Sunday, October 14, 2018

Actual Anchor Loads

I spent a LOT of time researching this topic, through the literature and by staring at a load cell for hours and hours. I used all sorts of rodes and snubbers, in all weather, on a number of boats.

ABYC (American Boat and Yacht Council) set standards for rodes and deck hardware 50 years ago, based on testing with boats on all-chain rode in open harbors and shallow water (but no breaking waves) and no snubber. In fact, these values are VERY close to what I got testing in similar conditions. This is very much a worst case situation and is something you should NEVER do, but is not a bad basis for the design of something that cannot fail.


Interestingly, every investigator reported 3-5 times less when they measured the strain on their boat (me too). Of course, they wisely anchored in deeper water (lower waves and more catenary), used rope, or used a snubber.

Looking only at the 60 knot row, which is very likely the most you will ever face without some protection from trees or shoreline, we see that the wind load is only about 20-25% of the ABYC load. Waves and snatching make up the rest. If you use a long chain in deep water (at least 20 feet), a long  snubber (35'-50'), or a rope rode, the load will be only 25-30% of the ABYC value.




For larger boats or those around coral and rocks, all chain is nice. Rig a LONG snubber, even if you have to cleat it at the mid-ships or stern cleats to keep the connection off the bottom.
With smaller boats and mud bottoms, the answer is rope. It is much lighter, gives good shock absorption, and lasts as long or longer, if it is protected from chafe and corrosion of chain is considered. Go oversize for durability, if you like; it will last longer be less prone to excessive stretch.

I've even gone to a Dyneema bridle to reduce yawing and to reduce the sometimes-excessive stretch of all-nylon rode. Because the bridle does not distort under shifting loads, yawing is reduced.
[Images excerpted from Rigging Modern Anchors.]

Sunday, September 30, 2018

Helmets

After one more like wack on the head, and an invitation from a magazine to write an article, I fond myself pondering where on the safety scale helmets might fall. I'm think we are in the midst of a big change in mind set, akin to bicycle helmets in the 70s and 80s.

US Sailing has this to say [emphasis added]:


2015. A word of caution to all persons who consider using helmets while sailing. There is no data to confirm that helmets will prevent concussions. The brain injury comes from the acceleration/deceleration from the strike, which is apparently not substantially altered by a helmet.
Helmets have been shown to reduce the incidence and severity of facial and skull fractures, contusions and lacerations but not concussions. 

Concussions seem to occur more easily in pre-teen and teens. We also need to be aware that adding a helmet to a young head makes the head a “larger” target and could possibly lead to more head strikes.
Therefore, it is the position of the Sports Medicine Committee of US SAILING that helmets should be considered and encouraged but not mandated for:
♦ aggressive competitive sailing,
♦ crew positions at increased risk for strikes to the head, and
♦ sailors who are learning the sport and thus unfamiliar with the position and movement of rigging and equipment.

In the event that a concussion or head injury occurs, treatment and the evaluation for a return to activity should be done by a trained specialist. 

David Jones, M.D., Chair of the Sports Medicine Committee
Thomas Hubbell, M.D., President of US Sailing


Kayakers have long worn them. In fact, it is the law in many whitewater areas, including my home Potomac river from Great Falls to Chain Bridge. It's easy to get pasted in the head by a rock while inverted.

 The Protec Ace is top rated and economical. I like to for whitewater kayaking as well.

I googled ocean racing accidents. While head injuries represent only a small portion of the total carnage, they represent nearly half of the injuries resulting in evacuations or retirement. I strongly suspect they are a factor in some of the drownings ("So-and-so was knocked overboard by the boom [or spin pole, or banged across the deck] and was recovered drown.). You don't need a skull fracture to be dazed just enough to swallow some water after going in head first.


A little impractical, I think. For a helmet to prevent concussions it needs to be thick enough to provide deceleration distance.All kidding a aside, the risk of entanglement in lines and increased impact when hitting the water at speed disqualify and oversized design.

I googled cruisers. There's a good list of injuries in heavy weather. I've been tapped a good number of times, but a cap is enough for those. I did get swatted to the deck once, but it was just a skimming across the crown and did no damage. But it makes you think.

