Aerodynamics Design Test Aircraft- the AXY-9 (Full Version)

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Lafayette -> Aerodynamics Design Test Aircraft- the AXY-9 (4/10/2008 11:45:30 AM)

Well, hi.

I think that the airplane will definitely fly. I found a very useful and quite an accurate online aerodynamics calculator on www.RCAdvisor.com . This is a very nice calculator which is meant for electric airplanes- but suites gas airplanes as well. I hope there will soon be an update to the calculator with gas engines . If you want to go there, become a member of the site for FREE and then you can use all the features of that calculator. That calculator counts drag ans lift and their coefficients, and all the other things like zero lift angle, wing loading and all that. So, here is what I came up with:

Airplane Dimensions:

Wingspan total = 147.9 cm

Length total = 123.2

Height total = 31.4 cm w/o rudder

Specifications:


Airplane Efficiency at 100 % Thrust at 60 km/hour:


Wing Loading = 28.464 oz/ft^2

Wing Lift = 2.5 kg

Thrust = 1.468 kg

Wing Reynolds Number = 109.906 k

Total Drag = 0.108 kg

Climb Rate = 320.088 km/hour or 88.913 m/sec


Airfoil Efficiency at 100 % Thrust at 60 km/hour or at .49 % Mach Speed:


Lift Coefficient = 0.404

Drag Coefficient = 0.025

Pressure Drag Coefficient = 0.019

Zero Lift Angle = -2.195


Guys, please tell me is the height of my airplane okay? Because I have small doubts on that if 31 cm will be okay for a 1.5 meter span wing. Will it be okay or should I make it smaller? Keep in mind the airplane will have to fly with a .50 and max .60 gas engine.

Thank you,
Yishht.



dick Hanson -> RE: Aerodynamics Design Test Aircraft- the AXY-9 (4/10/2008 2:21:34 PM)

Increase vertical fin aprox 10-15%
At low speeds you will most likely get some undulating yaw with your setup I don't lnow anything about design work using calculations- but I do know what works and what does not work well.
The lateral area forward the CG and the wing layout n spani are the reasons I say this---
It will provide for very effective rudder -as shown- but NOT best yaw stability .
Your layout is much like I use for my aerobatic stuff -that is - lots of lateral area on fuselage with NOT a lot of vertical fin --the object is to keep the CP of the fuselage (on it's side ) - as close as PRACTICAL to wing cg- this allows for a far smoother roll as the fuselage needs to pitch very little to maintain during the roll.
A good stable setup is a trade off - IF you only are after a nice stable model with very limited aerobatics - increase the vertical fin -
The reason a lot of "it looks about right" setups work, is that - is IS about right.



HighPlains -> RE: Aerodynamics Design Test Aircraft- the AXY-9 (4/10/2008 2:29:48 PM)

Well, I am pretty sure a 5.5 lb airplane is not going to have a climb rate of 88.9 m/s with any .50 engine. So I wouldn't put too much faith in the accuracy of the online performance calculator.

The design looks fine, except it looks like Carl Goldberg designed it (if one part would do, use two or three).



da Rock -> RE: Aerodynamics Design Test Aircraft- the AXY-9 (4/10/2008 2:59:32 PM)

Horizontal stab might be ok for small electrics, but even for them would be fragile. And it appears the fin/rudder are sheeted? If you are building a small electric, open structure as on the elevators and rudder makes sense. If you're going to sheet anything in the empenage, sheet the stab. In any case, the LE and TE of the stab should be robust enough to at least support the hinging and model handling. For a 50-60 engine unless the stab/elevator is sheeted, that structure is going to be dangerously weak. And if it is going to be sheeted, lose the TE sticks on the Elevator.

