Dyneema brands, standing rigging, UV and chafe

[wingssail]

Originally Posted by earthbm

in the interest of science I made 5 quick soft shackles out of 3/16 Amsteel Blue, and coated them with two competing truck bed liners, two competing rubberized underside coatings, and a “UV-protected” textile paint. When they will dry I will hang them in So Cal sun for 6 weeks (my timeline before making a decision). Let’s see what happens. All look like paint (thin coats) rather than an external skin like TrueKote. The underside coatings the thickest. Attachment 253085Attachment 253086

Still think TrueKote would make my dyneema shrouds’ life longer than mine…

Six weeks won't tell you much, what they look like after two years is more significant.

[Benz]

Originally Posted by seandepagnier

It just so happens I have access to a machine shop with a metal lathe, and a metal bandsaw as well as being surrounded by free scraps and a good deal of free time Even still it may not be worth the effort... I was curious if people made these for any tips.

Sorry.. my other friend has a metal lathe on his boat as well as lots of scrap metal... I've seen boats with drill presses, even washing machines! Of course even smaller boats often have 3d printers these days, though I limit myself to only one. Thought it was not that rare considering some people have scuba compressors, dish washers and tig welders on their boats.

All that being available, then you can make rings that fit your exact parameters. You could make a super-thick-walled one and never worry about deforming. And you could make your own mast-attachment tangs and really start to save money.

[seandepagnier]

The idea is to use double chain plates and put an annodized aluminum piece between them for the lashings to go around. This piece spun on a lathe to carve it slightly hourglass to keep the lashings from the edge. Not sure if it's viable to carve grooves for each lashing?


I am trying to do something similar for mast attachments. This is similar to "cheeky tangs" but not sure exactly how to make. Should I just make an aluminum piece that fits inside a stainless thimble (at an angle) and bolt through the mast. titanium/monel threaded rod is a bit expensive I may just use hardened stainless 316 (100ksi vs 70ksi) for the bolt, is this reasonable?

mcmaster offers both regular 316 and hardened 316. I am wondering if anyone has an opinion on these here. I feel less concerned with corrosion higher on the mast as there is far less salt up there.

[Benz]

Originally Posted by seandepagnier

The idea is to use double chain plates and put an annodized aluminum piece between them for the lashings to go around. This piece spun on a lathe to carve it slightly hourglass to keep the lashings from the edge. Not sure if it's viable to carve grooves for each lashing?


I am trying to do something similar for mast attachments. This is similar to "cheeky tangs" but not sure exactly how to make. Should I just make an aluminum piece that fits inside a stainless thimble (at an angle) and bolt through the mast. titanium/monel threaded rod is a bit expensive I may just use hardened stainless 316 (100ksi vs 70ksi) for the bolt, is this reasonable?

mcmaster offers both regular 316 and hardened 316. I am wondering if anyone has an opinion on these here. I feel less concerned with corrosion higher on the mast as there is far less salt up there.

I'm going to upgrade my mast attachments to something like a modified "bolt hanger" used by climbers. It'll be a slightly bent piece of alu. plate, through bolted to the mast like normal tangs for wire, but with a radiused horizontal slot designed to take a lashing. Should be dead easy to fabricate. Shrouds will end with a spliced eye on a thimble, eye will lash to the tang. Lighter and less bulky than cheeky tangs, and easy to replace a shroud with the mast up.

[seandepagnier]

Originally Posted by Benz

I'm going to upgrade my mast attachments to something like a modified "bolt hanger" used by climbers. It'll be a slightly bent piece of alu. plate, through bolted to the mast like normal tangs for wire, but with a radiused horizontal slot designed to take a lashing. Should be dead easy to fabricate. Shrouds will end with a spliced eye on a thimble, eye will lash to the tang. Lighter and less bulky than cheeky tangs, and easy to replace a shroud with the mast up.

Interesting, but I don't understand exactly. I will never rely on aluminum in tension, as it work hardens from repeated stress and fails. I have no issues using it in compression (or even other less optimal metals like 304)

[Jim Cate]

Originally Posted by seandepagnier

Interesting, but I don't understand exactly. I will never rely on aluminum in tension, as it work hardens from repeated stress and fails. I have no issues using it in compression (or even other less optimal metals like 304)

Alloy hulled yachts usually have aluminium chain plates... structures in tension.. and they seem to work well. And wings seldom fall off of airplanes, either.

