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  #11  
Old 09-17-2013
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Re: Baba 30 Maneuvering

This doesn't answer the OPs question at all, but, being on a pin simplifies things a lot. When I get underway, I wait for the boat to swing in the direction I want to leave, then drop the mooring line. The bow swings off, and I go. If I need to enter or leave a slip, then all bets are off.
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  #12  
Old 09-17-2013
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Re: Baba 30 Maneuvering



Pssst...... Wanna buy a bowthruster?
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  #13  
Old 09-17-2013
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Re: Baba 30 Maneuvering

Any chance of getting one of our designers to give us some guidance here.

What I would like to know is weather a boat with a keel configuration like a Bristol 32 should be expected to be more unmannerly in reverse than a Allmond 31.

I guessing that the prop being in a aperture makes a difference because in reverse as soon as the rudder is off center the prop is starved of water.

Also it looks to me that the location of the turning balance point in the Bristol will be a little further back which will make the tracking more tender and subject to wind and current.

That being said I trust math more than my eyes sometimes and would like to know how the numbers work out.

Bob P, Jeff_h anyone else with the skills to calculate this.
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  #14  
Old 09-18-2013
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Re: Baba 30 Maneuvering

Dave:
Not sure what you are asking me.
We all wrestle with full keel boats in reverse.
Bob P.
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Old 09-18-2013
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Re: Baba 30 Maneuvering

Quote:
Originally Posted by bobperry View Post
Dave:
Not sure what you are asking me.
We all wrestle with full keel boats in reverse.
Bob P.
My thoughts on backing up:
1. 49% influenced by current
2. 49% influenced by wind
3. 2% influenced by rudder position
MY qualifications: backing up my Island Packet since 1998.
(I'm a firm believer in using spring lines to accomplish desired outcome.)
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  #16  
Old 09-18-2013
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Re: Baba 30 Maneuvering

Quote:
Originally Posted by bobperry View Post
Dave:
Not sure what you are asking me.
We all wrestle with full keel boats in reverse.
Bob P.
Yes I'm finding that out the hard way.

I've attached the underwater profiles of two boats I have had experience on the summer. An Allmond 31 and a Bristol 32

They are both a handfull in reverse compared to a fin keel balanced spade rudder.

It appears to me with my limited experience that the Bristol is is noticeably more difficult in reverse than the Allmond.

To the extent that if you have the Allmond pretty much figured out and know what you can and can't do and basically can handle it, if you jump on the Bristol much of what you thought you knew will not work.

I know you know a lot of the science between the different hull shapes and I'm interested in knowing if my analysis makes sense based on hull shape of if other factors, may be influencing my gut level feel.
Attached Thumbnails
Baba 30 Maneuvering-allmand_31_drawing.jpg   Baba 30 Maneuvering-bristol_32-02857.jpg  
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Old 09-18-2013
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Re: Baba 30 Maneuvering

Wow Dave.
I have to leave now for the dojo where I wil beat up little old ladies.
I'll try to digest you data tomorrow. Nice work pal.
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  #18  
Old 09-18-2013
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Re: Baba 30 Maneuvering

The Bristol, with its keel-hung rudder, will always be a PITA to control in reverse.
See HERE.
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Old 09-19-2013
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Re: Baba 30 Maneuvering

Quote:
Originally Posted by SlowButSteady View Post
The Bristol, with its keel-hung rudder, will always be a PITA to control in reverse.
See HERE.
I'm thinking that if you limit yourself to only about 5 -10 degrees when in reverse the rudder may have some effect albeit exaggerated.

IOW once you get past 10 degrees nothing good will happen.
between 2 and 9 degrees it might actually have some either minor or exaggerated positive effect depending on what the much more important wind and current is doing.

I would love to be able to tank test something like this.
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Last edited by davidpm; 09-19-2013 at 12:47 AM.
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Old 09-19-2013
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Re: Baba 30 Maneuvering

I have a Ty37 with similar underwater geometry as the Baba30. I dont have a problem backing up; although such maneuvering requires quite a bit of forethought.

The problems are propeller tip clearance in the aperture resulting in large 'prop walk', which is very useful if you master 'prop walk'.

For docking in reverse, I usually initially set the boat at 45 degrees to the dock with the dock to port, apply massive short bursts of reverse rpm which turn the boat stern to port. Rudder is usually held over to starboard and 'ready' to apply quick burst of forward rpm to 'straighten' or correct the boat if the reverse travel 'gets out of hand'. Once 'underway' in reverse, engine is brought to idle speed with the transmission in neutral and the boat slowly drifting astern, using the flow of water across the rudder to 'slightly' steer and by using either mini-bursts of forward or reverse (propwalk) to steer. You cant be 'timid' with backing and filling, you really have to be aggressive ... and have rub rails.
Youre simply NOT going to back such a boat into a slip/dock if that dock is to starboard, it HAS to be to port, and initially at about a 45° angle to port. Prop walk with a right handed prop will only take the stern or bow 'to port' and thats why you 'start' with the boat at ~45° to a 'portside' dock.

The 'secret' to back a full keeler with an aperture is to first master 'backing and filling' (aka: pivot turn), remembering that such boats will *only turn the stern to port* when backing or *turn the bow to port* (stern to stb) when prop walking forward .... if you want to go to stb, in reverse either drift at speed with the rudder held to stb; or, if wanting to go forward to stb have the rudder set to stb and 'blast' some prop wash against it, the 'blast' against the cocked rudder will steer the boat. Be aggressive with the prop walk but idle down during the 'drift' in reverse. Also, practice your pivot turns (turning 360 within one boatlength), and master backing 'straight back' in open water BEFORE you start attempting to back into a slip. Such boats with righthand props simply will not turn to stb, either in forward or reverse when at low speeds .... master prop walk and pivot turns (clockwise and counterclockwise) if you want relatively hassle free docking to aft backing down in a relatively straight line.
For such boats you WANT lots of 'prop walk' ... I wouldnt know how to back down a full keeler with its prop in an aperture that didnt have 'prop walk'. Usually the rudder is simply forgotten (held to stb) and you steer solely by forward or reverse 'prop walk' when making sternway.

Rx: 'master' backing & filling / pivot turns and do so 'aggressively' before you attempt to go sternways into a slip/dock.

Last edited by RichH; 09-19-2013 at 10:49 AM.
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