BARGE
Does the barge form have any real advantage in a slim hull?

A very good question!
That was the reason i built this last model and tried it.

I would like to say yes to that. I think it works. If one is willing to throw away a lot of speed the Barge-Proa is a viable option. I would not build it for extended bluewater cruising, but for more sheltered sailing it could be a very cost-efficient alternative. I clocked my small model to 2,1 knots average and 3,2 knots peak over a 100 feet of sailing. Not bad for such a simple hull-shape.

I think it handles waves way beyond my expectations.
By building a slim Barge you get a hull that i believe will cope with much worse conditions than a 4:1 L/B mono-hull barge, and it will sail reliably at about 50 degrees upwind, even in breaking waves 3 times higher than the hull.

Why not form the bow in the ‘normal’ way?  As the hull is so slim, it still can be parrallel sided over most of its length.  Basically square profile sharpie with a flat centre section.  No more difficut to make or loss of space.

I think that would make it perform better. I have been thinking about different ways of make it faster and more seaworthy. This was a test. I wanted to test how simple proa one can build without sacrificing to much performance. This is the very bottom of that scale.

Thank you for very thoughtful comments Mark!
Its very appreciated!

Cheers
Johannes

A week ago i finally made up my mind on how to attach the akas to my ama.
I want a low windage, low resistance, low stress and low cost way to do that.
Since my 16 foot ama is a simple square section “log”, its quite easy to build very strong (i hope!) and simple aka-ama connections.

I will use 36 cm wide and 100 cm high plywood pieces i a “V”-shape like the black lines in the first picture below.
They will make very little resistance going through waves, and the shape should make them stiff and strong. The plywood-pieces going up through the hull side will be attached to a bulkhead inside the ama.

I took a picture of my ama. I looks like it will have very low resistance going through the water.

Cheers
Johannes

This is one of 4 pieces that will connect the akas to the ama.

Its not in the right angle yet. I will have to use my beltsander to get it to fit properly,

Cheers
Johannes

I hope this shows how my outrigger will look. It will stand on one of its corners, and you can see the rectangular holes where the plywood-pieces will connect my akas and ama. There will be 4 rectangular holes, but i had to sand the epoxy and fiberglass on the inside to get a good adhesion for the next layer of epoxy.

Cheers
Johannes

Today im to tired to build the aka-ama connection on my 16 feet ama.
Im trying to create a Wharram soft wing sail to my model-proa.
I got some red and very light spinaker-cloth at a good price from Albatross segel.
http://www.albatrossegel.se

Cheers
Johannes

Hi Johannes,

In general I love what you are doing but I think meanwhile you are tangeling with so many options, ideas, resaerch and modelbuilding that you are slowly loosing yourself in between them.

So, what I will write now is not meant to offend you in any way. I just want to be helpful. I have the feeling that, beside having fun making basic proa research, you are working towards a target and I don’t want that you loosing it.

You write “If one is willing to throw away a lot of speed the barge proa is a vital option”.
This is a bad idea in my eyes, if you are offering speed for simplicity in the build you will never be lucky sailing the boat. Just because you saved (lets say) two mounth’s building time, this will spoil your sailing pleasure forever. The parrallel sided barge proa is the worst option to have and even if you can improve the perfomance a little its no option to a fully faired one.

There will come the time when you have to take the blockplane and plane some piece of wood to the shape it needs it. You can’t avoid this in boatbuilding. Remenber, building the hull is just 1/5 of the total building time.

You always point high that your build has to be cost effective, simple and fast. But you are planning with a 1 1/2 inch bottom for a 12 Meter proa, this overscantling is a overkill in wheight, cost, and building time for the following reasons.
- Plywood this thick is expensive ... really expensive!

