EST I HE

I

0 s lOSS OF

ERSIO ITS

A. V. V, SATYANARAYANA* AND G. K. KURIYAN

Central Institute of Fisheries Technology, Cochin-5

INTRODUCTION

A wooden fishing float under immer­sion in water for long periods is liable to absorb water, the quantity of water absor­bed possibly being dependent upon the physical factors like the specific gravity and the inherent property of the material, the time of soaki!'g and the pressure acting on it. Consequently a wooden float is likely to become heavy and loss its original buoyancy· However, when the flo­at is removed from water and dried, the lost buoyancy is regained on complete dry­ing. It should be evident that, in both the amount of absorption of water and the rate of drying, the different wooden materi­als would exhibit different properties. These two characteristics severally and conjointly contribute to the effectiveness of the wooden float and the resultant effici­ency of the gear to which it is attached. The present paper is an attempt to eluc­idate these two important characteristics of some of the chief wooden floating materials used on the West Cost of India.

The authors thank Shri K. · Krishna Rao, Assistant Statistician for his kind help in fitting the regression lines.

MATERIAL AND METHODS

The materials included m the study

consist of five different woods. T2.b!e I presents the names of materials, their physi-cal dimensions, the states where used and the gear to which they are commonly atta­ched. The samples analysed represent app­roximately the actual size of floats in commercial use.

Experimental procedure

After recording the initial weight and buoyancy, the samples were completely suspended in water for a total period of 10 days (240 hours). The buoyancy was measured at periodic intervals as indicated b:low:

1st day at an interval of 6 h(mrs 2nd & 3rd days

" 8 hours 4th day

" 12 hours 5th to 1Oth day

" 24 hours

The original buoyancy is recorded in Table-I.

The method adopted for measuring the buoyancy and the equipment used are similar to those described elsewhere (Satya­narayana, 1960). Samples after exposure in water were removed and the quantity of absorbed water estimated. The wet samples were grouped ir.to sections and one section was dried in shade and the other in sun. In both cases the c.~:::.unt of water evaporated was recorded at regular intervals.

* Present AddrE>ss: C. I F. T. Sub-station, Kakinada-2.

VoL IX No 2 1972 139

"Tj (;;) :::r:1 tTl :;>;l ~

_, tTl () :::r:1 z 0 r-< 0 Cl >-<

1ABLE I: SHOWING THE SPECIFICATIONS Of THE FLOATS STUDIED

Local name

1

'Satwin'

~--~=~~ -~--~~

States from Scientific Name Original Buoyancy where samples

in gms, were taken

2 3 4

Alstonta scho!aris 106.31 Maharashtra

·'Guggaladupa' Bombux malabaricum 56.70 Mysore

70.88

'Hongarn' 35.43 ~.1ysore

35.43

177.18

574.37

'Pangara' ~do~ 517.37 Maharashtra

545.72

205.53

Name of fishing gear

5

Code No. and General shape of float

6

Drift nets 5 B; Long, triangular (Wahur' and in cross section and Surmai Jal') tapering at one end.

Gill and 3 B; Flat smooth at drift nets. ends to from the sha~

(Veedinabala') pe of a spindle.

Smallshore seines (Kairampini ')

4 B; ~do~

14 D; Cylindrical.

Dimensions in ems.

7

L=37: B=2.2; T,- 1.7

L=29.5; B=4.5 to 5; T~l.O

Lc-29.0; B=2.5 to 4.5; T=l.O

9.0; D=4.0

Big shore sei~ 13 D; Flat with rou~ L=14.0; 3.0 to 5.0; nes ('Rampni') nd and truncated edges T= 1.0

Shore Seines (Rampon)

Drift nets ('Wahri Jal')

12 D; ~do~ L~24.0; B=5.5 to 8.5; T=2.5

11 D; ~do~ L=34.5; B'"--7.5 to 12.0· '

15 D; Flat and rectangular 16 D; -do~

17 D; Long and tri­angular in cross section.

T=2.5

L=26.0; B 10.3; T=3.0 L=26.0; B=lO.O; T=3.1 L=36.0; B=2.0 to 4.0; T= 1.5 to 3.2

Ctl Cl ~ 0 :::

