Adding Bulkheads 'n stuff to Freeship model

[lewisboats]

Adding furniture to a hull:

To add bulkheads, bunks, cockpit seats, even consoles and such, extrude a handy boundry edge (the shear is good) by .1 units, then extrude it again by 2 units. Zoom in on the first extrusion and delete the two lines that join the larger panels. This gives you a new panel floating in mid air. Shape the panel to what you want (if a flat panel...to the length and width you want)(if a box by extruding the edges further to complete the shape).Assign the shape (or panels of a complex shape) to a new layer(s). Move the shape to the position you want it by highlighting all the lines, using Transform/Move then shape it to fit loosely. Use the shaded mode on the perspective view, along with varying the waterline to find gaps between the inside of the hull and the edges of your shape and adjust to fit. Move the perspective view around with the points enabled to see if any penetrate the hull exterior. Correct any that land outside the hull and this should get you quite close. When creating panels with the offsets for the parts, allow a bit of extra to trim to fit. In the layers properties add density and thickness to get a CG of all the panels to help with weight calcs. Luan is 38 lbs per cu ft which is 1 4x8 sheet of 3/8" ply...Ocumme is 28 lbs per sheet. 3/8" is .375 ft thickness... for any other type find the weight of a 3/8" sheet of 4x8 and this is the weight of 1 cu ft.. If you place a plane under or penetrating the waterline you must make it an enclosed figure for the hydrostatics to work. always extrude surfaces UP if possible so you have a sealed surface under the waterline and always extrude all the edges when extruding perpendicularly to a plane. It's a pain to move all the extra points and such but some can be removed without harming the shape. Moving an enclosed box takes a bit of patience but it is worth it when you can trim the hull properly and account for most if not all weights. The only problem is that whatever you put in is mirrored on the other side so asymetrical areas like the galley get mirrored. Best to put a box to represent galley on one side and a locker or something similar on the other.
Read pictures from left to right top to bottom.


Steve
PS: missed a pic so it is out of sequence (pic of point outside of hull)...should go before the first perspective pic

[deepsix]

I would like to add that it is worth while saving the flat panel as a part, this way you simply import it whenever you need it rather than extruding and deleting lines.

When adding a bulkhead, I like to add a station at that point, then turn off all layers except the flat panel and simply add nodes and drag them to fit the station intersection in section view. You can use waterline intersections in a similar manner for horizontal panels.

It is possible to turn the symmetrical option off in the layer properties window so that you do not need a locker and galley opposite each other. Just keep the center of gravity in mind.

[lewisboats]

It is possible to turn the symmetrical option off in the layer properties window so that you do not need a locker and galley opposite each other. Just keep the center of gravity in mind.

Maybe in Delftship but not in free ship...at least not in the copy that I have.

Steve

[deepsix]

Is greyed out because "use for hydrostatics" is on, turn that off then you will be able to uncheck the symmetrical option. I tested on freeship 2.83+ and on v2.6, it works fine

[lewisboats]

Ahhhhh!!!! did NOT know that....thanks much, works like a charm.

Steve

[deepsix]

Im glad I could help

[drshaddock]

Thanks to both of you guys--saved me days of work!

What about finding the intersections of layers? It seems to me that if you inserting a new bulkhead, for example, and made the bulkhead extend beyond the hull, and you used the Intersect Layer command to find the intersection of, say, Hull and Bulkhead3, a new set of points would be created where Bulkhead 3 hits the faces and edges of Hull. According to the manual, this new line of points can also be made into a control curve. It would seem logical to me that you could then delete the exterior parts of the bulkhead... Is this just too easy? Of course, it's easier for me to offer the idea than to go check it out--I'm supposed to be wrapping up the design of an engine wiring harness tonight and just took a break to browse. Thanks again for your ideas!

[deepsix]

Thanks to both of you guys--saved me days of work!

What about finding the intersections of layers? It seems to me that if you inserting a new bulkhead, for example, and made the bulkhead extend beyond the hull, and you used the Intersect Layer command to find the intersection of, say, Hull and Bulkhead3, a new set of points would be created where Bulkhead 3 hits the faces and edges of Hull. According to the manual, this new line of points can also be made into a control curve. It would seem logical to me that you could then delete the exterior parts of the bulkhead... Is this just too easy? Of course, it's easier for me to offer the idea than to go check it out--I'm supposed to be wrapping up the design of an engine wiring harness tonight and just took a break to browse. Thanks again for your ideas!

I had not thought of this before so I gave it a try. It seems that the intersect command adds a node to an existing edge where another layer intersects that edge. In order to add a bulkhead using this command, the bulkhead part that is extended beyond the hull boundary must contain a series of closely spaced edges(I used vertical edges). A node will be added to the edge where the layer intersects it.

The method does work but adding the edges and deleting the remaining nodes takes a long time. I prefer to add a station intersection, import a basic bulkhead part, and drag the nodes of a bulkhead part to the station intersection line.

