Max_Power

Wow Tim, that looks incredible!, when are we going to the field? (Just kidding, I'm too big of weenie to even move my chair away from the heater vent with the weather the last few days BRrrrrr!) I am really anxious to see it fly though. You've done a great job keeping the weight down so I'm sure it will be a great flyer. I've got some regular glow plug adapter heads that might knock a few rpm off if you want to try that. I bet it will be like your sure shark and require more of a release than a launch! Todd

skaliwag

My Feedback: (1)

I agree the .020 prop is too small so Texico-ficate the 049. Add shims, try a 7 X 3, won't need so much Nitro.
For sure turn the 6 X 3 around for the maiden.

GallopingGhostler

Along the same line there are other options such as running a 6x2 prop, using a glow plug adapter that lowers compression, among the other suggestions. There's Ken Willard's Virus plane that I've been wanting to build, will do some day. Since the Pee Wee .020's are getting rarer, I was thinking of using a Cox SureStart .049 with a glow plug adapter. That should tone it down to 1950's .049 levels.

combatpigg

My Feedback: (3)

It turned out looking really super.! Love that canopy, the cowl, the way the engine fits and the finished weight.
A 6x2 at 19,000 rpm gives about 34 mph and 1.25 pounds of thrust.
A 6x3 at 15,000 rpm gives about 42 mph and .87 pounds of thrust.
A 6x3 put on backwards must really cut into these figures.
You could fine tune high speed rpm by restricting intake area with a pressed in plastic insert and experiment with hole sizes. That would be an interesting experiment.

GallopingGhostler

I initially flew my Q-Tee as rudder only with an Ace Pulse Commander with Adams Stomper Actuator and Cox .049 R/C Bee on KRD sequential quick blip throttle control. I installed the elevator as a control surface, but used a short piece of pushrod fastened to the fuselage with an adjustable clevis, so prior to flights I could tune in the amount of decalage required for rudder only.

That could be a way to set the RPM of the .049, a similar linkage to adjust the exhaust collar throttle.

exocet-RCU

My Feedback: (1)

Thanks for the compliments and suggestions, guys. So, even a 6x3 is going to produce a 1.5 to 1 thrust to weight ratio. Wow. The 6x2 has a higher thrust to weight ratio but won't fly it as fast. I think I'm going to put a Mecoa plug adapter on it and see if that tones it down. I'm pretty excited about this plane.

Todd, I HOPE it isn't quite as fast as that Sure Shark was.

Tim

GallopingGhostler

You've done a sweet job of building, exocet-RCU. Now comes the trials, tweaking her in, getting her to a point where she's truly enjoyable to fly.

Andrew

Tim

What a great looking plane. .049 sized and with a .020 weight, it's probably going to be a rocket. Waiting to hear about the maiden.

andrew

Chad Veich

My Feedback: (60)

You could put a 3-blader on the .049 to absorb some of the excess power. I converted this kit to control line many years ago with an .049 and while I don't recall the AUW I'm sure it was a whole lot more than your 8.5 oz total. Great work and I will waiger that it flies very nicely. Good luck with it.

GallopingGhostler

Back in the 1950's and 1960's, one way to limit RPM on reed valve Cox's for free flight was through a home crafted simple sheet aluminum sleeve with ends bent out to form flanges for a small nut and bolt (2-56, 3-48, 4-40, etc.). One slid this sleeve up or down to act as a manual exhaust restrictor. Another way would be to drill circular holes in this simple banded sleeve (say, 5/32" or 4mm hole) that coincide with the exhaust slits and carefully rotate it. It would require trial and error to get desired RPM, then flight test.

Mr Cox

What engine is it, a regular babe bee?

It should be fine, just launch it a little on the rich side for the first flight and trimming.
I have planes at 10oz and use a Norvel .061 with a 5x4 prop.

exocet-RCU

My Feedback: (1)

Well, it flew. Actually flew really well until the engine quit and then I tip stalled it coming in. Needs a little repair but not much. I was surprised at how well it flew. Wish the motor would have run better but I think it might have started overheating. It ran great while we dialed it in then, when we walked to the flightline (about 50 ft from the pits) it started acting up. I adjusted the needle and it seemed to fix the problem but, soon after we launched it, the motor started acting up again and eventually died. But the plane just took off out of my friend's hand, flew straight and at a gradual climb. Can't wait to fix it and fly it again.

