Planing amas

Any threads here on planing amas?

I’m doodling another sailing canoe, using sails, foils, and spars I have cluttering the shed and garage.

I did a sailing canoe that was a flat bottom 16’ by 36”, with solid-ish 2.5 hiking wings out each side which worked ok, but I noticed that the wings (the ends of which were 1” by 1” by 2’ on each side, plywood and hemlock, were acting as floats/stabilizers esp keeping the weight of aluminum force 5 mast from capsizing the boat at rest, and slowing down the rate of roll under sail to the point it was placid,a bit boring, and didn’t seem to slow things down much. Sooo, I started thinking about a tri with small outriggers at the end of a longitudinally moving hiking plank that responded like a dinghy, but had the benefit of skinnier less drag central hull. Thing is, how skinny? And what shape and length for the stabilizers? My software is happy with a flat bottom double end hull 16’ by 24” but the outer floats aren’t that simple , or straightforward. And changing to say 16’ by 30” would seem to change things dramatically. (?) Is there a rule of thumb about this? My hunch is that I’ll be able to balance the middle hull in light air and smooth water so the outer floats don’t see the water until they are planing. I was messing with sort of thing with a small proa, but the problem there was the float was behind my back so it was hard to observe what was going on. I’m planning on going with solid balsa to make changing the shapes easier on the floats, starting with a square cross section, high prismatic, and shaping from there, and sealing with varnish.

Making things more interesting, I’d like to fix the floats to a hiking plank (sic) that will help the floats react dynamically to the water, kind of like the Gougeon’s design Adrenaline. The plank will move longitudinally, and I will be ‘chicken hiking’, my feet inside the hull.

Any ideas, or is this real $ize modeling and testing?

I’m not looking for ultimate speed, more a crisp, elegant, responsive, fast, minimalist ride. Kind of a sit down d2/racing longboard vibe for a 71 yr old that’s easy to float back on after the inevitable…

 

That all depends upon how much restoring force you want and thus how much change in motions you want too.
It is easy to sketch out, but not so easy to "design" without a set of parameters you wish to satisfy.

 

I guess the feel of it is too vague?

what kind of parameters would help?

weight of hull- 60-70 pounds
Length of mast ~ 20’
SA ~ 110 sq ft, think Merlin Rocket main plan form
Sail foot~ 6.5 ft
2 formula windsurfing skegs
2 Phil’s foils rudder/DB
Figuring displacement ~ 300 pounds
Bow~1 foot
Stern 4-6”
Single hiking plank 7-8’ by ~2 ft
Floats 4’ to start?
Don’t know if main hull needs to plane
Low prismatic for light airs
Protected bay sailing mainly
Crappy broken up ramp / trailer launching
Ply construction - little if any epoxy- I’m allergic
Boxy rails, flat bottom- I like the feel and sound and easy to build
Floats out of water in the light
Hiking to kept flat
Double ended - see boxy rails above
the other sail is a dipping lug, 110 sq ft-
Mainly because the mast can be near the cg/clr/ Lcfloat, and I’ve got it + carbon top spar.
2 masts, one carbon, one aluminum Force 5- they weigh pretty much the same, but aluminum mast has lower cg

this help?

 

The principal characteristics of your existing boat.
In with that, what is the behaviour of the boat under certain conditions, and then what you wish to change in said condition(s).

Don't over think this...

 

Existing boat hull/wings have been in a land fill for 6 years- this idea would be an evolution of the first- I can include a YouTube of it if that would help.

 

All of them would be great.

It didn't sail for six years? Why?
A couple of amas on the end of the previous wings would make it interesting, and a trimaran.
How did it sail in stronger winds?
I can see you're not a big fan of freeboard.

Most importantly, what do want to change, and why?

 

Dump the sliding plank and let Smythe´s Synergy inspire you. It is a perfect example of planing amas. It has been covered elsewhere on the internet and here, but I don´t know if there are any in depth calculations, though. The attack angle and the lift of the planing boards might be the problem to solve?

