Freeship and Delftship

righting moments are particularly of interest to me. All the literature I have read todate makes a lot of suppositions and guesses. As I understand it I need to look at 2 components. 1) the form stability, the effect of the hulls buoyancy 2) that big hunk of lead on the end of the fin ( approx 1600Kg 2.4 mtr down)
At low angles of heel it doesn't have much effect but at 20 or 30 deg it sure does. extrapolating a RM1 figure seems very imprecise to me. I want to be more accurate. too stiff is as bad as too tender! I do not want the rig to explode!

 

keels

you mean if I marry the points on my keel centerline to some on the Hull centerline then extrude the perimeter to the same, it will be fixed and not balls up the design buoyancy calculations?

How about rudders?
I did one with a stock by adding a cylinder, if the rudder is closed with no leaks can I, and how, can I get the stock though the hull to the cockpit? That is without causing 'Design Buoyancy' issues.

 

I just downloaded and read the doc. Great! Step by step and just what is missing from the Freeship/Delftship manuals. You have talent! Plain English is not so simple. Economy of words and jargon. Many thanks.

I do not know why I did not think of this myself! I will try 2 approaches:

1) create a fin and add a lump or cylinder assigning my respective COGs and wts
2) creating a stub keel, just like a real boat, and appending my keel from the wizard.

Cheers,
I will let you know how I get on.

 

That may take some unnecessary steps, loses the shape, and presumably fairness of the original drawing (without some reworking) . . . so another method:

• -scale the width smaller by the half thickness of the keel. [Shape is maintained and fairness is maintained - it's just squeezed a bit.]
• -move the whole model sideways from centreline by that same half width.
• -extrude keel down and then shape keel from sideview - ie only one point at each location needs to be moved
• -extrude keel bottom back to y=0.

​

done

 

Are you quite sure about that uncharitable guess?

 

You would have to pony up for the pro version of DS plus the add on for inclined hydro

 

You can rotate the hull about the longitudinal axis (Transform menu) and redisplay the waterlines (Visibility menu) but the halves of the hull rotate in opposite directions so you have to repeat the operation to get a complete set of waterlines for both sides. I imagine some hand work is required to match up the waterlines on both sides.

You may be able to use it - I design & build canoes so the cross-curves are more important to me.

 

I think you must have forgotten that the original Freeship was written by the same person who wrote Defltship. The Freeship you are using now was taken over by somebody else.

 

You can mirror the hull and then tilt it to the desired angle of heel

http://www.boatdesign.net/forums/sailboats/mini-ocean-racing-scow-39114-8.html
post 112

js

 

Thanks to HJS I was able to do that as follows:

1 Disable "Show both sides" (Visibility menu)
2 Mirror about vertical plane (Transform menu)
3 Rotate about longitudinal axis (Transform menu)

It wasn't clear at what depth to insert the waterline as the displayed draft and displacement remained the same, which obviously is incorrect.

 

1 Put both sides into one layer
2 Check that hydrostatics is active
3 Go to Calcultions and Hydrostatics
4 Calculate with small Draught step
5 Check up what displacement is the correct one
6 Transfere the draught to Main particulars
7 Check LCB, you may have to rotate the boat transversal also
and go an other round again

good luck

js

 

In the spirit of full disclosure; that doc I posted a link to was not written by me. It was created by BDS Taylor on the YAHOO FreeShip Group at https://groups.yahoo.com/neo/groups/Freeship_HTandT_Group/info

I did write the earlier post and I tried to keep it as simple as possible which is no easy task with Freeship. I have over my career with the Coast Guard written a lot of instructions and manuals and I learned quickly that the KISS principle is rule #1. You simply cannot assume someone reading it knows anything about what you are writing. Using professional Jargon (every profession including boat design has it's own language) just confuses people.

 

We all hope this stuff helps you terrnz, some of us learned a thing or two as well . . .

 

It's been a great help and given me a new insight. I am reworking some of my earlier models and taking a more organized and planned approach. Some of the suggestions have made me 'palm v face...why didn't I see that before?'
I have a lot to try out and time is limited at present as I am in the process of relocating back to NZ after 6 yrs in China.

The bulkhead operation is similar but easier than what I have done, it works well. However my hull is not hard chine and I want my bulkhead to follow the interior contours exactly. When finished I hope to export the lines or coordinates to AutoCAD or similar with the intention of CNC cutting frames and bulkheads. If I insert a transverse plane with multiple points can I attach the bulkhead to it? I will try and see when I have time.

 

I use freeship and think it's just brilliant, though a bit tedious. You can, while adjusting points see how the hull changes in shape in all three directions, the different views even allow you to fair the surfaces properly.

I often go back to older designs and play with it. Managed to knock off over a 100N of drag in a previous hull. Also fared it out a bit and now I'm keen to see what it's gong to do on the water Nice to be able to make changes and see if the drag improves or not... then tune it some for best results.

Anyway.

One can output the stations, edit them in a cad program and so produce a fishbone structure from which to make the hull. You find someone with a laser machine large enough to mark the stations on boards and you cut it out... make them stand and lay the lengths over, wrap in plastic and you have a form you can glass over... You also have the exact form of the bulkheads and can be made in the same way.

For everything else there's mastercard... right ?