4 - Memorial University of Newfoundland DAI

where (2) is the general gmmdric or model sealale; it is different from
(k), the member(a) wall thickness scale. Since (L) = (2)- then
C 4
equation (4.34) ean be reduced to the following expreosion:
To sntinly the above expreaaion, it will be necwa:y for the material of
the model to hive a density p,,;, ao:
p. .,* D,d, - -P,,p$l
(4.36)
whcn: p;,- and p., are the material densities of the model aud prolotype.
respetivciy-thcother variabioa have been previously defined. Observr that
thc products Dm& and D,d, are proportional to the cross sectional are- of
tlnc strtlctural componmt(a) of the model and prototype, respectively. Tho
shovo cxpmsion result8 because the submerged weight to tho hydrodynamic
force raLioe should be bold constant (591. Rearranging equation (4.36) results
in thc following expression:
Sinn models conslrueted of a material having a low modulus delarticity
(c.g., plwtie) onen have a lower density than p.,-', then it will be necessary
lo add flexibility and conwniently distributeextra masses b compensate br
llte dillcrenee'o; that is:
'. ~c.lF,.h..,.o; p:.D.d- or PPPD,~,~
(Fw.&~.~,c a DL or D:)
'' ..c.g .for the male1 br.ng~nr-tlgswd m thi.t,cnu.r, p.,: ~r 2OBlr lo-'kg/rd,
wh#lch- for ADS pl.alir 4s I I07 x 10.' Ig,