Super Anarchist
Sydney mostly
Pretty interesting day.

I'm very empirical, so I like to do my own tests.
Today I started loading up M4 DM20 SK99 , to find out about stretch and creep.
I'm using Marlow, mostly because I own a roll of it, I'm sure Liros is just as good.
Just so people are sure of what I am using.

And yes that is a roll of Liros that I am using elsewhere.

So this M4 DM20 SK99 has a rated BS of 2220kgs.

I have a hydraulic pull ram, that is rated to 5 tonne, and oil pressure gauge on it so I can work out how many tonne I am exerting.
Do a spice, and these were short, what I call painters, they transfer the lever/cascade 40:1 purchase to the M3 DM20 SK99 Cap shrouds.

First thing, until I exceed 1.5tonne, nothing settled, it was like a bit of elastic.
Once I took it past 1.5 tonne, I got initial creep of about 8mm per splice, it grew over 5 mins, load it back up again (to 1.5 tonne) and I got another 2mm creep, but that was it.
Held 1.5 tonne for well over an hour, with no drop in pressure.

Dropped the pressure to zero for an hour, came back, loaded it back up to 1.5 tonne, got about 2mm creep, back to 1.5 tonne, stay there for way past an hour, no movement.

So my D2's are likely to be this M4 DM20 SK99 and they have a working load of 5650N (about 580kgs).
My D3-V3 (primary shrouds) are going to be M5 DM20 SK99 (BS = 2870kgs) and they have a rated loading of 6550N so about 670kgs.
Absolutely I will exceed these numbers, launching off a wave and slamming into the next, but I have approx. 4:1 safety margin, what ISO would call 400% factor, and it's days like today that give you a lot of confidence in what you are doing.

It would be interesting to find out what it breaks at, but I would need a far bigger power pack (Hydraulic pump) and a gauge that goes way past 5000psi.

My point being, that unless you take this stuff and take it to approx 75% of BS, then your likely to have elastic shrouds.

Just to give you an idea of the load I'm putting down this M4,

That's a 5/16" or M8 shackle, its a RF636 rated "point load" of 2700kgs, BS is 3600kgs.
It's also a M8 ring. Not round anymore, it's a RF125 with a MWL of 700kgs and a BS of 3500kgs, it's fared better than the shackle.
That shackle had to be hack-sawed off, the pin was frozen.

And you can see the M4 (Black) hanging off the RHS.
The white rope to the LHS is 4 wraps of M5 SK78, not sure who's but its bullet proof.
This shot was taken at 1.5 tonne of load.

Broke some M3 SK78 (at approx 1400kgs), that was unintentional but exciting all the same, and almost 50% above the rated BS the manufacture (Liros) quoted (990kgs). Something tells me they are being very conservative.

The distortion of the shackle is impressive, I can measure accurately to 1 tonne, 1100kgs at a stretch, this was way beyond that.

More fun tomorrow.

I should lay-up the laminate of the fin tomorrow.
Had a disaster last week, 8 layers of wax, plus a test and the Rudder stuck, mould is back with the miller for a re-mill.

So tomorrow, maybe another 4 layers of wax and a layer of PVA surface release film, and suck the laminate into the fin.
I will try and film it, so I can post it here.



Super Anarchist
Sydney mostly
I have 10 sitting on my desk.
I need 4. and a few spares.
I can spare 4, but if you want more, I can get them sent directly from HK.
If you go back up the string you will find Sean Lam, I can contact him for you.
Or PM me and I will give you his contact details.

But let me find you a price first


Super Anarchist
Sydney mostly
where can i get these spreader ends from? They would be mint on my new mast
Lamgav, they are $USD25 each (set). So one SS loop and one 3D printed seat.
As commented black bit is 3D printed, so if you have a accurate profile or the end of your spreader the 3D printing can be tweaked.

If you order 200 of them, price 1/2ves, normal, normal, same!
Either SYD or HK shipping, so add FedEx or DHL from there.


Super Anarchist
Sydney mostly
So a bunch of questions.

N [Newtons) -> Kgs, divide by (I assume) gravity 9.8m/s/s or just divide by 9.8.

So yes, my main shrouds will be M5 DM20 SK99 (BS = 2870kgs) so I will have to take them to approx 2 tonne, to "season" then.
More scary is my fore-stay, which is M6 DM20 SK99 (BS = 4000kgs) so I will need to get it to 3 tonne, to "season it".

