'Atlantic Six'

What does your design brief look like? What are your requirements for the boat? What do you want to use it for? What does your budget look like?
User avatar
Rob Zabukovec
Posts: 555
Joined: 27 Aug 2014, 21:20

Re: 'Atlantic Six'

Post by Rob Zabukovec » 01 Dec 2017, 02:50

Marco,

You probably,have already, but just in case, you should check out Matt Layden's designs and ideas for micro,cruisers, you might find some inspiration there:

https://aiki.pbworks.com/w/page/1594232 ... inerunners

Also, Bernd Kohler who,has quite a track record in this field, including CATAPROA!! (Registered design!)

Rob.
User avatar
Manik
Site Admin
Posts: 373
Joined: 27 Aug 2014, 15:41

Re: 'Atlantic Six'

Post by Manik » 04 Dec 2017, 22:10

Thanks for the tip! :)

Design for the 6m atlantic proa is going quite well. I'm still a bit stumped over how to get it right side up in the event of a full inversion though. Counter-acting a 60kg+ ama with a 2.5m lever (plus the weight * lever of the beams) requires quite a bit of leverage on my end, and there's a bit of damping from the mast and sails to overcome as well. The buoyancy of the mast doesn't help much initially, even with a masthead float, because its pointing straight down. From a full inversion (180° heel) you have to get the first 50° or so (down to 120-130° of heel) before the mast and masthead float take over and bring the boat up to lying on its side (~95° of heel).

To get those initial 2000 Nm of righting moment plus a margin for damping, and for me to be well above the water, I'd need something like a 3 - 4m long righting-pole, which seems impractical to say the least, especially in a chop...
Attachments
rm_vs_heel_masthead_float.png
Simplified model of RM in a backwinding (i.e. pacific mode). Masses are point masses, the hulls are cylindrical, the mast is modeled as a cylinder. The mast set on the edge of the vaka. The mast (and masthead float) hit the water at about 95°, causing the spike in the RM curve.
top.jpg
two_righting_poles.JPG
"Man's mind and spirit grow with the space in which they are allowed to operate." - Krafft A. Ehricke, rocket pioneer
RobinBennett
Posts: 129
Joined: 08 Feb 2015, 22:36

Re: 'Atlantic Six'

Post by RobinBennett » 05 Dec 2017, 10:36

How about an A-frame, made from couple of spinnaker poles, clipped together at the top and to the edge of your rack? Use that to hoist a large bag of seawater, and then pull it towards the ama. It's a lot more complex than a righting pole, but should work for any size boat.

Or, could you reduce the weight of the ama to the point where a righting pole is feasable? My Wa'apa was easy to right, just pushing down on the windward rack while I was swimming.
User avatar
Rob Zabukovec
Posts: 555
Joined: 27 Aug 2014, 21:20

Re: 'Atlantic Six'

Post by Rob Zabukovec » 05 Dec 2017, 21:20

Marco,

I am not sure how you are going to manage all this in wet weather gear and life jacket or highly buoyant dry suit in very windy & wavey conditions without suffering hypothermia and exhaustion or worse..... Try swimming around with all your gear on sometime.

It isn't clear from the information how your mast is supported, but instead of extra poles/frames plus buckets and drogues etc (where do you store it all on a 6m Proa for easy and instant use without it all being a PITA?... Plus the extra weight).... why not just have a canting mast set up and let the mast float you already have do the work? If you set it up right, canting can help to avoid the situation in the first place? And if the mast is "dumped" before you capsize, it is already in the right place should you get turtled.

Have a look at John Pizzey's work over in the old Proafile.

Rob
User avatar
tdem
Posts: 146
Joined: 31 Aug 2014, 22:08

Re: 'Atlantic Six'

Post by tdem » 06 Dec 2017, 07:26

I agree a canting mast seems like the only elegant solution.

One question I have is - how likely is the boat to end up fully inverted, with the mast still intact?
The most important thing is to keep the most important thing the most important thing.- Donald Coduto
User avatar
cpcanoesailor
Posts: 230
Joined: 03 Sep 2014, 13:35

Re: 'Atlantic Six'

Post by cpcanoesailor » 07 Dec 2017, 15:36

A canting mast seems good, if you can easily adjust the stays when the boat is turtled and you are floating alongside. As long as the water is deeper than your mast, you probably don't have to worry about it breaking.

I also like the idea of being able to slide the ama closer to the vaka to reduce the righting moment necessary to flip the proa upright. This should be easy if you use tubes for akas. Just afix the ama to slightly larger tubes that can slide over the beams.

Whatever system you devise, it should be simple and quick to deploy, since you will want to get out of the water ASAP.
Post Reply