Harken MKIV User manual

Please read these instructions carefully before installing, servicing, or operating the equipment.
This manual may be modified without notice. See: www.harken.com/manuals for updated versions.
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MKIV UNDERDECK JIB REEFING & FURLING
Unit 0
Installation Manual – Intended for specialized personnel or expert users
4427 01/14
Preassembly
Parts 4
Rigging Parts Check/Tools 5
Dimensions/Sailmaker's Instructions 6
Rigging Options/Turnbuckle 7–8
Stay Into Foil Options 8
Hub Assembly
Install Hub Assembly in Bow 9
Under-Deck Lead Block 10
Preassembly
Top Foil Length 11
Short Top Foil 12
Foil Length Check 13
Assembly
Foils/Connectors 14–20
Halyard Swivel 20
Torque Tube Assembly 21
Rod Rigging 22
Attach Turnbuckle/Foils to Boat 23–24
Feeder/Final 25
Commissioning
Turnbuckle 26–27
Lead Line to Cockpit 28
Halyard Swivel Height/Angle 29
Halyard Restrainer/Tension 30
Operation
Halyard/Headstay Tension 31
Raise Sails/Storm Sails/Reefing 32–33
Secure Sail 33
Race Conversion 33
Maintenance/Troubleshooting
Clean/inspect 34
Replace Line 34
Storage/Transporting/Remove 34
Troubleshooting 35
Parts List 36–37
Drilling Template 38

2 MKIV Underdeck Unit 0 07/14/10
Parts Descriptions
Safety Precautions/Parts Description
a
c
b
d
f
e
g
1
Hub Assembly
a) Bridge Fairlead Assembly
b) Ball Spool Guard Assembly
c) Keeper
d) Deck Plate
e) Tack Shackle
f) Torque Tube
g) Torque Tube Screws
h) Foil Clamp
Part No. Size Wire Size Rod Size
Standard
Headstay Length
Max.
Headstay Length
7410.11 Unit 0
3
/ 16 ",
7
/ 32 "
5 mm, 6 mm
-4, -6
4.37 mm, 5.03 mm
38'4"
11.7 m
45' 4"
13.8 m
Size Check
1. Check headstay in chart below.
h
2
WARNING! Strictly follow all instructions to avoid potential
hazards that may kill or hurt you and others. See www.harken.com/
manuals for general warnings and instructions.
WARNING! This symbol alerts you to potential hazards that may kill or hurt you and others
if you don't follow instructions. The message will tell you how to reduce the
chance of injury.
Introduction
This manual gives technical information on installation and service. This information is destined exclusively for
specialized personnel or expert users. Installation, disassembling, and reassembling by personnel who are not
experts may cause serious damage to property or injury to users and those in the vicinity of the product. If you
do not understand an instruction contact Harken.
The user must have appropriate training in order to use this product.
Harken accepts no responsibility for damage or harm caused by not observing the safety requirements and
instructions in this manual. See limited warranty, general warnings, and instructions in www.harken.com/manuals.
Purpose
Harken®Jib Reefing and Furling is designed for rolling sails on sailboats to reduce sail size or to completely roll
so wind has little effect on the sail. Use of this product for other than normal sailboat applications is not covered
by the limited warranty.
Safety Precautions
CAUTION! This symbol alerts you to potential hazards that may hurt you and others if
you do not follow instructions. The message will tell you how to reduce the
chance of injury.

07/14/10 MKIV Underdeck Unit 0 3
Preassembly Sizing Check
4
3
8
6
9
Upper Unit
1) Bottom Foil
2) Feeder
3) Connector Bushing
4) Bottom Connector
5) 7' (2.13 m) Foil
6) Connector Wedge
7) Connector Screws
8) Connector
9) Halyard Swivel
10) Trim Cap Screws
11) Trim Cap
Unit Part No. A B C D
07410.11 5
1
/ 2 "
140 mm
3
25
/ 32 "
96 mm
5
7
/ 16 "
138 mm
6
29
/ 32 "
175 mm
Will Drum Fit in Bow?
Note: See dimensions above. Unit requires a connection to underdeck chainplate for stay loads.
See page 38 for deck plate dimensions.
Furler Requires Drained Compartment
Harken’s Underdeck Furler is designed to keep much of the water from entering the bow compartment. Water
will drip through the furler when it rains or when sailing in heavy weather. The furling compartment must drain.
3
10
11
A
B
C
D
7
5Online Product Registration
www.harken.com/FurlingWarranty

