Maxsurf stability problem

Hi sn1987,
It seems to me that here surfaces do not adjoin correctly- see the file. Through link jointing they have no general tangents.
_______________________
NA Razmik Baharyan

 

Hi sn1987,
I have tried to help you a little bit still. The top of the side at the bar stem has corrected by importing your file from Maxsurf in Rhino 5. I publish the file that has seen outcome. I excised two horn for sides as they have not liked me. There is a sense in their installation only if will be is support of a deck, but I do not see a deck above them. I hope what is it will not be to you irritate, but you know that it is impossible to find two people equal on taste. But it is insignificant.
I see other:
For the bar stem there is a hump, and in the position of joint with the keel there is a hogging. Except for that is exact in this zone there is a dark spot in the shell plating which is meant with a cavity.
For comparison I was made calculation of hydrostatics on Orca3D for alleged DWL. It is received on my expectations for T=2m:
Displacement 37,62t
LCB=7,725m from transom, Cb=0,253, LWL=15,193m
I accept prognostic VCG=70 % Hmin=2,8m, thus GMt=0,715m
This outcome very close up to that is received on Maxsurf Stability for T=2m:
Displacement 37,07t
LCB=7,693m from transom, Cb=0,252, LWL=15,185m
At VCG=2,8m GMt=0,698m
Has found data for the pilot cutter "Gresholm" made of a tree, with close ship dimensions /m/:
Lbp x B x H x T = 16,00 x 4,90 x 2,60 x 1,60
Crew-2, Places for the seat for 8 escort pilots.
Displacement 43t
I regret that I do not have data about fishing motorboats.
There can be you have found the good prototype with very close ship dimensions and for this purpose expect T=2,2m.
But if it no and the draft of the full vessel is still unknown then to have to arrange not less than 4-5 prototypes which to you should be compared for an estimation of the loads and accordingly the draft of the light and full vessel.
With it I terminates to help. I wish you to end the project successfully.
______________________
NA Razmik Baharyan

 

Hi sn1987,
I publish Power Analysis file made on Orca3D. If still you have not picked the engine it will help you to pick eligible power and speed. And if has already picked power these calculations will help you what speed will define.
_____________________
NA Razmik Baharyan

 

Do you really think Savitsky method is applicable to this ship ?. That awful!
We are going to see, for the first time in the history of mankind, a fishing boat of this type operating in planing mode.
I see you've removed "NA" from your signature. You have done well, my friend.

 

Hi All,
Hardly the author of the project wants the vessel was slid slowly as itself has picked a gliding hull form!
Whether this vessel will glide or not?
As is known from the planing theory if the vessel have speed relevant Volumetric Frude number Fnv=from 1 to 3 then we have a transient regime of movement, and at Fnv => 3 then we have a mode of pure gliding.
Let's see at calculations:
At chosen from me parameters for draft T=2m and VCG=2,8m at speed v=35kt receive a mode of pure gliding with: Fnv=3,15; Trim=3,94deg and Ntotal=2897kW.
Whether this version the stationary engine with such power is possible to install on wood vessel? There can be weight restrictions will not suppose it.
Then it is necessary to pick the second version the engine of smaller power:
At 12kt Fnv=1,082 Trim=2,89deg and N total=471,5kW
At 20kt Fnv=1,803 Trim=4,678deg and N total=1228kW
Speed which almost comes nearer to pure gliding:
30kt Fnv=2,7 Trim=4,7deg and N total=2140kW
In a word this vessel has all odds to be move in a transient regime of movement.
But as I have said for the first time, we shall better keep the author himself to decide the problems!
______________________
NA Razmik Baharyan

 

Hello sn1987,

Sorry for the late reply. Find attached the model a screenshot of how a skeg can be created without trimming by using Maxsurf's inbuilt ability to close the boundaries. Also note that there are no closing surfaces at aft, forward or top (unlike Freeship). Maxsurf closes these surfaces on its own. Please do not go into the details of the model because its just a rough model and not meant for any project. Created this model only to demonstrate how the functionality can be used.

