Bolger Advanced Sharpie Proa, now with Videos.
Tom,
Interesting model. My Tamanu hulls are quite a bit like your central hull portion and never stuffed the bows in the short steep cop of the Texas 200 even in catamaran mode. Three thoughts spring to mind: The first is that the pod seems to make sense like this as it isn’t grabby or blunt although it will weigh more. The second is that as the pod engages the water it makes a nice v shape. The third is the large flat might be uncomfortable if it does pound. Richard Woods seems to be using the same concept for his new Strike range of trimarans. If it’s high enough off the water not to slam, it should work just fine. Perhaps since the boat would not be harmed in any way by making a curve in plan view to the bottom of the pod, you could keep the bow portion of the chine flat further from the water. It could look a bit Newick-ish if the sheer was also curved to match. Not quite as efficient use fo the ply though. Alternately, you could angle the ply outboard and get the sweep of the sheer narutally?
Dan
Dan,
I feel like I’m starting to Hijack Johannes’s thread, and I should drag this back to the Box keel. Would you prefer that Johannes?
In any event, the concerns you raise are pretty much the same ones I go back and forth with. How far over the waterline do I need to be with the flat without making the boat too high? The pod really needs to be @ 24” OD to allow 4” of foam and a little framing if I want to use it as a berth flat. That also means it really needs to be @ 24” wide for at least 6ft. Wide actually makes it engage at less of an angle, though flaring the pod itself doesn’t make the bottom edge engage any sooner, and actually makes it a shallower “V” engaging the water.
putting rocker into the pod profile would sure look better, and would also reduce the chance of pounding, and I’m seriously considering this as it wouldn’t greatly complicate the build or remove any volume where I really want it. As far as putting some deadrise in the flat, that would actually take some panel development, and I would have to frame it back to flat inside for the berth. That would add even more weight and complexity.
I’m thinking this hull stretched out to 32’ at the same height would really start to look nice. I could also keep the pod @ 24’, meaning @ 4’ of sharp “Keel” hull at each end before the pod even starts. Might look like a WW2 submarine with the ballast tanks 😉
I didn’t do it in the model, but the topsides of the “keel” hull would be largely cut away inside of the pod, and the straight section of the “box” the pod is wrapped around wouldn’t be there either. I’m really only adding the material required for the flat with a little framing to the hull structure. Layout of all panels is dead simple and fast. I’m thinking of doing this in cheapo plywood with only the chines taped as a test. I’d put real money and effort into the rig and rudders and such, and if it all works go out and buy the good stuff and the epoxy for a long term boat. Move the expensive bits over, and have a pretty low toxicity fire with the test bed.
Tom.
I feel like I’m starting to Hijack Johannes’s thread, and I should drag this back to the Box keel. Would you prefer that Johannes?
No! That is no problem. Its very much the same type of proa im going to build soon (i hope).
If you start building the real thing, its best if you start a new thread, so as not confuse people about our different proas.
I have been looking at your modell, i think i understand what you want to do. Im afraid all that overhang/pod - structure will give to much area for waves to “grab” hold of. It might make the boat very difficult to handle in rough seas. I think its very important to keep the first one third of the hull clean and lean. Imagine large breaking waves and how it will behave. Even if its going to be a coastal cruiser, i think its important to be able to handle the boat in a blow.
I think that is a reason Russell Brown use short leepods on his proas.
It looks like a simle and easy way of building models, to get a feeling for how it will be.
Regards.
Johannes.
Yes, a lot of “I wonder”.
I’m thinking of building a base “keel” hull model that I can stick different pods onto. I’d maybe step up to a 1:6 scale for that (4’ long model). Makes coming up with hardware and keeping curves fair that much easier.
Tom
Tom,
I agree with Johannes. Both boats are similar in underlying concept and maybe they will both benefit from some ‘cross-pollination’
I’m thinking this hull stretched out to 32’ at the same height would really start to look nice. I could also keep the pod @ 24’, meaning @ 4’ of sharp “Keel” hull at each end before the pod even starts. Might look like a WW2 submarine with the ballast tanks
I think this would look good, Tom, and it would mean only 2-3 extra sheets of ply if you kept the other dimensions the same.
Would a tapering ‘fillet’ panel of perhaps 12” (extending 8.5”) at its widest between the berth flat and the hull topside be a possibility for you? It would lessen the flat area open to pounding and brace the berth flat and topside at the same time
I’m thinking of doing this in cheapo plywood with only the chines taped as a test. I’d put real money and effort into the rig and rudders and such, and if it all works go out and buy the good stuff and the epoxy for a long term boat.
Beams and ama? Interesting idea especially if you didn’t fit it out and as the main hull seems so quick to put together. Any ideas at this stage for “Plan B” if it didn’t work out for some reason?
I agree with the cross pollination James, my daddy just brought me up to be polite 😉
The fillet idea is excellent. if I ran it at 45degrees between the flat and the topside, a 16” wide (2 rips on one more sheet 😉 would extend 11.3” into the widest part of the flat, or almost the 50% point. I could always monkey the angle a bit, but the 45 degrees makes this an easy piece to layout the curvature on as it reduced towards the ends. Access holes could be cut it the topsides from inside making a nice little storage area/buoyancy chamber.
Thanks!
James,
Just read the last half of your post 😉
Rudders built ala Gary D’s latest on his blog. I love that rudder design. Adjustable for depth and kick up either direction.
