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Old Jan 25, 2009, 02:17 AM
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Iso Octane's Avatar
Toronto, Canada
Joined Jun 2003
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Build Log
My scratch built F3A-style pattern parkflyer

Just wanted to share with you guys my build. I think The Workshop is the right place to post this since this will be more about the building/design process and construction methods than the type of airplane. I also hope this can be my little contribution to this part of the forum. This place has been the source of so many answers to so many questions. A quick thank you to everyone here for posting, asking, and giving advice.

Specs at a glance

Wingspan: 44"
Wing area: 300 sq/in.
Hoped for AUW: under 25oz.
Battery: 1300mah 3S1P
Motor: 150W outrunner

Design goal

A parkflyer sized sport plane that looks like a F3A 2-meter pattern bird.

A little back story

This project first started back in 2004. I know a lot of people don't, but I just love the look of those 2-meter pattern planes. They're just so sleek and modern. So I wanted something like that but smaller, and there just wasn't anything on the market at the time in the 100-150 watt range.

IIRC, it was Fliton that first started offering modern looking parkflyers with their Flubber and Jumping Jack . The JJ in particular really captured that F3A look. Nowadays we have lots of choices in good looking small pattern ARFs, from the Quiet Storm , to the Helios , and the Brio . Well I would've purchased a JJ back then except I wanted to build a kit. We're all familiar with the story about ARFs taking over. I was on my own, to build my own.


Working out the design


Before doing anything, know what you want to do, so they say. What are the characteristics of a F3A pattern bird? They look really cool! More specifically they tend to have a curvy smooth body. No ugly sticks here. They have lots of side area to help them knife edge, and the trend is to have lots of that side area up near the front which leads to a "cab forward" look, with the canopy above or slightly forward of the wing. These planes have tapered wings with a relatively high aspect ratio. Finally, and this is important, they have really funky noses. I think this is the only category of plane where the designers go out of their way to create interesting and unique noses with weird looking air intakes and flares and tapers and bulges. Most will probably find it a bit ugly, and some of them are, but I really like the "styling" that the designers do for these planes.

So off I went to scour the net in search of as many photos as I could. With my pictures laid out nicely in layers I drew a sort of "line of best fit" through a few of my favorites to come up with the profile and planform. Parkflyer was the goal, and I decided that 300 sq/in. was a good round number for wing area. Using Autocad it was easy enough to scale down the wingspan a bit at a time until I got the wing area I wanted. That span turned out to be about 44".

More to come...
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Old Jan 25, 2009, 09:41 AM
that tree ate my plane
rotccapt's Avatar
oklahoma city oklahoma
Joined Apr 2004
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very cool hope it all works out for you. i ran into the same thing with my extra 300s not too may kits of them so i decided to draw up my own havent started it yet but some time
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Old Jan 25, 2009, 12:44 PM
Zor
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Quote:
Originally Posted by Iso Octane

Just wanted to share with you guys my build.
>
> Please read post #1
>
More to come...
Hello Iso Octane,

A beuatiful design from a talented designer and builder.

I just love the shape, proportions and I can imagine the finished appearance.

Congratulations for a job well done. You can be proud of yourself.

What are you planning to use for covering?

Zor
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Old Jan 25, 2009, 04:05 PM
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Why the big elevators for a pattern plane?

Dave
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Old Jan 25, 2009, 05:19 PM
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Toronto, Canada
Joined Jun 2003
445 Posts
Thanks for the kudos guys! I'm quite happy about how it's turning out so far, especially since it's my first time building from my own plans.

I'll be covering the plane primarily with Microlite.

The elevator is bigger than what the reference photos call for, and that's because I couldn't resist the idea of some mild 3D.
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Old Jan 25, 2009, 05:37 PM
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Toronto, Canada
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Wing design and construction

The wing uses a NACA 0012 airfoil, decided upon after lots of digging through RCGroups. If I were to do it over, I'd choose something thinner like a 0010 (ie. 10% thick) to follow the current trend for thinner airfoils.

