I try to credit my influences.  Scampi was a response to scamp.  Palindrox was a response to Paradox.  Sweet Rhode Island Red is a response to Proud Mary.  Both are songs by Tina Turner, who, as Michael pointed out, owns Proud Mary. 

Sweet Rhode Island Red is a butt steered, “slot” rigged gibbons/dierking rigged proa without a boom.  That was a revelation to me. The “loose footed” nature of the sail makes it easilly handled and reefed.  And loosing the foils (which I’m making for my boat now) is heaven, as long as it works.  Having the mast pivot in a slot works at a certain scale.

What I love is that the rig is to leeward. A scooching boat works much better where the scooching is unimpeded.  The slot itself is not drawn.  But we’ll assume it works.

I worked on a tilting rig version, based on my interest in equilibre’s windward/leeward and fore/aft leaning rig for steering.

But I kept it somewhat simple, figuring that a 1/5 longer Proud Mary would still be dingy like.

Very nice!

I love the more fluid lines, makes it even more musical than Proud Mary!:-)

One remark on the rig, there is not a strait profile of the model, but it seems to me that the clew of the sail is too high for the sheeting angle to work well. I think the middle of the yard and the clew of sail should describe a line that would go no further than the bow. Just need to adjust the mast.
Also, I’d make the first board of the platform longer, to make it easier to move further along the vaka for steering. I plan to do this on Proud Mary next time I work on it.
Does it make sense?

Your renderings are fantastic, not just this ones, all of them! What software do you use? (I remember you mentioning it in another thread, but couldn’t find it now…) I’d consider trying a very simple and basic program, if I could achieve something similar!

Love the Tina theme as well, maybe a paint job evocative of it would look funky!! (your’s look great as is thou)

Cheers

Hugo

OK, so the midpoint of the yard to the clew draws a straight line to the STERN (or old bow), right?  I’ll tweak that. 

Could you say more about why the sheet does not just go to the stern, but it split between the stern and the cockpit?  How does that “choose” the angle?

You mention adjusting the angle of the mast.  What happens to the bottom tip of the yard as the mast becomes more vertical?  Does it move away from the deck, or along the deck away from the bow?

Thanks for your thoughts, Hugo.  I’m interested to see how your polytarp sail turns out. 

Have you figured out how high Proud Mary is pointing?  Maybe a GPS is the best way since it takes out the error of leeway you might encounter with a compass.

I use Solidworks to draw and Photoview 360 to render.  The learning curve for Solidworks is a bit steep, but once you get over the hump its a VERY powerful tool.  This “rendering” is actual plywood (not just surfaces)—bulkheads and all.  I’m thinking about translating this design into a “kit” complete with CNCed foam amas, that could be cut anywhere where there’s a CNC router.

Best,
Chris

Here’s the revised sheeting angle.

Somehow the “foot” always looks longer than the “leech” even though they are EXACTLY the same.  Strange…

Here’s one showing the bulkheads.  There’ll be a stringer at the cockpit floor level on both sides, running the length of the boat. 

At 16” immersion, Red is displacing almost 1400lb.  The cockpit floor is 22” above the keel and the cockpit is 14” deep.

The water is a lot colder here—I need some freeboard!  I wonder how that increased windage will effect the handling.

Have you figured out how high Proud Mary is pointing?  Maybe a GPS is the best way since it takes out the error of leeway you might encounter with a compass.

Funny you ask… I’m in NYC at the moment, and one mission of mine for the next 2 days is to try to get a GPS to play with. I’m quite lost on what to get, looking for something cheap that does that job, as I don’t really need a GPS for anything else…

Any suggestions?

Luomanen- I’d suggest adding more flotation to the top of the ama in an inverted V profile. This way when the ama is buried it gains buoyancy while the profile helps it shed water and come back to the surface.

Gearbox- Look into running/cycling GPSs, or even better, a smart-phone. A smart phone in a water-proof case is a mini chartplotter and can access lots of apps or websites to make displaying and sharing your data much easier. I’m fairly certain you can have it arranged so it shows magnetic heading as well as your actual track, which would make calculating your leeway very simple!

OK, so the midpoint of the yard to the clew draws a straight line to the STERN (or old bow), right?  I’ll tweak that.

That’s correct.

Could you say more about why the sheet does not just go to the stern, but it split between the stern and the cockpit?  How does that “choose” the angle?

It might not be needed if all is really sorted and you are happy that it should be that position. In Proud Mary I tend to try different adjustments, and generally the above mentioned line does not go strait to stern. The sheeting point should be where the line meets the vaka, so either you have several anchor points or a system of changing it. this was my solution to that problem, and it seems to work fine.
Also in monohull boomless sails, the sheeting point should move according to point of sail to keep the right angle. Not sure if this makes much sense, but this arrangement seems to me (intuitively more than anything) to do this job.

