Chain plate Alignment

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Windcall
Bottom Paint Application Technician
Posts: 22
Joined: Sun Jan 12, 2020 6:19 pm
Boat Name: Windcall
Boat Type: Alberg 30 1969 Hull 397

Chain plate Alignment

Post by Windcall »

In the process of rebuilding my Alberg, I made a pattern of the angle of the chain plates before removing them. Currently and sadly I have lost the patterns I made due to a move and someone thought they were not important.
So now how does one know the proper alignment. I know how to align to the mast but not the angle of the chain plate to the rigging. I am new to this but I am believing the plates need to be in close alignment to the rigging there attached to.
Is there some formula used? Mast height/shroud length.

Any help for this rookie would be appreciated.
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markwesti
Almost a Finish Carpenter
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Joined: Wed Oct 17, 2018 9:29 pm
Boat Name: Patricia A
Boat Type: Westsail 28
Location: Long Beach , Ca.

Re: Chain plate Alignment

Post by markwesti »

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atomvoyager
Moderator | Revitalizer of Classics
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Boat Type: Pearson Triton
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Re: Chain plate Alignment

Post by atomvoyager »

The upper shroud chain plates are vertical. For the lowers, looking at the drawing above you see the spreaders are placed roughly halfway along the mast about 18' above deck. The distance from mast to chain plate is just over 4'. You could calculate the angle with a math formula but the simple way that makes it clear to you is to draw a 4.5-1 triangle say 10" on one side and 2" on the other and lay a protractor over it and you'll get about 79 degrees. If the mast is up and boat sitting level you could lay the protractor against a level and the shroud and read it directly. If the chain plates are adequate size of say 0.25 x 1.5" then a few degrees off is not going to matter and they can even be close to vertical and won't bend or move on this size boat if well secured. You may bump up against the inside of the hull with the lower end of the chain plate anyway before you get all the way to 79 degrees. If so, you either move the deck slot inboard or leave it at that and call it good enough.
Windcall
Bottom Paint Application Technician
Posts: 22
Joined: Sun Jan 12, 2020 6:19 pm
Boat Name: Windcall
Boat Type: Alberg 30 1969 Hull 397

Re: Chain plate Alignment

Post by Windcall »

Thank you Atom ... I believe I got it all sorted now.. thank you for help.

On another thought about chainplates... The Alberg 30 as you know has short chainplate knees that sandwiched between shelf and deck. Since I have all the knees removed and shelf as well.. is there any benefit at this point to make the chainplate knees longer and further down the hull to enlarge the area of adhesion as well the tension would be spread out over a larger area. more of a triangle knee, about 14 inches from deck to the end of kneed.

Just to mention I am not putting back the V-berth as it was. The old shelf that was there will still be there but wrap around the knee if making this bigger makes any sense. The Shelf will be further from the hull and the v-berth will not be a place for sleeping. Rather will have storage system cabinetry made. No one in my family or friends will sail so I am making the interior as for me.

Your extensive experience is much appreciated.
Windcall
Bottom Paint Application Technician
Posts: 22
Joined: Sun Jan 12, 2020 6:19 pm
Boat Name: Windcall
Boat Type: Alberg 30 1969 Hull 397

Re: Chain plate Alignment

Post by Windcall »

Thank you Atom

I came up with 78 degrees... ... now that you explained how to do it.. I feel stupid lol...
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atomvoyager
Moderator | Revitalizer of Classics
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Re: Chain plate Alignment

Post by atomvoyager »

As you might have seen in the following A30 chain plate replacement video, I glassed a knee extension for the forward lowers connected to the deck, hull and shelf. If the shelf is gone then I would extend the knee lower as you describe. If you are putting the shelf back and glassing it in then you don't need an extension, but it won't hurt. Or maybe you want the shelf removable and not glassed in. I like to glass in shelves and other cabinetry where possible, particularly if I'm replacing it anyway so as to strengthen the boat.

https://www.youtube.com/watch?v=LnAsYbcRJds
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