Selden Hints and Advice on Rigging and Tuning (PDF)

OWNER'S MANUAL

Selden's rigging and tuning handbook: cap shroud and backstay tension targets for each rig type, the "folding rule method", mast heel location on keel-stepped masts and the annual rig check – plus the tuning sheets for fractional rigs without masthead backstay, double-diamond multihull rigs and the S.O. 36, 39 & 42.

DocumentSelden Hints and Advice on Rigging and Tuning Owner's Manual

FormatPDF · 92 pages · 11.2 MB

LanguageEnglish

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Contents Shroud Tension Tuning by Rig Type Keel-Stepped Masts Annual Check Tuning Sheets Products

Selden Hints and Advice on Rigging and Tuning — Owner's Manual

What the Handbook Covers

Following the rigging instructions for your rig type is a condition of the Selden guarantee. The mast ID number is engraved at the lower end of the mast section; the boom ID is at the forward lower end of the boom.

Chapter	Page
Rig types, longitudinal, lateral and running rigging	6–12
Preparing the yacht, checking the mast	15–16
At the crane	22
Keel-stepped masts	24
Alternative rigging of jib furling system	29
Tensioning the cap shrouds / "The folding rule method"	31–32
Tuning for safety	33
Masthead rigs	35
Fractional rigs	45
19/20 rig and similar	51
Bergström-Ridder rig	53
Booms, Rodkicker	56–59
Working aloft, unstepping the mast	60–63
Annual maintenance	64
Storage, mounting new fittings	69–70
Calculating mast and rig dimensions	72
Positive roach + in-mast furling, sail slides and sail entry (MDS)	75–76

1 x 19 Wire Breaking Loads

Wire Ø mm	kN	lbs
3	8	1,770
4	14	3,090
5	22	4,860
6	31	6,845
7	43	9,490
8	56	12,360
10	88	19,425
12	126	27,815
14	171	37,750
16	216	47,680

Aim for cap shrouds at 15-20% of the breaking load; final check under sail. 1 mm stretch per 2 m of 1 x 19 wire = 5% of breaking load, whatever the diameter.

"The Folding Rule Method"

Tools: 2 metre measuring rod (folding rule), adhesive tape, vernier callipers. Start with cap shrouds hand-tight.
Tape the rule to the starboard cap shroud, lower end approximately 5 mm above the wire terminal. Measure the gap exactly: point A.
Tension starboard to A + 1.5 mm, then tension port the equivalent amount.
Keep going alternately. At A + 3 mm the cap shrouds are at 15% of breaking load (3 × 5%).

Stretch per 2 meter at 5% of breaking load
1 x 19 wire	1 mm
Dyform	0.95 mm
Rod	0.7 mm

Count how many rigging screw turns give 1 mm (5%) and note it. Lock rigging screws with split pins; Selden does not recommend lashing two rigging screws together when the upper terminal is a stemball.

Dockside Tension Targets (% of breaking load)

Rig type	Cap shrouds	Backstay	Key points
Masthead, one set of spreaders, single aft lowers + baby stay, or forward + aft lowers	15%	15% (short periods max 30%)	Forestay about 40% at max backstay. Cap shrouds should not slacken until about 20° heel.
Masthead, multi-spreader, swept spreaders	20% (max 25%)	15% normal / 20% pre-tension	Forestay about 40% with 20% in backstay and cap shrouds.
Masthead, multi-spreader, in-line spreaders (cutter stay)	15%	15% (short periods max 30%)	Runners recommended if the cutter stay is more than 6% of fore-triangle height below the forestay fitting; runners max 30%.
Fractional, one set or multi-spreader, swept spreaders	20% (max 25%)	Hard, max 20%	Backstay must never slacken completely; stopper-knot in the tackle tail.
Fractional, in-line spreaders, forward + aft lowers	15%	15%	Runners 15% at the dock; windward runner 15-30% under sail.
19/20 rig and similar	As the fractional rig	Never eased completely	Single (aft) lowers: never let the masthead move forward.

