Ball sizes

We have only used traditional fenders to protect our boat, but the consensus is that ball fenders are superior in most ways, and particularly in locks. We are in the market for ball finders as we aspire to spend a lot of time in locks. Question is, what size?

The Mariner 37 (and Helmsman 38) hull begins its curve toward the bow right about in the middle of the length. We tie alongside a dock with padded posts which means the hull is 9 inches from the dock at rest. That same 9 inch distance is maintained from stern to the bottom of the steps leading to the flybridge. The railing offers convenient spots for hanging fenders at the bottom of the flybridge steps and again forward at the bottom of the steps leading to the bow, but the distance from the dock to the hull at that forward position is 20 inches.



Understanding that the posts won't be there in a lock or other such structures, would 12 inch balls in the two further aft locations be sufficient to allow compression and protection, and would a 24 inch ball be right for the forward location? What sizes do you guys use?

On my boat with a somewhat flared hull, I carry both 12" and 18" balls in addition to our 10" cylinder fenders. We use the cylinders most of the time as they're in nice covers and aren't as sensitive to height adjustment, plus they don't push the boat as far off the dock for easier boarding when the extra distance or cushion isn't needed. But when we need something bigger, or if we're in a lock or against a concrete wall we pull out the balls.

For locks, we typically use the 12" balls tucked up just below the gunwale and then an 18" ball forward and 1 aft just above the water (no need to adjust in a lock that fills close to the top and it'll keep the boat off a wall of any height even if the boat rolls a bit due to water flow in a lock or anything). In other scenarios we'll use the balls in whatever combo works best.

My hull has a similar curve (and the curve starts a little sooner at the waterline than at the deck, so flare increases towards the bow), but mine also tapers in slightly from the widest point to the stern. So just sizing fenders isn't the ideal way to get it to sit as desired against a dock, you end up having to pay attention to how lines are tied. Typically the 2 aft-most fenders are the ones with the most dock contact as that's the part of the boat that needs to be parallel to the dock for boarding (the centerline of our boat is typically pointed slightly away from the dock with everything positioned well).

Go with the largest ones that you can store. You will come across situations that need bigger than you have imagined. I have never said that I wish my fenders were smaller but many times I have wished they were larger. We use the round fenders in locks but the cylinder fenders just about everywhere else.

I found that a combination is best. Cylinders starting at the stern and round as you go forward (one or two), starting at the curve. I think you would want a 24 round near the bow. One lesson I learned going through the locks-those nice fender covers get torn up going through locks. They get pinched against the wall. If the wall goes up and down in the locks, not a big issue, but if the boat slides up and down against the wall in the locks, the covers get torn up.

Yup, no fender covers in locks.

Comodave said:

Go with the largest ones that you can store. You will come across situations that need bigger than you have imagined. I have never said that I wish my fenders were smaller but many times I have wished they were larger. We use the round fenders in locks but the cylinder fenders just about everywhere else.

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Speaking of storage, balls can be pretty easily deflated for long-term storage. A bike pump and needle are handy for this.

Jeff F said:

Speaking of storage, balls can be pretty easily deflated for long-term storage. A bike pump and needle are handy for this.

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Agreed. We have enough space under the forward cabin to store the 12" balls inflated, but not the 18" ones so those get deflated if they won't be used again soon.

We just leave the big ball fenders at home if we aren’t going to be locking.

HeadedToTexas said:

We have only used traditional fenders to protect our boat, but the consensus is that ball fenders are superior in most ways, and particularly in locks. We are in the market for ball finders as we aspire to spend a lot of time in locks. Question is, what size?

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Can't advise, relative to your boat, but I can tell you what we take into account and what we've done about it. Not all about locking, per se, but some applies... as it also would to securing for storms.

Our boat's beam at stern is smaller than beam at mid-ship, so if we dock side-to and with our fore/aft centerline parallel with the dock... we can't get on and off at the stern (our only logical option). That in turn means we almost always dock so our keel is a foot or two off parallel with the dock, and the bow is a foot or two further away from the dock. Looks goofy, but...

