Boat suspension

[montero]

.

We shouldn't forget that the whole foray into suspension is sorta tangential to the goal of the HPV record. That will be in flat water. The only excuse for putting suspension on a specialized record-attempt race boat is that notion of letting the floats, especially the rear ones, "squat" on takeoff. The fuselage should dive stern down from the foil moment, splaying the rear float back, and the rear float should drop down into its own bow wave trough and nose up. Depending on how low you sling the fuselage, it might even drop the fuselage itself into the water, which would add another temporary planing surface in the form of the fuselage bottom. Shallower angle than the float, but we'll take all we can get. At cruise, the suspension extends back down and the float moves forward and the fuselage rises back up.

Or not. But that's really the only excuse for suspension on a flat-water record attempt boat.

Your propulsion is like FWD car .
If you will use engine stronger than human muscles , your boat will really "squat" on take off ? Or maybe hull behaviour will depend of trim (+ -) of foil axis . Which trim will cause "squat" or maybe will drag the boat up lossing propulsive power ? Did you consider this ?

 

[Horton HCCI]

Your propulsion is like FWD car .
If you will use engine stronger than human muscles , your boat will really "squat" on take off ? Or maybe hull behaviour will depend of trim (+ -) of foil axis . Which trim will cause "squat" or maybe will drag the boat up lossing propulsive power ? Did you consider this ?

I have. (For those following and perhaps bamboozled, I posted some drawings on the "Hydroplaning Rowboat" thread I started. Same post date as today, near the current end of the thread.)

Your consideration on foil axis angle is a good one. It does seem like it might help with squat but detract from forward propulsion. There should be a lot more power and torque at start, trying to clear the hump, than will be available or needed at cruise.

The foils have to be quite deep, I think (about .7 meters) for decent aspect ratio and to keep spray from getting to the surface, so I'd expect it to squat pretty significantly even on comparatively little power.

 

[Horton HCCI]

No.

OK, then how about this argument? (It's not that I dismiss your argument on twist or your recommendations for testing, I'm just trying to justify in my head why my boat might not crumple up into a ball unless I give it some support against yawing forces, which I don't envision how I can do, without huge complexity or compromising free pitch and roll and damped heave.)

So, when you're zooming along on plane, you have a lot of forward speed. Any sideways yawing force from, say, a quartering wave, is gonna be applied over some unit time. The wave moves, say, 3 m/s in the vector tangential to the boat. If your boats going 9 m/s, it'll see only 1 m/s of tangential movement of the wave in that same 1 sec. Ummmmmm ..no, that doesn't seem right.

That might work if the water were flat, like a river, and the boat were crossing it diagonally. Would that mean the boat's forward speed relative to the sideways vector of the river would ensure that the boat sees less sideways movement than it would if it were at rest? Like, relativity, man. Or just frames of reference. The same 3 m/s is applied to the side of the boat, but the boat's moving much farther at speed then at rest, so, if you're riding in the float, the side pressure is applied more gradually. It's slow, relative to the boat.

Sure, there's the up-and-down barrier of the wave--it might as well be stationary, perhaps. But you handle that with your damped suspension in heave and your free pitch. Same with roll. Those are impact forces, as from a hitting a solid hump or berm. Let's pretend those are handled. Have we now given ourself the equivalent of the flat river, with some sideways vector trying to yaw us?

Go lightning fast in your boat. 100 knots. Will it see more or less yawing force per unit time than a boat going forward at 2 knots? Both will experience 3 m/s of sideways yawing force, but the float at 100 knots has covered whatever--50 meters, while the boat at 2 knots has only covered 1 meter. From the perspective of the boat/float, the sideways force is applied to the sides of its speeding craft more slowly. So less yawing force.

Ummmmmm.... Or not. Geez, I'm not even under the influence of anything, but here I am tripping.

Plus, the actual water in waves doesn't move sideways, much. It's a perpetuation of a disturbance--a deformation--that takes the form of up-and downing. Peaks and troughs move away from the disturbance, but it's the up-and-down oscillation that's moving, not the water being displaced. The up-and downing wave propagation speed--its periodicity--depends on boat speed and hull shape, if the boat's doing the disturbing, or on wind speed and distance over which it's interacted with the water, if the wind is doing the disturbing. But the water isn't moving sideways. Not unless it's a river. It's making little circular eddies. There are videos. Waves don't move water sideways at the speed and distance the oscillating disturbance is being perpetuated. They just don't. Dad spent a career in a "wave propagation laboratory." I trust him. Think I'll give him a call.

Any good? No?

 

[montero]

I will make a simple model of this out of curiosity. Free pitch and roll with swingarms is the most interesting feature .

 

[montero]

More on topic :

 

[Horton HCCI]

I will make a simple model of this out of curiosity. Free pitch and roll with swingarms is the most interesting feature .

PLEASE do!!!!
I may be no great shakes as an inventor, but I'm at least a better inventor than an engineer. Then probably comes designer, then draftsperson. My drawings are in PowerPoint. I can't figure out scale, so top view is in inches/10. Profile is real, inches, but for the full-sized boat, so all needs to be scaled down 4 times for the model. So this shows you how good a draftsperson I am. Gotta get and learn CADD. Someday.

Worst of all my "skills" is building. ANYTHING. Suck at it, hate it. Can't cut a square line, much less a curve. Glue my fingers together.

