Proper Lifeline Tension

D

dkinzer

.
Sep 22, 2021
286
Hunter 41AC 0 Portland, OR
I have installed new 3/16" bare stainless lifelines on our 2007 H41AC. The last task is to tension them using the turnbuckles. I'm wondering, however, what the proper tension should be. I'm assuming that they shouldn't be guitar string taut but neither should they be flapping in the breeze.

It is currently cool here in the Pacific NW (highs in the high 40s Farenheit, and lows near freezing) but in the summer it can get to 100* or more. If I make them reasonably taut now, I'm guessing that the long runs (bow pulpit to gate, about 26 feet) may loosen a little in the summer. The coefficient of thermal expansion for 316 stainless is 8.8 microinches per degree Farenheit per inch so the long runs would expand about 3/16" with a 60* temperature change.

Any tips on the adjustment?
 
jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
23,139
CAL 35 Cruiser #21 moored EVERETT WA
Congrats on your new safety lines.
Tension on the life lines are not specific. They are what you desire. As you correctly state, weather and temperature will affect the cables. I find that I set them and adjust them as needed.

It is relatively easy to accomplish. I head forward on the starboard side and they feel good as I pull up on the lifeline. I feel secure and my feet find the deck soundly.

I return on the port side and there is an issue. The line feels loose. I immediately begin to identify why. Is there a stanchion bent or no longer properly attached at the deck. Did someone use the stanchion to pull the boat to the dock or push it away. Could it be that the turnbuckle has slipped a bit since my last sail. What ever it is I address the issue and resolve the safety problem.

I walk the deck and use the life lines every time before I untie the lines.

Straight forward and easy stuff.
 
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Joe

Joe

.
Jun 1, 2004
8,196
Catalina 27 Mission Bay, San Diego
I googled it for you. Most of the responses concur with the following quote I purloined from this piece on lifelines printed in Practical-Sailor.

........."Lifelines should be tight, so tight that they deflect no more than about two inches between stanchions when a force of about 11 foot-pounds is applied at mid-span between stanchions."......
 
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Hayden Watson

Hayden Watson

.
Apr 5, 2009
3,131
Catalina '88 C30 tr/bs Oak Harbor, WA
I like mine tight but you need to watch your stanchions as you are tightening them because they follow a curve, they exert a bending moment on the stanchions and if over tightened will bend them inward.
 
JamesG161

JamesG161

SBO Weather and Forecasting Forum Jim & John
Feb 14, 2014
7,770
Hunter 430 Waveland, MS
I teach new crew to use Life Lines to walk along my deck. [slack per @Joe needed]

You "pull up" on the line till tight, as you walk.

This action keeps your feet on the deck in choppy seas.

Safety Officer Jim...
 
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sailcapt340

sailcapt340

.
Sep 26, 2008
708
Hunter 340 0 Wickford, RI
On my boat I find that the tension changes, sometimes slightly and other very tight. When I connect the lifeline over the entry hatchway after we board the boat from the stern, after lifting the seat. The lines tighten all the way to the front, about 1/2” or so.
When I have two people sitting on the wing seats, the lines tighten even more. In this scenario, its very difficult to open the pelican hooks if we get to a dock and I have to get off the boat.
You‘ll need to do some testing to get them just right.
Fun stuff to do, moving people up and down, and you’ll always be asked by someone “what are you doing?”
 
Last edited:
BarryL

BarryL

.
May 21, 2004
1,067
Jeanneau Sun Odyssey 409 Mt. Sinai, NY
Hello,

US Sailing, Safety Equipment Requirements for COASTAL racing state:

Lifeline deflection shall not exceed the following: a) When a deflecting force of 9 lbs (40N) is applied to a lifeline midway between supports of an upper or single lifeline, the lifeline shall not deflect more than 2” (50mm). This measurement shall be taken at the widest span between supports that are aft of the mast. b) When a deflecting force of 9 lbs (40N) is applied midway between supports of an intermediate lifeline of all spans that are aft of the mast, deflection shall not exceed 5” (120mm) from a straight line between the stanchions.