I have opted for a M6 forestay because it's up inside the luff of the jib anyway, and it takes some abuse. Max load on the F/Stay is likely to be 6200N so about 650kgs, so over a 6:1 safety margin but the only scary thing will be getting 3 tonne on it.

Yes we did lay-up the fin today, no I did not film it, I'm simply not smart enough, need Alex for that.

Lesson of the last few days, if your going to use Polyurethane paint, use the 2:1 variety. It goes hard and cures fully.

The 4:1 (mixing ratio) dose not appear to be as "complete"!


@JulianB I am wondering that you are sizing your standing rigging for breaking load and not for stiffness. We actually tried to replace ours a few years ago and found that the effective modulus of dyneema and especially DM20 is only about 50% that of standard wire. Hence we increased the diameters to maintain stiffness.

We also found out the hard way that the stuff stretches enormously. Initially we had a rigger tension it with a winch and it came out short. Tried to adjust it and we almost lost our rig as it stretched enormously when the splices resettled. We send it back and it was put on a hydraulic test bench which also destroyed the M8 shackle on the headstay. It still did not fit afterwards and we abandoned the idea as we wanted to go sailing and not have our boat sit in a marina without a useable rig. So if someone is interested in lightly used 8mm and 6mm DM20 with fitting Bluewave terminals and turnbuckles DM me.


Super Anarchist
Sydney mostly
Re talking about BS, solely in the capacity that the rig will lurch and I know from old 18teen days you need at-least 200% safety margin (interesting ISO has settle on 220% and I would agree with that). Old 18teen days, the Forestay, if you used M3 or M3.2 (old 1/8") you got at best 3 months out of a forestay. Use M3.5 (we had to get it specially made and imported and then drill out 1/8" eyes and T-Ball with number drills) and you got 2 years.

Re Sports-boats

Can't talk about Vivace, he rigged and stayed away from the main bunch in Airlie.
i) Skeeter had Dynema Cap Shrouds.
ii) Lamborghini (Dave Lambourn) has all Dynema rigging, everything, and he made a comment that, and I will quote as best I can remember, "I'm a cheap shit so I used SK78".
Rob Bridge who sails with Dave, also commented that a) you have to "season them" and b) you get to an event, you put the rig up, but you can't hit your numbers (ropes have shrunk) so you pump the mast up (they have a hydraulic ram under the mast), come back 5 mins later, back the ram off, shorten the rig up and you back to your old numbers.
iii) all the testing we did with the 49er, and this was M4 DM20 (which is why I have a roll of it) vs M3 Bridon Dyform (49er For-stay) was that seasoned M4 DM20 out performed M3 Dyform massively in terms of strength but better or equal in terms of creep and stretch.

Way back in 2011, (infact I 1st did it back in the early 1900) I took a bit of M4 Dyform, which is the std wire on a 49er and then (1900's) an 18teen and did a controlled stretch. On a 49er D1, going from a Loogs gauge of about 5 to a load of 40 which is about 1/2 BS but a normal sort of load on a 49er D1 we got 8mm of movement. So this is a well seasoned wire, it had 50-100 sailing hours on it, all the oil/grease used in manufacture had been squeezed out, and between say 50kgs and 500kgs that wire which is about 1860mm LOA moved 8mm.
So in a 49er fore-stay, which is 8m LOA, you could deduce that you could get 20mm of movement.

OK, neuronz, your right, I did not measure displacement the other day, I simply relied on the maintenance of (oil) pressure in my ram and I have made the assumption that it did not creep because if it had, I have assumed that the pressure in the oil would drop.

I think I am on very solid ground, but there are some scenarios where oil pressure could be maintained while length grew, not many, but some.

I can see another test coming up.

From my POV the big advantages of DM20 are weight, simplicity and usability (much kinder to bodies, horrendous experiences with rod on 18teen).

Need to go find a 49er D1 and do a M3 test piece of rope and do a comparison, but thinking about that, even if I use M4 DM20, if I choose to opt up one size, it's still all relevant, my 3 key benifits (weight, simplicity and usability) still hold at a bigger size.



Super Anarchist
Sydney mostly
Talk about quick off the mark. Picky picky picky.

I said M4 for the 49er, that was a error,
The 49er uses M3 Dyform on the Fore-stay, Primary shrouds and D1's. It uses M2.5 Dyform on the caps.

