Hi Chris, thanks for posting the design iterations, what fun! I like the design a lot better with the breakwaters, it ads some much needed visual mass to counteract that lee dinghy! Before you added them I was going to suggest mounding the hull deck up (in a Newick sort of way) so that it and the dinghy deck were co-planer.

Looking at what you’ve got now, those breakwaters might be pulled slightly forward and down so they appear to be extending off the dinghy. See attachment.

You realize that integrating a dinghy into the “mothership” pushes all my Captain Nemo, Nautilus buttons. 😊

Hi Chris,
Very nice renderings; we have done that with an 8m proa.
Perhaps you might reconsider the shape of your dinghy.

Best Helmut

Hi Michael,

Excellent suggestion, fairing the breakwaters into the pram of the dinghy.  Putting a bit of a cone shape in the breakwater itself will stiffen it up a bit as well.  Very cool!

Another direction I’ve been thinking about is cutting the breakwaters back a bit, to allow the tiller push rods to clear them to leeward, connected to Russell Brown style vertical tillers mounted to the inside of the leeward topsides of the Vaka.  You’d drive the canoe while sitting in the cockpit, facing forward.  Similarly, I’d like to run the mainsheets along that same lee side.

But if the breakwaters are short, the way you’ve drawn them, that may solve the problem.  Everything can pass over them.

Hi Helmut,

GOOD POINT!  In fact, your solution is the logical progression as I consider rotating the dinghy further and further onto its side.

I remember reading about your beautiful boat on Proafile, but somehow it didn’t click that the pod was a dinghy.

I watched some of your model testing videos and the boat seems to be QUITE far over when the pod engages.  I’d love to hear about your experiences with the real thing.  Have you gotten it up on the pod?  How did it go?  Is your dinghy sealed up in any way, or is it an open style boat?

How does your full sized boat sail?  Is it difficult to shunt the crab claw with the pod in the way?

I could not find any videos on that, but would love to hear all about it.

Thanks, everyone, for your input.

Best,
Chris

Hi Chris,

I want to make comments for two of your topics.

First to the waterstays. I sailed a lot on one of the old dragonflys 800’s. connected with aluminium mast profiles and seastays. There was a lot of “splash” when a wave passed under the trampolin. The wires were around 8mm in diameter. As a solution we fitted a solid piece of stainless steel 4 x 15mm and sharpened the edges making an elypsoid out of the recktangle. The effect was that the rod cut the wave without splashing. This should work for your proa too.

Second for the use of Solid Works. I come out of the opposite direction,  designing with freeship but have massive difficulties to work out the details. Are you doing your calculations with a calkulator the traditional way? This is one of the good features with freeship. You can check every minute your hydrostatics and bring your design step by step closer to the desired target. You can fair your lines with great accuracy. Best thing is that you can make your hull with developable panels. Freeship calculates the flat panel measures for print out or as a export as dfx .

Best regards, Michel

Hi Chris,

In order to achieve our goal of self righting to at least 100 degrees we made a flotation box which is mounted between the beams and the dinghy is put over it.
The box is empty and has only an inspection hole; it could be though used as storing for live jackets and fenders. Perhaps next time.
The dinghy is made from 30mm foam which was a bad idea; we boosted the buoyant force but we added a lot of weight for glass/epoxy protection. Plywood would have been the better solution – faster built and much lighter. The less buoyancy could have been compromised with bigger bow compartments, a double floor or similar. Anyway the shape makes the dinghy very wobbly; the side panels should be beveled, perhaps the bottom too. More width would help.
The flotation box and the dinghy have enough buoyancy to carry the displacement of the whole boat.
Here in Greece now is wintertime; trials to turn the boat over we will probably better do when the water is warmer 😉)
I include some pics.
The rig geometry is designed to lift the yard over the beams; so no disturbance by the pod.
Vids might come later in the next year.
We are working on another rig to have something to compare to.
If you are interested in more details don’t hesitate to write a private mail.

Best Helmut

Hi Michel,

That’s good intel on the stays.  The dolphin striker on my Nacra 5.8 could throw some spray as well.  But there’s something so interesting about staying the akas.  Maybe there’s another solution to get them up a bit off of the water.  Spreaders, might be a good strategy, like on a mast.  Or is that just more complication?

I’m going to try out freeship.  I’d like to be less hydrostatically challenged. 

I ballpark displacements by turning the hulls into solids, and positioning a waterplane some distance from the lowest point on the hull.  Wherever I put that plane, that’s the immersed waterline.  So if I put it 8’ above the keel, and cut the rest of the boat away, and set the density of the solid to water’s (1 g/cm^3), then I’ve made a model of a boat shaped chunk of water equivalent in weight to the displacement of the boat pushed 8’ into the water.  So I get a total, but not the ever important distribution.

Hi Helmut,

GREAT pictures.  The more I see of your boat the more I like it!  I really like the little tongue in groove connection between the dinghy and the vaka.  Does that aid in flipping up the dinghy, like a hinge, or does it clip as a final step of stowing the dinghy?

