Bolger Advanced Sharpie Proa, now with Videos.
I have been thinking about the vaka and all that rocker. I watched the videos of the proa sailing over and over on my computer and i come to the same conclusion again and again. I need to make it slightly longer and less rocker. Something like 40 cm (16 inch) rocker on a 46 foot vaka . Now its 5 cm (2 inch) rocker on a 121 cm (48 inch) long vaka (20 inch rocker on a 40 feet vaka if it was full size).
I think i have to build another model before i comitt to something larger. I will probably loose some light wind sailing ability, but i will also gain speed and windward ability. Its always a tradeof, and speed is soo addictive. I love watching my little proa fly the ama as it speeds along at that dazling speed multihull-sailors speak of.
Johannes.
Today i started my next model. I found some plywood in a trashbin at work today. 1464 mm long and 122 mm wide. Its going to be a scale 10:1 model of a 46 feet proa. Same one plywood-sheet width. Im going with slightly less rocker. Only 4,5 (45 cm) (slightly less than 18 inch, or two inch on my model).
I hope i can try it this coming weekend. We are going sailing so i hope i can try it out in some real waves at sea.
Johannes, thanks for continuing with the posts. I’m actually sketching scow bow proas now, oh the humanity!
I’m curious as to how you arrived at the L/B ratio for the vaka. Going by your first post, 116cm x 12cm = 9.66/1 ratio. Any thoughts?
I’m curious as to how you arrived at the L/B ratio for the vaka. Going by your first post, 116cm x 12cm = 9.66/1 ratio.
I see now that 116 cm is not correct. Its 121 cm. I thought all the rocker would use more of the available length of the plywood, so “116” is from my simple drawing i made before building the vaka.
I wanted to test a “short and fat” proa, to maximize load carrying and usable space for a given length. Now i want to have some more potential speed. Im making it slightly longer with less rocker. 1420/122= 11,64:1. Its the size of proa i can build out of 6 sheets of plywood lenghtwise.
I hope i will get less wave-making resistans, and i know i will get some more wet surface and drag.
Its always a tradeof…
I’m actually sketching scow bow proas now, oh the humanity!
😊
I think we will see a lot of scow bows in many different areas of sailing soon. Winning the mini-trans-atlantic with a scow-bow has opened a lot of peoples eyes. I know a mini-trans-at is a very diffent thing compared to a proa, and the scow bow was to miximize righting moment in the monohull. In a proa there is a lot of other aspects to consider such as hobbyhorsing and the need for high pc and a lot of volume far out in the bows.
Since the hull is so slender i dont think the compareably small blunt bow will be any problem.
I hope you will post pictures and some of your ideas on scow/barge/sharpie-proas. I am very intrested in any and all aspects and thoughts in this matter.
Regards.
Johannes.
Im continuing my new model. I just want to show the difference between my old and new model. One can clearly see the diffence in rocker and lenght. Listening to Deep Purple Highway machine and dreaming of sailing in the mid teens!!! :=)
With less rocker the blunt ends become wider. Now they are 32 mm instead of 22 mm. The very large radius of the side will lower the wavemaking resistans a lot.
I’m curious as to how you arrived at the L/B ratio for the vaka.
I read somewhere that Phil Bolger thought that an advanced sharpie will sail better and better as one makes the hull more slender, and if i remember correct i think he wrote something of 6:1 or 7:1 as a very good fineness-ratio. In Proa-world every problem seems to vanish with length so i have to try 11,64:1 instead of 9,7:1.
Johannes.
I have applied thickend epoxy to the inside. I used as little as i could, and i hope its enough. I dont want to waste epoxy, and it seems to be very strong and durable even in very small amounts.
Now i have to just wait and wait…... I hate this part. I want to sand it smooth, paint it and go sailing with it NOW.
Dan,
I’m going to start with a 24’. the “Final Boat” would probably be 32’, or possibly even 39’ after the concept is proven.
6mm ply all the way Baby on the 24’, with the possible exception of the bottom with might go 3/8” or 1/2”. Depends on where I’m landing for all-up weight.
I’d probably step up to 3/8” topside on a 32’ juz because.
I’m going play with the pod length a bit on the 24’. I kind of like the 50% pod length giving 25% of “knife” on each end. I could have 8’ x2’ box for the berth with @ 2’ on each end to fair it into the flow. Anything much past that is getting too far into the ends to be of much internal use anyway.