- Plywood this thick is heavy ... really heavy. This additional wheight must be subtracted from your payload. A boat is designed on a CWL and the wheight of the boat is part of that. So, to have a certain amount of payload that means the boat has too be bigger than it could be with a proper scantling. Bigger boat -> bigger costs in build, equipment and usage. Not to forget building time

-Heavy again ... you will ruin your performance with a too heavy boat. Thats a fact for every vessel and a multihull in particular.  You don’t have to build at the high end of light wheight technology, but give your boat a fair chance of potential. If you load up your model and it sails better that means your are adding payload in the real world.

- No plywood boat can be beached on a rocky beach ... not even in calm conditions ...no way! If you do it, this will ruin the conservation of the bottom on every boat. It must be out of the water afterwards for re-painting. This will cost something ... be sure.

Philosophical and Technical

You are always point that you want to “wind the spiral downwards” to “cheap, simple, efficient and fun solutions” ...

but !!! ....

I don’t know what you want to do with your 12 Meter Proa. It’s a good thing to have a starting point for every design. ok, 12 Meter ist one point, but then?  Do you want to have a certain Accomodation? It seems not. Do you want to have a certain speed potential? It seems not. Do you want to have a safe and seagoing boat? For sure!!! What do you want beside having a 12 Meter boat?

For a “one man building show” a 12 Meter boat is the hell of a big boat, no matter the building method or bulkhead form. The costs for material, epuipment, big sails, maintanance, dockage and so on .... all the man hours to do this job ... all is a fucking lot of it.

Why not start at “your personal human needs” and let the length of the boat be a result of this? Why not make the length of the boat only 2 meter shorter and have the same what you want to have? Even if you are going with a flaired side sharpie hull and so to a little more complicated build, then the amount of money and man hours is much less as with the 12 Meter Bolger_Sharpie. And I’am talking of thousends of Euros and hundreds of man hours.

Sorry, but I had to say this. I hope you are not offended.

With Greetings from rhe North Sea Coast, Michel

Sorry, but I had to say this. I hope you are not offended.

Not at all! It is very appreciated!

Thank you very much for a lengthy and well thought through post about my adventures in Proa-land.
I know there is lots of different experiments and tests in many different directions, but there is so much i want to test.

In general I love what you are doing but I think meanwhile you are tangeling with so many options, ideas, resaerch and modelbuilding that you are slowly loosing yourself in between them.

Since i don’t have the strength to build very much at all, there will always be a lot of time where I am very tired in my body, but not i my head. I think a lot about many different aspects of proas, and there is alwaqys a lot of different things I want to test. I have been sick with CFS the last 14 years or so.

I have pretty much made up my mind about what I want to build. This last Barge-Proa was a test to get some kind of understanding of the very bottom of simple and cheap Proa hulls. “How far down that road can i take it before i get a very slow barge” - kind of experiment.

As i said before: I think the Barge Proa is a viable option if one is ready to throw away a lot of speed. Its the most simple and cheap Proa i can imagine. It is a Barge in that i can carry very heavy loads (considering it is a multihull with some microscopic pretense of speed and sailing-ability). It is the Triloboat of the Pacific Islands, and could probably be used to carry cargo back and forth across the Pacific. I am very impressed by its speed and easy motion, given the extreme simplicity and crudeness. It shows that the Proa has a innate sailing-ability and seaworthiness that far surpasses monohulls and other multihull-layouts.

A couple of pages back I posted the picture below.
That is what I am currently building. It is going to be 24 feet long and two feet wide. Slightly asymmetric, with sharp ends.

Cheers
Johannes

-Heavy again ... you will ruin your performance with a too heavy boat. Thats a fact for every vessel and a multihull in particular.

Its true that a more heavy loaded boat will sail slower given the same sailarea and wind-strength.
To answer your question i must try to explain my view on Proas.

I don’t think “speed” is the main advantage of the Proa. It is the most easily observed factor, and something that we all want more of.
I think there is much more interesting aspects of Proas. They have a very easy motion and a lot of sideways mass inertia - resisting rolling. They have very big deck-space. They are very low stress by design. All this translates to a very safe cruising boat.

