Twin Engine - Control Question?

[miket]

Endorse Mike's view.

Did one of the Southampton Boat Show competitions, and during practice (on someones Sunseeker Portofino 40, 2 x 230hp outdrives) the "Yachtmaster Instructor" on board advocated use of one engine only for close quarters handling. We did and it certainly worked well.

Best bet is practice at both, and make your own decision.

 

[byron]

YOU of all people should know Mike that some of the Judging left something to be desired at that competition. Personally I would like to see a Judge's own boat handling before they be allowed to sit in judgement on others. I can think of certain dudes who Judge on the Thames (you know who I mean) that hit everything in sight when at the wheel.

ô¿ô
My wife has not given me permission to express any opinion here

 

[jfm]

Re: Paddlewheel effect

Seems a bit odd if he was doing this on a long run, much better to alternate neutral and in gear if he wants a straight line and ultra low speed (both engines just in gear prob give you 6 knots in that boat, which is too fast for many situations obviously). Also bowthrusters are a bit crappy in terms of engineering imho, liable to bust shearpin, trip the circuit breaker, or otherwise phut out, so do not rely on them imho.

We're prob into the realms of boat quirks here, and all boats are a bit different. On ours for example, it can be made to move sideways by a combination of paddlewheel effect to move the stern sideways and bowthruster to move the bows. Or praps I'm kidding myself and it was wind.

The thing I've never understood in all this is why does paddlewheel effect happen? All that stuff about more density or grip on the deeper water at the bottom of the prop than the lower pressure water at the top pf the prop is obviously complete tosh, so why does it happen? Anyone know?

 

[tcm]

Re: Paddlewheel effect explained a bit

going fowards, the water goes back over the rudders and gives steering. But going backwards from near-stationery, the water is not moving directionally, rudders do nothing, so sideways initial impetus from props is realised by appropriate sidewaysy movement of stern. At higher reverse speed, rudder and hull *do* give steerage, so in order to make a sailboat go backwards and out into the fairway you have to give it some stick and blam along backwards at full pelt (6-7knots for a sailboat) . Agreed that an argument bout thicker water at surface must be rubbish, as force transferred anyway thru shaft.

 

[ChrisP]

Certainly agree about the judges at the show. Watched one judge (who happens to write a collum in the MBY and I believe is a Yachtmaster instructor) try a med mooring. 4 attempts and was eventually man-handled in by the other embarrased judges. Then went on to critisize the competetors in the debriefing. A fine example of "if you can't do teach it".

Back to the original thread.
Never had a bow thruster. I've usually had twin engines. I've always found that the enlightened use of crew that can throw a rope, springs and fenders have usually made short work of coming into and leaving tight moorings or adverse winds and tides. I would advocate the practice with ropes and fenders so that when the circuit breaker on the thruster decides to protest at the continued thruster use, you can fall back on "Ye Olde" method. For what its worth I've never seen a bow thruster that's half as good as driving into a solid spring. And before you sages drive on about how the crew should jump ashore rather than throw the rope, I still believe that a crew person with both feet on the deck behind a solid guard rail, is far better than watching the hapless person launching off towards a bouncing pontoon.

My advice. Grab someone that knows what they are doing. Find a flat piece of water and practice for a couple of hours. Then decide what method is best for you and the crew. (asking the crew makes them feel important and much more willing when it comes to providing the drink you just demanded).

Good Luck

ChrisP

 

[ChrisP]

Re: Paddlewheel effect explained a bit

Must agree about thicker water. Even if the density change due to temperature affected more than a few inches the effect would still be minimal.

I've always found the best way to drive singles astern is to give it a good burst astern with the rudder hard over to counteract the paddle wheel effect until the boat starts to move. Then ease the throttle until the boat starts to answer the helm. With the throttle in this position you can ease the helm until the boat travels in a straight line. You usually find that the helm will still has a portion of the "anti paddle" direction and the engine is a bit over tick over speed. You should now have reasonable control and if required a short kick ahead will sharpen the turn.

