Tuesday, November 29, 2011


Now that virtually everything, including rigging details, has crystallized (if not writ in stone--that won't happen even after the boat's launch), it's time for some acknowledgements.  In designing and building my boat, I drew inspiration from a very wide range of sources, some of which were anonymous, some which I have forgotten.  The amateur boatbuilding community is very generous with ideas and advice, and inspiration and emulation is widespread and natural—after all, it’s been said that imitation is the sincerest form of flattery.  I did not copy anything specific in detail, I just used well-known practices (and quite a few improvisations) to achieve what I wanted, based on the many inspirations.  All calculations and decisions, all errors and corrections, and even some small innovations are mine.
Even so, I would like to gratefully acknowledge the following people/businesses for inspirations and influences by subject (a specific boat design is listed as appropriate). 

  • General lapstrake hull design: John Welsford, François Vivier, B&B Yacht Designs (Lapwing)
  • Broad lapstrake hull design: Iain Oughtred (Caledonia Yawl)
  • Cat ketch basics: B&B Yacht Design
  • All manner of stuff on traditional sails, helm balancing, marlinspike skills, etc.: David Nichols
  • Sprit booms: B&B Yacht Designs, David Nichols
  • Lug sails: David Nichols, Jim Michalak
  • Standing lug/sprit boom combo: John Welsford (Houdini)
  • Sheet arrangements: B&B Yacht Designs
  • Halyard arrangements: François Vivier, Michael Storer (Goat Island Skiff), David Nichols, Jim Michalak
  • Broadseaming: Todd Bradshaw
You probably already know that I did not buy any plans for this boatbuilding effort.  That was obviously not for reasons of economy (even though some people think I am cheap): buying plans would have saved me countless hours of planning, calculating and improvising.  As I explained in my two earliest posts, I did not find a design that fit all my needs, and I greatly enjoyed the whole challenge of designing from scratch and building on the fly by the seat of my pants.  For people who are less crazy than me, I would heartily recommend the plans and/or books of the fine naval architects listed above.

Thursday, November 24, 2011

Sail Plan

When I started this blog I said that my plan was for a cat ketch, with a balanced lug fore (main) sail, and a standing lug sail with a sprit boom at the mizzen (aft) mast.

Upon reflection, I decided that it would be simpler and better to have the same type of sail both fore and aft.  I like several things about sprit booms, and B&B Yacht Designs expresses them eloquently.  One of the best is that, when the boom goes about, at worst you get slapped by a bit of canvas, instead of a length of wood or metal which can knock you senseless and/or overboard.  

The second reason was a balanced helm.  The placement of the mizzen mast partner (at the rowing thwart, just forward of frame 5) and the centerboard (between frames 3 and 5) was largely dictated by the boat’s basic design (the placement of the boat’s frames), so I had to design the sail plan around them.  I did, but at first I neglected to take into account the effect of the skeg and rudder on the Center of Lateral Resistance (CLR).  Adding these to the calculations moves the CLR aft, which means that the original sail plan would have resulted in a serious lee helm.  A lee helm can be dangerous: the moment you let go of the tiller, the boat turns away from the wind and it’s off to the races.  It’s best to have a slight weather helm, where the boat will naturally turn into the wind in an emergency and stop dead in its tracks.  I therefore had to move the Center of Effort (COE) aft too.  

To accomplish this, first I moved the mainmast position aft to just forward of the foremost bulkhead, about 22 inches from the bow.  This led to a reduction in the mainsail size, which also moves the COE aft.  Then I changed the sail type to the standing lug/sprit boom combination, which added to the effect, since the tack of this sail is further aft than a balanced lug’s.  Finally, I opted for a smaller main mast/sail and a larger mizzen mast/sail.

Taking all that into account, the sail plan now looks as you see it below.  It took me a while to make good on my promise for a full hand-drawn sketch, but better to be late and accurate than early and wrong.  The centerboard did not fit on a regular sheet of paper at an inch-to-millimeter scale, so it's truncated.  COE marks the combined center of effort.

The mainsail has an 84-inch (2134 mm) foot and a 96-inch (2438 mm) yard.  The sail area is 58.5 square feet (5.44 m2).  The mast will be 142 inches (3607 mm) long and 2 ¼ inches (57 mm) in diameter at the partners (click on "spars" label on right to learn more).  That’s a short mast, which has many virtues: it fits easily inside the boat (with the fore locker sliding door open), it’s short enough to be unstayed (no standing rigging!), it has a lower COE and center of gravity (which makes the boat more stable), it’s cheap to make and simple to work with. The clew of the sail will have about 6 inches (152 mm) of clearance forward of the mizzen mast, and 36 inches (914 mm) of clearance from the seats, leaving plenty of room to avoid the swinging boom-end with no ducking for most people.

The mizzen sail’s dimensions are proportional to the mainsails, and about 93% the size.  Thus we have a foot of 78 inches, an 89-inch yard, and an area of 49.5 square feet (4.6 m2).  The boom-end at the clew will be a little aft of the transom.  Clearance from the seats is the same as with the mainsail.  Mast length is 139 inches (3531 mm), and diameter the same as the main’s.  Given the dimensions of the two masts, it is possible to make both with a total of nine 8-foot boards.  That assumes no errors: hope springs eternal. 

