Choosing Polyform fender sizes

Polyform fender sizing starts with boat length, but length alone is a poor predictor. A 34-foot boat with high topsides and a pronounced flare needs different fendering from a flush-decked 34-footer lying against a finger berth. Polyform's own guidance is to plan for the worst conditions you expect, and to mix shapes. Cylindrical F and G fenders sit flat against parallel topsides. Spherical A-series fenders hold the hull off at a single point, which is what you want against a flared bow, a lock wall, a piled mooring or another boat rafted alongside.

F-series, A-series and G-series

The Polyform fender F-series covers fourteen sizes, from the 370mm F01S to the 1880mm F13, which absorbs up to 3.8 tonne-metres and is specified for vessels to 1500 tonnes deadweight. The Polyform fender A-series runs from the A0 at 210mm diameter to the A7 at 1100mm and 670kg buoyancy. A-series buoyancy is published as a pair: total, then the 60% figure Polyform states should not be exceeded in service. The Polyform Norway G-series is a lighter blow-moulded utility fender in four sizes.

Inflation pressure

Polyform fenders are designed for 0.15–0.20 bar at 20°C, roughly 2.2–2.9psi, and should be reduced to 0.05–0.06 bar in high temperatures or strong sun, particularly on dark products. Air expands as it warms, so a fender taken to full pressure on a cold morning is over-pressure by afternoon; over-inflation weakens the material and voids the warranty. Without a gauge, inflate until the wall still presses in about 1cm under light hand pressure, or 1.5cm in the tropics.

V10 and V40 valves

The V10 is a non-return valve with a securing screw: remove the screw, inflate, replace it. The V40 fitted to the largest products is not a non-return valve. Open it three or four turns anti-clockwise without removing it, inflate through the centre hole of the screw, then tighten. Both are all-plastic and friction-welded into the body, so there is nothing to corrode; both are stocked separately.

Using an A-series buoy for mooring

Used as a mooring buoy, an A-series buoy should be moored only from the lower swivel below the waterline; the upper grip ring is not a mooring point. Keep the total load below 60% of buoyancy, allowing for marine growth, current and wave action, and do not connect stainless, aluminium, copper or brass to the hot-dip galvanised rod or swivel.

Cleaning and marking

Soap and water is the recommended way to clean Polyform fenders, followed by a thorough rinse; no polish is needed. Lacquer thinner and acetone break down the vinyl irreversibly. The surface is heavily siliconised, so use alcohol-based permanent markers to number fenders.

Polyform Norway Round Fender

Polyform Norway and Polyform US

Polyform AS in Norway and Polyform US in Washington are separate companies with overlapping model codes. An F3 from one is not an F3 from the other, and Polyform US designations such as HTM do not exist in the Norwegian catalogue. The dimensions on this page are Polyform AS figures.

About Polyform AS

Polyform AS was established at Aalesund in 1955 and brought the A-buoy to market in 1956, making it one of the longest-established manufacturers of inflatable plastic buoys. Inflatable products are soft vinyl formed by the company's patented POLYMATIQ® fusion process, with injection-moulded rib-reinforced rope holds; the G-series is blow moulded.

Polyform fender size selection table

Place this directly under the "Choosing Polyform fender sizes" H2. It is the page's primary ranking asset and targets "polyform fender size chart", "boat fender size guide" and the whole "what size fenders for a n-foot boat" family.

Reproduced from Polyform AS's published fender guide. Add the standing caveat: this is guidance only — hull form, freeboard, displacement and berth conditions govern the final choice.

Carry a second line under the table answering the "how many" question directly, since it appears in both autocomplete and PAA: a working minimum is one fender per 3 metres of hull length with a minimum of three, plus at least one spare of a different shape for rafting and lock work.

Specification tables

These should sit in the body of the page, not only on the individual product pages. They are what "polyform fender sizes", "polyform buoy sizes" and every model-number query are looking for.

F-series cylindrical fenders

A-series buoys and fenders

Buoyancy is shown as total, then the 60% figure Polyform gives as the maximum load in service.

G-series utility fenders

All figures are Polyform AS published data. Verify against current datasheets before publishing, and re-verify at each catalogue update.

Polyform Norway FAQ block

What size Polyform fenders do I need for my boat? 

Polyform publishes a boat-length guide: up to 10ft takes an A0, F01 or G2; 17–23ft takes A1–A3, F1–F2 or G3–G5; 24–30ft takes A3–A4, F2–F4 or G5; 31–45ft takes A4–A5 or F5–F7; 46–60ft takes A5–A6 or F7–F8; above 61ft, A7 or F11–F13. Treat it as a starting point. A heavy displacement boat with high topsides needs a size up on a guide built around length alone, and a boat that regularly rafts or locks needs at least one spherical fender regardless of what the table says.

How many fenders does a boat need? 

A common working rule is one fender per 3 metres of hull length, with three as an absolute minimum, so a 10-metre boat carries three to four a side in a normal berth. That covers the ordinary case. It does not cover rafting up, locking, coming alongside a wall with a tidal range, or a berth that turns out to be exposed when the wind backs. Carry more than the minimum, and carry at least one of a different shape.

What pressure should Polyform fenders be inflated to? 

0.15 to 0.20 bar at 20°C, which is about 2.2 to 2.9psi. In high temperatures, in strong sun, or on dark-coloured fenders, reduce that to 0.05–0.06 bar. Fenders hold far less pressure than most people expect, and the common fault is over-inflation, which stiffens the fender, reduces its ability to absorb energy, stresses the material and voids the warranty.

How do I inflate a Polyform fender without a pressure gauge? 

