Bolger Advanced Sharpie Proa, now with Videos.
Strange looking video from underneath
There is some strange artifact from uploading it to youtube..
A very calm evening at lake Mjörn. I test my proa. Just fool around with it. Its very easy to push through the water. I didnt even feel the wind, but the proa did something like two knots upwind anyway. It feels totaly unreal. My girlfriend is very impressed with the proa. She said she definitly wants to sail at an easy 5 knots in almost no wind under a blue sky in the pacific, someday! Watch the dolfins and the waves. How could i not build the proa now?!?! 😉 This is the most amount of fun i have had with my pants on for a very long time! There is something very special and magical with proas!
Johannes.
Hi Johannes,
thanks very much for putting your thoughts, pictures and videos up on the forum here.
I’m wondering if a dory hull wouldn’t be better than a square one for a proa, though. A square hull has the advantage of resisting heel straight away and for a long time against increasing heeling force. This is all a good thing for a sharpie as they are said to sail best (fastest) upright. But then they can capsize to 90* very quickly (not a good thing) and then resist further capsize from there which is a good thing for a mono with ballast. It has the potential to self right from there.
But a proa benefits from some small degree of heel that allows the ama to skim or become slightly airbourne so a dory hull that allowed that would be an advantage i would think. Also the rising resistance to heel that a flared topside would provide would be an advantage as it would give some feedback regarding potential capsize. The flared topside would be more likely to allow the proa to be self righting, too, given it doesn’t have anywhere near the same amount of ballast as a mono has to overcome the stability of the square hull now at 90* to the water. Or were you looking to some other device to guard against capsize such as a leepod or safety ama?
This is only a test, but if i build a large proa it will have a leepod. I think a leepod is an absolutly essential feature on a proa designed for bluewatersailing. Russell Brown is my main inspiration, and i try to learn as much as possible from him and his proas. As far as i know, no else comes close to his amount of bluewatercruising in a proa, exept for polynesians and micronesians of yesterday.
The square sharpie type of hull is as you say, very fast when upright. On a proa the hull will be almost uppright most of the time. It doesnt have very much righting force at less heel than 10 - 15 degrees, so it shouldnt be any problem skimming the ama. The hull will have a lot of righting force when leaning more than 20 - 30 degrees, and as the leepod start tuching the water, the righting force will become very large, resisting capsize. I think its very important that the leepod is designed to make the vaka surf sideways down a wave. If cought sideways by a large breaking wave, its very important that the hull can slip sideways without tripping on anything. I think a sharpie like hull with very shallow draft, will slip sideways much more easy.
Regards.
Johannes.
I borrowed this picture from Sven Yrvinds blog Sven Yrvind and i hope he does’nt mind. A great blog by the way!
The righting force starts to come into play above say something like 10 - 15 degrees of heel. A proa is much more slender, so i hope it won’t be a problem.
Regards.
Johannes.
Dynamic lift to resist pitchpooling
Im sorry if spam this forum with lots of videos. Just tell me if its to much, and i will stop.
I made this video to show the dynamic lift, a flat bottom hull with some rocker, develops at speed.
I think this is very important to resist pitchpooling in heavy seas. I imagine surfing down a large wave in the pacific, scared shitless and tired, hour after hour as the gale howles outside the boat. I need very good and strong rudders with lots of control, and i need the boat to keep the bow out of the waves, to resist pitchpoling. I think it works realy well so far. I will be makeing a lot more tests in the coming weeks. Im allready planing and drawing my next proa. I think i will make it larger, so i can attach GoPro-cameras to it, without effecting the balance and sailing-trim.
Johannes.
You post as many comments, pictures and videos as you want, Johannes! This is very interesting.
Have you seen “Seaweed”?
http://outriggersailingcanoes.blogspot.com.au/search?q=seaweed
I came across this quote, Johannes, on the handling of the AS29 -
“This is the smallest sail area I have gone down to when caught offshore in 30 knts+ and 2.5 - 3m. breaking seas. In hindsight, a 3rd reef would have given better control in these conditions but as it was I reached down to Sydney Harbour and she smoothly rode the seas like a cork. When picked up by the wave the weather chine lifts before the stability of the hard lee chine takes effect. She levels out to surf down the wave with the full bow not tending to dive.”
Quoted from here-
http://members.fortunecity.com/booraleaboats/AS29Handling.html
Im sorry if spam this forum with lots of videos. Just tell me if its to much, and i will stop.
I am always glad to get some data from people who do something.
Is there a stream or fast-flowing river nearby? That would give a cheap tow tank, in which you can test whether you have enough dynamic lift when you tow from the mast at the height of the centre of effort.
I made this video to show the dynamic lift, a flat bottom hull with some rocker, develops at speed.
I think this is very important to resist pitchpooling in heavy seas.
