The limiting factor for centerboard cable is the diameter of the drum onto which the wire rope is spooled at the top. This is also why you should absolutely only use the recommended 7 x 19 stainless steel cable—for its flexibility.?

Larger cable, or cable made with fewer strands, will stress from bending around its take-up spool and quickly fail. Look up wire rope shives for more data on allowable bending radii.?

Dyneema is more chafe resistant than you would think and won’t part from rubbing even sharp edges for long periods ALONG its length, but is easy cut with a concentrated force with a very sharp edge ACROSS its length.

This stuff continues to amaze me. I’m rebuilding my centerboard now. There’s more to think about, but I’ll be strongly considering dyneema.?

Good luck with your centerboard.?

Alan Schaeffer?

1968 T27?

On Jan 25, 2020, at 9:15 PM, Caleb Davison via Groups.Io <calebjess@...> wrote:

Jeremy,

I think Warren has pointed out why it might not be so easy to just upgrade the size of wire rope (thanks Warren).

My information.html (file in the files section) says that the centerboard pennant is made up of 10' of 1/8" wire rope + 12' of 1/4" rope.? I don't think that the 1/8" wire rope even has to have a fancy weave like the 7x19 specified for the standing rigging - plain old 1/8" wire rope with however many strands it is made up with should do fine.? It may be worth spending a little extra on a SS version, if such does exist, as the wire attached to the centerboard will see frequent amounts of time in the water and will be likely to corrode/rust expecially up against dissimilar metal fittings.? So whatever material your wire rope is it should be compatible (the same) as the fittings/swages you may use.

There is a good reason that Tartan did not use dyneema originally for this application; dyneema would not be invented for another 40 or so years after production of these boats ended.? High tech high strength lines are a relatively recent newcomer in the rigging world with many applications that make sense on a boat, and many that don't make sense since dyneema wont hold most conventional knots.? What I love about Dyneema is it's low weight, super high strength (1/4" dyneema breaking point is around 6000#s) but it can easily be cut by a razor blade or knife, and thus is more succeptible to chafing than any wire rope.? I have also seen my centerboard trunk covered in barnacles after a season in our brachish/salty waters and we all know how sharp barncles can be.? For this reason alone I think that dyneema is unsuitable for this application (but you are more than welcome to try it out), I also think this system should have had a sheave for the wire rope just inside the centerboard trunk to keep it from sawing away at the inside of the trunk.

Best.

Caleb D.

T27 #328

-----Original Message-----
From: Warren Stein via Groups.Io <wrsteinesq@...>
To: T27Owners <[email protected]>
Sent: Sat, Jan 25, 2020 8:14 pm
Subject: Re: [T27Owners] What size wire rope do you use for the centerboard pennant?

I think the limiting factor may be the size of the hole at the edge of the center board. At least on my centerboard, there is a hole crossways, i.e. oriented as the hole for the pin; but there is also another hole, smaller, which runs from the aft edge of the center board perpendicularly and intersects with the crossways one.? The pennant enters the smaller hole and can push out either side of the crossways hole, so one can put a swage fitting on it.

This means that a bigger pennant requires a bigger hole.? And there is only so much Centerboard thickness to work with.? So I think thats the real limit.

> On Jan 25, 2020, at 5:46 PM, jeremy@... wrote:
>
> ?
> Hello,
>
> What size wire do you use for the centerboard pennant. I originally ordered the replacement cable from Tartan, but it seems it is only 1/8". That has a working load of 340lbs and a breaking strength around 1760lbs -- so, it should be plenty. But is it worthwhile to go up to a larger size ?
>
> At what point is the diameter too big?
>
> I know some people are experimenting with dyneema, but I am going to wait to hear how that works out before making the switch. Among other things, last time I got hauled out I couldn't drop my centerboard because a bunch of mussels, barnacles, or other hard, pointy things started growing in the centerboard trunk and actually jammed the centerboard in place.
>
> If those things started scraping on my centerboard pennant, I think stainless steel would fair better than dyneema.
>
> - jeremy
>
>