RC Laser Sailboat Rudder & Extension Sleeve & T-foil

thingiverse

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