What size Dyneema to replace wire centerboard cable on Pearson 36-2?
Darren Carlton
Helen Tacha
Upgrading to Dyneema for your centerboard cable is a great idea, considering its strength, durability, and resistance to wear. When replacing steel wire with Dyneema, you'll want to ensure the new line has sufficient strength and the right diameter for your setup.
Given the 5/32" diameter steel wire has a breaking strength of around 2,400 lbs, you'll want to find a Dyneema line with comparable strength. Dyneema's strength-to-weight ratio is exceptional, so a smaller diameter might suffice.
Some general guidelines for Dyneema diameters and strengths are:
- 3/16" (4.8mm) Dyneema: around 4,000-5,000 lbs breaking strength
- 1/4" (6.4mm) Dyneema: around 7,000-8,000 lbs breaking strength
Considering your current wire's breaking strength, a 1/4" (6.4mm) Dyneema line might be a good choice, offering a safety margin and sufficient strength for your Pearson 36-2's centerboard.
Before making a final decision, consider factors like:
- The specific Dyneema product's strength and durability ratings
- The winch's diameter and design
- Any potential chafing or abrasion points
It's also a good idea to consult with other Pearson 36-2 owners or a sailing expert familiar with Dyneema upgrades to ensure you're making the best choice for your boat.
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Guy Johnson
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Subject: Re: [pearson ] What size Dyneema to replace wire centerboard cable on Pearson 36-2?
Darren Carlton
Peter Nielsen
On Jun 2, 2025, at 23:15, Darren Carlton <darren....@gmail.com> wrote:
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Darren Carlton
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Guy Johnson
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Dan Pfeiffer
Couple more things...
You basically can't get a dynema line that is not stronger than the steel wire for the CB. So no issue there.
You should use a spliced eye in the end for attachment (splicing dynema is easy). Any knot might not hold well with the slippery dynema and you will loose 50% of the line strength. But don't forget to account for the increases diameter at the splice. be sure it will fit over or through whatever it needs to.
Running to a stopper and a regular winch (with a cover as Guy suggests) means you can have that winch do other things too (like handling reefing lines?). That's very useful. But if that's not what will happen and the winch is dedicated only to the CB then I would consider sticking with the reel winch. You can use it with the dynema and it's one less line tail to deal with.
Also, be sure a small dynema line can't jump a sheave and jam. Should be fine if it's not less than 1/2 the wire diameter? But be sure.
Dan Pfeiffer
Dave Cole
Why would you want to do this? What is the advantage? Weight doesnt matter. I can see big advantages if its going aloft and your a racer. But for something that just needs to function, I dont see the point. What happens if this line fails?
I understand that Dyneema only has decent abrasion resistance because of the jacket. It does not do well with shock loads since it doesnt stretch.
Dave
10M #26
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Darren Carlton
In my case, I'm seeing early wear on the wire cable where it wraps around the winch. I assume this is because wire isn't designed to wrap around a winch. The original owners manual mentions a wire-to-rope splice, with the rope going around the winch.
Dyneema is both strong and flexible, so it seems like the right choice, and saves me the extra work of a wire to rope splice.
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Dave Cole
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Dan Pfeiffer
I would pick dynema over wire spliced to rope (as in 7x19 wire spliced to double braid). That was old tech in 1990. I like the idea of dynema on the reel-type winch. If the dynema fails the same thing happens as when the wire fails. CB is down. And shock loads? Like from what with a center board lift? And even so I would expect properly secured dynema (with proper eye splices - easy) to perform as well or better than wire of the same size in shock loading? It will have more than 2x the strength for a higher safety factor. And the issues of construction stretch, or pre-stretch, or heat setting are not going to matter for this application.
I have a #5 jib (about 55% of foretriangle area) for properly windy days. It is maybe 2/3 hoist. A wire pennant on the top would be the old way of setting this sail so the roller furling swivel is up at the top of the foil. I used 3/16 dynema rather than wire. A big improvement for handling the sail. Not exactly the same as a CB lift cable but similar substitution of dynema for wire.
Regardless of the choice it's likely that other components in the system (blocks, sheaves, fairleads, winch,...) need refurbishment or replacement. Whatever the line or wire is it needs to run clean and fair or it will fail.
Dan Pfeiffer
Michael Cyr
Darren Carlton
27’ of 3/16” (5mm) Dyneema. SK-78 or HTS-78. This includes the line needed to create the eye splice, plus a few sacrificial feet for practicing knots and splices. I purchased 50’ of AmSteel Dyneema® AS-78 Single Braid from West Marine and had 23’ left over
3/16” stainless steel thimble
Clevis pin for centerboard pennant (in case the old one is damaged). ⅜” thick,
either 1” long or 1 ½” long. My calipers measured 1.4 inches of length for the current pin, but that doesn’t appear to be a standard size. 1 ½” is a little longer than needed, but might be what I would use.
Process
At one end of the Dyneema rope, create an eye splice with a thimble inside.
Use a Brummel locking splice.
Taper and bury the tail 72x the width of the rope. For 3/16” rope, the tail should be 14”. I saw this “72x” number mentioned on a few websites and videos. Not sure if there are official recommendations from Dyneema manufacturers, so I’m just following the herd here.
Here are a couple of videos that demonstrate the Brummel eye splice:
- https://www.youtube.com/watch?v=UpkqJ4GRfSg&t=467s&ab_channel=RiggingDoctor
- https://www.youtube.com/watch?v=buZypu8LP5g&ab_channel=BottomUP-Boatshttps://www.youtube.com/watch?v=buZypu8LP5g&ab_channel=BottomUP-Boats
Haul the boat and drop the centerboard all the way down. The pennant connects at the top of the centerboard. There are two metal plates (tangs?) that are attached to the centerboard. A clevis pin runs between them and the pennant goes around the clevis pin.
Use the old cable to pull the new one up through the centerboard trunk onto the deck. Here’s how we secured the steel cable to the Dyneema rope: Use some whipping thread to tie/sew the pennants together, then apply a single layer of masking tape (thin and flexible) over the temporary splice. Say a little prayer.
Up on deck, the winch for the centerboard cable has a hole for the pennant to go through. A stopper on the end of the pennant secures it to the winch.
3/16” Dyneema was too thick to easily push through the hole. So I:Removed 4 strands from the last 8 inches or so of the rope.
Pulled the thinned rope through the hole.
Once I got the rope started, the full rope with all 12 strands fit through the hole.
I pulled through enough line so that the winch is almost fully wrapped before the line takes on any strain. When the line takes on strain, it makes 2 wraps around the bare winch, then makes 2 more wraps over itself to fully raise the board.Tied a figure 8 stopper knot
To secure the tail, I
Buried the cut edges inside the rope. That is, I turned the last 1” of rope inside itself.
Whipped the end.
Melted the exposed end. Maybe this wasn’t necessary.
Looped the tail around the winch and sewed it to the first wrap. I’m not very good at this, so it’s not as pretty as it could be.
Time to go sailing!
Dan Pfeiffer
Excellent work! And excellent report! Time to go sailing indeed! We'll done!
Dan Pfeiffer
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