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Peter Haydon's Anima

This version was saved 15 years ago View current version     Page history
Saved by Peter Haydon
on March 15, 2009 at 8:18:24 pm
 

How this page is organised

It's a progress from top to bottom - latest progress and information is at the bottom of the page.

 

There's a fair bit of text, so skim the headings to find the interesting bits!

 

Introduction

I've been working on this project about four years. I spent most of that time thinking up with and discarding designs. As of the end of February 2009, it is about two months away from launching.

 

Anima -  the executive summary

Anima is a tacking double-outrigger with low-volume amas. The main hull (vaka) is a 2nd-hand David Pyne-designed fibreglass Tasman Twin tandem sea kayak - a large volume design. The amas are glass/epoxy over foam. The akas are telescopic aluminium tube.

 

Specs:

LOA: 6.46 m (21.2 ft)

BOA: 3.8 m (12.5 ft)

Ama length: 3.6 m (11.8 ft)

Ama volume: about 65 litres each (about 150 lbs flotation submerged, less ama weight of around 10 pounds) - don't know the percentage in traditional tri ama volume terms but it's probably down around 15%!

Sail area: 38 sq ft - (eventually, a second mast will likely be added with another sail of undetermined size.)

Akas: Al tubing - 50mm OD, 2mm wall/44mm OD 1.6mm wall. Max free span about 1.5 m.

 

I did a rough assembly the other day for the first time, temporarily held together with straps. This gives you some idea of what my finished craft will look like - note the flat wineglass transom:

 

 

 

Where I live

I live on the south-west coast of Victoria, Australia,on the well-known tourist route the Great Ocean Road.

I live near the lighthouse:

 

 

This stretch of coast can have fair-sized large surf - 2 metres is common. There is little or no protected water, and out to sea is Bass Strait or the Southern Ocean - both scary bits of water. Some of the coast is sandy beach, but a lot of it is rocky. Weather can change quickly and strong winds of 30 - 40 knots are not uncommon. There are a few lakes and navigable rivers within a 2-hour drive, but the coast is my main destination.

I want to be able to sail off this coast in any reasonable conditions - up to 20 knots of wind and 1.5 metre swell. I want to be able to cruise and get ashore safely in conditions far worse than that.

 

The original spec

I have always wanted a small single-handed cruising boat. I've raced dinghies extensively, and sailed keelboats, but I like a little cruising vessel.

There are no harbours and few boat ramps in my part of the world.

 

This was my original spec:

 

  • Sailing capability
  • One person handling, two person capacity.
  • Can be transported to beaches without boat ramps.
  • Handles well in surf and open ocean.
  • Reasonably fast.
  • Snorkelling platform.

 

(Maybe a developed sea kayak - sit-on, maybe with removable outriggers (maybe outriggers have the keel/daggerboard), unstayed mast and smallish single sail. All sailing gear can be stowed in hull while on board.)

 

...added to...

Needless to say, I added to this spec over the years. Items now include:

 

  • Fast setup/pulldown.
  • Lots of redundancy (and forgiving failure modes) for better safety and self-rescue.
  • Moderate cost.
  • Decent length (for surf management)
  • Not rotomoulded polyethylene (hard to modify) - so, wood or fibreglass.
  • Not sit-on (at least, some sit-in-ability.)
  • Possibility of sleeping/shelter onboard.

 

My personal rules for this project

I am allowed to make mistakes, even expensive ones - it's a prototype!

 

Some other design principles

Make as few permanent alterations to the kayak hull as possible. So far, it's down to drilling about 20 small holes (mostly in the deck) and one big one for the mast - maybe a few little ones for sail rigging. The idea is that I can tranfer the outriggers/sail rig to another vaka in future if required.

Oh, and try not to put holes/pins in aluminium tubing, especially in a stress situation. It's OK but it is asking for wear and stress concentration.

 

 

History

 

Early designs

I initially had little source of comparison for what I was doing. At various stages, had I had the money or the opportunity, I would have bought a CLC tri, an Easyrider kayak with sailing kit, a Windrider, a BSD BOSS kayak sail rig with inflatable amas, and just about any of Steve Isaac's (aka Watertirbe Chief) old rigs (I found out about his really interesting new Tridarka Raider design only recently - might still build it!).

 

But, living in Australia, you couldn't even get CLC kits until recently. I was scared of epoxy resin (I'm allergic to a few things). I'm a very modestly skilled woodworker, though I'm improving.

