Hydroplaning Rowboat

Fair point, I concede. "Advanced" it is not. Poor way of framing it. I'll fix in the next writeup, whenever that may be.

I didn't know that Coroplast isn't light compared to medium tech boats/materials. It strikes me as almost otherworldly light. Flimsy, oh yes, but 2.5 lbs per float is to me insane. It's like air. It's the "power of twinwall corrugation"--to me, Coroplast is an engineering marvel of strength and stiffness to weight, whether it's "new," or "advanced," or not. A yard sign weighs less than two ounces, but they tell me you can build boats out of this stuff! I find this jaw-dropping. Even half the thickness of marine plywood (2mm) would weigh like five times as much, says a little digging and calculator-ing, and would snap, whereas the Coroplast would "just" crease. And the plywood needs paint/epoxy/sealer, and that doubles the weight. No paint or epoxy for Coroplast.

Of course, you don't just fold a soggy "kayak" out of it--you use clever semi-monocoque construction with egg-crate crosslaps and sharp corners and large bonded areas in shear. Integral box beams. Stiffen the seams. Works quite well with paper and Elmers, on model #2. Shockingly well, to me. Stronger than one would think possible. Should be a floppy mess, but it's strong like a brick. Does not twist or bend. Just don't stick a pencil through it.

After all, I started out assuming I'd use 1/8" plywood, and thinking that could actually give me an entire boat, for, let's see...."under 25 lbs." But OK, CF epoxy (or something else?) might just beat "even" Coroplast. Seems fiberglass couldn't compete, but what do I know? 1/16" ply seems iffy on strength, and a lot of work, and still too heavy. A pound of paint or varnish is a pound too much. Skin-on-frame--maybe? But also a lot of work, and "heavy," and I think I want lots of sharp angles and corners to plane. Flat-panel suggested and suggests itself as the way to go. Floats are at present just glorified boxes, but that's exactly how I want them. Not because they're easy, but because I'm at present convinced they're right.

I would love to make something out of CF-epoxy or anything else that would out-light and out-strength Coroplast. I just don't have a prayer of doing it, myself. Never mind whether I could afford it--I have no tools and no space and no skills and no smarts (and no time, and no initiative....). Coroplast can be cut with boxcutters or regular scissors, and FOLDED, and--don't laugh--put together with hot melt glue. They make PP-specific hot melt, fairly amazingly. In affordable bulk--11 lbs for $120. That is filthy cheap, I don't care who you are. Almost worth it just to see if it does what they claim.

Even scissors and folding and hot melt is a stretch for a hopeless all-thumbs like me, but I could almost see myself swinging it. Not an ideal solution, definitely not a permanent solution, but would it hold together long enough for a few runs?

 

I have a book Titled: The 40 Knot Sailboat. It was printed in the 1950s. The author, a navy officer, reasoned that the reason sailboats are slow is that the hull gets in the way. That was a long time ago but he was pretty much co9rrect with his postulate.

We now have some very fast sailboats that are fast because the are supported by hydrofoils. Perhaps you might explore an option of that sort for your man powered record setter. Coroplast is not going to make suitable foils however.

One of our long time members has made a boat, or at least most of a sailboat with a 3D printer. The skins were supported by printed honeycomb backing. The boat was spectacularly light but it was abandoned as a project because there were some problems with compression loading with the plastic.

 

Thanks for the recollection, and digging! I'll try to make some time to look into further. There is a LOT more about oscillating fin stuff on the forum than I was aware of.

 

Yep, I know all about the 40-knot sailboat. Dad was wild about it, at one time. It's the principle behind Sailrocket 2, is it not? So I'm thinking ol' Bernard Smith might have been on to something. Really brilliant insight and design. It's fun to read about it, and see videos.

Did you know Sailrocket 2 was NOT a hydrofoil, though? It was a three-point hydroPLANE. Hydroplane/airplane, really. But not hydrofoil. Three pods skimming OVER the water, not under it. When it was really screaming, the leeward pod would leave the surface. Then the rear one, and it was just skmming on the front nose pod and using the force couple (am I using that term right?) of the canted keel/daggerboard balanced against the lift from the canted sail/wing. The lift actually came from the SAIL, not the submerged "foil" of the keel/daggerboard. It's really fascinating.

That's actually what I'm trying to do, too. Get lift from a "sail"--except it's a horizontal sail, a bit like a hang glider wing. The idea is to try to leave the water altogether. Get juuuuust barely airborne--get the planing hulls like an inch, or even half an inch above the water, with the propulsive, oscillating, vertical foils still churning away underneath. Or failing that, at least let the wings provide some amount of lift, so the area of the hulls in contact with the water is less. Just like Sailrocket 2, and the 40-knot sailboat.