Barry
 
Tin Kicker

Tin Kicker

.
Mar 8, 2019
111
ODay 322 Bodkin Creek, Chesapeake Bay
BarryL said:
Hello,

US Sailing, Safety Equipment Requirements for COASTAL racing state:

Lifeline deflection shall not exceed the following: a) When a deflecting force of 9 lbs (40N) is applied to a lifeline midway between supports of an upper or single lifeline, the lifeline shall not deflect more than 2” (50mm). This measurement shall be taken at the widest span between supports that are aft of the mast. b) When a deflecting force of 9 lbs (40N) is applied midway between supports of an intermediate lifeline of all spans that are aft of the mast, deflection shall not exceed 5” (120mm) from a straight line between the stanchions.


Barry
Click to expand
This is one of those requirements which while correct, it can be unrealistic in the real world. If you set that 2" under tension now while temperatures are freezing, you are going to either break or bend something on a hot summer day. The expansion of fiberglass is roughly double that of the stainless lifelines so having them too tight could cause a leak at the stanchion fasteners at the front and/or aft ends of the lines.

Definitely good to be aware of the specification but you need to use some common sense.
 
jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
23,139
CAL 35 Cruiser #21 moored EVERETT WA
Tin Kicker said:
it can be unrealistic in the real world
Click to expand
A good reason to set it. Then check it each time you plan to untie the lines.
  1. Smile at your boat as you approach her walking down the dock.
  2. Board your boat and take a stroll to the bow and then down the side.
    1. Notice the feel of the deck
    2. Is anything out of place
    3. ask, How you doing old girl
    4. use the lifelines as you move about
    5. back to the cockpit, open the companion way, begin loading and your checklist of get under way procedures.
It is always good to great your boat. That way she will let you know what is amiss and what she needs.

Not greeting her is just rude.
 
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FastOlson

FastOlson

.
Apr 8, 2010
2,115
Ericson Yachts Olson 34 28400 Portland OR
Perhaps good advice when greeting your spouse, too.... !
"How you doing, old girl?" :)
 
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higgs

higgs

.
Aug 24, 2005
3,710
Nassau 34 Olcott, NY
dkinzer said:
I have installed new 3/16" bare stainless lifelines on our 2007 H41AC. The last task is to tension them using the turnbuckles. I'm wondering, however, what the proper tension should be. I'm assuming that they shouldn't be guitar string taut but neither should they be flapping in the breeze.

It is currently cool here in the Pacific NW (highs in the high 40s Farenheit, and lows near freezing) but in the summer it can get to 100* or more. If I make them reasonably taut now, I'm guessing that the long runs (bow pulpit to gate, about 26 feet) may loosen a little in the summer. The coefficient of thermal expansion for 316 stainless is 8.8 microinches per degree Farenheit per inch so the long runs would expand about 3/16" with a 60* temperature change.

Any tips on the adjustment?
Click to expand
I think you are overthinking this issue. Tension to a point where, in use, you feel comfortable with them and forget about them. Of course check for corrosion over time.
 
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Hayden Watson

Hayden Watson

.
Apr 5, 2009
3,131
Catalina '88 C30 tr/bs Oak Harbor, WA
dkinzer said:
I have installed new 3/16" bare stainless lifelines on our 2007 H41AC. The last task is to tension them using the turnbuckles. I'm wondering, however, what the proper tension should be. I'm assuming that they shouldn't be guitar string taut but neither should they be flapping in the breeze.

It is currently cool here in the Pacific NW (highs in the high 40s Farenheit, and lows near freezing) but in the summer it can get to 100* or more. If I make them reasonably taut now, I'm guessing that the long runs (bow pulpit to gate, about 26 feet) may loosen a little in the summer. The coefficient of thermal expansion for 316 stainless is 8.8 microinches per degree Farenheit per inch so the long runs would expand about 3/16" with a 60* temperature change.

Any tips on the adjustment?
Click to expand
I learned an interesting thing that I learned recently. As an engineer, I need to know the mechanical properties of different materials and almost universally materials increase in volume as they get hotter. In wire this means that the length increases with a rise in temperature. The only product that I know of that breaks this rule is Dyneema. I gets shorter as the temp increases by about the same amount as steel gets longer. This means that if you set Dyneema lifelines in cold weather they will be much tighter in hot weather.
On boats with the Dyneema synthetic rigging, you should retune the rig any time the temperature varies by more than about 30º.
 
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