Re weight, if I used Dyform based on what say Skeeter uses I would have:

M6 Dyform Forestay, 10m which would weigh 10 x 0.194 (kgs/m) so approx 2kgs.
M4 Dyform Caps = 12.5 x 0.088 x 2 =2.2kgs
M6 Shrouds = 9 x 2 x 0.194 = 3.5kgs
M5 D2's = 2 x 5 x 0.135 = 1.35kgs

Total is 9.5kgs

I am using
M6 F-stay, DM20 so 10 x 0.00214 (21.4gms/m) = 0.24kgs
M3 Caps DM20 = 12.5 x 2 x 0.00055 = 0.0135 kgs
M5 Shrouds DM20 = 9 x2 x 0.00139 = 0.25kgs &
D4 DS1's DM20 = 5 x 2 x 0.00096 = .0096kgs

Total is about 1kg (not 100% sure of my maths, not my strong suite, if someone can check, appreciate it)

The ends are the ends, I'm hanging my F-Stay and Primary's of a 25 x 2.3 mm Ti Tube, 47gms which is then pin through the mast with a 20mm Ti bar (112 gms).

D2's are hanging off just the 20mm bar. (112 gms)
Caps the same M8 bolt in the mast head fitting regarless of whether it Dyform or DM20.


My Ti TC4 tube and bar.



New member
Scillyjosh, needs to stress mine is functional, I don't care about perfection with stuff like this, so if your a looks man, then get it done in the UK.

But I have this relationship with Sean Lam, he is Hong Kong Chinese, met him sailing B14's maybe 30 - 35 years ago.
The important thing is his mother tongue is Cantonese, and all of industrial Asia speaks technical Cantonese.
He also speaks fluent technical English and Mandarin. He lives in HK, his kids live/ go to school in Vancouver.

For the last 10 - 15 years, he and I have been generating all sort of fittings and he gets them from everywhere from Taiwan through to Malaysia. Some of the stuff he dose for us on the 49er he buys the raw stock, say POM (Acetal) 70mm rod in Japan and has it shipped to Vietnam to be machined.

So if you can generate a DFX or igs file of what you want, he can get it made.
And he can get it made in anything you want, Ti, SS, POM, 3D printed, steel, you name it, he can make it happen.
If you can't do dfx or igs, but can do a "mud-map" he can probably generate a cut-file, you OK it, you get a price and it happens.

Happy to pass on his contact details if your interested. Mostly he operates on WhatsApp.
I'm after nothing more than functional! It would be great if you could message me his details - I'm a mechanical/robotics engineer by day so CAD files etc are all easily supplied. Plus always handy to have new contacts in manufacturing!


Re weight, if I used Dyform based on what say Skeeter uses I would have:

M6 Dyform Forestay, 10m which would weigh 10 x 0.194 (kgs/m) = 1.94kgs.
M4 Dyform Caps = 12.5 x 0.088 x 2 = 2.20kgs
M6 Shrouds = 9 x 2 x 0.194 = 3.49kgs
M5 D2's = 2 x 5 x 0.135 = 1.35kgs

Total is 9.0kgs

I am using
M6 F-stay, DM20 so 10 x 0.0214 (21.4gms/m) = 0.21kgs
M3 Caps DM20 = 12.5 x 2 x 0.0055 = 0.01kgs
M5 Shrouds DM20 = 9 x2 x 0.0139 = 0.25kgs &
M4 D2’s DM20 = 5 x 2 x 0.0096 = 0.10kgs

Total is about 0.6kgs (not 100% sure of my maths, not my strong suite, if someone can check, appreciate it)
Fixed in bold italics…… Maths isn’t my strong suite either…… Not sure what is.
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Super Anarchist
Sydney mostly
I was in getting some rope and low friction rings today and got taken to task for not up-dating SA often enough as people are living vicariously through the forum and boat.

So a little taste.


