Tag Archives: mastodon

Junk Rig

I know, I know! It’s been almost three weeks since I posted anything. Ithere have been many things happening, but nothing much to do with drawing or with my boat so I thought I would spare you the drivel. I am editing my book. 100,000 words to edit, am about halfway through and needing (so far) to completely rewrite about 3-4000 of them. The rest are looking pretty well chosen (thank goodness!).

In boat news I got my copy of Hasler and McLeod’s Practical Junk Rig. Basically THE definitive tome on all things to do with Chinese style rigs. They are notoriously easy to sail, cheap to make and require minimum of stresses on both the hull and the sail. Perfect, no?

Thing is that my boat plans do not come with a junk option so I had to design one. It took all day and about eleven slightly different sails to arrive at the perfect configuration. I initially thought that you just plonk a siutable piece of cloth on a stick and call it a sail. Sadly it is about a hundred times more complicated and involves several things including your LWL, CLR, CE, rake and displacement (ballast in my case). You can see I am deliberately being cryptic.

Basically it is very important that the ‘average’ centre of pressure from the wind on the sail is more or less directly above the centre of lateral resistance of the hull. If not then your boat will not easily sail in a straight line, sacrificing speed and handling. If the point is too high above the boat then you will easily capsize, too low and you miss the swiftest winds. The height of your mast depends on the depth of your hull, so a little boat can’t have a tall mast because the mast will fall off and/or my boat will tip over in a gust. Finally the mast has to be the right proportions fore and aft of the mast to allow space for the rigging, and the right height above the boat to not hit you or trail in the water.

Anyway brace the contents of your various sphincters for the finished article!



I know…amazing…

Anyway, the important thing is I have plenty of sail (15 sq ft) and my CE is above my CLR, and my mast is a decent 19/20 ft. It should go like a scolded cat even in light breeze but I will have to reef early or risk taking a dip.

I was tempted by many things, extra masts, funky sail shapes, but I am going to keep it simple, this time.

With trepedation….

…I quietly announce the ‘pretty much’ final design for my boat.

Mastodon 21′ by Daniel Powell Conti

Everything was well and good with my previous final design, so as I mentioned before I was doing some 3D modelling to put up a picture for your entertainment. It was then that I realised a horrible design flaw.

It looked shit.

I am not going to spend thousands of pounds on a boat that doesn’t look awesome. I realised too late that my final design necessity was a cool looking boat. The problem was that the accomodation hull was too tall and fat. It looked like a supermodel and her retarded sister trussed together and passed off as a princess. To put it nicely.

So this is the newer, sleeker design. Hopefully it will actually look like one boat instead of two random ones bolted together. Click on the picture for higher resolution.


The vitalstastics

Lee hull (with the mast)
Waterline: 21′
Beam at waterline: 1′
Displacement: 68kg

Windward hull (accomodation)
Waterline: 21′
Beam at waterline: 2′
Displacement: 136kg

Centre to centre beam: 10′

Hull displacement: approx 204kg
Draft: 2″

This is a ‘weight to windward’ design of pacific proa, giving greater stability than a more conventional ‘flying’ design. I will talk a little about the important changes. The crossbeams, the hulls length, the mast step, and the accomodation.

I have four crossbeams instead of the more conventional two, generally something more often seen on catamaran. This may be a case of structural overbuilding but I want to feel safe in this thing. I feel that with a hull made of 4mm marine ply I could use a little extra support for the extremeties of the boat wich would otherwise stick 7′ free from any lateral support. The four beams will have strong internal support built into the bulkhead below as well as longitudinal support from one crossbeam to another. There are other advantages too. I am now able to build the rudders closer to the end of the hull, increasing their leverage. I will also be able to string trampoline mesh between the outer and inner crossbeams, doubling the available deck area.

