Basic Aeronautics

[Brian Clarey]

From the attachment above, it will be seen that the script for dimensions are written in reverse order ie; Aw for wing area. Also that it is an extract from the book Thermal Soaring by George Stringwell. The dimensions shown are typical for gliders , power models would have approx. 20% larger chord. So the table still applies

Brian C

[KENNYGLIDE]

Hi Brian... you may be the man to ask....... if I build a plane with a 47" wingspan ...around 4 to 5 lb weight.... what width would the wing chord need to be ..a straight wing that is.? Ideal fuselage length would be handy too.. no pressure ..I realise it may be not be a simple equation.....just looking at your diagram above I am confused...

[Brian Clarey]

Hi ken,....It is difficult to advise you on actual numbers, because not knowing your intended use of the model it poses too many variables. What you are talking about is called Aspect Ratio!! In a power model this generally between 7 and 15 to 1. In your case ,at the lower ratio ie; 47 divided by 7 is around 7 inches. Wing thickness should be from 8 to i2% of the chord. Nose moment   distance from wing leading edge to nose 1.75 chords....Tail moment is distance from the trailing edge of the wing to the leading edge of the stabilizer  ie;is 2.5 to 3.5 chords.  47  inch span  by 7 inch chord is 329 sq inch is 2.41 sq feet.multiplied by flying weight is wing loading...... around 12 to 16 ozs/sq foot. Hope this helps.

Brian  C

[KENNYGLIDE]

Thanks Brian...those ratios will certainly will help break it down to some figures i can work with... hope you are both keeping well....Cheers Ken

[Brian Clarey]

After writing down the model spec`s, then draw up the model fuselage full size. This allows the placement of the hardware to fit into the design... making sure [width] access is there for removal/model balancing. The shape of the fuse is your choice that is aesthetically pleasing.....It`s there to locate the wing and tail group position, motor mount ,under carriage, struts ,etc. Initial balance, while not being totally accurate is to take a board the length of the fuse and mark the location of the bulkheads ie; motor mount,fire wall, at the wing leading edge and at the wing trailing edge.and any other desired along the way. Mark the CoG behind the fire wall at about 30% of the wing chord. Place all components including tail group at the desired positions. Check balance under the COG....Adjustments can be carried out on completion as required Dawn and I are both well, Thank you asking.

Brian C

[KENNYGLIDE]

Thanks for that Brian...makes a lot of sense......looking at the Corrowot plan for the corflute fuselage.....will probably have to scale it...will make a dummy first see what it looks like.

[Brian Clarey]

Hi Ken,....The Corrowot reminds me of the Das Ugly Stick. This model has been built in many forms,it has been very popular over time. Pls. see Das Ugly Foamie stick. While it shows it built in foam, I consider it could be built in corflute without too much trouble. The site shows step by step construction. It might float your boat !!
Brian c

[Brian Clarey]

Structures in brief.....We had to come to this, so I will try to keep it from being a cure for insomnia. Basically, the forces on a structure are....Tension. compression and torsion twist. The perfect structure is a cube. The sides (Diaphragms) makes for a perfect structure due to all sides being structural and therefore bracing one another. As an illustration of this, if you take a shoe box , minus the lid it will be seen that the box is quite flimsy, in all three forces, particularly in torsion!! However, If the lid is fitted and secured all around, it becomes a complete structure. Now imagine that box being the cockpit of an aircraft ....attach the power unit at one end, the tail group at the other end,the wing on top and the undercarriage underneath. All loads are fed into the box. All very good till you put doors and windows into box. In a model with the wing removable, that of course allows access inside. With the wing refitted and adequately secured once again, the structure is complete. With an open ,structure, (stick) all open areas must be diagonally braced or sheeted.


Brian C

[Brian Clarey]

Wing ...The heart of any wing is the main spar. Therefore, particular attention should be given to it, Shear webs ,with the grain running vertically to the spars is in order...The grain of the webs, running parallel to the spars can split with wing flex. On more than the odd occasion, I have seen where a kit manufacturer has made this simple error.....Shear webs, when cut accurately can be used as spacers when constructing a built up wing. Emanating from the wing centre ,they can go out towards the wing tips as far as required without adding much weight. Sheeting from the top spar to the leading edge and the same for the bottom spar, forms a '' D " box, adding strength.
Because fabric covered wings sag between ribs, your carefully selected wing profile is ever changing along it`s length. Full wing sheeting eliminates this problem and makes for stronger structure in heavier weather conditions. Some modellers don`t understand the reason for wing Dihedral and Poly- hedral. When the model rolls the upper panel reduces lift, because projected wing area is reduced compared to the lower panel which increases projected wing are..., Creating a righting moment.

Brian C

[Brian Clarey]

Glow motors versus Electric Flight......Traditionally, internal combustion motors ie glow, spark ignition and diesel motors, were the choice of enthusiasts. Each has it`s own drawbacks....noise has been a real issue at some flying sites, particularly sparkies. They have been responsible for the loss of more than one airfield, in noise sensitive locations. Fortunately our club has no problem there. Fuel residue on the model can be a nuisance, as ever increasing cost of fuel , glow plug availability and associated hardware etc, that is required. The proceeding is part reason why the current generation of Electric Flight has gained in popularity.
With the exception of sound, the latter ticks most boxes ....with the added of benefit of restarting if required. The original concept of model aircraft was to copy the birds and to be able to stay aloft for extended periods of time. Gliders do not have to be be slow in flight, in fact some competition models can be flown at over 300 klm`s /hr. Yes , they are purpose built using advanced techniques and exotic materials. Results for research and experimentation!!

Brian C.