Friday, February 17, 2017

Book Store Up-Date

The Book Store has been updated.
  • Two new titles:
    • Keeping a Cruising Boat on Peanuts
    • Faster Cruising for the Coastal Sailor
  • Four titles are now avaialbe as PDF:
    • Keeping a Cruising Boat on Peanuts
    • Faster Cruising for the Coastal Sailor
    • Single Handed Sailing for the Coastal Sailor
    • Circumnavigating the Delmarva--A Guide for the Shoal Draft Sailor
The anchoring book ("Rigging Modern Anchors") has been a very serious undertaking and will hopefully be going the conventional paper publication route. It contains a lot of new research and I've had some good reviews from within the industry.

 This is where most of the work gets done. There's a lot more to it than typing.

Thursday, February 16, 2017

MastMate, The Easy Way

  Rope climbing systems are all the rage--and they do have the advantage of simplicity--but my good old rope ladder has served me well for 25 years. Heck, the surveyor I used on my current boat used a Mast Mate. But there are a few tricks that help.

A climbing harness would be much better.
  • Hoist Outside the Track. The instructions are adamant that it MUST be in the track, and it does climb a little easier that way, but I've been setting it free for 20 years. After hoisting to the top, lower 6 inches, clip the lowest eye to something solid, and tension hard with the halyard winch. To me, it simply isn't worth unloading a part of the sail, opening the mast gate, and fooling with 30 slugs.
  • Wear a Climbing Harness. It should fit tightly enough on the waist that it can NOT be slid off, even if you were to fall upside down. If this is not possible because of physique, you cannot climb.
  • Use a Second Halyard as a Safety Line. I tension the spinnaker halyard and secure it to the mast base. A run an ascender (rope grab) up the line to protect against falls and to allow rest. Alternatively, a crew member could tail it on a winch.
  • Wear slim profile shoes. Easier to get in the steps. I'm happy with deck shoes. Most running shoes stink.
  • When not in use, store the ladder coiled, from top to bottom, with the steps flattened in the correct position. This will insure that they open correctly and will make hoisting easier (won't catch on the spreaders). Secure with twine to make certain it stays that way. when hoisting, open the steps as they go up.
Coil for storage. I'm a "crammer" by nature, and I can tell you from experience, it is a mistake.
  • Carry Several Slings for Securing Yourself at Work Points. 4,500 pounds minimum breaking strength.
  • Do not carry any tools while climbing. Haul these up with a trail line. I like an electricians bag.
  • Haul up a climbing rope. Use this to rappel down, saving time and effort.
  • Wear gloves while climbing. Vinyl coated work gloves like Atlas Fit grip the mast well.
 I dump the tools out and take only what I need.

Saturday, February 11, 2017

Book Questions, Comments and Research Ideas

Something in the text is unclear? A subject you would like to see researched and written up? Please post the question here. I'm always searching for new subject matter.

Stainless Steel Bolt Specifications

Whether bolting on some new project, or trying to understand why something failed, you need to know how much a fastener can hold.


Clamping Force. When torqued to ANSI specifications, this is how much a bolt will hold before it becomes loose due to stretch (bolts stretch under tension--everything does). If the bolt cycles past this load, it will move around, the hole will be damamged, and something will break. Additionally, this is beyond the working Load Limit (WLL), so we wshould never get here.

Sheer Strength vs. Tensile Strength. Only important so that we understand that they are slightly different. Since most loads are a combination, the WLL is conservatively based on sheer strength.

Working Load Limit (WLL). There is no universal standard for determining this figure. In safety critical applications and applications where forces are not well defined the safety factor is greater than low risk applications and those where the forces are static and well known. The total number of cycles and corrosion matter. For the purposes of this table I set it at 4:1 based on sheer strength.

