FI 1 6 F 8 7 F 7 8 F 5 9 F 5 H e a r t In 11 R e j e c t 10 S i n c e AS 1490 was i s s u e d in 1973, a new a s s e s s m e n t o f t h e m e c h an ic a l
p r o p e r t i e s o f c l e a r , s e a s o n e d r a d i a t a p i n e has been c a r r i e d o u t by CSIRO,
(D itc h b u m e 3 K lo o t and Rixmball3 1975)
T h i s a s s e s s m e n t i n d i c a t e d t h a t t h e s p e c i e s s h o u l d be a l l o c a t e d t o s t r e n g t h group SD6 n o t SD7, as p r e v i o u s l y s p e c i f i e d in t h e Timber E n g i n e e r i n g Code(S ta n d a rd s A s s o c ia tio n o f
A u s t r a l i a 3 1975a).
As a r e s u l t t h e s t r e s s g r a d e s o f t h e v i s u a l g r a d e s o f r a d i a t a p i n e which d i d n o t c o n t a i n corewood wer e i n c r e a s e d by one s t e p , i . e . F5 s h o u l d become F7 e t c . T hi s i n c r e a s e i s n o t a p p l i c a b l e t o F5 h e a r t - i n s t u d g r a d e (F5Hi) s i n c e i t s s t r e s s r a t i n g i s n o t ba s ed on c l e a r wood p r o p e r t i e s b u t on t h e r e s u l t s o f t e s t i n g f u l l s i z e s c a n t l i n g s . Ther ange o f v i s u a l g r a d e s however was r educe d t o t h r e e ; F8, F7 and F5, e x c l u d i n g t h e h e a r t - i n g r a d e s . The change in g r a d i n g r u l e s had l i t t l e e f f e c t on t h e r e s u l t s o f t h i s work b e c a u s e t h e d i f f e r e n c e in d e f e c t s i z e
a l l o w a n c e s between g r ade s i s s m a l l . fn p r a c t i c e t h e a p p a r e n t b e n e f i t
o f t h e v a r i o u s v i s u a l gr ades i s n o t u s u a l l y r e a l i z e d by t h e t i m b e r p r o d u c e r because o f t h e d i f f i c u l t y i n d i s c r i m i n a t i n g between t h e h i g h e r g r ad e s
e c o n o m i c a l l y . C o n s e q u e n t l y much o f t h e v i s u a l l y gr aded s c a n t l i n g i n A u s t r a l i a i s gr aded t o a maximum o f F5.
The boa rd s were v i s u a l l y graded t o ASO72- I969 ( S . A . A . , 1 9 6 9 ) . The gr a de s and t h e codes used a r e g i v e n i n T a b l e 3 - 7 . T h i s s t a n d a r d was m e t r i c a t e d i n 1973 and i s s u e d as AS 1489“ 1973.
TABLE 3 . 7
Code Numbers a s s i g n e d t o t h e boar d AS072
gnadz
Cl e ar J o i n e r y S e l e c t S t a n d a r d R e j e c t g r ade sGrading Co du
1 2 34
53 .9 Ttmbzn. a amp t i n g deA&ujLcXivz £&&£&.
The C o m p u t e rm a ti c machi ne o f t h e F o r e s t r y Commi ssion o f N.S.W. and a d e v i c e known as a Mnemotype ( G r a n t, 1977) were used t o p r o v i d e d e f l e c t i o n r e a d i n g s o f some 400 p i e c e s . These l e n g t h s r e p r e s e n t e d t he m a j o r i t y o f t h e 35 mm x 150 mm and 35 mm x 200 mm s i z e s . The Mnemotype, when c o n n ec t ed t o t h e C o m p u t e r m a t i c , r e c o r d s and then p r i n t s each d e f l e c t i o n
v a l u e measured. The u n i t was a l s o used t o p r o v i d e a c c u r a t e i n d i c a t i o n o f each p i e c e ' s l o w e s t s t i f f n e s s zone. f t was i n t e n d e d t h a t each p i e c e wo u ld be t e s t e d i n a s t a t i c mac h ine , a t t h e p o i n t o f l o w e s t s t i f f n e s s , i n
b e n di ng on t h e w i d e and n a r r o w f a c e s and t hen t e s t e d t o d e s t r u c t i o n on t he n a r r o w f a c e . T h i s i n f o r m a t i o n was t o be used t o p r o v i d e s t r e n g t h d a t a f o r r a d i a t a p i n e o f 35 mm x 150 mm and 35 mm x 200 mm s e c t i o n s i z e s s i n c e
3 2 .
l i t t l e i s known o f t h e s t i f f n e s s - s t r e n g t h p r o p e r t f e s o f r a d i a t a p i n e in t h e s e s i z e s . A p p r o x i ma t e l y 100 s a mp l e s r andoml y s e l e c t e d from t h e 35 mm x 100 mm p i e c e s wer e a l s o t e s t e d ( t h e s e s a mpl es wer e t a k e n by Mr Buick d u r i n g t h e o r i g i n a l g r a d i n g a t t h e Depar t ment o f F o r e s t r y ) .