'" D - -t ::: 0 Q_,\;: ~ 0 "" ;::: (") (;)

s 0 ,.. ~ ..... -;· ~ 13 ~ ~ ~ (I) ~­-<.!;: ::: e ... ,.., ;::: .. ;;; "" ,_, "' ;::: ,.,. <:l 0 ~ ;::: ~ .... ;·~

s§' p ,.., - "' ~

"" 0 ::: ::; r-> - \::1 P-o '"'- 0 ;:o,l:l... {'Q ~ ::: /.5 'JJ p -- 0 ~ p ..... 0 ;;· -<::;:,

~~ 0

id;;; ~ ..., Q., .... ~ p ; f;"

"1::)' l

;::~ g ~ Cl"("->

<$:! 0

"' v"' ... 0 ~ .,..,_ ;;;· tO

<C ;::: 0

<:::! 0 ::: {)

r.:;z.

8at~Janarayana and 'Kuriyan: laoestigations on Wooden Floating Materials - 'Hie Loss of 'Buoyancy: under continuous Immersion in 1Dater and tf!e 'Rate of its 'Redemption 6y Drying

RESULTS AND DISCUSSION

The results obyained are indicated in Figures 1 & 2.

~ 100

;go ~ g 80

! 70 0

~ 60

0 50

j 40 0 * 30

~ 20

rt.,o l

GMELINA ARBOREA

99·2c.e. 28F

·····0.······•·······• 311·9 c.c.27F

OL--2~0~4~0-6,0--6~0~.~10TO~I~r-·,~r0-1,60~.~T0--2T00--2~20~240 eorlod of_ltnmare~ri' in tin.

Fig:l

Fig. 1: Relation between the percentage loss of buoyancy of different fishing floats made of different materials and period of immersion in water.

g:;o ~ 20

:. 10

100

~ 0 90

~SO·

j'70 i 60

ERYTHRINA INDICA

BOMSAX MALABARICUM

-----

120· 5 c.c:. 48 ...-~_.99·2 e.c, 38

,----------

050+-~f---~-----------------------------

VOL

0 ~~20~40~~ro~oo~~~oo~~~~~~40~~~~~~~'o~22~0~2~4o Pe.-rlod of lm~ in hna.

IX No 2 1972

Fig: I

0

c 30 f ~ 20

~ 10

SAMAOERA INDICA

~--~255·2c.c. 34!

-~-------------------· 339·5c.c. 35 l

~-

OL-~20~4~o~so~e~O~IO~O~I2~0~1~40~JST-O~Ie~o~2'oo~~-o~240 Porlod oflmmerelon In hrs:,

oiOO

!Go !$0 i! 70 0

iso

Fig: I

~~t---~~---------------------------­.2 '040 Q

~30 u 20

:r !0

100

90

, 80 .': :: 70 0 Q.

" > 60 .. ~ .. 50 ., lt -40 0

0

"' 30 E c: .. .., 20 :0 Q.

10

0

F'lg:l

SOMBAX MALABARiCUM

Dried under Shade.

(/~'" Dried unclar Sun·

38

1

20 40 60 80 100 0· Period of d ryi~Q In hrs.

/ 48 /

Flg:2

Fig. 2: % amount of water evaporated in the process of drying under shade and sun of different floats made of different material with the time of exposure.

Sa tyan arayana and 'Kuriyan: Investigations on Wooden Floating Materials~ 'Ine Loss 0 f 'Buoyancy under continuous Immersion in Water and tfle 'Rate of its 'Redemption 15y Drying

ALSTONIA SCHOLARU!t

Dried under Dri0CII under Shade Sun

100

59 90

'0 ao ! 0 ....

?0 0 Q; 0 :> ., .... !

50 0 ll: -0 40 (l)

"' E 30 c 0

" .... 20 0 Cl..

10

0 20 40 20 40

Perlo<! a f drying In hr:r. Fig:2

GMELINA ARBOREA

Dr}ed undor Sun 23F 25F 28F 27F

f {26F 24F .->- •

11r v / l(i /'_./ d ' iii t' 11/ / l'j! ·I,

10

OL-~~~~~-+~~~~~ 10 20 30 40 50 0 '0 20 3-0 40 50

Porlod of drying !n Mrs.