 

I bought a kayak cheaply - it was a Current Designs Storm single of rotomoulded polyethylene. Two years and hundreds of design sketches later, I traded it in for a fibreglass boat. I learned that it is really hard to bond things to polyethylene, and that I really wanted a larger two-person craft.

 

I bought a Australian David Payne design called the Tasman Twin. I had seen some of David's wooden kayak designs and I loved his lines. This hull, at least ten years old, was enormous - 6.5 metres long high volume hull with big bows.

 

At the kayak shop, they called it "the ship" - it dwarfed every other kayak there:

 

 

 

It also had a flat transom stern with a wineglass shape. This is very unusual in a kayak but perfect for retrofitting a chunky, dinghy-style removable rudder. I really didn't like the idea of those top-mounted kayak rudders for sailing - far too much leverage on the top bracket.

 

 

Designing and building the amas

The amas were the first things I designed and built. They were designed around my original Current Designs hull, but tranferred OK to the Tasman Twin (except the huge rear hatch is a little obstructed - not as big a problem as you might think).

 

I used a program called BearBoat Pro to design the amas. BearBoat Pro is very easy to use, and works on minimising wetted area for the design paramenters you choose.

 

My design parameters for the ama were:

  • Low volume so I could sink them and right the rig in case I turned turtle.
  • Slippery for most angles so water turbulence couldn't get too much "grab".
  • Up-turned bow to reduce nose-diving (I really should have used high volume in the bows instead)
  • Minimum drag for design length.

 

Beause I knew little about wood-work and had designed my amas freely without regard to what you can do with a flat plane of ply, I decided to shape them out of foam like a surf board. But surfboard foam is insanely expensive. Much research yielded a fine-grain, high density styrene foam, very shapable, which could be supplied in sizes to order.

 

I cut out a central vertical stringer of marine ply which looked like the profile of the ama hull. With the help of a friend with a big bandsaw, I cut my foam blocks to vertical and horizontal profiles (so they looked the right shape from side on and from above).

 

Just made one teeny mistake. Each profile was a half hull, so I had to cut four for the amas - two right, two left.

 

Except I cut four left sides, and my amas are NOT fore-and aft symmetrical!

 

We got around this by simply "flattening" the curved side of two pieces - pulling them in to bond to the central stringer on the "wrong" side. This worked amazingly well, so much so that you can no longer tell which was the "wrong" side on the finished ama.

 

During this process I had some professional help. After bonding each half to the central stringer, we bonded a thick-walled piece of PVC tube vertically into the ama for each aka mounting point, into a cutout in the stringer so it became structurally part of the stringer. This created a potential bury of 140mm at the rear mounting point and 200 mm at the front mounting point.

I shaped each ama like a surf board. From my design program, I had printed out half-sections of the hull for every 20 cm, and every 10 cm at each end where the shape changed more rapidly. I glued the printouts to thin MDF, then jigsawed each half-section out. I marked the hulls for length, then pressed the female MDF half-sections into the foam along each side.

 

Here is the ama in the process of shaping, with the half-sections laid along the top at their measured positions:

 

 

I power-planed off the pressure marks in the foam, then did it again. After days of this messy procedure (I'm still finding bits of styrofoam in my bedroom) I had a good shape, which I longboarded to a pretty nice shape ready for glassing (I had this done professionally as I was still scared of epoxy at this stage).

 

After 2x4oz glassing, with further reinforcement around the mounting points and between the mounting points as a step-upon, I had light strong amas.

 

A couple of ama design decisions caused me much head-scratching later on:

  • In the hope of a more stable movement under load, I maximised the distance between the aka attachment points on the ama - 1.9 metres (just over 6 feet).
  • For various reasons (mounting in a composite foam construction, force analysis etc) I made the aka attachment points vertical cylinders (to accept a tube).

 

The akas

The akas caused more design headaches than any other part of the boat.

 

I had all sorts of trouble arranging the 1.9 m gap between mount points at the ama to fit with the kayak hulls I used - at one stage I was contemplating Al tube precision bent in two different axes just to make it all fit together! I found out it is mightily hard (= expensive) to bend thin-wall aluminium, especially if you are looking for tolerances of less than a degree.

I didn't even discover methods of creating akas by lamination of thin strips of wood until too late in the design process, though I did consider steam-bent wood at one stage

 

I eventually settled on straight, telescopic akas of aluminium, attached to the akas by composite elbows (of which more later).

