Scheme for the model experiments with anti-pitching fins

&

Th. th of January 1962.

Soh.ae for the Model Ex.rjm.nts wjh

_{Br Àtjjtohjng Pin..}

Deif t Shipbuilding Laboratory Report No.81.

Ssveral model .xpuim.nts with fixed bow antipitohing fins have been made and they confirmed that the pitching motion of chip. can be effected by mean. of fixed antipitohing fins. On th. other hand, it i aleo confirmed that the asriouc problem associated with the use of antipitahing tins is that of transverse hull vibration both xperiaentaly and actually.

The purpos. of this experiment is to provide some further information relative to the problem of designing efficient and practical antipitching fine. The bulk of the experiment is

concer-ned with the ff.ote that fine of different oonfigulations and thi ness have on the pitching and heaving iotione, the phase ingles

between pitch and heave, the horimonta]. and vertical vibrations at

modele bow, end the resistanc, in longitudinal head waves.

The xperim.nte about the active antipitching fins and built

up

antipitohing

_{fina an, *lso going to be mad. later it possible.}

Tb.

effects of fin .rticular, on pitch reduotio, bw

_vibra4oA

and recitano, which mers oonfijm.d br foraey ext)eriaente.

*.

area.

The reduction in pitch is approximately linear with th. in orease of fin area but both bow vibration and resistance in1.

creas, with fin area' b). _{japect ratio..}

Small changes in fin dimensions with a constant fin area havi

negligible effect. on

pitch reduction and resistance. Its ef-fect on bow vibration has not confirmed yet.

o). TiD t.noe.

Ras hein confirmed to have good effects on pitch reduction and

bow vibration.

-2-&

4). qoftjuz'.tioz.

A fin having heiss or slits of proper sie. and shape

.ema to

b. ff.ctiy. for both pitch riduotion end bow vibration preves.

tion, but the effect has not oonfirmed yet quantitatively.

The resistance far

this fin,

_{however, is greater than that for} a fin without ho].. or slit..

Aspit ratio

2

Tin area _{12,800 (0,023 Av)}

Equipped with tip teno..

Ï

10 x 8 loLos

Tin A.

t:12

ftn31

Fin 12

ZinC

t: 12

_t12

_t12

tf2

.

I

s s s

i

Tin LI

t:18

t=

Tin A2.

t=6

e e e

1&x3

HoLes

3. !' arti,iIl,!a.

L.oatien

(aft of

TP) % L

Spas (total) i6o

k Titjz

odt1. to b. m.d.

PLa.tjiao4sl of ?.44 60 seri.. Os.d.1 Ne. 31. Cb

O65) i.

going to b. amid for Ui. tiste. Plaetio modsi is chosin to saki

it easy to aunt and ahangi fins.

,

!szLMu

0,9

1.1.

13.

_2x3e6.

1/DO

1/30

ft

0.

0,06, 0,09, 0,12,

0,30.

¡toas to bi

Pioh und hsae asplitude.

Rssietance.

Bow acoelsratio.