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Old 07-14-2013
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Backing up (or not)

I have been sailing a Bristol 32 (with the board up) this summer so far.

I find that it's behavior is reverse is very sluggish and unpredictable.

I noticed a comment in a Vigor book that the Cape Dory was sluggish and unpredictable in reverse. I noticed that the underwater profile of both boats is practically identical.

The behavior seems to be related to four things:
1. Very low power in reverse even with a three blade prop.
2. Barn door rudder so when the rudder bites in reverse it is significant.
3. The cut-away fore-foot keel seems to over-whelm any other forces like prop-walk or astern propulsion.

The end result is a boat where it is hard to predict its behavior in reverse.

So I have two questions for those in the know.

1. Other than just practicing a lot any tips on backing up this boat?

2. Will every boat that has this same or similar keel shape behave similarly?
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Old 07-14-2013
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Re: Backing up (or not)

Full keel boats are notorious for backing like unpredictable slugs. Having the rudder hung on a skeg helps, but only boats with a spade rudder are truly well mannered in reverse.
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Old 07-15-2013
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Re: Backing up (or not)

Yes, my boat doesn't have a "full" keel but it is a long not-so-deep keel and a skeg hung rudder and she is a mutha to reverse, goes pretty much wherever she wants until there is a considerable boat speed.

Compared to my mate's Beneteau 40 with spade rudder and fin keel the boat is almost as responsive in reverse as it is going forward.
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Old 07-15-2013
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Re: Backing up (or not)

Someone out their must have a full/cutaway keel boat for a lot of years and has figured out the trick of at least predicting it's behavior.
Where are you?
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Old 07-15-2013
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Re: Backing up (or not)

We have a longish keel (to house the centerboard) and backing up can be an adventure. One thing to try, get the boat moving and then put it into neutral. It should steer much better in neutral. The idea is to go into and out of gear. Also if your boat like ours it will steer more reliably in one direction than another and you consider this when choosing docks and how to approach piers and the like.
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Old 07-15-2013
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Re: Backing up (or not)

I've had the fun of re-learning how to back up. The Gemini had a drive leg that turned with the rudder so it was easy-peasy, sort of like driving a car.

The Irwin has a 2/3 full keel (quesstimate) that is all of 18 inches down from the hull and a foot thick - not exactly a blade. I had to get over my chicken nerves and decide to MOVE the boat then turn. Not easy in a tight channel at a marina.
I've found that if I goose a 2/3 throttle for a second then back to idle the boat gets moving and stays moving fairly straight. I have a Maxprop so in theory I have no prop wash - in practice I have minimal prop wash.
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Old 07-15-2013
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Re: Backing up (or not)

My auxiliary sailboats have all had spade rudders. Some back better than others. Invariably I have prop-walk that prevents backing to starboard; so the answer has been get a head of steam up straight back and cut down to idle, out of gear, and THEN turn the wheel to swing the transom to starboard. This works fine.

In a tight channel the propwalk is actually handy for a bootlegger's turn (in one boat length/spin on the keep's axis). Power in, wheel hard stbd, at 70-90° back the wheel and power in reverse, at 160-180° wheel back over and power forward - out the way you came.

Gets people standing on their transoms when you do this between piers in a marina.

Always remember that, unlike a car, a boat pivots on the keel. Boats are like aircraft - they rotate on a central point. And you seldom see anyone backing an airplane in flight.

A friend of mine had a beautiful Albert Strange designed sailboat with a keel mounted rudder and offset propshaft; but not offset so much as to allow the prop to fully avoid the rudder when hard over. Reverse was an imaginary concept. He had to do an 18-point turn to regain his slip.
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Old 07-15-2013
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Re: Backing up (or not)

Quote:
Originally Posted by davidpm View Post
I have been sailing a Bristol 32 (with the board up) this summer so far.
How do you like the boat overall? It is one of the boats high up on my list of possible candidates to purchase.
Do not mean to hijack the thread...
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Old 07-15-2013
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Re: Backing up (or not)

I wrote an indepth article for GOB on rudders in the July/ Aug 2010 issue. I explain why full keel boats are "challenged" in reverse. It has nothing to do with how much the keel is cut away forward. It has everything to do with how far the keel goes aft. The arm between the center of pressure of the rudder and the center of pressure on the hull in reverse is just too short to give the rudder the upper hand. The more you eliminate keel aft and move it forward, i.e. fin keel, the better the boat will back up. The best boats in reverse are modern racing boats with big spade rudders and high aspect ratio fin keels.
davidpm and Seaduction like this.
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Old 07-15-2013
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Re: Backing up (or not)

Sorry David but my A35 keel slung rudder makes backing down as unpredictable as has been described. Without a good head of steam, going in reverse is a crap shoot. My only solution is to avoid getting into situations where backing in reverse is required. There are really not many situations where it makes a lot of difference but I avoid having to back into tight dock spaces if possible.
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