Backing Plates. The need depends entirely on the strength of the base material. Obviously, a 1/4-inch bolt passing through a 1/2-inch steel plate does not need a backing plate. It does need a standard (bolting ) washer to provide a smooth bearing surface while torquing it down. However, when fastening to fiberglass, ANY SIZE steel bolt, even combined with an ANSI bolting washer, can exceed the compression strength of fiberglass, no mater how thick. The fiberglass will crumble and crack. I did a bunch of instrumented testing for articles using both thin cored laminates and solid glass, and several simple rules of thumb emerged:

  • Backing plate size: 5 bolt diameters minimum. 7 bolt diameters for thin skinned cores.
  • Backing plate thickness:
    • Stainless Steel--1/2 bolt diameter
    • Aluminum--1/2 bolt diameter. A bolting washer is also required. Not for damp locations; I've seen plates just crumble away in anchor lockers. Fine in a dry cabin.
    • Solid fiberglass--1 bolt diameter, unless bonded directly to the laminate. Then 1/2 bolt diameter. A bolting washer is also required.
    • Wood. Not recommended due to rot and splitting potential.
      • Plywood--2 bolt diameters. A bolting washer is also required.
      • Hard wood--3 bolt diameters. Not recommended, since all of he test samples failed by sudden splitting. A bolting washer is also required.
    • HDPE (Starboard). Not recommended. All samples gradually bowed and cracked under sustained load. Just don't do it.
  • Bond the bolting plate to the substrate if possible to insure good contact. Vital if the surface is very rough or curved. The bonding can be weak material, such as sealant. 
  • Threads. A single steel bolt will hold full tensile strength, even though it will strip before the bolt breaks when turned. The required thichness for the threads to hold full bolt tension varies with the material and how well the threads are cut, but is aproximatly:
    • Steel. 2/3 bolt diameter.
    • Aluminum. 1 bolt diameter in spar alloys.
    • Fiberglass. 1-2 bolt diameters, depending on the density of the lay-up. 1 bolt diameter in G10 and most pre-cast laminates. No standard value for cored laminates, HDPE  (creeps) or wood.
No guess work, just solid engineering principles, though even engineers go up a size when there is something they can't be sure of.




Tuesday, February 7, 2017

Paint Testing in Estuaries

Practical Sailor does a nice job of testing a huge slate of paints in Florida seawater, and occasionally other locations (New England, Australia). But in many estuaries paint selection can be very local, the salinity and pollutant load situation specific. So run your own private test. When you consider what bottom paint costs, this is quite practical. Share the work and expense around the marina, and it's chump change. every marina should do this.

  • Panels: 16" x 48" GRP shower surround material from Home Depot. Since I use this for many other projects around the boat (window covers, wire guards, small fabrications), this is just scrap.
  • Floats: 2" x 60" PVC pipe with the ends capped.
Mask the panel off into rectangles and paint. The number of coats varies, but I would use 2 for 20year paints and 1 for single season paints, since that is how they would be applied. Drill holes every 12 inches and connect the  float tot he panels with 3/16" clothes line or equivalent.  Suspend so that it floats with the tide.








My test panels are actually for an article on cleaning method (one is not cleaned, and others will be cleaned using different sorts of scrubbers), but this is the basic paint testing set-up.

I would not bother in seawater--the Practical Sailor tests should be good--but in the upper Chesapeake Bay, for example, this seems obvious.

Monday, February 6, 2017

Why Bow Sprits on Cruising Catamarans?


I thought about adding one to my PDQ. I really did, after seeing all the pretty ones at the boat show. I had the surplus parts all lined up to build a good one for $20. Then I came to my senses, realized they are nothing more than marketing bollox, and perfect my bridle instead.


I do understand why they exist. My first boat, a souped-up beach cat, had one to carry a chute, and the boat was considerably faster than the wind. Even reaching deep downwind, the apparent wind remained forward of the bow. Jibing through 90 degrees I would actually tack, with the eye of the wind coming from in front of the boat, not from behind. Same with my Stiletto. Fast boats.

A bowsprit increases projected area, allows a larger chute, and most importantly, it provides enough separation between the spinnaker tack and forestay for fast inside jibes (remember, these boats actually tack down wind).

But the math on a cruising cat, even a relatively fast one is very different. The fastest course down wind  moves the apparent wind well aft. Jibes are outside because the apparent wind moves astern when jibing. Thus, a bridle provides more projected area and reduces the chance of running your sheets over mid-jibe. It is also lighter, does not contribute to pitching, and does not pound through waves up wind.

(With a bowsprit that long, the sheets are way out there. Just a little slack, the lazy sheet goes in the water, and a second later it is around the keel. Catamarans are less prone to this because the broad bows catch the sheets.)

For any boat that can't sail above wind speed with the wind at 135 true, bow sprits are pure marketing poop. I've had them and I know the math.

 

This is what you actually need. Lighter, faster, stronger, cheaper. All the good words.

(Excerpt from up-coming book on Cruising Faster.)