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Old Dec 31, 2010, 08:50 AM
Firepower
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North Brisbane, Australia
Joined Mar 2010
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Quote:
Originally Posted by dhdsracer View Post
I honestly don't feel like I was misleading. I at least truly hope the video isn't misleading. But there is always going to be someone that hates my videos. Oh, and there is a huge gap between the canopy and fuselage. That fuse is about as air tight as a spaghetti strainer... Now lets all have a beer and calm down.
cheers guys,
Don
Good stuff and keep up the videos. It was also mentioned there is a hole behind the wheel at the bottom that goes through to the inside just in front of the servos.

Someone mentioned earlier that it is the outlet for the air. I have made mine a bit bigger to let more air out. Also my maximum amp draw with the cut down prop is 18amps but still a bit close for comfort on the standard speed controller but I have not bothered to change mine yet or the motor. I guess a lot fly like that close to the limits of the speed controller but that is at full throttle.

Keep up the good work.
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Old Dec 31, 2010, 02:50 PM
Ozzie Express wiggy pilot
SON OF PALEFACE's Avatar
YANKALILLA , SOUTH AUSTRALIA.
Joined Nov 2002
5,234 Posts
Here it is for the last time
The "venting" wont work , because you need at least twice the exit area ....as hot air expands

Fitting a 30amp ESC wont work because the problem is still there , that is the motor , and it will either fail and or melt the plastic mount or both

The motor is the wrong KV for 3s and the standard prop , the ways to fix this is to either reduce or fit a smaller prop , around 8X4 , so the current is no more than 15amps , trimming 1/4" off wont do it......OR fit a motor with a KV suited to the stock prop , 860-1000KV , again keeping the current draw to no more than 15amps ...I fitted an 860KV motor and at $6 bucks is the cheapest option ...AND ...it works
This is a classic cruiser , not a hot liner and this power is enough

I hope this is the end of it....cause Ive had enough Bull Sh** for a while

Happy New Year

Ian
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Old Dec 31, 2010, 03:44 PM
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United States, ME, Bangor
Joined Nov 2010
101 Posts
Got my Moa airborne today. Fitted with an AR600. Dropped in a 3s 1800mAh 15c and chucked it. I was all tense and ready but for no reason. It climbed out without drama or incident. Better behaved than my Radian. And this with a CG that I knew was a bit spicy (80mm?) due to the light pack.

Powered up about 400 feet or so working out the trim and then cut the throt and just glided around...

It is a fast plane with excellent penetration. Love the way it behaves. Not as floaty as the Radian but much more authority and efficiency. First landing was spot on the mark. Checked the motor and batt. A little warm but not too bad. It IS winter up here. I did wash the prop plate and spinner out to about a 5mm gap from the engine housing.

Second flight I took her up a bit higher. Really sweet plane. Graceful and powerful. Rolls and loops like a prehistoric bird. Only thing is, she didn't want to come out of that dive. Made quite a crunching sound when she hit the birch tree. Tore the right wing completely off, bent the wing spar, knocked off the spinner (gone), tore up the leading edges of both wings and stab, broke two of the three motor mounts, tore at the stab bolt channels, knocked all the innards loose.

I knew from the start that this was going to be a high maintenance, laughter and tears kind of relationship.

No worries, a bit of tape, glue and some spare parts and she's all fixed up and ready to go again tomorrow. Forecast is for sunny, warm and low winds. Maybe this time I should avoid those steep dives? I'll let you know how it goes...

This plane definitely has some serious no BS attitude.
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Old Jan 01, 2011, 11:06 AM
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Long Island, NY
Joined May 2010
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Only thing is, she didn't want to come out of that dive.