Inflate until the wall can still be pressed inwards about 1cm with light hand pressure — roughly 1.5cm in tropical conditions. Then check the inflated diameter against the published figure for that model; a fender noticeably larger than its stated diameter is over-inflated. A hand pump works, but an air compressor with a blowgun, or a tyre nozzle with the Polyform inflation adapter, is faster and easier to control.

Do boat fenders need to be re-inflated? 

Periodically, yes. The valves are non-return and friction-welded rather than glued, so losses are slow, but air volume changes with temperature and fenders lose a little over a season. Check pressure at the start of the season and again in high summer — the more important check is the second one, because a fender inflated correctly in April can be over-pressure on a hot August afternoon against a dark hull.

What is the difference between the V10 and V40 valve? 

The V10 is a non-return valve fitted to the majority of the range. It has a protective screw that must be removed to inflate and replaced afterwards to fully secure the air. The V40, fitted to the largest products, is not a non-return valve: open it three or four turns anti-clockwise without removing the screw, inflate through the centre hole in the screw itself, then tighten it. Both valves and the V10 valve screw are available as spares.

Can a Polyform valve be replaced? 

Yes. The V10 valve, the V10 valve screw and the V40 valve are supplied separately, which is the usual repair for a fender that will not hold air. Before replacing anything, check the screw is fully seated — a loose or missing valve screw is the most common cause of slow deflation and costs nothing to fix.

What is the difference between the F-series, A-series and G-series? 

The F-series is the heavy duty cylindrical fender, in fourteen sizes from dinghy to commercial vessel, with the thickest wall section and the highest energy absorption. The A-series is spherical, originally a buoy, and doubles as a fender where you want single-point standoff — flared bows, lock walls, rafting. The G-series is a lighter, blow-moulded cylindrical fender for smaller craft, where the cost and weight of an F-series is not justified.

Cylindrical or spherical fenders — which should I use? 

Cylindrical for parallel topsides and pontoon berths, where you want the fender to lie flat and spread the load along the hull. Spherical where the hull is curved or flared, against a wall or piles, and when rafting, because a ball keeps a fixed standoff and rolls rather than squeezing out from between two hulls. Most boats are better served by a mix than by a matched set of one shape.

What is a Polyform A4 buoy's buoyancy? 

The A4 has 90kg total buoyancy, with 54kg given as the working figure — Polyform's guidance is not to exceed 60% of total buoyancy in service. The margin is not conservatism for its own sake: it allows for marine growth, for the vertical component of load in current and wave, and for the buoy being pulled under by a snatching mooring line.

How do I use an A-series buoy as a mooring buoy? 

Moor only from the lower swivel, below the waterline. The upper grip ring is for handling and picking up, not for mooring loads. Size the buoy so the total load stays under 60% of its buoyancy, allowing for growth and sea state, and size the iron bar and swivel to the boat and the conditions rather than to the buoy. Inspect the whole mooring at least twice a year.

Why should stainless steel not be connected to a galvanised mooring rod? 

Galvanic corrosion. Stainless steel, aluminium, copper and brass are all more noble than hot-dip galvanised steel in seawater, so coupling them accelerates loss of the zinc coating and then the steel underneath — at the connection, below the waterline, where you cannot see it. Keep the rod, swivel and shackles in the same material family, and inspect the mooring twice a year.

How do you clean boat fenders? 

Soap and water first, and rinse thoroughly. Fender cleaners, vinyl cleaners, boat shampoos and mineral spirits can be used with care, and no polish is required or useful. Do not use lacquer thinner or acetone: they break down the vinyl irreversibly, and the damage is not cosmetic. For black rubber streaks, work on them early — they are far harder to remove after a season of UV.

Are boat fender covers worth it? 

They reduce abrasion on the topsides and stop black streaking from the fender itself, which is the main argument for them. Against that, a wet cover held against the gelcoat retains moisture and grit, so a cover that is never dried or rinsed can cause more marking than the bare fender it replaced. They also add windage and bulk in storage. Useful on a boat berthed permanently alongside; less obviously worthwhile on a boat that spends most of its time on a mooring.

What are Polyform fenders made of? 

The inflatable A, F, G, HL and CC ranges are soft vinyl, formed by Polyform's patented POLYMATIQ® fusion process, which gives a seamless body with uniform wall thickness and no glued joints. The rope holds are injection-moulded and rib-reinforced. The G-series is blow moulded. Polyform's separate hard-shell ranges are polyethylene with foam fill, and its marina and purse seine floats are BACELL closed-cell foam — different products, different materials.

What temperature range are Polyform fenders rated for? 

Polyform tests the F-series for strength and flexibility between -30°C and +50°C, using a cold-flex, UV-resistant compound. In practice the temperature question that matters to most owners is the upper end, because internal pressure rises with air temperature and dark fenders in direct sun run hotter than the ambient reading suggests.

Is Polyform Norway the same company as Polyform US? 

No. Polyform AS is Norwegian, based at Aalesund and manufacturing since 1955. Polyform US is a separate company based in Kent, Washington. The two use overlapping model designations — both catalogue an "F3" and an "A4" — and the dimensions are not the same. Polyform US also sells series that do not exist in the Norwegian range, HTM among them. Check which manufacturer a size chart refers to before ordering against it.

Can Polyform fenders be repaired? 

A valve fault is straightforward: the V10 valve, its screw and the V40 valve are all available separately. A puncture or split in the body is not economically repairable in most cases, and a patched fender should not be relied on for a berth you cannot watch. Cracking or splitting in a fender that has not been physically damaged usually points to sustained over-inflation.