2 Questions..... ok maybe 3...

[Ado]

Does anyone know what profile is used on the Aeroflyte Brolga 2? Aeroflyte dont have a webpage so I cant find any info on it. OR does anyone recommend a good profile for a 3m wing. i have to keep the root the same length and anything else can change from the original design.

Also, if i replaced the 2m wing with a 3m wing.. would I have to enlarge the elevator and rudder?

Cheers,

Ado

[Ollie]

One of the best 3-meter wing designs, both from an aerodynamic and a structural point of view is for Dr. Drela's Aegea. For the airfoils, see:
http://www.charlesriverrc.org/articles/drela-airfoilshop/markdrela-ag-ht-airfoils.htm
An efficient wing design isn't just a matter of airfoil selection. The airfoils must also be coordinated with structural design, planform, aspect ratio, twist and sweep for best results.

When replacing a 2-meter wing with a three meter wing, two issues arise. They are stability and control power. Pitch stability can be maintained by moving the CG forward some but some pitch control power will be lost. If the horizontal tail had control power to spare, then you might get away with it. Increasing span decreases yaw stability and yaw control power. Most vertical tail areas are marginal to begin with, so, it is less likely that you can get away with not increasing vertical tail area. To maintain the same stability and control power it is advisable to increase horizontal tail area in proportion to wing area increqse and vertical tail area by 50% (in proportion to wing span increase). If the tail moment arm length remains the same, yaw and pitch damping will degrade some, resulting in less "groovy" handling characteristics even with the tail area increases.

The increase in wing aspect ratio will result in reduced sinking speed and better glide angle. Any decrease in wing loading will result in even lower sinking speed.

In other words, you can probably get away with it but at some cost to maneuversbility and handling characteristics along with improvement in glide.

[Ado]

wow thanks Ollie!

I was going to build the rudder bigger anyway... its a little small as it is... might have to go even further. I think the elevator has plenty there but might go bigger just to be sure.

Thanks again for the info.

Cheers,

Ado

[Ollie]

You can check the adequacy of your tail areas and moment arms by applying Dr. Drela's criteria as follows:
Ch = (A_hori/A_wing) * (tail_arm/avg_wing_chord)
Cv = (A_vert/A_wing) * (tail_arm/avg_wing_span )

A well-sized tail will be in the range...
Ch = 0.35 - 0.50
Cv = 0.02 - 0.035
If the Ch and/or Cv are below the minimum values, the handling will suffer.

[Ado]

I worked out the areas for the vert and elevator.... 25796mm2 and 58096mm2.(yay for the area function in autocad :P )

The wing cord will be 203mm... but I dont know what the tip cord should be.

but right now my head hurts and I think the 3m wing will be too much for this plane. I think I might just go back and build up the 2m wing.. hehe.

Thanks for your help Ollie but all this is way over my head.. im still a "noob" when it comes to plane/wing design etc.

Cheers,

Ado

[dingo]

Gee , some one else has got a Brolga , whats the differance between a Brolga & Brolga 2 . An old bloke gave me the Brolga , he put maybe half of it together then left it sitting on a shelf for 6 years . He was at a slope one day & said I could have it . It took ages for me to finish it . I`ve gotta hand it to you blokes who build from kits & scratch build . I`ll stick to ARF .

[Ado]

Im not sure what the differences are sorry.

I dont mind the building... its the covering I dont like.

Cheers,

Ado