Blue rope is the Jib Halyard, I'm going to slide the jib up and down the luff wire to alter jib-sheeting angle. Jib-halyard is 8:1, you can see the Allen Ball-race block with a hook, attached to a double, hence 8:1.
Purple rope is spin-halyard.
The quadruple block at the base of the mast (also a Allen Ball-Race) turns Vang, Outhaul and Downhual backwards into the cockpit.
Using 3 at present, I have a 4th crazy idea pending!
Downhaul is hanging down into the boat (white with RF block on the bottom) as is the outhaul (black).
Vang is 16:1,You can see it (white) at the top leading off to the left. Down and out-haul are both 8:1


Bright orange is the Jib downhaul, on the deck, also 8:1, rational is if you want to move the jib up 20mm you ease the downhaul 160mm and pull the jib halyard (blue) 160mm, do it in a tack or ease the fine tune jib sheet (blue and white, 4:1) 200mm.
Red arrow is the business end of the caps shrouds, that's the M4 DM20 that I went to 1.5tonne on the other day, that attaches to M3 DM20 with a BS over 1200kgs. Max expected load is 3000N so about 340kgs, nice 4:1 safety margin.
Grey rope infront of the orange is jib angle, the self tacker is set up to be able to set the jib anywhere between 12 - 6°. The idea is either set max BS and then point higher so as not to exceed or set it outwards and blow past HS. Optimum is likely to be around 8° AoA.


Floor cluster Red is Vang, Blue is Downhaul, white is Outhaul, Yellow is Capshrouds (red arrow in previous render) which has in-excess of 40:1 on it mostly via a 6mm thick carbon lever. Blue/white is jib-sheet coarse (2:1) tune (through a 49er/29er type RF cleat).


Swingstraps (individual) and string leads, the slive "plug" fwd is a really nice Allen fitting, (A8739-18) that will carry the 2nd Z part of the spin sheet, and they will be a RF 56101. 1st part of the Z will be a RF 62100, Only ratchet up to this sort of load, we used to call them Fredrisksen's (Danish), really great blocks.


Pole is also fitting, we go almost 3.15m extension in-front of the Jib Tack, single line launch system, so pull one rope, spin goes up and out and pole also goes out, spinnaker tack line become the bob-stay (2:1). No ropes down inside the pole at all.

In some ways I am lucky as I am not wedded to any single fitting manufacture, I probably have spend most with Allen, but only just a tad more than I have spent with Harken and Ronstan.

Horses for courses, I am being very selective even when buying low friction rings.

And then you have these Nodus fittings, and Wichard reefing hooks.

The really big up side is there has been some serious investment in design by all of these guys, huge life in design quality!

That's me, blowing core for the fin at present, and 3rd time lucky, but 2nd (biscuit) is user-able.

Boat goes to RANSA in 10 days, I go to Europe in 13 days, got my sister wake in the middle.



Super Anarchist
Sydney mostly
For the synthetic rigging isn't it recommended to have a larger turn radius?
Hi Solo, had a few people come back with "what is my protocol WRT splicing synthetics" so this is my take.
And I hasten to add, not advocating this, just that it seems to work and I have had no failures to date.

There is a y-tube clip out there somewhere and it points out the obvious, if you splice a rope, the weakest point is not the end of the loop, it is were the spice starts! Same goes for wire, and remember I come from a aviation background where control surfaces used to be driven by wires and the advent of the terminal swage dropped the wire weight by 30-40% just because of the reduction in failure rate over crimping were the wires come together (in a crimp).

In-fact, the "loop" is operating at 1/2 the load that the un-spliced rope is, so minimum radius's are a bit of a furfy.
WRT my Primary shrouds which are M5 DM20 I am simply slip-knotting (hitching) them around a Bluewave 31908AF (Danish) turnbuckle and I have picked that fitting for 3 reasons. (https://bluewave.dk/catalogues-and-technical-guides/ page 48)
a) A M8/5/16" pin and that's what most Sportsboats have.
b) It has a "rated" BS of 2200kgs but I have tested it and some M5 DM20 to way above that level, the M5 DM20 has a nominal BS of 2800kgs but my expected max load is not likely to exceed double operating load, so 2 x 6550N (approx 670kgs) so approx 1350kgs. &
c) It is designed with a very nice round "eye" 7mm in Dia. (I measure it as 8.2mm BTW, 7mm is whats in the catalog)

If you go back a few posts you will see my M4 DM20 wrapped around a 5/16" shackle taking 1.5tonne, the body of that shackle is about 5mm Rad, and that was a single loop. I plan on making the rope removable from the turnbuckle so I will inevitably have a double hitch, so I will have a double loop, so 1/2 the load again.

It has been suggested that I use "fancy" hitches like this, but my testing to-date would suggest that they are NOT warranted. The idea is that there is less crimp, and that dose have merit, but, I am not seeing any failure in testing with a simply hitch. This is a BW Turnbuckle BTW.

