I would say in all seriousness; please proceed. If you can put any of this together and make any progress, I’ll be first to cheer you on. And; I am sure it will make an interesting read. If you make a mistake or have to rethink some part of the process, that’s OK. Learn by doing. I would seriously like to see how you do this and what works and what doesn’t. Have a sense of humor. No ill intent meant. No one new to or a regular here at Swaylocks has attempted anything quite this ambitious in a long time. It will be pretty amazing if you pull it off.
You do get a slight smile outta me when I read the stainless hinge part.
Rereading this whole thing and…BINGO! Real good analogy here.
Airplane wings have similar structural requirements to any surfcraft. Stresses in positive and negative X, Y and Z plus our old pal torsion. Impact loading and more. You are not building a moored raft meant for a swimming pool here.
How would you build an unstayed airplane wing? On an aerobatic aircraft? Not something with the performance of a low-end ultralight with what is more or less a lawnmower engine but one of those Red Bull pylon racers. Right. Real Strong.
If you wanted to make the wings fold like, say, the wings on a Grumman F4F Wildcat, would you use cheezy stainless hardware store hinges held to a pretty weak structure component with even more cheezoid stainless ( barely) sheet metal screws? Leroy Grumman didn’t, I assure you. The mechanism he used on the F4F and its successors was gorgeous, from an engineering standpoint. and also Real Strong. And pretty complex.
As for the need for a precision shape - let me run an idea past you.
A surfboard in use on a wave has the use of the force of mgsinA, where m is the mass of the board and rider and A is the angle from the horizontal formed by the board’s path on the wave face. Not inconsiderable, and as it uses gravity, it doesn’t run out. Power, in the words of Jeremy Clarkson. I won’t attempt to reproduce his accent.
Okay, now a paddleboard. Powered by one human. No help from a wave. A racing cyclist ( using a number vaguely remembered from some human powered flight texts, Gossamer Whateveritwas) can produce around 1/8 HP, sustained. Using very well trained legs. Strongest muscles you have, meant for locomoting the human body long distances at a fair speed.
Arms, not so much. Indeed a lot less, well under 1/10 HP sustained. Like, say, somebody canoe racing in the Olympics. For somebody quite strong and in training. The rest of us, less power and for less time.
So, I submit, a well done, precise and efficient shape is of considerable import here.
If you want to go and do something other than merely tire yourself out, say if you want to go from Point A to Point B and back during the reign of the current British monarch, you want to use your very limited power as efficiently as you can, no? A badly executed shape wastes power. A crude shape wastes power. Which you really don’t have to waste.
hope that’s of use
doc…
Thank you very much, Doc… lots of useful things to consider in your two posts. Exactly the type of feedback I was looking for on many of the issues i was concerned about. I had not been looking at this as a monocoque structure I was thinking of the internal members and was worried about distributing the joining forces into them… may have to consider the designs entirely if it is really about distributing the forces into the skin.
I’ll have to do some stretching tests on the fabric (with and without glue); I had not considered how much it might stretch can see that it could be an issue. If the skin is the structure then skin strength is way more critical than I was thinking. I’ve been thinking of skin more like a rugged version of on an old pvc-fabric on a wood frame kayak I used to have. I thought it was mostly about distributing weight and keep out water and ruggedness on impact, not an actual structural contribution.
And before I went full out with the crazy idea I would have done a larger scale test. Since it will be on the water, I expected a large bottom surface area supporting, my inital test was because I was more worried about the more point-loads at my feed. I was thinking more like 30" x30" test set up on 2x4’s 30" apart. Since the strain increases non-linearly with the distance between supports and the water will be a very distributed support I thought the above would be good. . You said 7ft between test support which seems excessive, Am I missing something? EDIT: after more reading I see why you say 7’… since it could be bow and stern on different waves.
Based on your feedback I will have to go back and reconsider my designs and look into consider a wood + foam + skin combination to balance the strength I need near the joint and the weight – e.g. take advantage that I don’t need the strength of wood at the ends, but have to distribute forces into the skin. I’ll have to look for threads on such non-sandwich composite builds and a bit mor ereading on monocoque and semi-monocoque designs.
