Choosing the correct rigid boom vang requires more than yacht length. Seldén's Rodkicker range includes RK05, RK10, RK20 and RK30 units, with different lengths, load ratings, gas spring strengths and mounting arrangements. This guide brings the principal technical differences together and explains what to check when selecting a replacement.
The information below is based on Seldén's published Rodkicker specification and spare gas spring listings. It is a selection guide, not an approval for a particular yacht. Contact our rigging team if you need help identifying an installed unit.
What does a Rodkicker do?
A rigid boom kicker (boom vang) provides compression support beneath the boom while allowing the kicking tackle to control boom position and mainsail shape. Where a correctly specified gas spring is fitted, it can help raise or support the boom as the tackle is eased. A Rodkicker supplied without a gas spring does not provide that spring-assisted lift.
Selection depends on the yacht's rigging moment, rig type, boom weight and geometry, the mast and boom attachments, the available installed length and the required stroke.
Seldén Rodkicker dimensions and load ratings
Seldén identifies several lengths and load classes within the range. The figures are catalogue values for the listed unit families, not instructions for setting attachment positions. All dimensions are in millimetres and safe working loads in kilograms.
| Model | Catalogue lengths | Stroke | Safe working load |
|---|---|---|---|
| RK05 | 1,150 | 180 | 800 kg |
| RK10 | 1,360 (short) / 1,670 (long) | 300 | 1,200 kg |
| RK20 standard | 1,720 (short) / 2,260 (long) | 300 | 1,800 kg |
| RK20 heavy duty | 1,720 (short) / 2,260 (long) | 300 | 2,400 kg |
| RK30 standard | 2,200 (short) / 2,700 (long) | 300 | 3,800 kg |
| RK30 heavy duty | 2,200 (short) | 300 | 4,400 kg |
Some additional RK20 length and catalogue variants exist. Check the exact part number against the Seldén listing before assuming that a replacement with the same model name will fit.
Rigging moment: an important selection check
Seldén also publishes rigging-moment figures for fractional and masthead rigs. These are useful for identifying the load class of a candidate Rodkicker, but they do not replace the manufacturer's full sizing procedure.
| Model / class | RM fr (kNm) | RM MH (kNm) |
|---|---|---|
| RK05 | 14 | 20 |
| RK10 | 25 | 35 |
| RK20 standard | 45 | 62 |
| RK20 heavy duty | 68 | 94 |
| RK30 standard | 131 | 181 |
| RK30 heavy duty | 162 | 223 |
RM fr and RM MH follow Seldén's fractional-rig and masthead-rig terminology. Confirm the appropriate rating with the mast specification and rigging geometry; do not select on displacement or hull length alone.
Gas spring strengths and replacement references
Rodkickers within the same size family can be supplied without spring assistance or with different spring forces. A stronger spring is not automatically a better replacement: it needs to suit the boom weight, fittings and original specification.
| Seldén gas spring reference | Nominal force | Listed Rodkicker use |
|---|---|---|
| 308-038 | 700 N | RK05 |
| 308-070 | 600 N | RK10 |
| 308-071 | 1,200 N | RK10 / RK20 |
| 308-072 | 2,500 N | RK10 / RK20 / RK30 |
| 308-073 | 5,000 N | RK20 / RK30 |
These are reference numbers from Seldén's gas spring catalogue; compatibility depends on more than nominal force. Check dimensions, original end fittings and the exact Rodkicker variant. Seldén notes that replacement springs are supplied without the Rodkicker end fittings and specifies cylinder-up installation for long service life.
Safety: Gas springs are highly loaded components. Support the boom, unload the kicker and follow the manufacturer's service instructions before dismantling; do not attempt to puncture or dismantle a gas spring.
How to identify your existing Rodkicker
- Find the model or part reference on the unit, where still legible.
- Measure the unit length and available movement, and photograph the complete installation.
- Record the mast and boom attachment geometry, bracket type and pin dimensions.
- Confirm whether a gas spring is fitted and, if known, its original rating.
- Check the mast section, boom section, rig type and boom weight before selecting a replacement.
For a more detailed maintenance procedure, see our guide to identifying and replacing a Seldén Rodkicker gas strut.
Mast brackets, boom brackets and alternative kicker systems
The fittings at both ends of the Rodkicker are as important as the body length. Different Seldén mast and boom sections can require different brackets, pins or attachment arrangements. For keelboats with an alternative boom-control layout, Seldén also lists GNAV equipment; hydraulic boom vang products are a separate category and should not be treated as interchangeable with a spring-assisted Rodkicker.
When replacing the original assembly, confirm the bracket geometry and available clearance throughout the boom's operating range. Avoid ordering by model number alone where the original mast or boom has been changed.
Which Rodkicker should I choose?
RK05 covers the smallest model in this group; RK10 introduces short and long bodies; RK20 adds higher safe working loads and a heavy-duty option; RK30 is the larger class with standard and heavy-duty ratings. That progression is not a direct yacht-length chart. Final selection must account for masthead or fractional rig, the rigging moment and the existing installation.
For bespoke yachts, older masts and replacement brackets, send us photographs and measurements. We can help establish the correct replacement assembly, gas spring or fittings.
Frequently asked questions
Can I replace an RK10 with an RK20?
Not solely on the basis of increased load rating. The units have different dimensions and may require different attachment geometry or brackets.
Does every Seldén Rodkicker contain a gas spring?
No. Seldén's catalogue includes both unsprung and spring-assisted versions. Check the installed unit before ordering a replacement spring.
Can I select a gas spring using the force rating alone?
No. The body dimensions, spring ends, compatibility with the Rodkicker and the boom's weight and geometry must also be checked.
Need help choosing a Seldén Rodkicker?
Check the fitted mast and boom brackets, unit length and spring force before purchase.
Primary technical references: Seldén Rodkicker product specification, Seldén replacement gas springs and Seldén Rodkicker brackets. Manufacturer listings contain detailed part numbers and variants; verify current information before purchase.