@Devemaster
How did you get into such a dive?
Sounds like terminal compressibility dive on a P38!
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Old Jan 01, 2011, 11:20 AM
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Long Island, NY
Joined May 2010
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Quote:
Originally Posted by SON OF PALEFACE View Post
Here it is for the last time
The "venting" wont work , because you need at least twice the exit area ....as hot air expands

Fitting a 30amp ESC wont work because the problem is still there , that is the motor , and it will either fail and or melt the plastic mount or both

The motor is the wrong KV for 3s and the standard prop , the ways to fix this is to either reduce or fit a smaller prop , around 8X4 , so the current is no more than 15amps , trimming 1/4" off wont do it......OR fit a motor with a KV suited to the stock prop , 860-1000KV , again keeping the current draw to no more than 15amps ...I fitted an 860KV motor and at $6 bucks is the cheapest option ...AND ...it works
This is a classic cruiser , not a hot liner and this power is enough

I hope this is the end of it....cause Ive had enough Bull Sh** for a while

Happy New Year

Ian
The imbalance between prop size and motor plus the need for more air in and out, that's about what we figured out 30 pages ago!
So for the rest, nothing to get exited about. It's a lovely flying and looking plane.
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Old Jan 01, 2011, 12:46 PM
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United States, ME, Bangor
Joined Nov 2010
101 Posts
Well-

Was out again this morning. Zero wind, cloud ceiling about 3 kilometers. Had some great flights. No vertical landings today.

As to the dive yesterday, well I guess I put myself into that. I was having one of those 'wonder what will happen if' moments. Intentionally put her into a vertical dive just to see what would happen. I'm used to the Radian which will pull out of a dive no problem. The Moa takes a little longer. About 30 meters more than I had available at the time.

So at the risk of causing a group brain aneurysm I must say that the stock motor and ESC seems to be performing just fine. Of course it is winter time up here in the other hemisphere and I am flying the plane like what it is; an electric assisted glider, not a 3d stunt plane.

The air temp is a bit cool at 5C but not exactly arctic. I did move the prop plate out to a gap of 5mm from the motor mount, and my version of the plane does have a few vent holes in it. I wonder if they've been updating the plane.

I will probably have to do something for the summer, as I have noticed that the motor is warm, not hot, after a 3-4 minute burst at WOT. I will try an air scoop, kind of like a pitot, but also an exhaust hole near the back of the main compartment.

Here's something I've noticed: It's very easy to over tighten the prop nut so as to restrict the ability of the motor to spin due to too much friction. Wonder if some of the overheating problems are due to this?

Please forgive me if this is old ground for you guys. I'm a noob and your gonna get some repeat information occasionally. I think we need to find a balance between noobs asking the same question for the 1,000 time without reading the thread first, and the other extreme of not being open to new possibilities and ways of seeing from newcombers to the thread.

Just my two cents.

Oh, one more thing, I've programmed flaperons on the Moa and I'm gonna go chuck it and see how it works. First I make sure there is plenty of glue and packing tape on hand...

Cheers and good on ya-
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Old Jan 01, 2011, 03:18 PM
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Chilliwack, BC Canada
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Quote:
Originally Posted by devemaster View Post

As to the dive yesterday, ........ I'm used to the Radian which will pull out of a dive no problem. The Moa takes a little longer.
Thanks for the warning! Haven't tried that yet.

Quote:
Originally Posted by devemaster View Post

I am flying the plane like what it is; an electric assisted glider, not a 3d stunt plane.
Probably why some of us got away with using the stock power system for a while.

Quote:
Originally Posted by devemaster View Post
....... and my version of the plane does have a few vent holes in it. I wonder if they've been updating the plane.
I haven't seen that mentioned before! How big are the holes? Pictures? Mine had only one hole about the size of a pencil lead on the bottom behind the wheel.

Quote:
Originally Posted by devemaster View Post
..... but also an exhaust hole near the back of the main compartment.
This foam cuts really nicely if you take a piece of metal tubing, sharpen the end razor sharp (Dremel tool works for that) and then twist the tubing into the foam. Don't start too small because it doesn't work well trying to cut a larger hole where a slightly smaller one already is. See post #582 for some pictures of one way (not the only way) to do it. I would go a bit bigger if I were to do it again.

Looking forward to hearing how the flaperons work. I went the other way and made them spoilerons. Sometimes it just doesn't want to land!

Good luck and Happy New Year

Gord
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Old Jan 02, 2011, 08:11 AM
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United States, ME, Bangor
Joined Nov 2010
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Dive- I adjusted the elevator travel to 125% which seems to help get her out of a dive sooner. Plus I'm a bit more conservative and will probably not try another supersonic kamikaze dive for a while. Save those for the radian.