I have increased the length of the hulls as well as making the ama and vaka (main and outrigger) the same length. This was after I saw a similar design called ‘Ping Pong’ by Terho Halme. It has equal length hulls and sails just fine. It solves several problems for me. The problem I was having with the ‘weight to windward’ design was not having enough space or displacement in the windward accomodation hull. Having a 21′ windward hull solves it nicely. I have not gone back on my ‘easy to build’ principle either. By sacrificing a bit of inside space the hull can be made to be 2′ high with an additional 1′ cabin top. This still leaves space for two to sleep, head to head instead of next to each other. The space will allow two to sit and face each other with space to cook or play chess inbetween when they are not sleeping. However generally, while sailing, two crew members would not be taking sleeping shifts at the same time. If moored or at anchor there is space on the 14 sq ft deck to pitch a tent.

I have chosen to step the mast to the crossbeams rather than into a hull. I want a mostly freestanding mast for ease of manufacture. As I said in a previous post, stepping the mast inside the hull raises problems that I can just avoid. Furthermore, having the mast on the crossbeams allows me to move it, repair it and generally be able to access any part of it without having to mess with an integral part of the boats structure. It also makes it easier to earth the mast incase of a thunder storm, I can just trail some copper wire in the sea.

The unloaded displacement is 204kg for 2″ draft. Day tripping with three or four people would be around the maximum displacement of 520kg which would give a draft of about 6″. Adequate for smooth seas.

The only real complexities are the angled, three chine hulls. I feel they are quite necessary to avoid slamming into waves at high speeds so they stay. Because the boat has no rocker so it is a manageable level of complexity.

I have a boat designed. It is simple yet elegant and will look sweet as when decked out in bright red paint. Now I just have to think of the…cost…
14 x (4mm x 1.2 x 2.4) marine ply = GBP 252
60kg epoxy = GBP 624
27m sq of CSM fibreglass 300gsm = GBP 24
40m sq of 300gsm woven glass fabric = GBP 52
Paint plus antifouling = GBP 100-200

total cost of hull = GBP 1052

Then all I have is estimates for the other costs.
Workshop and tool hire GBP 800 (?)
Aluminium poles GBP 80 (?)
Sail GBP 200 (?)
Rope GBP 100 (?)

Estimated bild time: 240 hours

Assuming my estimates are sound the minimum cost will be around GBP 2232. Knowing from the outset that there is a snowballs chance in hell of sticking to the minimum budget I am giving myself a budget of GBP 3000 to complete the project.

That seems like a lot of money so I thought of other stuff I could buy for three grand that would help me enjoy travelling around New Zealand.
An old car and 6 months of petrol and insurance.
An old monohull sailboat.
A 14′ racing catamaran.
A cheap Armani suit. (Wait, that wouldn’t help at all)

So to hell with common sense!


Should probably stop…

…announcing new boat designs. I have gone through four designs so far, each time thinking I was done. Well now I am actually done. Pretty much.

Why am I done now instead of being done the last few times? It’s a little to do with optimisation and a lot to do with finding an awesome boat!

Last time I posted I mentioned something called a Harryproa. The interesting thing about this type is the accomodation is situated in the windward hull and the rig is situated in the lee hull. The result of this is greater stability due to the distribution of sail force and weight of passengers. However all the designs I saw were too small and had too small a payload. Until I saw ‘Sidecar’ by Doug Haines, a modified Elementarry Harryproa. I based my design around it, and this is where the optimisation came in. I needed a greater payload available, but I also didn’t want to waste wood making something fat and slow (like my other designs).

The hulls are 20’x2’x2′ for the lee and 14’x3’x4′ for the windward. The 20′ hull can be made out of 4 sheets of oversized ply with very little waste. The 14′ hull will take a few more regular sized boards, but the accomodation section has been designed with space and ease of building in mind. The whole thing can be stitched-and-glued and there is no complex geometry. I should have about 300-500kg max payload without having to sacrifice much in the way of speed.

Then I designed the crossbeam fastenings, the crossbeam supports and the internal bulkheads. There will be space to sleep two and a 2′ x 2′ x 7′ store in the 14′ hull. The 20′ will have a 2′ x 2′ x 6′ store for light objects. The remaing hull space can be filled with structural foam to make it theoretically unsinkable (touch wood).

All I need to do is design the mast to be stepped into the crossbeams like on ‘Madness’, but I need to see whether that is a good idea. So I’m going to bother the nice people on the boatdesignforums.