Is that a huge hole in the aft fuselage sides? If you wish to lighten slab sides, it works better to break that huge hole up into a series of holes. Place them between the fuselage bulkheads, and you get a tremendously stronger fuselage. As shown, the empenage would lose quite a bit of resistance to twisting that it has no reason to lose. A 50-60 engined airplane isn't going to need a huge amount of lightening in the aft fuselage sides.

quote:

Guys, please tell me is the height of my airplane okay?
Depends on what you mean by "height". Ground clearance is dead simple to figure. Consider the largest prop your engine could use and whether or not you fly off of grass.

It's not clear on the plans where the wing actually is in the sideview and it's relationship to the main gear, but it looks like the main wheels are not located far enough aft if the wing is located where it seem to be. You want them behind the CG range enough that there is enough weight on the nosewheel that it has adequate traction and the airplane has no tendency to "sit down on it's elevators". The attachment shows a very popular, accepted design for the mains on a tricycle gear model.

Also, look at the proportion of nose length to fuselage length on the attachment. It's not clear on your sideview, but if the wing is where it seems to be, your nose is a bit long. Long noses give you fits trying to locate the CG.

Are you making provision for removal of the wing?



Lafayette -> RE: Aerodynamics Design Test Aircraft- the AXY-9 (4/10/2008 3:10:30 PM)

Hi,

Thank you guys for all of your comments. I was really scared of reading them, as if before a major exam. I was working on these plans for about a month, and I drew over 50 different fuselage shapes. Today I will try to print out my plans with a poster program. I do not have a 1.5 m side paper, so I will have to spliut each section of my plan on an A4 sized sheet of paper. Guys, I heard you can do this kind of splitting and keeping the scale right on Adobe Acrobat or Adobe Reader or whatever. I will have to print not at my house but at someone else's who cannot install a poster program. HOW do I do this splitting on MS Word, or Adobe Reader, or any other conventional program not a one from the interenet. Thank you.

Yishht.



dick Hanson -> RE: Aerodynamics Design Test Aircraft- the AXY-9 (4/10/2008 3:53:42 PM)


quote:

ORIGINAL: Yishht87

Hi,

Thank you guys for all of your comments. I was really scared of reading them, as if before a major exam. I was working on these plans for about a month, and I drew over 50 different fuselage shapes. Today I will try to print out my plans with a poster program. I do not have a 1.5 m side paper, so I will have to spliut each section of my plan on an A4 sized sheet of paper. Guys, I heard you can do this kind of splitting and keeping the scale right on Adobe Acrobat or Adobe Reader or whatever. I will have to print not at my house but at someone else's who cannot install a poster program. HOW do I do this splitting on MS Word, or Adobe Reader, or any other conventional program not a one from the interenet. Thank you.

Yishht.

The shape - is not the real problem here - and a larger fin is the quick fix for shape - OR just move the wing forward about 3/4 of the chord
The structural setup you have for the wing is a problem- tho it is like some kits - th spar setup has a real stress riser (weak point) close to the fuselage
Keep your spars topand bottom fully integrated -that is -add shear webbing from top to bottom spar for atleast half the wing span
If yo ulook along th fuselage then pretend yo are trying to break it - look at the intersectionswhich do NOT distribute load
A really good model is not so much the "airfoils and ratios etc., but in how you distribute loads so nothing breaks
if yo play with this awhile --you will see how weight need not build up -as strength builds up.
Look closely a 1980's bridge designs They had same problems - distributing strength-without a lot of material.
Your tailgroup is also weak at root odf stabs -If you cant change the structure - add a thin wire external ,interconnecting support from fin to stab -to fuselage - which is 360 degrees around



BMatthews -> RE: Aerodynamics Design Test Aircraft- the AXY-9 (4/11/2008 12:45:11 AM)

Yishht, this topic should have been kept with your other thread in the Scratch Building forum. The topics here are still easily related to the othet topic. It's considered as slightly bad manners to post multiple threads about the same or closely the same topic in different forums.

To everyone that wants to reply to this thread please post your replies to....

http://www.rcuniverse.com/forum/m_7336526/tm.htm



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