SailNet Community banner
  • SailNet is a forum community dedicated to Sailing enthusiasts. Come join the discussion about sailing, modifications, classifieds, troubleshooting, repairs, reviews, maintenance, and more!

Backing up (or not)

8K views 43 replies 27 participants last post by  Seaduction 
#1 ·
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?
 
See less See more
#2 ·
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.
 
#3 ·
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.
 
#4 ·
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?
 
#42 ·
Unless I get attacked by a Sharktopus, backing out of my slip at the beginning of the trip is usually the most stressful part of the voyage. My boat is heavy 30,000lbs, has a 6' full keel, an underpowered engine (36HP), and a prop in an apeture.



I no longer find her unpredictable in reverse at all. She is in fact, very predictable. The secret, I have found, is in accepting what she can and can not do, and estimating the forces that will be at work before untying.

I'll try and explain. My pivot point is located just forward of my wheel, where the mizzen mast is. That means that all windage forward of that will try and blow the bow off. In fact, there is so much forward windage, that my boat apparently heaves to with a FULL mizzen only, with the 150sqft sail and the forward part of the boat's windage being about equal. So, 40ft of boat, including my bowsprit (which is at the end of the lever) act like a unidirectional-wind-powered bow-thruster. I also know that my LH prop causes the boat to strongly prop walk to starboard. I also know that my rudder will not overcome much opposing wind, and will barely keep up with prop walk if there is no wind.

Knowing these things, and knowing that I can't overcome them, I have to work with them. Before I untie I look at my masthead wind indicator and feel the strength of the wind. I know the wind blowing the bow one way or the other will be the biggest actor. Once I know that, check for current, and account for prop walk. I kind of imagine all these vectors in my head and decide how I can affect them and make a plan.

Often the wind blows from my starboard side. This will blow the bow to port. The prop walk will compound the problem. If I "try" to overcome this in reverse with the rudder, I'll be making an insurance claim. I HAVE to accept the limitations of my craft and not pretend that if I just twist harder on the wheel she'll go.

So, I do something else, like shorten up the starboard bow line, release all others, and release it last so I start backing up crooked, and straighten out as I go. Or I use a burst of forward with starboard rudder to straighten out, then resume backing.

Basically, I know the forces that will act in opposition or unison to affect my steering, and I know and accept that the rudder is a small, not a large player in the overall plan. I imagine the vectors, make a plan, untie my lines and see if I was right.

I hope my long-winded ramble made some sense and helped somewhat....

MedSailor
 
#5 ·
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.
 
#6 ·
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.
 
#22 ·
I have a Maxprop so in theory I have no prop wash - in practice I have minimal prop wash.
I have a Maxprop on our Hunter 40. But I'm new to the boat and the prop and don't really understand exactly what a Maxprop does.

What I DO know is that the boat does incredibly well in reverse - with very, very little prop walk. I had to move it to our new slip a few weeks ago (my first time really handling the boat in close quarters). I was extremely nervous - as the boat felt like an aircraft carrier compared to my previous C27.

To make things more difficult, I had to back it in for my shorepower cords to reach the cockpit. And to make things even more difficult, I had wind blowing directly into the slip.

I asked the broker who sold me the boat - a seriously good guy and veteran sailor in the area named Pat - to help me as I didn't want to try it with just the boys aboard. I did just fine backing it out of the slip at the boat yard that re-did my rigging. Piece of cake.

When we got to the new slip, he walked me through what I needed to do - which was come into the fairway pretty tight to our dock (leeward), then right at our slip, turn hard to port to get the bow through the wind and swing the stern to align with the slip - then back down quickly.

I tried this 5-6 times (Pat's a very patient guy) and finally got the stern going into the slip, but I was always too timid with the initial turn which allowed the bow to blow off to starboard. So even though I got good initial alignment with the stern, I always got a little too sideways to reverse in cleanly. Pat made me keep trying. I was able to control the boat in the fairway and keep us away from the hard bits as we kept at it.

Long story short...at my request, Pat finally showed me how. But he warned me that he was already a couple of Manhattans into the evening. Regardless, he did a great job - still getting us a bit sideways as the bow blew off, and crunching my life ring a bit - but we got her in.

It made me feel good to see that it's NEVER that easy - even with tons of experience. And it made me feel REALLY good when he complimented me on my boat handling. I'm feeling a bit more confident for the next try.
 
#7 ·
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.
 
#9 ·
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.
 