You may want to search for the web site of the multihull designer John Shuttleworth. He has some articles about multihull safety, and one of them is about how to design against pitchpoling.
And perhaps look up the Jordan series drogue, also intended to prevent pitchpoling. If I remember correctly, he writes that it is important that submerged volume should increase quickly with pitch angle. He achieves this with flare and a step. The long, shallow overhang of your sharpie hull does the same.
The approach taken by Nigel Irens with the wave piercing hulls of Idec 2 or Sodebo at first seems different, but according to some work by an Australian AYRS member it really isn’t. His tests showed that even more important than volume is lever arm. The wave piercers achieve that without a lot of weight and windage, and shape the hull so that it rises easily when you inevitably (because of the low freeboard) do stuff it into a wave. Because of the length of the hull, there is still plenty of longitudinal stability.
Finally, I have this hypothesis that a Pacific proa with a high density ama should be the multihull least vulnerable to wave-induced capsize when lying ahull or sailing upwind. The theory is that breaking crests would wash right over an ama that is flooded until it barely floats without lifting it much, and would only lift the lee hull. There is no surf at any place I can reach from Trondheim by bike, so I have never tested this. Do you have surf nearby? If you are serious about cruising the oceans in a proa, it might be relevant whether this hypothesis is correct.
Regards
Robert Biegler
Have you seen “Seaweed”?
Yes, i have seen it before, but did not notice its sharpiehull. Beautifull proa!!!
I have not found any other pictures of it on the web?! Anyone know anything more abot that proa?
You post as many comments, pictures and videos as you want, Johannes! This is very interesting.
Thank you! I only want to give something back to this wonderful site! I have learned soo much from Proafile. I have spent many many hours here.
I came across this quote, Johannes, on the handling of the AS29 -
I have read that before, but did not remember that it validated my claim of dynamic lift.
Thanks!
Is there a stream or fast-flowing river nearby? That would give a cheap tow tank, in which you can test whether you have enough dynamic lift when you tow from the mast at the height of the centre of effort.
Soon on a Youtube near you!
There is no surf at any place I can reach from Trondheim by bike, so I have never tested this. Do you have surf nearby? If you are serious about cruising the oceans in a proa, it might be relevant whether this hypothesis is correct.
Soon on a Youtube near you, part 2. (in a couple of weeks).
Thank you very much! Very interesting points.
I have been thinking the same way about proas and flooded ama. I think that is a real advantage compared with a catamaran or trimaran. They will become airborn in 70 - 90 knots of wind, but a partially flooded proa will not.
Regards.
Johannes.
Have you seen “Seaweed”?
Yes, i have seen it before, but did not notice its sharpiehull. Beautifull proa!!!
I have not found any other pictures of it on the web?! Anyone know anything more abot that proa?
If you go to the link and read the comments, you’ll see Gary has offered to provide the builder’s (Eric Lyons) email address to others. So if you email Gary, he may put you in touch with him.
http://outriggersailingcanoes.blogspot.com.au/search?q=seaweed
Thanx for link and information!
I will send him an email.
I think sharpies has to be quite heavy to realy work. Light sharpies and dories tend to pound and make a lot of noise. The Layden Paradox is a very heavy little cruiser, 640 kgs and 4 meters waterline-length. It seems to be a very good sailor. and quite fast. Theoretical hullspeed for the Paradox is 4,8 knots, and it constantly sails at around 5 knots.
The same goes for a flat bottom proa. I use the same rocker on the bottom and the sides, and i design the proa to be heavy. Im not building a proa for speed or coastal cruising, but for bluewater-cruising. I want speed, but not at the price of less carrying capacity or safety.
I plan to build a 46 foot advanced sharpie proa out of 3/4 inch plywood (18 mm) and the bottom out of 1,5 inch plywood = 2 layers of 18 mm plywood. Heavy and strong. I don’t think it will be very noisy inside.
I hope i can try pulling my proa in the water with a thin rope attached to the top of the mast. I want to see if the dynamic lift will counteract any pitchpooling-tendencies.
Johannes.
I tested pulling the Proa through the water and waves with a thin rope.
The waves are about 15 to 30 cm high (6 - 12 inch), and i think the vaka handles them very well. Even at some speed being pulled from a point roughly halfway up the mast. The ama is being flooded every time i try to pull the Proa, but it keeps its course and behaves very well anyway.
A picture of the proa.
It floats very high. I have tried to sail it filled with water, and it works. Its not fast, but much faster than one would expect.
Johannes.
Soo much for not searching the forum enough….
I see this has been discussed before. I hope my tests have answered some questions.
Very interesting to read through that thread.
Johannes.
Johannes,
You’ve gone much farther down the road of actually building a model than I have.
I’ve VERY much enjoyed seeing this thread. Keep it comming PLEASE 😉
Tom