DIY Mast tangs for Dyneema shrouds, Synthetic standing rigging Episode 6

[@clickireland1113]

Brilliant Andy thanks. Exactly my problem (and loads of looking-up google) - Solved. Really appreciate your sharing of the solutions you found thank you. Small rigging I'm doing to a Pirate 17 that had the stainless steel shrouds fail while moored in harbour. Mind you the rigging was probably origional and 30 years old. Going dyneema obviously now. Rooster in the UK seem to have the best supplies I can research so far.

[@SustainableSailing]

I'll check Rooster, we've mostly used Jimmy Green Marine so far.

[@CheersWarren]

The only reason for using the FR4 I can see it is that this already has a smooth surface on it and you can cut it. Why not just use a ready made solid round thimble ( smooth for dyneema ) and add a wedges inboard and out. Use SS I-beam wedge washers as they have about the right angle. Thimbles made typically from aluminium with anodized coating. Cost a problem I assume? Then use a hollow SS round thimble with a pressed and glued in plug you can drill at the 15 deg. Angle . This is very similiar to traditional rigging but they normally put the loop around the mast above the gaff mainsail throat. Warren

[@SustainableSailing]

Hi Warren, In large part our choices are based on what we can find or think to look for :-) By Solid Round Thimble do you mean what is commonly sold as a low friction ring (similar to what we are using for the lower end of the shrouds eg jimmygreen.com/low-friction-rings/77358-8854-barton-low-friction-rings#/6795-internal_diameter-28mm )? I didn't choose these for 3 reasons. a) they are never shown with a bolt through the centre hole, only with rope so I assume they are not suited for the task (and as the hole is not exact for the bolt size there will be a point loading/wear). b) I have only seen them in aluminium or titanium and surely this would cause a galvanic reaction with the stainless bolt? c) if using wedges (which I didn't know existed, that is helpful thanks) there would be no articulation, the angle would be fixed, yet the angles of our shrouds are not all identical ranging from approx 11 to 13+ degrees? So the dyneema won't be perfectly aligned. With our length of rod there is space for the dyneema to align exactly. With the pressed & glued plug it seems to me that is less easy as a diy solution as it requires a more complex part (press-in plug) to make and then to drill at the correct angle? But I might not have understood correctly :-)

[@svoiysh]

Nice ! Making flush surface for head of the screw and nut I thing is important. No pointy contacts, big surface of contact will reduce friction wear of fr4. Maybe even washers. Also backing plates that were riveted to the mast where the bolt was going through the mast ware reinforcing contact point between mast and bolt. Aluminium is soft compering to stainless. You might want to use a bolt without thread on all contact places with fr4. Thread will be like saw vs fiberglass. I wood also use fr4 next to mast without washer. Smaller leverage on bolt only shear force. All anchoring point on boats with synthetic chain plates have pin/shaft as a contact point. So are you sure that dyneema will not cut through fr4? I'm not an expert it's just gut feeling.

[@SustainableSailing]

Thanks! The mizzen lower, just below the spreaders is the only shroud attachment point without a plate riveted to the mast. It does have a compression tube though. Agree, the forstner bit is doing a nice job or creating a flat space for the bolt head. Agree on needing a bolt with no thread touching the FR4. Next video shows a Mark II with these changes and the endplates glued on. Beyond that we are planing a Mark III made from a single piece of "Acetal C", should resist wear better. As for the pin, there was a video from Zingaro about Kraken fittings because the Pin into a thimble with a size mismatch causes point loading which we are trying to avoid. The combination of a tightly fitting bolt and a 60mm diameter rod for the dyneema look should avoid point loadings.

[@markthomasson5077]

Is FR4 pulltruded? If so all the glass is going the wrong way. Another way of making a similar item is to mould epoxy with chopped strands. See Easy Composites videos. They use carbon, comes out stronger than aluminium. They make the mould using a 3D printer. All said is your solution a bit complicated? How about, a stainless sleeve, width of the rope, with a large flat cone shaped nylon washer each side?