#31 ·
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.
Do you have a reference to that article.
I'm not sure I understand the arm thing you mentioned but is sounds like it is the answer I'm looking for.

IE what is the arm why is it a problem in reverse but not forward?
 
#10 ·
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.
 
#11 · (Edited)
My boat is completely uncontrollable in reverse. I've tried with another sailor and experimented in calm, flat water. Even at speed, the boat oscillates slowly between turning to port or to starboard. regardless of what we did with the rudder.

I have to walk my boat out and pray that the wind does not blow her in the wrong direction before I can get her to move forward and gain control.
 
#12 ·
As KILLARNEY said, give some throttle and then put it in neutral. Without going into the design aspect of WHY (BobP is much better at this than I will ever be) some boats just don't handle well in reverse. The prop walk is just overpowering. Key is to get the boat moving in reverse, take it out of gear, thus removing the propwalk and now you have water flowing over the rudder giving you steerage. Assuming you have room, position yourself so you can get up a head of steam and allow for the prop walk, then put it in neutral and hope you have enough momentum to steer yourself into the slip.

And yes the Bristol 32 is a gorgeous boat albeit smallish.
 
#13 ·
BRISTOL 32 sailboat specifications and details on sailboatdata.com

Is your B 32' Atomic 4 or diesel powered?

My Tartan 27' has a similar shaped hull and behaves in reverse as described here; unpredictably. So yes, similarly shaped hulls behave similarly.

I have found that if we start out by pushing the boat out of a slip and establishing a direction that when reverse is engaged the boat will likely continue in the direction it is already moving. The boat does not have to be moving fast before reverse is engaged, it just has to be moving. If you have to allow the propeller and rudder to establish the direction of movement then all bets are off which way it will pull, because it wont back up in a straight line.
 
#14 ·
I have the same issue with my Bristol 35.5. I will have to practice in reverse gear, rev up, neutral, adjust rudder but usually the stress gets me and I end up going back into foward to correct. I badly need a parking lesson as I will soon be moving my boat to a marina instead a 2 boat private slip.
 
#17 ·
Same on the Pearson 35 ... similar longer skeg keel, barn door rudder with the prop high and protected. Reverse is a mere suggestion. Although, I find that at slower speeds the boat is increasing uncontrolable/predictable in reverse. Unfortunately, slow is what is needed as you near docks. If you feel that the engine is underpowered, then I think that would add to the controlability.

I've gone to out into the open water and practiced before. After four to five years on this boat, I don't feel my "reverse" skills have improved much.
 
#18 ·
Anyone for dropping a trolling motor on the front of the boat to use as a bow thruster? Seems like for a few hundred bucks and some creativity, you should be able to solve the problem. They seem to go cheap enough on Ebay, that it would be worth a try.
 
#19 ·
I've thought of doing just that, only off the transom. My boat, a Cal 2-27, has a longish (not deepish) fin keel and a spade rudder. And our marina has pretty narrow channels. To complicate things even further, the wind usually blows about 90˚ to our slip, from the direction we want to eventually go when leaving. When not exactly 90˚ to the slip, it blows the boat slightly back toward the dock. So, as I back out I want the stern to swing to Port, but the wind catches the bow and forces it to Port. If the wind is light, the rudder usually turns the boat fast enough to win the struggle. But once the wind pipes up a bit the effect of the rudder gets cancelled by the wind pushing the bow and I can't turn fast enough. To avoid backing into the boats on the next dock I have to stop backing and let the boat slip sideways up the channel until I get to the dock at the end and then man-handle the boat until she's pointing in the right direction. In such a situation, a trolling motor on the transom would come in very handy.
 
#20 ·
I have a long keel contiguous with the rudder and with a cut-away forefoot; therfore, I'm among those with the least backing performance. The best stategy for me is not one answer. If it's backing out of the slip, then the answer is warping on pilings and spring lines. If it's backing into the slip, the answer is positioning close to the slip and then turning clockwise with the helm hard to starboard and "goosing" the throttle in forward and reverse. If it's backing with the bow into current then it's not reverse at all, but lightly in forward and neutral while ferrying port or starboard. If it's wind then the answer is to place the bow in a position that, while you are backing, the wind is turning the bow to your favor. Final answer,- the plan depends on the condition!
 
#23 ·
To the OP, You cant surf when there are no waves and you cant sail when there is no wind so why would your try and make your boat do something it physically cant. Learn the characteristics of your boat and always be one step ahead. Tip, forget about your rudder in reverse, the prop has more effect that the rudder, use the prop walk to your advantage.
 
