Why the Right Fender Makes All the Difference
A boat fender — also called a bumper — is the cushion between your hull and a dock, piling, or another vessel. Without adequate fender protection, docking in a current, a wake from a passing boat, or an overnight surge can leave you with scratched gelcoat, dented rails, or worse. The right fenders, properly sized and positioned, protect your investment every time you tie up.
This guide covers fender types, how to size fenders for your boat, how many you need, and how to rig them correctly.
Fender Types
1. Cylindrical (Round) Fenders
The most common fender style for recreational boats. Cylindrical fenders hang vertically from a cleat or rail and provide excellent protection against docks and pilings.
- Best for: Powerboats, sailboats, and most recreational vessels docking alongside a pier or floating dock
- Pros: Versatile, easy to rig, available in a wide range of sizes, can be hung vertically or horizontally
- Cons: Can roll out of position if not rigged correctly; not ideal for piling protection when hung vertically
2. Flat / Inflatable Boat Bumpers
Long, flat inflatable bumpers that run along the full length of the boat's side. Ideal for boats that dock in the same slip repeatedly or need full-length protection.
- Best for: Pontoon boats, houseboats, and any vessel that benefits from continuous side protection
- Pros: Maximum coverage, stays in position, excellent for tight slips
- Cons: Less portable than cylindrical fenders; requires inflation
3. Pontoon / Flat Fenders
Specifically designed for the flat sides and unique geometry of pontoon boats. Wider and flatter than standard cylindrical fenders to protect the pontoon tubes and deck edge.
- Best for: Pontoon boats exclusively
- Pros: Purpose-built fit, better coverage for pontoon geometry
- Cons: Not useful on other boat types
4. Piling Fenders
Wrap around dock pilings to protect the hull when the boat is pushed against a piling by current or wind. Often used in addition to standard fenders.
- Best for: Boats in tidal areas or exposed slips where the boat frequently contacts pilings
How to Size Fenders for Your Boat
Fender sizing is based on boat length and beam (width). The general rule: 1 inch of fender diameter for every 4–5 feet of boat length, with a minimum of 4 inches diameter for any boat.
| Boat Length | Recommended Fender Diameter | Recommended Fender Length |
|---|---|---|
| Up to 20 ft | 4–5" | 18–20" |
| 20–26 ft | 5–6" | 20–24" |
| 26–32 ft | 6–8" | 24–27" |
| 32–40 ft | 8–10" | 27–30" |
| 40–50 ft | 10–12" | 30–36" |
When in doubt, go larger. An oversized fender provides more protection and compresses more before the hull contacts the dock. Undersized fenders bottom out and provide little protection.
How Many Fenders Do You Need?
A minimum of three fenders per side is the standard recommendation for most recreational boats:
- One at the bow (forward quarter)
- One amidships (widest point of the boat)
- One at the stern (aft quarter)
For longer boats (over 30 ft), add a fourth fender. In rough conditions, exposed slips, or when leaving the boat unattended overnight, more is always better. Keep at least one extra fender aboard for emergencies.
How to Rig Fenders Correctly
Vertical Rigging (Most Common)
Hang fenders vertically from a cleat or lifeline stanchion so the bottom of the fender is just below the waterline. This protects the widest part of the hull at the waterline where contact with a dock is most likely.
Horizontal Rigging
Rig fenders horizontally (parallel to the water) when docking against a piling. A horizontally rigged fender wraps around the piling and prevents the hull from sliding past it.
Fender Lines
- Use fender line (not dock line) — smaller diameter, easier to adjust
- Tie with a cleat hitch or round turn and two half hitches for secure, adjustable attachment
- Adjust height so the fender sits at the dock's contact point — this varies by tide and dock height
Inflatable Boat Bumpers: Full-Length Protection
For boats that dock in the same slip regularly, inflatable boat bumpers offer continuous side protection without the gaps between individual fenders. Seipel Marine's inflatable bumpers are available in 5, 10, 15, and 20-foot lengths — mix and match to cover your boat's full length.
- Seipel Marine 5' Inflatable Bumper (Grey) →
- Seipel Marine 10' Inflatable Bumper (Grey) →
- Seipel Marine 15' Inflatable Bumper (Grey) →
- Seipel Marine 20' Inflatable Bumper (Grey) →
Also available in black:
- Seipel Marine 5' Inflatable Bumper (Black) →
- Seipel Marine 10' Inflatable Bumper (Black) →
- Seipel Marine 20' Inflatable Bumper (Black) →
Pontoon Boat Fenders
Standard cylindrical fenders don't fit pontoon geometry well. The Dock Edge 'TOON Pontoon Fender is purpose-built for pontoon boats, providing a secure fit along the pontoon tube and deck edge.
Fender Care & Maintenance
- Rinse after saltwater use to prevent UV degradation and salt buildup
- Check inflation regularly on inflatable fenders — they lose pressure over time
- Use fender cleaner/protector to restore shine and protect against UV and ozone cracking
- Inspect for cracks or punctures at the start of each season
- Store out of direct sunlight when not in use to extend life
Keep your fenders looking new with Star brite Inflatable Boat Fender Cleaner & Protector →
Fender Buying Checklist
- ✅ Fender diameter sized for your boat length (1" per 4–5 ft of LOA)
- ✅ Minimum 3 fenders per side
- ✅ One extra fender aboard for emergencies
- ✅ Fender lines for each fender
- ✅ Pontoon-specific fenders if applicable
- ✅ Fender cleaner/protector for maintenance
Shop Boat Fenders at Egret Marine
Browse our full selection of boat fenders, fender accessories, and fender covers at Egret Marine.
Not sure what size or style is right for your boat? Contact our team — we're happy to help.