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Jan 13, 2013, 05:14 AM
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Finally she flies


After several crashes on my own I finally found someone to help me get this bird off the ground and land in one piece.

I had the post "plane is turning left and wont recover"
Heres what we found

Although the plane is rated for a small engine the .25 os which i have on it and by the way the largest recommended 2 stroke is under powered. it takes to much to get it up to speed. i haven't weighed the overall plane weight, but I only added an ounce of weight to balance in all directions, so i really couldn't get any lighter

So my conclusion is to put a bigger engine in the plane
dropping the 25 and putting a 46 in adds 5 ozs of weight and i can counter balance by moving the battery pack to the other side of cg

Also by the recommendation of the instructor is to remove some of the dehydril. its currently at 7" lift on the one side, measurement taking by putting wing flat on the floor. Ill reduce that to 4". this action is being taken due to the wind wanting to throw the plane around a bit, and there wasn't much wind at all.

But other than that the plane flew well after a long take off to get it of the ground. It needed no trim to fly straight which tells me that for a first build I was fairly accurrate and pleased with that outcome.

Ok I weighed the plane it weighs within specs of the [email protected] 4.5 lbs with wing loading of 20.16 oz/sq ft. by changing the engine it will bring wing loading to 21.93 oz/sq ft.

problem 2
the prop swings on a larger radius so larger tires will need to be installed to lift the plane higher off the ground so the prop doesn't get effected by close contact to the ground. im currently looking for lightweight tires so i don't bring the overall weight up any more.

lets see what i can find
Last edited by asusrick; Jan 13, 2013 at 07:22 AM. Reason: update
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Jan 13, 2013, 08:57 AM
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Congrats! Another alternative to prop clearance can be to extend the nose gear a little. You might also consider a Thunder Tiger .36. A lot of power in that small package.
Edwin
Jan 13, 2013, 09:35 AM
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Thread OP
thx edwin ill look into it and compare horsepower
Jan 13, 2013, 10:30 AM
Tampa,Fl
Dale 813's Avatar
I would like to know how you take dihedral out of the wing ?
Jan 13, 2013, 11:44 AM
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Well dale not an easy task
1 remove the sevo from the wing , my ailerons share a single servo so its in the middle of the wing

2 break out the trusty rusty back saw, called a miter saw if your not a carpenter

3 saw away

4 now this is an important step, because im removing material due to the sawing and having to reshape the slope of the balsa through hand sanding, add a 1/4" piece of balsa to each side marking and cutting holes for the wing joiners that must be replaced.

5. taking careful measurements make sure both wing-halves are the same length.

now start the sanding process to achieve the new angle.

put some wing joiners that where custom made from some ply from the hobby shop

and wallah a reduced dehedral

I was a cabinet maker for 30 years this one was simple
Jan 14, 2013, 09:43 PM
I'm a pilot, 100 yrs too late
Thermalin's Avatar
I still dont understand why it was turning to one side.. the changes made would have no effect on that. Dihedral just adds stability...though the orginal 7".. I assume 3.5 at each tip is quite a bit.. The 40 is the correct size for 4 to 5 llbs.

Is this an older design. Back in the... motors in the 20 range were routinely used heavier planes.
Jan 15, 2013, 02:02 AM
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Quote:
Originally Posted by asusrick
..Ill reduce that to 4". this action is being taken due to the wind wanting to throw the plane around a bit, and there wasn't much wind at all...
Steady state wind won't do that - gusts will. Sounds like it flew great - I wouldn't change a thing.

Kurt
Jan 15, 2013, 03:36 AM
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Thread OP
I was going with a .46 but a friend gave me an older super tiger (mid 80s) .34. and after looking up the specs, my current motor puts out .56 hp compared to the supers .98 hp. we will try that before i take the plunge on a new motor. but the .34 still swings the same size prop so not sure if im gonna get the speed to shorten the take off, but we will see what happens

I have to concur about the gust it wasn't much wind like i side but a slight gust during flight really made the plane whip side to side, not an uncontrollable movement just a noticeable difference from the other planes flight characteristics that where flying that day.

