Hull Resistance Holtrop and Oortmerssen

[dalls]

I have been looking for Oortmerssen formulas for calculating hull resistance. Does anyone have the formulas or a spreadsheet for this method.

On another note, I have the papers for the Holtrop method 1982 and 1984, however I am having trouble with the wave resistance formula. It doesn't yield the same results as the examples. Formulas for the Holtrop method in section 8 of "Principles of Naval Architecture" by SNAME indicate that I may not understand how to use the formulas.

The confusion is in the model-ship correlation allowance Ca. The original papers use this this to compute a resistance Ra, SNAME concludes with a Rt = 1/2 x rho x V^2 x Stot[Cf(1+k)+Ca] + Rw.

Any help would be appreciated.

Regards
D Alls

[yipster]

maybe you can find some helpfull info in the wetted surface area - approximate formulas thread (http://www.boatdesign.net/forums/showthread.php?t=930&highlight=hull)

[jehardiman]

See table 13 on page 61 or page 93 of Vol II of the new version of PNA. It has the values/calculation of Ca based upon Lwl.

Wether you add it as a factor to Cf and therefore to Rf or leave it as a seperate factor (i.e. Ca becomes Ra) it is still the same.
Rt = Rf + Ra + Rw
or
Rt = (speed density factor)*S*(Cf) +(speed density factor)*S*(Ca)+ Rw
or
Rt = (speed density factor)*S*(Cf+Ca) +Rw

All the same.

[dalls]

Thank You jehardiman, that clarifies the NPA version. Do you use a hull resistance program?

Do you have any suggestions on how to get the formulas for the Oortmerssen method?

Regards
Dalls

[jehardiman]

Go to your local library and see if they can get a copy of the International Shipbuilding Progress issue it was in. Or you may be able to order it from

Delft University Press
P.O. Box 98
2600 MG Delft
The Netherlands

Fax
+31 (0)15 278 1661

Telephone
+31 (0)15 278 5121

[dalls]

One other question, the formula in PNA pg 92 has the equation

Rw/W = C1 * C2 * C3 * exp(m*Fn^d) + m2 *cos(lama*Fn^-2)

The Holtrop 1984 equivalent formula groups the exp term

Rw-A = C1 * C2 * C3 *W * exp(m*Fn^d+m2*cos(lama*Fn^-2))

which one is correct, PNA or my Holtrop interpretation?

Also why the Rw-A?:confused:

Any help would be appreciated.

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