The shocking truth about speed or, Dustflyer finally gets a taste of reality!
OK, my Jett FIRE 50 is SCREAMING, I'm turning a 7.4 X 8.25 carbon fiber prop at 21,400 on the ground. I launch. It unloads. Man this thing has got to be going....
Today I met my friend Sydney at the NE Philly RC field. Syd is no ordinary modeler. This guy was flying RC planes when most of us were still in liquid form. Today, retired with no worries other than where and when he is going flying, Syd sends humbled 30 year old hot-shots running home with fingers outstretched, itching to boot up that G2 sim for more practice.
Syd brought his radar gun along today, and no ordinary bargain model. This baby was 1500 bucks, just calibrated, and Syd could teach a New Jersey state trooper a thing or two about how to use it.
A while back, on a different forum, I remember other contributors, racers probably, telling me how all the charts, formulas, calculators, etc. were just so much nonsense for calculating aircraft speed and how I was obviously full of, well.. let's just say they were, uh, I was.. well, you know what I mean!
So here I am today. Syd is in position. Turning 20.4K, backed off from 21.4 I launch my Dust. Plenty of thrust! Off it goes like a slingshot, straight out. I take it up high, put it into a screaming dive, DOWNWIND, the doppler effect registers and the call comes through on the walkie-talkie to Frank, my spotter.
The speed? All of, are you ready? A whopping...150mph!
This is repeated over and over. The fastest I could get it to go was 150.7 mph.
So, what does this all mean? It means that all the charts, formulas, calculators, etc. are all NONSENSE, just like everyone told me they were!
Clearly, something more is at work here. You simply cannot take pitch x 10 x .000947 or whatever and calculate speed.
Let me ask you this. If you turn a 9X8 at 20K will you go the same speed as if you turn a 6X8 at 20K? How about a 5X8? If you could fly the airplane with a 3X8 turning 20K could anybody with any common sense assume the airplane would go the same speed as with a 9X8 turning 20K?
My point is there is more than rpm and pitch to the speed solution. There needs to be a certain amount of thrust. I don't know how that is figured out except by trial and error, maybe there is a way.
I am convinced the Diamond Dust has a lot of drag, induced drag mainly, plus a whole lot of wetted area. There is no way a teeny tiny prop is going to pull that thing through the air at 200 mph, I have proven it!
I know what I am going to do. I am going right back to where I started...long pipe, 9X10 prop turning 16K plus. That's where I am going to start with my Whiplash and to where I will return with my Dust.