The buoyancy is either completely lost or mostly lost in almost all the samples within a period of ten days. Within the same material, small sized floats lost their buoyancy in a short period, while the rate of loss was slow in their bigger counterparts. During the process of dry­ing, the smaller floats dried completely in a day thus redeeming the lost buoyancy relatively fast.

142

1. loss of buoyancy in different materials and variations due to volume and shape within and different materials:-

The percentage loss of buoyancy after different periods of immersion for the samples are shown in Text. Fig. 1.

i) Loss of extra buoyancy with respect to different materials:-

Comparison of loss of buoyancy in different materials was drawn from the samples of floats having more or less same volume and shape.

If a float is considered to be of not much use, when its buoyancy has reduced by 50%; then among the smaller volumed floats (less than 100 c. c.) 50% loss is noticed in Gmelina arborea, Bombax ma­labaricum. and Erythrina indica within 16, 22 and 26 hours respectively (Fig. 1). In medium sized floats (volume between 100 to 200 c.c.), Gmelina arborea retaind 40% buoyancy upto 50 Hrs. as against 36 Hrs. in the case of Alstonia scholaris. In bigger sized floats (volume ranging from 200 to 300 c.c.), which are found in wide use 50% loss is recorded at 30 102, llO Hrs. in Samadera indica, Gme­lina arborea and Erythrina indica thereby indicating the effectiveness of Erythrina indica. Considering the above, even tho­ugh it can be said that as floating ma­terial, all these woods can be used with satisfaction, but floats made of Erythrina indica and Gmelina arborea retained their buoyancy for comparatively longer periods, followed closely by Alstonia scholaris. The remaining two floating materials (viz.) Bombax malabaricum and Samadera indica reduce their buoyancy within short periods.

ii) Jnj!w?nce of volume and shape:-

The reduction of buoyancy is found to be proportional to the volume of mat­erial contained in the float. Accordingly

. FISHERY TECHNOLOGY

,8.afyanarayana and 1{uriyal'l: 1noestigations em Wooden FlGating Materials- 1fie Loss of 13uoyanelJ

under continuous Immersion in Water and tile 'Rate oj its 'Redemption 6y Vryi~1!J.

SAMADERA INDICA

Drhu! und« Shodtt :Dde>d undeF Sun

IOQ ~/' 351 341 /.36f 34I ,

·"' 90 .,,ff!!>-.....,. ... w ... .,' ' ~ ,

Ol 00 tJf +- ' . E • I 0 70 ' Ill. 1:1 > 0! 60 b Q

i 50 .. 0 40 8, 0

30 ... c ell u .._ 20 "' CL

10

0 20 40 60 eo 100 120 140 160 0 20 40 60 80 100 120

Pet'lod of dr)'il'lel In hrs. Fio:2

ERVTHRINA INDICA

100

90

't:l so <I>

0 ::; 70 Q,

" ~ 60 ... ., 0 50 3::

6 40 .. 0

~ 30

"' 0.

~ 20 a..

Period of drying in hrs. Fig:2

'5maller volumed group experienced less buoyaucy loss· than the comparatively large volumed group. Further the time taken for buoyancy loss is shorter jn the

VoL IX No 2 1972

former group rather than in the latter group.

Among the floats made of ErJifh:rina indica, .a very interesting phenomena was

143

Satyanarayana and Kuriyan: lnoesiigaiions on 1Dooclen fluating Yfnterials- 'Ifle Loss o/ 13uoyancu 1mder continuous Immersion in Waler nHd tfie Tiede of its Redemption: f)y Drying .

observed in buoyancy reduction. The time taken to buoyancy reduction has shown inc­rease with the corresponding increase in size and volume of the float. Between the two shaped floats of more or l::ss same volume at 63.8 cc, the long, flat with round edged floats lost buoyancy much earlier than short and cylinderical ones. Among the two samples of the two groups having volumes about 260 cc and 775 c c, variations between the individu:1ls was not significant, except reduction was seen in accordance with volume, since the shape of samples in each group is same. The sample of float having 963 cc vol­ume 1ost its buoyancy comparatively ear­lier than the samples of 775 cc group, which may be due to its shape being lo­ng, wide and thin and had wider area of exposure.

the two samples of floats made with Omelina arborea, though the volume was more or Jess same, the loss of bu­oyancy was prominent in the float of tria­ngular shape (135 cc) than in the flat and rectangular floats (148 cc), indicating the inflnence of shape.