I think maybe this fear is poorly grounded, Sean.

Jim

[Benz]

Originally Posted by seandepagnier

Interesting, but I don't understand exactly. I will never rely on aluminum in tension, as it work hardens from repeated stress and fails. I have no issues using it in compression (or even other less optimal metals like 304)

Look at the aluminum rigging plates used by rope access and rescue folk--they're loaded/released all the time, as are their carabiners. I've never heard of a carabiner failing due to work hardening. It's not like they're being beat on with hammers.
Do you suppose all the aluminum airplanes are made of is only in compression?
I think you're fearing the wrong thing.

[Jim Cate]

Originally Posted by Benz

Look at the aluminum rigging plates used by rope access and rescue folk--they're loaded/released all the time, as are their carabiners. I've never heard of a carabiner failing due to work hardening. It's not like they're being beat on with hammers.
Do you suppose all the aluminum airplanes are made of is only in compression?
I think you're fearing the wrong thing.

I think that we are on the same page, Ben!

Jim

[seandepagnier]

The analogy to airplane wings is more like making a mast or boat out of aluminum . The carabiner also has much more freedom of movement to avoid fatigue.

OK, I admit it can work. Sorry. It just seems like it might not really save much weight. Otherwise, why not use aluminum shackles and aluminum chain on anchors? Why don't all boats just use aluminum chainplates if it's so much lighter and cheaper (and way easier to work with)

He is talking about bending aluminum plate (already weakening it?) then using it in a location almost every other boat uses stainless steel to do the same task: the mast tang. By the time the tang is sufficiently large to ensure it is reliable here, would there be any weight savings? What about windage? My searches indicate aluminum is much more vulnerable to fatigue and generally a poor choice for such applications.

Is this airplane made completely out of aluminum or does it have some stainless or other metals? My searches indicate on aircraft that rivets for example are steel not aluminum.

Finally... what use are lashings on the mast where you can't adjust them?

[Benz]

Originally Posted by seandepagnier

The analogy to airplane wings is more like making a mast or boat out of aluminum . The carabiner also has much more freedom of movement to avoid fatigue.

OK, I admit it can work. Sorry. It just seems like it might not really save much weight. Otherwise, why not use aluminum shackles and aluminum chain on anchors? Why don't all boats just use aluminum chainplates if it's so much lighter and cheaper (and way easier to work with)

He is talking about bending aluminum plate (already weakening it?) then using it in a location almost every other boat uses stainless steel to do the same task: the mast tang. By the time the tang is sufficiently large to ensure it is reliable here, would there be any weight savings? What about windage? My searches indicate aluminum is much more vulnerable to fatigue and generally a poor choice for such applications.

Is this airplane made completely out of aluminum or does it have some stainless or other metals? My searches indicate on aircraft that rivets for example are steel not aluminum.

Finally... what use are lashings on the mast where you can't adjust them?

You could use aluminum shackles and chain on anchors, I guess--many anchors are made from aluminum, but steel chain is cheap and usually weight is desired. But the reason I'm making mast tangs from Alu. is that to get a nice radius for lashing, you need thick material, and SS that thick would be super-heavy. I'd love to use Ti, but the cost prohibits.
A schooner I work on has welded-on aluminum tangs for the shrouds to attach to. They're in tension--huge tension, as the schooner gets sailed hard every day for half the year, and they're still working perfectly.
Finally, the lashing is just a convenient way to attach the top of the shroud to the mast--it's not for adjustment, which is done with a deadeye down low. But if something should go wrong, you could go aloft and change out the shroud pretty easily without any tools but a knife or fid.

[seandepagnier]

This is really interesting.. the more details we discuss the more I realize there are more possibilities and my understanding less than I thought before. Thanks for that!

On this schooner, the tangs are just welded to the mast? How are their dimensions compared to standard stainless tangs? Are they 2x? 3x? I've had aluminum bicycles and had the frames break after riding a few thousand miles (admittedly I was riding a road bike offroad and put it through hell) but my steel frame bike is a few years older than I am and still ok. This is not a scientific or controlled experiment unfortunately.. but I recall hiking the AT, that other hikers complained the aluminum treking poles would break after 1000 miles or so, the carbon fiber ones would splinter, and the titanium ones would last for the whole trail (or several perhaps) but cost too much. I was in the 10% of hikers who didn't use poles.

