New style Harryproa cruiser

[ZULU40]

Originally Posted by valhalla360

Compared to a traditional production catamaran, you are correct, but the premise earlier was you provide the same accomodations but stretch the 40' cat to 60'.

That negates most of your points and would have a similar cost to the proa as extending narrow hulls requires negligible labor and materials, so cost should be similar.

how dare you exclaim my points are negated for what someone else wrote
whistle dixie buddy, im not here for your games

[paulanthony]

Originally Posted by valhalla360

Compared to a traditional production catamaran, you are correct, but the premise earlier was you provide the same accomodations but stretch the 40' cat to 60'.

That negates most of your points and would have a similar cost to the proa as extending narrow hulls requires negligible labor and materials, so cost should be similar.

Also you "photo" appears to be a computer generated image of a small beach proa, so I'm still not buying that the mast will keep her from rolling or that you can swing out the boom and it will flip upright.

The hull index for comparison with a cat is the ww one on the proa. The cat has 2 hulls and the proa has 1.5 or what ever but less than 2 anyway. No matter how much you extend the hulls of the cat it will always be equal to two.

The proa gives board and lodgings equal to a 40 foot cat and a patio garden close to a 60 foot cat all for the cost of 1.5 hulls. Ok.. 1.6 or 1.7 but not 2.

Scale as I have said before is just about matching acting forces to resisting forces. If you can get scale to work you more often than not get an advantage.

Big planes can go upside down as well. We could design fighter Jets as big as jumbo jets if we had our at disposal the needed forces but we don't. However, this proa is within the technologies provision window required.

[lucdekeyser]

Originally Posted by valhalla360

Building in a lower cost country, certainly will cut costs but you get the same benefits regardless of boat design. This is not a benefit of a proa design but of the local labor costs.

There are exceptions but usually there is still a correlation between the skill and the price of labor.

Well, as a matter of fact Denney's new method of assemble ready infusions should lower labor time significantly. A low wage country is thus less of an advantage for this type of proa build.
Ballotta is specialsed in the KSS method which was a new starting point for Denney's approach.

[lucdekeyser]

Originally Posted by ZULU40

....
Secondly, the layout of the hulls, where unlike a trimaran the larger ama is more resistant to sticking into a wave, stalling, crashing, and pitchpoling. As it is still an ama its beam/length ratio is more conducive to speed, likewise its greater length adds to boatspeed and with a smoother more comfortable ride. If caught aback it has the volume of the main hull to fight off the capsize force due to its buoyancy.
....

In addition the masts are located in the "larger ama" opening up the "main hull" for more useful space.

[lucdekeyser]

In low wind speed ranges the difference in windage between stayed and unstayed masts may not be that significant. But what about surviving hurricane speed winds? Difference in dragging anchor(s)?

[paulanthony]

Originally Posted by lucdekeyser

In addition the masts are located in the "larger ama" opening up the "main hull" for more useful space.

Hey... Who ever said pole dancing was not a useful allocation of space..

[ZULU40]

Originally Posted by lucdekeyser

In low wind speed ranges the difference in windage between stayed and unstayed masts may not be that significant. But what about surviving hurricane speed winds? Difference in dragging anchor(s)?

Sail area is effectively a square area, vs drag a function of a cube root. So both scale and velocity favours a larger design or greater force, and this is explains why models are only a qualative representation of performance, not quantative.

The same relationship is true of all other non static forces, bigger is always better. Until we reach the point where the strength of the materials we have begins to be challenged and things begin to break.

[ZULU40]

Originally Posted by lucdekeyser

In addition the masts are located in the "larger ama" opening up the "main hull" for more useful space.

it follows then, that in 'modelling' proa attributes in earlier smaller versions, using body weight and short flying ama's made more sense. But in these sizes the effects of scale make the sail bearing ama the better proposition with an accommodation hull on the other side.

Seems to me to be a theoretically bulletproof proposition, which is always a good start

[lucdekeyser]

Originally Posted by ZULU40

Sail area is effectively a square area, vs drag a function of a cube root. So both scale and velocity favours a larger design or greater force, and this is explains why models are only a qualative representation of performance, not quantative.

The same relationship is true of all other non static forces, bigger is always better. Until we reach the point where the strength of the materials we have begins to be challenged and things begin to break.

Maybe I should rephrase my question: my boat is moored in the bay. A hurricane will pass by. I have tied down the boat as good as can be. Can I worry less with unstayed masts?

[downunder]

Originally Posted by valhalla360

Building in a lower cost country, certainly will cut costs but you get the same benefits regardless of boat design. This is not a benefit of a proa design but of the local labor costs.

There are exceptions but usually there is still a correlation between the skill and the price of labor.