At present, I am stuck on my paper floats. Need air scoops, need to spray paint. Steps and integral vents and chine fences done. I have the PowerPoints for anyone who wants to wade into that swamp. Have sources for aluminum and CF tube to scale, pulleys and wheels, what I think is a pretty good torque motor for scaled power (15 watts!). Fishing line, clamps, aluminum and PC sheet, big rubber bands, RC transceiver and ESC, GPS speedo, you name it. I bought all this stuff. Mostly Amazon, some Onlinemetals, motor Alibaba, some local. Think all pretty viable. I also can provide sources for the limit switches and H-bridge thingy I used to get the first model to oscillate the foils. Very tricky, but works. Foil cars are a dream. Greased lightning, no friction to speak of, don't fall off. My proudest achievement. Haven't tried variable pitch yet.

If you don't like foils or wings or square floats or any of the other "innovations," a regular rotary motor should work OK, but hugely overpowered for an HPV analog. I can recommend probably appropriate Traxx RC truck shocks. I may have, um, "misplaced" mine. Or the cat ate 'em.

Have a good source for you for mini ABS rectangular tube. Don't know if Amazon delivers over there, or Alibaba. AliExpress has most things, and all things CF, if you're willing to wait a few months. I have everything, and where I got it, you're welcome to it. Can pack it all up and ship it to you. You don't have to use it all. .

 

[Horton HCCI]

I will make a simple model of this out of curiosity. Free pitch and roll with swingarms is the most interesting feature .

Oh. ABS angle, too. Very nice for hinges. Really, everything I can think of. I may have lost a few pieces. Having a day job and a wife (and cats) and being lazy and forgetful is not conducive to getting things done.

I am a terror as an internet shopper, though. Better at it than inventing. Every single component of the full-sized HPV has been meticulously resourced and shopped and comparatively priced. Whole boat maybe $2 grand US, possibly a little less. Shipping big things like 4x8 Coroplast sheets is a killer, so local. eBay has gym wheels for pulleys, Wal-Mart for bulk 3D printer wheels for all the cars. You need a lot. More than 20 of each. I KNOW!

Tear up a Stamina 1190 or similar rowing machine for seat and footplate rails/footplate. eBay sometimes has them. Craigslist. I own one. Seat rail weighs about a kilo. Kayak seat for seat back (I bought two, guess it was a twofer. I forget.) Recycled bike parts for pedals. Have those sitting around. Speedplay, 35 years old, shoes to match.

I have an excellent source for small-lot FRP tube, shipping quite reasonable. From an antenna supplier, Max-gain. Don't even consider full-scale CF tube, it's outrageous. I have 13, 3/4" diameter, 7 feet long, I got from Rockwest Composites at an absolute steal on clearance--cleaned 'em out--but you may not have them. They're reserved for the real, full-scale, record attempt boat.

 

[Horton HCCI]

More on topic:

I know both of these. Well, top one, no, but that's just Nauti-craft 2Play, the less interesting of their two. Too tall, active suspension, too complicated, cat. Why? Why spend all that effort and money? They should have made models. VCG is atrocious.

Second is Wav-V, or something. Closer, and it has the wide stance, but why so tall? And why a cat? If you're gonna articulate your floats, go all the way. Why hook them together at all, either longitudinally or transversely? Let each do its own thing with no regard to the others. Inde-PEN-dent suspension. You might as well. Less length of hull in the water for twisting water movement (if there is any) to get a purchase on.

Sure, if you drop your fuselage/platform down to less than half that, you might touch a wave or two. Get some spray. But the goal--my goal--is to even out the bumps, not try to keep the platform perfectly level for guns or to on- and offload people. I have a long fuselage, but that's because rowers stretch their legs and lean, and I want to be somewhat streamlined. And I may want the transom in the water at starting squat to get up on plane faster. And I don't want or need wide, because I'm not trying to maximize cargo space. I'm trying to be a race boat. If you aren't, but want to carry loads and have space, go wider in the fuselage/platform. If you go shorter, too, that should reduce the chances you'll catch a wave. Go higher, like these guys, and you'll virtually eliminate the possibility. But drop those long pontoons, please. Or if you're gonna go displacement and not try to plane, don't CONNECT them, for crying out loud. Stop that. What are you scared of? Just go all the way.

Looks like you're about to try it out. God speed, my friend.

It's a lot easier, if you just tell yourself it's gonna act like a boat-- fuselage pitches and rolls some, in bigger waves--but you're gonna damp the smaller stuff, or stuff that hits faster, so you can go faster over it. It's not the big, slow stuff that'll get you, and that causes so much damage to spines and brains. It's the jostling. The sudden, not huge but huge enough, bouncing. Tame the bouncing, soften the slamming, turn all those lower amplitude but high frequency and spikey waveforms with their peaky tops into something smoother, so your vertical accelerations are tamed and damped. Like Nauti-craft 4Play. They may have faked that video, but it illustrates the goal. Tilt up and to the sides, fine. Comes with the territory. They even bound around, because their fuselage is too high. Grenestedt doesn't. His fuselage is quite low. He's not faking it. You want the (stub) arms high, not the fuselage. Fuselage slung as low as you can without dragging in the water. Anchor points low, right on the bottoms of the floats. Reduces roll and pitch radius both, so it's easier to eat the little bumps. keep VCG down.