RC Laser Sailboat Rudder & Extension Sleeve & T-foil

prusaprinters

This project was started by members of a local RC yacht club. Based on their handmade rudder prototype and measurements (plus a slightly used stock rudder), I produced some CAD models. Currently, I am producing a couple of test prints for them to try building up along with a finished sleeve so they can see how the rough surface of the print becomes baby-butt smooth! Their idea is that the larger rudder surface area will make a better performing match for the light air A-rig on the RC Laser. The larger sail pushes the nose of the RC Laser down, lifting the stern and causing excessive heeling, which decreases the amount of rudder in the water to control the boat. Plus, the longer rudder can help with general maneuvering. I thought a slip-on conversion would allow anyone to try the new rudder without permanent modification and make future design changes easy to implement. Further, I wanted to keep the stock rudder look and feel. The original is designed for toughness, not razor tipped performance. So, the sleeve takes its design cues from the original. It is not designed to be "better" than the original rudder, only "bigger", if you get my drift. Next, these prints will head back to the club members for building and real world testing. Then, we will see where it leads from there! *UPDATE* The slightly longer sleeve does help overall performance, but does not fix the issue it was designed to correct. Once the bow starts to dive and it heels hard, you are going to lose rudder authority. Maybe it needs to be even longer, but that means more drag with minuscule benefit. *UPDATE 2* I tried a T-foil rudder. Theoretically, this helps keep the back end of the boat planted and the rudder in the water. This may need more testing. It works to a point, but there does not seem to be a wide wind range that it is useful. Too slow and it holds the boat down TOO well, feeling draggy. Too much wind and the boat overpowers the T-foil anyway and nosediving and heeling starts up again and you are back where you started. As the wind gets stronger, you just need to adjust your sail, your boat handling, or jump to the B-rig, which does not need a fancy rudder. You could go down the rabbit hole forever re-working this T-foil design, but it just does not seem worth it. Which design is best so far? The rudder extension sleeve is not that bad at all. I think it helps the boat the most overall, even if it doesn't 100% fix the original issue. The T-foil only helps at a single wind speed, a speed which is just under the performance limit of the A-rigged boat and the increased drag Is a hindrance at slower speeds. Although the T-foil is SO COOL LOOKING, this ain't a beauty contest! After testing both rudder sleeves, I don't think an upgraded rudder can fully cure the performance issue. It is the design of the boat needs to change to match the longer rudder! :) A simple rudder sleeve to help folks at the club level keep control during a crowded regatta is one thing, but a hull redesign of a well-established, scale one-design class is not going to happen! Even though this was only a partial success, I learned a TON doing this project that I will apply down the road. Obviously, this is a local experiment and is not a class-approved modification. ;) • Some details for folks actually attempting this print • This print is designed for VASE MODE ONLY. No infill, no tops and bottoms, and a single wall. It is not a hard print, once you get your settings ironed out, but don't expect a perfect fit out of the box. My printer is not your printer! I use eSun PETG filament, with a 0.80mm nozzle and 0.50 mm layer height. It is a tough filament, especially in a chonky vase mode print done right. It quickly gets even stronger with the epoxy coating applied and stock rudder inserted. The nozzle temp is 260º C and the bed is 75º C. Fan on after Layer 2. A 6mm brim is a must for bed adhesion. You need very high nozzle temps to get maximum layer adhesion. This part needs to be tough. If you can break the print bare handed, you need more nozzle heat. Here is a good trick in your slicer for this particular sleeve style of print. If you use Cura slicer, give the first layer positive horizontal expansion (or whatever your slicing software calls it). This results in increased "elephant foot" on the outside of the print, which you usually try not to do, but shoving that foot further out will make the interior wall flush on a vase mode print. This flat inner surface is just what you want for a slip-on print. When printing this part, just do some test prints of the first 10mm of the rudder skin base and use it to check for size and do some fine tuning of your settings until it is a friction fit that snugs up well on the last 6-10 mm of the stock rudder. Once you have the print scale sorted, then try the full prints with your adjusted settings. Also, there is a full height STL version presented just for kicks, but it will not print well in one tall piece. It will start to wobble and look like crap after a 120mm or so of printing. Also, these prints are mirrored STLs combined into one model. So you may see two entities in a single STL. Most slicers will automatically merge adjacent STLs for printing, but yours may not, so look out for that. Cura has no issue with these models. The tip and base halves, printed one at a time in vase mode give the best result in the end. The short sections do not get too tall before wobbling sets in and the surface quality starts to break down. Putting them together is quite easy using the original rudder as a gluing jig. Pic 1. Showing sleeve on rudder, glued up, but not shaped or coated Pic 2. I don’t think of these as failures, just “partial successes” :) Pic 3. Left, fresh off printer Middle, XTC coated and sanded to 320, Right, stock rudder Pic 4. XTC3D fresh