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Old Apr 04, 2014, 08:34 AM
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To Whacker Fly or NOT to Whacker Fly, that is the Question

I'm well on my way to completing an 84 inch 900 sq in. wing, for a scratch Ultra Stick clone, less than 9 lbs gasser. In case anyone doesn't know yet, I have had this Homelite 25cc in a box for a few years, just sitting there annoying me because it is already converted but not in a plane flying.

I'm at a turning point where I could go with a DLE 20 or Turnigy 26cc and get a bit more performance on 1.5 lbs less weight. The Homelite gets 10.5 lbs thrust, 8000 rpm with a wood Master Airscrew 16x8. I think it would make a nice cheapo sport flyer. But I see all these videos of converted weed whacker engines ON A TEST STAND but few in anything but stuff like an occasional 12 lb SPAD or other overweight scratch builds.

Also it looks like that big flywheel would make LOTS of drag, maybe a few lbs at 60 mph.

So does anyone know FROM EXPERIENCE is there any real reason it would not work for a sport plane and simple aerobatics ? It sort of worries me to imagine that heavy, almost 4 lb motor sticking out on the nose vs a 2.5 lb RC engine that makes about +1 hp.
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Old Apr 04, 2014, 08:51 AM
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BTW, using the converted engine could save me $300 on a simple Stick that only does some loops, rolls, hammer heads, Immelmanns, etc, and just fly around. That is the serious question. It seems I might get a few years of simple fun out of it.
But as I said, I only seem to see them (converts) on a test stand, not flying.
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Old Apr 04, 2014, 01:47 PM
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We used to fly them all the time like that before electronic ignition systems came about. The engines worked fairly well too. So yes go for it. Yeah they might be a bit on the heavy side, but with big airplanes it isn't a big deal. You can also use a servo controlling a switch for the engine cutoff too.
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Old Apr 04, 2014, 02:23 PM
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I did start into this last year but backed out. If I can complete the airframe all minus the motor at 8 lbs then I'll go on with this Homelite. If it goes well on gasoline then I'll try an ARF and RC designed engine.

I keep worrying the motor is so heavy it will break off of the nose after some landings.
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Old Apr 04, 2014, 03:35 PM
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So. Just glue it back on. No big deal. Then start practicing softer landings.
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Old Apr 05, 2014, 04:25 AM
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Funny funny, now that I have your attention, do you have a preference for a trustable tank air inlet that doesn't leak gas back out, and a good clunker ?

My wacker tank lid has a porous disk that seems to let air in but keeps gas from leaking. I could maybe go on and use the disk in a tube that sticks out of the plane to keep any leaks from dripping inside the fuselage.
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Old Apr 05, 2014, 04:46 AM
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Originally Posted by Chophop View Post
Funny funny, now that I have your attention, do you have a preference for a trustable tank air inlet that doesn't leak gas back out, and a good clunker ?

My wacker tank lid has a porous disk that seems to let air in but keeps gas from leaking. I could maybe go on and use the disk in a tube that sticks out of the plane to keep any leaks from dripping inside the fuselage.
Hi there chop chop , have a look at that other giant forum how they loop there vent line around so it doesn't leak out . U do want it exiting the fuz though .No need for a special cap or any thing . U may want a filter (or not ) on that line as well . Cheers the pope
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Old Apr 05, 2014, 05:04 AM
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Tanks, I'll have a look.
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Old Apr 05, 2014, 06:53 AM
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What I do is on the smaller gas engine powered planes is route a longer vent line above and below the fuel tank. Thus I route the vent line up and make a half loop and have it go below the plane. Thus when the plane is right side up and inverted the fuel doesn't ooze back out of the tank. Now if you carried the plane by the tail and the tank is full it could dribble out like that.

I haven't had a plane big enough to use the multiple loops or coils of vent line around the tank yet. But some guys do that, especially if they mount the fuel tank over the CG point in the plane.

Here is a example with my NV-Engines GX-40 gas engine. The vent line is the clear tubing, it goes up above the level of the tank and then down below the level of the tank. It uses three lines on the tank, one for the engine, one to fill and empty and a vent. Both the engine and fill lines use clunks.



it is a little harder to see in this pic, but the vent line loops up over the spark plug wire and then back down under the plane.

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Old Apr 05, 2014, 07:56 AM
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Well, it's about $7 to $12 for a chainsaw check valve, if this works then I'll try to find a way to hide it, the tubing is a bit ugly. Sorry if it doesn't sound nice, I like that clean engine look.

I'm going to test a run back to the fire wall then make a circle around it.
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Old Apr 05, 2014, 08:23 AM
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Just glue it back on. No big deal. Then start practicing softer landings.
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Old Apr 05, 2014, 08:38 AM
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Yea but I have such a nice smooth prop, I may not get another one. It's a Master Airscrew 16x8 wood.
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Old Apr 05, 2014, 08:41 PM
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Just a comment about a 20cc in a 84"ultra stick, I have a 76" ultra stick. I don't know the weight but I use it for a beater plane to break in engines. I have run two different 20cc engines (rcgf and VVRC), both were slugs in the air. With a dle30 it flew great.
Edwin
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Old Apr 05, 2014, 08:47 PM
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I'm using an NACA 2410 airfoil, and if I can keep it 8 lbs or less, a pitch speed of just over 60 mph, I should be able to fly it from my short home strip out in a rural area. I have obstructions that keep me from easily landing the higher wing loading planes here. I have to land them at about 20 mph or less.
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Old Apr 06, 2014, 08:04 AM
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Yes that is not a bad way to do it. My Super Stunts has a 80 inch wingspan with flaps and was built very light so it doesn't weigh all that much. I have to use flaps for landings otherwise it just floats across the runway and won't settle down for that last little bit to touch ground. It does land ridiculously slow with the flaps down though. A 17cc gas engine sort of overpowers it. You can fly it around 1/4 to 1/2 throttle most of the time.
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