I do get the issues with efficient shape, but since one of my primary goals is testing out the strength and durability of my low-cost joining idea it was not my primary focus. But I was planning on moderate, but secondary, efficiency considerations in the shaping – it is not going to be a floating brick.
FYI My airplane work was balsa + foam flying wings as awell as skin-on-wood (for RC planes). The foam ones were fiberglassed, where I leaned my dislike and sensitivity. However, the largest was 2m across and maybe 2kg total weight, so nowhere near the stress of full-size planes. It’s why I was asking questions because I know this will have a lot more stress and just don’t know how various materials/approaches can handle it and yes the joint will need a good enough substructure. I’ve seen plenty of threads on folding or bisected boards and the issues they raised as well as reading read multiple patents. It is not just the material but the design of how the forces are spread.
Finally, the stainless hinge is not about providing support for the forces it is about making alignment easy since my joint idea has some details to line up, and precision lining up of large moderately heavy objects is hard without some help.
Back to the drawing board.
Terry
Thanks Johnmellar.
The weight is a major concern. I get lighter is better but have to have enough strength in my design so am trying to find that balance. While it is subjective what do you consider “too heavy”? 30lb? 40lb?
My bad, that was a typo, should have been $41.; I guess it came down a little since I bookmarked it or I included tax or something). I’ll fix the original post so I don’t mislead others.
Actually, what caught my eye was two words: Free Shipping. You might find lower prices on the resin itself, but typically they then charge you for HAZMAT shipping which is outrageously expensive.
doc…
quotes: dr_innovation
Thank you very much, Doc… lots of useful things to consider in your two posts. Exactly the type of feedback I was looking for on many of the issues i was concerned about. I had not been looking at this as a monocoque structure I was thinking of the internal members and was worried about distributing the joining forces into them… may have to consider the designs entirely if it is really about distributing the forces into the skin.
De nada, what we’re here for.
I’ll have to do some stretching tests on the fabric (with and without glue); I had not considered how much it might stretch can see that it could be an issue. If the skin is the structure then skin strength is way more critical than I was thinking. I’ve been thinking of skin more like a rugged version of on an old pvc-fabric on a wood frame kayak I used to have. I thought it was mostly about distributing weight and keep out water and ruggedness on impact, not an actual structural contribution.
Again, BINGO. And again, an aircraft wing is a good analogy to the kayak, a framed, fabric covered ( with either a heat shrink fabric or doped fabric) structure where the fabric in tension and the framing in compression provides a major component of the stiffness and indeed the structure. . As it is tensioned already, well, fabric stretch isn’t such an issue. You might want to see if that fabric you have will heat shrink to any extent.
I will note that many fuselages also were made that way, which gives you a point to proceed from if you wanted to. The tech is a century old, it’s been largely debugged…
And before I went full out with the crazy idea I would have done a larger scale test. Since it will be on the water, I expected a large bottom surface area supporting, my inital test was because I was more worried about the more point-loads at my feed. I was thinking more like 30" x30" test set up on 2x4’s 30" apart. Since the strain increases non-linearly with the distance between supports and the water will be a very distributed support I thought the above would be good. . You said 7ft between test support which seems excessive, Am I missing something?
Yeah, to begin with, I’d want to test to destruction. Early successes tend to lead to unfortunate places. Failures and the analysis of them you learn a lot from.
Now, even on a lake, in use,lets say Joe Jetski goes by, or his brother in the cabin cruiser. If the wavelength isn’t a lot more than the board length, at some time you are gonna have float at the ends but not the middle. Unfortunately, in the middle is you, Mister Point Load. Or, just the opposite, a wave ( or wake) breaks at your feet, multiplying the point load. You can, I am sure, come up with a lot of similar ‘oh damn’ scenarios. what happens if…
In aircraft engineering and naval architecture/marine engineering there’s long lists of what you should and indeed are expected to consider when putting the plans together. There is no such field as surfboard engineering. It’s all rule of thumb. And a lot of broken boards. Which works, but me, I like things I can throw numbers at.
