Mini Hog

Haiduk

Haiduk

New member
Hey all,

It's been awhile since I've posted here. Sorry, real life comes before RealFlight!

Anyway, now that winter is back, I've been deep in design and build mode since it's rare the weather allows for flying.

Usually my design process includes building a model for RealFlight to test things like airfoils, wing incidence, dihedral, thrust angles, control surface size, etc. Once I'm happy with the flight characteristics in the simulator I can start designing and fitting the actual parts in 3DS. From there I can extract the parts out to AutoCad to lay out plans and set up templates to lay out on balsa and light ply or to set up G-Code for laser cutting.

This project will be a park sized sport plane with the classic lines of the AstroHog. I'm shooting for a 40" wingspan aircraft with a flying weight between 20 and 24 ounces. Should be able to power it with a 400-480 sized outrunner.

So far, I've got the model for RealFlight is completed and I like the way it flies. At this weight and wing area the flaps are really not needed, but they are fun. I will probably set up the kit so flaps are optional. I've opted for slightly over-sized wheels for ground handling in grass.


MiniHog Tricycle version


MiniHog Tail Dragger version
 

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I just uploaded the initial RealFlight model for you all to check out. If it needs tweaking, it's best to get it done before I finalize G-Code for the prototype.
 
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:)

Hey Phrank! I'm back at the design thing. Still haven't broken down and picked up G5.5. It's in the plans, Maybe Santa will drop it off for me this year.

Need feedback on this plane. I want to start laying out plans and setting up templates for balsa cutting by the end of the year.
 
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#1 clear the CG over-ride. When building a real model you do not have a magic wand, adjust your CG by shifting the electronics or adding weight just like in real life.

Mostly everything is good, providing you can build that light (I have a Chipmunk in the same scale that has a similar weight, so I know it is possible). The only thing I saw was that you have a bloom with a rapid reduction of power, this is due to the aircraft fighting an offset of the engine and when you cut power the engine force is removed leaving unstable aerodynamic forces causing the plane to climb. So add a degree of down thrust on the engine and add a degree of incident to the horz stab to balance forces.

Doug
 
Doug,
Not sure what you mean to "clear the CG over-ride." Isn't 0,0,0 CoG in the editor based on 0,0,0 model coordinates? I just eyeballed the center model coordinates at around 27% of the MAC. I figure CoG will fall between 25 and 30% for this model.

I made a few changes to the physics model and reposted the EA. I saw the bloom that you spoke of. I fixed that by reducing the wing incidence. It was too much. H Stab and down thrust are both 0. I did increase the right thrust a bit and it did reduce the left roll under throttle. Maybe you would be kind enough to test it again for me?

EDIT: I added too much right thrust. I again reduced it back down so the plane tracks straight on the ground.


MiniHog with updated physics
 
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U-Bird wrote:
OUTSTANDING !!! Years ago in G2 someone made a CS for either the Flybaby or the Spacewalker with the Astro Hog scheme and I always enjoyed the plane as it looked good in the air.
This little plane flies good and I'd never given any thought to a Astro Gog with flaps. Interesting.....
 
U-Bird wrote:
You know, a full size or maybe a 80 or 90 inch Astro hog would be great. It was the Astro Hog that I learned to fly RC on back in 1978. It was a great old bird.
 
I had too much right thrust and neither the tricycle version nor the tail dragger tracked straight on the ground. I reposted both models with a more suitable right thrust. If you update your model, please remember to overwrite old files.

At this point I'll make further physics tweaks with AV's as needed.
 
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Haiduk said:
Doug,
Not sure what you mean to "clear the CG over-ride." Isn't 0,0,0 CoG in the editor based on 0,0,0 model coordinates? I just eyeballed the center model coordinates at around 27% of the MAC. I figure CoG will fall between 25 and 30% for this model.
Click to expand...
If you look under the Airframe section, you have a manual CG over-ride adjustment. Get rid of it, so that you can see where the battery, etc. should go in the fuselage.


Haiduk said:
I made a few changes to the physics model and reposted the EA. I saw the bloom that you spoke of. I fixed that by reducing the wing incidence. It was too much. H Stab and down thrust are both 0. I did increase the right thrust a bit and it did reduce the left roll under throttle. Maybe you would be kind enough to test it again for me?
Click to expand...
I'll look again, but I don't think you needed right thrust. The need for right thrust is apparent when you pull back hard on the stick and not while tracking on the ground. Most planes need a touch of rudder when starting off and before the virticle stab becomes effective.
 
dhk79 said:
If you look under the Airframe section, you have a manual CG over-ride adjustment. Get rid of it, so that you can see where the battery, etc. should go in the fuselage...
Click to expand...

I honestly don't yet know the weights of the individual components on the real model. I used approximate weights from a similar sized plane I scratch built last winter to get in the ballpark.

At this stage. I wanted to battery to be centered to make it easier to test different battery sizes without having to move them around.

Once I know the exact weights of everything, then zeroing out the CG over-ride makes a lot of sense. I will definitely be zeroing out the CG over-ride before settling in on battery placement and the battery hatch on the prototype.
 
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Just thought you should know............I Really LIKE IT!!!!!!!
 
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Still have the climb problem when power is cut. Also you now have too much right thrust causing the plane to veer slightly right in a tight loop. Your choice is to either use rudder on roll out or counter this thrust when trying to do aerobatics.
 
I went back in and zeroed the right thrust and yes, once again, you're right Doug. :)

It looks like I can stay with zero zero thrust angles on the firewall. Zero degrees on the horiz stabilizer and about 1 degree positive incidence on the main wing for the real model. I can further adjust thrust angles on the prototype with washers. You've been a great help Doug. Thanks man.

I'll be busy for the next few days setting up the parts for the prototype build. I'll check back here periodically.
 
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