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Twin screw handling question?

Discussion in 'General Yachting Discussion' started by Fishy, Sep 7, 2011.

  1. Capt Ralph

    Capt Ralph Senior Member

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    We may be overlooking one more thought here. Remember your old single screw handling, with a right hand prop, when you first put it in gear, the stern wants to squat to stb, in reverse, the stern pulls to port. Long ago it was explained to me water density (wet friction) had a better grab on the bottom of the prop. That's one of my basic walking ideas I keep in my head when I operate an unfamiliar boat, twin or single wheel.

    I think the original post was asking, is there a standard to apply when operating a new boat. I think safely answered; NO.

    You can keep some theories in mind, experience and fenders but the next boat you walk on, may (will) behave differently.

    May you have fast clutches,,,,
  2. YES!

    YES! Senior Member

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    Props and Rotation Do Not Matter

    I have yet to meet a seagoing lady that does not move her ass starboard when you ring up an aft bell on the port shaft. Same goes for forward on starboard, shes moving to starboard abaft the beam and to port forward of it.

    Opposing thrusts on each shaft will increase the lateral movement that can be additionally increased or decreased through rudder angle adjustment. Efficiency in this maneuver is exacerbated with inboard turning wheels.

    A flatter bottom will allow the bow to be more compliant in the walking maneuver whereas a deeper keel necessitates the use of a bow thruster to to maintain the ship perfectly parallel to the quay as she walks towards or away from her berth.

    I have seen it no other way in 40 years at sea......

    That's just my opinion.....I could be wrong ;-)
  3. AMG

    AMG YF Moderator

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    This is what we are all saying. Do you know if it is the same regardless of the props rotation..?
  4. YES!

    YES! Senior Member

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    As I said above, the inboard turning props are not as efficient in the lateral "kick". The outboard rotation provides the addition of wheel effect in the direction you are twisting. That is when the rudder angle can assist in additional lateral movement as well.
  5. AMG

    AMG YF Moderator

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    Thanks, I couldnĀ“t follow the wording exactly. May I add that on sterndrives with 2 x Duoprop, (probably same with Bravo 3), which means 4 counterrotating props, you get a sidewalk by steering the drives to the side you want and give reverse on that side and forward on the outer. (I hope I said it right, I always do it without thinking..:rolleyes: )
  6. YES!

    YES! Senior Member

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    With the outboards you enjoy the advantage of being able to actually steer the thrust (propellers) providing additional lateral control just as you do with jet drives and azimuth drives.

    Further to a comment above, you can play more with the wheel effect of CPPs while using negligible thrust.
  7. AMG

    AMG YF Moderator

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    I was talking about traditionally handled drives, not the new where they rotate individually (just like jets or pods).
  8. Capt J

    Capt J Senior Member

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    Inboard spinning propellors don't have nearly as much effect on twisting the boat or walking it sideways as outboard turning props, you generally have to give them throttle to get them to react similarly, but that is also how they are more efficient when running as the propellor thrust is sent out in a more narrow area.
  9. curtarmy

    curtarmy New Member

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    Just to add a bit of thought..... the downward angle of the shaft changes the pitch of the prop at the 3 o'clock and 9 o'clock positions. Therefore looking from behind a twin propped boat with counter rotating outward turning shafts/props, (port turning counter clockwise and starboard turning clockwise), the outboard arcs of each prop have the greatest prop angle and therefore most thrust. That is to say, 9 o'clock on the port prop and 3 o'clock on the starboard prop have the most angle and thrust. Therefore from a leverage perspective gives the most responsive handling. Also the most action when the rudder interacts with the most powerful segment of the prop wash.
    ie, underway forward, turn the wheel over to starboard, the starboard rudder gets slightly more pressure as it intersects the 3 o'clock wash from the starboard prop than the port rudder gets from the weaker wash from the reduced pitch from the 3'oclock position on the port prop.
  10. NYCAP123

    NYCAP123 Senior Member

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    Anybody with experience on the early 80's 56 Hatteras know if they can be walked sideways (no thrusters)?
  11. Capt Ralph

    Capt Ralph Senior Member

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    Rudders point to the direction of travel, lets say stb. stb main forward, port astern. (assuming the stb wheel turns right for forward). Both wheels are rolling to stb. Allot of clutching on the port.

    If I remember, the old hats had a nice keel. You hay have to work harder on your approach or drop fenders earlier.
  12. Pascal

    Pascal Senior Member

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    Yeah I m pretty sure the 56 has a keel like most earlier Hatts. She may walk, just, on a calm day but with any breeze it's going to be back to basics (like pivoting the bow of a piling to leave a dock when pinned to). So while fun to discuss and try, it has very little practical use
  13. Capt Ralph

    Capt Ralph Senior Member

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    On our ole girl, Working piles is a natural maneuver. When we get rich and famous, maybe we'll get a thruster.
  14. NYCAP123

    NYCAP123 Senior Member

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    Thanks guys. That's what I thought since she does have a keel. Pascale, DK about pivoting 74,000 lbs off a piling. You're a better man than I. Hopefully I won't have to do that too often.
  15. Pascal

    Pascal Senior Member

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    I routinely pivot my 53 of pilings or bulkhead (with fenders) when pinned by the wind. Same with the 70 footer i run ( not a Hatt but over 120k lbs) although I m a little careful if the docks or pilings appear "rustic"

    Thing is that on most boats, the BT will not do much once the wind gets over 15 or 20kts anyway so may as well do it the old fashioned way :)
  16. Capt Ralph

    Capt Ralph Senior Member

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    Roger Dat
  17. NYCAP123

    NYCAP123 Senior Member

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    Fortunately I'm an old fashioned guy.:) Done it many time with single screw and steel and aluminum hulls. Fiberglass:eek: Careful does it.
  18. Capt Ralph

    Capt Ralph Senior Member

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    Been working on an old Albin & GB, both single screw. Last week had to pull out extra lines and teach my partner how to clutch on a line to kick da butt out and curl around a dolphin pile to turn tight. Actually, it turned out to be fun and refreshing.
    Had a big grin later sippin on some rum. Drew some watchers and it all worked perfect moving some boats around a crowed dock area.

    Naw,,, We don't need no s@#$$ng thrusters when we win the lotto. just more rum...(maybe stabilizers).
  19. Caltexflanc

    Caltexflanc Senior Member

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    I have owned and operated one for 5 1/2 years. Put about 10,000 miles on it, take it out all the time. The short answer is yes. It does have a fairly deep keel. I have a thruster but I forget to use it half the time. Turn the wheel away from the dock and use the shifters.
  20. Capt Ralph

    Capt Ralph Senior Member

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    Away from da dock? Normal out swinging wheels?
    Cool. Just like Pascal said, fun to discuss and try..
    I feel a MOB drill coming on this weekend. While I'm pointing and sipping, Gonna make da wife & Boy try and figure out how to go sideways with out input from me. May show her this thread to prove I'm not pulling her leg.

    I'll report next week. Were 58x18 (Lil fatter), similar keel, spread between wheels and Small rudders. She'll figure it out.