James Brett’s Youtube Videos were a pretty big factor in deciding on the viability of the Junk 😉 Then I build one for my little 10’ Seaclipper Tri, and I’m completely sold.
Here’s some video from right after I’ve built it. I’ve done some mods to improve the sail shape, and should be getting it out on the river soon and getting some more video of the upgrades.
Isn’t all that displacement wonderful? I’d want it sitting with the ends just clear at full displacement. If I need to ballast it, I’ll use some Trojans deep in the Vaka to help with final stability an give me some electronics and trolling motor capability. That or a thicker bottom and topsides if it seems a bit flimsy. That’s why I’d do the cheapy plywood boat first.
Tom
http://smalltrimarans.com/blog/?p=6745
http://www.youtube.com/user/tdsoren1/videos
Tom, Check the most recent post from smalltrimarans.com for a tri hull built much as you envision your hull except for space concerns only rather than the dual nature of your pod.
http://smalltrimarans.com/blog/?p=8017
Dan
Johannes,
New model is looking great! I like the 12:1 ratio myself, and here’s the reasons. With Cats and Tri’s, they’ve found that the absolute “fattest” they can go and still have the wave-making speed advantage is 8:1, but simply going up to 10:1 is a huge improvement. this is the ratio on a lot of “Cruising Catamaran” hulls. Racing hulls usually end up in the 16:1 range, but then it’s VERY difficult to get any kind of accomodation in under 40’ unless you have a flare Ala Wharram or Knuckles Ala Shuttleworth. Or Box pods Ala Sorensen 😉
With the Bolger type curvature, I found my 16:1 box keel immersed the ends of the hull, Which Phil thought should be kept just clear of the water line. I find my displacement & forefoot fall into place at right around 12:1.
One of my big questions is how the Bolger theory is going to work out with a Proa that essentially sail flatter than his “intended to heel a bit” sharpies. Schemes have entered my head for the Amas to Purposefully tilt the Vaka for sailing, and level it for anchor or light airs.
The other disadvantage to a very fine hull can be larger wetted surface in very light airs as well as a deep draft to get required payload.
Dan,
I’ve gotta admit, It was looking at various Trimaran hulls shaped this way that helped put the idea in my head. That’s a sweet looking little trimaran.
Tom
One of my big questions is how the Bolger theory is going to work out with a Proa that essentially sail flatter than his “intended to heel a bit” sharpies.
My experience is that heeling is not needed at all. My little model sails very good ( i think) without any heeling. This kind of slender hulls are very directionaly stable, and my model sails very steep upwind without any problem. I dont know how that scales to a large 40+ foot proa. I dont think size should make any difference.
I cant see or hear any pounding or slapping noices when the proa sails, soo that should not be a problem either.
Johannes.
One of my big questions is how the Bolger theory is going to work out with a Proa that essentially sail flatter than his “intended to heel a bit” sharpies. Schemes have entered my head for the Amas to Purposefully tilt the Vaka for sailing, and level it for anchor or light airs.
My experience shows me that heeling is only needed in short fat monohulls. I built a Layden Paradox type of boat with chinerunners, and it sailed wonderful with very little heel. Maybe 3 - 5 degrees, and it does 45 degrees upwind without any problem. With this slender 10: or 12:1 vakas, heeling is not needed at all. I think it can pound a bit from time to time, and that is one of the reasons i want a very thick, strong and durable bottom. 1,5 inch plywood or more. Its going to be a cruising-proa and i dont want to be afraid of grounding my boat. I want to able to sail my proa straight up onto a beach if its an emergency - without destroying the vaka.
I believe one of the big problems people seems to do when building a sharpie, is making it too light. Every succesful sharpie is heavy. Loose-Moose2, Matt Laydens Paradox and Little Cruiser, Chris Morejohns Hogfish Maximus. They are heavy and strongly built sharpies. Thick layers of plywood,lots of stringers a lot of heavy gear and food down low inside the boat.
I know a proa gets its righting moment from the ama and crossbeams, but i think a light sharpie type of hull is going to a pain in the a.. to sail in any type of sea. With some more weight it will move smoothly and calmly through the waves, but with a very slender hull, there is not much resistans going forward.
Compared to loudspeaker-design, i can say i want a very low Q design with lots of Bl and very high efficiency..
Johannes.
Today i have had a moment of clarity!
I think i have everything pretty much sorted out. I will try to descibe what i think is the key points.
Please comment or ask if there is any uncertainties or alternate veiws. I am very interested in your thought about all of this. I need every bit of knowledge and experience i can get, before commiting to a large 46 foot proa.