Pictures attached of the three vent holes. One behind the wheel like everybody elses, two in the red plastic cowling that is the nose. These are all probably too small to be very effective, but with the addition of a small pitot might increase the airflow and cooling capacity.

I'd love to see a dynamic fluid analysis of this bird under power. Something like a wind tunnel test to see just how much air is moving through the compartment and the temperature changes that occur during flight. Anybody out there have access to a Cray supercomputer? :-)

As it is I only check the temperature AFTER a flight. The motor, batt and ESC are probably getting quite a bit warmer than I think. But since this bird has already tried to chop off my finger, burn down my house and ruin a brand new battery (not to mention attacking a perfectly innocent birch tree) I really have no qualms about doing some destructive testing...how hot is too hot? Can I get her to burst into flames in mid air?

Flaperons need some work. First I tried with ailerons down 80% and elevator up 50%. Too much elevator so I went 0% elevator. That was good except I have to adjust mix to balance ailerons so she'll fly straight and level in flaps down mode. Still working on it. I will also try spoilerons too and see how that goes.

Please pardon the crappy photos. I wanted to use existing light and my camera has been drinking way too much coffee.
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Old Jan 02, 2011, 03:40 PM
Ozzie Express wiggy pilot
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YANKALILLA , SOUTH AUSTRALIA.
Joined Nov 2002
5,234 Posts
Here is some info on cooling.........especially read the part about "getting the air to move thru the cowling"

THE PATH OF LEAST RESISTANCE

Air will always take the path of least resistance, always. If we look at some cowlings, the space between the propeller and cowl is very small. The cowling and engine act as a dam, restricting flow. Air being pulled through the blades, close to the hub will try to follow the easiest path. In this case, it is simply backing up and swirling around and flowing outward to join up with the airflow from the outer portion of the blades. In order to fix this problem, some full scale designers move the entire propeller and hub out as far as practical from the cowl. This helps straighten the prop airflow. Current Formula 1 racers are examples of this. Radial engine aerobatic aircraft props are also set forward, for the same reason. The air flowing through the propeller now has less interaction with the big cowling. Very tight cowlings for the modern radials and large spinners also smooth the flow. This still leaves us with the question: how does the cooling air get to the engine?

LOW PRESSURE AT WORK

Simply put, we have to suck the air into the cowling. This is done by lowering the pressure inside the cowling . The internal low pressure then allows the outside air to flow into the cowl inlets . This is the key to air movement High pressure air moves in to fill a low pressure . Watch the morning weather lady, she will tell you the same thing. As long as a pressure difference exists, the flow will continue. If the pressure differences cease, the air stagnates and temperatures go up (Pictures and news at 11:00). To create this low pressure, we need some kind of setup to create constant low pressure in the cowling. How we do this is exactly the same technique used to cool a home. If you place a fan in a window facing outward, then open a window on the opposite side of the house, the fan , even a small one , will pull fresh air through the entire house. On our models we don't have a fan, so it is necessary to create this low pressure by using an aerodynamic trick. Full scale aircraft, sometimes utilize rows of louvers along the sides, bottom and top of the cowling. Air flowing over them creates a siphoning effect to pull air from inside the cowling. Cowl flaps do the same thing. When opened, they lower internal cowl pressure, pulling more fresh air through the engine cooling fins. This pulling of fresh air through the fins, ducts, vents and louvers, is the key to proper cooling.

EXITS AND AIR DAMS

An effective method to create low pressure in our cowlings, is to make an outlet hole in the bottom of the cowling. The hole can be nicely curved or rectangular, whichever looks best. It should be about 3 times the area of the total inlet holes in front If you can't do the math, don't worry, just eyeball it. Once you make the cutout, cut a piece of 1/64 thick plywood and attach along the forward edges of the cutout. The height of the air-dam (or spoiler) must be at least in height and may be blended in or left blunt. When the plane is moving forward or the prop is running, the air-dam turbulence will create the low pressure to make the air flow through the cowl and out the exit. This puts us back to the original chain saw setup with the engine in a case and air flowing over it. Actually, not quite. There is still the problem of making certain the air flows through the cooling fins of the engine!

note the words between the...