Floats made in triangular blocks from the above material are specially used for bo­ttom set and drift nets possibly due to that the shape aids it to withstand the relati · vciy larger pressures available at these de­pths. Further the material is dense with specific gravity varying from 0.474 to 0. 263 g-mjcc., which incidentally is the highest among all the floating materials used at pre­sent in India (Kuriyan and satyanarayana. 1961).

iii) Relation between foss of Buoyancy with time of ilnmersion~-

An attempt has been made to corr-1ate the loss of buoyancy of the above wooden float samples with the time of continuous immersion in water. The av­erage percentage loss of buoyancy per ea­ch hour was oht~1incd by dividing the

percentage loss of buoyancy between two successive observations with the time int­erval for the same two observations and is taken corresponding to the end of the time intervaL Regression lines for all the samples were fitted as shown in the text. Fig. 3 and the formulas holding the relations have been calculated usi!1g the least squ­are method and shown in Table H against the indtvidual samples.

Fig. 3, Regression lines for the loss of extra buoyancy with time of continuous Im­mersion in water.

FISHERY TECHNOLOGY

Satuanara!Jana and 1{uriyan: Investigations on Wooden Floating Materials- 'Uie Loss of 'Buouancy under continuous Immersion in Water and tile Rate of its 'Redemption 6y Vrving

4 SAMADERA INDICA

E .. 0

3

<

. 1:

2

0

~ 0

~ I

~

(Oocrooalno 11olumc ~11th dlftoront atlopu}

,. ..

' ' ' ' ' ' ' ' ' '

I 0 1·5 2 0 Tlll'lo l)f contlnuou• tmmor~>lon

BOMBAX MALABARJCUM

(Docrno•lntlliOiumo wlthdlrtoront ohOP•~)

' '

' . '

20

/0 ~~ 20 25

130

liD

T1mo or .conron1..10ut.> lmrnar ~!On

ERYTHRINA INDICA

{Oo~roo~!no volumo ..,Ill! difhoronf •hOP•u 1

20

Time. of contlnuoua lmmoralon

VoL IX No 2 1972

Erythrina indica:

The perusal of table as well as figure re­veal that Joss of buoyancy depends on volu­me as well as the shape of the float as the samples 13D & 14D, and 12D & 17D having same volume, exhibited different property mainly due to shape. Similarly within the same sh1.ped floats (i. e.) 11 D, ] 2 D and 13 D, the difference can be attributed to the volume contained in each; but within the same shape and volume (15 D & 16 D) the equation remains almost same.

Gmelina arborea: The Table clearly indi­cate that as the volume increases, the slope of the curve decreases, irrespective of the shape of the floating materiaL Thus the loss of Buoyancy vary with the shape, hold good in this material too.

Among the sample of Samadera indica and Bombax malabaricum, rhe regression lines indinte that the difference is mainly due to volume as the shape of samples are identicaL

2. Amount of water absorh._:d in different materials a.'1d its relation to shape and size of floats:-

The amount of water absorbed at satu­rated point in fresh water for different materials was indicated in Table Ill. The calculated quantity of water absorbed per 1000 cc. of material in each of the sam­ples was also shown for comparative purposes.

The amount of water absorbed depend on the density and size of the float and the area c·f the absorbing surface.

From the perusal of Table HI, it can be clearly seen that absorption of water is found to be significant in Bombax ma!a­baricwn. followed by Erythrina indica. Though some floats of Gmelina arbon?a exhibit more or less same tendency as

]45

-.J:::. 0\

'Tj -(/) ::0 m :;::; -< ..., m (j ::r:: z 0 r 0 CJ -<

TABLE II:

& Code No.