If that were to actually work, at least to a degree, then hydrofoils would be "holding DaggerRo back." They'd be a liability rather than an asset. If that makes sense. If you're trying to leave the water altogether, the last thing you want is to be dragging some hydrofoil lifting structure along beneath and behind you.

The 3D printer idea is very intriguing! Do you know who the member is?

 

I think you can talk to one of them . Such a pilot will definitely speed up your boat .

 

I've spent some time considering the requirements for a slightly different record, broken many times, the distance covered by a human in 24 hours.
Far and away the single most important aspect is the motor, all else is secondary. My task was to come up with an optimum approach to the secondary issues, it ain't easy.

First order, simple and light, every ounce (or gram if you were raised in a rational universe) makes a difference.

Two decisions are required, first how to provide the power and second the minimum drag at design speed.

The record has been held at different times by paddlers or peddlers. I've the pleasure of knowing one of the paddlers, Carter Johnson who is physically suited to the task, a superb athlete and very nice guy. My potential client comes from a cycling background which easily establishes power approach.

Two approaches to the actual design were considered, foil borne or optimized displacement hull. Client liked the foil borne approach after he saw an old video of the original foil borne "walker" from years ago. My concern with the approach is a foil system is real "peaky" EG very good in a small speed range. Decavators pop up foil was an ingenious solution to the issue but not well suited for a 24 hour craft. My preference was an optimized displacement hull stabilized with a steadying foil/skimmer, an approach I've had some experience with.

The project hasn't developed but I'd like to say a bit about putting the power into a driving force. Paddles and propellors have both been used for the distance record. I've long admired a horizonal fin approach after seeing what Mother Nature developed with the orcas. An issue with such for a floating structure is the inevitable up/down component introduces some non optimal vertical oscillation, easily minimized by placing the fin under the CB.

One last issue is optimizing the motion of the horizonal fin. This bothered me for a while because any mechanism under water would seriously increase drag. The obvious solution finally came in that you could have the mechanism above water so the only thing in the water was the fin and a couple of minimal struts piercing the water.

Great probability is it won't be built but it's been an interesting exercise.

 

I'm a mildly interested spectator and I think it can be a good sort of project to push boundaries.I'm not utterly convinced that rowing or paddling is the best approach as both can only provide intermittent power delivery.Pedalling has been mentioned and I think it is worth further consideration,not only because of the uninterrupted power,but it might also allow less windage of the boat plus propusion system plus occupant.A reclining pedaller and a connection to a good propellor via a streamlined strut could allow a reduced frontal area and the strut might be a good attachment point for a lifting foil.Maybe a small trimming foil near the bow and a realisation that it might have a short life in the wrong piece of water... Feel free to ignore or not,as you see fit.

 

Are you a world class athlete or will you hire someone to be the motor?

 

Lots lots of discussion on this topic in the archives, here's a source of some links,

Rick Willoughby's V series boat plans https://www.boatdesign.net/threads/rick-willoughbys-v-series-boat-plans.67288/#post-933565

Look around on Greg's link for the posts on what it takes to break a world record.

I haven't been following developments on the 24-hour record. AFAIK Greg K still holds the record over Carter Johnson set in 2017, and a better designed boat by Rick Willoughby seemed to be in play for that. Even though Carter might have been the stronger engine. Reducing Appendage drag may have been a significant part of that boat's design, which helped. A thin, flexible, unsupported, flexible spring steel, long tail shaft was used on that craft, which provided the lowest possible appendage profile (except for an air prop -0-). I had been using a fiberglass version of that kind of shaft for several years in my own one man pack in boats. Finally was able to convince Rick that it actually worked without wobbling.

Post 53 and 54 on this link,

Prop Shaft Systems. https://www.boatdesign.net/threads/prop-shaft-systems.24636/page-4#post-286133

 

I expect that the stronger the rubber bands, the greater the hysteresis losses. So do you need more than the minimum necessary to return the foils during the recovery phase? Speed would vary across the phases of the stroke, and if drag is proportional to the square of speed, then the average drag of speed varying around a mean is greater than if speed is kept steady. But that might be a smaller effect than hysteresis losses. And it would save you adjusting the rubber bands for power output, which varies with who is rowing, and for what distance.

How do you intend to steer the boat? A rudder, perhaps controlled by tilt of the seat or pedals? Or have separate grips and pedals for each side, so you can independently vary the amplitude of the stroke on each side? I think that is how this boat is steered:

 

No, but I've designed some boats for world class athletes ;-) My experience is with marathon canoe racing. Some of my designs have helped paddlers and a few peddlers win races and set records (a few still standing) in primarily the Texas Water Safari but also the Yukon Quest and the Ms 340.

