yard-dart

My Feedback: (35)

Actually, I think Montague's theory is more accurately spoken.

Sport_Pilot

Correct. Except that humid air is also less dense. Reading off of a psychrometric chart gives the density of 92 degrees at 80% RH of .06897 lbs per cubic foot. At 92 degrees and 14% RH it is at .07143 lbs per cubic foot. I do this kind of stuff for a living boys. If you take the FAA pilots test you would know this one.

MikeSell

My Feedback: (2)

I found that Blaisdell makes a felt tipped marker with a heavy aluminum boss on the end usually covered by a plastic cap that is just the right size to thread for the exhaust of the AP. I drilled thru the center of the boss and dug the innards out of the marker. I then pulled the felt tip out of the ferrule leaving a stinger. The stinger was slightly too large so I used an expandable collet and crimped it down to an appropriate size. The result is a pipe resembling a tuned pipe. It is not as quiet as the std muffler but it has little restriction. It is too short for any more than a 1/4 wave tuned exhaust.
I altered one with a sleeve in the center to allow the stinger end to slide out a way. The results were inconclusive as I was trying to tach rpm under florescent lights. I was drawn away by interest in other projects before completeing the tests.

blaisdell liquid tip 1100

LOONY BOY

SJN looks good to me.
AP engines are great, I have modified a .09 and it turns a 6*6 to 22000 rpm.
Raised exhaust port, opened carb 10%, made tuned pipe, increased compression
Bad pic but better than none

SJN

Thanks...

yard-dart

My Feedback: (35)

Whatever you says Boss. It's awfully damn odd that the LA that I normally run in combat, the one that I only get 17.5K out of at the most on one of our 95+, 100% humidity days, turned 18.3K yesterday. What's so different about yesterday? Yesterday, it only got to a high of 86 degrees with the humidity of only around 60%.
You can give me all that scientific, I do this stuff for a living boys, mumbo freakin jumbo if you want. Makes no difference to me. I just come on here to read your lovely typing. For real, I'm gonna stick with the common sense side of things. This day and time, it's pretty hard to depend on any kind of science that has anything to do with the weather. Just the other day, the weather man stated that there was a 60% chance showers for the viewing area. Guess what! Not a drop of rain anywhere. On top of that, the other weather station in town called for a mostly clear day one particular day. Guess what! It ended up pouring rain 18 out of the 24 hours. Where do these guys get there info? From the same science you're talking about, that's where.

Like I said, you can give me all the science talk you want. In reality, I know what type of weather makes my engines run best, and it's just the opposite of what you're stating it should be.

John

hollerp89

I have a ap 15 i was just wanted to ask some one about do you think it will fly a
plane
30 3/4" corseair kit rc . email [email protected]
thank you.

no1speshal

My Feedback: (1)

I wouldn't do it if I were you. These are clean engines, they look great, run rather quiet and are virtually useless in the power range they are supposed to be at. If you had an application calling out for an .098, then yes, I would say use the AP .15. Otherwise, no way would I put that on an airplane that already has issues, such as an F4U. I would go out and drop the 40 bucks and get an OS 15 LA. It is worth it for the piece of mind. The AP might do it, but you will wish you didn't in the end.


Just my $0.02

Red

buzzard bait

There is no way to answer the question about the Corsair without knowing the approximate weight. It could fly on a Cox .049 if it is light enough. Say it is 28 ozs or less--I bet it would do fine on the AP.

Got to admit, I really like the OS 15 LA, but the AP will do fine if the plane isn't too heavy. Jim

iskandar taib

My Feedback: (5)

Actually, Sport Pilot was right. Humidity makes air LESS dense. Here's why. You might remember that equation from high school Physics:

PV=nRT

Forget about units for now, if you rearrange the equation:

n/V=P/RT

This means that, if pressure (P) and temperature (T) are held constant, a gas will contain the exact same number of molecules (n) per unit volume (V). So every molecule of water takes up the same amount of space as every molecule of nitrogen (N2) or oxygen (O2). Now.. every molecule of water (H2O) weighs 18 atomic mass units (amu), while every oxygen molecule weighs 32 amu and every molecule of nitrogen weighs 28. So you're replacing heavier molecules with lighter ones. We're so used to thinking of water as being "heavy" compared to air because we're used to liquid water and gaseous air.

Air which is less dense makes for worse performance - ask any full size pilot. Engine power goes down (water displacing oxygen, as noted), but lift created by the wing and thrust created by the prop also diminishes. Takeoff rolls are longer, takeoff speeds increase. It doesn't matter whether the thinner air is caused by humidity, high temperatures or high altitudes. Yes, it is true you can fly faster in thinner air (if your engine has supercharging), and you can get better fuel economy (which is why airliners like cruising at 30,000 feet).

Actually, I came here, like everyone else, to find out if these engines are any good, since there are quite a few used ones around. If I had to buy new, I'd get one of the blue head ASP .15s. Sounds quite promising, I'm not afraid of throwing the muffler away or hogging it out, same with the carb (replace it with a big venturi and remote needle). Too bad, though, that it isn't legal for Indonesian Rules Slow Combat (plain bearing engines only).

Iskandar