And then there is the danger of the helmet itself. I wide rim, like a bike helmet could snag on ropes. A brim could add to rotation or catch on the water at high speed. A helmet needs to be compact, such those we are seeing on many performance boat crews. I need to feel the wind. It cannot block my vision. On the other hand, it could keep my head warmer in the winter and it could double as a rain hat. Which brings up the matter of interference with the hood.

As I descend the rabbit hole of article research, I'm becoming convinced they are rational in many settings. Youth through college sailing, beach cats and skiffs, and maybe any small boat racing where mark rounding get crazy. Ocean racing in rough weather. Up the mast off-shore for everyone.

But what about cruising scenarios?  The foredeck when it's bad. Perhaps it is like headlights (if the wipers are on, the head lights must be on); if tethers are needed, so is a helmet? No, that seems like too much as a general rule. On the other hand, seatbelts don't seem very useful until that one instant you need one. When I look at the numbers, including only experiences sailors, It's hard not to see PFD, tethers, and helmets in a similar light. The accident numbers say they are all in the same range. Discomfort and expense are all in a similar range, I think. You wear a hat and I'm pretty used to my bike helmet. But I do miss the wind in my hair and I don't always wear it.

Food for thought.


 

Friday, September 28, 2018

Edit: Why a Jordan Series Drogue is NOT a Very Good Steering or Speed Limiting Drogue

Usually there is a specific event, often personal, that motivates me to research something. In this case, ~ some years ago I jammed a rudder on a submerged tree. I remembered a the loss of Too Good to Be (Alpha 42 Catamaran) due to a bent rudder, and several friends who have been towed in after striking logs. A boat was towed hundreds of miles across the Gulf of Mexico last year, after loosing a rudder in nice weather--with a steering drogue I would have been underway again in 10 minutes, no need to make a call, other than perhaps a Pan-Pan to the US Coast Guard as a condition report. It occurred to me that emergency steering is a least as important to the coastal sailor, because there is so much more debris to hit. So I got interested in emergency steering and drogues in general. 


A JSD is unarguably the correct tool for most serious storm conditions. You can Google "JSD Coast Guard Report" for the details, so I will only summarize. It was an innovative and clever leap forward that sidestepped many of the problems associated with conventional drogues:

  • No single point of failure.
  • Can't tangle.
  • Can't be thrown forward by a wave, because the load is distributed.
  • Can't pull out of a wave face, because the load is distributed. 
  • Very smooth drag.
  • No single heavy piece to handle.


However, it has serious short comings when used at higher speeds as a speed limiting drogue, or more importantly to me, for emergency steering:


  • The cones will shred. Unlike a JSD, which spends most of it's time at 2-3 knots, a steering drogue sees a sustained 5-8 knot speeds, resulting an average load per cone that is 2-10 times higher. Although reversal in direction is less common than for a JSD in a serious storm, they will be working near the surface, breaking out of waves regularly and getting pounded.
  • Longer endurance is required. It will be used for a week of more, not overnight. On a long passage, it might be deploy several times, just for comfort.
  • JSD cones are too close together for proper flow at the higher speeds. Testing of JSDs and plain cone drogues suggest drag is reduced about 30-40% by close spacing. Increase from 2 feet to 3.5-4 feet.
     
And yet it has  potential advantages:

  • No single large element to handle. Pulling a Delta drogue 72 over the transom in rough weather is no picnic. That is an understatement. Single drogues much larger than 2 feet (Seabrake 24, Delta Drogue 72) are simply not manageable by normal or aging sailor in boisterous conditions. Standard JSDs have a reputation for difficult recovery, but this would be 1/3 the length; I'm confident it is easier to man handle than a conventional drogue.
  • Less chance of tangling during deployment or recovery. The worst time with a standard drogue is recovery it; I've had a few get in the rudders.
  • Will not pull out of a wave. This is a considerable advantage, because every conventional drogue becomes unstable above about 5 knots in the presence of steep waves. The wave increases the angle of the rode to the water and the drogue pulls out as the wave passes it. The best you can do is try to put this out of phase with the peak load, which in confused seas, is impossible. This is the primary reason conventional drogues can fail catastrophically as the storm rises; everything seems good, until the speed + load reach a critical level, the wave steepness builds, and the drogue pops out. If it is on a nylon rode, the rode contracts, the drogue snaps forward, and maybe the wind and breaking wave help it along. There is no magic design that can make a single drogue run deep enough to avoid this cycle. I observed this hundreds of times in testing.
  • Drag will be more adjustable. Sometimes you need a lot of drag to make the boat track, and sometimes less would increase both speed and pointing (yes, you can sail upwind with a drogue, just not very high).



