Design it, Drive it: Speedboats: new forum reply to other boats?

New reply from Todd Wasson

Sorry about the delay, I just saw your post.

I’m wondering the same thing you are. I’m not really sure either way, specifically when it comes to the hull design and how well the performance matches reality. At a subjective level it seems pretty close within reason (better than I thought it would be, actually), but without serious validation I wouldn’t want to make a claim like “you can use this software to design real boats.” It’d be irresponsible of me to make that claim, really, because I just don’t know. “Pretty close” could mean the difference between a boat that flips and kills somebody and one that doesn’t, so I’m worried that it might be very dangerous to put too much trust in the simulation and don’t want to encourage anyone to do that unless I receive enough feedback from designers saying that it’s good enough for that.

My hope is that hull designers will play with the sim and report back to me their findings. However, I’ll leave it to them to say how well it does or doesn’t match reality because they’ll know better than I will.

Regarding propellers in particular: For that I can say for sure “no” at this stage, this can’t be used to design propellers, at least not the first release. The propellers right now are the least accurate part of the model, probably. At the moment the props are just four triangles, one for each blade. As you might imagine, a shape like that isn’t very efficient for a propeller blade, so to get the pitch setting giving a reasonable response, the blades in the simulator are raked severely. Otherwise a 26 pitch prop ends up acting like it’s a much smaller pitch. The way I rake the propeller changes the geometric pitch (which itself changes depending on the location inside the triangle blades you choose to measure it anyway). However, I was able to rake it the same amount and all the different pitches worked reasonably well. I was quite frankly shocked that the simple “one triangle per blade” approach worked as well as it did.

One bad thing about this is that when the prop is surface piercing (in the sim), the paddlewheel effect is too strong. At the moment I’m frequently having to countersteer 120+ degrees at the steering wheel when the prop spin axis is lined up with the bottom of the pad. I asked someone about this and he said that was too much. I’m sure this is because of the simple propeller, but it’s just one example of a response that isn’t right because of that simplification.

One thing I want to do in the future (probably after the first release sometime) is increase the resolution of the propeller so it’s a proper mesh like the rest of the boat. If I were to do that then yes, it would be a procedural mesh just like the boat where you could adjust lots of things. In that case I’d try to make sure you can adjust rake, cup, etc.. I can’t be sure how close the performance of a given prop would be to a real propeller of the same specs, but it might be enough to get the basic responses on the hull down well enough at least for educational purposes, to get a general feel for what rake actually does to the boat for instance. How well that will match with reality is unclear, but it I’m confident it would be an improvement so it’s up near the top of my list of things to do.

Even with that new propeller model, I’m not very confident that you’d really want to use the simulator to design a real propeller. To get a general idea of what those different things do, sure, but to actually design a real propeller for a real boat, not so much. There is specialized software out there for that sort of thing that will do a better job than I could in the simulator. Who knows though? Maybe it might get close enough to be useful as a real life tool at some level, sort of a scratchpad to play around with ideas before moving on to more serious software. I don’t know, but I hope one day to find boaters and designers discussing these types of things in this and other forums. They’ll be the ones that can really make that call and let us know how useful it is for actual design. I would be happy and proud if it turns out to be useful for real boat design.

Original Post by jackwilliam

other boats?

i know that this game is in a very early stage, do you ever plan on adding other boats?