Tim

Tee Bee

Sorry about the mishap. Happens to us all. Glad she flew well. I had a feeling it would. I've got one of those Zero kits on the shelf and a box full of reedie .049s. Hmmm.

combatpigg

My Feedback: (3)

A plane this light would be pretty difficult to stall unless the CG isn't right.

exocet-RCU

My Feedback: (1)

CP, it stalled because I just got it flying too slow when trying to land it. I was trying to be slow it down for a gentle landing and just 'over-gentled' it right into a stall. Totally pilot error.

I'm curious, though, as to why the motor started acting up and then died. I had a 6x3 prop on it (big, I know, but had hoped to slow it down a bit for the first flight using that) and the engine was cowled. Do you think it started to overheat? It ran fine on the bench and then walking out to the flight line. It only started acting up after it had been running for awhile.

Andrew

Tim -

It's difficult to tell from your pics, but do you have sufficient openings at the back of the cowl to dump hot air and exhaust? It may be that when flying, the cowl is simply packing air and exhaust and, like you noted, overheating. A very general rule of thumb is to have exhaust air openings about twice the size as intake to allow for expansion.

exocet-RCU

My Feedback: (1)

Thanks, Andrew. I don't have any openings other than the one around the head and the one for the prop, obviously. I will cut some 'cowl slits' on the back and bend out the cowl slightly. That should make it look more scale anyway. I may also cut a hole in the bottom for additional ventilation.

GallopingGhostler

5x3 prop might be more effective in slowing 'er down. Nice build BTW. [8D]

combatpigg

My Feedback: (3)

Exocet, you might have experienced fuel foaming... that causes an engine to go lean after the model has been released. Overheating in a poorly ventilated cowl is a possibility. A 5x3 prop will also put less load on the engine, to help with runaway heat build up.
Make sure to run 25% oil as an easy thing to try.
If the model is nose heavy, it will be easier to "tip stall" because it doesn't distribute the weight across the full chord of the wing properly.

exocet-RCU

My Feedback: (1)

Thanks, GG and CP. Will make sure I have 25% oil and, if the holes in the cowl don't help with the engine performance, I'll try the smaller prop. I will make sure the tank is well wrapped in foam, too. I'm using an external tank, not the one that comes on the reedy.

Tim

GallopingGhostler

Tank orientation and fuel line length is more critical with the 1/2-A's, as their venturi suction ability is less than with larger engines. That may account for changes in performance as fuel dwindles down, engine goes more lean. It's why some manufacturers used to make tank mounts, which placed the fuel tank as close as possible.

exocet-RCU

My Feedback: (1)

GG,

The line is less than an inch long. In fact, the brass tubing of the tank sticks through the firewall into a hole in the back of the reedy tank and a short piece of tube connects it to the pick up nozzle on the needle valve of the reedy. It was a real 'treat' to connect it up but it works well. I'm using a 1 ounce round tank. I didn't notice any foaming in the fuel when I went to pick up the plane off the field but I suppose it could have dissipated. I had some foam rubber holding the tank in place but hadn't wrapped the entire tank in foam.

Hopefully I can have the repairs done by this weekend and can test out some of these theories. Thanks for the advice. I always learn things on this forum.

Tim

combatpigg

My Feedback: (3)

The fuel settles very fast from the foamy state. Just holding the model when it is running can dampen the vibrations enough to cancel out the foaming. Foaming can be hard to witness but easy to cure.
I've had great results with the 1 oz round tanks but make sure to rig the tank so it can't roll after it is installed.
I've stupidly built "pinches" into some set ups that caused intermittent trouble and I've seen other flyers battle crappy tank plumbing jobs enough times to suspect this as a common cause of unhappiness.

colmo-RCU

Enjoy, it will fly great. Mine had a norvel 061 and I dont think I ever ran it full throttle. Be careful when pulling up, mine stalled hard when too tuch elevator was used at medium to high speed. That's how I lost it.

exocet-RCU

My Feedback: (1)

That's a beautiful Zero, Colmo-RCU!