Recovering a Delta Drogue 72 (about 24-30 inches across). Even in clam weather it is extremely heavy and must be dumped first--impossible unless you are standing at water's edge, which won't always be practical. Other drogues are awaiting their turn in the dinghy, including a Galerider, Paradrogue, Seabrake, cone, and JSD  from Ace Sail Makers.

In use the drogue is often pulled in very close to the transom, to reduce drag by lifting the drogue. This is how a Seabrake 24 deploys in 10-25 knots for emergency steering; in light winds it is in close, in stronger winds I you add an extension between the chain and the bridle.


I decided to test a modified JSD (call it a Series Steering Drogue) as a speed limiting and emergency steering drogue:

  • Fewer cones. Only about 1/3 the number specified for storm service.
  • Strong construction. Upgrade to 6.5 ounce sail cloth and hem the leaving edge (Ace Sailmakers is building JSDs this way now).
  • Increase cone spacing to 4 feet for better flow at higher speed.
  • Less weight. 10 feet of 5/16-inch chain should be enough, or an 8-pound mushroom anchor. The rogue will be more naturally resistant to surfacing at high load or high speed (same thing).
    The most obvious difference is the that the series steering drogue is much longer, about 75-100 feet. But this is part of its strength--only by distributing the load can the drag remain steady is something as fragile and turbulent as water. 



    The standby rode is to allow us to seamlessly add the rest of the JSD if conditions deteriorate; just attach the rest of the JSD, along with a dedicated bridle attached to the JSD chain plates, and cast the spinnaker bridle free (you will recover it when you recover the JSD).



    Alternatively, A conventional drogue, such as the Seabrake can be used as the new primary drogue. Again, the stand-by rode allows for seamless deployment. The Steering Drogue will still provide stabilization for the new primary drogue (the Seabrake), much like a JSD, but with more adjustable deployment.




    And it was a complete failure. 

    First, the trade mark JDS droop, which allows the tail to run deeper under water does not occur. At higher speeds (5-7 knots) the JSD is pulled right up to the surface by water drag. The droop is not unique to the JSD design, but is only an artifact of Jordan specifying enough cones so that enough drag has been added to reduce the speed to 2 knots or so, which allows the tail to sink. Any drogue design will do this in an equivalent manner, as long as there are at least 2 units and the speed and weight are equal. Although it may retain some resistance to damage if the motion is reversed on the back slope, this is not he case with steering and speed limiting drogues--motion is always forward.  

    Second, smaller drogues (cones in this case) are inherently less stable when running near the surface, and are more easily disturbed by the movement of waves. A large drogue can run at shorter scope because it pushes a lump of water above it, whereas small cones push only froth. The small cones simply splash on the surface, completely unstable, unless the scope is at least 75:1, which is impractical with a 4-foot transom (I had to test them by anchoring near the waterline). Cones also zig-zag and flutter. This is very hard on their construction, fatiguing the cloth.

    Efficient shapes. A cone produces only 55-70% as much drag as a Seabrake or Delta Drogue of the same size. The design is easy to sew but not advanced.



    Finally, drogues are inefficient if they follow too closely behind one another, much like a racing cyclist enjoys the draft by following another closely, and the higher the speed the more significant  the effect. Thus, a steering drogue based on JSD cones must have much greater than normal cone spacing and becomes very long, about 50-60% of storm drogue length length even though it contains only 20% of the number of cones. This is quite cumbersome compared to a single unit, with no apparent advantages. The combined effects of inefficient shape (essential, because so many must be built), close draft, and small size (unstable near surface) are limiting to the function of a truncated JSD.