You may wonder why the two masts do not conform to the 93% ratio.  First of all, the mainmast step is a full 5 inches further above the baseline than the mizzen one, so the total length can be correspondingly less.  Secondly, what matters for the proportions is not total mast length, but the length between the tack and the yard, which is only 97 inches in the mainmast, and consequently 90 inches in the mizzen. 

Under the final sail plan, the COE is well aft of the middle of the lowered centerboard, which should make for a balanced helm (fingers crossed).  The total sail area will be 108 sf (10 m2), which should make the boat reasonably zippy.  

Balanced helm, zippiness and how close and how well the boat will sail upwind all remain to be seen, and I may need to make more adjustments after the boat’s launch.  I am hoping for 90-degree tacks but will settle for 100.  Heck, I won’t be racing against any tall-aluminum-masted affairs with complicated standing rigging, genoas, fancy boom-vangs, jibsheet capstans and the rest.  My whole boat design and building effort is based on a principled rebellion against high-tech complexity, uniformity and the racing rules that spawned them.  In any case, if other traditional sail aficionados are to be believed, my Aerie should be able to leave behind any comparable Bermuda-rigged boat on a beam or broad reach, where lug sails excel.

By now almost all of the hull work is done.  As you can see, though, there’s plenty more, so keep reading 176inches!


Sunday, November 13, 2011


Today I did what I promised myself would be the last thing in the garage for the season:  I put on the oak rubrails.  They are 3/4 inch by 2 inch oak, and it was hard to bend them around the curves of the sheer, along both the y (around the decks) and z (up and down) axis.  I had to cut kerfs on the inside in the forward part, drill recessed pilot holes, and get help from my wife.  Still, I had to stop in the middle and go buy a couple of large, strong clamps to hold things in place amidships.  Also managed to strip a couple of screws, which is par for the course.  There are places where there are tiny gaps between the rubrail and the sheer, but nothing which that last refuge of the desperate boatbuilder, filleting compound, will not fix.  I still have to do that and fill the screw holes, but the table saw, shop vac and tools and materials will be moving into the basement so I can work on the spars and other things (see the previous post). 

So, as usual, keep checking 176inches.


Wednesday, November 9, 2011

Decks, splashguards and spar planning

With winter approaching, I have been winding down the work on the boat (as opposed to spars, oars, centerboard and rudder, which I will make in the basement, and sails, which I will sew in the house), and on Sunday I cleaned up the garage for the season.  I was amazed how many small or narrow, useless scraps of plywood I had left over, but that's what you get with all the curved and irregular pieces.

Meanwhile, the weather in Ohio is holding, and yesterday we had almost 70 degrees (over 20 Celsius).  Not for much longer, that's for sure.  But since it's reasonably mild still, I first put on the side decks and sanded their edges and those of the foredeck smooth.  Then I marked and cut the splash guards.  The forward one is nailed and glued on the main bulkhead, protrudes 1.5 inch over the foredeck, and fits around the upper rail of the forward sliding door.  The side splash guards start forward at 1.5 inches over the side decks and end at about 3/4 inch at the transom.  I glued and nailed them onto the side deck vertical boards.  If you look closely at the picture, the splash guards are a little irregular and will require a little planing/sanding to smooth the curves.  This comes from cutting them free-hand with a circular saw.  I could have invested in a scroll saw but did not see the need beyond this one-off job.  I intend to put on the oak rubrails at the sheer this week.

If my luck with the weather holds I might do some finishing on the decks.  Finishing benches and inside bottom will probably wait for the spring, when I complete the flooring.  I am looking forward to taking a bit of a break from this frantic race with time and climate.  The auxiliary (winter) work will start soon enough.  Speaking of that, some words about what is planned:

Last weekend I bought the lumber for masts, yards and oars.  Good, clear, knot-free lumber is surprisingly expensive, but using stock white pine studs like I did in the past is a real pain, with all the knots and voids, and not very strong.  I designed the masts based on calculations from free software (Mast by Robert Tyrrell).  They will be laminated from three layers of 1X3 clear pine (3/4 by 2.5 inch in actual measurements).  The mainmast will be about 12 ft (3.66 metres) and the mizzen 11 ft 7 in (3.53 metres).  Both will easily fit inside the boat.  The diameter will be 2 1/4 inches (57 mm) at the partners, with some tapering above and below.  With all the scarfing, lamination, trimming, tapering, cutting the corners into octagonal cross-section, final rounding and finishing, the masts will be a lot of work.  Yards, by contrast, will be easy: two layers of 1x2 inch pine (3/4 by 1.5 inch in actual measurements) glued together, and some rounding of the corners.  As for the sprit booms, I already have one from a previous rig, and the second will be the same: a piece of closet rod with an epoxy and varnish finish.  Then of course I will have to get all the beautiful and perplexing chandlery of rigging: blocks, cleats, line, etc. for halyards, snotters, sheets and more.  I am a thrifty guy, and the boat will have traditional, unstayed, sturdy, simple rigging, so high-strength, high-performance, expensive stuff will not be necessary.  I have taught myself splicing, servicing and other marlinspike skills which will come in handy.  There will be plenty of posts about all that, of course.

The oar shafts will be made of two layers of 1X2 poplar stock, and the blades will be clear pine edge-glued to the shaft and its extension in the middle.  There will be quite a bit of rounding and tapering, planing and sanding.  I will also leather the place where the oars meet the bronze oarlocks, and add what is called a button to each oar so it doesn't slide out.  I will talk about the sails another time.

So keep an eye out for more adventures on 176inches.