Erynth rina indica 13D 12 D ll D

14 D

15 D 16 D

17 D

Gmglina arborea 23 F

24 F

25 F 26 F

27 F

28 F

Samaeara indica 34 I 35 I

Bombax malabaricum 3 B 4B

Alstonia scholaris 5 B

REGRESSION EQUATIONS FOR

Volume (c. c.)

63.8 258.1 9GJ.8

63.8

758.3 80 ).9

2G2.2

63.8

135.7

148.8 177.2

311.9

99.2

255.2 339.5

99.2 120.5

163.0

OF BUOYANCY WITH TIMES OF IMMERSION IN WATER

Shape

flat with round and truncated edges

" " , ,

Cylindrical

flat and rectangular

" ,

long, triangular in cross section

long and cylinderical

triangular

rectangular and flat

" triangular

"

Regression equation

Y = 5.2229 - 2.4741 X Y = 2.0593 - 0.8989 X Y = 3.4518 - 1.6354 X

Y = 1.0255 - 0.2275 X

Y = 2.1177- 0.9593 X Y = 2.1418 - 0.9644 X

Y 2.0949 - 1.3553 X

Y = 6.0365 - 2.9148 X

Y = 4.4201 - 2.0498 X

Y = 3.5991 - 1.6574 X Y = 2.3108 - 0.9906 X

Y = 2.1284 - 0.9665 X -----~--- --------

oblong, flat on one side & round on the other

long and cylindrical

" "

spindle shape

" "

long and triangular

y = 5.1209 - 2.3994 X

Y = 2.8709 - 1.3189 X Y = 4.0734 - 1.8815 X

Y = 44.540 - 2.0793 X Y = 3.1573 - 1.3617 X

Y = 3.0653 - 1.4082 X

Note: Y = Average % of loss of extra buoyancy per hour. X = log. of hours (Time of continuous immersion).

(J)

~ <.:= c c

,., -t ~ !:l .... <;::::

s:l.!:l "' ;:< -t 0 (")

0 p ;s = :=:~

~ ~ 0 ;:: ;:: -t V> ....

<;:::: -o :::: ;:< ~ .. "' ,_, ~. ~ 0 "' ;s ;. ~· <,a ~ E.. 5g c Cll

;;;-0 -t ;;s

§ 5 s:l.o

0 .... s:l. ~,

"' ;:: j>j.,

c -~ 0

"' ;;_ 0 ;· -<,a

~~ c

~­"' ~ s:l. .... "' c ~ ~

'1:l' • =:H 0 ~ ;:: "' C'>t­

c.: 0 V>

t:j"' .. 0 <.: """" ::s· tU

<,a ;:::

0 <.: ;::, ;:;; (")

~

Satyanarayana and 'Kuriyan: 1nvestiyations on Wooden Floating Materials- 'Ifw ·Lass of 'Buoynncy under continuous Immersion in Water and tile 'Rate of its 'Redemption 15y Vryi11g

Erythrina indica, the small rectangular and flat floats absorbed less water, which may be due to higher density of the sample. Bet­ween samples of Alstonia scholaris and Gme­lina arborea, having more or less same volu­mes the water absorptiun is high in Alsto­nia scholaris and it is nearly 10% more. Between Samadera indica and Erythrina indica having same volume, the former is better.

Considering that generally fishing gear­is not kept under fishing condition for more than two days, the amount of water ab­sorbed for nearly one and two days im­mersion in water respectively was worked out and the relation of water absorbed and the volnme of the floats is shown in fig. 4.

' \ \

\ \

ERYTHRINA INDICA

\ 64hte \

\ .,. .... ..-"Z6Piinl

\/"""------ // ----q

200 400 600 soo 1000 Volumo of float tn c;.c:.

Flg:4

Fig. 4: Showing the calculated amount of heat absorbed per 100 c. c. of material within 26 and 54 Hrs of water immersion in different volu­med floats in different materials.

It is evident from the figure. 4 that the more is the volume of the float, the less is the absorption of water. In Ery­thrina indica samples the absorption is alm­ost proportional to the volume of the float and the period of immersion. The devi­ations noticed may be due to the shape and density of the materials of the sam­ples.

