Love the openness of new ideas and thought processes to the design. I suspect there's gonna be plenty of head scratching to come, with loads of advice and ideas in the comments. I really hope this works out as it will help so many others out here as a DIY alternative to getting our eyes taken out by rigging companies.
I will call the FAA and recommend an honourary A&P certificate for your efforts to adhere to aircraft specs! Congrats on the success with the bits. I have used FR4 in experimental aircraft and predict you will not have problems with cracking now. Consider epoxy paint as the resin will degrade with UV exposure. You could match your mast if you want. I would be tempted to make 4 perfect discs as your cheeks (although I wonder if you need to worry about the stay moving toward the mast and you might eliminate those.) and I would fabricate them and sand them before epoxying onto the tang. Then I would off-set the disks so they were eccentrically located to miss your spreaders. I believe you are using 2mm for cheeks. I leave it to your judgment but 3 or 4 would make me more secure. I would also use a fillet of thickened epoxy at the tang-cheek junction for many obvious reasons. Good work friend!
Hey, really enjoying your project here. One issue I think you should reconsider is the attachment of shrouds to the mast. The original tangs attached very close to the mast such that the bolt was mainly in so gle shear. This new design has a decent leverage arm on that bolt. I suspect you're at risk of fatigue failures over time on this one. I have training in this stuff so take it for what you paid...I'd stick with traditional tangs on the mast to connect up shrouds. Good stuff!
First thanks, glad you are enjoying the project. We have thought about the issue of the leverage on the through mast bolt. Jane trained as a Civil Engineer so does do some check calculations for us, she does get irritated with my sloppy language about loads and forces so I hope she isn't checking the comments ;-) Our first response is that we are not moving the load any further out than if we bought Colligo Marine cheeky tangs which we find reassuring. The plates on the original tangs would not spread wide enough for a dyneema shroud with thimble (the original fittings were a flattened swage eye which was only 5 or 6mm thick). Also if we used a stainless steel thimble onto a pin we would be getting a point loading. Either a much larger pin is needed or a hard to find thimble with solid interior. Remember that we are not tuning for a racing rig and that the Rival 38 has a fairly small rig. My understanding (which may well get me in trouble and be wrong) is that as the tang fits tightly onto the unthreaded bolt the load is not a point at the middle of the shroud but the tang is going to exert the leverage close to the mast. Also as the tang is wide at the mast and tightly fitted to the mast the thickness of the tag below the bolt will also be helpful. If I am wrong I hope that at least we will make a hugely popular video titled "We told Dave he was wrong" in which we capture the mast falling down ;-)
Ha, here's hoping you don't make that mast falling video! Glad someone checked it. Cool project that I'm enjoying watching. Boat design is typically very conservative with rigging in particular so this stuff is always welcome.
if the fr4 is unidirectional along its length then this would be a very weak part you are building. i would suggest a winded part. then again force is mainly compression on it above the screw. if you connect dyneema below srew it would be tensile on the fibres.
Nothing I've seen suggests that the FR4 is unidirectional. The two key disadvantages people have pointed out are a) the wear resistance isn't very high (but our loads are quite static) and b) it is not very easy to machine. As the dyneema goes over the FR4 and the bolt goes through it I think all the load is compression, isn't it?
I have only seen extruded (poltruded?!?) Rods. In these the fibres are along its length. If you slice them obviously only the resin is holding them together. Tensile strenght is were carbon et cetera is shining. For the cheeky tangs, my plan so far is to use aluminium halyard rolls between bigger washers or carbon endplates. The plates will be angled like yours to fit the mast and screw. ✌
This is the rod I've been using www.aiplastics.com/epoxy_4w_ep_rod.html Good to hear someone else making dyneema tangs. Do your aluminium halyard rolls come pre-drilled? If so how are you going to get them to sit at the correct angle? Also how will you avoid galvanic corrosion between them and the bolt?
Nice to talk to someone doing a heath robinson, too. The plates you are using to hold the dyneema sideways would be angles/profiled to fit mast and screw. Another option is to use carbon rowing to make a cheeky tang diy. And further I am suggesting to make something like a chainplate that is also from rowing. Which uses tensile strenght of the fibres. Like a 8 plate, screwed in on top and bottom hole takes the dyneema. I have lots of rowing and the solution to any problem is to use epoxy with rowing ofcourse. Definitely following you very closely here..
Have you seen the witch sailor? He has a steel boat with dyneema rigging. He is using a super simple solution on his rail. Basically just puts the dyneema through a home in the rail and the button knots it. I would be reluctant because of chave but lots of other points of failure are eliminated. It would be cool to just do this for the baby stays at the mast. ✌
Much simpler to replace the cotter pins once in a while. I don't get why you're so concerned with having to fix your things at sea when the original stainless tangs/pins are not something you're going to have to worry about for decades if you just replace the original equipment.
Hi, It would be less change but the advantages are much more than being able to fix things at sea (or more accurately diy repairs in remote locations). We believe our latest version is a significant improvement in lots of ways.
I have mentioned Colligo in lots of our videos and on our blog. I've had some helpful comments from them on our blog regarding our dyneema rigging. Very nice people with a huge amount of experience. We just can't afford their cheeky tangs but we highly recommend them for anyone who can.
Patents are to protect IP from other companies selling products based on them... you can build **anything** for yourself and not worry.... just dont sell it.
Love the openness of new ideas and thought processes to the design. I suspect there's gonna be plenty of head scratching to come, with loads of advice and ideas in the comments. I really hope this works out as it will help so many others out here as a DIY alternative to getting our eyes taken out by rigging companies.
