Twistle rig

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KellysEye

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www.kellyseye.net
I'e finally got around to take pictures of the Twistle rig joint we used. Other pictures have the poles overlapped and tied together which will eventually damage the poles.

I got this from a chap called Dennis Maidment if you want his number please PM me. Alternatively tthe sailmaker Ratsey and Lapthorn should know where to get one.
 
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KellysEye said:
I'e finally got around to take pictures of the Twistle rig joint we used. Other pictures have the poles overlapped and tied together which will eventually damage the poles.
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Sorry for the dumb question but am I right in thinking the two rings are for the up/downhaul and the pole ends lock into the U-shaped straps ?

Also, are they available in different sizes ?

Boo2
 
Rope connection eventually damaging the poles?
Do you have some evidence of this?

I've been a champion of the Twistle rig for years and have provided the knotted joint to dozens of cruising couples and long distance boats. Have never heard that they have suffered damage to their poles.

In fact, quite the opposite! The only problems I have seen have been by people trying to use mechanical joints.
 
It looks to be a comparatively light construction.
I had a stainless steel ring about 15cm in diameter made up from 10mm rod. I then used ropework (Turk's Heads) to hold the various lines and pole end fittings in place.
No moving parts and worked well.
 
Sorry for the dumb question but am I right in thinking the two rings are for the up/downhaul and the pole ends lock into the U-shaped straps ? Also, are they available in different sizes ?

Not dumb at all. The ring on the long shaft goes on to the spinnaker pole uphaul clip. The ring on the shorter shaft goes to a dwownhaul. We rigged the downhaul with a sheet to a stanchion by the cockpit with a jamming block and a turing block tied to the front cleats.

I don't know about different sizes we bought both the poles and hinge from Dennis so he made the hinge for the poles.

Obviously you need twin poles and we couldn't find a deck fitting that took two poles. We did a drawing and took it to a marine stainless fabricator, the price £180. So we took the drawing to a stainless fabricator of commercial kitchens which use marine grade stainless. It was a £80.

>I've been a champion of the Twistle rig for years and have provided the knotted joint to dozens of cruising couples and long distance boats. Have never heard that they have suffered damage to their poles.

The pictures I've seen of rope joints in use show the poles overlapping and rubbing against each other. You are saying it doesn't damage them, which surprises me.

>The only problems I have seen have been by people trying to use mechanical joints.

Never had trouble with ours and used it for around 7,000 miles. What problemse have you seen with what I've shown in the pictures?
 
The two poles in a Twistle rig are under compression. I don't know what size of boat your link is for use with, but from 30ft upwards, the loads on the ends towards each other are quite large. That's the idea of the rig, as the two loads come together and cancel each other out, thereby taking the mast out of the equation.

So the cruciform joints never stay "in column" - they fold up and now the sharp edges are bearing on each other, whereas with the rope connector everything is soft and pliant.

Where the two poles rub a wrap of leather on each and a little Lanacote with provide enough anti chafe for several circumnavigations before the leather needs changing.

Fore and aft lower guys are both important as it gives much better control over the behaviour of the poles.
 
>The two poles in a Twistle rig are under compression. I don't know what size of boat your link is for use with, but from 30ft upwards, the loads on the ends towards each other are quite large.

Our boat was a 38 foot 14 ton long keel ketch. I wish I had put a ruler alongside in the picture, it's about 14 inches wide and heavily built, as you would find if you lifted it.

I'm not sure about large compression loads. The whole rig is free flying, as the boat rolls the sails move together with the roll, obviously there must be some compression but I don't think it's a great deal.

The compression load on a poled out spinnaker is a different ball game, I've seen six broken carbon poles and two torn off mast pole fittings after boats have crossed the Atlantic.
 
KellysEye said:
The compression load on a poled out spinnaker is a different ball game, I've seen six broken carbon poles and two torn off mast pole fittings after boats have crossed the Atlantic.
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Quite, but that's not a function of the size of the load, but the fact that if you fix a pole on the mast it has to absorb the load as the inboard end is fixed. You can use a twistle rig with two cruising chutes and the loads on the pole are exactly the same, but what isn't there is the equal and opposite reaction from the fixed mast.

A simple vector diagram will allow you to calculate the loads in a twistle rig of a given size, in a given wind strength, with the sheets at a given angle. The rig doesn't fail to generate these loads otherwise the boat wouldn't move, but the system resolves the compressive component in the poles in a sympathetic way.

But whatever the magnitude of the compression, it always pushes the end of the poles together and no articulated system can hold them apart. It will always 'jackknife' on itself and then graunch against themselves.
 
TimBennet said:
But whatever the magnitude of the compression, it always pushes the end of the poles together and no articulated system can hold them apart. It will always 'jackknife' on itself and then graunch against themselves.
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That seems obvious to me if there is indeed compression (I don't know enough about the Twistle rig to tell). But Kellyseye would surely know if his gadget spent most of its time capsized - wouldn't he?

Perhaps he can confirm that it doesn't fold in, in which case there must be relatively little inward force on the pole ends in his setup.

Personally I'd go with a rope grommet and leatherwork, more for economy than because I think special fittings don't work. But then I'm quite comfortable with using tallow-coated leather against chafe in gaff and square rig.

Pete
 
> if his gadget spent most of its time capsized - wouldn't he?

I'm not sure what that means.

>Perhaps he can confirm that it doesn't fold in, in which case there must be relatively little inward force on the pole ends in his setup.

The flanges at each end are hinged and they do flex when the boat is rolling which I think helps take load on the poles. Speaking of load on the poles I mentioned with a Twistle rig I didn't think it was much. I forgot to mention that the two poles were half the diameter, with thinner metal, of our spinnaker pole, so on the Twistle Rig there must be much less than half the load on our spinaker pole.
 
I come back to my simple stainless steel ring. There was not a problem with "capsizing" and the system was remarkably stable when sailing directly downwind.
Both sails were ballooning- out which doesn't give compressive forces.From my racing experience ,you only get strong compressive forces when reaching which of course you don't do with this rig.
 
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KellysEye said:
>capsizing

What does that mean?
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Possibly not strictly correct, but one talks about a knot capsizing and this seemed like the analogous thing.

What I mean is the central part of the fitting twisting round through nearly 180 degrees, so that the vertical pivot pin for the starboard pole is on the port side, and vice versa, with the hinged "wings" of the fitting passing ahead or astern (one of each) of the central part. That's what I'd expect to happen if there's significant inward load on the poles.

Pete
 
Pete7 said:
I think he means like this in the video:

http://www.youtube.com/watch?v=sy53gIOrE40
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I don't think so, although it's hard to see exactly what's going on there. I don't think that fitting is the same as KellysEye's - he clips the ends of the poles directly into the "wings" of the fitting, right? The guy in the video seems to have short lanyards involved somehow as well as the metalwork.

Pete
 
>he clips the ends of the poles directly into the "wings" of the fitting, right?

That's correct, if you look carefully at the fitting there is no way the flanges can overlap unlike the fittings used in the videos, which look like a bad idea to me. The flanges are well seperated from the uphaul/downhaul bar and rings.
 
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