Proa Hulls

[rwatson]

Originally Posted by ThomD

I'm interested in the idea of the level keel hull on a trimaran. ....
A level keel would have the advantage of allowing a little more volume in a folded plywood hull, and if it suffered in tacking, would that really be a problem just hauling it to the azores. At the very worst one might have to back the jib, which still may not leave a tri losing a tacking battle with a boat that shunts, and in any case is not what this boat would be about.

...

have a look at your average tri or cat hull, and you will find there is very little rocker at the stern where it is widest anyway.

At the front, (or either end on a proa) losing the rocker will add about 3 cubic inches of totally unusable space, and give you all the tacking problems you want.

It makes no sense to me to lose maneuvarability for the amount of space you could recover by adding an inch width all down the hull.

Not tacking easily doesnt seem a big deal until you have to get out of irons in front of the PortArlington Ferry bearing down on you at 17 knots with 200 tonnes of cars on board.

[Alex.A]

Isn't that what the motor/s are for?

[rwatson]

Originally Posted by Alex.A

Isn't that what the motor/s are for?

yes - but I had run out of petrol about ten minutes earlier, and the wind was very light.

A kind couta-boat towed us out of harms way. :-)

Seriously - you have to have a really good reason to compromise a boats sailing ability - engines are so bloody fraught!

Last year, went out on a 60 ft square rigger for an afternoon. We ended up having to drop the pick while Captain Sarah went below to clean out the injectors after the engine failed to fire.

[Alex.A]

Ok - 2 engines and a sculling oar too!!!

[cavalier mk2]

I know rocker for proas isn't currently trendy but there are advantages to a boat that goes over some of the waves instead of through them, drier being one of them. On traditional Polynesian craft the guy that got to sit in front and block the waves from hitting the chief was considered as a having a position of honor. It is no wonder those boats had rocker, if nothing else it made the honor more bearable. Rick's earlier comments on having to back off pedaling in certain conditions made me think a little rocker might be good. While a proa doesn't have to tack (I think they should for more options) being able to maneuver easily in crowded or narrow waters should be a consideration unless you are just trade wind sailing. All boats don't need to be buoy racers but it is good to be able to miss the buoys.

[Alex.A]

I like a tacking proa- OOPS -outrigger .....
Reserve bouyancy to pull up as you go thru?
Gonna test it and see.... as for the dude upfront - i wont need one and if i do i'll pay him well! Hopefully he'll be honoured?

[rwatson]

Originally Posted by cavalier mk2

I know rocker for proas isn't currently trendy but there are advantages to a boat that goes over some of the waves instead of through them, drier being one of them. .

I think you will find that its not so much the rocker that decides if you go through the waves or over, but more the width and profile of the forward section. You can have plenty of rocker, but with a very narrow bow and forward section will ensure you go through the rough stuff.

The rocker tends to affect tracking and maneauverability more than anything else ( oh, and of course hitting rocks and beaches etc)

[cavalier mk2]

Not to mention hitting drift! Plumb or reverse bows like the race boats can also be a chance when cruising as they are going to take an impact instead of sledding over. Rocker does have an effect but with a double ender it probably doesn't need much. On the Wharram Pahis which have a straight keel it was observed that any pitching tended to move the CLR more than the Tikis. I suppose there would be less effect with a 2 masted rig than a central one.

[Alex.A]

Proa's in the small range and tri's are just stabilized monohulls.....
Take a monohull - cant the keel even further to the side and make it bouyant instead of stuffing it full of lead? Oh no!!
So - if you could just swing it over and tack - it'd really be a monohull
Here-in lies my problem - while i like the idea,it doesn't work for me - i want to get the use of/from both hulls. The mid deck is too small too....
Only once they get big do you get 2 hulls - but by then they are both more complex and more expensive - to build and park (and maintain etc).
so (in smaller sizes) the only true multi(useable)hull is a cat!!!
Ok - so there is the speed gain - but for cruising, what is that worth - similar sized cat will go fast enough... for a racer tho it makes sense.
Of course you could make it a sshunting cat thingamabob but then everyone poo-poo's it as some bastardised nonsense .
A tacking outrigger or asymetrically hulled cat has the good tack bad tack thing - so doesn't work either...
SO - i think, in the medium small range, i am stuck with a cat......
And yes - curved bows(and bows - sorry sterns) and a ketch rig.
My craziness is over. The basics are in place. Now for the details........
One more thing - should i have posted in pacific/atlantic thread