As for aluminum shackles and chain... There is a reason they make aluminum anchors, it is to save weight. I guess you could argue that aluminum chain would be undesirable because the point of the chain is for cantenary and you would be better off with rode to save weight. It seems chain has the other desirable property of not chaffing through, so an aluminum chain would be useful, however I think aluminum would wear out much faster? For using lashings as you suggest to a tang this is at least not an issue as there is no metal wearing against it, so this may explain why aluminum is not considered for chainplates/tangs when it could be if you are using lashings.

People with fortress anchors might find aluminum chains useful as once the zinc wears off the galvanizing of the chain/shackle, the steel will be on the wrong side of aluminum on the galvanic table. Again, not sure about aluminum wearing out here, I suspect it is a real issue, but there are also a lot of aluminum alloys to choose from.

As for aluminum shackles.. again these would be really useful if they work as you suggest, but I have never seen one and wonder about wear and suspect this makes them not viable. Stainless shackles are incredibly expensive to buy, its $50-$60 for a 3/8" one now, and galvanized ones rust if not protected and are still heavy. The other issue is they would be useful basically for all-aluminum engineered systems as the physical sizes would be much larger for everything.

It is a good point about carabiner, but these hold the weight of a human falling on a nylon rope (which stretches) vs a stay which does not stretch (much), so the forces are very different and the amount of aluminum for a tang or chain plate would have to be much more to avoid any deformation.

Assuming the tang would work well with the lashings, wouldn't it be just as easy to put a titanium (or stainless) threaded rod through the mast and just put a thimble on the end of the stay to this and avoid the lashings and tang all together? This is my intention, so I am not sure what you gain from adding a specialized tang you have to fabricate and lashings, just not having to undo a locknut.

[Benz]

Originally Posted by seandepagnier

This is really interesting.. the more details we discuss the more I realize there are more possibilities and my understanding less than I thought before. Thanks for that!

On this schooner, the tangs are just welded to the mast? How are their dimensions compared to standard stainless tangs? Are they 2x? 3x? I've had aluminum bicycles and had the frames break after riding a few thousand miles (admittedly I was riding a road bike offroad and put it through hell) but my steel frame bike is a few years older than I am and still ok. This is not a scientific or controlled experiment unfortunately.. but I recall hiking the AT, that other hikers complained the aluminum treking poles would break after 1000 miles or so, the carbon fiber ones would splinter, and the titanium ones would last for the whole trail (or several perhaps) but cost too much. I was in the 10% of hikers who didn't use poles.

As for aluminum shackles and chain... There is a reason they make aluminum anchors, it is to save weight. I guess you could argue that aluminum chain would be undesirable because the point of the chain is for cantenary and you would be better off with rode to save weight. It seems chain has the other desirable property of not chaffing through, so an aluminum chain would be useful, however I think aluminum would wear out much faster? For using lashings as you suggest to a tang this is at least not an issue as there is no metal wearing against it, so this may explain why aluminum is not considered for chainplates/tangs when it could be if you are using lashings.

People with fortress anchors might find aluminum chains useful as once the zinc wears off the galvanizing of the chain/shackle, the steel will be on the wrong side of aluminum on the galvanic table. Again, not sure about aluminum wearing out here, I suspect it is a real issue, but there are also a lot of aluminum alloys to choose from.

As for aluminum shackles.. again these would be really useful if they work as you suggest, but I have never seen one and wonder about wear and suspect this makes them not viable. Stainless shackles are incredibly expensive to buy, its $50-$60 for a 3/8" one now, and galvanized ones rust if not protected and are still heavy. The other issue is they would be useful basically for all-aluminum engineered systems as the physical sizes would be much larger for everything.

It is a good point about carabiner, but these hold the weight of a human falling on a nylon rope (which stretches) vs a stay which does not stretch (much), so the forces are very different and the amount of aluminum for a tang or chain plate would have to be much more to avoid any deformation.