You mention adjusting the angle of the mast.  What happens to the bottom tip of the yard as the mast becomes more vertical?  Does it move away from the deck, or along the deck away from the bow?

It does move away from deck, but what i usually do then is adjust the high of the yard on the mast until it is back in place.

This “rendering” is actual plywood (not just surfaces)—bulkheads and all.  I’m thinking about translating this design into a “kit” complete with CNCed foam amas, that could be cut anywhere where there’s a CNC router.

That’s really cool!

Hope this makes sense… As proud mary was, and is, more of a “sort it out as you go” project some solutions might be strange and not the best. “Sweet Rhode Island Red” has the potential to be all sorted from the start, by looking at your way you work.

Gearbox,

re GPS, The least expensive thing that will export gpx files, often thru a serial port some others via removable memory card.

Skip

Gearbox- Look into running/cycling GPSs, or even better, a smart-phone. A smart phone in a water-proof case is a mini chartplotter and can access lots of apps or websites to make displaying and sharing your data much easier. I’m fairly certain you can have it arranged so it shows magnetic heading as well as your actual track, which would make calculating your leeway very simple!

re GPS, The least expensive thing that will export gpx files, often thru a serial port some others via removable memory card.

Thanks! So any device will do, the key factor is that it export gpx files.
The hunting for such machine will start!

Appreciate the quick advise.

Cheers

Luomanen- I’d suggest adding more flotation to the top of the ama in an inverted V profile. This way when the ama is buried it gains buoyancy while the profile helps it shed water and come back to the surface.

Hmmm…it seems like the modified “heart” shape cross section (without the dimple in the top) would gain more buoyancy (and beam) as its immersed than a “diamond” cross section you’re talking about.

I also like that the heart shape has a little bit of a nice place to step on the top (not flat but a large rad)—while still providing smaller radii at the edges to shed water.

Maybe I’m overestimating this shape’s ability to shed water.

In any case, that’s one of the great things about designing for machined foam—it can be just about any shape you can get glass to stick to.

For something that will be punching through waves, you want the pointiest top possible, with most of the buoyancy down low for lower wetted surface area. If this is a small sport craft, I don’t really see the need for trying to balance on the top of the ama? Check out the Jester class pictures for an idea on what I mean, though I admit I was thinking the deck should be even more steeply angled.

Luomanen, do your designs include things like bulkhead profiles and dimensions for various things?  The reason I ask is that the proas look so good they almost drive me crazy. 

How far apart are the crossbeams?

What are your deck boards made of? 

This project does not have a house or cockpit, but what construction method would you use for the house, lee float and cockpit on your other designs?  stitch and glue?

The sponson, did you invent that shape?  I assume it is to cushion by splashing upon impact with the water surface.

Do you have material lists made up?  Sometimes I question whether parts of the designs would look as good if I built them with klunky affordable materials.

The whole shebang is 1/4” plywood.  It would be built stitch and glue with the stringers and sheer clamps already glued on before it gets stitched.  Then the whole thing gets the fillet and tape treatment.  The decks and cockpit sole are going to need some area to stick too—since you can’t reach in and fillet them.  Thats part of why you need the stringer and sheer clamp.  It also makes the sides fair.  All this is stuff learned making my Wa’apa—which is tank-like sturdy.

I might need some transverse cleats on the bottom of the deck and cockpit sole—but maybe not—the whole boat is pretty skinny.

I’m just guessing at those scantlings based on my Wa’apa, Skips boats, etc.

I’d make the deck boards out of 1/8” ply sandwiching 1” blue styrofoam.  Those boards are 96” long and a little under 16” wide.  So you make up the sandwich, with hardwood where the edges will be, and cut it into 3.

The safety ama shape is my idea, but its placed based on Sven’s description of Pacific Bee’s stability curve.  The pod touches when it heels 15 degrees.  At that point the ama is about 28” off the water.  Time to come down!  The Concave shape is hopefully to trap some air and make it bounce with ground effect.  Also, I don’t have any restriction on shape because its machined, so I went nuts.

I want a proa that puts itself back on its feet when the ama gets too high!

As far as cheap materials—I’m all for them.  I used Meranti ply instead of Okume—seems fine so far.  The amas are blue foam insulation (just like the machined amas on my Wa’apa) from home depot.  My epoxy is the cheap stuff from Duckworks.

I need to learn some lightweight construction methods.  However, I do not believe that foam core 1/8” plywood will span that distance.  I might be wrong.

The edges would be hard wood—not foam, in case that wasn’t clear.

I think it would work fine, but we’ll have to find out.  The nice part about putting the light part on the inside is that you can always throw some glass on the outside.

The alas are only 6’ apart.

Mike Leneman has made some pretty awesome structures with blue foam and plywood—you’d be amazed how strong they are!