Boat suspension

This is old hat.

Vessels with suspension https://www.boatdesign.net/threads/vessels-with-suspension.22148/

Experimental Catamaran with active X-Y-Z stabilization from "Velodyne Marine" https://www.boatdesign.net/threads/experimental-catamaran-with-active-x-y-z-stabilization-from-velodyne-marine.46493/

 

Thank you for dig it out . Today I found a thread on this forum , Turkish guy wanted to sail from the Black sea to Amsterdam as a barge leech.

 

IMO the key missing term here is "un-sprung weight".

I'd try something more like the Delta Seadart experimental jet fighter with ski(s) and shock absorber.
Make them just skis, not floats, for lighter weight and better sprung to un-sprung ratio.
At rest or lower speed the skis would submerge and provide anti-roll damping.

Maybe tune the size of skis so the hull could still take a bit of wave in tough conditions

 

"un-sprung weight" I know something about it. This is an important phenomenon .
Post no. 3 from 3:10 looks ok. If the buoyancy of the floats were reduced, they would turn into skis. I wonder how to propel a ship on waves on these skis.

 

Basically, that is what the Soviet/Russian Raketa (Project 340) and Voskhod (Design 352) hydrofoils where.

 

They are successful hydrofoil designs but they suffer on the waves .I like their CCCP futuristic look and overall concept.

 

Омский теплоход "Полесье-8" после катастрофы https://omchanin.livejournal.com/758393.html

 

Wetbike - Wikipedia https://en.wikipedia.org/wiki/Wetbike

This PWC used suspension. Other than that, I liked it.

 

OK, well, I'm model prototyping a quad-hull suspension setup very much like Nauticraft 4Play. Four, because geez, you need independent suspension, do you not? What do you do when you're all torsioned around over multiple waves, or crossing at an angle, etc.? Suspension on cat hulls is like leaf springs on a fixed-axle covered wagon. I don't get it.

This is not hard. Use a swingarm, like a motorcycle. Trailing arms behind, "leading" arms in front. Just hang off a bar on a simple hinge. For my purposes, I think $30, 1 lb apiece mountain bike rear shocks should work nicely. But you do you.

And don't articulate or do anything else fancy, like wishbones or whatever. Just use a bloody U-joint where you attach to the pod. Make your own. Free movement in pitch and roll, fixed in yaw. Even I can build something like this, and I can't build anything. Do we need more?

So, what's wrong with this?








Why--on earth--will this not do all that's needed? What am I missing? Some aspects of boat design are hard. This does not appear to me to be one of them. Can we just get ON with it, please?

 

Mechanical advantage...draw a FBD of the forces in your linkages.

 

Can't. Know what that is, can't do it. But the shocks work on a bike with roughly the same lever arm to the seat/chainstay. They're rated for 550 lbs or something. I could get 750 lbs, but I think that's overkill, as there are four of them. This is for a rowboat. 200 lb rower, 45 lb boat. It's an overgrown bicycle. I can't see it folding into a potato chip, but I guess the only way to find out is to try. Really wish I didn't have to. I prefer to dream.

 

What I guess I mean to say is, suspension is so obvious a solution for boats in general and planing boats in particular, I simply don't understand what the holdup is. We know how to make suspension and shocks. All fast boats that go on rough water should have them. Failing to do this is subjecting people like hydroplane racers and navy patrol boat drivers and crew to chronic concussions and brain injuries. Domestic violence. Drug abuse. Suicide. This is unacceptable to me, when it can so easily be remedied. It makes me FURIOUS. And impatient.

Nauti-craft already did it. So did Joachim Grenestedt at Lehigh. Why aren't all boats using their designs? What, please, is the discipline's, and the industry's, excuse, for this unconscionable delay?

Well, maybe their designs are too complicated. They sure seem that way to me. I'm no genius, and I know suspension is a career in itself, but it just seems to me it can't be that hard. So I throw out a crude and simple design and say, please, why does it need to be harder than this?

I don't understand linkages. I don't know why they need to be there. So I searched and finally found an example of a butt simple, three-point setup that made sense to me. If it puts too much stress in linkages or support members, OK, but millions of mountain bikes have linkages that aren't that much more complicated that align forces in whatever way they need to be aligned to work. Motorcycles, too. Both seem easier than cars, and boats seem easier than all three. So someone who knows about such stuff, please get on it. Is what I'm saying.

 

1.Longitudinal swing arms of motorbikes ( I dont wan't to write about MTB misconceptions , 30 years of riding of somebody phantasy design , 26" wheels , short wheelbase , sick frame geometry and milions of followers)
are not designed to carry much of side load. Your idea of use longitudal swingarms one dragged one pushed is not bad however side loads need to be consider.Also twisting forces . So you need double swingarms or massive stif single swingarms.
2.Point where swingarm meet float is extremely important. How you will find proper place?
3.Connection joint is a Cardan so you need at least ropes limiting maximum deflections .Determining the length of these ropes will tune the suspension.Nose diving float isn't what you want.

 

Weakest point of your design is one point joint connection .
Dragged and pulled swingarms can be done , wide apart , stiff and light double swingarms .
One point attachment of the float is more chalennging:
-point of anchor need to be tested
-you need specific elastokinematics of joint
-you need big twisting stiffeness.

 

Thanks much for the input, @montero. So, side loads--you point out this setup is limited to mostly at straight-line travel, I guess. Not pulling hard lateral Gs from quick turns. So yep, that's an issue, at least it you want to turn fast. The wider the attachment (hinge) at the top, the more bracing you'll have, yes? Like a cantilevered wing. Would that help? Maybe it's a trade-off.

Independent floats should help with handling quartering waves, and that plus free roll should relieve torsion loads when the boat is suspended between wavetops. One hopes. But the width means a flat ride. So more lateral loads, as you can't lean into turns as you do if your thrust is an outboard or stern drive. Would adding, say, a midships skeg or dagger board/centerboard/keel help take some of the lateral loads, and provide something of a pivot to turn on?

I suppose one might use horizontal (or Vee?) foils like ailerons to drive the inner floats down and lift the outer ones up, synched with the rudder. A bit too complex for my application, and draggy. But points to the concept that a fast boat is something of an airplane, as is an F1 car.

An F1 car IS an airplane, in my book, at speed. I don't understand why ailerons (and forward, canard elevators) aren't standard equipment. Let you lean into corners without having to bank turns. Simplifies suspension, maybe. I digress.

On attachment, the thought is that free pitch and roll, in combination with allowance in vertical travel from the suspension, would avoid some of the "spearing" into waves that I gather is a problem for long amas (along with relieving torsion stresses). Shorter, broader floats should help with lower speed planing, and also provide sufficient buoyancy for shallower draft, to float over waves rather than plowing through them at sub-planing speeds. Puts lightness at a premium, and increased windage is a consideration.

Weighting fore and aft--trial and error, in a model. Velcro. Make the attachment well longer than ultimately needed until you find the sweet spot. Weight tending aft, as in any planing boat, to help avoid digging in the nose. Placing the attachments in wells to keep the weight low is an idea from my niece, and I think it's a good one. Nauti-craft 4Play doesn't do this. Good call, niece. Would want self-bailers.

Putting a limit, or stops, on movement in pitch and roll seems a sound plan, and I've thought of it. Might again be a question of trial and error, and speeds and sea states contemplated. Any restriction would seem to add to stresses. Bounding over waves at speed strikes me as most similar to a 4x4 bombing along a rutted road. VERY rutted. So, long travel, very soft "tuning."