The plane comes with specs for 2 different dehadril measurement and i choose the greater one, im just changing it to the least specs of the plane, it will still be a trainer just a little smoother during flight in windy conditions. there will always be wind during flying so i need to build to that
Jan 15, 2013, 09:20 AM
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Quote:
Originally Posted by asusrick
it will still be a trainer just a little smoother during flight in windy conditions. there will always be wind during flying so i need to build to that
The airplane is not aware of wind up in the air. It is moving in a fluid, just like a boat on a lake. All that matters to an airplane is its airspeed - the speed at which air is moving over its wings and control surfaces.

Gusts can make an airplane bump around, because the airspeed is changing quickly, and dihedral does have an effect in those conditions, but a steady wind makes no difference.

The effect you see of a plane with a lot of dihedral rocking from side to side in a gusty wind, is due to the airspeed changing unequally between the two wings, affecting how much lift they produce.
Jan 15, 2013, 05:03 PM
I'm a pilot, 100 yrs too late
Thermalin's Avatar
I'm tinking bouncing is more a function of the wind buffeting the wings, body, tails as opposed to wind traveling over the wings independently...that would mean you have micro gusts of diff speeds moving over the wings independently. With our spans of 4 to 5 or 6 feet.. that's not enough space to have gusts of different speeds. Just my thoughts.
Jan 15, 2013, 06:17 PM
Registered User
You're probably right, and the air near the ground where we fly most models, surface to 200'-400' or so AGL, is often pretty turbulent, so there's almost always some up-/downdrafts, possibly some sheer, etc. It's still in the region where air is bouncing off objects and doing all kinds of things.

The only point I wanted to try to make is, to give an example, when the plane's going upwind, and you bank to turn, and the plane starts moving sideways as viewed from the ground, it's because the plane's moving in a fluid that is itself moving, not because the wind is getting under the wing and blowing it over. It's a point I struggled with a lot.
Jan 15, 2013, 10:24 PM
I'm a pilot, 100 yrs too late
Thermalin's Avatar
I agree with that... flying gliders for many years... I learned a lot about wind and the micro environments near the ground... The river of air article by Steve Work, designer of the BOT I believe is a good read. Sort of like visualizing water moving through a stream and the objects, stones, branches, etc that are in the way and the turbulence the create.
Jan 26, 2013, 04:16 PM
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Thread OP
Put the wing back together with 1-1/2" dehydril. a little lower than i originally planned. i thought it would make it a little sportier. Also I was gonna put a spare 34 i had laying around but went for the OS 46 axii instead. I origanally calculated the the wing loading would be 21.93 oz/sq/ft but i also converted it to a taildragger. moved the batteries around and ditched some counter balance through the battery movement and got the plane to 20.49 oz/sq/ft, the origanal wing loading was 20.1 oz/sqft so im pretty pleased with that outcome. adding 3 times the horsepower with only 3 tenths of an oz/sqft gain on the wing.

not bad for an amature
Last edited by asusrick; Jan 26, 2013 at 04:24 PM.
Feb 19, 2013, 11:27 AM
Registered User
Nice re-work on the aircraft, you should be pleased with it. I personaly like tail draggers over the stupid tricycle gear. I had more hard landings and prop bites with a tricycle gear then I did after I converted my trainier to a tail dragger. Now all of my aircraft get the conversion if they don't already come as a tail dragger.
Feb 19, 2013, 02:07 PM
Registered User
Quote:
Originally Posted by F16DCC
Nice re-work on the aircraft, you should be pleased with it. I personaly like tail draggers over the stupid tricycle gear. I had more hard landings and prop bites with a tricycle gear then I did after I converted my trainier to a tail dragger. Now all of my aircraft get the conversion if they don't already come as a tail dragger.
There are about a bzillion of us out there who can fly "stupid" tricycle gear without "prop bites." You should give it a chance down the road.

Kurt


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