The Theory and Practice of Model Aeroplaning

by V. E. Johnson

							Relative
				Ultimate		Modulus of	Value.
		Weight	Strength per	Breaking	Relative	Elasticity	Bending
Material	Specific	per	Sq. In.	Load (Lb.)	Resilience	in Millions	Strength
	Gravity	Cub. Ft.	in Lb.	Span	in Bending	of Lb. per	compared
		in Lb.		1' × 1"		Sq. In. for	with
				× 1"		Bending	Weight
Ash	·79	43-52	14,000-17,000	622	4·69	1·55	13·0
Bamboo		25[A]	6300[A]		3·07	3·20
Beech	·69	43	10,000-12,000	850		1·65	19·8
Birch	·71	45	15,000	550		3·28	12·2
Box	1·28	80	20,000-23,000	815			10·2
Cork	·24	15
Fir (Norway
Spruce)	·51	32	9,000-11,000	450	3·01	1·70	14·0
American
Hickory		49	11,000	800	3·47	2·40	16·3
Honduras
Mahogany	·56	35	20,000	750	3·40	1·60	21·4
Maple	·68	44	10,600	750			17·0
American White
Pine	·42	25	11,800	450	2·37	1·39	18·0
Lombardy Poplar		24	7,000	550	2·89	0·77	22·9
American Yellow
Poplar		44	10,000		3·63	1·40
Satinwood	·96	60		1,033			17·2
Spruce	·50	31	12,400	450			14·5
Tubular Ash,t =1/8 d		47			3·50	1·55

t = thickness: d = diameter.
[A]Given elsewhere as 55 and 22,500 (t = 1/3 d), evidently regarded as solid.

§ 14.—Formula connecting the Weight Lifted in Pounds per Square Foot and the Velocity.—The empirical formula

W = (V²C)/g

Where W = weight lifted in lb. per sq. ft.
V = velocity in ft. per sec.
C = a constant = 0·025.
g = 32·2, or 32 approx.

may be used for a thoroughly efficient model. This gives (approximately)

1 lb.	per sq. ft.	lift at	25	miles an hour.
21 oz.	"	"	30	"
6 oz.	"	"	15	"
4 oz.	"	"	12	"
2·7 oz.	"	"	10	"

Remember the results work out in feet per second. To convert (approximately) into miles per hour multiply by 2/3.

§ 15. Formula connecting Models of Similar Design, but Different Weights.