 

Hello everybody,
Band covering keel from above should be removed, because calculations on hydrostatics display untrue outcome - without the cubage of volume of keel. See the file.
Example at the rate with program Orca3D for T=2m:
With a band- displacement= 37,36t
Without a band- displacement= 37,62t
______________________
NA Razmik Baharyan

 

Hello guys,
thank you for your precious help. Rabah How did you correct the bow cone problem in rhino?For your last post I think the difference with orca3d is due to the different analitical approach of the programs.
Devudegoa how did you create the skeg? by adding three plane surfaces and then bonding them togheter? Sorry for the questions

 

Hi,

Don't worry about asking questions. The best thing about this forum is that you can always come and ask questions. So feel free to ask.

Regarding your question about skeg, it doesn't involve any bonding. It's just the default Maxsurf surface which comes with 9 points. Go to surfaces -> add surface -> default. Then simply manipulate the points to position the surface. You can check by opening the model which I have provided.

 

Hello sn1987,
Before to begin correction of the side in Rhinoceros 5 it is necessary to save Deck line in the fore.
1. It is necessary to click on the defective surface and then with “Curve from object” and “Duplicate Edge” it is saved Deck line /curve AB - See the file/.
2. Too most we shall make and from the remaining part of the side to receive Deck line /curve BD/.
3. On view Front it will be traced a new line which to lay on the surface of section of the side there where we want to fix the edge of surface New bow topside.
4. With "Trim" we excise the side on this line.
5. With “Curve from object” and “Duplicate Edge” it is saved cutting edges of the upper and lower portion of the side.
6. These two lines it is pooled and saved as one whole line.
7. The following line which is necessary for us is already fixed from the edge of Bar Stem.
8. Now one more line - Deck line is necessary for us. It is visible that curvature of the old line is poor. It is necessary to receive perfect curvature from the new line:
8.1 From reserved line BD it is necessary to outline piece BC. As already point C is fixed we shall use the function "Split".
8.2 It is pooled two lines AB and BC in general curve AC with "Group" and "Join".
8.3 It is selectable curve AC and then with “Points on” or “Orca3D Control Points on” and “Edit Control Points” we moderate quantity of control points and it is transferred them so to receive ideal curvature of line AC.
9. On three lines we create a new surface “New Bow topside” with “Sweep 2 Rails”. Thus first Rail is line at Bar Stem, second - Deck line and “cross section curve” - the third line /the edge of jointing inclusive point C with surfaces Topside/.
_____________________
NA Razmik Baharyan

 

Dear sn1987,
I want to explain you too and how the internal constructions influence calculations on hydrostatics.
I have tested it on my back in an extent some sleepless nights until then while have understood where I am mistaken.
Has understood the following:
If in the model there are traced internal constructions, for example: double bottom, lower deck, longitudinal and transverse bulkheads and so on, on hydrostatics or is impossible to make calculations or false.
It is received from for that programs for making the mathematical model of the outboard shell of the vessel demand as compulsory condition of the normal to the created surfaces had directions from the inner side of the vessel out to water, i.e. from inside to out. For this purpose when it is necessary to calculate hydrostatics, to suffice only the surface ensuring tightness - bottom, side, deck and transom. If there is a skeg - only contours the bound outside with water.
Everything else if it is traced, it is necessary to put in separate layers which should be frozen at calculations on hydrostatics, intact stability and unsinkability.
It will be better if the file inclusive only shell plating, deck and transom, to save separately, and internal constructions to inscribe in other file.
Even when you work with Maxsurf Stability there is no necessity to draw internal constructions. The information for the walls of tanks and for the bulkheads of cargo tanks is included into the general table, and location of the transversal watertight bulkheads enters in the program as an additional information, without necessity of their visualization.
_____________________
NA Razmik Baharyan