I have a local outlet where aluminum tubing is available at scrap prices, so My mast and akas will probably end up as such and be re-useable.
Sail is going to be a Junk, once again re-useable with all of the sheets and such.
If I put time into a good Ama, that would be as well.
If the main hull was a complete failure, it would be pretty easy to do something simple and proven similar to Skip’s P52 or maybe a 24’ wa’apa based hull.
I’m going for more safety/cruising accommodation than pure speed. I plan to step the mast well to windward to get the thrust aligned to the point of leaving both rudders down all the time, maybe even interlocking them. shunting would only involve sheeting the sail over. with the Junk reefability, it should be an easy single hander with plenty of volume for daysailing 3 or cruising 1 to 2. good cabin for PNW weather.
Tom
I’m glad the ‘fillet’ panel (I’m sure it has a NA name!) sound like it might be useful for you, Tom. So now I’m hoping you find suitable building space soon! 😊
I like the junk rig too. After reading ‘Bunny’ Smiths development of it, I knew it was what I wanted to try. Terho’s success with the van Loan rig sealed the case as far as I’m concerned. So good luck with it all!
James,
Just read the last half of your post 😉
Rudders built ala Gary D’s latest on his blog. I love that rudder design. Adjustable for depth and kick up either direction.
I have a local outlet where aluminum tubing is available at scrap prices, so My mast and akas will probably end up as such and be re-useable.
Sail is going to be a Junk, once again re-useable with all of the sheets and such.
If I put time into a good Ama, that would be as well.
If the main hull was a complete failure, it would be pretty easy to do something simple and proven similar to Skip’s P52 or maybe a 24’ wa’apa based hull.
I’m going for more safety/cruising accommodation than pure speed. I plan to step the mast well to windward to get the thrust aligned to the point of leaving both rudders down all the time, maybe even interlocking them. shunting would only involve sheeting the sail over. with the Junk reefability, it should be an easy single hander with plenty of volume for daysailing 3 or cruising 1 to 2. good cabin for PNW weather.
Tom
Tom, if you go with the shorter pod (it could be 16 or 24’ or anything really) you also cut some weight while gaining fineness ratio by going to the longer vaka. The pod can be the same height off the water as Brown’s work since it’s high enough. The 45 degree panel/ support for the pod would soften the blow and make it a smaller area to smash into if the wave period were wrong.
The junk is a proven commodity with James Brett’s proa as well. Seeing how much capacity my Tamanu hulls have, I can only imagine a 32’ hull will carry your load with aplomb. I do like a bit of v in the front sections though as in certian wave period and chop conditions the hulls is a bit noisy—never pounded, but more of a slurping gurgling sound. Keep the images going! It feeds the imagination of so many to see a fresh idea. What scantlings were you thinking of going with for the hull?
Dan
Here’s a couple showing the Heel angle where the pod starts to engage. While I have concerns as to the looks and possible pounding of the flat underside, it sure meets the water nicely, almost a “tunnel hull"effect that seems would actuall tend to head the boat up instead of possibly dragging it down wind.
Tom
I did a quick sketch and a 32’ boat with a 16’ pod. Not taking the pod all the way to the bow makes it look just like the picture linked of the green proa. I don’t know that you need much rocker in a boat like this unless you want to go with the Bolger thing. My Tamanu has maybe 3 inches of rocker. A 32’ hull with 12” of rocker will need lots of weight to get it down on it’s lines unless you want both ends out of the water most of the time. A super rough idea might be the displacement of a 24’x2’ box for something like 1600 pounds of displacement at 6” draft. That’s lots of displacement to play with!
Dan
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
Im sorry i have not been participating much lately. I have been down with a nasty cold for the most part of the two last weeks.
I enjoy and read with lot of interest all ideas and thoughts about this kind of scow/sharpie/barge - proas. Its a very interesting concept.
Since the proa is such an efficient kind of sailing-machine i think there is lot of room for experiment. One does not have to make everything as effecient and streamlined as possible. One does not have to work hard for every knot of speed. Speed is natural for a proa. What we have to work with is making the proa load more gear and larger on the inside, to suit colder climates, especially up here in sweden. We only have one or two months a year were one wants to sail the boat without a lot of protective clothing. May in sweden is usualy cold and wet, with lots of rain and wind.
I have filled my ama and most of my vaka with polyurethane-foam, so it can’t flood when sailing in heavy wheather. Now i just wait for some harder easterly winds, so i can test it. I want a good steady 30 - 40 knot wind so i get breaking nasty waves at the beach were i usualy test my proa. I might have to sew a new smaller sail. I want to see how it behaves in hurricane-winds.
Johannes.
Sailing with the camera looking backwards
More sailing with a camera.
There is very little wind and waves, but i think i can see that its very stable and does not pitch or hobbyhorse at all. Very good damping of unwanted movements.
It does’nt sail very fast, but there is not much wind. A soon as the wind picks up, it sailes very fast. I thought that multihulls did’nt sail very fast without much wind due to a larger wet surface of the long slender hull. It does sail very good. I cant feel the wind but the proa sails close to theoretical hullspeed. Very strange!
Johannes.
I placed the camera just in front of the mast, looking strait ahead.
Very calm and smooth movements.
I need a better camera that is waterproof.
Johannes.