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Tue, June 25 2024, 02:36Login ] [ Contact Forum Admin ] [ Main index ] [ Post a new message ] [ Search | Check update time | Archives: 123456[7]89 ]


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Date Posted: - Friday - 01/ 4/08 - 2:26pm
Author: matts
Subject: Problem backing under power

Our Mariner 31 will go straight back under power with a bit of coaxing, and she definitely backs to port--but never to starboard--not even at idle speed or by rocking back and forth between neutral and reverse. Powering out of a dock is quite an adventure that usually requires bit of help from someone on the dock (to push the boat until the bow is clear of the dock).

I suspected that her prop is walking the stern to port, effectively canceling any chance to go to starboard, especially since a neighboring Mariner 40 has the same problem.
1. Are any of you having the same problem?
2. Is it possible that we have too large a prop?
3. --or--Is this simply a problem with shoal keel rigs and cannot be resolved,
4.--or-- does anyone know of some kind of method for easy backing under power for those of us who single-hand and can't find any help on the dock?

matts

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Replies:

[> backing to port -- mike Anthony, - Saturday - 01/ 5/08 - 3:17pm

Our 40 definitely backs to port as well. We turn an 18x15 prop with a 64 horse engine. However, if you are able to build a little speed go to neutral then put the wheel over. It will turn to stbd then,at least ours dows, and due to the full deep keel it will tracking that way until you change it. Of course wind and current and also effect your direction. When I purchased Tivoli the prevous owner had installed a bow thruster.. And while we have not yet hooked it up or used it, Im sure it would help, probably help us tacking in lite winds as well.

Good Luck
Mike & Paula
S/V Tivoli


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[> [> Problem backing under power -- matts, - Saturday - 01/ 5/08 - 3:40pm

Thanks, Mike. I've tried the reverse to neutral trick, but since our entry channel is rather narrow, backing is still pretty risky. Your prop size is of interest, though. I'll have the diver check ours the next time he scrubs the bottom.

matts


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[> [> [> Prop -- Mike M-40 #61, - Sunday - 01/ 6/08 - 2:26pm

You might have your diver clean your prop while doing the bottom. An unpolised prop is only 80% efficient.


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[> The Keel -- Randall, Murre, M31, - Sunday - 01/ 6/08 - 11:40pm

I think poor going astern steerage is in the nature of the keel type in the same way that tacking under some conditions can be a challenge in our boats.

Cunliffe once commented of Hirta, his large gaff cutter, that reverse did little more than make the boat bridle, and only sometimes did it slow her down.

I remember being quite amazed by a Frers 39 (8 foot draft, fin) I helped to deliver from Hawaii back to BC. We landed at the Tofino gas dock late at night and next day the harbor master asked us to move to the opposite side of the finger. The owner went reverse off the dock, reverse around the finger, and reverse into the new slot like he was driving a fork lift. Murre wouldn’t do that in a million years.

Murre has a 12 x 6 prop now but had a 13 x 8 for a couple years and I don’t remember a significant difference in going astern characteristics. I will admit I don’t do much going astern. We’re in our third Marina w/this boat, and I’ve tended to plan the slip I rent based on the boat’s (or at least the skipper’s) abilities.

You might check the size of your rudder. Most Mariners (I think) have a barn door of a thing—Murre does. Some I’ve seen have a smaller, more rounded affair, which might be less effective when backing the boat down.

RR


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[> rudder design -- Mike M-40 #61, - Monday - 01/ 7/08 - 10:58am

During conversations with Ida Sailor about building a new rudder for my boat, I have learned the Mariners have design flaws in the present rudder. The width of the hull at trailing edge far exceeds the width of the existing rudder and causes inefficiency. Also the distance between the hulls trailing edge and leading edge ot the rudder also causes inefficiency. Then there is the flat shape of the rudder which causes less steerage control at slow speeds. They suggested a modern design rudder which eliminates the area between the leading edge of rudder and the hulls trailing edge. Also, increase the thickness of the rudder with wing shape design. Their estimate for new rudder was approximately $3000.


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[> [> rudder design -- matts, - Monday - 01/ 7/08 - 3:14pm

Thanks, Mike.
$3,000 sounds swell and a likely solution, but I fear that it is a bit over the boating budget--at least for the (very long) time. I think I'll follow Randall's lead and put us on the waiting list for the other side of the dock, which is reserved for 40 footers and opens on the bay. Perhaps the increase in room and board is worth the extra margin of safety. In any case, it will let me back "Scandia" out of her dock for at least a quarter mile while I run in merry reverse circles.

Ought to keep the locals amused and puzzled about my true intent!

matts


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