BaBy Clown in Prgress

Cribbs74 wrote:Eric,

Here is the the Baby Clown as built like yours before I modified it. I was running a Medallion with a 3/4oz Perfect hard tank. It was a good setup. Please excuse the poor flying. Inverted flight was a new thing to me at the time.

Nice Flight I cant fly 1/2A Cox 049 engines where I am at, They dont seem to like the 3000+ ft Elevation where I am at in the high desert, up here its best to use a 10 size engine or bigger, I fly E power planes up here because the Elevation does not bother them Take care and have fun, Chellie

Chellie, actually that flight of Ron's occurred at 4,300 ft. elevation. Location was the MADS (Model Airplane Driver Society) AMA flying field at the Ned Houk public park lands belonging to the city of Clovis, NM. I was the one releasing the plane for Ron.

Ron's is powered by an .049 Tee Dee. However, at our elevation (Ron's was visiting Clovis at the time), the reed valve engine don't do as well. You are correct if referring to reedies, smallest engine I'm using is a .15 for CL.

that's interesting about the elevation, meaning the air is too thin? Cribbs stated it was a medallion he had on it , either way it had plenty of gettie up to it ! Had a bad neck day from tilling and putting the monakote on see if I can get the rudder assy. and tail skid on today so I can bal. for the CG passion with the engine ( most likely 049 medallion ) will bee the power . may have to tone it down a bit to keep from loosing my mine going in circles , I am excited about it though that and the baby ringmaster to maiden in one day will either bee good or bad Thanks for the replys and I do like colors

Makes sense that reed engines suffer in thin air. After all, the reed valve is opened by the external air pressure... Never thought of it that way.

Maybe there should be some thinner/more flexible reeds available for higher altitudes?

getback wrote:that's interesting about the elevation, meaning the air is too thin? Cribbs stated it was a medallion he had on it , either way it had plenty of gettie up to it !

My bad, I thought it was a Tee Dee. Medallion is IMO basically a slightly detuned Tee Dee, still is more powerful than a Cox reedie.

KariFS wrote:Makes sense that reed engines suffer in thin air. After all, the reed valve is opened by the external air pressure... Never thought of it that way. Maybe there should be some thinner/more flexible reeds available for higher altitudes?

It's not a matter of the reed valve assembly, has to do with the reduced ambient pressure. At 4,300 feet (1,311 m), atmospheric is about 12.5 psia (0.85 atm). At 6,500 feet (1,981 m), it is about 11.5 psia (0.78 atm). In a crude sense you are producing 85% of your sea level horsepower at 4,300 ft., and 78% of your sea level hp at 6,500 ft. This corresponds to a 15% and 22% power loss respectively.

In this higher desert, the land is flat. we don't have much trees and structures to lessen the winds near the ground. With reduced hp, the reedies can't keep decent line tension with the wind.

I found though you can fly RC, provided your aircraft is constructed light and has sufficient wing area. I flew my Q-Tee on Black Widow power in Gallup, NM at 6,500 feet on a 6x3 or 6x4 Masters prop. Q-Tee has generous wing area. Interestingly, prop sizes have a more dramatic effect at elevation. A 5x4 prop on my Q-Tee produced the same air speed as a 6x3 prop at sea level. At 6,500 ft., it barely produced enough lift and Q-Tee was struggling to maintain altitude.

Gallup has mountains to reduce wind speeds near the ground. I don't fly reedies in Clovis because of its terrainless features. Here, my Q-Tee is powered by a Norvel Big Mig .061 CL/FF engine. It is Tee Dee like in power and has good wind penetration on the Q-Tee.

KariFS wrote:Makes sense that reed engines suffer in thin air. After all, the reed valve is opened by the external air pressure... Never thought of it that way.

Maybe there should be some thinner/more flexible reeds available for higher altitudes?

In addition to the ambient air pressure, the reed is forced open by the vacuum pulled by the displacement of the rising piston. Incidentally it's the remains of that same vacuum that causes the crankcase to inhale fresh air at TDC on SPI engines. By then, the crankcase vacuum has been partially relieved by the inflow from the venturi. Lots of wasted energy compared to a rotary valve that gulps wide open outside air for a few degrees of rotation. That's also why SPI isn't quite as beneficial to a rotary.
Rusty

GallopingGhostler wrote:Chellie, actually that flight of Ron's occurred at 4,300 ft. elevation. Location was the MADS (Model Airplane Driver Society) AMA flying field at the Ned Houk public park lands belonging to the city of Clovis, NM. I was the one releasing the plane for Ron.

Ron's is powered by an .049 Tee Dee. However, at our elevation (Ron's was visiting Clovis at the time), the reed valve engine don't do as well. You are correct if referring to reedies, smallest engine I'm using is a .15 for CL.

Yea, Its the reed engines that dont like the higher elevation, Its good to know that the TD engines will work up here