4 MKIV Underdeck Unit 0
Hub Assembly
Preassembly Parts
Bow Shackles
Trim Cap
Plastic Connector
Wedges
Feeder
Prefeeder
Halyard Swivel
5200
Adhesive
Injector
2' (610 mm)
Bottom Foil
7' (2.13 m)
Foils
Bottom
Connector
Connectors
Connector Bushings
Part No. Quantity Description
HFG951 1 Hub assembly with foil clamp
H-39923 1 Halyard swivel
Main Components
Part No. Quantity Description
7410.30 5 7'(2.13 m) foil
7410.33 1 2'(610 mm) Botton foil
Foils (Standard Package)
Quantity Description
1 Each 2.5, 3, 5 mm Hex keys
Tools
Part No. Quantity Description
7410.31 4 6.5" (165 mm) Connector
7410.32 1 10" (254 mm) Bottom Connector
HFG294 1 Connector bushing set (10-H-42067/10-H-42068)
HFG298 1 Plastic connector wedge set (12-H-39625)
HFG341 1 Foil screw set (26-HFS1105)
HFG679 1 Trim cap set (H-37335/H-37336)
HFG629 1 Trim cap screw set (3-HFS1126)
947 1 Prefeeder
H-39713 1 Feeder with screw and tab
2110 3 6 mm Bow shackles
HFG725 1 Injector, 1 oz. 5200 Adhesive (HFG722)
HFG739 2 Red Loctite®(for foil screws)
Other Components
2.5, 3, 5 mm
Hex Keys
Trim Cap Screws
Forward Ø Min Break Strength Aft Ø
3
/ 16 " (5 mm) 1300 lb (590 kg)
1
/ 4 " (6 mm)
Line Specifications
Line (Not included with Furler)
Note: Line is not included with furler. Drum of
unit is smaller to allow it to fit into narrow bow
sections. If overlapping sails are used, standard
diameter line will fill up drum and jam furler. To
prevent this, use small diameter, high strength
line at forward end and have a rigger add a
cover at aft end where line is handled.
Foil Screws
Red Loctite®

09/17/10 MKIV Underdeck Unit 0 5
1. Turnbuckle components are not included and
must be purchased separately.
2. Rod rigging requires Harken rod adapter stud.
3. Order Harken Lead Blocks and one additional
7403 if necessary. Fits 1" (25 mm) stanchions.
4. Furling Line - Use 3/16 to 1/4" (5 to 6 mm). To figure
line length, measure the distance from the furler to
the furling cleat. Add 15' (4.5 m).
Preassembly Rigging Parts Check/Tools
Tools You Will Need
MKIV Furlers are shipped with 3M 5200
adhesive. Use adhesives on dry connectors
and foils using the special injection system
described in the assembly section. Parts
may immediately be exposed to rain. Cure
is best at 70F (22C) with 50% humidity.
Do not apply at temperatures below 40F
(5C) and above 100F (38C).
Although adhesive has not cured it will
remain in place on foil joints whether
they are left on the ground or raised up
on boat. Foils can be raised immediately
after assembly and sails fitted.
Note: A small amount of adhesive may
bulge out of injection ports. If possible
let system sit for a couple days before
sailing. If adhesive gets on sails remove
using acetone. For faster-curing adhesive,
purchase 4200 Fast Cure.
Note: Damaged foils can be repaired.
Use a hand-held propane torch to heat
joints until foils can be pulled apart.
Adhesive Alert
1. Long tape measure 6. Side cutters 11. Center punch 16. Hole saw 4
1
/ 4 " (110 mm)*
2. Short tape measure 7. Rat-tail file 12. Rigging or black tape 17. Deck sealant
3. Power drill 8. Hex keys (provided) 13. Scissors 18. Box end wrench
4. Drill bits
1
/ 8 " (3 mm) 9. Slotted/Phillips screwdrivers 14. Metal straight edge 19. 6 mm bolts, nuts, and washers
5. Hacksaw 10. Needle-nose pliers 15. Hammer
10 13
12
11
8
7
6
5
3
2
1
14
9
7404 Lead Block Kit
(Sold Separately)
349
131
Unit Turning Thru-Deck
0349 131
Recommended Furling
Compartment Lead Blocks
16
Use 6 mm bolts and washers to
mount deck flange. To figure bolt
length, add
3
/ 8 " (10 mm) to deck
thickness. Minimum thread
engagement must be 9 mm.
19
17
4
Unit Drill Ø
0
1
/ 8 " (3 mm)
15
7420 -4
7421 -6
Rod Adapter Stud
ROD RIGGING
Harken Rod Adapter
Stud Required
(Sold Separately)
*Requires some beveling of bottom edge of deck hole to provide a good fit. Alternatively a smaller hole may be used to fashion a socket in deck to conform
to ball shape. This may improve appearance and reduce amount of water that enters. A 4
1
/ 2 " (115 mm) hole saw may also be used if no beveling is desired.
18