VoL IX No 2 1912

BOMBAX MALABARICUM

I l I I

126hn

0 200 400 Volume of floats in c. c.

Fig: 4

GMELINA ARSOREA .. eoo E

i " c

~ " 500 ' .. ~

·"' .. "'~ "' " <IS-;: .. 400

g:~ .... "' 0 .<!::= g "' . 300 .. "o ~0 ~o

~= D 200 " 1 64hr< L

J! '1 ~• 26hrm.

" 3: .... -.. 100 0

§

E <( 0

200 400 600 1000 Voh.l!"no of floats k-1 c c.

3. Evaporation of absorbed water of floats on drying in sun and shade:-

The percentage amount of water ev­aporated in the process of drying in _both sun and shade at different intervals in different samples made of different mat-erials is represented in Text. Fig. 2. The

147

D;;J·c!J·anaraJJana and 'Kwriyan: I'nvest~gations on Wooden Floating Materiafs ~ 1'fte Loss of 'Buoyanew under continuous lmme1:sion in Water and tfle 'Raie of its 'Redemption f5y Drying

samples dried earlier En Sun than under shade, wh~ch is the gene:rel character of most of the woods with respect to their drying property.. On comparison, it is found that samples of Erythrina indica- dried very mu.ch earlier (by 25 to 30% time), than all others. The time of drying in Sun is nearly 10%, earlier than rn shade in an material except in Gnrelzna aroorea, w··here the range is between 5 to 10%.

Considering the equal Yol'umed floats of different materials, it is found that samples of Gmelina arborea, dried earlier" foHowed by Alstonia s.cholaris:.

Within the same material, floats hav­ing scome volume, but with different shapes. the rate of drying is found to be differenL This is ciear in Erythrihcf fndica in which the drying time of a sample of long and flat shape is different than the short and cylinderica! one. On the whore, the size9' shape and area of surface exposed,.. deter­mine the rate of drying.

Here too, the regression equations. were obtained between the percentage loss of water ion drying under shade and sun with_

times of drying and are giveri in Tabie­IV and regression lines drawn in Text Fig, 5. As previously stated, the percentage loss per hour was calculated for the succ­essive observations and taken correspond-1ngly to the time interval.

ERYTHRI~A INDICA

Or>cd a.md~u Sun

Fig. 5: Regression lines for the loss of water­in drying under snn with time of dry iLl g ..

ERYTHRii4A i;'JCICA

Oricd und<!lr Sll~

&·0 1·5 2·0 Tim&~ of dryl~

2·6

flg:5

FISHERY TECHNOLCGY'

B t='

~

z 0

tv

...... \.0 -....) N

.,., ~ \.0

TABLE IV: REGRESSION EQUATIONS FOR LOSS OF WATER IN DRYING UNDER SHADE AND SUN

Name of floating mate- Volume in rial with code No. c. c.

Erythrina indica 13 D 12 D 11 D 14 D 15 D 16 D 17 D

Gme!ina arborea 23 F

24 F

25 F

26 F

27 F 28 F

Samadara indica 34 I 35 ·I

Bombax malabaricum 3 B 4 B

63.8 258.1 963.8

63.8 758.3 800.9 262.2

63.8

135.7

147.8

177.2

311.9 99.2

255.2 339.2

99.2 120.5

Regression Equations

Under shade Under Sun

Y = 5.8880 - 2.9615 X; Y = 5.6327 - 2.7813 X Y = 3.2279 - 1.4185 X; Y = 3.5567 - 1.5993 X Y = 7.0735 - 3.6623 X; Y = 7.0292 - 3.4549 X Y = 3.2877 - 1.7629 X; Y = 2.8591 - 1.1698 X Y = 3.2877 - 1.4479 X; Y = 3.5484 - 1.5731 X Y = 7.1094- 3.7857 X; Y = 3.5196- 1.1625 X

Y = 11.8308 -- 7.1629 X;

Y = 4.2121 - 1.9498 X; Y = 7.1851 - 3.7593 X;

Y = 13.4338 - 8.4378 X; Y = 8.8708 - 4.8529 X;

,

Y = 9.6898 -- 5.6009 X

Y = 6.5287 - 3.3621 X Y = 7.2326 - 3.8473 X

Y = 6.8919 - 3.5497 X Y = 8.6996 - 4.8705 X

Remarks

dried within 15 & 10 hrs. exposure under shade and sun respectively.