 

The outer aka tube is 50mm OD,  2mm wall thickness, temper 6060 T5 (this is not ideal by the way - I would rather have 6061 T6 but at the time of purchase was considering bending curves into the akas - the harder alloy doesn't bend very well. I later changed this design but when you have spend many dollars on something that will do the job - you use it!)

The inner aka tube is 44mm OD, 1.6mm wall thickness, temper 6061 T6.

When the tube is fully extended to design beam there is an overlap of around 450mm of inner and outer tube. I intend to have a thin layer of glass (c. 0.5mm) bonded to the inner, covering this overlap. This is to decrease the clearance, decrease stress concentration, slightly increase wall strength and remove the risk of Al-Al binding. However, I can continually reduce beam to 2.5 m, and sail with that reduced beam. I expect to do beam changes on land because it would be tricky to do this while actually on anything but the calmest water.

 

Aka mounts on main hull

The aka mounts are of 25mm marine ply bolted vertically through the deck of the sea kayak. One of the trickiest aspects of this was trying to work out where vertical was on a flowing curved hull design. I eventually just found horizontal (by floating the main hull and using a level) then decided that vertical was perpendicular to that!

 

Another slightly tricky issue was shaping the wood to fit he hull (both stringer on the inside and mount on the outside). I will eventually use gap-filling epoxy to bed the mount (using releasing agent on the hull).

 

 

 

The mounts bolt through to stringers which spread the load underneath the deck (yes, the kayak is  inverted in this photo!).

 

 

Each mount has a large lashing-point (big chunk of oregon) bonded to it extending slightly beyond the hull, and bolted horizontally through the hull.

 

 

 

I use big chunky SS/polyester ratchet tie-downs ( the strap is 25mm wide) to lash akas to mounts (not shown above):

 

 

The aka mounts would work fine with conventional lashings, rubber inner tubes or what have you. I'm using tie-downs in the hope that they are quicker to rig. They use them for OC canoe outriggers in Queensland sometimes.

 

Elbow pieces

So I have straight horizontal akas, and vertical mounts in the amas. I need a transition.

 

The elbow pieces create a transition between the horizontal akas and the vertical holes in the amas. They cover an angle of 96 degrees (to allow for 6 degrees of heel at nominal loads) with a straight of about 250 mm on either side of the angle - this straight is buried either in the ama or in the aka.

 

The elbows are made of hardwood dowel (cut in 14 degree wedges and end-bonded to create the angle). Here's one in the jig I used:

 

 

The wooden core becomes a former for glass tape wrapped helically around to a thickness of about 2mm - the idea is that most of the load gets carried by the glass, not the dowel:

 

 

The elbows are of two different sizes (two for the larger diameter aka, two for the smaller). They just fit inside the aka tube. 

 

Here is one in position - you can only see the actual elbow as the straights are buried in ama and aka. The blue elastic strap is not part of the final rig!

 

 

 

Holding it all together

I wanted to avoid using pins through the Al tubing to hold it all in place. I considered cleats and lashings, but eventually decided to use big chunky SS hose clamps at each connection point.

 

All the connection points (ama/elbow, elbow/aka, inner aka/outer aka) have an "outer" of aluminium tube, slit at the end so the clamp can bear. At each clamping point, the outer is axially cut at 6 evenly spaced points around the diameter of the tube. The cuts alternate between 40mm and 50mm, and have slight widening holes drilled in the inner end of the cut for stress reduction and to reduce corrosion points.

I really wanted to get cam clamps like those on bike seat posts, but couldn't find any in the right diameters. My clamps are screwdriver/wrench tightened, which is a minor disadvantage.

 

Because of all the clamping points (3 on each aka, 2 on each ama) there is an insane amount of adjustability - I may replace the four aka/elbow clamps with permanent bonds.

In normal use I will only adjust the two outer aka/inner aka clamps for telescoping of the akas for trailering, maybe narrow passages such as small rivers, and

berthing.

 

Rudder

This is pretty conventional - the profile is loosely inspired by Steve Isaac's Watertribe rudder. It has about 15% - 20%  of the area forward of the pivot point to reduce the chance of stalling. Currently it is a flat 4mm Al (5083) blade, but it has cheeks bonded to the blade stock to bring it out to 20mm. This is so I can make a wood/glass foil rudder some idle winter and still use the same housing.

 

Rudder blade with blade cheeks prior to bonding:

 

 

 

The rudder stock is not yet made but here is a diagram - you can see it has a dinghy-style pintle/gudgeon setup. I did a heap of design pics like this in CorelDRAW - not formal drafting, but they helped me to visualise things, and enabled me to print wood and glass fabric cutout diagrams.