Based on your feedback I will have to go back and reconsider my designs and look into consider a wood + foam + skin combination to balance the strength I need near the joint and the weight – e.g. take advantage that I don’t need the strength of wood at the ends, but have to distribute forces into the skin. I’ll have to look for threads on such non-sandwich composite builds.
Or foam/foam/skin. or… again, say, a foam aircraft wing. If you’re using Aerolite or similar, you might well use different densities of that foam depending on what stresses they are subject to at varying locations…
I do get the issues with efficient shape, but since one of my primary goals is testing out the strength and durability of my low-cost joining idea it was not my primary focus. But I was planning on moderate, but secondary, efficiency considerations in the shaping – it is not going to be a floating brick.
Well, the good news is that thin straight grained wood ( not plywood unless you get real lucky) tends to bend into a nice, fair hydrodynamic/aerodynamic curve. It’s kinda inescapable. Which is why wooden battens were used in ship design and aircraft design, viz the wings on a Supermarine Spitfire. It’s also why learning/developing the ability to see that fair curve is a big part of a traditional boatbuilder’s apprenticeship.
As well, you’re not exactly doing a straight cost-benefit analysis here. Or, if you like, you need to move the pivot on that seesaw, balancing efficiency and expense of construction against efficiency and energy expenditure in use and giving the latter more leverage.
FYI My airplane work was foam flying wings and skin-on-wood RC plane wings. The foam ones were fiberglassed, where I leaned my dislike and sensitivity. However, the largest was 2m across, so nowhere near the stress of full-size planes. It’s why I was asking questions because I know this will have a lot more stress and just don’t know how various materials/approaches can handle it and yes the joint will need a good enough substructure. I’ve seen plenty of threads on folding or bisected boards and the issues they raised as well as reading read multiple patents. It is not just the material but the design of how the forces are spread.
Exactly. Look, model A/C are a perfectly valid testbed. It’s just that you need to have your scaling nailed. Same deal with tank testing model hulls. Water/air interface vehicles like surfcraft get REALLY interesting. MIT does a series of courses on the subject, department of Ocean Engineering as they call it now, in my day it was Naval Architecture/Marine Engineeing…
I will note that, again, there haven’t been any successful folding boards that I know of, some worked for a while but fatigue issues or whatever eventually led to failure. It’s a technically difficult problem, doing such a joint in such a way that it uses simple materials or off the shelf components and put together by somebody with a skill level just north of a monkey.
On a wild hair- consider Japanese timber frame joints. Might come to nothing, but might be some ideas there.
Finally, the stainless hinge is not about providing support for the forces it is about making alignment easy since my joint idea has some details to line up, and precision lining up of large moderately heavy objects is hard without some help.
Back to the drawing board.
Terry
(chuckling) wayull, this is why I took courses on Visual Thinking and Design and ‘brainstorming’ as core subjects in Eng school.
It is little understood, just how intuitive engineering is. Good engineering, that is. You build a concept in your head, mess with it, onwards and onwards to where you have something you can put on paper, build, test. Not just engineering, the late Richard Phillips Feynman was a master of it.
hope that’s of use
doc…
So many things wrong with this post.
You say this is your first build, and you want to build a 2 piece composite sandwich SUP.
Biggest issue will be creating a 2 piece SUP board. Even the best board builders have problems building multi part boards. There are at least 2 companies selling 2 piece boards. The system for locking the 2 halves together is patented. I’m currently trying to create a multi piece board, and it is not a simple thing to do. I’m on prototype 3 and I haven’t even gotten to the point where I have a viable system (different from anything already patented).
Using poly resin will require a poly type of foam. You will have isses with PU resin and EPS or XPS foam. You will need to be 100% confident that XPS or EPS foam is sealed before attempting to use PU resin.
The current price for surfboard epoxy from Fiberglass Hawaii is about $180. I don’t know what others are charging, but if you use a boat resin, you will need to paint it with a UV protective coating.
Using the polyiso foam… it’s heavy.
