TECHNICAL NOTE S
F"oRE5'r' PRODUCTS LA B4RATOF~ Y
U, S . F'Uf2EST SEF2VtC E
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~l14DiSON, WiSCOh1SI N
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~'i+'i+~C ~' ~ F WRA.P~.'~IZ~ U T3 THE, S r.1REi~~T~i U .~' ASR :r.'~N~ S '.Lt~I~T S
1'he pr ac t .ice o r' wr ~~pp ing ~,~ . xpl 3ne struts o r win g
~be,an~s with canvas deve~ .oped under :the supposition tha t
such wx app i.ng i nc r e s,s e d the strength o f the m e ~b er s a t
cr i tica~. points , pr eve; nt ed sudden fa ilux e s , and k~:pt ou t
~noisturt . Wrapping has been advocated especi~,l2y fo~ c
cross-gxained rn~,teria~. in oxder to make ~,vailab~.e for ~,ix ;
plane construction stock which wou~.d ~o th ~:rw ice be xe j .eete d
~~tensive tests have be~;n made 3t the ~ ores t
fro duc is Z.abo xatory for the United St .ate~s _~,ir 'Sexvice t o
determine the re~infoxc ing value of such . ~~vr app ing * Thes e
tests were l~nr~,de u~aon cross-gx~,ined struts of Site, spxuc e
and Toughs fir p~,rtl.y or entirely eoverec~ with ~3akelize d
canvas ox the standard cotton tape , and upon some of th e
carne stxuts with . t3~e~ wrapp ing rernoved .
.~~
follows ;
'l~he c onclus ions xeached fror~ the tests were a s
.
The addition of ;BakeliZed cal~ve,s to cross--gx .3ine d
struts increases the ~.oad eomev~hat but decre-~sed the loa d
per unit weigb.t ; it a3.so increases the def~.ection ~,nd wor k
to f~ .n~,3. fail.ure~ and hence the shock-res~.sting capacity o f
the stxuts .
wrappi~Zg cross-~gx~ined struts wit~i cotton tap e
~caording to stand.,3~rd mmethods has rlo appxec~.able effect o n
their st~cength .
It is doubtful if a3~y othex methods o f
wr ~,p~,ing such as cording would increase the st~cength pxopexties vexy gr eat~.y .
' nex e is 31so the pr o babi~. ity th 3 t
any wrapping or cover ire ; will be loosened by we3the x
changes .
I t is be3, ieved th~.t e anv~,s , tape , ox cord a ovex .~ ng i s o f l e s s value than the s ani e volume o f • pro o d, :~nd
since such .~ covering is ~. ike~.y to be hs avier thin woo d
it is o f sti~.l ~ .e ss va~,ue when camp~.red ~vith tha s~r:le
weight of wflod .