ChrisP;-)

 

[paulineb]

Re: Paddlewheel effect explained a bit

That's just what I was going to say ;-)

Pxx

 

[Deleted User YDKXO]

Bowthrusters

I would have agreed with you until I had a boat with a (properly sized) bowthruster. It does save a lot of messing around with springs and fenders especially when you're short handed and got a bolshy wife like mine. If I dont get her directly above the pontoon cleat first time, she's just as likely to flounce off and say do it yourself
You suggested that it wasnt safe to allow crew to jump ashore and I agree with you and thats where a bowthruster can help by allowing you to hold the bow against the pontoon
Having said that, you're absolutely right to say that everyone should learn how to manouevre using springs
BTW who was the YM Instructor/MBY hack?

 

[byron]

"And before you sages drive on about how the crew should jump ashore rather "

No way should anyone be allowed to jump ashore, this is the height of stupidity especially if holding a line. I can only think of one instance this can be countenanced and funnily enough it happened to me today. The berth we were putting a boat on didn't have bollards so we had to get ashore to put a line through the rings.

ô¿ô

 

[hlb]

Cris is dead right. Our method was mainly developed by SWMBO. Who's only 5ft 3in. and a bit eerr weightily challenged and nearly old. The deck is about five foot higher than the pontoon. So Flying over the guard rails and landing in a heap on the pontoon. she would probably go straight through it!! Now my SWIMBO is no acrobat. So just take a big loop of rope dangle over front. If it's an alongside mooring and especialy if theres wind blowing off. Just drive the boat nose on to the pontoon, stop with nose over the top of the pontoon to make it very easy. It's not hard to hold it within three inches, without touching. And swimbo just swings the rope a bit, to go over the cleat. Then wiz boat round on the engines. BOTH engines. One forwards and one back. Dont care if it has outdrives it will still do the job with perfect control. Even if a little slower. Just adjust throttles so the boat come round. Using the bow line as a spring to hold the front in. It's very easy even in a gale.

Have you sent off Your Stamped. SAE and cheque. Yet.

Haydn

 

[ToMo]

AND he really does exactly that - witnessed it meself!

 

[ChrisP]

Re: Bowthrusters

He writes some of the technical test articals when he's not wittering on about his own ways of doing things. Initials T.B. (Tim Bartlet) He's also the one of the ones that marks people down if they don't perform the "pontoon or bust " flying leap. I would challenge him to take part in the Thames 5 clubs rally or the ATYC competitions, but unfortunatly we'd all have retired in the time it will take him to practice enough to reach the required standard for entry (Novice).

ChrisP

 

[Deleted User YDKXO]

Talk the talk

I got the impression TB was always a closet yottie when he worked for MBY. I see he's come out now and crossed over the other side to PBO. To be fair, I always find his articles informative and interesting. Maybe its a case of talking the talk but not being able to walk the walk.

 

[byron]

Re: Bowthrusters

tee hee.

ô¿ô

 

[jfm]

Re: TB electronic guru

Ah TB......he's the one who tested for MBY the Sony Ps1, Ps2, Gameboy, Nintendo, and Dyson to see which was the best plotter. Conclusion was, none of these is at all suitable for use as a plotter, something which he could have figured out by reading the packet

 

[paulineb]

ooh jfm !

... and I thought women could be bitchy ;-)

Pxx

 

[Medskipper]

Sorry but I disagree! you CAN centre the outdrives and control the boat to a very fine degree on both engines! I could turn my 30' boat on its own axis using both engines.

Barry

 

[Deleted User YDKXO]

I used to own a Sealine S37 and you could'nt do that. You needed a lot of revs to get the boat to pivot. If the wheel was only slightly off centre the boat would just go the way the outdrive was pointing. In any case you could achieve so much more by steering as well