Assuming the tang would work well with the lashings, wouldn't it be just as easy to put a titanium (or stainless) threaded rod through the mast and just put a thimble on the end of the stay to this and avoid the lashings and tang all together? This is my intention, so I am not sure what you gain from adding a specialized tang you have to fabricate and lashings, just not having to undo a locknut.

I think you've reached the stage of designing things where your brain is so full you're over-engineering everything, and chasing every idea down the farthest rabbit trail it can go. I've been there, several times, while building my own boat. Our fellow member Chotu has as well.....
Anyhow, the tangs on the schooner are welded, they're a piece of 3/4" bar stock placed vertically along the mast, with a hole for a pin drilled through, so the shroud ends with a jaw. I can't tell if the bar goes through the mast to become the tang on the other side--that's how I'd do it if I were engineering the mast. It would be relatively simple to cut a rectangular slot on either side of the mast to slip the bar through, then weld it in. I made my own mast similarly, but instead of welding, which I had no access to, I milled slots into the bottom of the plate which key into the wall of the mast section. I'd do it the same way next time, but with better provision for lashings, which I hadn't imagined yet (soft rigging has come a long way since then).
Still, the "bolt hangers" I'm making are for those places where a transverse bar won't do, and before I simply had pieces of rod sticking out that served as bolsters for a soft eye that went around the whole mast.
Your plan of putting a thimble over a piece of rod and having it all sit against a locknut gives me the willies: unless the thimble fits loosely, it won't articulate, but if it sits loosely, it'll point-load and possibly deform. Your bolt won't be in compression, like a snug tang-bolt: it'll be levering about in shear. Won't the rattle of the loose loo'ard shrouds disturb, as the thimbles clack on the rod? Or am I not seeing what your plan is?

[earthbm]

Thanks for the thread hijack guys…

[seandepagnier]

Originally Posted by Benz

Your plan of putting a thimble over a piece of rod and having it all sit against a locknut gives me the willies: unless the thimble fits loosely, it won't articulate, but if it sits loosely, it'll point-load and possibly deform. Your bolt won't be in compression, like a snug tang-bolt: it'll be levering about in shear. Won't the rattle of the loose loo'ard shrouds disturb, as the thimbles clack on the rod? Or am I not seeing what your plan is?

I intend to fill the gap with aluminum. So an aluminum piece fits over the rod, and the thimble over this. It doesn't need to articulate, since the dyneema itself is flexible?

There will be an end plate or large washer to prevent the thimble falling off. As for the loose shrouds. I will have to ensure everything is a snug fit, essentially the same as a "cheeky tang" though rather than a single piece of aluminum, it will be a few pieces and a thimble. If you have any better ideas let me know.

The other way would be to just use a tang bolted on, which I'm not really opposed to, and still pondering.. the annoying part is attaching the thimble to this tang. It requires a shackle? Or would you use double tangs and a pin?

[fxykty]

Originally Posted by seandepagnier

I intend to fill the gap with aluminum. So an aluminum piece fits over the rod, and the thimble over this. It doesn't need to articulate, since the dyneema itself is flexible?



There will be an end plate or large washer to prevent the thimble falling off. As for the loose shrouds. I will have to ensure everything is a snug fit, essentially the same as a "cheeky tang" though rather than a single piece of aluminum, it will be a few pieces and a thimble. If you have any better ideas let me know.



The other way would be to just use a tang bolted on, which I'm not really opposed to, and still pondering.. the annoying part is attaching the thimble to this tang. It requires a shackle? Or would you use double tangs and a pin?

You could use a double tang and pin through the narrow end hole of the thimble - if your existing SS rigging has the tangs already. Otherwise you can make them up, or get a rigger to make them up. My preference is always for least number of components, hence why we did spend the money for Cheeky Tangs.

Do make sure that the final thimble with the shroud eye is aligned. As you mentioned it does not need to articulate. In our case our Cheeky Tangs don’t articulate.

Do note that even with a reasonably tight rig (and ours is) the leeward shroud will go loose at times (think pumping due to waves and the times you keep more sail up then really needed), so do mechanically secure the eye to the thimble. We do that with a secondary tang over the Cheeky Tang that has its own through bolt. Though that makes it more of a pain to replace the rig.