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Audax F3A - new project for 2013

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Old 03-29-2013, 10:53 AM
  #1
Alex Voicu
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Default Audax F3A - new project for 2013

While still working on the kit version of my [link=http://www.rcuniverse.com/forum/m_10970855/tm.htm]Radiance[/link] model, i started thinking about my next pattern design. I initially started with a modified, composite version of Radiance, but soon decided to try a completely different design, one that would use the advantages offered by Brenner’s contra drive, meet its specific requirements and still work well for conventional setups with a single propeller. I probably made over a hundred hand drawings and dozens of 3D models before settling on a design, but in the end i’m happy with the result.

The requirements of the contra drive and single propeller setup may seem quite different: while the contra favors the low drag fuselages, the single prop monoplane designs of today have more and more side area for better knife edge performance during rolling maneuvers. My solution was to create a clean, streamlined design with low form drag but with lots of side area, so I eliminated any sharp edges and completely integrated the canopy into the shape of the fuselage. Using my experience with Radiance, i tried to optimize the side area distribution along the fuselage, which will hopefully result in better handling in crosswinds. The vertical tail area is quite large to increase directional stability and has a flared rudder to eliminate yaw sensitivity.

The wing design features a high taper ratio for fast snap rolls and elliptical tips for improved efficiency of the wing. In my view the multiple rolls on the vertical uplines require a very delicate balance of the model; if the ailerons are almost full span, deflecting them for the vertical roll may influence the airflow over the stabs and therefore deviate the model from the perfect vertical line. That’s why I plan on using split ailerons; normally only the outboard ailerons will be used, but when switching to snap roll flight mode both inboard and outboard ailerons will work together.

The name of the new model is AUDAX ; for now the plan is to build a full composite model, but the light weight of the built-up balsa wings is quite tempting so I may design a wood version later. I will post here images of the progress so far.

I attached 2 images of the model in plain white so you can clearly see its shape and proportions.
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Old 03-29-2013, 10:55 AM
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Alex Voicu
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As usual, designing a color scheme that works with the shape of the model was the most difficult part for me; i tried creating a new color scheme from scratch but most of the times what seemed great on paper didn’t quite work when applied in 3D. In the end, i took my old Radiance color scheme, changed the colors, changed the lines here and there and with a lot of work, the results were quite pleasing.







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Old 03-29-2013, 11:35 AM
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BEAUTIFUL is all I can say. Keep us informed of your progress.
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Old 03-29-2013, 12:25 PM
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Stunning work so far, Alex. I'm looking forward to seeing this airplane progress.
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Old 03-29-2013, 12:31 PM
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Default RE: Audax F3A - new project for 2013

I'm looking for the [[BUY NOW]] button!  No seriously, it looks like one sweet F13 machine and I'm just not there yet LOL. Cheers!
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Old 03-29-2013, 02:43 PM
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Living in Queensland, Australia our State motto is "Audax at Fidelis".

While hardly a scholar of Latin, I had to laugh during a program about ancient Rome where one persons profession was written as "OBSTETRIX". Not hard to figure that one out
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Old 03-29-2013, 05:45 PM
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Default RE: Audax F3A - new project for 2013

compilation of Caelestia ZNline, Gaudius JM and Sebart.
Nice work but nothing, sorry but nothing new.
Alex, i know you can do much more. Just keep your things. Not others.
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Old 03-29-2013, 07:01 PM
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Nice work Alex! Really like your color scheme too!
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Old 03-29-2013, 07:47 PM
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Default RE: Audax F3A - new project for 2013

Very interesting concept, your theory for the design makes sense, I hope the model will fly to your expectations. very nice lines and very pretty.

Alejandro
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Old 03-29-2013, 09:23 PM
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I have no words.. the plane looks awesome..

What 3D software do you use?
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Old 03-29-2013, 11:01 PM
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Alex Voicu
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Thanks everyone for the kind comments, i'm glad you like it

I will soon add pictures of the building process.
The CAD software i used is Solidworks 2007.
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Old 03-30-2013, 05:08 AM
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Default RE: Audax F3A - new project for 2013

Beautiful!
Alex, I'm curious as to why you and other designers rarely put the wing on the thrust line? I don't know that that is better, but it seems to make sense to me.
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Old 03-30-2013, 06:31 AM
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Default RE: Audax F3A - new project for 2013

Will these be in glass composite and carbon composite versions? I really like your Radiance model but  I just don;t have the time to build that intensively
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Old 03-30-2013, 11:21 AM
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Thanks for sharing I love the design.
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Old 03-30-2013, 11:51 AM
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Quote:
ORIGINAL: underdw

Beautiful!
Alex, I'm curious as to why you and other designers rarely put the wing on the thrust line? I don't know that that is better, but it seems to make sense to me.
I don't know what other designers think, but in my opinion the wing provides the lift but it's the stab that keeps the plane tracking straight. I placed the stab on the thrust line so it's in a more neutral position. The wing is placed a little lower to keep the stab in clean air, away from wing interference.