Mast bend must not exceed 2% of fore-triangle height (1% with in-mast furling). Reef and check lateral straightness: more than 5 mm deviation → adjust the lower shrouds. Mark the setting on the rigging screws once the first-season tune is right.

Mast Heel Location for Rake and Pre-bend

A keel-stepped mast must have an even curvature (convex forward) right down to the heel. Formula: a = (x − y) • Q, with x from the rake table, y from the pre-bend table and Q the distance keel to deck. Example: rake 1.6°, pre-bend 0.4%, Q = 1900 mm → a = (0.027-0.014) x 1900 mm = 24.7 mm, heel 25 mm forward of the vertical line from the mast centre at deck ring level.

Rake [°]	x	Pre-bend [% of FH]	y
0.0	0.000	0.0	0.000
0.2	0.003	0.1	0.003
0.4	0.007	0.2	0.007
0.6	0.010	0.3	0.010
0.8	0.014	0.4	0.014
1.0	0.017	0.5	0.017
1.2	0.020	0.6	0.020
1.4	0.024	0.7	0.024
1.6	0.027	0.8	0.027
1.8	0.031	0.9	0.031
2.0	0.034	1.0	0.034
2.2	0.037	1.1	0.037
2.4	0.041	1.2	0.041
2.6	0.044	1.3	0.044
2.8	0.048	1.4	0.048
3.0	0.051	1.5	0.051

Small leaks past the internal seal can occur; the sealing kit 312-322-10 is poured into the mast while it is rigged. Tie-rods are left completely loose while tuning, then tightened just enough to stop them rattling.

Standing & Running Rigging

Check stays and shrouds for fraying; if a strand has failed, replace the complete pair.
Selden advises replacing all wire standing rigging after 20000Nm, its expected life.
Clean rigging screw threads with solvent and lubricate with Selden rigging screw oil (Art. No. 312-502) every year.
Check terminals, toggles, links, clevis and split pins for wear, distortion or cracks; check shackles close properly.
Replace halyards with messenger lines over winter; keep wire halyard parts away from the aluminium.

Mast & Boom

Rinse with water, wash with mild detergent, rinse carefully – especially at the mast foot.
Check structural fittings, holes and cut-outs for cracks, deformation, wear/play, fastening, corrosion and ageing plastic. Keel-stepped masts: check for cracks and dents at deck level.
Grease the boom outboard end-fitting screws every season, one screw at a time.
Coat all aluminium sections with paraffin oil, yacht polish or wax.
Painted spars: touch up damage with a paint suitable for aluminium; bed new fittings in "Mastic Frame Sealant".

Extra Tuning Instructions (downloads)

Fractional rig without masthead backstay, aft swept spreaders (595-748-E)

Cap shrouds to about 15% of breaking load, then tension the lower shrouds for the desired mast curve.
At the optimum heel (20°- 25°) the mast must be straight athwartships and the lee cap shroud must not go slack; if it does, increase cap shroud tension (max. 25%).
Caution: with the main reefed so the headboard is 0.5 - 1 m below the forestay attachment, the mast can take a dangerous negative bend.

Multihull rig, 2 pairs of diamonds with lower shrouds (597-595-E)

Clamp the lower spreader ends at the same height on both sides (±5mm).
On trestles, tension RD1 to 1,2 times the final pre-bend: 0,9% of the P-measure (0,75% x1,2); outer diamonds then at 5 to 10% of breaking strength. RD2 to 10%.
Selden recommends a pre-bend of 0,75% of the P-measure. Cap shrouds 10%, lower shrouds 5 to 10%.

S.O. 36, 39 & 42 (595-494-E)

Spreaders elevate 6°. V1 cap shrouds to 20% (gap A + 4 mm on the folding rule). Recommended pre-bend 0,5% of P (conventional) / 0,2% (furling); D2 tensioning reduces curvature by approximately 10mm.