I’ve made dozens of Composite Sandwich boards using many different combinations of core foams and skins. Using any type of wood other than Balsa or Bamboo veneer will make it heavy. I’ve used thin Luann doorskin for one side of a 7’ board and it was much heavier than I expected. Paulownia wood is noticeable heavier than Balsa, but it is good in salt water.
I made a 8-8 SUP with XPS and EPS foam and a balsa deck, it’s heavy, but not terribly heavy. Wouldn’t want to walk too far to get to the water.
You’ve been given a lot of good advice, but seem to have all the answers for why it’s not good advice for you. Check out the Sunova sight, they sell exactly what you want.
Thanks for the feedback. And I have been considering what I’ve learned here and am already reworking the design based on Doc’s feedback.
I am aware of the lack of great solutions and a three commerial products. I have read through the many existing and prior patents including US8469756B2 licensed to Compact Carbon which is used in the Sunova 2 piece board. As a inventor with many patent’s that is the part of the process I understand well. Part of my goal is building a test board for evaluation of variations of my a potentially patentable design for the connection. I want to do it low cost, as I do many of my design prottyping ideas since many of them fail to be viable so don’t want to spend a ton on the learning. My other goal is evaluation of recycled or low-cost materials which could be useful even if I fail in my connection designs and have to fall back to an estabilished two-piece or even one piece design.
Wht do you consider heavy? I’ve seen multiple wood boards in in the 30lb range. I’m not really protytping a final board design but still want to aim to be reasonable.
Awsome feedback doc… Cool that you took visual thinking and design in your ENG degree. Not enough places teaching that stuff in engineering. I happen to teach innovation accross many majors (including engineering), where we do a lot of it ;-) I’ll have to check out the MIT courses; I did just go through Daniel Carter Beard’s classic book on boat design, but there is absolutely nothing on foam-based building ;-( I was planning on using a board-based shape curve for the hull shape, just maybe pure displacement not a rocker which is harder to get right.
I had just edited my post as to why 7ft testing made sense given waves, I should have seen that befor eposting, but have been spoiled by boarding on lakes that don’t allow power boats or at least sections that don’t allow them.
I did the 30" untreated foam test with 4"x4" griding without top or bottom surface with 100kg load with a bit of a hop – it deforms right on the edge of the 2x4, which means it will absoutely take signficant reinforcement from the “skin” if used. Next test will with skinned on top/bottom with skin only on the joints in the grid (which is a lot less material/glue). My foam is only 60" so I’ll do my next test at that with.
I did stretch test this evening as well, without glue, and a 3cm wide strip 25cm long stretches by about .5cm under a 100kg load (me hanging on it), so about 5%. Visibly it seemd it was mostly the fibers in the weave moving/tightening which glue/poly would reduce.
Thinking of it as semi-monocoque design and reading more about that, has been very interesting as I try to thinking of how to distribute the forces into the skin with some ideas I’ll have to test in small scale first. My orginal design was distributing into the stringers as structure, I think I can expand on the core idea but am not sure how much the stringers can distributed into the skin without testing, especially with foram since the stringer might just delam from the stringer. Not sure how I can test that without going full size – and since will likely depend the materials. Though a lower fidelity prottype with PMF would be okay if it works, a failure with PMF will not mean the connection fails, and I may I may get stuck doing resin if I really want a meaningful test. I have to consider the tradeoffs of needing to remove and resand to apply resin… So much to learn…
quote…dr_innovation
Awsome feedback doc… Cool that you took visual thinking and design in your ENG degree. Not enough places teaching that stuff in engineering. I happen to teach innovation accross many majors (including engineering), where we do a lot of it ;-) I’ll have to check out the MIT courses; I did just go through Daniel Carter Beard’s classic book on boat design, but there is absolutely nothing on foam-based building ;-( I was planning on using a board-based shape curve for the hull shape, just maybe pure displacement not a rocker which is harder to get right.
Y’know, if I had to do it all over again, I would have gone on in school and wound up teaching, Probably philosophy and history. Philosophy and history of science and technology would be right up my alley. Maybe in my next life. Assuming I don’t come back as a grapefruit or something.