My D2's will also be the same Turnbuckle, but M4 DM20. (Designing also for 2 times operating load so 2 x 5650N.)
My D1's will be the smaller Turnbuckle, M6/1/4" threads/pins but still M4 DM20 rope. (I'm not expecting my D1's to ever exceed their expected operating load of 2000N) Using M4 DM20 because I have it and for stretch.

All of the above being true, these are my general rules!

a) try not to go small than 1.5 time the Rope diameter were you terminate the rope, so my BW TB's are nominally 7mm, I'm using M5, 5 x 1.5 = 7.5mm Dia so I am right at the lower end, you would not want to go smaller.
b) 50:1 splice length, so M5 DM20 should have 5 x 50 = 250mm bury (M4 = 200mm, M6 = 300mm and so on)
c) Taper the last 1/3 fully so
i) 250 / 3 = 83mm
ii) And you go from full "body" to 1 strand in a linear taper over that 83mm
ipso-facto 166mm of full body is fully buried. &
iii) do the in and out splice prior to burying the splice.

Yellow rope is there to show off the in-out.

Then WRT my shrouds, I sort of coming up with this protocol were I am exerting 3 x expected operating load to "season" the rope.
Therefor WRT my Primary Shrouds, M5 DM20, I plan to take them to 3 x 670kgs or 2 tonne and hold that for an hour.
My Forestay which is M6 DM20, very similar load, and that is because I am expecting a similar operating load on my F/Stay as my Primaries. My D2's (M4 DM20) a bit less, probably 1.5tonne which is what I did the other day.

Let me know if that all makes sense.



Overlord of Anarchy
San Diego
The "Brummel" (in & out) has been shown to NOT add any strength, & may reduce strength. I don't know of any major Dyneema spinner that recommends a brummel. To my knowledge all require 'lock stitching' to secure the bury when it is unloaded

There is a long thread around here with actual testing results by Estarzinger

Regarding the attachment to the t/b eye - the highest loading will be on the first turn around the eye. More 'wraps' around the 'tail' will not relieve/reduce that load. So the 'fancy' hitches will just be harder to undo. Could be used if the dyneema is just a bit too long for the t/b, tho.

Really appreciate your ongoing updates.


Super Anarchist
Sydney mostly
The "Brummel" (in & out) has been shown to NOT add any strength, & may reduce strength. I don't know of any major Dyneema spinner that recommends a brummel. To my knowledge all require 'lock stitching' to secure the bury when it is unloaded

There is a long thread around here with actual testing results by Estarzinger

Regarding the attachment to the t/b eye - the highest loading will be on the first turn around the eye. More 'wraps' around the 'tail' will not relieve/reduce that load. So the 'fancy' hitches will just be harder to undo. Could be used if the dyneema is just a bit too long for the t/b, tho.

Really appreciate your ongoing updates.
Longy, I'm not using the Brummel to gain strength, and I would think it would compromise the strength but it's on the 1/2 load side of the splice, so it's still probably 180% the strength of the "virgin" rope. When I use the Brummel, I never have a slip and I am yet to have a break.
I do use a "locking stitch" when reducing say the spin halyard from 6mm to 4mm, so yes that works, but I have not used it WRT standing rigging, and unless someone convinces me otherwise, I will keep using the Brummel.

I know we are saying the same thing, just want to be clear, and again, I don't profess to be a professional rigger. I am sure they would try and sell me some thimbles and use "Fancy" knots.
I have also been told about the use of super glue, especially in soft shackles, bees-wax to increase the friction, yad yad yad.

I will stick to my Brummel and 50:1.


Overlord of Anarchy
San Diego
Sorry, I was unclear. Too my understanding, when the brummel gets loaded & the opposing pass throughs pull up against each other, that intersection then holds all the load. The buried taper remains unloaded as there is no transfer of load past the locked together brummel. So now you have two point loaded spots with disturbed weave.
However, since line sizing is usually spec'd for stretch rather than strength in shrouds, the possible loss of strength is not an issue.
Due to the number of variations of splicing techniques/actual finished splices there does not seem to be any definitive statement on this

Christo Mroz

New member
I'm thinking about 89er winglets. Could a winglet help other hulls? Those that are narrow, and could use extra bodies upwind, but you have to toss them overboard off the wind.