Tank Testing

[TimClark]

I know all of us aren't available to tanks that include the computers for calculating different factors. So I was wondering if anyone here used a "modified" way of tank-testing that will show the basic actions of a hull. Thanks.

Tim

[Willallison]

There was an excellent article in Proffesional Boatbuilder some months back regarding tow-testing models - well worth a read. I'm away from my mags so I can't tell you which edition sorry....
I also know Tom28571 has done some 'back-yard' tank testing - he's away too at the moment, but maybe when he gets back we could pester him into giving away some of his trade secrets!!;)

[FAST FRED]

Check on the AYRS , Amateur Yacht Research Society , they have been doing backyard tank testing for 1/2 a century.

Their method is to compare two hulls to see which is better , period.

This can easily be done with small models and a bath tub sized water tank that emptys into a chute , where the models are on a tether. like a sea saw.

Works quite well , but gives no data for computers , just shows which boat has less drag.

Similar results can be had by towing the set behind a rowboat , but water speed is harder to measure, as is repeatibility .

FAST FRED

[RANCHI OTTO]

I have carried out several tank tests (resistance and self propulsion) for high speed displacement and planing craft.

[yipster]

beeing very curious and finding little free info on Amateur Yacht Research Society i ask you if self propulsion planing high speed tests were on radio control ?

[RANCHI OTTO]

normally the model in large scale is selfpropulsed with electrical motor.
the torque and rpm are recorded at shaft.
from these figures you calculate the power vs speed curve.

[RANCHI OTTO]

"Bagliani Class"

Model scale 1/10

Length = 26.15 m
Speed = 45 knots

Selfpropulsion tests in Vienna Model Basin (Austria)

[yipster]

big 2.60 m model, thanks Otto, here some more pics from your site (http://www.ranchidesign.com/english/index-en.htm)


http://www.ranchidesign.com/Gallery/bagliani1.jpg


http://www.ranchidesign.com/Gallery/bagliani2.jpg

[RANCHI OTTO]

The model length is the max. permitted according to the trolley speed.
Bigger model.....corresponds to more true results.

Even the small propellers have their openwater tests.
So doing it is possible to calculate all hydrodynamic coefficients and later recalculate the final propeller geometry and efficiency.

The sea trial results for this craft were very closed to the speed vs power curves.

Selfpropulsion model tests are very expensive but for military craft the penalities are.......very expensive too!