Our normal fender pattern, especially at floating docks, is three 10.5" cylinders hung vertically, plus one 8" cylinder hung vertically right at the stern. Latter lets us get on and off a bit more gracefully than would a 10" tube at that location.

But then for storm tie-ups, and for locks, we bag the 8" stern cylinder... change that to a 17" buoy (A3) at the stern, and a 20" (A4) buoy nearer the bow, just ahead of the curve. Those sequential diameters -- 20, 10.5, 10.5, 10.5, 17 -- mate best with our hull curvature.

We actually have six of the 10.5" cylinders, and when underway we almost always leave 3 on both sides, immediately deployable on one side or the other by just kicking them over the rail... and then we move the A3 and A4 from side to side as necessary as we approach a dock or lock.

We also own a 27" buoy (A5) and our intent was to schlepp that back and forth as required too... but it's too heavy for The Admiral... so on a trip it mostly stays deflated... but remains available for storm situations.

And now... we also own an inflatable fender, 18" x 36", meant for additional protection during storms. Not tested yet, not sure the fabric would stand up to locking. OTOH, it's very lightweight, deflates to smaller than our 27" buoy, and easily stowed... so I have hopes it'll be a useful addition to our fender inventory.

-Chris

Great stuff. Thanks guys.

20" or bigger. The larger ones also have enough weight to keep them from walking up.

Another thing to consider is a hard landing. If you consider the force of a boat being pushed to the wall by wind, a wave, or a boat wake, the larger the area in contact with the boat and the wall, the more gentle the impact. Consider a 12" ball with a contact area of an 8" circle. The area is about 50 square inches. A 20" ball with a contact area of a 16" circle, will have a contact area of 200 square inches. The force would be the same but the 20" ball will be far more gentle. There are also situations where the smaller ball may not keep your boat from getting lock rash.

Some locks have ladders and hooks recessed in the wall. Big balls pass over them. Smaller balls can get hung up and break the deploying line.

Ted

O C Diver said:

Another thing to consider is a hard landing. If you consider the force of a boat being pushed to the wall by wind, a wave, or a boat wake, the larger the area in contact with the boat and the wall, the more gentle the impact. Consider a 12" ball with a contact area of an 8" circle. The area is about 50 square inches. A 20" ball with a contact area of a 16" circle, will have a contact area of 200 square inches. The force would be the same but the 20" ball will be far more gentle. There are also situations where the smaller ball may not keep your boat from getting lock rash.

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That also points to another thing. In situations where you don't want to use giant fenders (due to making the step on/off too large, for example), you'll need to use more fenders to avoid excessive contact pressure with the smaller ones. In a situation where 2 or 3 of the 20" balls is adequate, you might need 4 - 6 smaller fenders to handle the forces appropriately.

Only the aft half of our rub rail makes contact with the dock in our slip, but the lines keep us in place. Lines hanging from the top of a lock wall do not have the leverage of a dock line that is nearly parallel to the water, and line handlers to not have the same strength as our cleats.

Figuring the physics out would be simple if this was a pontoon boat with hull exposure roughly parallel to the lock wall bow to stern, but the curve and flare of the forward half of our Mariner 37 means that the forward fender is very close to the mid point of the boat. The last parallel spot on the hull is at the bottom of the steps to the flybridge where it is 20 feet ahead to the bow and 20 feet back to the transom.

Moving forward about 6 feet provides better leverage, but requires a far bigger fender to reach the hull. A 27 inch diameter Polyform A-5 ball looks like the right size. It is better to have the advantage of that 6 feet ahead of the mid point, yes (as opposed to equal size fenders at the mid point and aft at the stern)?

HeadedToTexas said:

Only the aft half of our rub rail makes contact with the dock in our slip, but the lines keep us in place. Lines hanging from the top of a lock wall do not have the leverage of a dock line that is nearly parallel to the water, and line handlers to not have the same strength as our cleats.

Figuring the physics out would be simple if this was a pontoon boat with hull exposure roughly parallel to the lock wall bow to stern, but the curve and flare of the forward half of our Mariner 37 means that the forward fender is very close to the mid point of the boat. The last parallel spot on the hull is at the bottom of the steps to the flybridge where it is 20 feet ahead to the bow and 20 feet back to the transom.