Sample dried within 15 & 5 hrs. under shade and Sun. Sample dried within 15 & 10 hrs. under shade and Sun Sample dried within 10 hrs. under shade as well as sun. Sample dried withih I5 & 10 hrs. under shade & Sun.

Sample dried within 24 hrs. under both side and sun.

Alstonia sholaris 5 B 163.0 Y = 14.3141 - 9.1386 X *Sample dried within 24 hrs.

under shade. Note: Y = Average percentage of loss of water for each hour.

X = log. of hours. (drying time)

Cn c ....

<.!:: ~ :=:

;:: ~ :=: c P..t,:: (I) p ... :=: C) ~ 0 p a :=: ;· p._.

;:: :::,;; 0 ;::

~ ~. -c.:: ~ § :::: .. ;;; -:; ~ .... <::1 o ro :=: ~ ~·tO. ;:: p

6g: Q :=: - <n ro o ... :=:

§ s P..o

0 ..... p._. ;:::,(1) (I) ;::

::>;5'11 p --o 1\) 0

...... .... 0 :::l -\,C)

a:~ 0

::>;Jc;:-(1) .... p._. .... (I) 0 - -:: '-'> "0', -.... ,..:) g ;:::, ... (I)

""c­t.:: 0

<n

v"' ... 0 c.::-;:;· tO

\,!;) ...

0 <.!:: p :::l ()

<.!::

-VI 0

'Tj -fJ)

::I:

~ ;;;1 g z 0 t-' 0

~

TABLE HI: AMOUNT OF WATER ABSORBED AFTER 235 HRS. OF CONTINUOUS IMMERSION

Name of material of

the float

A!stonht scho!aris

Bombax ma Tabarfcum

Code No.,

Volume & shape of the float

5 B: 163.0 cc. Long triangular in cross section

3 B: 99.2 cc. Flat spindle shaped 4 B: 120.5 cc. , ,

Quantity of water absor­bed within 235 hrs.

in gms.

56.7

70.9 70.9

'--~"~~~--~ ----------------

Erythrina indica

Gme!ina arborea

Samadara indica

14 D: 63.8 cc. Round small cylinders 13 D: 63.8 cc. Thin flat with round edges 12 D: 258.1 cc. long and flat with round edges 11 D: 963.9 cc. Long and flat with round edges 17 D: 262.2 cc. Long triangular in cross section 15 D: 758.3 cc. Flat rectangular 16 D: 800.9 cc. Flat rectangular.

· 23 F: 63.8 cc. Long cylinderical

24 F: 135.7 cc. Triangular block

28 F: 99.2 cc. Oblong flat on one side and round on other

27 F: 311.9 cc. Semitriangular block

25 F: 148.8 cc. Semirectangular block (Flat)

26 F: 177.2 cc. Semirectangular block (Flat)

34 I: 255.2 cc. Long cylinderical

35 I: 339.5 cc. Long cylinderical.

57.3 35.4

134.6 431.3 134.7 361.4 311.9

35.4

56.9

42.5

60.2

42.5

35.4

106.3

155.9

Calculated amount of water absorbed for 1000 c c of material in

gms. at saturated point.

348.0

715.5

588.4

898.4 555.5

521.6 447.5

513.5 476.6

389.3

555.6

419.2

428.5

193.1

285.7

200.0

416.6

459.2

C/J D

~ 0 ;:s p ::: ...

;s D 0..<:;: (I) 0 .., ;:s

n o 0 >::>

~;:: ;· R..

::! ~ g ;:!

