"1/2 A" & "1/8 A" airplanes These are the small ones...more popular now than ever.

Help me make it fly better.

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Old 08-12-2009, 06:40 AM
  #26  
Mr Cox
 
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Default RE: Help me make it fly better.

Hey, don't blame it on the engine... For a given power and duration glow is hard to beat, especially when it comes to repowering.

Do you have any weight numbers for the plane alone, without any installations?
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Old 08-12-2009, 02:22 PM
  #27  
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Default RE: Help me make it fly better.

This is the kind of project I like, where you try to make something that falls short of your goal reach that goal. I'm pretty sure this is the same plane that many of us here watched a beautiful 3D demo video of, powered by a .074. The plane was originally desined by Billy H@ll for electric.
This is also what makes 3D fascinating, there is so much more that goes into it than the usual boring stuff.
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Old 08-12-2009, 08:52 PM
  #28  
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Default RE: Help me make it fly better.


ORIGINAL: Zpat


ORIGINAL: BMatthews

You can try adding a rib bay to each wing but really the important issue is that the model is just plain too heavy. I'd cut your loses and move on to building a new model with more careful attention being paid to reducing the overall weight down to around 24 or less oz.
Your right.

This is an electric airplane. Glow engines are just too heavy for it.

WOW! Have the tables ever turned! A few years ago converting a glow model to electric was seen as basically slinging an anvil of extra motor and battery weight round the model's neck. Now we've got folks saying that glow is too heavy to let an electric model perform well. I never thought I'd see the day....

Things have come a long way and these days it's quite possible that a brushless motor, prop, battery pack and ESC totals the same or a bit less than a glow engine, prop, muffler, fuel tank, average fuel load and the throttle servo to run it all. Who'd have thought this would ever come to pass. Then add on the extra structural mass to absorb the engine's vibrations as opposed to the silky smooth torque from a motor and you've got a case were it's entirely possible for the engine powered option to actually be heavier overall.

Sorry Zpat, this isn't an answer for you but just a momentary modeling epiphany on my part.
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Old 08-13-2009, 02:42 AM
  #29  
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Default RE: Help me make it fly better.

I don't think that we are there yet. When someone actually tries to match the performance of glow with electrics, for more than just a brief moment of full trust, they still have problems. For instance there has been some local effort to match Q500 performance using electrics and it turns out very expensive and heavy...

I the box of an ARF says that it will weight 20oz on electrics and he gets 30oz using glow I would really like to see the actual numbers...

There are lots of weight savings that can be done and has already been mentioned in this thread, I haven't see any comments on that though.
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Old 08-15-2009, 05:17 AM
  #30  
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Default RE: Help me make it fly better.

ORIGINAL: Mr Cox

I don't think that we are there yet. When someone actually tries to match the performance of glow with electrics, for more than just a brief moment of full trust, they still have problems. For instance there has been some local effort to match Q500 performance using electrics and it turns out very expensive and heavy...

I the box of an ARF says that it will weight 20oz on electrics and he gets 30oz using glow I would really like to see the actual numbers...

There are lots of weight savings that can be done and has already been mentioned in this thread, I haven't see any comments on that though.
There's nothing left to remove. The landing gear is gone and the carbon pushrods weigh 7 grams. The engine weighs 6.6 oz. If I add structure it will just result in more weight.


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Old 08-15-2009, 08:39 AM
  #31  
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Default RE: Help me make it fly better.

I'm just trying to understand where the weight comes from, 6.6 oz for the engine leaves about 25 oz for the plane with installations (?) still sounds like too much to me...

Others have already mentioned tank and receiver battery, other points are servos and engine mount etc...
I once saved about 0.5 oz by replacing the foam protecting the tank and receiver, it all about saving a bit everywhere and it will add up to a lot at the end.
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Old 08-15-2009, 11:00 AM
  #32  
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Default RE: Help me make it fly better.

When a guy named Mr Cox speaks to you at the 1/2A forum....you had better listen to him [>:]!!!

I would build an exact sized replica of this plane from scratch, even if you need to dissect it to make patterns....but this time around down size all the materials that you can slightly and rig the plane as lightly as possible. The minimum fuselage thickness I've gotten away with for .15 power with no carbon fiber involved is 1/4" hard balsa sticks and 1/64" ply doublers up front. Too flimsy is no good either, it is a fine line.
Use one of those plastic eye droppers to dispense the thin CA and use a drop of medium CA instead of flooding a glue joint with thin. Diehard builders use waterbased glue to save even more weight after the water evaporates.
I'd either go with pull/pull control using Spiderline or put the servos in the tail. A .15 engine should counterbalance the weight in the aft end OK.
I've tried using HS65s all around but keep blowing out the one that controls the rudder. The problem is when the plane lands on the tail first and then breaks gear teeth. A wire skid in back should solve that, then the HS-65s should be fine for the long haul.
Cover the plane with floral wrap cellophane or some kind of ultra light hobby store film. I'll bet this version would end up weighing no more than 25 ozs, which will make the plane a lot more fun with a .15.
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Old 08-15-2009, 12:51 PM
  #33  
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Default RE: Help me make it fly better.

I removed the engine to get some real numbers.
Engine and muffler 10 oz.
Airframe, includes 4 HS-81's servos, Neutron 6 rx, Hydramax 750 mah battery ( 2 oz), switch and charger jack. 21 oz.
4 oz Fuel tank and lines 2 oz.
Tail surface servos are in aft fuselage to compensate for engine weight.