[@SustainableSailing]

In a later video you will see that based on a number of conversations we switched from FR4 for the tangs to Acetal-C. We were able to machine them with our table router. We don't have a 3d printer and this felt like easier tech. We wanted the diameter to be large enough for the recommended dyneema bend radius (5x diameter) and don't have the tools to machine stainless steel. Plus this way we can angle the surface to match the angle of the shrouds.

[@jampasritalon4180]

Make the next one thicker and use a large bit to counter bore a hole big enough for the bolt head and washer (and socket). Bore the large hole first (with a forsner bit to create a flat bottom) then the 13mm hole for the bolt. I would use a numbered bit set to make a very close fit to the shank on the bolt. You need to avoid all sources of stress risers on fiberglass structures (air craft mechanic experience). It will also look better than using an angled washer. I agree you bored the hole too close to the edge. Aim closer to the center next time. Size your bolt so no threads contact the fiberglass.

[@SustainableSailing]

Thanks. a) I have wondered about fitting a stainless steel sleeve through the FR4 so the bolt is inside the sleeve. I could epoxy the sleeve into the FR4 to help even the load distribution? This would also ensure no issue with bolt threads. b) not sure what you mean by a numbered bit set? I used a 13mm drill for a 13mm bolt. c) agree on the width and hole position. I'll put a jig on the pillar drill to get position spot on. d) looking for forsner bits now. e) thinking about it. I'm going to put FR4 endplates on both inside and outside to keep shroud from slipping into inner washer. Much appreciated.

[@jampasritalon4180]

@@SustainableSailing they make numbered drill bits 1 through 60 and lettered bits A through Z. These sizes are neither SAE nor metric. The in between sizes allow you to choose a bit that is very nearly perfect to avoid point loading. Proper sized holes should obviate the need for a sleeve. Avoid threads in any case! There is a reason why it is very nearly a death penalty offence to put loads on threads on an aircraft. We would rather go one size up in length and let washers make up the difference. Planning on your part would let you drill the perfect depth with the forsner bit to avoid too many washers or loading threads. Your sleeve idea protects the fiberglass but still loads the threads.

[@SustainableSailing]

Wow, thanks. That is a whole load of useful information that I didn't know. I'm planning my Mark II, to put this learning into practice 😊

[@CheersWarren]

@@SustainableSailing , forstner bits dull very fast on grp. A proper flat bottom bolt counterbore with a pilot the size of the thru hole you drill first will work better BUT won’t this mess up the anti slip off washer your are going to add?

[@SustainableSailing]

I'm learning lots of new stuff. I hadn't heard of a flat bottom bolt counterbore before. However, I've looked and there seem to be 2 problems. a) The width of the counterbore seems to be just enough for a bolt with a socket head, rather than a normal bolt head or nut. Eg for my M13 bolt on the mizzen I need a 31mm counterbore to fit a socket wrench over the bolt & nut. b) I'm struggling to find them large enough anyway. The mizzen is M13 but the main mast will be M16. I found more examples called "Counterbore Mill Bit" I guess another option would be to use a lathe but I don't have one (or know how to use one), I certainly won't have one when out sailing. Regarding the end plates. Yes the counterbore will affect these. I will try with the end plate epoxied on before drilling. The washer in the counterbore will still grip some of the end plate where it is shallower at the top. I could also experiment with a thicker end plate so that the it is thicker than the counterbore is deep. More to think about and experiments to do.

[@AndyUK-Corrival]

you could have made tang bigger and recessed the bolt head, and, had the face of the bolt flush in the tang. personally I would not be happy with the bolts as they are.

[@SustainableSailing]

I agree about recessing the bolt head (and the nut). I'll get the end plates on and I will need to order a suitable drill bit as I only have flat bits of a suitable size and I don't think they will work on FR4. I also agree that I was a bit stingy with the tang length. Mostly I was worried about the gap to the shroud but that has ended up more spacious than I feared.

[@XXLaffinGravyXX]

Nice vid fella..looking forward to the full rig setup.....but on a side note ..Rigging Doctor..God the intro to their vids of her shrieking out of tune singing... god its like two cats fighting a sack...thats why i refuse to watch any of their stuff ...and he acts like a kid with his baby talk ..ffs its embarrassing..but their yanks so they dont know any different.

[@SustainableSailing]

Thanks, no baby talk from me - I'd get all embarrassed 😂