#29 ·
I'm trying to figure out what the boat will do because it is so different from other boats.
In all other boats I have operated I could count on the the prop walk at low speed before the the speed was sufficient to make the rudder work.

This boat has surprised me on some occasions. Instead of prop-walking to port in reverse as would be expected it has moved starboard.
Sometime port sometimes starboard.

It obviously has a cause it it not magic. I'm thinking that the reason is that the prop-walk effect is overwhelmed by the currents effect on the keel and in one case topside windage.
 
#26 ·
On my Edel 22' I turn the outboard when in reverse and keep the tiller str8.

I think something disconnects the tiller whenever the Honda is in "R"....I cannot see that connection but I will find it one day.

or perhaps my brain's RAM is overloaded unless it is in "F"
 
#27 ·
Smack, I had a Maxprop on my last boat, a Niagara 35 with longish fin keel and big spade rudder. In general there was very little prop walk but I learned that if you wanted some, eg to pull the stern into a dock you could goose it in reverse for just a second or two and you would get a quick jump in the desired direction - you did choose the dock to allow this of course?
 
#33 ·
Dave:
That article appears in the July? Aug issue 2010.

"IE what is the arm why is it a problem in reverse but not forward? "

Good question. I'll take a stab at answering it. I think the key is that the center of pressure on the hull moves. When in reverse the hull C of P moves well aft. In forward it moves well foward. This would be consistent with any foil and the keel foil shape is backwards in reverse, i.e. sharp leading edge, making it move even more aft. I think that's it.
 
#34 ·
I've always looked at it like this:

When moving forward a keel with an attached rudder acts like an airplane wing with an aileron. The net effect on the lift of the wing is in the opposite direction of the movement of the aileron; the aileron goes up the wing goes down, and visa-versa. Now, turn the plane 90˚ so that the wing is pointing straight down and you essentially have a keel with an attached rudder. The rudder goes to the right the lift is increased to the left, and visa-versa.

BUT, reverse the flow and what do you have? The "aileron" is now acting more like a leading edge flap (and there's a good reason they put the ailerons on the trailing edge of the foil). It might reduce the stall speed a bit (that's why planes have leading edge flaps), and increase the drag of the foil, but it won't do much for the lift of the foil (wing or keel; OK, it may increase the lift a bit, but not as much as an aileron would). So, when backing a boat with a rudder attached to the keel the "control surface" is basically on the wrong edge of the foil.

A spade rudder works because moving it from side to side has the same effect as changing the "angle of attack" of an airplane wing. Increase the angle of attack and lift is increased, at least until the stall angle is reached. With a spade rudder such lift swings the stern right of left, and Voila! The distance from the center of pressure may also come into play, but the important dynamic is the effect of the control surface on lift (in my humble biomechanical opinion).
 
#35 · (Edited)
Hmmmmm,,,,,,I'll buy that. I need to ponder it a bit but it sounds good to me.
I think you may have part of the answer but I still think that the center of pressure on the keel plays a big roll. If it were static you would still have the same turning arm in reverse. I think having the control surface on the leading edge also may be the reason the C of P moves aft.
 
#37 · (Edited)
Another way to look at this is to think about what happens to the flow over the keel in the forward and reverse directions. Let's start with the boat moving forward; the flow is (or at least should be) laminar all along the keel and its attached rudder. Now, turn the rudder a bit to Port and the flow should stay pretty much laminar as long as it isn't cranked too far. There may be a few vortices being shed off of the trailing edge of the rudder, but these will only increase drag without having much of an impact on lift. So, turn the rudder to Port, lift increases on the Starboard side of the keel, the stern swings to Starboard and the bow turns to Port.

What happens when the flow is reversed (i.e., the boat is backing)? With the rudder centered the flow is again laminar. The maximum chord (the thickest part of the keel) is probably in the wrong place, but let's not worry about that for now. OK, turn the rudder to Port again and what happens to the flow? Now the edge of the rudder is the first thing the flow "sees" as it impacts the keel. Since this edge is relatively sharp (compared to the forward edge of the keel) the flow separates right at the leading edge (or what is the leading edge while backing). This causes vortices at slow speed and turbulence as the speed increases, in this case all along the Port side of the keel. This pretty much ruins any lift the keel might otherwise generate (i.e., the keel is "stalled"), and directional control is more or less nonexistent.
 
  • Like
Reactions: SchockT
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top