6 MKIV Underdeck Unit 0
Preassembly Dimensions/Sailmaker's Instructions
Luff Length
Note offsets above and below sail.
A shorter luff may be required if a halyard restrainer is necessary
(page 30).
If luff of sail is not long enough to put halyard swivel near top of
headstay foil, a pendant must be added. See page 29.
Tack Setback
Note setback for tack shackle and cut the sail accordingly.
Luff Tape Size
All units require #6 (6/32" or 5 mm) luff tape.
Luff Tape Length
Cut off top of luff tape so it is 18–24" (450–600 mm) below head
of sail. This allows head to lag behind rest of sail to help flatten
sail. It will also help head to roll more smoothly.
Note feeder height and extend bottom of luff tape downward so
it is below feeder. This will prevent luff tape from catching in
feeder as sail is lowered.
Tack and Head Shackles
Make sure tack and head shackles fit sail
rings. The minimum inside dimensions
of standard head and tack shackles are:
A
B
Unit Part No. A B C D E F
07410.11 3
3
/ 4 "
96 mm
6
1
/ 4 "
158 mm
1
19
/ 64 "
33 mm
15
/ 64 "
6 mm
34
5
/ 16 "
817 mm
3
19
/ 32 "
91.5 mm
F
D
C
E
AB
Unit A B
011/16" (27 mm) 1/2" (13 mm)
Suncover
7410.11 Furls in one direction only.
IMPORTANT! Suncover must be installed on starboard side of sail.

07/14/10 MKIV Underdeck Unit 0 7
Preassembly Rigging Options — Turnbuckle
The stay runs up the center of the MKIV Unit
0 Underdeck furler. It does not attach to the
furler in any way. Choose one of the follow-
ing three turnbuckle locations based upon
diameter of turnbuckle body and access to
the turnbuckle below deck. The interior of
the furler components are shown below.
Turnbuckle Options
Turnbuckle Below Furler
Make sure that the upper stud wrench
flats are accessible. If necessary, the bridge
fairlead assembly can be lowered below the
turnbuckle to allow access to wrench flats.
B
A
C
E
D
H
G
F
Unit A B C D E F G H
01
7
/ 16 "
36.4 mm
10
1
/ 8 "
258 mm
1"
25.4 mm
7
1
/ 2 "
190.5 mm
5
1
/ 2 "
140.5 mm
1
7
/ 8 "
47.6 mm
2
5
/ 16 "
58.6 mm
1
1
/ 2 "
38.1 mm

8 MKIV Underdeck Unit 0
1. Swage stud at end of wire.
2. Open end of wire and install Norseman or Sta-Lok®stud after
foil is assembled.
3. Rod adapter nosepiece for Harken rod adapter stud: Threaded
nosepiece must have a positive lock as well as adhesive.
Use Harken stud with cotter pins. See page 22.
Options for Snaking Stay into Foils
Turnbuckle inside torque tube
Set up a pendant below making sure
to have a turnbuckle toggle.
Use a swage to swage turnbuckle
located just above the lower unit.
Check turnbuckle fit inside torque
tube. Requires a “third hand” to adjust.
Turnbuckle above swage
On smaller size wires 3/16" (4 mm)
a small turnbuckle should fit. Check
dimensions above for clearance.
Preassembly Turnbuckle Options
WARNING! Using a threaded nosepiece with only
adhesive at the upper rod eye terminal may result
in headstay system failure. Make sure there is a
mechanical lock.

MKIV Underdeck Unit 0 9
Assembly Deck Plate
Carefully locate center point in deck to locate deck plate. Line from mast to underdeck
chainplate must intersect this center point. Mark center fore/aft and athwartships line.
Use template to mark four outer holes and center pilot hole. Make sure closer pair of
holes is forward. Mark center hole for drilling large hole.
71° – 73°
Use 6 mm screws, washers, locknuts and deck sealant to fasten lower unit to deck.
Note: There must be a minimum of
3
/ 8 " (9 mm) thread engagement into deck flange.
Note: Deck plate angle
matches a stay angle of
72° when compared to
deck. Angles can vary
between 71° and 73°. If
deck does not fall within
these angles, shims must
be made using structural
adhesive to avoid exces-
sive pressure on deck
and deck bearings.
Once you are certain hole is located in line with
chainplate and any required shimming is done,
drill hole 90° to deck.
Make sure hole is just large enough so deck
plate bears against deck. It is better to make
hole slightly smaller and file opening larger
to fit. Use template to mark large hole and
bolt holes. Use hole saw to drill deck.
Tip: After pilot drill bit clears deck, drill final
hole from bottom using pilot hole to line up
hole drilled from top. This will prevent glass
from chipping.
Tip: Run line through fairlead
and dead end line into spool
before mounting lower unit.