MIT has a lot of their courses online, for the general public to access. Which I mean to get to, right after I invent the 72 hour day.
When I think of the name Daniel Beard, I think of Dan Beard, the guy who wrote over a century ago about woodcraft and the like, one of the founders of Boy Scouts in the States. .Indeed, I think there was a bark canoe in those books someplace.
But for boat design, I’ll suggest Skene’s and Lindsay Lord on planing hulls. Ummmm, as regards structure, I think some aircraft construction and design texts would be more on point, composites, especially higher tech composites in boat design rather lag behind aircraft until you get to the deep black methods used in very expensive race boats.
I had just edited my post as to why 7ft testing made sense given waves, I should have seen that befor eposting, but have been spoiled by boarding on lakes that don’t allow power boats or at least sections that don’t allow them.
I saw that. See, thing is that while you can optomise for your flat water , the people who would wind up as your customer base will want to play in the ocean and at least think about surfing the things. For flat water, modelling your hull on something like an Olympic racing canoe would work well, but for surf, no. Plus, while a flat water human powered boat is gonna have to be a displacement hull, anything surfed will be a planing hull, inescapably.
I did the 30" untreated foam test with 4"x4" griding without top or bottom surface with 100kg load with a bit of a hop – it deforms right on the edge of the 2x4, which means it will absoutely take signficant reinforcement from the “skin” if used. Next test will with skinned on top/bottom with skin only on the joints in the grid (which is a lot less material/glue). My foam is only 60" so I’ll do my next test at that with.
Y’know what? I’d try something fairly long, let you experiment with joints in the foam grid and in the skin. I’d suggest that a scarph joint as is done with plywood boats, glued, would be the way to go, stagger those, I might even make up long pieces and cut to length as required. Skin both sides, easier that way overall, put a camber in the top which aids stiffness a lot.
What I’m leading you to here is a foam-sheet skinned structure with foam formers in it, glued together, and a fairly rugged skin on top of the foam sheet.
I did stretch test this evening as well, without glue, and a 3cm wide strip 25cm long stretches by about .5cm under a 100kg load (me hanging on it), so about 5%. Visibly it seemd it was mostly the fibers in the weave moving/tightening which glue/poly would reduce.
As I mentioned, I would try hanging a weight from it and having at the stuff with a hair dryer or heat gun, see if it will heat shrink any. There are similar fabrics- well, I think similar- which are used for aircraft fabric and for things like rowing shell decks on older shells, nice stuff. 5% elongation sounds about right.
Thinking of it as semi-monocoque design and reading more about that, has been very interesting as I try to thinking of how to distribute the forces into the skin with some ideas I’ll have to test in small scale first. My orginal design was distributing into the stringers as structure, I think I can expand on the core idea but am not sure how much the stringers can distributed into the skin without testing, especially with foram since the stringer might just delam from the stringer.
BINGO again. Stringers are both overrated and overhyped. Which is heresy in the surf biz. I have seen broken boards where the skin failure (and thus the break) was triggered by a stringer breaking and compromising the skin, which tore from there and then the board broke. The board very likely would have flexed and recovered without that stringer and done it just fine. Likewise, abrupt transitions make for some ugly stress points. Consider the DeHavilland Comet.
Not sure how I can test that without going full size – and since will likely depend the materials. Though a lower fidelity prottype with PMF would be okay if it works, a failure with PMF will not mean the connection fails, and I may I may get stuck doing resin if I really want a meaningful test. I have to consider the tradeoffs of needing to remove and resand to apply resin… So much to learn…
Ahmmm, full size test articles are good, for testing materials and methods. And you can do them cheap and cheerful. Best of all, you can be testing one thing at a time rather than several ideas together.
Yep that be the one I read… I figured I wanted to start old school. I have a few others but none had what I was looking for. I may try the areo community for better sources, especially we have many faculty in that space.
