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earthsciteach's STOL Build for the "Contest"

earthsciteach

Moderator
Moderator
If you had been diligently reading my build log you would have known that I don't have a scrap piece of wood large enough to carve into a form for heat shrinking. Its like you don't even hear me anymore...
 

earthsciteach

Moderator
Moderator
Thanks, Jimmy. My release agent isn't releasing so well, though. I'm hoping to safe the form as I think it will stand enough heat for vacuum forming with plastic sheets. Now, why didn't I think of that before? :confused:
 

earthsciteach

Moderator
Moderator
Vacuum forming FAIL!

I haven't made any progress on the STOL build in a couple of days and I'm starting to feel the pressure! Other guys are already getting their planes stuck in trees and such. So, I took a few minutes to vacuum for the cowling. Well, at least TRY to vacuum form it...

Here's my little vacuum forming setup:

DSCF8251.JPG

I based this on this guy's video:

In the process, I COMPLETELY forgot the lessons I learned from making cowlings for my Super Cub. There is a trick to getting the right ratio of plastic sheet size to form size. I had built a smaller frame for my Cub and should have used that. The larger frame I used for this had too much material and did not allow it to draw down tight on the form. So, adjusted the height of my form, tossed the sheet back into the oven for reheating and here's the sad result:

DSCF8254.JPG

By doing this, I do now have the confidence that I can heat shrink a 2 liter bottle of the glassed form without melting the foam. I hit it pretty hard with the heat gun with no ill results. You were right, FM. As luck would have it, there is not a single two liter bottle in the house at the moment.
 

earthsciteach

Moderator
Moderator
Well, Ive pretty much dedicated today to making progress on the STOL build. Figured I'd post an update. The motor mount is almost complete. I'm using an 1100 KV, 480 class motor with a 12x6 prop and 30 amp esc. I covered it in microlite and she'll get trimmed out in black. Flaperons are covered, too. I still need to make the brackets to mount them below and behind the wing, but that'll be easy. Right now my biggest issue is finding an empty 2 liter bottle! I visited 5 neighbors this morning and they don't have any, either. Go figure. I'll scrounge some later at my bro-in-laws 50th party.

Still haven't determined exactly how I want to make the leading edge slats. But, with the Bat Bone kit and equipment on the way, I want to get this done so I can focus on that!
 

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quorneng

Well-known member
Earthsciteach
I am always a little wary of big flaperons in a true STOL application where the plane is taken well below the 'clean' stall speed.
If you are using them dropped significantly (over 45 degrees) the lift does not change that much with any further angle change but the drag does. This means big aileron movements are required to bring the wing level which in turn results in an even bigger adverse yaw.
I hope you have a big enough rudder to allow you to safely use the full power of the flaps. ;)
 

earthsciteach

Moderator
Moderator
I debated flaperons vs flaps. I decided to stick with flaperons because that's what the plane I modeled it from has. I really exaggerated the tail control surfaces for low speed. I fly flaperons on my HZ Super Cub and am pretty comfortable with them. Worse case, I'll split the flaperons into ailerons and flaps. I have plenty of area to do that.
 

earthsciteach

Moderator
Moderator
Yes, I am. Funny, less than a week ago I was completely banished to the basement. Now, I'm back! LOL!

So, now the motor is mounted on the plane. She's coming together fast, now. I think I'll tackle the flaperon brackets, next and get those installed. Still waiting for inspiration of the leading edge slats.
 

Attachments

quorneng

Well-known member
The laws of aerodynamics suggest that at model sizes slats are of little benefit.

Unless you have a greatly exaggerated gap the airflow through the slot is so restricted by the boundary layer as to have very little influence on the airflow over the wing.
With a wide gap the slat itself can add significantly to the effective wing area so reducing the stall speed.
It will be interesting to see your results.

This is all getting very serious!
.
 

earthsciteach

Moderator
Moderator
Thanks for the advice, quorneng. The Kitfox doesn't have leading edge slats, so it won't impact the scale of the build if I don't use them. I may fly it first, then add them on later to see if it makes a difference. Didn't think about boundary layer, but that makes perfect sense.
 

Tritium

Amateur Extra Class K5TWM
The laws of aerodynamics suggest that at model sizes slats are of little benefit.

Unless you have a greatly exaggerated gap the airflow through the slot is so restricted by the boundary layer as to have very little influence on the airflow over the wing.
With a wide gap the slat itself can add significantly to the effective wing area so reducing the stall speed.
It will be interesting to see your results.

This is all getting very serious!
.
Alright, I have to ask this: are you known as "Flux" on any Renewable Energy Forums specifically Windpower?

Thurmond