[lewisboats]

Think you could post a few pics on the process?

Steve

[deepsix]

Method 1 - Intersect Layers

1. Create a flat sheet with multiple edges. I have only added vertical edges but a complete grid would work better. Save this as a part.
2. Open model, import part and move it to an appropriate location (Figure 1)
3. Point>Intersect Layers, will add nodes to the edges on the bulkhead panel(Figure 2)
4. Delete the nodes which are not required.

http://www.boatdesign.net/gallery/data/500/medium/Figure_1.jpg
Figure 1

http://www.boatdesign.net/gallery/data/500/medium/Figure_2.jpg
Figure 2

I dont like this method, it is slow and tedious, but may be more accurate.

Method 2 - Station Intersection

1. Open your model and import or create a flat bulkhead panel
2. Calculation>Intersections. Remove all existing station intersections and add a new one at the location of the new bulkhead.
3. Make sure stations are visible - Visibility>Station if station is not visable
4. Turn off all layers except the new bulkhead
5. Move bulkhead part to the correct location in plan and profile views
6. In body plan view, add nodes and drag them until they match station line

http://www.boatdesign.net/gallery/data/500/medium/Figure_3.jpg
Figure 3 -Blue is station intersection line, red is the flat bulkhead panel.

http://www.boatdesign.net/gallery/data/500/medium/Figure_4.jpg
Figure 4 - Simply move the bulkhead panel to match the station intersection line.

http://www.boatdesign.net/gallery/data/500/medium/Figure_5.jpg
Figure 5

http://www.boatdesign.net/gallery/data/500/medium/Figure_6.jpg
Figure 6

This is how I would do it, but I am sure that there are better ways. If anything is not clear, ill gladly explain in more detail.

[lewisboats]

excellent info and I'll have to play with it to get comfortable. Here is a poser for you...how would you go about putting bilge keels on a hull? Looking at 2 keels about 20" deep, around 5.5 ft long (at the root) with a 55 or so deg rake forward and a 30 or so degree reverse rake aft, plate steel so there is no NACA shape to speak of. I tried backing the boundry edge off the centerline and extruding and shaping but it came out crappy with leaks. Perhaps a .part but how do you eliminate leaks?

Steve

[Guest625101138]

Add a cyclinder, shape it to suit. Seal off the lower end by extending the edge and closing to a point. Move it to position and ensure the top extends through the hull. If it is left as symmetrical layer you will have two of them.

If the keel is basically a flat plate it will stall at relativelt low angle of leeway.

Rick W.

PS Delftship Pro has a rudder and keel wizard - not sure if Delftship free has this.

[lewisboats]

If the keel is basically a flat plate it will stall at relativelt low angle of leeway.

it is a rather common feature in GB. Most are described as steel plates...although the possibility exists of building some shape into it with epoxy and filler. right now I am more interested in getting the keels into the drawing to work on the hydrostatics and get the sail balance going. Thanks for the info.

Steve

[lewisboats]

OK...got the bilge keel done but I've run into a problem...it isn't being recognized properly in the hydrostatics. Select it to be included and the LCR only moves a tiny fraction...regardless of the placement of the keel(s) along the length of the hull. I have even taken the keel down to 6" long and it still doesn't change anything. Got any ideas? I attached the .fbm of just the hull, the keel and the skeg.

Steve

[deepsix]

I will have a closer look later, have you turned on the use for hyrostatics option in the layer properties box?

[lewisboats]

yes...toggling it on and off only gives a minor variation and it doesn't change regardless of the position of the keels longitudinally.

Steve

[Guest625101138]

OK...got the bilge keel done but I've run into a problem...it isn't being recognized properly in the hydrostatics. Select it to be included and the LCR only moves a tiny fraction...regardless of the placement of the keel(s) along the length of the hull. I have even taken the keel down to 6" long and it still doesn't change anything. Got any ideas? I attached the .fbm of just the hull, the keel and the skeg.

Steve

Steve
I checked the keels and they look fine. They displace about 40lbs and take wetted surface from about 25sq.ft tp 67sq ft - that is the killer with these things. They will turn an otherwise nice hull into a dog.

None of my versions of Freeship or Delftship provide LCR. The give LCB but this is quite different and will not change much by moving keels with small volume about.

From a performance perspective you should try to use slightly fatter foils that are much shorter in length and the same depth. The higher aspect ratio will improve their efficiency.

Rick W.

[lewisboats]

I thought the Longitudinal Center of effort under Lateral Plane was the LCR...but it doesn't seem to work very well if it is. I put a 6 ft deep 2 ft long surface on the bottom of the hull (without any keels or skeg) and suspended it between the aftmost two points on the bottom...it didn't change the center of effort more than a few points. curious.

Steve

[LP]

I believe that Freeship only does the LCR computation along the centerline of the hull. I've got a similar problem with a design with twin keels. I've gotten around some of the problem by defining "hydro" appendages on the centerline and manipulate the layer properties to give the desired values.

