Maybe reach out to RCTestFlight here on RU-vid? He's done a lot of stuff on hydrofoils, hydroplanes, and similar, both ridden and RC - and is very knowledgeable about propeller design too
It could also be thermal contraction, which doesn't always happen as evenly as you might consider. Can see more obvious signs of it in the delamination of some of the prints
this or warping which with big parts is much more noticeable, when we don't even the expanding foam that might introduce more warp due to the pressure from expanding and reaching 80C
As opposed to creating your design around the quirks and nonsense that the software vendor allowed the programmers to create because they could be bothered to write a decent design spec. No bother with that, give me "clay sculpting" every time. 😁😁😁
@@timcorso6337no, as opposed to proper, sketch-driven, parametric modelling. I deleted the rest of this answer, because I could rant a while. Direct modelling has it's place, but there are other tools that are better for it.
The large flat surface at the back leading all the way down to the props could be causing a low pressure area just in front of the prop and letting air get pulled down to the prop. Re-shaping the motor mounts to be more of a knife edge from the bottom of the boat to the top of the motor might help some. Or try moving the props out of line with the transom. More forward or back just so the props aren't working through all the turbulence of the boat before it's on plain.
Yes he's most likely getting ventilation rather than cavitation. Have a look at an outboard motor design shape, and investigate the purpose of an anti-cavitation plate. Also if you are planning on more of a surface drive prop you need a MUCH higher rake angle like on racing props to help it shed the air off the blade tips.
Awesome job Sam it looks like an awesome design! I think you could put the motors out on a bit of a stalk like 300mm long away from the rear of the boat that you can adjust the angle. Then run surface drive props to get the speed
You need to get the front side of the props into "cleaner" water, away from and/or below the hull of the boat. Longer prop shafts angled downward, with a streamlined support to help hold them straight.
Exactly. They're not pulling enough water from the front side. Either move them out or back farther or create a channel under the hull so they can source the water to pull and in turn push otherwise it's just going to suck.
10:07 Are you sure it isnt ventilation, not cavitation that you suffer from? Looks more like it to me... In which case there are multiple solutions. If you have to run the props that high, you likely would need a different prop design and perhaps also a different power output.
Great video and build. To reduce cavitation of the props you need a cav plate - essentially a plate on the back of the boat that sits just above the props, it'll make a big difference. I used to build ski boats and played around with different shapes, sizes and angles, but in the end given the position of your motors, you probably need something 400mm wider than the hull, and 200mm beyong the props. Good luck, I'd love to see how you develop it.
To reduce the cavitation you need to get the props lower or under the boat to stop them drawing air down from the surface, maybe as an easy adition you could add a flat plate obove the prop location (covering the main area where it is currently drawing air from) as a modification to this hull with minimal redesigning? as you go faster the plate would need extending further foward as it might draw air from each side of the hull.
Thermal expansion and contraction combined with slight imperfections throughout the printing process is why parts aren't lining up, these are huge pieces and when the printers moving around, it only needs a slight imperfection for the problem to exacerbate
With the prints having gaps I can think of two possible reasons: 1. your printer is not assembled perfectly square. On some prints you won't notice as the prints that are supposed to fit together were scewed in such directions that they still fit. But then in other joints those scews add up badly and you end up with the wedge shaped gap. 2. at these sizes even PLA warps. I have a V-Core 3 500x500x500 and I checked it is squared very well. However I still had issues with multipart prints fitting and often the gaps look like they open up towards the edges of the print. This is the higher layers of the print contracting and lifting the corners off the bed (sometimes it lifts the spring steel sheet with it if adhesion is that good). It can also make sides of your print bow inward because bottom and top are held more by having solid layers but in between the hot plastic can shrink more as it cools. Cause 2 is more difficult to solve. - Sometimes it can help to not use the max volume of your printer and rather split your model into more parts with more gaps but the gaps are then small enough to be filled with a glue. - Having the printer enclosed helps a lot too as it prevents unwanted draft cooling but this is difficult with bed slingers. The bed moving along Y axis naturally cools the print as it swings it into fresh air repeatedly. - If the shape has no overhangs like some of the hull sections here you might want to turn off the part cooling fan as well. On such big prints even PLA will have enough time to solidify enough before the nozzle comes again to the same spot to deposit the next layer. - And finally the only way to really be fully dimensionally accurate on such big prints is fiber filled filament. I have tried PETG-CF, PCTG-CF and PCTG-GF (beautiful white look) and they all kept shape that was completely unprintable in normal PETG and visibly deformed in PLA. If you really want PLA for the gluing and such you could try PLA-CF. I never had it but based on how much the fibers helped on PETG I would guess that with PLA-CF your only accuracy limit will be the squaring of your printer. But be aware that you need a hardened nozzle and your speed limit might be a bit lower. For example on my printer I can do 38 mm3/s with normal PETG but only about 30-32 with PETG-CF. The hardened nozzle just transfers the heat less well. Also filaments with fibers are way more water absorbing than the same polymer without fibers. The water seems to creep in along the fibers or something. Drying the spool before you use it improves the results a lot.