Heres another quote about cooling............

Have you installed baffles in the cowl to direct the cooling flow? Your air exits should be much larger (I think about 3-4 times as large) as your intake area. 18% total oil is fine with some castor to guard against a lean run. You don't want to cook the castor.

Bob



Read more: http://www.rcuniverse.com/forum


Another link to propper cowling design and areas

http://www.rcuniverse.com/forum/fb.asp?m=7236870
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Old Jan 03, 2011, 08:34 AM
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United States, ME, Bangor
Joined Nov 2010
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All good information, thanks. And it corresponds to what I've seen in other E-gliders. The Radian is a good example of what's required to get the air moving through. That huge slotted plate on the bottom of the fuse makes the three holes in My Moa look hopelessly inadequate, and on the wrong end of the plane!

Still, I will take any mods slowly and with great thought (except the ones I do by smashing through trees and slicing batteries) as they are more or less permanent. Also I am what my friends politely call a "rugged individualist" and if you say the world is round, not flat I am likely to take a walk just to prove it to myself. I've built a new prop setup out of the damaged blades and a spare baseplate. 230mm in diameter compared to the stock 270mm. Will try this out to see if there is any difference.

The plane still works pretty well in the cold temperatures, so I'm not in any great hurry. Summer will eventually return to the Northern Hem so I'll have to do something to keep flying.

Here's hoping you guys are enjoying your new year!
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Old Jan 03, 2011, 02:25 PM
Ozzie Express wiggy pilot
SON OF PALEFACE's Avatar
YANKALILLA , SOUTH AUSTRALIA.
Joined Nov 2002
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The info on cooling is for general enlightenment.....and also for "video makers"

I have found over the years ...66.....that it really doesnt pay to rabbit on about things you "think" you know about....because sooner or later ...you will get caught out ...and you only really succeed in making yourself look stupid...........er
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Old Jan 03, 2011, 06:02 PM
I'm slow but I'm expensive
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United States, GA, Snellville
Joined Nov 2003
576 Posts
cooling

On new full scale planes the air inlet has gotten much smaller. It is designed to give the proper amount of airflow in cruise flight. The air flows into a large volume plenum (divergent duct). By Bernoulli's principle the airflow slows and pressure goes up. The outlet side of the cowl does need to have less pressure than the intake side. A Cessna 210 has about a 6" H20 pressure drop. If you have cowl flaps they are open for starting, takeoff and climb. In cruise as the cowl flaps are closed you can see a few knot increase in airspeed. The cooling drag is a fairly large portion of the total drag. We also use fuel to help cool the engine. At idle we have the richest fuel air mixture. At power settings above cruise is the next richest. The leanest fuel air mixtures are in cruise flight. Adding fuel over an optimum fuel air mixture lowers combustion temperatures and the cooling load.

For our models we might try a tube around the motor case that forces all the air through the motor or very close to the case. Any cooling air that misses the motor is wasted.

Myself, I bought the Minimoa to be a cool sport sailplane. Short powered climb to altitude and then the motor off the hunt the elusive thermal.

Ken Lilja
A&P instructor
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Old Jan 04, 2011, 12:26 AM
Ozzie Express wiggy pilot
SON OF PALEFACE's Avatar
YANKALILLA , SOUTH AUSTRALIA.
Joined Nov 2002
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WTG ...Ken
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Old Jan 04, 2011, 07:32 AM
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United States, ME, Bangor
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Now there's an idea, cowl flaps. Maybe on the throttle channel or somehow mechanically linked to the spinning of the prop? Then in power off mode everything is all slick and streamlined again.
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Old Jan 06, 2011, 05:01 PM
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Quote:
Originally Posted by SON OF PALEFACE View Post
The info on cooling is for general enlightenment.....and also for "video makers"

I have found over the years ...66.....that it really doesnt pay to rabbit on about things you "think" you know about....because sooner or later ...you will get caught out ...and you only really succeed in making yourself look stupid...........er
I think you're taking this far. He said it pulled 27 amps when he tested it, and that it's a good idea to replace it.

What's bad about that? Maybe you need to watch the video again.
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