I know i probably seem a bit eccentric and my ideas are far out, but i hope i can explain things. I hope i make some sense.
There are four very important “points” that is underlaying everything.
1# Cheap.
2# Simple
3# Safe
4# Fast to build.
During my last 4 years of sailing and learning about boats, i stumbled accross the Proa and the Sharpie. Both have a lot of very unique and interesting features. Shallow draught is important to me. A lot of very beautiful cruising-grounds is very shallow. A lot of good protected ancorages is very shallow. The ability to beach the boat upright is also a feature that could save once life, and will make it much easier and cheaper to maintain the boat, clean the bottom and paint it. Very early on i started to think of a way combine those two types of hulls (proa and sharpie).the sharpie is probably the fastest kind of boat to build. Probably the cheapest one too. But i dont like the heeling and pitching and yawing motions of a monohull. That leads me to multihulls.
The proa is the most rational type of multihull. Least amount of material for a given length, or seen from another veiwpoint, most lenght from a given amount of money. Less material means less work assembling it.
A proa is very easy driven through the water, which gives a smaller rig and sails. Shorter mast and smaller sails gives a lot less stress on everything including my wallet.
Hull:
Vaka will be a Advanced Sharpie. 46 feet long, 14,2 meters (6 sheets of plywood in lenght), 4 feet wide, 1,22 meters (one sheet wide) with about 18 inch (45 cm) rocker in both the bottom and the sides. I calculate a maximum total weight of 4300 kgs, and the emptie vaka will weight around 2000 kgs.
Mostly 18 mm, 3/4 inch plywood, with two layers in the bottom.
Ama will be a Wharram Tiki like hull. Deep V hull. 32 feet long and 2,5 feet wide.
The rigg will be a simple stayed alumium pipe. 6,5 inch thick with 1/4 inch thick walls. Wharram soft wing sail and two 110% jibs. I will probably use dyneema for all the stays.
I like the Wharram soft wingsail, as it gives a lot of area without a very high mast. I think its important to have a short and light mast and rig. The soft wingsail does not have a boom, so there is nothing to hit you in the head if the wind suddenly changes direction. A nice safety-feature on a boat full of kids and a total lack of hardcore sailors.
I will write more soon. I want to post this before something happens with my computer and all my work gets lost.
Johannes.
I want to show a simple sketch of my proa.
I must take some time and learn Google Sketchup…
Johannes, I find your approach refreshing and mentally stimulating. I trust you will continue with the 16’ test proa? Sailing it will probably change everything, so don’t fret the details too much on the big boat? Ha! Impossible, I know.
My only strong disagreement with your scheme is the choice of the Wharram boomless wing sail. A boomless main needs a wide traveler for the mainsheet, otherwise, during off-wind points of sail, the sail shape will deform and become baggy as hell, rather than a slender foil. A catamaran naturally provides this wide traveler, but a proa cannot since the mast is so close to the lee side. That is why some kind of boom is very desirable on a proa.
The side profile sketch is very sleek, BTW!
My only strong disagreement with your scheme is the choice of the Wharram boomless wing sail. A boomless main needs a wide traveler for the mainsheet
That is true…. Fu_k! I thought i had a great idea, but looking over my sketches, i see that i drew the mainsail why to small. I have mixed up the scales on my drawing….
I will have to experiment some more on my small model… I really want a soft wingsail without a boom, but it might not be the best solution… The leepod is only 2,3 meters wide from the mast. That is as you say, not wide enough.
I still plan on building my 16 feet version. It will maybe take a while, before i get there. I must test my new slightly longer model first.
With best regards.
Johannes.
My only strong disagreement with your scheme is the choice of the Wharram boomless wing sail. A boomless main needs a wide traveler for the mainsheet
That is true…. Fu_k! I thought i had a great idea, but looking over my sketches, i see that i drew the mainsail why to small. I have mixed up the scales on my drawing….
I will have to experiment some more on my small model… I really want a soft wingsail without a boom, but it might not be the best solution… The leepod is only 2,3 meters wide from the mast. That is as you say, not wide enough.I still plan on building my 16 feet version. It will maybe take a while, before i get there. I must test my new slightly longer model first.
With best regards.
Johannes.
Why the emphasis on super heavy scantlings? Could you compare your approach to other multihulls of any configuration and have even half of the thickness? The material weight will affect your payload. Thicker material is also more expensive.
Dan