 

 

 

Aside: bonding ply to aluminium

It is hard to expoy things to aluminium, because the oxide layer forms so fast (and the oxide layer is not strong enough to bond to). As soon as you sand aluminium, the oxide layer has formed - it takes literally seconds. There are etching kits sold to counter this, using muriatic acid I think, but I found another really cool and simple method on the net. I have tested it, and it works really well - used it on my blade stock cheeks.

 

Basically, you apply epoxy to the unprepared aluminium surface, then sand through it (like wet sanding) with coarse paper (40 - 60). The liquid epoxy stops the oxygen from reaching the surface of the sanded aluminium, thus no oxide layer is formed - you are bonding directly to toothed aluminium metal. The oxide suspended in the epoxy after sanding does no harm to the bond strength. You can then  happily bond the aluminium to sanded ply, or whatever else takes your fancy.

 

Had to share that with you - it appeals to my nerdy sense of cool and elegance!

 

Leeboard - moulding fun for everyone

I bought a sail rig from Mark Balogh of Balogh Sail Designs - he makes very good quality gear. It cost an arm and a leg, especially with the Aussie dollar exchange rate, but I wanted something bullet-proof to keep me company on the lonely ocean. It included a beautifully made leeboard which attached to an aka.

 

To keep things simple, I wanted to attach the leeboard to my aka, but it was a different diameter to the one Mark's leeboard fittings were designed for - I had bigger amas and consequently larger diamter tubing. So I had to make my own leeboard clutch. I was getting so cocky by now I decided to build my own moulded part completely in glass and epoxy

 

Here's the diagram. The thick white thing is the thickness of the leeboard and the existing hole in it. The metal ring is an aluminium ring washer, which I made out of the same 4mm plate I used for the rudder.

 

 

Here's the mould, carved from ply - bit of a rough hack:

 

 

The first moulding came out really well (below left). The second was a mess (below left). I've done a lot of work on the mould which will hopefully improve its replacement.

 

 

 

 

 

Sail plan

 

Fairly early in the project, I decided to buy a sail, mast and centreboard from Mark Balogh of Balogh Sail Designs. Mark specialises in making all-points sail rigs for kayaks. His gear has a reputation for being bullet-proof, which suited me for solo sailing on an inhospitable coast. His sails have a zip reefing system. I bought the 38 sq ft sail (his largest) which reefs down to about 30 sq ft and 20 sq ft.

 

Before buying these sails, I also picked up a couple of small used windsurfer sails and a fibreglass windsurfer mast, all for about US$60. Again, these were pretty small - about 25 - 30 sq ft each.

 

I like small sails. I don't want to go really fast (although this Tandem Twin hull pushes really easily) - I'm a cruiser by nature. Also, in ocean conditions, I don't necessarily want to be hiking out all the time, and we often get pretty solid winds. I also want the sails to be unstayed, and furthermore I don't have that much bury compared with, say, a Dierking proa.

 

So I have rough sketches of a couple of tentative sailplans with three possible mast positions. Here's the single-sail version:

 

 

The Balogh sail is on an aluminium mast which breaks down into 4 sections for easy stowage. In this mid-mast position, there is about 35 cm of bury, which I hope will be enough. Also, the mast is attached to the aka, which gives lateral support and thus another few cm of effective bury. The only problem with this rig is that people will point and say, "Ha ha, look at the tiny little sail." Unfortunately I don't expect the boat to point very well with this rig - I hope to tack through about 110 degrees.

 

 

And here is the double-sail version:

 

 

As far as I can tell the centre of effort is not that different between the single- and double-sail versions. I'm hoping the centre of resistance is not too far aft of the centreboard, which is attached to the aka.

 

The forward mast position has about 37 cm of bury which I think is probably OK - it is reinforced at that point, and it's more than most kayaks offer.

 

The rear mast position has about 30 cm of bury - not sure if I'll need some kind of mast partner here. Unfortunately it can't be attached directly to the rear aka because that would put it through a hatch. It still penetrates a storage compartment, but will be in a glassed-in tube so the compartment stays sealed.

 

The windsurfer sail is on a cut-down fireglass mast, which I plan to reinforce at deck point with a tapering external FG reinforcement running about 30 cm either side of the deck,. Alternatively I might use the approx 1 metre I cut off the bottom of the mast as a stub mast - not quite sure how this would work.

 

 

 

 

 

 

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