Also just got the call yesterday, my school is hosting OFSTED for the next two days…wish me luck!

The Mastodon

Philosophy aside, lets get into the actual specifics of the boat. I have spent about a year and a half refining my ideas and looking at various configurations.
My requirements are:
1. Needs to be small enough to be sailed solo, but large enough to accomodate two people.
2. Must be large enough for extended travel away from civilisation, between two weeks and a month.
3. Must be small enough that I can drag it up a beach in an emergency.
4. Must have space to store a kayak.
5. Must be simple to build.
6. Should have ample deck space for relaxing on sunny days.

It would be a thousand times easier to just buy a boat instead of make one, and I’m sure I could get one that satisfies most of my needs to an adequate degree for a reasonable price. Decent boats can go for as little as 2000GBP. (my stupid foreign keyboard doesn’t have a pound sign) But there are some problems with that. Primarily because these boats, while in good repair will almost certainly be 30 to 40 years old. That pretty much guarantees that they will need regular maintenance from the go. A noob like me, with no sailing or woodworking experience is not going to have a chance of doing it properly. However, if I have made the entire thing, then I will know exactly where and what the problem is should one arise.
Thats the logical consideration.
Emotionally speaking, I can scarcely imagine the satisfaction of cruising around in a boat you made from scratch, exactly to your specifications, no compromise.

For those wondering why I think I am capable of building and sailing a boat with no experience, well, for better or for worse, I am not familiar with self doubt. I have done extensive research and I am confident this project falls well within my limitations.

At the bottom of this post I have added links to some websites that have steered me in helpful directions and provided inspiration. The full list would be ten times as long if I could remember all the webpages I have visited since the thought first popped into my head. Veterans like Sven Yrvind and Matt Layden are exactly the people you want to be taking advice from when it comes to sailing small boats.

After lots of reading, the state of the art for small boats is widely accepted to be Matt Layden’s ‘Paradox’, and Sven Yrvind’s ‘Yrvind’ (links below). These boats are 13′ 10″ and 15′ respectively. They are mono-hull and shallow draft. The ‘Paradox’ being the easiest to build because there are plans on sale.

However neither of these designs could fulfil all of my requirements. Specifically they were too small to comfortably house two people and I could not store a kayak on either. A little more research and Quenet Yann (boat-et-koad) stepped up to the plate. A man who has built and tested an 18′ version of the shallow draft boats invented by Matt Layden. I looked at his design, did some cost calculations and was stoked for a while, thinking that I had found my design. After a while however doubts started to set in. Would it be right for my needs? Would the effort of building be offset by the advantages of having it tailored to my needs?
I started losing enthusiasm for the whole project and thought I might as well just buy one for cheap and find ways around the limitations.

For those nautically challenged, shallow draft (the amount of boat under the water) is necessary for me for several reasons. Firstly it allows me to avoid many submerged obstacles, secondly it is necessary for beaching, thirdly, flat bottomed craft are much easier to build.

My ‘buy and make do’ opinion changed completely when I saw this!

Boom! The 31′ ‘Madness’ Designed by John Harris. What a beast. Much too big and expensive for me of course, but it sent the cogs turning once more.

This type of boat is a Proa, a very old micronesian type. The basic point is that the smaller of the two hulls, known as the Ama, is used instead of a keel and ballast to offset the sideways force on the sails. What that essentially means is that the boat can be lighter and carry more sail than a similarly sized mono-hull.

The immediate benefits for me are:
1. Plenty of storage space in the Ama.
2. Can have a shallow draft.
3. No heeling (leaning sideways).
4. Plenty of ‘deck’ space for crusing comfortably in the sun.
5. Plenty of main hull space for sleeping.
6. Can keep my kayak onboard.

Long story short, I have roughed out a design for an 18′ Pacific Proa, ‘Mastodon’ by Daniel Powell Conti.

This is the basic design that I made 3D with a bit of free google software. I did a pretty poor job of replicating the details of the actual design, but it will do to get across my idea. It was my first time using the software and took about an hour. The next model will be much more accurate.


More on that in my next post, its lunch time now.

For anyone interested here are some links that I found extremely helpful.