Yeah I strated realizing that while the paddleboard market is much larger than surfboard, if its designed for both paddleboard and surf the market is of course larger and that many paddleboard might still want to think they will use it in surf as most paddleboards are closer to surf designs than displacement. I only started thinking about moving forward with the design idea after I saw the Oragami Paddleer (https://www.origamipaddler.com/) did 3.8Millon on kickstarter. I was impressed with their effort but felt it was too small that at least two of my designs could be made cheaper/better. But they showed there is clearly a market. Maybe continuing to shape my vison of the space their videos are also all relatively flat water.
With respect to the foam-board idea I realized yesterday, as glue was drying on some peices, that they seem softer while I was adding fabrick to the back side and the glue was drying. And then it hit me that they are pretty strong a 3/8" because they have paper + clay glueed on both sides, and when paper/clay gets wet it looses strength. After it dried it was again stong but that hinted that the glue for the paper/clay was not water proof. I submerged a piece for 15min and its very weak and the glued on fabric is easy to remove. So that whole crazy idea is now dead and a small leak would potentially destroy the strength). I might reconsider the grid idea using coroplast (corogated plastic), e.g. which can be upcycled from the next set of election signs that are everywere in November. Its difficult to bond but quite strong on edge, light and easy enough to cut into a grid, but not clear how I could transfer energy from it to the skin if I cannot get a good glue bond.
I went and reviews the existing patents an as I thought I recalled they are all distributing the energy of the joint into the middle of the board. Distributing into the skin is definately more complex since near the joint the skin will be weaker becuase it must turn down the face of the joint and the bend decreases strength along the direction of the bend. I’m sure those companies tried some ways so that means it is non-trivial. Its really too bad I cannot model any of this stuff with my Cad tools (Fusion360). Might have to try Inventor or Solidworks and see if they can. Way too many ideas and not enough experience to just want to build and test the surface connection.
Thanks again doc…you saved me a ton of trial/error mistakes. I may not have much to report until i gather some materials for testing so tread may go quiet. Maybe I’ll get some students to work on this in the fall who are trained Mechanical Engineers.
Regarding weight limit, I.E. “Too heavy” - It really depends on a variety of factors. Haw far will you have to carry it to the water? How steep is the trail? How strong are you?
For me and where I’m likely to surf, a 30 lb board is about all I want to carry. Lighter would be better.
quotes=dr_innovation
Yep that be the one I read… I figured I wanted to start old school. I have a few others but none had what I was looking for. I may try the areo community for better sources, especially we have many faculty in that space.
Wow, blast from the past defined. But not all that relevant. Look up ‘folboat’, you may find it interesting and more on point.
Yeah I strated realizing that while the paddleboard market is much larger than surfboard, if its designed for both paddleboard and surf the market is of course larger and that many paddleboard might still want to think they will use it in surf as most paddleboards are closer to surf designs than displacement. I only started thinking about moving forward with the design idea after I saw the Oragami Paddleer (https://www.origamipaddler.com/) did 3.8Millon on kickstarter. I was impressed with their effort but felt it was too small that at least two of my designs could be made cheaper/better. But they showed there is clearly a market. Maybe continuing to shape my vison of the space their videos are also all relatively flat water.
Gee, that’s…hideous. Don’t wanna know what it costs. If I was going someplace and wanted to go paddling, I’d rent one, there. But that’s me. Spending silly money for a folding rotomolded beach float, no. I don’t care if it fits in the overhead luggage compartment. For that matter, that inflatable you have already is a better setup by far.
With respect to the foam-board idea I realized yesterday, as glue was drying on some peices, that they seem softer while I was adding fabrick to the back side and the glue was drying. And then it hit me that they are pretty strong a 3/8" because they have paper + clay glueed on both sides, and when paper/clay gets wet it looses strength. After it dried it was again stong but that hinted that the glue for the paper/clay was not water proof. I submerged a piece for 15min and its very weak and the glued on fabric is easy to remove. So that whole crazy idea is now dead and a small leak would potentially destroy the strength). I might reconsider the grid idea using coroplast (corogated plastic), e.g. which can be upcycled from the next set of election signs that are everywere in November. Its difficult to bond but quite strong on edge, light and easy enough to cut into a grid, but not clear how I could transfer energy from it to the skin if I cannot get a good glue bond.