Me too, their is a very fine "veil" cloth, a bit of reading and good to go assuming no issues with the 3d printed material reacting. I'm fancying doing this with very thin ply and above, I'm sure I seen plans years back.
The cavitation is mostly caused by the big cylindrical shapes that house the engines dragging through the water close to the water surface. They are creating an air bubble around the props most likely. I bet making a more streamlined nose cone for those things would help or moving the prop away from the thing by putting it on a longer axle is what normal boats do. I also think you'll want a more speedboat like prop, but that's complicated stuff. awesome video
To help with cavitation you need to get the propellers into "cleaner water" away from any wake. Spacing then out will help, but also the to"clean" the wake up by streamlining the back of the boat to allow the water to flow off more"clean"
You can print frame, sculpt hull with some sort of "foam", then fiberglass it all over and remove foam. I think it will by much lighter and more structurally sound.
You will significantly reduce cavitation by reworking those motor mounts. Not only do they have a flat front face plowing in the water, theyre blocking the water from flowing through the prop. Instead they have to suck in water from the sides.
Next time add alignment tabs, tongue and groove sets, bow-tie connection points. This will allow your parts to lock together and self support far better. Bow-tie joints will pull the gaps together. Tongue and groove sets will keep parts straight. Alignment tabs will keep edge transitions between sections to a minimum.
Cavitation is generally caused by props being too high for the application, or disturbed water flow. In this case, I think it is both. Larger propeller likely will help it (enough) though it would have been better if were below the center on pod(s). In the end, if it gets to planing speed, then you'll likely want the props level with planed out water level, or above. The hydroplanes you built is designed on the "3 point" design and are meant for much higher speed than 30. Normally, the boat will plane on the back portion of the sponsons and at lower speed the back of the boat. At extreme speed, they'll nearly just ride the propeller which will be roughly halfway out of the water at top speed. They are a bit different on prop placement than conventional v-bottom boats (where I have a lot of experience with small boats going fast). If larger props didn't help, or help enough, you might also experiment with 'set-back' i.e. putting the motors BEHIND the boat instead of inside. This helps with stability, bow attitude (which may not help much on hydroplane), and overall speed. My 20' Hydrostream needed 8" of setback versus mounting the outboard directly on the stern with prop 2" above center line to hit its max speed of 104 mph. Regarding the fit, fit all the parts together and glue before filling with foam. I discovered a long time ago when I used spray foam behind a door frame that it can expand and greatly flex the space. In my case, the small amount I used was enough to where I couldn't get the door open until I took a saw and cut out some of the foam. It looks like the molds did fairly well, but more internal bracing near connection points will help. I used to have to do that with huge fiberglass subwoofer boxes so they didn't flex under use.
if you want to stick to dual motor as your form of steering you'll need it to be software base because once you get up to speed on plane you'll want any adjustment to be miniscule or you risk loosing plane or loosing control. you also most definitely want your props to be mirrored otherwise you're just slamming the port side of the boat down into the water.
I think the gaps in your 3D prints are actually caused by slight warping in your parts especially on the surfaces that laid “flat” on the heated print bed, due to some temperature differences.
That's a huge endeavor! It sure is satisfying when a plan comes together and works. Nice job. I have to be honest about something. When you talk about that new printer and the insane print speeds, that peeks interest for some of us. BUT, when we see that the printer, as fast as it is, doesn't print accurately, this could be a deal breaker for many. That issue with meeting at the top and bottom, while having such huge progressive gaps in the middle of the 2 parts, is not good. This would be something that needs to be resolved, whether it's slicer settings (perhaps hotend/bed temps, they type of filament used that perhaps expands and/or contracts during/after print or something with the printer itself. The other issue I saw there on several pieces were some layer separation. It looked like total separation, like maybe the filament didn't even extrude, or perhaps the filament does contract and caused that layer separation issue. My printer used to do that too when I first got it and knew nothing about 3D printers or slicers. I finally figured it out and it took a lot of tweaking and mods to my printer to get that issue resolved. One of the tweaks was to reduce acceleration and jerk. The other, main tweak, was to print HOT! I print all my stuff at 235C. This way, the layers are coming out extra hot and just melt nicely into the layer below. I use Cura and I use a feature it has called Fuzzy. I like the texture it creates, but by the way it creates the "fuzzy" texture, it also blends the layers together even better. I never seen layer separations at all now. I'm a guy who likes large build printers. Mine is 400x400x400 and while I've never printed anything that huge, it's nice to know it's there if I need to one day.
