ORIGINAL: rcpattern
Matt,
I would say the 10% drag. I know a 10lb Black Magic VF3 with the drag on it will NOT fly the Masters pattern COMPETITIVELY with an OS 1.40RX, but it does just fine with a YS 1.70 or electric setup with a lot of torque at close to 11lbs. Heck, my old Mantis at 9 3/4lbs still had problems in the summer heat in Muncie getting through the top of climbs with authority. I'm not saying they are not good engines, but I dont think they are a viable top level engine any longer. If they were, then why arent more people running them in Masters and FAI. I wouldn't have swtiched to YS had I not that it would be beneficial. I didn't do it just for the heck of it. I LOVED my OS 1.40's and ran several of them to near death.
Renegade,
A thin fuse doesnt mean less drag. There are many other areas to create drag without a really wide fuse. The mid-rex may be thin, but it is still a large airframe.
I don't claim to know all the ins and outs of drag as i'm not an aerospace engineer. However I have flown enough designs to know the differences.
Arch
I will buy the argument that making the RX produce the required power is not trivial and not an excercise that anyone could undertake. Same is true with the Webras, which I still run and love. These are not the plug and play variety powerplants as YS could be and electric appears to be.
And prop development is not for everyone either. However, matching the power you have to a prop or two (for extremes in wind) to the model of choice, can be done and should be done by anyone deisring to compete at the highest level. Of these, the prop is the least understood and practically never played with. Bryan Hebert and Dave Lockhart are about the only other guys I know of (besides yours trully) who don't mind playing with the prop a bit. I suggest that some should try messing with this gizmo to extract max efficiency out of any set-up.
On the other hand I'd agree that most RX's I have oberved or have owned are slightly off the power that Webras develop. YS has nothing on the Webra 160. Unfortunately it appears that hardly anybody can make this thing run. I've not had hardly any problems with mine but I know I am the exception
Hey for those who care in an alternate, the Syssa 180 gasoline engine might be worth a closer look. Power is better on pattern props than the RX or W145 or YS140/160. But less than the YS170 and W160. Cost to purchase is reasonable, cost to operate is about 1/15th, cost to maintain will probably be practically zero on an annual basis, and weight is quite comparable to many of these and far lighter than electric. And you get the fine throttle of the special Walbro carb. Just a thought. Todd Syssa has been open to suggestions from pattern need point of view so we may have some news on a modified version also.
In a different thread I intend to have flying report in a pattern set-up soon if the weather holds
MattK