Brittany Ports

[snowleopard]

I'm always a bit sceptical of designer's theories. Some say you should have bow and stern different shapes, e.g. V bow, flat stern, to prevent hobby-horsing yet the Twins is pretty well symmetrical fore and aft.

I spoke to someone who was building a tri from the same design as me. He built a scale model and tried to capsize it in wind and waves. He said the only way to tip it was stalling on the face of a wave and sliding backwards when the stern of the lee float dug in and it turned over along the diagonal. Prout told me their tapered sterns prevented digging in, unlike the common forward-sloping transoms.

I don't understand how less beam could prevent pitchpoling though.

 

[boatmike]

Well I hadn't meant to start a treatise on multihull design but having worked with many designers I think there are several clearly evident facts. Firstly the longer the boat is in relation to its beam the less likely it is to pitchpole. This is doubly so when one considers a cat going downwind with pressure on the sails trying to bury the lee bow. Most blue water ocean going cats won't ever lift a hull on a reach, they tend to trip over the lee bow and pitchpole in extreme conditions and this is what most racing sailors of multihulls fear most. There are three things that can be done to counter this.
1. Increase the WL length in relation to the beam.
2. Increase the reserve bouyancy in the bows (i.e. the bouyant area normally above the WL when at rest)
3. Decrease the reserve bouyancy in the stern quarters reducing the lift of a following sea.
Unfortunately all three of these things tend to be detremental to sheer speed in one way or another.
The Prout designs are not known for being fast but they are highly regarded for their sea keeping qualities which is basically why I am a fan.
The symmetrical hull form is directly descended from the polynesian cats and proas. The basic reason for the sea keeping qualities of these frail little boats that took Asians all the way to New Zealand was their inability to be tipped end to end in following seas. Just like those a Prout like mine has a hull that is the same form aft of the centreline as forward of it, and has less tendancy to lift its stern to a following sea. In fact its failing is not the hull form but the solid bridgedeck above it that is a clear failing of all modern designs from an extreme seakeeping point of view. In fact in really extreme conditions you do get very wet in the cockpit but the stern does not lift sufficiently to bury the bows. That's not just theory, I have survived, not a hurricane, but a very severe atlantic storm in one streaming a series drogue and know it's true. I truly would not have wanted to be in any other boat of equal size then. The later Prouts succumbed to market pressure and fitted wider transoms in order to increase the volume of the aft cabins and adopted a bow design that has very little reserve bouyancy to increase the waterline length. It had nothing to do with seakeeping and I like them not. You can build a boat for speed, you can build a boat for sea survival in extreme conditions and you can build a boat to impress the buyers at boat shows how much room you have on board. You can't do all three. It's a compromise. Always. That's why I keep saying there is no such thing as a perfect boat..... The compromises the designer of your boat made were different from the designer of mine. That's why they are different. I envy you your speed and I am not saying for one moment that your boat is unseaworthy, but it's built to do a different job than mine and has different faults because of it.
In design one should not strive for perfection in every area, it's an impossible task. Know your remit and design to suit the market requirements. But recognise the limitations of the finished product......
Enough!
Lets go sailing and enjoy!

 

[brianhumber]

On springs people sail over the retaining dam wall, last I was there a dirty great beamy cat was tied up, was not till we saw how high the water reached over the wall we realised how he had got in!!.

B

 

[snowleopard]

Yes, I've seen it done. One would need to be pretty confident of ones tidal calculations.

 

[boatmike]

Er Yes! Or it could indeed be a long stay..... /forums/images/graemlins/blush.gif

 

[MacMan]

We were in Erquy a couple of years ago - not in our cat then but unless it has changed I would go back in our little Prout. At the time we took up a spare mooring buoy but in settled conditions two or three cats and bilge keelers just dried out on the beach. Not much protection though as you aren't behind the breakwater there but OK in settled conditions or offshore winds. Water by portage at the HM office and a nice set of restaurants. Decent supermarket in town - overall a pleasant little place an nicely of the "beaten track".

All of the "wall" was taken by fishing boats and so I think would be a no-no.

Did "Sables des Pins" last- we towed the boat out with me on holding a line off the stern and SWMBO with a like in the bow ! All the Frenchies thought we were mental - but back then we only drew 9 inches with everything up. Not recommended !

Brehat recommended if you are going that far - dry out right up the beach out the way.

 

[boatmike]

Thanks for that MacMan we might well give Erquy a try then!

 

[MacMan]

I should say it's off the beaten track for yachties - there will be hundreds of locals on the beach - but no-one seemed to mind last time if you stay at the sea end of the beach - just inside the breakwater but clear of the harbour "entrance" - but be prepared for lots of bucket and spade types walking about - I would still recommend a vist though.

Cheers, mark