My next, next build will be a leftover Nacra 5.8 hull from my tri build, with two Fanatic wave boards and a F18/A-cat main, ie a very clumsy clone. Might also try this on my ongoing foiler build, to evaluate the rudder system. Note I am also 70+.

 

Mark Palmquist is exploring and prototyping some related ideas on Duckworks - might be worth a follow on fb

 

I was trying to see how minimalist I could go with freeboard, kind of a D1 smooth water board (no bow rocker) sort of approach, see if I could get weight down- used the Boyer torture ply approach of using 2” XPS for 3/4’ of a bunch of bulkheads/forms, which worked well.

The problem with it was the weight of the aluminum mast and how far forward it was- even when I was standing on the stern, it was impossible to get the bow up at all- add to that some Aussie designers arguing against rocker, which I thought I would try ….

oddly enough, it was ok in heavier winds, if I jumped on the stern at the right time to get the bow up on a wave, but the nose pearling downwind in light winds was, um, weird- I tried an anti dive plate at the bow, but it snapped off and tore up the bow- not the balsa nose, but the 4mm okume ~2’ behind the bow.

I’m allergic to epoxy, so this was my 3rd attempt at Titebond III Okume and wood chine logs. It leaked, and after the bow destruction event, I moved on to other things.

The double end flat low prismatic hull (.48!) went through the water almost exactly as Vacanti software predicted, with very little wave propagation when it was flat, which was weird but cool, so I’d like to explore that more. Amas will help keep the hull from heeling- when heel gets to 5-10 degrees, wave making started going wonky. More slender hulls of the same shape have better numbers, at any rate, at 5-10 degrees, which amas would help with.

I’d like the components to be lighter, so launching gets easier- and I’d like to get a system that allows for easy on/off of outer hulls so I can experiment with shapes. I want to keep a freestanding mast- plug in, pull off. I’d like to keep the responsive dinghy feel of a smaller boat than the Smyth magnum opus, which I really dig.

 

(>70) Very cool what you’re doing! I had a couple of old short boards around for the same reason, but right now I like the general gestalt of a more canoe/lagoon like vessel that I don’t have to run around. I’m gravitating towards a plank more like the old school 16*30’s, although not sliding athwartships to save my shoulders some grief- who knows where this will go- I can see going towards a more class b sailing canoe approach with a couple of small speed needles as amas, which would be a smaller version of what you’re doing. I’ve ordered a bunch of .8 mm etc aircraft ply to make some Gougeon -esque models to get a better idea of what I’m doing.

 

Palmquist's concept:


16*30's?
Paul Scott, what about a quick drawing, to show what you actually have in mind?

 

I’ll get to a line drawing or 2 later today- just had the new COVID + flu vaccines together the other day (who thought that was a good idea?), need to get my concentration together .

 

Is there an easy way to calculate ballpark figures of lift and attack angles of planing hulls based on speed, area and weight?

I think it is a good idea in the long run, will get mine soon.

 

Two things. The "wing" planer only works on a few points of sail. I had a good friend that built one many years ago (maybe 30+) that did work but it would plane, accelerate, the drag from the wing and the main hull would change and all control would be lost. He was starting to experiment with articulating wing ends when development stopped. I think real foils would have worked better and been much easier to sail.
I currently have a couple of tris, a Dragonfly 800 and a Crowther Buc 33 and in racing them I have found that loading the leeward float to about half displacement with my crew is faster than trying to keep the boats flat or healed to weather. The floats on both boats are about 11 x 1 beam to length and seem to have less drag than the 8 x 1 main hulls so I keep the movable ballast out on the low side nets or floats. Long straight hulls with some planing surface aft on the amas seem to work well. Smyth's light weight semi planing tri did work, but he is also a very good sailor and someone else with less experience might not be as successful.