Slow <————————————————————> Fast
Heavy <———————————————————> Light
Soft motion <———————————————> Quick and jerky motion
Durable <——————————————————> Fragile
Calm <———————————————————-> Touchy

A Proa is always a balance of all the above properties.
One has to choose what one preferes and needs.
A heavier boat is slower, but is easy to steer and control. things does not happen very fast, one will have time to respond. It will be much easier to live on when sailing as its motion will be slow and calm. It does not react to every little wave and gust..
A very light Proa will react to every wave and gust, it will have a fast and jerky motion and the helmsman will have to be alert all the time. It will be fragile and one needs to take care not to hole the hull when cruising.

Somewhere on that scale is the Proa that will fit what one needs. I tend to drift towards the heavy side, because I like durable heavy-duty work-boats. I want other boats to avoid me. I don’t like being nervouse about weekend-warriors with power-boats and more horsepowers than IQ.

Cheers
Johannes

Speed is relative to what you want. Multihulls have to be faster than mono hulls. Trimarans want to be faster than catamarans and proas want to be faster than both….. Which is fine for beach boats and racers. But cruising ? Above 8-10 becomes uncomfortable and stressfull anyway. The occasional blast in the right conditions will be fun but it won’t be the norm, especially if the wife and kids are along. I agree that there are other advantages to the proa form than purely speed.

Alex and Johannes,

It seems to be funny, but I agree with both of you. In my eyes a proa is a very simple, and low stress (in every way) cruising boat, not a racer.

For the low-powered, low-tech proa, easy motion at sea with low stresses in the structures is that what counts in a proa. Speeds of 10 or 12 knots are the maximum where you can sail comfortable and “the easy way”. A Proa can do this with very small sails, because of the low resistance of there slim one and a half hulls.

But a proa is a multihull and a multihulls nature is that of a light displacement boat. I’am not meaning extreme light displacement building like the racers do it with “carbon vakuum infusion - finite element analysis - squeesing every extra drop of epoxy out of the laminate - way.

I mean a very natural way of designing a light displacement boat, like mother nature does it with her light displacement designs. For example Seagulls, which are able to glide a long way without a single stroke of there wings, thanks to there light weight and flexible and effective design and construction. They are playing and having fun with the wind puffs in a force 7 wind. (I strongly believe to ... why should a seagull fly high in the sky circeling in a storm without any need ...  exept having fun?)
The same has a boat do do with waves coming against when you sail upwind. It has to climb over the waves and therefore a proa has to be light, because the slim hull of a proa has not enough volume to support a heavy load over the waves. Have you ever seen a swan flying in a force 7 wind? No, you have not! A swan cannot fly in disturbed air (like waves), because it’s too heavy and the aerodynamics not flexible enough and therefore zhe swan cannot deal with the windpuffs.

If you will build your proa with too much wheight, due to too heavy scantlings, you will start a number of spirals that will do no good things to your boat

Sailing Motion: Too much wheight -> hulls are deeper in the water -> more resistence -> more bow down tendency downwind because of the higher resistence -> more wavepiercing tendency upwind ->

Performance: Too much wheight -> hulls are deeper in the water ->  more resitance -> more sailarea needed to reach the same speed -> more dangerous ride because of bow down tendency due to higher rig and bigger sail.

Structure: more wheight needs a stronger structure because the forces are higher -> you loose a lot of natural flexibility of the building material -> this causes stress points in the structure needing even more stength to deal with it.

Accomodation: Too much wheight in the hull -> less payload if the displ is the same.

Money: building heavy -> more material needed -> thicker plywood is more expensive than thinner one -> needs much more epoxy to glue the thick stuff together.

Building time and Efford: Believe it or not ... it takes longer to build a heavy structure than a well balanced one.

