Proa Hulls

I follow some of the discussions on the Harryproa Yahoo group and they are always talking about rudder ideas.

Rob Denney showed a bit of interest in my dipping rudder ideas but he is still building his new boat and it will use single fore and aft rudders.

There are still a lot of things to sort with the boats but their modern development is not very mature. I expect there will be many creative solutions.

For me they are the most exiting prospect for light handed cruising.

Rick W

 

Terho - how long befor we get a how to dimension a proa.....? =)

 

Too many variations of theme, only few proanauts...

Most of my early study of proa is here in my obsolete web side:
http://www.planet.fi/~kcad/cpc/Cruising_proa_concepts.htm

 

In my mind there is only one type of boat that fits a proa description. First is the use of the crabclaw sail second is to have only around 30% of total weight to windward. Proas were meant to fly not lumber around with lux accommodations. A very important aspect of proa construction is to keep things flexible. I don't know why it bothers me to see people westernizing proas. I suppose it is in our culture to think we always know better

 

I am trying to find out what came of Richard Atkin 's catamaran concept with the rockerless bottoms...? From the underwater hull form thread from 2008.

Dr Craze- i cant see the polynesians building in cement, even if they ran out of wood..... my brain is also having a problem with flexible cement/concrete.
So - by your thinking, there would be no racing cats or tri's? Oh -and no cement proa's? =)

What happened to Trevlyns proa concept?

 

Every boatbuilder worth his salt should build & sail a Proa, they are the most fun you can have with your clothes on.
The idea of cruising one does not appeal to me but for blasting across the bay as a day boat i cant think of anything better!
last one i built was the Voodoo child & it was 20 odd years ago. He was a right powerful beast at 36ft long.
I figure i ought to build another one before i get too old & i just got offered a beat up grp sectional four oared Rowing shell, it has fast proa written all over it.
My boy who is 14 thinks it will be a great summer holiday project & it will keep him of the computer games so money well spent!

 

Funny you should mention that Alex. There is evidence they were working on earthen fiber composites

I wasnt tryin to ruffle any feathers but without a canting crabclaw rig it just not a proa. They are more like shunting cats. Besides all that the crabclaw was developed just for the proa, why mess with eons of R & D
Why not take off from where they left?

All that said, I am not opposed to a windward cockpit on a very large proa. But still retaining the ability to fly and have the vaka take the load of the entire craft.

Flexibility.....Epoxy is brittle right. when used with fiber it becomes flexible.
.................Cement is brittle yes, when used with steel wire/fiber it becomes flexible, more flexible than fiberglass/epoxy of the same thickness, hense the need for bulkheads and frames on flat sections.

 

Cool.
I like the cc - speaks to me!!
The polynesians worked with what they had and given modern materials, would have used them. Probably would have made even more amazing boats!

 

When you think of it, if you live on a small island with limited resources ie trees a proa gives you the most boats for your buck, assuming some will get lost it spreads the risk. And as Dr craze says why ignore few thousand years or r&d?
The crab claw rig is idealy suited to the craft & lets face it it is cheap to experiment with proas because most bits can be aquired for nowt out of skips.

 

Dr craze - you must post pics.....
Most folks have a problem getting their heads around a proa - making it out of cement will just make it worse.
BUT i like doing things different too so good luck and keep posting on his progress.

 

Alex
Richard was looking to move to the USA from New Zealand. He was going to build or buy a boat when he got there. I do not know how his plans panned out.

Since that time I have built my V14 hull and have been very pleased with it.

The hull is the lowest drag hard chine hull I could achieve for 90kg with 130W input. It outperformed the earlier V11 round chine design primarily because I could build it a little lighter. But also the flat bottom provides a bit of lift at higher speed whereas the earlier V11 hull has a little sinkage.

I am currently working on my V15 hull. It is not much different in hull shape underwater to V14 but I have modified the deck with the aim of reducing the tendency to bury into waves when running downhill. The V14 hull is already better downwind than the V11 hull because the flat bottom at the entry provides a bit of dynamic lift but the deck needs to be able to move upwards easily through a wave. Slender hulls wave pierce so it is important there they have dynamic lift when submerged.

I have attached a photo of the V14 hull, its linesplan and a rendering of the V15 boat I am presently building.

Getting back to the Proa, I have done some performance comparisons for Rob Denney on his latest hull against other more familiar hull shapes. His objective was to make hulls that were easy to build but still performed well. I am looking forward to seeing it in operation.

 

Thanks
I was wondering what his concept was..... cruiser/fast cruiser?
Pro's and cons (compromise!!!) to all designs... but rockerless hulls would enable easy design and build and knowing the cons, it could be worked around?
The gains being speed and simplicity.

 

The lowest drag hull shape will change depending on the available power. Typically with a cat the hulls will be pushed well above hull speed so little rocker ends up being the lowest drag.

With the proa there is more freedom with the hulls because the two hulls serve different purposes.

I have a good understanding of what Rob Denney is doing with his hulls. Both of his have zero rocker but this is more to do with ease of construction than outright performance.

If you are using a flat panel method of construction then there is some benefit for construction to have a bit of rocker. I like a little in the bow for the dynamic lift it provides.

 

I was thinking something like the k-proa main hull - but for a cat.....?
9m length - 7.5m on wl - 6m rockerless mid underhull and similar ends - ie quarter circles with a decent flare for reserve bouyancy. Ht of hull 160(?) - draft 45cm. Wl beam of 70cm - so curved deep v down to a small flat bottom -10cm only....

 

Alex
Getting into the detail of the hull shape without a clear idea of what you want the boat to do means you go around in circle for a long time.

The best is to work out what you would like to do with the boat and then look for what best fits those objectives. Typically the cost of building and ownership have to be factored into the requirements.

The proa that Rob Denney is building should end up costing about AUD20k excluding his labour cost. He ends up with arguably a 50ft ocean capable yacht able to cruise around 12kts without being pressed. It will have limited accommodation for 2 to 3 people.

The performance difference between particular hull shapes of similar overall dimensions is not huge. The main factors are weight and length. Whether it has a bit of rocker or not does not make much difference. A rounded hull is a bit more difficult to make from flat panels compared with a dory style. Their performance is not much different.