Thanks for the kind words, guys - I do appreciate it!
Now, I've had a bit of downtime and I've taken the opportunity to hammer out some feedback for everyone's entries for this challenge. First of all, some general comments:
As I had hoped when I was designing this challenge, larger, slower-turning engines performed better than small, high-revving engines. While the engine block itself will be larger, it does have some very serious benefits; first, the lower revs means you can use cheaper cast parts in the rotating assembly, and it also means you can use a smaller and cheaper cylinder head design, in addition to a smaller, cheaper and lighter reduction gearbox. With the exception of Riso's engine, the top powerplants, if you notice, almost all used MOHV cylinder heads. In future challenges with multi-engine aircraft, the compact size of an OHV motor will give a substantial advantage in terms of the frontal area of your engine nacelle, which is calculated largely from the width and height of your engine.
The other huge, huge thing in this challenge was fuel consumption; since there is only a fixed amount of fuel aboard, every last drop counts, so your aim should be to build an engine with the absolute lowest specific fuel consumption you can manage and still produce the power you need, even if that means making the engine larger than you think is necessary.
Additionally, it seemed in this challenge as though flat-rating a more powerful engine to a lower power level outweighs the drawbacks of having a larger engine in the first place...it will be an aberration, I believe, because the next challenges will be a lot more free in terms of power and speed. Instead of a fixed speed limit, subsequent challenges will have a range of speeds that their real-world equivalents are capable of reaching. Bear in mind that the laws of aerodynamics will come into play here as well; to double your speed, you will need roughly eight times the power, which does not make sense from a fuel economy standpoint. Another note on flat-rating; if your engine has poor specific fuel consumption, it can dramatically improve your cruise fuel burn and therefore your range performance!
Now for some individual feedback:
@8bs Overall your engine was quite good; lightweight, compact and with a very good propeller choice, though the addition of variable valve timing was perhaps not entirely necessary and added to your already higher-than-average cost. Your takeoff and climb performance was excellent, but the relatively high propeller RPM (2850) meant that in order to absorb the power you produced, your propeller pitch was quite fine (a small blade angle), which hurt your cruise performance somewhat. Also, your specific fuel consumption was on the high side, which didn't help much either. All in all though, not bad!
@AirJordan Your engine was one of two V6s, which made things a bit more complicated in terms of cost; that said, your choice of a pushrod head helped get your engine more in line with the rest of the group. Power output was good, and your (relatively) coarse-pitch propeller was more oriented towards cruise performance than takeoff and climb, and it showed - your aircraft was among the fastest in nearly every metric, but it also had a lower than average climb rate and service ceiling as well as a longer than average takeoff run. A very interesting effort to say the least!
@DeusExMackia Your engine was reasonably good in most aspects, and apart from the two entries who took advantage of a foolishly (on my part) ignored calculation loophole, had the highest Time Between Overhaul rating. However, your engine was the heaviest and most complicated, which made your payload and overall cost suffer dramatically. The small, fine-pitch propeller selection did not help a whole lot either, as your cruise speed was a little below average. That said, your engine had an excellent specific fuel consumption, so that does help!
@Kilonum Your engine was perhaps a bit on the small side, and while it gave you by far the best payload of any aircraft in the challenge, it did mean you had to work your engine very, very hard to make the power needed. As such, your fuel economy was, ummm, not good - 57.8 pounds per hour is about what I would expect an aircraft with double the power to burn - and your TBO was on the low side of things. I will also say that I think your chose the best overall propeller of all the aircraft - your takeoff, climb and cruise performance was excellent overall otherwise!
@koolkei What can I say, you won! And you could have won a bit bigger if you chose a bigger, slower turning propeller to get a bit more out of the aircraft overall, and had you opted to spend a bit more money and went with a composite-bladed prop, the weight savings would have boosted your lowest category - payload. Other than that, fantastic job!
@MrChips Don't screw up the unveil next time! Biggest thing I could improve would be my specific fuel consumption, which I could have helped by building a slightly larger engine. My propeller was one step too far in terms of cruise performance as well, I think.
@one85db Your engine was very small and had to work very hard to make the power it needed, plus the use of a V6 AND overhead cams meant that your engine was extremely expensive - almost $10,000 more than the lowest scoring engine. On the other hand, your compact engine gave you an excellent payload number, and your high power output combined with a good, coarse-pitch cruise propeller gave your aircraft truly excellent altitude and by far the best maximum and cruise speeds of all the entries. Well done in that area!
@Riso Your engine proved that you don't need all the horsepower or complicated, fancy engines to be very, very competitive. By choosing to flat-rate to the bottom end of the suggested horsepower range, you gave up a fair bit of takeoff and climb performance, but you also gained a tremendous advantage in TBO, fuel burn and altitude performance. Having said that, a larger, finer-pitched propeller would have improved your takeoff and climb performance to the point that you could have won the competition hands-down.
All in all, I am very satisfied with the result of this challenge, and I hope to see all of you and more back for Round Two, which will be chosen from my list of possible challenges by none other than our winner, @koolkei. I'm going to need a bit of time to iron out a couple of very minor quality-of-life issues with the simulation, and finish tweaking the revised Powerplant Calculator - no longer will it be possible to get insane and unrealistic TBO values from a big flat-rate, propeller weight is now calculated based on hub and blade characteristics (instead of just a simple algebraic length function), and I have added a couple of other things to help you guys out as well!