 

I think the current record is for the longest distance paddled on a surfski, canoe, or kayak in 24 hours is 251.71 km (156.41 miles), set by Sebastian Szubski in Poland in 2019 which beat Greg K's 151+ miles. Records are made to be broken.

As an aside, achieving a Guiness world record is not a trivial matter, the recording and documentation requirements are stringent and expensive.

 

All great input and debate here--great to see! I'll try to respond to posts directed to me when I can make time and if I have anything to contribute. Some discussions seem to have potential to take on a life of their own, and that could start other threads, if any were interested.

Attached and below (?)are drawings with the latest design changes. (Colors not consistent)



Main differences from the writeup are:

1. Change from colinear foil tracks to tandem, to reduce overall footprint area by 2/3

2. Change from narrow spacing between stern floats to "square" layout

3. Wings are now rectangular, no dihedral, (Günther Jörg "Flairboot" inspired)

4. Box-wing, lifting tail proposed for airborne stability

5. Trailing arm and "leading arm," single U-joint attachment point suspension proposed. "Wishbone" bracing courtesy of @montero on this forum (please correct if I’m way off)

6. Reverse rower to face aft, for better weight distribution and momentum shift over pull stroke (courtesy Tom McGuinness, Pacific Tailboats AquaFin™, AquaNova Technologies)

7. "Pull rails" form the gunwales, to define/contain arm pull and assist rower stability

8. Fixed seat, sliding footplate drivetrain (credit to Volker Nolte, “sliding rigger”)

9. Lines/pulleys allow for proper rowing technique: in succession, doubled leg drive (handles against forward stops); trunk lean (handles still against forward stops); arm pull

10. Wing endplates ("tip seals”) to seal to water and mitigate tip vortices

11. Float chine fences

12. Midships float steps, ventilated

13. Provisional midship interceptor at step lip (not shown), (credit to Jürgen Sass, @HJS on this forum)

14. Elastic is now laid along the wing endplates

15. Elastic now incorporates 2:1 block and tackle system for compactness

There are more, like variable foil pitch (critical) and asymmetrical, flexible, reversing camber on the foils. Foldable “stub arms” are proposed to provide support for suspension, as max commercially available length for CF tubes for tracks is 88” (purchased on clearance). But I’ll detail those later.

You may note that multiple attachment points are suggested, as for instance on the tail, to experiment with AoA and lift, and on the strut attachment points, to adjust fuselage ride height.

 

Hi, Robert--thanks for the good input. No, I don't think one needs to use more elastic "charging" force than is needed to return the foils to their starting point. But one certainly CAN, right? If you wanted, you could make your foils small enough, and your elastic strong enough, that you could set it up backwards--pull force just enough to get the foils to the end of their travel but impart negligible thrust, like an archer pulling back an arrow, then release. A slingshot.

But my thought here has been that if you want to try to plane (and maybe "fly"), you want less pulsing and more constant power delivery to the water, so you don't fall off of plane or lose your aerodynamic lift and have to almost re-climb the hump all over again, or at least keep lifting up, dropping down, lifting up, etc., on every stroke.

So, since the foils must be returned anyway, I propose selecting a combination of foil area and elastic strength that would roughly accomplish this constant power to the water. Yes, rowers of different power would need more powerful elastic (you can buy exercise bands of different resistance in sets, quite affordable), and the overall powertrain length would need to be adjusted to "choke up on the bat" for different rowers' pull lengths. Both seat placement and "stops" for both footplate and pull cars should be adjustable to the rower, to facilitate constrained rowing. All quite straightforward and easy to implement.
--
It's definitely not perfect. As you observe, force applied to the foils and speed of the foils will likely vary over the foils' travel, both because of the force curves of the human body and the inconsistent force from the contracting elastic (more at the start, less at the end). Momentum and other factors also come into play.

But the way I'm applying a torquing force to impart and hold angle of attack of the foil is such that it's at least trying to track variations in force and speed over the course of its transverse travel, to present an "acceptable," non-stall AoA over the course of foil travel. This is my proposal for variable foil pitch. Looks like this:

Sorta all kinds of things going on here that I can get into later, but the main point is that I'm trying to use torque (moment) on the, shall we call it, "foil mast," to impart and hold AoA against the "flow" of water the foil encounters due to the combination of being pulled along the transverse track plus the forward motion of the boat. You have to have some way of imparting variable pitch so that you can "sheet in" as boatspeed increases and the "apparent waterwind" the foil encounters shifts forward, or you will lose "bite" and not be able to increase speed no matter how much force is applied. So, variable pitch, not just with boat speed, but over the course of a single pull and a single return. You're providing strongly pulsed input, and this is an attempt to deal with that.