"' ... ..,. <.:: -o ;;: :s

= .. (I) -~ ::: .... "' 0 (;)

= ; ..... "" ::: p

st s:l ~ ..,. (;) 0 ... ;:s

p c-" ~ c::3 o..c

0 -o.. ~(\) (U ;:l

::<:J'TJ 0 -- 0 "' p -0 ;· """<O

::::~ "' p ::;:)~ !tl ... 0.. ... cu D ~ l/)

~· ..... t--=l 0 ~ ;:l (1)

oor­<.:::: 0 (J> tl(J> ... Q

<C .......

~· tO tO ;:::

0 ~ p ;s

" ·c:

< 0 \' -:X

~ N

-\0 --...) N

-Vl -

1 2 3 4

'Shiveni' Gmelina arborea 35.43 Mysore

93.12

'Shivani' ~do- 56.70 Maharashtra

141.75

'Shevan' ~do- 63.78 Gujarat

63.78

'Karingotta' Samadara indica 205.55 Kerala

134.66

5

Drift nets

Gill and drift net (' Hoga' and 'budi jal')

6

23 F: Long and cylin~ clerical

24 F: Triangular piece

7

L=30.0; D=2.5 to 3.0

1=9.0; B=4.0; T=8.0

28 F: Oblong flat on one L=]6.5; B=5.5; T=l2.0 side and round on the other side.

Bottom set gill 27 F: semi triangular 11.0; B=8.0; T=2.0 nets ('Khandali jali') piece

Bottom Set and drift nets ('Dhakal & valli Jala')

Gill and drift nets ('Aila and Mathichala vala')

25 F: Small-reetangular and flat.

26 F: -do~

34 I: Long and cylinde­rical

35 I: -do-

L= 10.3; B = 8.3; T=3.0

L=lLO; B=8.0; T=2.0

L=30.0; D=3.5

L=30.0; D=3.8

L = Length; B = Breadth and T = Thickness; D = Diameter.

IJJ p ...,_

<.:::: 0 :::! ,::,

"" "t :: 0 "' ~ 1:>...0 ~ ~

0 () 0 p ~ ;:s ~~

~ ~ 0 .... $:: :; "' ....

<.:::: '-P ~ ~ ... .. :::: ;;; -~.; a "" ~ ; ~·<a ~ p ..... c:;g· p "' ;;:- 0 'I ;:s

~ 8 P...a

0 ...... P... ;::-,"" (\} ~

/j'Tl p -..... a "" p -a ;:;· .,.,..<a

~~ p

l'O;;:-"" .... P... .... "" 0 ::: ~ "1::)',

;::~ 0 ~ ;:! (t)

Ol>r <.:::: a

"' v"' ., a ~~

;· b5 .($;) .::

a <.:::: :::. :::!

"' <.::::

8atyanarayana and Kuriyan: Investigations on Wooden Floaiing Materials- 'Ifie Loss of 'Buoyancy undel' continuous Immersion in Water and tfte 'Rate of its 'Redemption fJy 'Drying

152

80MBAX MALABli.RtCUM

{ Or!ad. U!ldGr Sue.

k~e Orlod uP/.!..ar S.tlod.e

,1: ', '

\ \

SAMAOERA tN.DICA

ALSTONIA ,SCHOLARIS

{Drl<td l!nder Sun J,

l·G 2·0 z·o Time; off cfryfng

Fig: 0

G:MELIMA ARBOREA

7

2·0 Q-!5 1·0

Time of d.J"ylnQ

Erythrina indica : The table IV .as well as Fig. 5 reveal that within the floats having identical volume (13 D & 14 D) the flat one is found different in dr­ying quality than cylinderical one. The shape and area of exposure mainly con­trols the property when exposed for dr­ying in both shade and sun.

Gmelina arborea: The samples of this material have got the same property 1n drying earlier except one, (i.e) 27° F, which takes long time mainly due to its shape and volume.

REFERENCES:-

Kuriyan, G. K. and Satyanarayana, A.V.V, 1961. 'A general account of the wood­en floating materials used for fishing nets in India.' Jour. of Timber Dryers' and Preserver's Association of Ind.

(4).

Satyanarayana. A. V. V. 1960 'PreliminarY studies of certain characteristics of' spherical fishing floats. Ind. Jour. of Fish. (2).

FISHERY TECHNOLOGY