Assembly Under-Deck Lead Block
Mount lead block so furling line is 90° to
hub assembly.
Mount thru-deck block. Be sure to angle
it toward stanchion lead block.
10 MKIV Underdeck Unit 0
90°

MKIV Underdeck Unit 0 11
UNIT 0
Length Chart
Dimensions Inches mm
ACenter of Pin to Bottom of Terminal
BBottom of Terminal to Top of Foil
.40* 10*
CTop Foil Length
DNumber of Foils ________ x 84" (2133.6 mm)
EBottom Foil 24 610
FBottom of Foil to underside of deck 14 359
Pin-to-Pin Length
*Add 1" (25 mm) if using a Halyard Deflector.
Make sure upper
measurement points
of A and pin-to-pin
are the same.
1Pin-to-Pin Length
2Subtract ABEF –
3Result (Pin-to-Pin – ABEF)
4Subtract D –
To find “D” pick number from chart below that is clos-
est to, but not greater than total from step 3.
Inches mm
3 X 84 = 252
4 X 84 = 336
5 x 84 = 420
6 x 84 = 504
3 x 2133.6 = 6400.8
4 x 2133.6 = 8534.4
5 x 2133.6 = 10668
6 x 2133.6 = 12801.6
Example–If result from Step 3 is:
500 inches “D” = 420 inches
12,000 mm “D” = 10,668 mm
5Result (C) Top Foil Length
After completing worksheet above fill in A, C and D below. Add “A”
through “F” to confirm total equals your pin-to-pin measurement.
Length Check
Alternate
Measurement
Point A
TOP FOIL LENGTH WORKSHEET
Preassembly Unit 0—Top Foil Length
A
C
D
E
F
Pin
to
Pin
B
Pin
to
Pin
Measure A and add to this chart
and length chart below
Inches mm
A
B.4* 10*
E24 610
F14 359
G
Total A+B+E+F+G
*Add 1" (25 mm) if using a Halyard
Deflector.

12 MKIV Underdeck Unit 0
Preassembly Short Top Foil
If top foil is shorter than 7" (177.8 mm), use one of the following special techniques to ensure sufficient bearing
surface for the foil in the area of the halyard swivel.
21/2(63 mm)
2" (51 mm)
11/2" (38 mm)
1" (25 mm)
1/2" (13 mm)
63/8" (162 mm) No special treatment required.
61/4"–45/8" (159–117 mm) Do not use plastic bushing
above top connector.
61/4"–45/8" (159–117 mm)
41/2"–31/2" (114–89mm) Do not use plastic bushing
above top connector. Shorten top of connector and if
necessary shorten trim cap.
33/8"–25/8" (86–67 mm) Do not use plastic bushing
above top connector. Cut connector right at cross formed
by glue dispersion channels. Use single foil screw in top
foil only.
33/8"–25/8" (86–67 mm)
Under 1/2" (13 mm) Eliminate top foil and run foil higher
in drum assembly.
Under 1/2" (13 mm)
Top Foil
Length from
Worksheet
1. Initial
top foil
cut length
2. Cut through
middle hole in
top foil.*
3. Shorten
full length
adjoining
foil by
cutting
through
middle
hole.*
4. Shorten
connector
5. Shorten
trim cap
Resulting Top
Foil Length Length
21/2"
(63 mm)
55/8"
(143 mm)
41/16"
(103 mm)
31/4"
(83 mm) No
2"
(51 mm)
51/8"
(130 mm)
39/16"
(90 mm)
31/4"
(83 mm) No
11/2"
(38 mm)
45/8"
(117 mm)
31/16"
(78 mm)
31/4"
(83 mm) No
1"
(25 mm)
41/8"
(105 mm)
29/16"
(65 mm)
3"
(76 mm) Yes
1/2"
(13 mm)
35/8"
(92 mm)
21/16"
(52 mm)
23/4"
(70 mm) Yes
21/2"–1/2" (63–13 mm) Shorten top foil and adjoining
full length foil so two screws are used to assemble joint
instead of four. Do not use plastic bushings above top
connector.
*To allow for saw cut, position blade so upper half of
middle hole is preserved.
Cut-Offs – Do Not Use
Cut-Offs
Do Not Use
Cut-Offs
Do Not Use
Cut-Offs
Do Not Use
Cut-Off
Do Not Use
41/2"–31/2" (114–89 mm) 63/8" (162 mm)