😂😂😂 love the good old British humour and spirit chaps . Nice design, discrepancies in the printed parts on assembly may be down to thermal shrinkage and / accumulation of misalignment on assembly and possibly storage before assembly. Maybe print a couple of removable braces in the cad drawing for part stability . Dry fit in larger sections and place on a flat surface and use X/Y axis datum marks an a sheet of plywood. Alternatively print some internal flanges so it can be glued and bolted together. Or an internal stepped flange . Jet drives would be the way to go but I’m just going off the speed and performance of a jet ski and they use jet drives for a reason. Cavitation is probably down to the prop diameter and pitch RPM range . But again I’m just going off what fast boats and RC boats use and I’m no specialist. Put adjustable 2 trim tabs on the stern this may enable it to get on the plane easier. To be fair I could of built a pattern / mold and made a carbon fibre one in the time it took to print and draw this but that’s not the point of your video so fair play . It’s all about having fun while experimenting and educating oneself .👍
That fall reminds me so much of when ‘how to make everything’ fell headfirst into the flooded cranberry field just as funny 😂 ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-whSKmj6oR8Y.htmlsi=5cTpxVscWCksADRP
I believe hydroplanes like to be on plane and usually require a lot of power to overcome their inital faults of be a drag in the water they also use forward hard "fins" to stabilize once they get out of the water since they are designed to take advantage of the moving air goodluck it was a treat to watch
Very cool , we want more cracking vids like this - inspiring others to try science and engineering, and make the world a better place, one 3d printed boat at a time ^^
put your props under the hull where there is less turbulence or modify your hull to streamline the water where the propeller sits to prevent turbulence.
Maybe the easiest way to get rid of the cavitation is to extend the shafts of the propellers. Or othervise moving the motors and propellers under the hull
Warping can happen without an enclosure. Also, larger prints tend to warp. I 3D printed a full size Lamborghini Aventador, and these were issues I saw. Awesome build!
Cool project. Just came to mention that you must not have squared your printers before printing. This shows in your distorted parts. Your motor housing/mount needs to be smooth on the front. It should resemble the front of an outboard engines gearbox.
The expanded foam gives huge rigidity to structure, we used to use 2" thick sheet foan glasses in with glassfibre to make rain gutter for warehouses and such, a man could stand in the middle of a thirty foot length and be lifted by a guy at either end with minimal deflection, the first time I seen it done my jaw dropped!!!!! lol
Thought it was clickbait when I saw the small boat in the beginning. lol BTW, if you dont want all those bubbles, and you want more thrust, you probably need to redesign the impeller system. You should look into buying or printing a jetski type inpeller, and maybe redesign the impeller system so the impeller is inside a small tunnel further under the boat and not so far back and high up. My guess is the bubbles are from the impeller being too close to the water surface, but that is all just a guess. You could probably design a little drop in tunnel with a gate on it without having to redo your whole boat. You could cut out a box section, and drop in the insert.
I had a hydroplane that was given to me years ago. I didn't take it seriously until I started playing with it. I put a 40 hp Evinrude motor on it and soon found out that it was more than enough power and the boat went into violent roll slap. (side to side) I experimented with height of the motor, and found that by lowering center of gravity and putting the prop deeper into the water made it more controllable. These boats ran smaller engines on alcohol back in the day. I hope any of this helps.
You almost always need to shift your weight forward in a small boat like that to get it on plane. Once it's planing you can shift weight back some. You're never going to get going well dragging the ass end through the water like that. Also if there is no fairing on the front of the motor pods to make them hydrodynamic it will create lots of drag as well.
3d printed parts can shrink slightly depending on the plastics used, But what seems more likely to me is that they warped. Especially since you mentioned the foam got up to 80°... It's also possible your printer is not quite dialed in and leveled. You'd have to check the dimensions of the parts as they come off the printer to see where they went wrong
You need to change the location of your props. They are directly behind the flat surfaces at the stern on both sides. This causes a backwash , and will cause your rops to cavitate. If you will place them in the center, and below the stern plate with fins to break up any backwash, it will get the speed you need.
