AS9100D Certified

Military Critical Technical Data Agreement

Helpful Information:
Rigger’s Guide to proper swaging techniques

How to use PT Series Tension Gauges

HOW TO MEASURE

Figure 1
ModelCable size
Model PT-1Cable size 3/32", 1/8", 5/32"
Model PT-1MCable size 2.5mm, 3mm, 4mm
Model PT-2Cable size 3/16", 7/32", 1/4"
Model PT-2MCable size 5mm, 6mm, 7mm
Model PT-3Cable size 1/4", 9/32", 5/16", 3/8"
Model PT-3MCable size 7mm, 8mm, 9mm, 10mm

Hold the gauge with the left hand and place the cable between the two nylon spools as shown in Figure 1.

With the right hand pull the lanyard and extend the spring until the hook on the nylon slider can be hooked on the cable as shown in Figure 2.

Figure 2

Release the lanyard. Read the needle position on the scale. Refer to the calibration table obtain correct tension in the cable. The gauge can be left on the wire for “hands free” adjusting of the cable.

To assure accurate readings make sure that the slider moves freely in the frame slot and does not bind. Also, lubricate the slider slot frequently with silicone lubricant.

Note: An extra 1/4″ inch hole is provided in the frame of the instrument for an attachment of a short lanyard and snap hook (not furnished) for securing the gauge to the cable. This will prevent loss of the instrument if it becomes inadvertently detached.

HOW MUCH TENSION?

Specific tension requirements for your application must be obtained from the boat, mast, or sail manufacturer or the manufacturer of the product on which the cable is used.

Table 1 recommends an initial tension setting, but there is no simple solution since the optimum rigging tension will be a function of the boat design, the rig (masthead or fractional, one or more spreaders, etc.), and even the cut of the sails. Many skippers use insufficient tension because of a fear of “breaking something.” It should be noted that on America’s Cup contenders, where electronic state of the art tension instrumentation is available, the standing rigging is set as tight as is structurally feasible.

Table 1
302/304 1x19 Stainless Steel Rigging Cable
Diam., In.Breaking Strength PoundsForestay* PoundsShrouds* Pounds
3/321200180120
1/82100320240
5/323300500350
3/164700750500
7/3263001000700
1/482001300850
9/321030016001050
5/161250020001300
3/81750027501850
*Suggested initial settings.

ONE DESIGN CLASS RACING SAILBOATS

Most sail makers who produce sails for the one design classes provide each purchaser with specific set of readings on the Loos Model A or Model B tension gauges for use when setting up the standing rigging. This assures that the sails will have the correct shape when the rig is under load.

For the convenience of sailors who wish to upgrade from our Model A or B gauges to the professional model (PT-1, PT-2, or PT-3) gauges we include below a conversion chart so that the same recommended tension can be obtained with the PT-1, PT-2 or PT-3 gauges as with the Model A or B gauges.

MODEL A
MODEL PT-1MODEL BMODEL PT-2MODEL PT-3
SCALE3/321/85/32SCALE3/167/321/49/32
56  1011   
109  1513   
151214 1815   
201616 201618  
252019 221820  
282321 241922  
30 22 262124  
35 2725282325  
38 302830252725 
40 333032272927 
42  3334293139 
44  3636 3331 
45  3838 36336
46  3939 37347
47  4040  369
    41  3710
    42  3911
    43  4012
    44   14
    45   16
    46   18
    47   20
    49   25

When no specific requirements are provided by the sail maker, the following general comments will provide a basis for a rational procedure for tuning the rig.

FORESTAY TENSION

Masthead Rig

On the masthead rig it’s almost always advantageous to set the forestay tension as high as possible within the limits of structural strength. Generally, it’s possible to use 15% of the breaking strength of the cable. Thus, a forestay tension of 1,000 lbs. is a reasonable place to start with a 7/32″diam., 302/304 1×19 stainless steel cable. Backstay tension would, of course, have to be adjusted to maintain a straight mast with the desired forestay tension. Since the backstay makes a greater angle to the mast, the backstay tension will be lower than the forestay tension.

NOTE ! ROLLER FURLING CAN ONLY BE SET BY BACK STAY TENSION.

Fractional Rig

In a fractional rig the forestay does not go all the way to the masthead and forestay tension cannot be directly balanced by tension in the backstay. Therefore, some mast bend is generally accepted and the mainsail is cut to fit the bend. A forestay tension of at least 15% of the cable strength is desirable. However, if this results in excessive mast bend it will be necessary to back off a bit. On some fractional rigs, diamond shrouds are used to reduce mast bend.

