Thursday, 2 April 2015

From the ground up

Now that Mareda has arrived (!!), the outfitting has begun in earnest, and we have to make some firm decisions about equipment.  This is in stark contrast to the decisions we've made up to this point, which mostly involved flipping through the catalog and saying “Cool !  Let’s add one of these !” 

 **note: I'm taking lots of photos of the commissioning process.  See our Facebook page for all the latest photos and updates ! 

Starting from the ground up, we've been thinking about anchors and chains this week.

The standard offer for the SO 379 was a 16kg Delta anchor with 28 meters of 10 mm chain and 40 meters of 18mm line.  (That’s a ~ 33 lb anchor, ~ 85 feet of 3/8” chain and ~120 feet of line).  This all seemed a bit light to us, especially for anchoring in the meteorologically-capricious Mediterranean.  At one point, I tried to convince myself that with a swing-keel we could get closer to shore and wouldn't need so much chain, but for reasons I can’t quite put my finger on, I decided that this was dumb.

From technical reviews and personal testimonies of friends, we knew we wanted a Rocna anchorWith Mareda's length of 11.3 meters and weight at just under 7 tonnes, the Rocna sizing charts suggested that an anchor of 15kg would be adequate (where “adequate” is based on tests in 50 knot winds with associated surge and poor holding conditions).  The chart indicated that 8 mm chain would suffice for our boat with such a Rocna anchor.  For the SO 379, 10mm chain and windlass is standard, so we felt good about being over-spec’d (if that is, indeed, the case). 

But no one said anything about the length of chain required.  The basic rule (which of course has many variations) is that you want to put out a length of chain that is 4 times greater than the water depth at high-tide.  (Example: moor in 3 meters of water, put out 12 meters of chain).  This all depends, of course, on the conditions in which you anchor.  An interesting rule-of-thumb I saw recently:  winds of Beaufort 3 = 3 x chain length; winds of Beaufort 4 = 4 x chain length, etc., etc.

After searching through numerous web-sites and talking to friends who know the Med well, we decided that 40 meters of chain was the minimum for the Med.  If 40m is minimum, I thought, why not go for 50, just to be safe?  When I mentioned this to Patrick, he turned on his best sarcastic voice and said, “Yeah, great ! and Hey!  Why not 60?  Why not 75?  What the heck… let’s make it an even 100 !”

Slinking back to my office, I started thinking about it.  Why not more?  That’s when it dawned on me that there must be limits, real limits, based on weight (and not on snitty, financially-motivated comments from one’s husband).  How much does all that chain weigh?  When does your boat start to become nose-heavy?  And what about the windlass?  If you've deployed 100m of 10mm chain, is your windlass strong enough to pull it up?

Easy stuff first.  10 mm chain weighs 2.25 kg / meter, giving us 112.5 kg for 50 meters.

Medium stuff next:  The windlass (Quick Aires 1000 W) has a working load of 120 kg.  Its maximum working load is more than double this, but we don’t like pushing electrical / mechanical devices into the red zone, do we?  So 50 meters of 10mm chain is getting quite close to the working load.  Add a 15 kg anchor and we've gone past it.  Granted, the situation where you would have 50 meters of chain and the anchor hanging through the water column all at once is rare and you could push the beast hard for a short period of time, but you just never know, do you?

Hard stuff now:  When does the boat start to get too nose heavy?  As with most hard questions in life, the difficulty lies in defining the question.  What does too nose-heavy mean?  The only advice I could find on this was “sail the boat with the weight in the nose, then move the weight to the center of the boat and see if she sails better.”  Humph.

I’m still a bit at a loss as to how to approach this one.  The standard equipment for the SO 379 gives 79 kg versus the 112.5kg we want.  The difference is peanuts, right?  Let’s just assume (because I like the answer I get when I do this) that the architects have given us a safety or performance margin of 2 relative to the standard weight they propose, which means that we could go up to 158 kg without getting too nose heavy.  Since we’ll be well under this mark even with 40 meters of 18mm line attached to the chain, all’s well.  With time, I’ll convince myself that I feel comfortable with this.

In the end, we decided to go with 40m of chain and 40m of line.  Patrick triumphantly pointed out that this was the decision we had come to before I did all these calculations. But what else was I supposed to do with a cold rainy afternoon?  (I’ve had other rainy-day inspired fits of calculations, including rudder angles and hull speed.  It rains A LOT in Brittany…)    

So our principal mooring will look like this:  
  • Rocna 15kg anchor
  • Articulated Kong junction between the anchor and the chain
  • 40 meters of 10mm chain
  • 40 meters of 18 mm line, connected to the chain with a splice directly onto the chain (if the 18mm strands fit through the 10mm chain links… to be determined shortly).
  • A double bow roller, which the Jeanneau dealer says has been reinforced after the first models had problems.
  • A snubber
  • Depth marks on the chain and an “aide memoire” of what the marks mean in the anchor locker.  I think I’ll stick with my spray-paint technique.  You have to re-apply the paint every year, but it’s quick and easy to do. 
  • The 2nd anchor:  a 12 kg FOB with 10 meters of 8mm chain + 20 meters of lead line.  I’ll attach another 20 meters of line to that when we go into the Med.  After 2 years of sailing around northern France, the Channel Islands, and northern Spain, we've never needed the 2nd anchor, but then again, we've never had a boat we could beach before, either !

Our high-tech chain depth indicator system.

Our memory aid of what those colors mean !

2 comments: said...

How lovely to buy a new boat! I read your comment in a different post about those incredible HR 40's. Yes, who wouldn't want a boat like that? We ended up with a boat much larger than we were looking for because we fell in love. You know how that goes. It's a challenge in marinas to be sure, but there is room for our adult kids and that was important to me since we'll be giving up the family home. Still, I'd love to sail in Europe, especially France and also the UK. After reading some of your posts I'm thinking we might want a swing keel boat for that. Who knows what the future will bring? Loving your blog.

MH said...

Hi Melissa, Thank you for the nice message and your great blog. Even though we're in the process of buying a new boat that we love, your boat still makes me dream ! Let us know if you ever make it over to Europe.