Tired Old Man

My Feedback: (1)

To be candid Super08, I've never heard of the guy either, "professional flying circuits", Top Gun, or anywhere else. I wish him the best of luck with his distributorship since it appears JC has now found another to accept the responsibility.

I'll have to admit I'm not paid to fly someone's "team" model of build a "scale" plane. All the stuff I work with I'm paid (call it professional) to do but you might call all of it "full scale" even though the aircraft are on a "reduced size" level. I don't mount engines on a test stand and spin up as much RPM as possible, or hook engines up to fish scales to determine power output. I'm afraid it's a little more sophisticated than that.

I learned that props run up in a static condition, like a test stand or executing a limited distance pull on a fish scale, doesn't provide anywhere close to the true output of an engine. Prop blades stall when they are restricted to a static position and the limit of what they provide occurs when the blades stall. So prop/thrust charts are useful, but only up to the point a prop stalled, which is very early in a static environment. All the convertable energy after that point is never measured because the stalled prop became an air brake, limiting the engine, so most people don't have a clue what their engines or propellers can actually provide where performance is concerned. Happens the same way on a dyno so wind tunnels or other ways of moving the prop through the air are required to find answers.

Most people prop an engine for achieving the maximum RPM, which is really quite easy to do. Those engines will do "fast" work but never provide the output they were designed to provide. For the guy that wants to drag a light model with a high lift airffoil around the patch that stuff works out pretty good but what happens when they need to set up an engine to pull a very heavy plane having a high aspect ratio wing for extended periods of time while maintaining a fuel economy that doesn't require a 10 gallon gas tank for 8 hours of flying? That fast response prop just won't do, and the engine will consume far more fuel than the plane can carry for a needed flight duration.

Even the light plane, 3d, warbird, fast mover crowds can benefit from better understanding the relationships of a propeller to an engine. Once people get away from static thrust charts they start to learn about wider blades, increased diameters, tip shapes and cross sections, and how those relate to engine performance. Why? because they left the race for RPM and discovered the meaning of power. The ability of an engine to perform work, not just seeking an answer to how fast that engine can do a little bit of work. Some might find that all that time they were chasing the peak RPM they were wasting an engine's potential because the best performance was to be found 400 to 800 RPM below what all the other engines were hitting at "peak" RPM. Unfortunately those answers won't be found in an internet forum with the question of "what's the best prop for..." because the answers will be limited to the lowest common denominator. That denominator is usually the least amount of cash that was required to buy a "suitable" propeller, and the reluctance to spend in the quest for perfomance limited experimentation and published selections.

Such is the case with 3w. All those people that have been trying to match the short stroke engine RPM peaks have been passing well past the peak torque of a 3w engine. The next thing you hear them say is how such and such engine outperforms a 3w. They also forget that an engine's ability to shed heat and continue providing all that power while under stress is another important aspect of an engine's qualities. Now take that JC 60 and the 3w 60 and put them in a 35 pound plane and point them straight up. Prop that 3w with an inch more diameter and see just how much stronger that JC is. Better still, pit that JC against a 3w 56 twin and watch the JC start to cry. The JC may be good, and it's definately cheap, fitting that specific need of 90% of the people in this forum, but it's not possible to be that good. Copies of other products never are.

You have to have the ability to conduct a little engineering R&D to be able to stay on top of the pack, else all you're doing is playing catch up. Most all the engines out there copy another in one manner or another but the name players like DA, 3w, MVVS, BME, RCS, and DLE (yes I said DLE) go a few steps beyond and make subtle or significant changes that aren't generally transferred to the molds of the copy artists.

So ultimately we have a new dealer for JC that has found a venue he can get some mileage without having to spend anything on advertising. Not the first time it's happened and it won't be the last, but hopefully the new guy will state what he hopes to accomplish beyond making a buck. Until then everyone should give him some room to discuss the product with factual test values obtained from woking the engines hard to establish their endurance and reliability. I'd say 15 or 20 engines worth of data over a couple hundred hours of run time on each should provide a reasonable comparison basis.