Scale Speed - How to Calculate?

[ramius-ii]

If you know the speed of your sub in actual MPH (Miles Per Hour) how do you convert to the speed of a scale model?

Ed

[rcher]

If you know the scale

If you know the scale of your submarine ie 1/72 then you would mulltiply the speed by 72.

For example, if the speed of your sub is 5 knots, then 5 x 72 = 360 knots.

[seanletsflytwo]

also, if you wanted to

also, if you wanted to go backwards, from realto scale, then you divide

[Guest]

Correction, you need to divide

Correction, you need to divide by the square route of the scale.

i.e. in the case of my Vanguard, which is at 1/100 scale and the fullsize speed of 25 knots

25/10= 2.5 knots

Add in a model factor of between 1.5 to 2.0, which will give a model speed of between 3.75-5 knots.

This is the speed required for realistic wave formation/wake around the model and responsive control surfaces equivalent to the fullsize counterpart.

More information on this is featured in the book 'Model Submarine Technology' by Norbert Bruggen.

Models may get smaller but water molecules don't!

Andy



Edited By Sub culture on 1093467000

[koeze]

Sub Culture is right.

Model Speed

Sub Culture is right.

Model Speed = Square root Original Speed

This is a model rule used in Hydrodynamic Calcalutions ie towtesting model ships.

EJK

[ramius-ii]

Thanks Guys! http://www.subcommittee.com/forum/icon_smile.gif
The

Thanks Guys!
The only question left is what is the "Model factor"?

Add in a model factor of between 1.5 to 2.0, which will give a model speed of between 3.75-5 knots.

Best, Ed

[Guest]

The model factor is merely

The model factor is merely a number, without any units, inserted into the equation to account for the inefficiency of small scale props and control surfaces.

Whether you go on the smaller side of that number e.g 1.5 or larger- 2.0 would depend on how you feel the boat is performing in the wet stuff. Some designs ape their fullsize counterparts better than others- thus requiring a larger or smaller model factor.

You really ought to grab yourself a copy of Norberts book if you are interested in this kind of thing.

There is a lot more to this subject than can be explained in a few lines on a messageboard.

Andy

[ramius-ii]

Thanks Andy http://www.subcommittee.com/forum/icon_smile.gif The book

Thanks Andy The book does not seem to be avaliable which is why all the Q & A's.

Best, Ed

[Guest]

Thanks Andy http://www.subcommittee.com/forum/icon_smile.gif The book

Thanks Andy The book does not seem to be avaliable which is why all the Q & A's.

Best, Ed

http://www.amazon.co.uk/exec....4747035

The Amazon UK site seem to have some!

Also these guys seem to have some too-

http://www.sussex-model-centre.co.uk/Traplet_Books-1495.htm

Edited By Sub culture on 1093624879