After months of absorbing information from this site as we prepare to outfit our new boat
(that should arrive in a few months
), I think it is time for me to give back a little. One big question I have had is regarding anchor
selection, and based on the number of posts (and opinions) in this Anchoring
forum, I think this is fairly common. Being a visual kind of person, I struggled a bit with the sizing tables that manufacturers make for their anchors as they seemed a bit too cut and dry and I felt like a few questions were not answered well like "how big a jump is it really if I went with the next size up?"
As I have pretty much narrowed down my quest for an anchor
to a Rocna
, I created a more visual representation of the sizing chart on the Rocna
website that I hope may help others. To use it, simply draw a line up from your boat
length and across from your boat
weight and where they intersect is where you boat falls into the sizing scheme of things. You can then make your own call on whether or not upsizing might make sense (i.e., are you close to a line or a fair ways below it? Does your boat have a lot of freeboard or sail at anchor, tending to increase loads?). Also note that I have left off Rocna's three largest anchors since including them made it difficult to interpret things at the lower / mid range I was most interested in.
I also found a lot of information regarding anchor size or weight that, while extremely helpful, didn't really apply to someone with a 37' / 20,000 lb. boat. There were several testimonials from people using 100+ lb. anchors on a boat of size X that held them for a day of 50+ knot
winds, but how would that scale to my situation where there is no way I am putting a 100+ lb anchor on the bow? Especially with respect to a Rocna that supposedly has more holding power per lb. than a more traditional anchor? (And note the "supposedly", I am not saying this is necessarily the case so please don't fixate on that one statement!) After researching this, I have come to a personal conclusion that holding power isn't a linear phenomenon of anchor size and someone's experience with an anchor that weighs 150+ lbs couldn't really map to a West Marine
test that looked at 30 lb anchors (hence the debate over why a Bruce seems rock solid over 100+ lbs but seems to have problems setting and holding in the 25-75 lb range).
Luckily I found the following information in a somewhat recent post at Steve Dashew's blog
"At the risk of repeating ourselves (this topic is covered in great detail in our books), and using one of the new generation highly efficient hooks like the Rocna, Spade, or Bruegel, we would carry the following:
- Sundeer 56/60 – 110lb/50kg
- Sundeer 64/68 – 176lb/80kg
- Beowulf 80 – 240lb/110kg
- For yachts in the 40 to 50 foot range – 80lb/38kg
- For yachts in the 30 to 40 foot range – 60lb/28kg
This assumes a chain rode
SO, weeks of my agonizing over tons of information only to find things neatly summarized by a respected expert in the cruising field, for the anchor I am interested in at least.
It is nice, however, to get some independent confirmation of my final decision for an anchor for our particular boat (prior to reading the Dashew's opinion, I had decided on the 55 lb Rocna even though according to their sizing table the 44 lb should work).
One last comment, the spreadsheets and discussion about anchor rodes on Alain Fraysse's website
are a fantastic resource. The guy has written a doctoral dissertation on rodes and in my opinion deserves some sort of award
for sharing all that hard work
for (as far as I can tell) no personal benefit.
I hope this helps someone else...