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Old 04-12-2013, 20:47   #1
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Help! Transitioning from sail to twin screws

In three days I will be in the cockpit of a 2003 Campion Allante 925, (30' with twin 5.7 volvos.

Question: What is a trim tab again? Seriously, what do I need to know about handling one of these things, getting into my slip (calm conditions but near freezng).

5 tons of cruiser here and I am more than a little intimidated. In the last 3 years I have done the Power Squadron Course, sailed the Pacific Northwest for hundreds of days at sea, (single handling, literally, can't get enough). but then someone came along and made me an offer I couldn't resist so I sold the Hunter 28. Then this wonderful deal came up and all of a sudden, I am a "Stink Potter""

Looking forward to it!
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Old 04-12-2013, 21:03   #2
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Re: Help! Transitioning from sail to twin screws

Does Co-op have a fuel barge in Vancouver. You are going to need the help.
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Old 04-12-2013, 21:17   #3
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Re: Help! Transitioning from sail to twin screws

Ever driven a Bobcat on ice with wind?
Forget the helm, just vector the thing with throttles and gearshift.
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Old 04-12-2013, 23:29   #4
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Re: Help! Transitioning from sail to twin screws

I gather even a large 10,000 lb power boat gets blown around by the wind worse than my Hunter 28?
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Old 04-12-2013, 23:31   #5
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Re: Help! Transitioning from sail to twin screws

Quote:
Originally Posted by DeepFrz View Post
Does Co-op have a fuel barge in Vancouver. You are going to need the help.
My Hunter was getting 1.2 liters per hour, this one gets 18 US gallons per hour travelling 5 times as fast at 25 knots. OUCH!
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Old 05-12-2013, 00:18   #6
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Re: Help! Transitioning from sail to twin screws

The trim tabs are basically horizontal rudders. Used to adjust bring the bow down at low planing speeds, or can be used to adjust heel due to an uneven load.

Having twins, docking will be easier than with your Hunter after a bit of practice. You'll be able to rotate in your own length. Initially, don't use the helm wheel; just drive her like a tank, bumping each prop in/out of gear.

Using forward and reverse to make your turns with the reverse prop just idling and slightly more throttle on the forward rotating prop.
As your skill level increases, you can use the rudders to fine tune your docking, but initially it may just confuse the issue.

Play around by docking alongside a mooring buoy to get the hang of it.
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Old 05-12-2013, 00:43   #7
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Contact your local power squadron and see if there is a member experienced operating your type of boat willing to ride along. Better idea is to hire a licensed captain for 2-3 hours to train you in twin screw operation. That would be cheaper than repairing potential scratch and dents while you are practicing.
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Old 05-12-2013, 04:46   #8
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Re: Help! Transitioning from sail to twin screws

When you see someone in your area that really handles a boat well ask him to take you for a ride in your boat. He will be flattered and you will learn a lot in a short time.
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Old 05-12-2013, 06:28   #9
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Re: Help! Transitioning from sail to twin screws

Trim tabs are only functional above or near planing speeds, at displacement speeds they do nothing. For most boats you put the tabs full down when accelerating onto plane, then once on plane they are adjusted for proper ride (they are real good at stopping porpoising).
They are of course real good for when your passengers all go to one side of the boat for whatever reason.
Trim tabs are wonderful on a planing hull, position displays that report their positions are great. I don't have those displays on my current boat, and I miss them

You'll be fine seamanship, is seamanship, common sense, common sense
Power boats are easy, it's their major appeal
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Old 05-12-2013, 09:00   #10
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Re: Help! Transitioning from sail to twin screws

^^

So approx. 54 times the fuel for 5 times the speed. Is my math right? Of course most folks don't go screaming around at top speed. Unless of course their name is Getty.

I used to have a car that was something like that...
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Old 05-12-2013, 09:59   #11
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Re: Help! Transitioning from sail to twin screws

Thanks for the help all of you, I have been watching these twin screw manouvers on YouTube, looks like fun.

25 knots is cruising not top speed which is 55 mph at 18.8 gallons per hour.
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Old 05-12-2013, 10:06   #12
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Re: Help! Transitioning from sail to twin screws

It's a differnt world for handling for sure. Twins will help. A sailboat with a fin keel pivots more or less around the keel. The cruiser will swing wider when you turn... remember that in marinas!
When getting up on plane have the trim tabs in the up position, once you get nearing a plane trim them down until the bow comes down and the boat stops laboring. then ease them up until the bow attitude is what you want. You may find the boat heels due to engine torque... you can adjust one tab or the other to get rid of this. Yo wont likely have much of this with dual engines though.
Have fun... it'll be fun getting to your favorite anchorage in 1.5 hours when the sailboat took all day!
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Old 05-12-2013, 10:10   #13
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Re: Help! Transitioning from sail to twin screws

Thanks, I wondered if applying the tabs before accelerating wouldn't make the boat work harder than necessary, it makes sense to me to apply them when almost planing.

They say the tabs help fuel economy but don't they slow the boat when lifting the stern?
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Old 05-12-2013, 11:34   #14
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Re: Help! Transitioning from sail to twin screws

You'll find the sweet spot.... you can feel it. I use as little tab as possible once up on plane. I just start easing the tabs down as the boat starts to labor to get on plane.
Another word of caution, dont trust your fuel gauge. Most tanks are V bottom shaped but the gauging system doesnt account for that. So the first half of the tank disappears slow, but the last half disappears fast! I just try to keep the tank full at every opportunity if using my gas eater!
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Old 05-12-2013, 11:52   #15
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Every boat I've had will drop the bow and hence get on plane quicker with full tabs. My current boat with water tank and full fuel four people and dive gear won't plane at all without the tabs down. She will just point her nose high and hang there. It takes the tabs to push her over on plane.
If your only burning 18 GPH at 55 mph that's incredible good fuel burn. I'm smaller and a single four stroke outboard but burn over 20 GPH at 30 kts.
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