coat, literally dripping wet, as it should be. Pic 5. Showing the resulting surface finish. Pic 6. T-foil Rudder Print Settings Printer Brand: Creality Printer: Ender 5 Rafts: No Supports: No Resolution: .5mm Infill: 0% Filament: eSun PET-G clear Notes: More RC Laser info: https://www.theamya.org/boats/rclaser/ https://www.intensitysails.com/racolasa.html https://www.outthere.com/rc-laser/ Post-Printing You should do most all the post processing work with the sleeve on the rudder. It helps the sleeve stay aligned during glue-up and keeps it from overly flexing and even breaking during the rough filing and sanding. It also makes a great handle during sanding and epoxy application. Once you have prints that fit the stock rudder, trim off the brims, but do not trim them flush. Leave a half millimeter of the brim on the prints. That tiny lip will help you during gluing and surface finishing. Tack the leading edge joint with flexible super glue. Then tack the trailing edge joint. Lastly run a bead of flex CA down both sides of the join. Be sparing with the glue so it does not leak inside and bond to the old rudder. Use accelerator to help it cure quickly and not get spread around. That bit of brim gives you more area to work with during glue up. Use a med/fine metal file to remove the high points and clean up the overall contours of the print. This should be a rough cleaning and shaping, but do not use a wood rasp! Control the heat buildup as well, so do not use power tools. This is the time to file 99% of the rest of the brims off the print. As you file and sand you will see the brims start to disappear and merge with the surface. If you work these brims down slowly, they give a very good indicator of how evenly you are working the whole surface. You shouldalmost not pay much attention to the brim near the open edge, it will get worked away as you file and sand the rest of the skin. Hold the rudder up at angle to the light and check for even surfaces and scuffing. You can use a rougher sandpaper her to, but you should be careful about rough grits scarring the plastic surface of the print if you are going for a clear finish. In the next set of steps items 1-3 should be done quickly and WITH NO ATTEMPT TO FULLY FAIR THE SURFACE. There should be dips, bands, and ridges that have not been removed. Do not worry about them. You should not have spent more than five minutes or so each at step 1-3. If you have scarred the print, don't try to file it out, it will get filled. Use medium 120-150 grit sandpaper and a flat hard sanding block to further refine the shape. Keep this hard block constantly rolling over the curves as you sand so you don't create large flat spots. Switch to a 150-180 grit and a sanding pad with some give to start rounding some areas. Use some 180-220 by hand to give the low spots some scuffing and help the epoxy adhere. Wipe all the sanding dust and fingerprints away using denatured alcohol. Next if you are using the stock rudder as a handle, apply a band of blue tape around the end of the rudder to prevent epoxy adhesion. Brush a thick, wet coat of XTC-3D epoxy resin coating from Smooth-On onto the exterior of the print. Be sparing at the open lip of print only to prevent epoxy from dripping inside. Make sure the rudder tip and trailing edge are facing down during curing so the excess epoxy drains away from the opening and stock rudder. XTC-3D flows well, cures hard, and self levels nicely. It is a great way to get a smooth surface on your print. It does not take much, I mixed a 15mL batch for each application. Yes, it will be dripping off the end as it flows outs. Find a way to clamp it at a downward angle while it cures so it drips toward the trailing edge and tip. Wipe off the excess dripping initially (not the runs, they will flow out), but after that don't worry, let it drip. You will file it off easily later. 5. After the epoxy application, you will need to redo the fiing and sanding steps from earlier again. If you did the epoxy coating right, the "grain" of the print will be nicely filled. Again, do not go for a 100% perfect surface. It should be starting to look decent, but with some small low spots here and there, but looking 80-90% fair with no shaping other than light fairing to be done. 6. Apply a second coat of XTC-3D resin. It should be not be as heavy a coat, but still thick enough to fill. 7. More sanding as before, but you should be able to get a pretty fair surface now. Take it to 320 grit. You should be done, but if needed apply another coat of epoxy on trouble areas or a light body filler if it going to be painted. At this point, the rudder sleeve should be fair and smooth and you should be ready to apply your final finish with absolutely no shaping left to be done. • Finishing • You may have your own technique on finishing the surface, but this what I did. Spray three light coats of Krylon clear gloss lacquer (does not need a primer) about 5 minutes apart. Let it cure. Wet sand with 320-400 grit automotive sandpaper. The lacquer "orange peel" surface should be gone, leaving a very nice, even matte look. Spray two light more coats a few minutes apart. Wet sand with 600 grit to remove "orange peel". Spray again if needed, but I did not and proceeded to wet sand with 1200 grit. I followed this up with a very fine gray 3M synthetic non-woven pad (it looks like a green scrubbing kitchen pad, but is much finer). It will take down any remaining finish issues and get your surface ready for a light polish. Lastly, I rubbed the sleeve Meguiar's Scratch-X 2.0 liquid polish to get a nice semi-gloss sheen. The smooth and clear finish showing the embedded rough print surface gives a neat visual effect to the clear sleeve. You could paint this as well just using colored lacquer instead of clear. There some pictures showing the build process in the gallery above. Category: R/C Vehicles