Ball sizes

[HeadedToTexas]

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?

 

[rslifkin]

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).

 

[Comodave]

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.

 

[Mac2]

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.

 

[Comodave]

Yup, no fender covers in locks.

 

[Jeff F]

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.

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

 

[rslifkin]

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

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.

 

[Comodave]

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

 

[ranger58sb]

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?

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

 

[HeadedToTexas]

Great stuff. Thanks guys.

 

[O C Diver]

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

 

[rslifkin]

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.

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.

 

[HeadedToTexas]

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)?

 

[rslifkin]

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)?

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).

 

[ranger58sb]

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)?

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