Is putting a whole through a spinner a better way to cool an electric motor than adding some kind of inlet behind the spinner?[X(]

OL, the guys who did the actual research must have been happy to find such a simple solution. I've never seen what you are talking about in person, but I'll bet a look at it while running would reveal that it disturbs the air.

Art Chester did this in 1947 with his Swea Pea design for Goodyear racing. The cheek cowls had no opening on the front, so all cooling air was drawn through the spinner. Inside the spinner was a four bladed fan as well as the shank blades of the prop.

One of the first FW-190's also had a ducted spinner. It had (would you call them?) impeller blades inside it to pressure cool the BMW radial.

I was thinking...if you drilled some holes at an angle through the spinner's backplate, similar to a vented flywheel?
Or...if you look at some of the light weight Aluminum spinner backplates with all the lightening windows cut in them...you could file/shape the webs to a fan blade shape.

You could also make/shape the cowling's air exit to be a more effective low pressure area to help pull air through the spinner opening. (by that I mean more effective than your typical (seemingly ) after thought cowl air exit )

Air through a while in a high pressure area is free air in most aerodynamic shapes. A friend and I have been experimenting with a Hobby Lobby F5B Tiger which comes with such a spinner and we also have a regular spinner. We are not experts with a lot of instruments so we spray the plane with corn starch, fly it and look for patterns in the cs after landing. We are going to experiment with different power substances but we are looking for air separation from flying at different speeds. We have discovered with our home made methods and a flight logger to get power expended while flying are giving us useful data that we can try to turn into information.

We have found two different kinds of experts that have volunteered to help. Number 1 is the guy that already knows the answer and preaches to us. When our tests do not prove him to be correct they we find out that we are wrong. The other more useful one gets involved in discussions and make suggestions and is quick to say the dreaded three words that are lacking in number 1's vocabulary, "I don't know". Our basic

We are finding out that air flow around the spinner and the very front of the fuselage is important by itself and is also important in not messing up the air flow around the wing roots and the first 10 to 15 percent of the wing. Many other get tied up in the wing tips but we are finding out that the wing roots are an important area and might just worth spending some time on the lean what is going on.

The reason for my initial question about spinners is that you may have swapped spinners and found more than just improved electric motor. The reason I'm interested in this is because this solution would work and different speeds, angles of attack and plane orientation with respect to the air flow. Designing an exhaust duct would be easier because in most positions it's under some positive pressure and during the times when it is not then less cooling may be required. A plane going backwards does not spend much time in this attitude and air flow is of less concern.

This leads to another question. Has anyone looked at vortex generators or modifying the surface texture from glassy smooth to rough in areas of flow separation in areas that the corn starch shows changes in air flow?

By putting tape on the wing of the HL Tiger length wise we have kept the top speed but with no changes in the ailerons programming for landing we have cut the approach speed dramatically with much better overall control and greatly enhanced ailerons authority. The strips are 1/16" wide and run the full length of the wing. and is set back at 75% of the chord. We are trying different methods of adding texture to the tape. One of the experts said it won't work. He said this while watching the Tiger land. I guess that because we are too stupid to know it won't work, it did work. The only thing we have to do is improve our coarn starch. We were thinking of moving from 32 bit corn starch to 64 bit with a raid array.

During all this we are hoping that the hole in the spinner is going to prove to be the method of choice along with improved exhausting without a lot of internal dran, in other words getting it out as soon as possible.

Larry, there's dozens of ways to add turbulence to a shape to delay flow separation. They all have odd names but the whole point is to convert laminar flow to a thin controlled turbulent boundry flow before the air can separate from the surface and cause larger and more draggy "bubbles" of turbulence. It's not uncommon to find such turbulators on wings and a large part of Micheal Selig's wind tunnel work on airfoils involved turbulators being added at various points and the airfoils retested to see if some of the low speed troubles could be corrected. There's even cases of turbulators, invigorators or some other assorted gizmos being used on fuselages and air intakes and I even saw pictures of what looked like invigorators on a wing mounted mission pod of some sort.

Back to spinners, there has to be all kinds of dirty air created from the gaps between the prop and the spinner cut outs, plus any other access holes, etc. that are whipping around. The FAI pylon racers' one piece prop/spinner with all blended surfaces isn't just done this way for looks.

I think the idea to draw air through the spinner for cooling is a crafty way to get to that goal, but I don't believe in any free lunches...something always gets lost in any energy exchange.

There aren't many free lunches, but you can make a pretty good sandwich with a couple of ingredients that complement each other.

The key to getting it to work just might be a good sucking exhaust hole or two aft on the fuselage. Place a decent vent or two in a good strong negative pressure area to start. Make sure there aren't any significant openings from there forward to the hole in the cowl behind the prop, and you might have a winner. Negative pressure right behind the spinner could make the holes in the spinner work. Just having holes in the spinner aren't going to insure much of anything.

A number of designers in WWII tried to boost engine cooling with a focus on the area of the spinner and immediately behind it. There were a couple that worked. One used an impeller immediately behind the prop. Most helped the cooling, but took horsepower. So they settled on pressure cowls. Which should be a clue as to what makes cooling up front work. Pressure cowls work great. And depend on having negative pressure to get the parade started.

You get the negative pressure back at the exhaust holes and contain it all the way to a hole in the cowl right under the spinner. So the spinner backplate feels negative pressure that it exists thanks to those remote holes.

Good thing about working negative pressure for your purpose is the simplicity. All you need to get results is a hole or two. Pretty low maintenance too.

Is anyone using corn starch or other powder to track flow separation?

Combatpigg, your comment is well taken. By spraying a water based paint on the spinner and prop we discovered the gap problem right away and filled it. The prop was able to draw more current through the motor with these changes.

The problem with this testing is that none of us have a lot of spare time to devote to all this. I would like to figure out a way to scratch build composite wings and fuselages. The ARF kits are really expensive especially if you're going to hack it up anyhow. The best thing we have is that we want a fun plane not a strict by the rules plan like an F5B pylon racer. I just want to lean how to fly better and have some fun and experiment along the way.

Ol' Larry, you've taken it way further than I ever imagined....I'll bet you are much more able to visualize probable aerodynamic outcomes because of the experiments you've done with corn starch and colored water. If I felt it was possible to rig up a poor mans' wind tunnel to test up to 250 mph, I might be interested. I imagine I'll need to live closer to 3 phase, 480 volt power and get me a 25 ton air handler unit, though.

Maybe it would not be too expensive to build up a wind tunnel. At least most model airplanes are smaller than the models used in the aerospace industry for such testing. You'd only have to make the space wide enough to handle one wing and the fuse. You could leave the other wing off. Another way would be to mount your model on top of your car and use the corn starch/fine powder method and maybe a video camera. You'd just have to do it some where that to avoid a speeding ticket. So far I have discovered that a lot of common knowledge about aerodynamics is just plan wrong or at best incomplete.

A Control Line stunt flyer some years back rigged an airfoil testing setup for the hood, not the roof of his vehicle. The roof sees turbulated air and it's most often upslope air. In fact, unless the airfoil is significantly forward of the nose of the car it's going to see disturbed air too, just less disturbance.

But since he was looking for comparisons more than clean, pure data, it worked for him. And he set the competition environment on it's ear with the things he did thanks to that testing.

Did you know that the NACA test profiles back in the early days were about the same chord we use today? Ones used in tunnels were often 8" chord.

And how big would a tunnel have to be to test different cowl/spinner setups?