You could do a "hydro" keel on centerline that is twice the area of a bilge keel, but you will have to manipulate the shape to maintain the desired LCR and VCR. (Disregard :Keep the thickness at zero, but build the bilge keels as normal. Leave the hydrostatics turned on for both and the displacement will be calculated for the "real" keels while the LCR will be computed from the centerline "keel". As long as the "hydro" keel is on centerline, it will not create a leak, but be sure to leave it as a 2D (all y values=0) shape.)

I believe this to be the case and I believe there will be some error where there is keel and hull overlap.

==================================================================================

Now I have to correct myself. The 2D hydro appendage doesn't work. I have made a 3D appendage that worked to my purposes. I'm working on a design with an offcenter centerboard (a portboard?) where I had to copy it on the centerline to get a lateral plane area for it. I did take your model and extrude a "hydro" board and did not get a change in lateral area. However, when I started giving it volume, (i.e. taking it off of Y=0) it started modifying lateral area. You might be able to make an appendage of infinitely small volume so you can fool Freeship into giving lateral area. Or, give the "hydro" board the volume and lateral volume of both boards combined turn off the hydro function for the real boards

[Martijn_vE]

I believe that Freeship only does the LCR computation along the centerline of the hull.

---- snip ----


I believe this to be the case and I believe there will be some error where there is keel and hull overlap.


You're absolutely correct Greg.

Martijn

[Guest625101138]

...
None of my versions of Freeship or Delftship provide LCR. The give LCB but this is quite different and will not change much by moving keels with small volume about.

...Rick W.

I have now found the Lateral Plane properties in both Delftship and FreeShip.

I failed to scroll down the hydrostatics window far enough to find them.

Rick W.

[lewisboats]

Well...this gives me something to work with. I expected to have some error with the overlap because the hull would hide some of the fins in the profile view (2 dimensionally) and also things will change as the hull heels and one fin becomes more vertical and the other less so. Also...the angle of attack and leeway will present all of the leeward fin and a portion of the windward fin (making the profile of the two keels appear as a single longer keel...if that description makes sense). Basically the dynamics of the two keels will constantly be changing as conditions change. Thanks much... It would have taken me a bunch more time to work out that I needed to add thickness to a centerline fin before it started to change the LCR. I probably would have been puttering on a different hull shape a few months from now and had it finally dawn on me.

Steve

[LP]

Looking at your model, I'd guess each board is canted about 10 deg. Intuitively, your effective lateral plane area will be cos(10) * area. Up to 10 deg of heel this should be constant as the windward board loses effective area, the lee board should pick it up. Your furthur reduction in lateral area with increased heel should not be any different than with a centerline keel yacht, I believe.

[mizzenman]

It did not work for me!
I exstruded a part of the shere upwards, but I was unable to delete the two lines that conects the new pannel to the rest of the hull.

What did I do wrong?

thanks in advance!

[LP]

I suspect you may have hit the collapse icon. And, did you extrude twice? the first extrude gets deleted after you do the second extrude.

Select one edge of the panel you want to delete and select the trash can. It will ask you if you want to delete one (or more depending on what you have selected) item. Select ok if the number agrees with what you've selected.

Another way would by to turn on interior edges (the icon to the left of the show both sides icon) and then select the panel that you want to delete. Again, hit the trash can and it will query you on whether to delete or not.

Good luck.

[kengrome]

It did not work for me!
I exstruded a part of the shere upwards, but I was unable to delete the two lines that conects the new pannel to the rest of the hull.

What did I do wrong?Extruding creates a new face in the previously selected layer, which is probably the layer that's shown in the selection list in the menu bar. If you turned off that layer your new face won't be visible -- it's there, you just cannot see it until you turn that layer on again.

You must also have the control grid turned on if you want to select the connecting edges so you can delete them.

[lewisboats]

You actually have to use edit/delete rather than removing the edge by colapsing as LP said. I usually deselect all then select the two small lines on the sides of the first extrusion and hit edit/delete. It asks you if you want to delete these two items (if it is more make sure to deselect all and try again). Kenneth is also correct in that if the layer that is current in the box in the tool bar is deselected in the layer dialog box then your face will disappear but still be there...on that other layer. Best thing to do is create a new layer and then do your extrusions...this should automatically assign it to that new layer.

Steve

PS: I did create the center keel and give it some thickness...worked quite well so now I have to play with it to get approximately the same area and move it around until I get what I want. Gonna have to add the sails first then balance the two...I just need the time to do it when I am not too beat.

[mizzenman]

Thanks guys, very kind of you!!
Using the 'thrash can' function instead of the 'collapse edge' was the ticket.

Thanks again

[LP]

Here's a trick that I just discovered. Maybe you guys already know it.

To co-locate two points in the same location, select the point to be moved, hold the ctrl key and select the destination control point. Now, just click on each X, Y and Z coordinate in the destination coordinate box and watch the first control point align itself with the second. Groovey, man.