You might note in the drawing that the anchor point of the green "pull line" is closer to the rim of the "pull disc" vs. the red, elastic-powered return line, which is closer to the center of the disc. I'm proposing this because the pull line needs both to apply and hold force against the water while also stretching out and "charging up" the elastic, while the return line needs only to pull the foil and impart torque on the mast. This one's a bit out on a limb, so needs experimentation, but who knows, it might work. Any thoughts/arguments/better ideas welcome. It's trying to do a lot of things at once.
--
By the way, Decavitator didn't have variable pitch on its air prop. Not dynamic variable pitch while underway. It's, um, pretty darn important. You don't want to get towed up to plane, because it's against the spirit of the rules, if not the letter. It's HARD to accomplish. Trust me. But necessary. And it's a big, wide field of opportunity just asking to be exploited. An opportunity to gain an edge.

But as you can see here--don't quit while you think you're ahead. Don't stop. Keep going. Just on the project of foils, I haven't even gone into what I'm trying to get it to do on the "power tack," or the assymetrical, flexible, reversing camber foils. If you can see a way to improve it against the single goal--the "need for (sprint) speed," within the rules--and it's not too unfeasible, DO it. Stack 'em up. Don't stop now. That's my motto. No holds barred. This is war.
--
Steering is an easy problem in comparison, I'd say. Rudder, or differential travel of a foil on one side, or both. The coupled leg thrust from the footplate results in synchronized foil travel, but once you have extended legs and leaned back and are ready for the arm pull, you can pull one side and not the other.

You can in fact just push your legs out and "lock" them there, fully extended, and just use arms. Lock down the leg pull part with an adjustable stop, and you have the flexibility for "arms only" power. Vice-versa--just leave the pull cars/handles against their forward stop, and use all legs. You can use all TRUNK, because I'm tying the back support to the pull cars with a strap:



Lumbar support. Stop using your arms as "passive towbars," and only put them under tension when you can actively move them to contribute to the stroke. Take a rest and use different muscle groups on a long, say cross-ocean voyage. Could be used by para athletes. None of these necessarily contribute to the prime directive, but they're unexpected benefits that certainly don't detract from it, that I see.

Don't stop. Keep going.

 

Yah, this one's a bit tricky. Both hands and feet (and trunk) are occupied, when you're underway. Your entire body is in motion, really. I thought about feet, putting a pivot on the footplate. Maybe? Seat---hmmm. It doesn't move--once you've adjusted it to your liking, you clamp it down with, like a quick-release quill or pin or whatever. It's not a sliding seat boat, it's a sliding "rigger" (actually rolling footplate, but the feet are yoked together). One could let the feet work independently? Hmmmm. I'd be receptive to a good argument on that. That would let you start differentially pulling on one side vs. the other right at the beginning of the stroke. But it strikes me as complicated, and I'm not sure that one might not LIKE to have one's feet yoked together. Rowers do. This is a rowboat. May not look like one, but it is. It is not going to be a pedal boat. Don't think I'll budge on that one.

One thought I've had is to run rudder lines along the gunwale pull rails, maybe above and a little outside. The pull rails and cars are "ergo," in that they allow rotation of the car with the rail as the axis. Stick you hands out in front of you flat, now pull them in. Do they angle up, or even go vertical, when you let them do their natural motion? That.

This:


Useful? Contributes to prime directive, maybe with unintended side benefits? Original? Patentable? Am I going to patent it? (No.) (This, by the way, is the basic design principle of the foil cars, too--round rail, three U-groove wheels. Looks like it comes from a 3-D printer. Surprise! It does. The wheels do, anyway.) Have built tons of these on the model. They work specTACularly. Roll back and forth like greased lightning. Ropes over pulleys, not so bad, either. Just be careful to keep 'em lined up, so they don't frict against the groove. I'm souring on Dyneema for ropes, by the way. Too slippery. Need at least a PE jacket so the wheels turn rather than the ropes sliding.

Not sure how to incorporate these rotating pull handles/cars on rails into an existing design, like a regular rowboat. You kind of have to buy in to a lot of DaggerRo design principles overall, to get the benefit. Guess you better just buy the boat.

Oh--rudder--

So, you run rudder lines above/outside the pull rail that forms the gunwale. Tilt your pull handle up and frict against the pull line. This shortens it (puts a bend in it) and pulls on the rudder at the stern. Don't have to stop rowing, you can just pull with the handle on one side kicked up (maybe past the vertical? Or at any rate, more vertical than you'd ever naturally pull). There's probably a better way, or several better ways, to do it. Wheels? Rollers? Put something on its own little "stalk" off the car? Thoughts welcome.