Use something other than that glue. Polyurethane varnish, for instance. Not the water-based stuff. the good stuff. A thinned polyester resin. Krylon spray paint. Lots of options. Might well stiffen it up to where you don’t need the cloth reinforcement.
Corrugated materials- you ever hear of the XB-70? North American built it, big supersonic bomber, canard and delta setup. Anticipated SSTs . Technically interesting. But they used something in it called honeycomb aluminum, essentially aluminum foil done in the pattern of beehive honeycomb ( hence the name) , used it for the inside of skin-honeycomb-skin sandwiches for a lot of the fuselage and wings, maybe bulkheads and formers, lots lighter than plain metal of equivalent stiffness. The methods they used to make and join said sandwich would be applicable.
I suspect that honeycomb aluminum went away when they came up with better and more heat-resistant foams.
On the other hand, I think (looked it up) that coroplast is polypropylene. Not easy to stick it together, as you also find with most thermoplastics. . The heavier solid ones you can weld, but this, prolly not.
More- yeah, recycled materials are great. But if you want to build a bunch of them you may have problems. Availability and so on. Likewise selling plans, etc. More on this in a bit-
I went and reviews the existing patents an as I thought I recalled they are all distributing the energy of the joint into the middle of the board. Distributing into the skin is definately more complex since near the joint the skin will be weaker becuase it must turn down the face of the joint and the bend decreases strength along the direction of the bend. I’m sure those companies tried some ways so that means it is non-trivial. Its really too bad I cannot model any of this stuff with my Cad tools (Fusion360). Might have to try Inventor or Solidworks and see if they can. Way too many ideas and not enough experience to just want to build and test the surface connection.
I have been meaning to mention something- look, you can patent pretty much anything. I think they now exclude perpetual motion machines and similar impossibilities, but otherwise practicality isn’t necessary. At a later time, if you want to patent yours and defend said patent, fine.
Now, I have come up with a lot of things for things I was in, shellfish aquaculture for instance. It was suggested that I patent some of them, but the expense of the patent and defending said patent way outweighed the possible income from it. So I released them in to the wild, as it were. Instead, I got R&D grants to come up with them in the first place. With any luck, this won’t apply to your setup, you’d be making a lot of 'em, but always worth considering .
As well, CAD is nice, but distracting. How many Really Good Things started out on bar napkins? Unless you have access to something like Boeing uses, that can calculate stresses, I’d hold off on CAD.
Thanks again doc…you saved me a ton of trial/error mistakes. I may not have much to report until i gather some materials for testing so tread may go quiet. Maybe I’ll get some students to work on this in the fall who are trained Mechanical Engineers.
A cautionary tale or two- and a little bragging.
Friend of mine is a marine biologist, specialising in shellfish aquaculture. And he had the ME students at the college he professed at do a project for him, a solar powered rig, a float that you put tiny shellfish seed in and it would run seawater through it and they would grow, grow, grow.
It was a classic school solution, lots of batteries, impellers, panels and black boxes. Needed a LOT of pumping capacity, lifting water about a meter to the tanks the seed was in and so on. Calculated to a fare-thee-well. Expensive, heavy, kinda fragile considering the environment it was in.
I got a R&D grant to engineer something from sawmill pine to do the same job. Run by tidal current, cheap and cheerful.
Likewise, Eng school. I was in my late 20s at the time. Manufacturing Engineering 101. One project I got was cast iron segments for an old-school steam radiator, one line did in and out, condensed steam gravity-flowed back to the boiler, I’m sure you have seen them. Hollow-cast iron, some sharp corners, you’d bolt together a bunch of them to make your radiator. Neat.
So I gave them the school solution. All good, I knew my stuff, then., But then I redesigned it so it would instead be simple sand cast non-hollow-cast identical clamshell-like halves that would also bolt together to make the radiator segments, it drained better ( no standing water at the bottoms of the segments), no sharp corners, and be cheaper in every way.With the ‘why’ on all that. Got an A on the paper, also the TAs asked if they could make copies. Flattering, it was.