The planform posed a bit of a problem when it came to locating the spar. Convention says to lay the spar over the thickest part of the wing. That's fine for straight tapered planforms as the spar can be straight through tip to tip, perpendicular to the body. However for a swept tapered wing the spar would be angled. In order to join the two removable wing halves without using tubes I needed a perpendicular spar. So the wing has two spars, an angled one over the thickest part of the wing running the length of each wing half, and also a smaller perpendicular spar which will run through the body and join with the other wing half. The perpendicular spar is placed at the CG location.
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Old Jan 25, 2009, 05:53 PM
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Subscribed! Looks great!
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Old Jan 25, 2009, 07:06 PM
Zor
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Quote:
Originally Posted by Iso Octane
Wing design and construction

The wing uses a NACA 0012 airfoil, decided upon after lots of digging through RCGroups. If I were to do it over, I'd choose something thinner like a 0010 (ie. 10% thick) to follow the current trend for thinner airfoils.

The planform posed a bit of a problem
>
>
>
The perpendicular spar is placed at the CG location.
Iso Octane,

Just an idea.
The two spars forming an angle to each other and reaching to the wing tip could be joined as well using a small piece of sheet akuminum (dural) with a curve in it to match the angle.

It is too late for that now.

Negligeable added weight more than twice the strength.

QUESTION
I see what looks like green masking tape to hold the elevators in position and I see only two hinges for each elevator.

If I am correct, suggest you add a third. Think of what happens if one fails (break).


Zor
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Old Jan 26, 2009, 10:08 PM
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Interesting idea. I imagine the aluminum would join at the shear webs? Yeah the masking tape is just to hold it there for the photos.
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Old Jan 27, 2009, 12:04 AM
Zor
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Quote:
Originally Posted by Iso Octane
Interesting idea. I imagine the aluminum would join at the shear webs? Yeah the masking tape is just to hold it there for the photos.
Ya ... the aluminum part of the spar would be screwed and epoxyed to the root of the spar that would be laminated with plywood in that area.

What about the hinges? Read my posting again.
Do you have only two hinges on each elevator?
That is risky if one hinge fails the elevcator goes hay wire and loose its hinge line. There should be three hinges but for some reason I only saw two on each elevator.

Zor
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Old Aug 30, 2009, 10:06 PM
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Toronto, Canada
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It's finally finished!

The all important number... AUW is just 19.75 oz!

More to come as I sift through pics to upload.
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Old Aug 31, 2009, 09:02 PM
KE your cub.
Curare's Avatar
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Joined Jun 2005
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Definetely TLAR!

I can see the influences of the JJ in there, but you've come out with a nice F3A-P? model?

Looks like it should do rolling circles for weeks.


So what's next? A canalizer!? hehee
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Old Sep 03, 2009, 01:48 AM
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Toronto, Canada
Joined Jun 2003
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Canalizer, lol.


Removable Wings

Okay, more about construction. The wings are two-piece and removable. The left wing spar slots tightly into the right wing spar. Each wing half is then further secured to the fuselage by two 4-40 nylon bolts. The bolts go through the holes there on the side of the fuse.
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Old Sep 03, 2009, 02:10 AM
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That's a sharp looking model Iso!!!
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Old Sep 03, 2009, 08:57 PM
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Toronto, Canada
Joined Jun 2003
445 Posts
Thanks!

Landing Gear

On to the landing gear. The landing gear is removable as well. It consists of two gear wire legs bent to shape and supported by a section of 1/8th balsa all sandwiched between two pieces of 1/32 ply. The gear assembly is then slotted into the fuse and secured by a nylon bolt.

Credit for this sandwich and slot method goes to Stevens Aero, as something similar is used on their sport models and in the S.A Cap232 that I have. It seems to be an uncomplicated way of having removable wire gear and uses less wire than the traditional method of having two L-shaped pieces of wire side by side spanning the width of the fuse bottom.
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