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Old 02-08-2012, 01:48   #16
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re: Aluminium Chainplates

Yes the chainplates need to a marine grade aluminium.
They should be the same material as the hull. 5083 and 5086 are the best materials.

Please don't take any advice from someone who does not understand aluminium yacht construction.
The thought of useing bronze chainplates on an aluminium hull is just too horrible to contemplate.
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Old 02-08-2012, 06:57   #17
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re: Aluminium Chainplates

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Originally Posted by DeepFrz View Post
There is a metal that is aluminum on one side and steel on the other. They are explosively fused. It is used to join aluminum and steel, so you could use it to attach a steel chain plate or a steel loop on the toe rail for the rigging. I can't remember what it is called though.
Explosive welding, also known as explosive bonding or explosive cladding, is sold under the trade names of “Detaclad”, “Triplate”, etc.
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Old 02-08-2012, 07:54   #18
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re: Aluminium Chainplates

My boat has what appears to be an aluminum alloy used for the shroud chain plates.
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Old 03-08-2012, 20:23   #19
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re: Aluminium Chainplates

I had a Peterson 34 (fg) with aluminum chainplates. They held up for 20+ years of racing. At one point there was some deformation at the top of the holes where the rigging pins were located. I had a friend who is a structural engineer look at them and he said they were ok as long as there was not indication of the edge of the plate above the holes was not deforming. In your situation I would be confident of using aluminum. Leave as much margin above the holes as possible, and use the largest rigging pin diameter practical to have ensure the largest bearing area for stress. Check every few years or whenever the rig is out. Replace when it looks like things are getting weak. You should be good for many years.
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Old 03-08-2012, 20:28   #20
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re: Aluminium Chainplates

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Friends don't let friends have aluminum chainplates. Is it possible? Doesn't seem so.

Sounds as sensible as aluminium rudder tubes.
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Old 06-08-2012, 02:55   #21
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re: Aluminium Chainplates

Thanks everybody for the great comments and suggestions.

The forward bulkhead will be directly under the main mast so I'll extend the necessary part of it above the deck (saving me one weld), then weld extra plate on either side. I haven't done a proper calculation yet, but I think from the comments above I'll be able to achieve a suitable thickness and width. I'll use the same material as the hull even if it ends up needing to be thicker/wider. My side decks are quite wide so having the chainplate across the boat is acceptable.

As to the bush (or not), I'm still inclined to use a bush from the suspension of a car. I'm thinking of something called Nolathane (that's the brand in australia anyway). If one of these can last 100000km in a car, then I would think it would be ok. They can't distort too much or it would stuff up the steering geometry of the vehicle and they also claim to be UV resistant. The large outside diameter would put less of load on the material around the eye and they have a metal inner bush which I could replace with stainless easily enough.
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Old 06-08-2012, 03:13   #22
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re: Aluminium Chainplates

Nick

If you're going to go that way, you can also buy the same material (urethane elastomer) in tube form in a whole range of sizes, eg "Lurethane" from J C Ludowici & Son, NSW.

You'd want to specify 90 durometer rather than the usual 70 (which is probably a bit too soft)

Seeing you only want a few, I can see it's easier to go your way, though... even if it means drilling out the inner sleeve.

Personally I would favour a suitable grade of Tufnol or Micarta, because they're much stronger in compression, but urethane would be fine for a boat your size
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Old 06-08-2012, 05:24   #23
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re: Aluminium Chainplates

I think you will find this blog a big help.

It deals with the design and construction of chain plates on an aluminium boat. Lots of other good information detailing the total building process.

Building Odyssey
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Old 06-08-2012, 23:06   #24
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re: Aluminium Chainplates

Hello all, As Noelex77 has mentioned, you really need to do your own research. Getting such vital information from this thread of mis-information could lead to serious consequences. I am building a 55' alloy cutter that has a righting moment at 30 degrees of 105,000 lbs. Skene's Elements of design formula directs me to install chain plates that are 1 1/8 inch thick with 1 inch pins. These are the same alloy as the hull,(5086)The distance of the outside of the hole to the top of the plate is very important as well as the radius of the top edges. Remember that when putting in a bushing, it needs to be able to take the force of your whole boats displacement in compression. ie,RM@30degrees. I doubt if something squeezed out of a tube will do that.
cheers,Greg
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Old 07-08-2012, 01:37   #25
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Re: Aluminium Chainplates

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Originally Posted by Mirar View Post
Hello all, As Noelex77 has mentioned, you really need to do your own research. Getting such vital information from this thread of mis-information could lead to serious consequences. I am building a 55' alloy cutter that has a righting moment at 30 degrees of 105,000 lbs. Skene's Elements of design formula directs me to install chain plates that are 1 1/8 inch thick with 1 inch pins. These are the same alloy as the hull,(5086)The distance of the outside of the hole to the top of the plate is very important as well as the radius of the top edges. Remember that when putting in a bushing, it needs to be able to take the force of your whole boats displacement in compression. ie,RM@30degrees. I doubt if something squeezed out of a tube will do that.
cheers,Greg
G'Day Greg,

Good advice! I can't believe that someone would actually design their chainplates from info garnered here on these hallowed (but often erroneous) pages. And to say that one must not use aluminium for chainplate structures... good grief!

Anyway, how is progress on the new boat?

Cheers,

Jim
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Old 07-08-2012, 05:45   #26
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Re: Aluminium Chainplates







Snowpetrel Sailing: Fatigue... of the metal variety

Make em strong! the problem can be getting the toggles on the turnbuckles over thicker chainplates. One boat I sailed got around this by using custom stainless link plates from the very thick chainplates to the turnbuckles.
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Old 11-08-2012, 00:04   #27
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Re: Aluminium Chainplates

I'll agree to that 100%, design by popularity contest would not be very useful..... but ..... it is also important to see what is actually out there, garner wisdom from others etc. I've known and worked with engineers who are very good at theory, but completely impractical. One guy even told me that he bought the highest quality hydraulic jack so that he wouldn't need to mess around with axle stands.... hmm... I guess I would trust my life to a tiny little valve ... not.
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Old 11-08-2012, 00:23   #28
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Re: Aluminium Chainplates

I must be missing something, but wouldn't you need to include the dimensions of the rig to calculate the chainplate size (as well as possibly the righting moment). If I had a 1 metre mast attached to your boat with a 1 square meter sail (sounds like a solar panel and plenty of those come loose) then I wouldn't need a 1 1/8 thick chain plate (would need to know the width as well of course).

So if I assume that the boat was glued to a perfectly flat ocean, with certain sail area and dimension, then applied a wind of certain speed, I could calculate the force on my chainplates. Of course real life is different, boats give ( at least monohulls do) so this might actually reduce the load, but then repeated cycles will cause fatigue which increases the required dimensions. Does anyone have a load cell and data logger running on their boat, it would be intriguing to say the least.

As to the bushing, a suspension bush from a light truck would take my ~4 tonnes displacement and then wack it around several times a second for say 150000 km ( say about 10 million times) and still be servicable. The thing is that I would want it to have some slight give (I presume this is the same in cars) as it will spring back but the aluminium wouldn't.
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Old 11-08-2012, 00:26   #29
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Re: Aluminium Chainplates

Thanks, I had a quick look and that is one site that I will be going through thoroughly when I get a moment. Nice workshop they have.
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