side of the prop would have a 10 degree te on the downward sweep and the port side would have a 0 degree bite as compared to horizontal.
Thus the movement to stbd on a single prop.
Curt

Adding rudder always helps but most SF guys don't bother unless they're setting up against a severe crosswind or current. Most SF guys also get a lot of practice manuvering in rewind chasing fish so know how their boat responds better than most casual cruisers. Most newer ones also have bow thrusters helping even more.

Older hatts did have some keel as did Oceans but the latter typically had less transom deadrise which makes spinning easier. Mid 90's to mid 2000's the keels went away and both spun relatively easily. Newer model Hatt's have large tunnels which make it more difficult to spin much like their older sisters.

SF's typically respond better than comparable sized MY's due to their reduced windage forward, they also usually have quite a bit more horsepower available to increase thrust if needed but in most cases the pro's don't use throttle. The old adage "fast goes crash, slow goes bump" runs through my head all the time!

Got it. Thanks Bill!

Also the distance between the props can make a significant difference. My props on a 50 Post 17 wide have, I would guess, 18" or more distance between them then say a Viking of the same size because of the beam and the fact that the engine are mounted more outboard. Very responsive boat for a variety of reasons. I have never used any rudder and make sure my tabs are up.