The point is that Ballotta has the skills and knowledge of infusion techniques with the addittional advantage of lower labour costs.

Being close to the States many South americans have been educated in the States and requlatly update their knowledge in the States.

I would not hesitate to build a vessel there.

I think labour costs and the construction costs of this design will put it close to the cost of a KSS built 39ft cat.

[44'cruisingcat]

Not good enough. It's supposed to cost the same as a 30 foot cat.

[paulanthony]

Originally Posted by lucdekeyser

Maybe I should rephrase my question: my boat is moored in the bay. A hurricane will pass by. I have tied down the boat as good as can be. Can I worry less with unstayed masts?

You wont have any shrouds vibrating and trying to rip themselves out.

[ZULU40]

Originally Posted by lucdekeyser

Maybe I should rephrase my question: my boat is moored in the bay. A hurricane will pass by. I have tied down the boat as good as can be. Can I worry less with unstayed masts?

yes it should be fine,
a stayless rig, whether or not it is round or an aero profile, either will, or can be rotated to a point known as zero lift. The only effect on the rig is drag around the spars. It is therefore in balance, is steady and more consistent.

Having a larger profile than an alloy mast might seem to some to make it a higher contributor. But experience has it, that wire and rod rigging has drag effects beyond its size. Its that 'bigger is better' thing all over again

A free standing rig will transmit its forces through the comparatively massive mast step, and it will resist the gust forces better by deflecting/bending its tops.

A rig with stays will produce more drag, and unless the spar section is round it will produce an amount of lift (As most do) which will contribute to a driving force. So it has a contribution of lift and drag vectors which will have some different perhaps indeterminate effects. In any event it will feature more drag which means more forces to deal with, often with seemingly more minor components.

Inconveniently a stayed rig also has more points of failure, stainless fittings with hairline cracks, poorly swaged multi-core wire, corrosion and casting defects, chainplate problems, all have a contribution.

A rig with stays is designed to stay tight and rigid and is permanently stressed all the time, and a lot of the forces will be distributed through the hardware, so the integrity of the whole is an important feature in keeping the rig aloft where it belongs.

The thing will sing like a steel guitar at a country and western convention in a hurricane.

If there is a problem and some component fails, the rig is at risk from coming down. That doesnt mean certain failure, but it does mean the rig is compromised and at risk. If something else fails due to the now added loads on it, due to its 'in tension design' there is no question about it you are in trouble.

In either type, I would be surprised if they could be blown to failure without a sail up, but in any event the free standing rig is going to be more reliable and in the better situation as it will produce less force to dislodge your ground tackle or securing warps.



.

[lucdekeyser]

Originally Posted by 44'cruisingcat

Not good enough. It's supposed to cost the same as a 30 foot cat.

What is the price fork for such a cat in your experience?

[lucdekeyser]

Originally Posted by ZULU40

yes it should be fine,
a stayless rig, whether or not it is round or an aero profile, either will, or can be rotated to a point known as zero lift. The only effect on the rig is drag around the spars. It is therefore in balance, is steady and more consistent.

Having a larger profile than an alloy mast might seem to some to make it a higher contributor. But experience has it, that wire and rod rigging has drag effects beyond its size. Its that 'bigger is better' thing all over again

A free standing rig will transmit its forces through the comparatively massive mast step, and it will resist the gust forces better by deflecting/bending its tops.

A rig with stays will produce more drag, and unless the spar section is round it will produce an amount of lift (As most do) which will contribute to a driving force. So it has a contribution of lift and drag vectors which will have some different perhaps indeterminate effects. In any event it will feature more drag which means more forces to deal with, often with seemingly more minor components.

Inconveniently a stayed rig also has more points of failure, stainless fittings with hairline cracks, poorly swaged multi-core wire, corrosion and casting defects, chainplate problems, all have a contribution.

A rig with stays is designed to stay tight and rigid and is permanently stressed all the time, and a lot of the forces will be distributed through the hardware, so the integrity of the whole is an important feature in keeping the rig aloft where it belongs.

The thing will sing like a steel guitar at a country and western convention in a hurricane.

If there is a problem and some component fails, the rig is at risk from coming down. That doesnt mean certain failure, but it does mean the rig is compromised and at risk. If something else fails due to the now added loads on it, due to its 'in tension design' there is no question about it you are in trouble.

In either type, I would be surprised if they could be blown to failure without a sail up, but in any event the free standing rig is going to be more reliable and in the better situation as it will produce less force to dislodge your ground tackle or securing warps.
.

Wow. Thank you for this full reasoning. Particularly the "less force to dislodge" I find very important. I wonder how much I would value such an assurance. I am somewhat biased just now as last week a nightly storm in the Med. set a mono lose crashing it on the rocks and three people drowned.