Other rules that I use are size of Ailerons, Rudder, Elevator
Lets say that D is Engine size like an OS 40 is .40 of a cubic inch
Lets say that W is aircraft weight like 5 lbs.
an example? a .40 engine would be happy pushing around a 4.8 lb.
airplane or .40X12=4.8
or example, a 6 lb. airplane would like a .50 size engine or 6/12=.50.
What can I tell you, It works for me !
Other rules that I use are size of Ailerons, Rudder, Elevator
Ailerons ------------------ 10% of wing area.
Rudder -------------------- 25% of Stab. area.
Elevator ------------------ 25% of Stab. area.
CG ------------------------ 25 to 30% of wing chord
.10 ------------------------------ 200-250
.25 ------------------------------ 400-500
.40 ------------------------------ 500-700
.60 ------------------------------ 600-850
Gas -------------------------- 1000 - up
( CANARD Center of Gravity ) Thought I would pass on some information on the CG of Canard type Aircraft. This is what a viewer had to say. -- This is written in general terms:
1. Both canard (forward wing) and wing should be of high aspect ratio. Better than seven. The canard should have the higher ratio than the wing.
2. The airfoil section of the canard should stall before the wing.
3. The area of the canard should be 20% to 40 % of the wing.
4. The angle of incidence of the canard should be 2 to 6 greater than the wing. In some cases even greater.
5. Keep the distance between the canard and the wing as long as possible.
6. The balance or center of gravity should be just ahead of the wing. In general if the area of the canard is 30% of the wing area. The center of gravity should fall 30% of the distance ahead of the center of lift of the wing. 100% would be the distance between the centers of lift of both lifting surfaces. Measurement is taken from the center of lift of the wing forward.
7. The center of lateral area of the aircraft is back of the center of gravity. Extent the fuselage back of the wing so that the vertical stabilizer can be effective.
8. In the case of swept back wings the centers of lift will be further back than a straight platform wing. The centers of lift can de determine graphically. The Gentle Lady is a good subject for the conversion into a Canard. However, a new canard has to be built. Hope this answers your questions. The same for powered aircraft.
These design notes are from R/C Model Builder December 1980 page 18 written and contributed by Col Bob Thacker. These are the details on the design of the OMAC-1 a 63" canard model of a proposed full size aircraft.
The C.G. is very hard to discuss because we have no common reference points. Let's establish them right now. The first thing you are going to have to do on any canard is figure out where the centre of lift is for both wings. The simplest and easiest way of doing this is to take the plan form right off the plan in the magazine. Stick this onto card and cut out. Now you are going to balance that half of the wing in two 90 degree planes, so balance in one plane, mark a line on it, turn the wing 90 degrees balance and mark another line on it. Where they intersect, draw a straight line along the airflow (chord) of the wing from front to back. The line you have drawn on the wing (and we do not care how much sweep or whether it is a double delta or whatever plan form) is going to be your Mean Chord.
Now 25% back from the leading edge of that chord (mean chord) mark and draw a line at right angles so it intersects the centre line of the fuselage and mark, this is the centre of lift on that wing. Repeat the procedure for the fore plane (canard wing) Now you have two lifting points, one forward and one aft. Now you are going to figure out where to put the C.G. First establish the area of the main wing and the canard wing. Let us assume that the areas work out as 20% for the canard and 80% for the main wing, this will give us some numbers to work with. Now measure 20% back from the forward Centre of lift or 80% forward of the aft Centre of lift (that is 20% or 80% of the distance between the two Centres of lift. This establishes the mean lifting point of the entire aircraft.
On conventional aircraft, we always have the C.G. forward of the Mean lifting point, 10% of the distance between the two Centres of lift forward of the mean lifting point will give you a starting point for your C.G. IMPORTANT. When you are calculating the wing area do not forget it is the lifting area you are after, so the part of the wing either on the bottom of or buried in the fuselage will be of no interest because it is part of the fuselage now and contributes no lift and therefore should not be a part of your calculations of the wing area." CENTRE OF LATERAL AREA.
How this fits into the picture I am not sure, Bob Thacker in his article has this to say about it. "Now we are not exactly sure why we have a Dutch roll, but there is one sure way to correct this, start adding more lateral area aft of the C.G. Our thanks to Sitting Bull who said "if your arrow flies poorly, just add bigger tail feathers". What are we talking about when we talk about this centre of lateral area ? If it is so important how do you figure it out so that you stay out of trouble ? Back to the trace and card as you did for the wing and canard wing, trace around the side view or your aircraft and cut out (if you have two rudders cut out another rudder and glue it right over the first rudder) Balance the fuselage (you have cut from card) two ways and draw lines through where these two balance points meet. The is your CENTRE OF LATERAL AREA.
The further aft on a canard that you can get your lateral area, the more stability you are going to have. It must be aft of the C.G. and very close to the aircraft's CENTRE OF LIFT. To get rid of Dutch roll we increased the lateral area aft of the C.G. and lowered the centre of lateral area by going under the wing with a large sub-rudder". Please credit RC Model Builder and Col Bob Thacker for the above information. I found the following info on the net but was unable to locate a photograph so the model was developed into a full sized aircraft.
OMAC 1977: OMAC Inc ("Old Man's Aircraft Company"; fdr: Carl Parise and Larry Heuberger), Reno NV. 1985: Albany GA. Laser 300 1988 = 7pChwM rg; 750hp P&W Canada PT6A-135A [N301L]; span: 41'6" length: 29'7" load: 3250# v: 291/230/71; ff: 7/29/88. Production version of OMAC 1. OMAC I 1981 = 6-8pChwM rg canard. Prototype 1: 700hp Avco Lycoming LTP 101-700A-1 pusher; ff: Dec 11, 1981. Prototype 2 [N81PH]: 700hp Garett TPE331-9 pusher; span: 35'0" length: 30'0" load: 2500# v: 299/250/63 range: 2950; ff: 2/19/83.
A special Thanks to Michael Walsh
At 2" spacing there would be 10 ribs on each side. The tip could be 4" for argument sake giving you a different size ribe each 2" span along the wing. make a hard rib pattern for the center and a hard rib for the tip with alignment holes for some music wire to keep the bottom of the ribs flat to the bottom of the wing. Insert ten pieces of material to shape the ribs from ( foam , balsa , bass etc.) poke the alignment wires through the holes and straight line sand from the tip rib to the center rib and it will produce a perfect tapered rib pattern at that spacing,
Next put ten more rib pieces and put the tip pattern on the other side and produce the opposite wing. Good luck and happy flying.