Maybe build it shaped like 2 hulls side by side. With a space between where you can sit to control the boat. Then you can use 1 motor in the middle and make 2 rudders. Locate the rudder brhind the hull. Just like when you buy an boat. Then you can use a bigger motor with more power. Instead of 2 motors.
Probably one way you could've prevented massive turbulence on the hydroplane (specificly the stern, which seemed to be the most inefficient) could be by adding an extra plate on the back which pointed inwards, hopefully stopping back turbulence from happening.
You could have saved quite a bit of time if you just 3d printed non-flat parts of a boat and buy + glue plastic sheets wherever there is flat surface. Nevertheless cool project
This would have been a great time to use plastic pellets to feed your 3d printer, would be a lot more work to start (to get that working, but some have that working), but 40kg of plastic pellets is a lot cheaper than filament, an order of magnitude. @@SamBarker
You’re pods block your flow to your propellers. That’s why normal boats have the motors inside the hull with a driveshaft going through the hull with an only a strut supporting the prop shaft in the water to reduce drag and turbulence to the propellers.
3d printer ~ $500 PLA $17 x 50 boxes = $850 PLA Gloop ~ $35 Expanding foam ~ $75 ~ $1,500 to make a small custom boat frame 🤔 Also like a lot of 3D printing, 3D modeling, and Assembly Wonder how that compares to other DIY methods
@@computermdms considering you can make a plywood hull up in about a day if youve built them before... ffs, i made one from a packing crate. just cus i was too cheap to go buy the plywood sheet....
For your narration I would definitely recommend looking into audacity's nose floor removal, will just help to get rid of some of the background fuzz :)
It might be ventilation and not cavitation. Ventilation occurs when the prop sucks in air. It looks like it might be sucking in quite a bit of air. If it is cavitation, you're going to need to redesign the propellers or lower your output. There's a lot of data on using toroidal propellers online. You could even redesign it to be more like a Jet Ski Impeller where it pulls water in through a tube. Lot's of other options too probably. Add jet turbines above the water. Lol
The classic mistake that all these cool engineering video's on RU-vid make is how does buoyancy work lol. They all have underestimated the mathematical web of buoyancy haha.
The issue of your prints not aligning is due to the auto bed leveling system on the printer. With a printer like the Kobra 2 Max, the large and thin bed on it is practically guarenteed to warp. Becuase of this warping, your auto bed leveling is having to work harder and harder to contour your first layers to the warped bed. Almost all printers with auto bed leveling will also have "Mesh Fade" setting where the printer with automatically fade from the contour of the bed mesh to flat layers (at least if your machine is square) where there are no movements in the z-axis. The problem with this is that your top layer will be flat, but your bottom layer will be just as skewed as your bed is causing the top and bottom layers to be nonparallel. I can tell by the orientation of the layer lines in the areas you had massive gaps that this is very likely the root cause of your problem. An easy way to tell is by checking your bed mesh and what sort of range you're getting from the lowest point to the highest point.
Prop cavitation You need them lower than your back transom. Or the back face of the boat Can mount on little pods lower like an outboard Or in front like an inboard Its not cavitation, but the air bubbles coming in from above But no boats have them back there cause air bubbles And when you get on a plane theyre out of the water
Really nice project, build your dreams ! Heatcreep may cause deformation of parts , look into welding steel to get an idea on solving this ;) Looks like your props are pulling air , maybe due to the shape of your hull. Try repositioning those more to the center or even further out .. keep up the good work and please do not drown yourself XD
Honestly, a combination of factors, printer not being square, pla and prints in general tend to shrink/warp and / or how the model was cut up in fusion. Pretty good build though with everything considered.
You want to put a prop shaft through the bottom of the hull. The pods you have the motors mounted on are starving the props. Look up RC Hydroplanes. I build and race RC Hydroplane boats. You don't want to use twin propellers. Run the two motors through a gear box and one shaft. If you want to get over 15mph it must be a surface pearcing prop and a surface drive. The prop will be only half submerged when at high speed. Or find an ald small outboard and replace the engine with your electric one.
you already know the way to get rid of cavitation and you're half way there. You remove the amount of surface are touching the water... ideally being out of the water planing on the surface with just enough in the water to maintain control.
@@adambundy2639 no splitting or shattering with SLA, so no need to reprint saves time and frustration in the end. SLA is way messier, however. And as you stated, expensive...
@nuchbutter a better choice of filament would avoid any splitting or shattering you speak of. There's literally companies making boats through the FDM process