    It seems it is a matter of horses for courses. The JSD principle has considerable advantages for severe storm management, but only if designed for sufficient drag to slow the boat to less than 2 knots. If truncated to allow for better movement, the design has no advantages and more failings.

    Darn. 




    Monday, September 24, 2018

    Free Stuff

    Actually, just a limited time offer for a free Kindle book.

    Rigging Modern Anchors is being offered by the publisher for free to people with Amazon Prime or Kindle Unlimited. At some point it will go to $9.99, so for our mutual benefit, please take advantage of this offer.

    I could really use some sales volume and some kind reviews (which I hope I have earned), so I'm reaching out to my readers in the hope that you will enjoy a little light reading.

    This is perhaps more a technical study than "anchoring for beginners," but there is much for the beginners as well; every time I anchor I remind myself that good fundamentals make the greatest difference. 


    Now that I have a smaller boat, I've continued testing, but with a smaller boat spin. Much of this made it into "Rigging Modern Anchors," but there is more to come, as investigate doing away with chain and what that means.

    Happy Reading!

    Tuesday, September 11, 2018

    Rigging Modern Anchors

    Working with a bricks and mortar publisher to get this in print has been a lengthy process for me, but well worth it. It encouraged me to dive far more deeply into the technical side than I might have for my own needs, and the result is the most technically detailed boat on yacht anchoring written. And I don't feel I'm bragging unfairly. I simply did the work. While others have brought vast blue water cruising experience to life, I spent years with a load cell, digging around in the mud. Hardly glamorous, but science is mostly about diligent work.

    Available in print through Amazon.




    Rigging Modern Anchors

    Rigging Modern Anchors

    First print edition, 2018, by Seaworthy Press. About 156 pages.

    I've been setting and trusting anchors with my life (climbing) and my boat (sailing) for 35 years. I've been testing and documenting anchor testing for 5 years, and I've spent the last two sifting, collating, and analyzing all that I have learned. The result, I believe, is a complete description of what is actually going on below the waves, not just descriptively or as oral history from an old salt, but with numerical back-up everywhere I could provided it. I hope it helps. I know I sleep better. From the back cover of the book:
    “Rigging Modern Anchors” demystifies anchoring with today’s modern anchors. Through years of systematic testing, Drew Frye has produced a new benchmark of understanding based on empirical data instead of anecdotal wisdom, passed down from one sailor to the next without proof or deep understanding. In “Rigging Modern Anchors” we dig deeply into the how and why of anchoring, using hard numbers as our foundation.


    Included are in-depth discussions of anchoring basics, loads, scope, and the effects of cyclical loading, soil consolidation and bottom characteristics on holding power. Special attention is given to problem bottoms such as very soft mud and rock. There are anchor-specific observations, discussions of tandem anchors and rigging methods, plus an extensive appendix containing test data, open source designs for bridle plates and anchor turners, strength and toughness for various chain types, anchor connector recommendations, anchor sizing guides and more.


    Proper anchoring technique, rigging, and gear selection is vital to the safety of ship and crew. Instead of hoping your anchor and rigging scheme will hold, read “Rigging Modern Anchors” and be sure.


     

    Monday, September 10, 2018

    Unsinkable

    Every few months I see a picture of a multihull sinking. This should never happen, not with a few crash tanks, bulkheads, and no ballast.


    Yes, there are heavy things in there like diesels, but there is also foam core and empty tanks.

    The PDQ 32, on the other hand, is quite unsinkable. I had a through-hull failure once and it didn't even get the floor boards wet.
    [the load waterline is on the lower edge of the boot top stripe]

    With 2 crash tanks forward, one aft, and two bulkheads, you simply can't tear a big enough hole.

    I know what it is. People don't want the cabin space chopped-up by walls. Their funeral.
    ------

    As for my F-24, it is easily supported by the amas and the beams, no crash tanks required. No worries. But I would add them anyway, if I were sailing far. I'd seal off most of the space under the V-berth and under the cockpit. A day's work for peace of mind, and no new access problems.


    Monday, August 27, 2018

    Spare Yamaha 9.9 High Thrust Props for Sale

    In the process of making room for more boat stuff, I came across these, which should go.