Reminds me of some great software teams I was part of on Compuserve in the days before public Internet access 😁 #YesImVeryOld 🤣
I will call the FAA and recommend an honourary A&P certificate for your efforts to adhere to aircraft specs! Congrats on the success with the bits. I have used FR4 in experimental aircraft and predict you will not have problems with cracking now. Consider epoxy paint as the resin will degrade with UV exposure. You could match your mast if you want. I would be tempted to make 4 perfect discs as your cheeks (although I wonder if you need to worry about the stay moving toward the mast and you might eliminate those.) and I would fabricate them and sand them before epoxying onto the tang. Then I would off-set the disks so they were eccentrically located to miss your spreaders. I believe you are using 2mm for cheeks. I leave it to your judgment but 3 or 4 would make me more secure. I would also use a fillet of thickened epoxy at the tang-cheek junction for many obvious reasons. Good work friend!
High praise! Thanks. Good tips for final finishing. 🤩
Hey, really enjoying your project here. One issue I think you should reconsider is the attachment of shrouds to the mast. The original tangs attached very close to the mast such that the bolt was mainly in so gle shear. This new design has a decent leverage arm on that bolt. I suspect you're at risk of fatigue failures over time on this one. I have training in this stuff so take it for what you paid...I'd stick with traditional tangs on the mast to connect up shrouds. Good stuff!
First thanks, glad you are enjoying the project.
We have thought about the issue of the leverage on the through mast bolt. Jane trained as a Civil Engineer so does do some check calculations for us, she does get irritated with my sloppy language about loads and forces so I hope she isn't checking the comments ;-)
Our first response is that we are not moving the load any further out than if we bought Colligo Marine cheeky tangs which we find reassuring. The plates on the original tangs would not spread wide enough for a dyneema shroud with thimble (the original fittings were a flattened swage eye which was only 5 or 6mm thick). Also if we used a stainless steel thimble onto a pin we would be getting a point loading. Either a much larger pin is needed or a hard to find thimble with solid interior.
Remember that we are not tuning for a racing rig and that the Rival 38 has a fairly small rig.
My understanding (which may well get me in trouble and be wrong) is that as the tang fits tightly onto the unthreaded bolt the load is not a point at the middle of the shroud but the tang is going to exert the leverage close to the mast. Also as the tang is wide at the mast and tightly fitted to the mast the thickness of the tag below the bolt will also be helpful.
If I am wrong I hope that at least we will make a hugely popular video titled "We told Dave he was wrong" in which we capture the mast falling down ;-)
Ha, here's hoping you don't make that mast falling video! Glad someone checked it. Cool project that I'm enjoying watching. Boat design is typically very conservative with rigging in particular so this stuff is always welcome.
Well we hope we don't make that video as well. The number of 50mph+ storms that come through the Menai Straits in winter will be a first good test.
if the fr4 is unidirectional along its length then this would be a very weak part you are building. i would suggest a winded part. then again force is mainly compression on it above the screw. if you connect dyneema below srew it would be tensile on the fibres.
Nothing I've seen suggests that the FR4 is unidirectional. The two key disadvantages people have pointed out are a) the wear resistance isn't very high (but our loads are quite static) and b) it is not very easy to machine.
As the dyneema goes over the FR4 and the bolt goes through it I think all the load is compression, isn't it?
I have only seen extruded (poltruded?!?) Rods. In these the fibres are along its length. If you slice them obviously only the resin is holding them together.
Tensile strenght is were carbon et cetera is shining.
For the cheeky tangs, my plan so far is to use aluminium halyard rolls between bigger washers or carbon endplates. The plates will be angled like yours to fit the mast and screw. ✌
This is the rod I've been using www.aiplastics.com/epoxy_4w_ep_rod.html
Good to hear someone else making dyneema tangs. Do your aluminium halyard rolls come pre-drilled? If so how are you going to get them to sit at the correct angle? Also how will you avoid galvanic corrosion between them and the bolt?
Nice to talk to someone doing a heath robinson, too. The plates you are using to hold the dyneema sideways would be angles/profiled to fit mast and screw.
Another option is to use carbon rowing to make a cheeky tang diy. And further I am suggesting to make something like a chainplate that is also from rowing. Which uses tensile strenght of the fibres. Like a 8 plate, screwed in on top and bottom hole takes the dyneema.
I have lots of rowing and the solution to any problem is to use epoxy with rowing ofcourse. Definitely following you very closely here..
Have you seen the witch sailor? He has a steel boat with dyneema rigging. He is using a super simple solution on his rail. Basically just puts the dyneema through a home in the rail and the button knots it. I would be reluctant because of chave but lots of other points of failure are eliminated.
It would be cool to just do this for the baby stays at the mast. ✌
Much simpler to replace the cotter pins once in a while. I don't get why you're so concerned with having to fix your things at sea when the original stainless tangs/pins are not something you're going to have to worry about for decades if you just replace the original equipment.
Hi,
It would be less change but the advantages are much more than being able to fix things at sea (or more accurately diy repairs in remote locations).
We believe our latest version is a significant improvement in lots of ways.
Really a company called Colligo has this product for sale for five years nothing new here in fact you might be in breech of patents…..
I have mentioned Colligo in lots of our videos and on our blog. I've had some helpful comments from them on our blog regarding our dyneema rigging. Very nice people with a huge amount of experience.
We just can't afford their cheeky tangs but we highly recommend them for anyone who can.
Patents are to protect IP from other companies selling products based on them... you can build **anything** for yourself and not worry.... just dont sell it.