Moving forward about 6 feet provides better leverage, but requires a far bigger fender to reach the hull. A 27 inch diameter Polyform A-5 ball looks like the right size. It is better to have the advantage of that 6 feet ahead of the mid point, yes (as opposed to equal size fenders at the mid point and aft at the stern)?

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In locks our forward-most fender at rub rail height is far enough forward that it should never touch the wall, but if we ever get a bit twisted then it'll save from hitting the rub rail on the wall and keep us further way, giving more margin before hitting the pulpit. I've also occasionally pivoted onto it to kick the stern out before backing away from a wall. I don't try to keep us perfectly parallel or against the wall in locks, just close enough to stay in a good position (so we fender more conservatively than we would for typical docking).

HeadedToTexas said:

A 27 inch diameter Polyform A-5 ball looks like the right size. It is better to have the advantage of that 6 feet ahead of the mid point, yes (as opposed to equal size fenders at the mid point and aft at the stern)?

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Check the weight, before you take that plunge. My Admiral can't reliably shift one from one side to the other.

But yes, we'd use ours further forward where the hull has curved more...

-Chris

Good point. A 27 inch diameter Polyform A-5 ball weighs 20 pounds.

ranger58sb said:

...we'd use ours further forward where the hull has curved more...

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That's really my question. Does a boat with such a pronounced curve that starts at mid ship need a ball further forward, or like dock posts, are fenders at the stern and mid point enough?

HeadedToTexas said:

That's really my question. Does a boat with such a pronounced curve that starts at mid ship need a ball further forward, or like dock posts, are fenders at the stern and mid point enough?

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I like to have something further forward just in case, but realistically, unless it's a massive fender, it shouldn't ever touch due to the hull curve.

In my case, the big ball would be to keep the rub rail off the lock wall.

HeadedToTexas said:

That's really my question. Does a boat with such a pronounced curve that starts at mid ship need a ball further forward, or like dock posts, are fenders at the stern and mid point enough?

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Sorry, can't say about that, relative to your boat.

Although, we do like to have something forward of the curve, especially if we think we might lean against a dock on purpose (for leverage or whatever). So far our 20" buoy has been sufficient for that.

For warping, I'd actually prefer the 27" but... it's so heavy I'd have to come down off the bridge to get in place,
and the weight (plus warping) means it'd be better to hang from the bottom of a stanchion, not from our rub rail... another impediment to any sort of quick rigging.

-Chris

I use 2-12" and 1-17"

ranger58sb said:

Sorry, can't say about that, relative to your boat.

Although, we do like to have something forward of the curve, especially if we think we might lean against a dock on purpose (for leverage or whatever). So far our 20" buoy has been sufficient for that.

For warping, I'd actually prefer the 27" but... it's so heavy I'd have to come down off the bridge to get in place,
and the weight (plus warping) means it'd be better to hang from the bottom of a stanchion, not from our rub rail... another impediment to any sort of quick rigging.

-Chris

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for our larger locking ball when splicing the rope on I did a large enough loop at the ball end so we can just slip it over our forward cleat to keep it high and another loop at the other end to be able to hang closer to the water line.

HeadedToTexas said:

That's really my question. Does a boat with such a pronounced curve that starts at mid ship need a ball further forward, or like dock posts, are fenders at the stern and mid point enough?

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I used 3 polyform A-5 balls. One almost to the stern. One just forward of the pilothouse door (between that one and the stern ball, it held the boat about 18" off a flat wall). One just under the cap rail about halfway between the bow and the middle ball. The position was such that if the boat was against the lock wall, the middle ball and the bow ball would keep any part of the boat from touching. Additionally, the bow ball has a long line with a loop for the bitter end. The loop goes over the cleat so that the length is correct to just float the ball. Normally it's pulled up and tied just under the cap rail. Occasionally some of the locks have very short walls when the locks are full. This allows you to drop the bow ball to water level to protect the hull.

Ted

Hopefully some helpful images.

The stern and middle ball with a line around the pipe going up. You can clearly see the boat being held off by the two balls.