Yes, warm water is better for getting knocked down 100 degrees!!!  I would love to hear that story, but hope you never get to tell it.  But I’d love to hear more about your experiences sailing the boat.  And see pics, of course!

For example, I was wondering more when the lee pod *starts* to engage.  Sven says in this post, (go to #9)...

http://proafile.com/forums/viewthread/25/

...his pod is starting to touch the water around 15 degrees and is holding up the boat at 43.  I was wondering what your experience was.

Anyway, I was inspired by your idea of a dory shaped pod.  So I made one with the exact same displacement at 8’ of immersion (about 700 pounds!) as my earlier pram-pod.  So here is the pram pod and the dory pod.  They’re angled to engage the water flat on their bottoms (front view) at about 15 degrees.  Again, based on my clunky hydrostatics….

Here are some more pics comparing the two dinghy/pods.  To be fair, the dory should have more rocker.  But its an interesting comparison of two shapes with equal displacement at 8” immersion.

Front and top views…

Have you considered carlson’s hulls program?  it’s free and super simple.

Tom

Thanks, Tom, I will.

I want to be able to export back to solidworks…to do the detail design work.  So I’ll look and see if it outputs IGES or STEP or something else I can use.

I give my CNC router vendor solidworks of what I want him to cut, and the CAM software works straight from that format.  That way I can do profile AND 3d cutting in a batch.

What are folks’ favorite software for hydrostatics and lofting?

best,
Chris

It will output DXF and VRML.  It also generates patterns for all of the parts and has nesting capabilities to lay it out on sheets.  Carlson actually sells CNC machinery, and the output can be used on his stuff at least to cut out the parts.

It’s just a VERY quick and easy way to generate a hull section and vary the waterline/displacement.  Free!ship is MUCH more powerful, but much steeper learning curve.

I taught myself to use it reasonably comprehensively in a couple of hours.

Tom

Too much “life stuff’ and not enough building has had me thinking a bit on what I want to build. I keep coming back to the Wa’apa at 24’ rigged as a proa.  This thread has me thinking of how I can combine yet another future project, a strip built Stand Up Paddle board.

I see the Wa’apa as supremely beachable here on the west coast of Florida and down into the Keys, so a dinghy for the type of day sailing and camp cruising isn’t on my list. But I could definitely see the use for an SUP.

I’m toying with the idea of using it lashed to leeward as a pod/platform/emergency ama. The other thought is to lash it on the windward side about half way between the vaka and amas on top of the iakos as a bench for seating while under sail, then unstrap it at the beach for some paddling and fishing fun.

Where do yall think it best to lash it? I really wish I was even remotely close to having time to build them both and just test it out, this idea keeps tickling at my brain.

Here is the SUP that is on the ever growing list of things I want to build http://woodsurfboardplans.com/BuildingawoodSUP.html

Thanks
Jon

Hello Chris,

These little brackets on the vaka are solid wooden fittings (female on the vaka and male on the opposite part); it is a final step for the dinghy and also on the other side for the cockpit floor. They are glued with epoxy and anchored with 12mm wooden dowels through the hull. I include a pic with the box upside down not mounted.

Probably you will never hear a story about tilting ‘MeToo’, because the ama has a water deposit of until 225 liters ballast water. The water is pumped by two pumps from the cockpit. So stability will not be really an issue; always enough RM. But there are of course a lot of other issues….like a ‘turtle-insurance’ it is a very welcome and necessary advice.

I read all of Sven’s information (very good Sven, couldn’t agree more. My congratulations); I am afraid you have to wait until spring for more sailing experience with ‘MeToo’ – anyway some information might differ a lot because of the crab claw rig. The sail is supposed to ‘travel’ a lot lengthwise and in wward and lee direction (the mast is tilting) in order to be balanced and steer the direction the boat is supposed to go. So the task is to balance the boat, skimming the ama just a little bit over the surface and produce the least resistance… 😉)

Regarding your dinghy pod – I decided against the 15 degrees beveled dinghy mount because of different reasons. One was the beveled surface would not be useful and collects water and dirt, the more important one was the ease of connection to the beams in the 90 degrees angle.
If I had to build the dinghy again I would prefer a less wobbly shape like a kayak shape for example. It is also important to have some space in the dinghy in order to transport two people and some gear. I include a pic of the ‘Merganser’ which has a very promising midship section for my opinion. The rest of the boat could be adjusted.

Best Helmut

Here’s another example of someone trying to use a dinghy on a proa, though not as the lee side float.  I wonder if this thread is where he got the idea 😉  I do like the way he suspends it.  If your Akas stepped up, you could completely avoid complicated/intrusive hull penetrations on the dinghy.

http://groups.yahoo.com/group/proa_file/files/Proa ideas and project details.pdf

Tom.

I wonder if the dory shaped pod would be a better choice for sailing through steep chop? It looks like it would somewhat cut through the waves instead of plowing through.