MKIV Underdeck Unit 0 13
Preassembly Foil Length Check
Line up bottom foil so foil clamp is just
above or below center of notches in
bottom foil.
Confirm foil length by laying foils alongside
stay with turnbuckle components and torque
tube. Pull stay out straight.
Note: Position top foil so that with top
cap the foil will ride below terminal. If wire
fitting at top of stay is swage, foil must ride
just below shoulder of swage. Mark cut line
on foil. Wrap tape around foil as a guide so
cut is straight.
14" (359 mm)
to underside of deck
If 7301 Halyard Deflector is used, add 1" (25 mm)

MKIV Underdeck Unit 0 15
Assembly Top Foil
Lay top foil in line with others. Slide stay
into top foil and down line of foils or slide
each foil up stay.
Cut out template at right. Line up template
with top of foil and scribed line. Tape in
place. Use a center punch to mark holes.
Check center punch marks to confirm
they are 3/16" (5 mm) and .8" or 13/16"
(20 mm) from top of foil.
Drill two (2) 1/8" (3.2 mm) holes for
trim cap.
3/16" (5 mm)
.8" or 13/16"
(20 mm)
Foil
Top
!

16 MKIV Underdeck Unit 0
Assembly Top Foil
Place halves of plastic bushings on stay so
hooked part of longer section faces out.
Tip: With foil screw holes up as shown
below, place longer half of bushing
with hook on upper half.
Install trim cap. Place each side over wire.
Push trim cap into foil to start, then tap
in using hammer.
Install trim cap screws.
Red Loctite®
Halyard Deflector

MKIV Underdeck Unit 0 17
Assembly Top Foil/Connectors
Slip connector on wire, mating hook of
plastic bushing with connector.
Put a drop of red Loctite®into screw holes.

18 MKIV Underdeck Unit 0
Assembly Foils/Connectors
Hold plastic wedge in place with thumb
as you insert into foil. Line foil holes with
connector screw holes.
Loading Injector with Adhesive
Tip: In cooler weather, keep sealed
adhesive in pocket to keep warm. Use
instructions below to fill injector less
than half way; you will only use a small
amount of adhesive. Refill if needed
but do not keep open sealant for long
periods. Use adhesive within 3 hours.
Use cap of adhesive to break seal. Remove
injector tip cap and plunger. Hold injector
at an angle with applicator tip facing down.
Squeeze adhesive into tube so lower half
of injector is full as shown. Keep tip free
of sealant to let air inside.
Adhesive in
lower half
Start plunger into injector and immediately
hold upright so plunger is down and
applicator tip is up.
As sealant runs down towards plunger an
air pocket will form near tip. Push plunger
to evacuate air. You are now ready to begin
injecting adhesive.

MKIV Underdeck Unit 0 19
Assembly Foils/Connectors
Use bushings, connector, wedge, and
adhesive in other screw hole and insert
into other foil. Use 1/4 to 1/2 ml. of
adhesive.
Use “ml”
marks to
estimate
adhesive
Stop when you see a small
amount of adhesive enter
one of the screw holes.
Inject only a small amount of adhesive
into middle hole. Unit 0 will only take
1/4 to 1/3 of a graduation mark. Do not
press tip of injector into hole. Back off
slightly while injecting.
Tip: When you see a small
amount of adhesive enter
one of the screw holes,
stop. You have applied
enough adhesive.
Red Loctite®
Tighten screws into connector holes. Make
sure a drop of red Loctite®entered each
screw hole. If not, apply to screw.

20 MKIV Underdeck Unit 0
Continue installing connectors and wedges.
Make sure to use adhesive in screw holes.
Continue assembly. Use bottom connector
to assemble bottom foil.
Slide halyard swivel onto foil above feeder
window. Make sure taller “half” is up as
shown.
Assembly Bottom Foil/Connectors/Halyard Swivel
Red Loctite®

MKIV Underdeck Unit 0 21
Loosen foil clamp screws at top of
drum assembly.
Slide drum assembly onto foils.
Tip: Face clamp downward so it clears
foil notches during installation.
Assembly Torque Tube Assembly
Temporarily clamp torque tube to top of
bottom foil, leaving feeder gap partially
exposed as shown at right. Gap will be
used to rig a foil system lifting line.