You still don’t believe me? Then try to sail a Hobie 16 in a strong wind with three persons aboard and you will see that it has no easy motion in the waves, nor it is fast. It will be unconfortable and wet, not to say dangerous, upwind and downwind.

A well designed lightweight boat has not by nature bad habits like quick and jerky motion, bad controllability or stressfull steering. These are design factors which can accour in a heavy boat as in a light one. That has something to do with volume distribution, bulkhead form, balance between CLR and Center of Sailarea, size of rudder and so on.

To stay with your diagramm: take the middle and give your design a little touch to the light side. There you will find the best compromise for a proa. (you will find the seagull there too, exept the really fat ones living near the tourist crowded towns on the swedisch south coast.)

Stupid power boat drivers -> forget it, you can not build a proa to survive a crash with a powerboat, no matter if the structure is overkill or well balanced -> build a steel battlecruiser and open fire early -> only stupid people have no fear.

If you need help with your scantlings for your 7.5 Meter Proa, tell me please. I’am a experienced boatbuilder and able to calculate a basic structure that is well balanced between wheight, safety, building time, building efford and cost. Send me you scetches and i will check it for you.

The same is with your design. I can check your desired volume and compare it with the wheight calculation of the structure. Just to be sure you will not feed a dead horse.

By the way ... I like your various vaka designs very much, even if I favor a different sharpie-style.

Best Regards, Michel

I’m with Michel on this, there’s a path of least resistance that involves pretty common materials (sparingly) and avoiding carbon fiber and the like, though I would use spectra in the rigging.

As far as ease of motion is concerned, there is a significant difference in different configurations of the same design depending on polar moment of inertia. P52 was a completely different boat with crab claw spars up over the bow(s) versus just a central mast with a staysail arrangement, this is one area where “less is more” really holds true.

BTW in 2009, P52 sporting an enormous 48 square foot staysail blew by the whole Texas 200 fleet except for a very well sailed Hobie 14 and Kevins green proa carrying three times as much sail.

cheers,
Skip

Just to have an estimation. What plywood thickness are you planning (or have you bought) for the skins and bulkheads of your vaka and 16 foot ama? On the Photos it looks like 10 or 12 mm.

Thank you for answers!!!

My Ama is built out of cheap and light 7 mm spruce-plywood. The empy hull is so light I can carry it with one hand. With more bulkheads, glassfiber, epoxy, paint and some stringers it will weight about 45 - 50 kg.
It is 475 cm long and has a square section with 30 cm wide sides.

My Vaka will be built out of much heavier 7 mm pine-plywood in the sides and 12 mm plywood in the bottom. I have not decided yet on the deck, but i think it will be a single layer of 4 mm pine-plywood. I will cover the hull with one layer of 300 g/m2 glasfiber and epoxy. More at the chines - since they are high stress and high wear areas.
It is going to be 720 cm long, 60 cm wide and 60 cms high. 25 cm deep continuos rock between the ends. 35 cm high above the waterline. I have (roughly) calculated that it should weight somewhere around 120 kg. We will be 4 poeple sailing on the Proa. I weight a very light and slim 125 kgs. My whole family together weight about 270 kgs, so that is the minimum weight the Proa has to carry when sailing.

As I have said before in this thread: This first Proa is a test to learn how to sail Proas and work out the details. I want to build something that is much larger, but i need to get some experience of sailing Proas first. A 14,4 meter Advanced Sharpie Proa is large enough for some extended cruising for me and my family. It can carry all the food, water and other stuff we need. With a leepod i think a 14,4 meter Advanced Sharpie Proa is large enough for us to live aboard for extended periods of time.

Cheers
Johannes

I wasn’t disagreeing with the weight issue. Love the seagull analogy - was watching them just before coming on here.

Hi Johannes, thanks for the information. I feed freeship with the information and we will see what happens. But it will need some time. Christmas is coming and i have a lot of work to do until then. I think in the middle of january I should have some useful results.

best regards, Michel