# use of POLYCAD naval design software

Discussion in 'Software' started by JFD, Jan 30, 2020.

1. Joined: Jan 2013
Posts: 29
Likes: 0, Points: 1, Legacy Rep: 3
Location: india

### sujeethmonuAsst Professor(mech dept)

Even with this calculations in kg and metres, the values are wrong.
Check this hydrostatic calculation from the file which you sent me with (unit in m), only thing is I have enabled WPA(m2)=water plane area.

at T=0.15m, WPA=2.28m2 and Tonnes per Centimeter Immersion (TPC) = (water density of sea water in tonne * WPA in m2) /100 (in tonne/cm)
so TPC should be = 1.025 tonne/m3 * 2.28 m2 = 2.34 tonne/m since it is not divided by 100.
TPC value is correct but unit should have been tonne/m or it should be 2340kg/m.

so if boat is added with mass of 2340 kg, it will sink deeper in water by 1m.
for 0.025m increment in draught (as shown in calculation table), it will sink by 2340*0.025=58.5kg

At 0.15m draught, disp(kg)=223.876kg
At 0.175 draught, disp(kg)=223.876+58.5=282.376 which is apprx to 283.315kg as shown in calc table.

2. Joined: Dec 2016
Posts: 283
Likes: 57, Points: 38, Legacy Rep: 18
Location: Jamestown, Saint Helena

### pafurijazSenior Member

But I think you use a wrong draughts input of values.
this is the correct input for draughts that I usually input in the filed for this variable
every value is separated by ";" and the "," is for decimals without "()"

That is the way, and the values are progressive.
0,15; 0,25; 0,3
or in your case with dot as separator for decimal.
0.15; 0.25; 0.3
Try this type of input

3. Joined: Jan 2013
Posts: 29
Likes: 0, Points: 1, Legacy Rep: 3
Location: india

### sujeethmonuAsst Professor(mech dept)

got it. (0.15, 0.3, 0.025) working as well. (starting draught, end draught, increment draught)

4. Joined: Jan 2013
Posts: 29
Likes: 0, Points: 1, Legacy Rep: 3
Location: india

### sujeethmonuAsst Professor(mech dept)

I just mentioned that TPC value being calculated in polycad is wrong.

5. Joined: Dec 2016
Posts: 283
Likes: 57, Points: 38, Legacy Rep: 18
Location: Jamestown, Saint Helena

### pafurijazSenior Member

OK, fine. I hope you can solve that with the developer, in these days I'm a bit busy, with a work and I'm bit late..

6. Joined: Jan 2013
Posts: 29
Likes: 0, Points: 1, Legacy Rep: 3
Location: india

### sujeethmonuAsst Professor(mech dept)

Yeah mailed marcus regarding it. hope it helps in its development. Thanks a lot bro. I learnt a lot from you. Was not knowing about units changing at all.

7. Joined: Dec 2022
Posts: 2
Likes: 0, Points: 1
Location: UK

### KitegNew Member

The tutorial video copying polylines from old drawings is helpful. New to Polycad though I still have not managed to figure out the next stage; i.e. once you've created stations, sheer, stem etc as lines- how to then to develop surfaces on these polylines in order to built up the hull for fairing. Any pointers would be most helpful

8. Joined: Aug 2003
Posts: 279
Likes: 13, Points: 18, Legacy Rep: 45
Location: Edinburgh

### AndySenior Member

Hi Kiteg, you can either 1) loft through the station lines you have if you have enough (bow, midsection and transom at least) then modify from there, or 2) Turn all your curves into X topology curves then do an X topology lofting from them. Be aware that the lofting creates a network of interpolated curves based on your input curves, and not a surface as such. You can also create an X topology surface although this is usually a bit later in the process.

9. Joined: Dec 2022
Posts: 2
Likes: 0, Points: 1
Location: UK

### KitegNew Member

Very grateful for your reply Andy, I have now managed to create an X topology surface by trial and error though fairing it is proving tricky. My task then will be to work out how to obtain y/z cordinates at a given x, i.e. define a vertical slice through my surface to create mid-station bulkheads. I'm actually trying to build a model of a yacht I built years ago - lofted then with splines and ducks - when the IBM Personal Computer was still someone's dream!!!

10. Joined: Jun 2023
Posts: 7
Likes: 0, Points: 1