Design check

[UnknownTarget]

So I did the numbers up from this design, using a combination of the plans for the SPAD BOHOR .25, some web references, and some equations I got from one of my aerodynamics books. This is going to be my first plane, as I have a class in composites and I figured hey, I might as well build something fun. Here are the full details of the design minus the actual geometry, which is what I'm doing next on the computer to be made with CNC cut foam.

Here goes;

Wing:

Airfoil: Clark Y

Area: 720 in^2

Span: 71 inches

Root/Tip Chords: 10 inches

Dihedral: Low wing, 5 degrees.

Aileron Span: 65 inches

Aileron Length: 1 inch


Tails:

Distance 25 inches from MAC of tails to MAC of wing.

Vertical Tail:

Area: 81.8 in^2

Root: 8.8 inches

Tip: 4.6 inches

Height: 12 inches

Horizontal Tail:

Area: 129.6 in^2 (all moving)

Span: 19.7 inches

Root: 8.8 inches

Tip: 4.4 Inches

General:

Length: 3.95 feet (47.4 inches)

Target max weight: 40 oz.


Electronic info:

Motor: http://www.commonsenserc.com/product_info.php?cPath=51&products_id=297

ESC: http://www.commonsenserc.com/product_info.php?cPath=52&products_id=313

Reciever: http://www.commonsenserc.com/product_info.php?cPath=58_66_67&products_id=458

Battery: http://www.commonsenserc.com/product_info.php?cPath=37_31&products_id=47

Servos (x3): http://www.commonsenserc.com/product_info.php?cPath=58_78_61_65&products_id=488

I think the prop is going to be about 9 inches in diameter. I don't have the weight + balance spreadsheet with me at the moment but I'll post that later.


Anyway, any thoughts? Thanks!

[HerkS]

Here are some approximate numbers - some of which may be of interest to you.

No guarantee that they are highly accurate. You can put in your own numbers and play with them.

[UnknownTarget]

Woo boy, thank you for that! Are the calculations for the Reynold's numbers accurate (you said it was all approximate, did you mean just the results?).

[HerkS]

Hi Target

RN is reasonably accurate. When you get into slicing it really fine, it depends upon whose atmosphere tables you use.

By approximate, I mean things like: the Cl of the airfoil is not equal the Cl of the wing. For those calculations you are using the Cl of the wing - which depends on aspect ratio, planform and RN etc etc. Same with the propeller numbers - you have to estimate the efficiency - big heavy plane-small prop=lower efficiency, small light plane, big prop=higher efficiency --- if you get my drift.

[nmasters]

Hi, UnknownTarget--

Herk is a real engineer. That means he knows when to be Felix and when it's ok to be Oscar. :D You can trust his numbers

As far as Re goes. The actual Reynolds numbers that your plane flys at will vary from day to day because the density and viscosity of air are affected by temperature and humidity. The tables he referred to obviously can't take that into account

--Norm