UPPER AND LOWER SHROUD TENSION

Masthead Rig

There is a simple criterion for shroud tension. The initial rigging tension should be high enough that the leeward shrouds do not go slack when sailing close-hauled in a reasonably brisk breeze. The proper value for your boat can be found by a few trial runs under sail. Once the correct tension is known, the gauge can be used to maintain the value.

For many boat designs a shroud tension of 10% to 12% of the breaking strength of the cable is adequate. Thus, for 7/32″, 302/ 304 1×19 stainless steel cable , the upper and lower shrouds would be set to 600 to 700 lbs. tension. On some rigs it may be desirable to carry more tension in the uppers than in the lowers.

Fractional Rig

For most fractional rigs the correct shroud tension is the same as that for a masthead rig, i. e., a tension setting that will keep the leeward shrouds from going slack. However there is one exception. On certain fractional rigs , the upper and lower shrouds lead to chain plates that are aft of the mast. The spreader is swept back. For such a rig most of the forestay tension is balanced by the upper shrouds. A shroud tension of approximately 20% of the cable strength may be required to achieve the desired forestay tension. Never exceed 25% of the cable breaking strength. (Refer to the breaking strength chart Table 1.)

NOTE ! THE INTENDED USE OF THIS GAUGE IS TO BE USED ON 302 / 304 1x19 S.S. CABLE IN APPROPRIATE SIZES. IF USED ON OTHER CABLE TYPES, SIZES, AND CONSTRUCTION YOUR READINGS WOULD BE CONSISTENT (REPEATABLE) BUT POUND TENSION VALUES WOULD DIFFER FROM THOSE LISTED ON THE LABEL. GAUGE MAY NOT READ "O" WHEN AT REST, AS THEY ARE CALIBRATED AT MIDRANGE OF TENSION.

NOTE ! IF FLAT SPOTS APPEAR ON NYLON SPOOLS AFTER EXTENDED USE, ROTATE NYLON SPOOLS 45°.

ADDITIONAL SCALE READINGS

LBS. TENSION
 
CALIBRATION PLATE
MODEL PT-1
CALIBRATION PLATE
MODEL PT-2
CALIBRATION PLATE
MODEL PT-3
SCALE3/321/85/323/167/321/41/49/325/163/8
570     550   
680     600   
790     700   
8100     770500  
9110     830550  
10125  180  900600320 
11135  240  1000650380 
12150100 270  1100720440 
13160110 300  1200780500 
14170125 330  1300830550 
15185135 370  1400900600200
16200150 420  15001000680230
17220165 450  16501080740270
18240180 500  18001150800290
19260200 540  20001220870330
20280220140590320  1300950360
21300240155640360  14201050380
22 260170700410  15401130420
23 280185770450300 16601210480
24 300200840500350 18001300530
25 320220920560400 19601400570
26 3452451030630450 21301500600
27 3702651110680500 23001600650
28 3903001240740550 25001700720
29 420320 820600  1850800
30 450335 890660  2000870
31 475360 970720  2200930
32 500390 1060780  24001000
33  420 1180840  27001100
34  450 1300900  30001200
35  480 14801000   1300
36  520 16801100   1400
37  560  1200   1500
38  610  1300   1650
39  700  1600   1770
40  800  2000   1900
41         2100
42         2230
43         2400
44         2620
45         2850
46         3100
47         3400
48         3700
49         4100
50         4500
ADDITIONAL SCALE READINGS

KGS. TENSION
 
CALIBRATION PLATE
MODEL PT-1 METRIC
Kilograms
CALIBRATION PLATE
MODEL PT-2 METRIC
Kilograms
CALIBRATION PLATE
MODEL PT-3 METRIC
Kilograms
SCALE2.5mm3mm4mm5mm6mm7mm7mm8mm9mm10mm
850         
954         
1058     300   
1162  95      
1266  110  360200  
1370  120   220  
1475  140   240  
158270 150  480270  
169075 170   300  
1710082 180  550330  
1811090 200   360  
19120100 220  630400  
20130110 240   430  
2114012070260    460 
22 13076280160 790500  
23 14083310180  540  
24 15090340200 900590  
25 160100370210  630370 
26 170115400230 1100680410 
27 180127440250  720440 
28 190140490270  770480 
29 210150550290  850520 
30 220160620320220 920560 
31 235170 350240 1000590 
32 250180 380270 1100630 
33  195 420290 1240700 
34  210 460320 1400750400
35  225 510350  810430
36  240 570370  870460
37  260 640400  940500
38  280 730440  1020540
39  320  470  1100590
40  360  510  1190630
41  610  550  1300680
42  700  620  1420730
43  800     1600790
44         870
45         940
46         1000
47         1090
48         1180
49         1270
50         1360
51         1500
52         1640
53         1800