How much space to allow for anchor rode?

Discussion in 'Metal Boat Building' started by pdwiley, Apr 13, 2012.

  1. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    MT1 is a consideration on a chain/rode locker. Do you know what your MT1 is? A quick way to determine the MT1 is to get the square of the water plane area, multiply by .68 for square meters or .35 for square feet. Then divide this number by the waterline beam.

    Assuming a reasonably dimensioned 39' sailboat, with a 28 - 29 square meter (305 sq. ft.) water plane, you could expect a considerable bow down trim depending on where you place this locker and how much you stuff into it. Your suggested location seems better then most, but figure out your resulting trim, before you commit to a locker and/or a specific rode type/capacity.

    Again assuming a 55% CB location and a favorable locker location, well aft of the stem, you'll still have one large trimming moment to consider. The math is quite simple, so play with the numbers and see what you can live with, compared to what you actually want.
     
  2. pdwiley
    Joined: Jun 2008
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    pdwiley Senior Member

    Thanks. It's a Colvin Witch design and the rode goes between frames 1 & 2 in the design. I have no idea what the area of its waterplane is, I'm a dumb retired biologist/software person.Thing is that a lot of US boats seem to use rope with minimal chain whereas I'm going to use all chain and I am aware there's a big weight difference. The trim is a consideration. That's part of the reason I said 60m of 10mm chain; it'd be nice to have 100m but if you rarely use the extra length, it's a lot of weight where you don't want it. I'd rather put the extra in the keel recess a lot further aft.

    Anyway looking at the space I can't see any real downside in making the bin for the rode as big as will fit through an opening 550mm x 550mm (size of the opening in the frame 2 bulkhead), 2 parts (P & S) and shaped to the form of the available space. Not like I'm going to be using the space for anything else.

    PDW
     
  3. Submarine Tom

    Submarine Tom Previous Member

    Seems like running 100m of chain down into your keel for storage would be the ideal theoretical solution.
     
  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    60 m of 3/8" chain is in the 150 kilo range, plus whatever else you're stuffing in there. This is 2,250 kilos of trim at 15', which is a very conservative estimate. Knowing what your MT1 is, you can find the amount of trim change.

    Can you be more specific about the design, possably post a lines drawing? Knowing a little more about the design will permit a simple trim calculation. Odds are your weight is considerably different and further from the CB then suggested, so some accuracy is necessary, which requires basic dimensions and centers.
     
  5. Milehog
    Joined: Aug 2006
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    Milehog Clever Quip

    Silver Raven, our boat is a C-Dory 22 Cruiser. A small pilot house pocket cruiser that prolly weighs 3,700 lbs loaded to the gills.
    The main anchor is a 6 kg Rocna with 20' of 1/4" chain and 7/16" New England Ropes 3 strand nylon line. The secondary is an 11 lb Hydro Bubble plow that breaks down for easy storage. It's rode is 15' of chain and 3/8" N. E. R. 3 strand. The whole set up fits in an old canvas rucksack. I emphasize New England Ropes because it is vastly superior to the light, flimsy, loose imported generic crap that I can't trust.
    There is a rode "locker" in the bow with a deck pipe fitting the rode goes through. There is room on top of the main rode for the rucksack the secondary lives in. The boat came with a 7.5kg Bruce knock off and I bought a 13 lb Danforth clone that sits next to it in the garage.
     
  6. bpw
    Joined: May 2012
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    Location: Cruising

    bpw Senior Member

    I know I am a bit late on this thread, but if still looking for data....

    I have 100ft of 5/16 chain and about 150ft of 1/2 3 strand line (though it looks a little bigger) in a 5 ft tall piece of 8 inch PVC pipe.

    Works great, bottom is capped so keeps mud etc out of the boat, just need to empty every once in a while. Rope and chain self stow really well because of the tall narrow shape, and because its so narrow I can fit it back next to the mast. Keeping weight out of the bow.

    This is aboard a 28 ft "day boat" that just finished a 52 day passage! While carrying 100 gallons (80 to 100 days for 2 people) of water and all the fuel we need (5 gallons for the stove) and not a thing stored on deck except a flat folding dinghy that is lower than the bulwarks.
     
  7. Silver Raven
    Joined: Oct 2011
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    Location: Far North Queensland, Australia

    Silver Raven Senior Member

    Gooday. WOW - Lots of valuable info - Thank-you so much for sharing. How many times did you use all the chain ??? & did you deploy any of the rode ??? - At a quick glance - I can't see how big or what type your anchor is. Sure hope you had a great time !!! 52 days is a nice length for an extended passage.

    Again - Thanks for sharing you valuable knowledge. Ciao, james
     
  8. bpw
    Joined: May 2012
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    Location: Cruising

    bpw Senior Member

    There are a bunch of details of our anchor set up in this thread:

    http://www.boatdesign.net/forums/mu...ger-cold-weather-cruiser-project-41658-5.html

    We generally dump all the chain out no matter what the depth, if we don't have enough room to swing the second hook comes out. Then rode added as needed for deeper water, more wind etc. Not unusual to have 200ft out if we have the swinging room. Chain and rode don't help in the chain locker!

    No idea how many times we have anchored, the boat has been on the hook or at sea for something like 20 of the last 26 months.

    Current anchor is a 15kg Rocna, but its new, until recently we mostly used a 10kg Bruce, bit undersized but was fine in Mexico and we had some bigger gear ready to go if needed.

    The passage was fun, but it does get a bit dull after a while, nothing much happening out in the deep pacific. Much more interesting being along the coast with all the animal life.

    Should add, I just noticed Frosty's comment about inability to anchor where you want on a small boat due to lack of rode, between anchor chain, rode and shore lines we have close to 2000 ft of usable anchor rode on board.
     

  9. pdwiley
    Joined: Jun 2008
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    Location: Hobart

    pdwiley Senior Member

    Thanks for that, the information is useful. I haven't built anything yet as I usually try to gather information well in advance. Putting epoxy slime paint on the keel recesses has been taking more time than I wanted as the temperature is low enough to extend curing time.

    PDW
     
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