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Old 08-15-2009, 01:39 PM
  #34  
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Default RE: Help me make it fly better.

Now we are getting down to the real stuff.
Don't know what to tell you to do with the present engine but a brand new OS .15 LA weighs 5 oz w/o muffler (6.5 oz w/muffler). Weight savings? Substantial!

Surely there is a four ounce tank that weighs less than 2 ounces out there somewhere. You should also go smaller than a four ounce. I can't say exactly how much four fluid ounces of fuel weighs but it weighs a lot more than four dry ounces.

As CP was saying, go with a smaller on board battery. The covering? Granted a lot of work to strip off and recover but you might be surprised how much weight you can save there. Sometimes it depends on how dedicated to getting it like you want it.

It can be done.

Robert
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Old 08-15-2009, 02:22 PM
  #35  
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Default RE: Help me make it fly better.

Okey, seems like my nick-name is on the line here...

The set-up might be fine in a warbird and luckily there are plenty of place to save weight.

The engine numbers sound too high, I don't have the .15 myself but it is listed at 6.6 oz and the muffler should weight about 1.5 oz, so it should be around 8.1 oz (compared to the OS LA it has doubble ball bearings that gives the higher weight, but the power ought to beat the LA too). So 2 oz here that I don't know where they are comming from, Heavy spinner? (you don't need any spinner...)

- 2 oz to save

Fuel tank is heavy, there are more lighweight ones with a single tiny rubber stopper only. Or you make your own without any rubber stopper and a lightweight clunk.

-1 oz to save

The radio servos are a bit heavy I think and they also draw quite a bit of current, for the throttle one can use HS55 and for the others e.g. HS 65HB, the battery can then be dropped to about half the size of what you have now. Receiver is a bit heavy, the HS 5 is half the weight I think. Standard switch with charging lead? They are heavy too, there are lightweight ones...

- 2 oz to save

Standard covering instead of lightweight (?) I also spot what looks like quite a few plastic hinges on there...

- about 1 oz to save

Rear mounted servos add weight if you use standard extension, better to have them mounted in the front and to use lightweight pushrods or pull-pull, as suggested above.

-about 1 oz to save (if there are standard extensions to servos, including aileron servos)

This all adds up to about 7 oz to save, try a few of them and see what happens...
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Old 08-15-2009, 05:23 PM
  #36  
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Default RE: Help me make it fly better.

I originally bought this engine for a Westcoast Products 1/4 Midget Mustang. It didn't trip my trigger.
.15 size models are few and far between and I just happened upon this one.
I got disgusted with giant scale and the back breaking effort it took to get them to the field and decided to go smaller. At first it was .60 size fun fly models and then I discovered profile 3D and was a convert.
I'll probably give up on this one. At least I got some fuel through this engine and it is a good runner.

I want to thank everyone who contributed. I have no desire to throw any money at this one to get it to work.

Again, Thank You

Pat
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Old 08-16-2009, 05:27 AM
  #37  
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Default RE: Help me make it fly better.

Okey, I hope you have gotten some insperations now for your next build. Scratch building with weight considerations from the start can be very rewarding.

I'm doing this as a hobby, so time and money are always well spent by definition.
In fact I might have the opposite problem, I'm struggling to leave a plane alone even though it might fly just fine, can't help having to test some moderations...
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Old 08-16-2009, 02:26 PM
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Default RE: Help me make it fly better.

I scratched this one.
70" wingspan, 14 lbs, 1.80 Moki.
Have yet to fly it do to the profile projects.
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Old 08-16-2009, 03:22 PM
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Default RE: Help me make it fly better.

That's a beaut!
Will the Moki 1.8 hover it?
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Old 08-16-2009, 10:03 PM
  #40  
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Default RE: Help me make it fly better.

Well, 10 oz for a .15 and muffler is WAY over the top. Likely being an MVVS this is one of the fairly hot engines with the rather "portly" crankcases that adds up the wieght fast. But that's only part of the issues. The model itself with RC gear is still pretty heavy on its own at 21 oz for this size. I'm going to guess that the ARF itself is strongly overweight.

To call out an example a lot of years ago I built an electric fun fly that is 40 inch span with a HUGE wing. The bare framework less covering came in at 6.5 oz. With the light Solarfilm covering I gave it I don't think it gained more than 2 oz at most. Adding radio gear probably put on another 4 to 6 oz (it's been a long time and I don't remember what all I put into it). But I'm still way under your 21oz with a bigger model to boot. I think the issue isn't the gear and engine, although that's a porker of a mill and muffler, but more about the poor numbers on the ARF as delivered. Basically I think it came to you with the deck stacked against you.
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Old 08-17-2009, 01:47 AM
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Default RE: Help me make it fly better.

Pig,
Thanks. I'll see if it will fly straight and level first. I don't think it will be a 3D monster.

BM,
This is a kit. It's the rage with electric power.
I do remember the bare airframe weight was less than the engine.

I've added pictures of the airframe. Not much structure left to remove. I relocated the tail feather servos in the initial build to reduce the nose weight. I thought it was balanced. It was uncovered but I don't think .2 oz/sq ft (That's what they claim) would make much difference. It is extemely pitch sensitive. I'm running -60 expo (Futaba) . I had a first time airplane flyer fly it (3D helicopter flyer)
and he had no trouble with flying in figure 8's and loops.

I moved the engine 1 1/2" forward to compensate for the tail weight.

Maybe it won't be so pitch sensitive and will do something different.

Don't make too much fun of my state of the art weight measuring equipment.




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