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Anke and I are building our next boat, and writing about it at ABargeInTheMaking.blogspot.com. Access to the net comes and goes, so I'll be writing in fits and spurts.

Please feel free to browse the archives, leave comments where you will and write, and I'll respond as I can.

Fair winds!

Dave and Anke
triloboats swirl gmail daughter com

Saturday, March 7, 2020

Ama AHA! Quick and Dirty Approach to a Small Multihull

Insurance for a narrow hull

My escape is to just get in a boat and disappear on the water.

-- Carl Hiaasen


Ama AHA! Quick and Dirty Approach to a Small Multihull

Let's say we can get our hands on a canoe, dory, kayak or other small craft. We enjoy paddling around, but are thinking a sail would really be kinda fun. But we're cheap.

What might we do?

To sail, we'll need some basic things:
  • Stability
  • Sail and rig
  • Lateral Resistance
  • Steering

Stability

I'll presume our little boat is narrow and tippy. We may get some stability from ballast, but that's awkward and complicates everything. So we look for ways to increase form stability.

The arrangement shown above looks quick and dirty to me.
Three features excite me...

A) The simple, bent ama shape... even with blunt ends, most of the time the immersed shape will be hydrodynamic. These look to be PVC which can be momentarily softened and permanently shaped with moderate heat (hot air gun, hair dryer or holding over a heat source). 

Small trees for cross beams and curved drift logs from the base of select trees would work as well, and can be quickly shaped with an axe.

B) The over and under arrangement with the cross beams... the aft strut could easily be eliminated with more curvature or an arced cross beam.

C) The whole affair can be lashed up... all we need is some line and a few holes bored below the sheer rail at mounting points.

This simplifies a scheme Anke and I have been wanting to try with our dory as well sas a planned, half-open beach cruiser, in which we can go into proa or tri mode using beachcombed crossbeams and akas. Using this approach, so long as the hull has xbeam mounting points, the whole thing can be lashed up with minimal carpentry. 
When done with a (windward) sailing stretch, we can disassemble and row/downwind sail off leaving the components in our wake. 

Of course, this works especially well in an area like the Cascadian Passage. Won't be so easy, in a lot of places where the beachcombing is limited.

Sail and Rig

A sail is a simple thing. Any flat fabric of the right size will do. Problem is, flat sails work (if you allow them to twist) but they are not powerful. A little shaping goes a long way. The trick is to get the right amount and proportion of extra fabric toward the middle of the sail.

Q&D fabrics include tarps of most any kind, house-wrap, awning material, sheets and so on.
Q&D solutions for shaping a sail:
  • Cut one or more perimeters with some curvature (curved away from the sail's center). When straightened along a spar or under tension, the extra fabric goes toward the middle.

  • Seize around one or more corners. This pinches the tied corner, tightens the perimeter and radiating cloth from the corner toward the middle.

  • Selectively dart the edges. This is a little fancier, and takes some knowledge or experience. But good in the tool kit.

Masts can be made from small diameter trees (chances are your guess at about right will be about right). If straight ones aren't available, consider a balanced lug rig, which sets well on a crooked mast.

They need at least two points of support - step (or heel stop) and partners with as wide a spread as you can manage (can always add stays). Since we're talking small boats, these needn't be too beefy. U-shaped pipe hangers have worked well for us as partners and stop. If the hull is thin, we'll add a small plate of plywood under the mast heel (bottom end of mast).

If you decide to go bigger, scale up as need be.
You'll need sheets to haul the sail in and let it out. A halyard is optional (sail may be fixed to mast). Some rigs will have their own extras. Consider rigs that keep the extras down (sorry Junk Rig!).

PDRacers are a racing platform with no specified rig. In short, you can see all manner of practical (and impractical) rigs for small boats here.


Lateral Resistance

The harder the chine (angle or radius between sides and bottom), the more lateral resistance from the hull. If we want to sail to windward, we'll need to add more.

Simplest means I know of is an Off-CenterBoard. Most just call them leeboards, but they work on both tacks. Of these, among the simplest is Jim Michalak's pivoting leeboard.


Steering

The simplest solution is no rudder. Balancing sail adjusted with sheets against lateral resistance adjusted by weight shifts (LR moves for and aft with crew weight). This is why sailboards need none.

An oar over the side or stern is next. A well placed pin or stern notch, respectively, help keep it in place and reduce fatigue.

A light kick-up rudder (bearing plate style is simplest of these) can be easily hung on strap hinges, and doesn't require mounting or dis-mounting when leaving or approaching shore.


*****

So there you have it. A bag of Q&D approaches that can have you sailing day after tomorrow! 
Don't forget flotation and life-jackets!






...

Full disclosure: COVID-19 has me on alert. If you may need to travel by water, it's a good time to be getting a boat in hand. Go small, go simple, get ready!

4 comments:

  1. Nice quick-n-dirty tips applicable to the next size hull up in case of having to bail awhile during the worst of the pandemic.

    Another super fast and cheap sail construction option: stake out a perimeter bolt rope in your preferred shape of a chinese lugsail. With battens-yard (we used pvc pipe with wood inserts) tied into it. Throw a one piece tarp on top, trim the edges 6" too much all around, have a sew to boltrope party with a few buds. Trim the rough edges. Bang in some grommets for the batten attachments (industrial zip ties work well).

    Did this for a 435 sqr. ft. lugsail using a 20X40 tarp and worked well!! Of course so much easier if smaller. Duckworks has a article from a guy who did this and even sewed in belly into each panel easily.

    ReplyDelete
    Replies
    1. Hi Roberto,

      Great method.

      An easy (Chinese) way to get belly in your system is to press down between battens about 1/3 from the luff (stones are often used) before trimming and sewing.

      Less stable fabrics (like cotton) work great with this type of sail.

      Dave Z

      Delete
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