One version of the pipe in the wall.



A better pic of the middle ball.



The bow ball before I lengthened the line to drop it to the water. Just under the cap rail.



A cleat (for barges) in the wall. A small ball will go inside the cleat pocket (lock rash in the making) and may not be able to get out before the fender line parts.


Ted

Good points oc diver- my forward fenders, that are round, are placed just below the cap rail.
OP might be thinking they need to be down at dock/rubrail level. On my last boat I would also put a ball way forward to protect the bow pulpit. Currents in the locks tended to kick my stern out and due to the line angle, I couldn’t stop the movement.

I have yet to lock through anywhere, but I have studied the process and watched a bunch of videos detailing the various types of lock walls, lines, bollards, etc. My question is about the location of fenders along the length of the hull. Near the stern is obvious. Amidships is obvious. Forward of midship is my question as the curve and flare mean the fender ball would have to be quite large to have any impact.

Somewhere there must exist a balance between a huge ball and a location closer to midships that still effectively protects the boat. On my boat, that appears to be just a few feet forward of the center point. Unless, of course, the boat is angled toward the wall as in during approach or springing off.

HeadedToTexas said:

I have yet to lock through anywhere, but I have studied the process and watched a bunch of videos detailing the various types of lock walls, lines, bollards, etc. My question is about the location of fenders along the length of the hull. Near the stern is obvious. Amidships is obvious. Forward of midship is my question as the curve and flare mean the fender ball would have to be quite large to have any impact.

Somewhere there must exist a balance between a huge ball and a location closer to midships that still effectively protects the boat. On my boat, that appears to be just a few feet forward of the center point. Unless, of course, the boat is angled toward the wall as in during approach or springing off.

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Can you post a picture of the side of the boat from a couple of feet outward of the stern. Basically I'm trying to understand is the curve more pronounced at the waterline, and maybe flatter a foot above the water.

Certainly nothing wrong with 3 balls on the side and a forth ball protecting the bow cap rail. One consideration on ball placement is based on the cleat you plan to use for the pipe, cable, or floating bollard. Ideally you want the cleat at least 10' from the stern and from the middle ball (not the one protecting the cap rail). If the cleat is to close to the middle ball, it's tougher to keep the bow off the wall.

On many locks where you will be looping around a pipe or cable, there will also be hanging lines. As there will be 2 of you, one person can grab a hanging line off the stern and maintain modest tension to keep the stern against the wall. A long boat hook, gloves, and a length of line are required. The line is sometimes used to lengthen the hanging line so that your pulling on an angle from the side away from the lock wall. A simple square knot allows you to join lines of different sizes. Lengthening the line is almost always when going up (if the line is too short). There's usually turbulence when going up, almost never when going down.

Ted

Here are two additional views for context. Thanks Ted.

Seeing the pic, I might be inclined to consider two balls.

One forward of midships, approx. right under where that hawse hole is. And then another further forward, only intended to work if the bow swings far enough toward the dock/lock to begin to come into contact/

That way, two 20" buoys, for example, could work without adding the weight of a 27.

Maybe.

-Chris

HeadedToTexas said:

Here are two additional views for context. Thanks Ted.

View attachment 159277

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If it were me, and it was, I would use two Polyform A-5s for locking (plus the one to guard the bow cap rail). Then use something like an F-6 for docking. Locking fenders get pretty nasty and I try to limit how much hull they come in contact with. From your picture, two A-5s 6" to 12" above the water would work very well.

The bigger issue in my mind is where the cleat for locking is located. Mine wasn't ideally located (too close to the forward ball), but it worked most of the time.

In this picture you can see two cleats on either side of the dryer vent above the cap rail. I installed the one under the window, which proved to be unmanageable other than working through the window.


The forward fender would hang from the stanchion just forward of the pilothouse door. Not enough separation between the fender and the cleat.

Where is the cleat you plan to use?

Ted

The cleats aren't there yet, but here is where they will be when that project bubbles up to the top of my priority list. Proper backing plates and all. They are the subject of a separate thread here somewhere.

Too far aft for a fender, but as good as I can get for locking lines.