In any event, yeah, ME students are great, but look for the ones who are not afraid to think outside the box. Or the school solution.
doc…living outside the box.
As for weight, I think 30lbs is way too heavy for me. For today’s standards, a 20 lb board is heavy.
It may not be a problem when you first get to the beach, or wherever you plan to paddle. It’s a problem when you are done and tired and then have to carry the wet board back.
I use recycled foam and wood for my builds. I have gone out and harvested, dried and milled Wiliwili wood which is light like Balsa, an Agave like wood we have here and I bought a storage shed of model airplane balsa from the widow of an airplane builder. I’ve used thin veneers bought online, and large 4’ x 8’ sheets of thin plywood as well as 4’ x 8’ woven Bamboo sheets. This is why I can say the Balsa is the lightest, but the woven Bamboo is also light and very strong.
I can make a blank for about $10, but it requires a lot of work cutting and gluing up foam, and then the shaping takes a lot more skill. Glassing costs have gone up quite a bit since the last time I bought supplies, pre covid. I used to be able to make a complete board for about $125 USD, and only $10 was for the foam. The fin boxes and fins are a big cost, so I even make my own fins using G10 panels, or the excess glass I have from making boards.
I’ll be watching to see where you end up with this. I hope you are sucessful, but it will be a very challenging build.
Thanks…
I’ve seen some of your beautiful wood builds in threads, e.g. I bookmarked https://www.swaylocks.com/forum/86657/home-depot-compsand-build. You are very talented. Very cool that you are doing so much with recycled materials.
Today I went looking for CAD models of surfboard shapes as my current cad model is displacement and if I am going to do semi-monocoque modeling I’ll start with a more standard board shape. When I went looking I found there was an interesting competition for portable boards. THey are not “foldable” but are portable.
https://grabcad.com/challenges/portable-stand-up-paddle-board-challenge/results
You might look through that to see if it gives you ideas you might adapt for your portable build. Most are very “3d printer” centric ideas but something might be adaptable.
And one of those had an idea very similar to one of my designs with double-ended large “screw” elements to bind/hold the pieces together (https://grabcad.com/library/4-piece-paddle-board-with-coupling-1) so my version of that idea may no longer be patentable even though my idea ha some advantages form a patent view they might be considered obvious… Might still want to try it but that definitely lowers the potential value of that design. But also that design does not do much to transfer energy to the skin, its into the frame behind the connector.
Oh man, this is an awesome thread. I’m not going to copy what the others have previously warned, although I agree with them. Instead, I’d like to ask some questions: why displacement bottom? I’m picturing rounded bottom which are usually easier to tip.
Also, why don’t you just build a smaller model version for your first go around?
As for McDing; listen to him. He is right on many fronts and I’ve learned a lot from him. However, he can be a snarky twit at times and he’s not the only one here you should listen to.
In an earlier response you made a comment about going over to boatbuilder.com (or something similar). I for one think you should go over there AS WELL as continue posting here. I’d like to read what their comments would be.
I was thinking displacement because it cuts through the wave instead of getting pounded by them so less stress on the joints. It is why many ships are designed to cut not plane, e.g. the well-known Axe design for some ships. Since I do mostly flat water (e.g. check my profile pic), not surf displacement designs are also efficient and much easier to build since they don’t use rockers but a large flat bottom. Displacement is more about the bow shape than the bottom… can still have a nice stable flat bottom in a displacement – many (most?) race paddleboards are displaced with flat bottoms. However, I’m not reconsidering the market size and most of my design ideas.
I do (and have done some) small tests of components of the design but the stresses are hard to model and don’t scale so there many limitations in such small-scale learning.
The problem on boatbuilder.net is there is just not near the amount of “board” design. I’ve done a good bit of reading there but I wanted advice about boards not dingy/canoes and sailboats. I may still go there but want to think deeply, do more read and redesign based on what I learned here. I may join thereafter I refine the idea, especially if it is wood-based.
Shark Country has made boards out of scrap pieces of foam etc. Heed his advice.