Timble, the plan is to have a full composite model. Carbon will be used only in the nose of the fuselage, the rest is glassfiber-airex sandwich.
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Old 04-01-2013, 07:12 AM
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Default RE: Audax F3A - new project for 2013

Work started in december with CNC programming and simulation of the milling process. The available CNC router was not large enough, so i had to split the fuselage in 2 parts.
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Old 04-01-2013, 07:24 AM
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The CNC router had very limited travel on the Z axis and also the tools available were very short, so i decided to cut the fuselage and canopy together and separate them later. The fin was very thin and flexible at the tip, so i used a block of balsa to mill the fin tip separately.

Material was a block of polyurethanic foam made of a few 30mm sheets glued together.
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Old 04-01-2013, 07:25 AM
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Default RE: Audax F3A - new project for 2013

Alex, when do you anticipate completion of the mold?
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Old 04-01-2013, 07:30 AM
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Default RE: Audax F3A - new project for 2013

Ryan, the fuselage mold is done, currently working on the canopy mold. I'll post here images with all the steps of the building process.
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Old 04-01-2013, 07:39 AM
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I really enjoy looking at all the pictures, very nice.
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Old 04-01-2013, 10:59 AM
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Quote:
ORIGINAL: przytek

compilation of Caelestia ZNline, Gaudius JM and Sebart.
Nice work but nothing, sorry but nothing new.
Alex, i know you can do much more. Just keep your things. Not others.
Some people just can't help but be negative. Why post a comment like this at all?

It's a beautiful airplane, Alex!
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Old 04-01-2013, 12:09 PM
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Right Doug,

Looks great to me, looks like a progression from his last design.
outstanding work!
There are a few new designers out there coming on strong with modern tools, and Good efforts,
Like Mark Hunt and Alex. I think thats Great and what this sport needs.
This keeps us all excited and even the old guys can learn from this

Bryan
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Old 04-01-2013, 12:10 PM
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Default RE: Audax F3A - new project for 2013


Quote:
ORIGINAL: Alex Voicu


Quote:
ORIGINAL: underdw

Beautiful!
Alex, I'm curious as to why you and other designers rarely put the wing on the thrust line? I don't know that that is better, but it seems to make sense to me.
I don't know what other designers think, but in my opinion the wing provides the lift but it's the stab that keeps the plane tracking straight. I placed the stab on the thrust line so it's in a more neutral position. The wing is placed a little lower to keep the stab in clean air, away from wing interference.

Timble, the plan is to have a full composite model. Carbon will be used only in the nose of the fuselage, the rest is glassfiber-airex sandwich.


Excellent, thanks Alex. I agree, stab on the thrust line minimises tracking issues. Also consider having the area of the ruder equal above and below the thrustline although this would need to be considered in conjunction with fuselage volume above and below the thrust line too.

Your targeted construction should see it coiming in at a reasonable price.


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Old 04-01-2013, 12:43 PM
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Default RE: Audax F3A - new project for 2013

Fantastic work Alex!

I am very interested to see how that wing planform performs. It looks like a winner to me.

Best of luck

Jeff
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Old 04-04-2013, 08:50 AM
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Default RE: Audax F3A - new project for 2013

Thanks a lot, reading all the nice comments is really encouraging.

The next step was to assemble the fuselage mold plug from the CNC machined parts. From this point on, i worked together with my friend Horia Florian; he has a lot of experience with composites and his work includes a full scale glider.

As mentioned before, the fin was a little flexible, so i added a plywood former at the back to solve the problem. The tip was cut off and later replaced with the balsa milled part.

We used an aluminium profile on the center line of the fuselage mold plug to make sure it stays straight and stiff. Since the fuselage and canopy were milled in 1 piece, i had to design a jig for separating the canopy. The jig was laser cut from MDF and after using some filler and sanding, the result was pretty good.

We also glassed the mold plug using 2 layers of 160g FG cloth.
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