    Used, but functional. In my opinion, every PDQ owner should carry at least one spare, if not two. Once in a while you will wind up a lift line or find a crab pot. It's a 5-minute change... if you have a spare. I always carried a spare.

    They're ~ $70 on e-bay. How's about $50 for all three, plus whatever shipping costs (unless you pick them up, either Vienna, VA, or Deale, MD.



    Time for Bed


    Tuesday, August 21, 2018

    Depth of Discharge vs. Battery Life

    It's a cruiser mantra that lead acid batteries should never be taken below 50% state of charge. There is some pretty convincing math on this for batteries that are cycled daily,including full-time cruisers and off-grid power systems. On the other hand, golf carts go lower than that every day.

    And for the rest of us, who cruise weekends and a few weeks now and then, we don't rack up that many cycles, perhaps 100 in 5 years and 200 in 10 years. Northern holiday cruisers are even more challenged to rack up high cycles, with the boat out of the water half the year.

    Even using shallow cycle designs, which we are not, we'd be hard pressed to hit the cycle limit within 10 years if we took them to 60 %, and we would just hit it in 5 years at 80% discharge. With standard deep cycle batteries, we could discharge to 80% far more times than we will ever spend the night on the hook. The batteries will die of corrosion, failure to recharge, or failure to water first.
    This has been my experience. I use relatively small battery banks and discharge past 50% regularly. I do recharge as soon as possible and I do check the water. I typically have gotten 7 years, whether cruising frequently or not, before I loose enough capacity I replace them (never complete failure, such as a shorted cell).

    Why what some would consider an undersized bank? Because on a multihull, weight is worth money. My boat cost $20/pound and I feel every pound saved is worth $20 in performance. Otherwise, I would have purchased a slower boat. Carrying an extra battery (75 pounds) costs $1500 in weight penalty.First, I don't believe adding a battery would extend the battery life in proportion to the added purchase cost; they would last perhaps 15% longer and cost 25-50% more to replace. The $1500 weight penalty stands. The only upside is additional reserve capacity, which isn't worth $1500 to me.


    (That's 25 degrees C, not 250C like it says)

    I've had enough different boats to understand that for each boat, my answers to these questions would have been different.
    • How big is the bank? A single group 24 battery is minutes to change, but a big bank of traction batteries is a project.
    • How critical is power failure? An outboard can be pull-started, a big diesel is a problem.
    • What charging sources are available? How many days between full charging?
    • How often is the boat anchored-out? Are we talking thousands of cycles or hundreds during the life of the battery?
    There is simply no way that one answer is right for everyone. On my last boat battery maintenance was serious; lots of appliances and significant battery cost. On my F-24 weight matters, I have one slim 50W panel and a throw-away group 24 battery. I don't have any electronics that matter to me and I pull start the engine. A 5-pound Li ion battery is probably the smart answer, providing all the power I need for about the same money. Very cool.

    I need to look into this farther.

    Saturday, August 11, 2018

    Dual Rod Holder From Scraps

    Or rather from a stern rail motor mount that the the PO liked but I had removed. In my mind, either the engine should be able to stay on the dingy or...
    • The davits or hoist is weak. Upgrade.
    • The engine is too damn big.
    • The dingy moves too much, in which case it should be triced-up.
    • The dingy is vulnerable in rough weather. Not the case on most catamarans, since the davits are forward of the transoms.
    The mount has been resting in a might-need drawer for 6 years but now enjoys new life.

    It's primary purpose is to hold my 2 mini-outriggers (2 x 6' outriggers give me an effective beam of  26 feet, easily trailing 3-4 lines without tangles) while not trolling. They can't left in place during docking, and placing them in the outboard rod holds inhibits easy boarding and blocks the holders for other uses. I find rod holders handy for other things as well--boat hooks, walking sticks, gaffs, oars--so i can never have too many.

    I dislike commercial holders since they only grip the rail without twisting if tightened so much they scar the rail. This never will, since it uses an up-right for bracing.



    Construction was simple enough. I had to slot the back to accommodate a brace. The 2" SCH 40 pipe is attached with counter sunk #10 machine screws. In the background are a pair of kayaks lashed to the top of the davits, the most convenient storage space.


    The lures are home-made too.