How to draw a boat hull

[andrewWMZPK]

Hello,

I want to do some power boat hull design. I've had some parametric modelling experience with solidworks but I'm new to Fusion 360. The end game is to build a 4m long open power boat from CNC cut flat panels (e.g.plywood or Duflex). I must understand how to draw this myself rather than borrow another design from grabcad.

I'm having great difficulty getting started and getting the basic chined hull form modelled. I'm sure there are plenty of ways to achieve this and it sounds simple but so far I can't control the basic hull shape.. 

1. I want planar bottom surfaces in the aft half of the boat (for efficient planing).

2. I want curved surfaces in the forward half of the boat that can be formed from flat panels (e.g. plywood or duflex).

I've tried sweeping sketched lines and sculpting t-splines but not with good results so far. I'm having difficulty with the combination of a curved surface coming off a flat surface.

I've attached a screen shot of a basic hull shape I sculpted from a t-spline box on the weekend. On close inspection the aft end bottom panels aren't flat even though I used the "flatten" parallel to a plane command. The aft "flat" panels appear to be affected by the curvature of the front of the boat (the bending spline). The t-spline surface appears to be distorted (more visible with zebra analysis) around the "flat" to curved transition area. I also don't seem to be able to add dimensions to control the size of the t-spline box. I can sculpt and pull the t-spline box to a rough dimension but not set an editable and accurate length, width, height, angles like dimensioning a sketch. Appreciate any advice as to how to accurately sculpt a hull from a t-spline box.

Also appreciate any advice as to whether I'm heading in the wrong direction with sculpting t-splines and suggestions for a faster, more accurate way to get a basic hull shape modelled.

Thanks!

Andrew.

[cekuhnen]

@Anonymous

In Fusion you cannot edit the CVs of a NURBS surface. The software does not allow you do to that like in Alias or SolidWorks.

If you would loft it via T-Splines then yes in TS mode you can still later sculpt and adjust the individual mesh elements ( point edge face)

The design looks very complex / organic. I am not sure if this might not be better to simply sculpt by hand instead of lofting this 

from a crazy amount of cross section profiles.

Will this be later a full size model - prototype?

[andrewWMZPK]

kjlpdx - I suspect it may be easier to model a displacement hull with curves in all directions (like your very excellent looking kayak) hull using a T-spline in the Sculpt environment. One problem (and perhaps my thinking is too old school;) is that Fusion doesn't allow me to dimension a T-spline so the end result may be difficult to get to desired dimensions quickly.. I'm not sure though as I've not put much effort into T-splines as I also couldn't get my planing surfaces flat enough. I like to fiddle with dimensions, observe changes and end up with mostly nice round numbers to to fabricate accurately to. My old school engineering mindset and yes.. molded by a small amount of Solidworks experience a few years ago..

[andrewWMZPK]

cekuhunen -

Thanks for the help. I have very few constraints in my sketches. Possibly too few constraints.. I am having a lot of trouble editing a sketch after it's first drawn and closed. I feel like the Sketch environment is not stable? I've never had issues with sketch stability like this... Every time I re-enter a previously drawn profile sketch and adjust a linear or angular dimension (even by only a small amount) the sketch flips around one or sometimes both axis to create a monster.. Often I need to delete a few dimensions, drag the sketch back into the desired shape, and then re-enter dimensions. I suspect this won't be doing any good to any lofts that have been defined by the edited profile sketches or associated 3D geometry like the chine sketches. As you can see my profile sketches are very simple with only two linear and two angular dimensions to define them. All I want to do is tweak loft profile sketch dimensions and see my model change shape..

And yes, I'd like to fabricate from sheet material like plywood so the curves in the bow half of the boat will be conical and twisted. Only what can readily be fabricated from a flat panel. No concave "wave slicing" surfaces as you have sketched above at this stage. 

[andrewWMZPK]

Hi Browny-

Thanks again. I'm not sure how to revert to an earlier version. I'll swat up on reverting now:)

Yes, I think I'm possibly breaking the sketches somehow by tweaking the dimensions. See my comments above on sketch stability. I'm finding this a bit weird.. Never seen anything like it.. I'm starting to wonder if it's because I'm using a Mac.

And yes, after the mid plane sketch flipped around one or both axis caused by editing dimensions (by only small amounts like 5mm or 5 degrees) I dragged the end points of the sketch back into the correct position and replaced dimensions. This may have broken the connections to the chine spline sketch. I don't recall deleting any lines and redrawing them but I'll check myself on that from now on.

About the two lofts on top of each other.. I did a loft on top of the profile and chine spline sketches you helped me with a few days ago (I've kept your drawing as my basic starting point). I recall you mentioning you tested by lofting using the profiles and rails but I couldn't see any lofts in the browser tree so I assumed you deleted it.. I still can't see a loft in your base sketch... I did my loft in the sketches you gave me. I did a surface loft in the Patch environment as you described and also another model with a solid loft in the Model environment which also worked perfectly. 

[cekuhnen]

@andrewWMZPK

The engine is actually pretty stable - while it has some bugs here and there - but those bugs should not result into broken sketches like in your case.

Here is a screencast showing you how I build your design and that I can adjust everything quite well.

Key is to constraint sketches fully so that they are stable and plan ahead how you use constraints so you later can adjust width height etc...

https://drive.google.com/file/d/0Byzv_NlyKp_2bFByREcwbnBzOUE/view

[davebYYPCU]

Gooday Andrew,

only time I have had anything like that swinging, is placing constraints (usually horizontal or vertical), on spline handles.  Only sometimes they flip 180 degrees, don't know why, could be to do with the click position, but I undo, drag the handle back into submission and can normally continue.

Ah when I said that I had success with your model, I was in testing mode, wanted you to make the selections and learn the logical steps, but what I do in Test mode, is select all, and with a successful preview, I hit cancel.  

I have learnt to do this for the Loft error machine, it spits errors up, and I know it was to do with the last selection, if you ignore the error, Fusion will continue in preview mode.  That's maddening but now I know.

In your case there must be enough cache data to at least get something on screen.

Try testing each rail and profile, by turning them on and off, sometime you see why the problem exists. To fix the yellow icons, bring the timeline back to the first one and rebuild the sketch, it didn't look like the chine was broken, just unhooked.

Browny

[andrewWMZPK]

Thanks cekuhnen and Browny.

cekuhnen - The screencast and extra file will help greatly. I've watched the screencast twice but I'm short on time tonight to check it out properly but will get into creating some new drawings this weekend.

I missed the reason why you created separate side and bow loft surfaces rather than just doing a single loft from transom to bow?

[cekuhnen]

@andrewWMZPK Workflow preference - but you can also make a complete 3d sketch including drawing the lines by hand and then at the end do the loft at once instead of 2 times.

Glad to hear it is helpful!

[andrewWMZPK]

Hello again,

I'm still unable to edit a sketch dimension and have the hull loft adjust accordingly. I've just spent some time drawing another hull from scratch without any errors along the way and if I edit any dimension the sketch changes but the loft doesn't.. The file is attached. I'm missing something fundamental. Is there a box to tick somewhere to enable editing of a loft after it's made?

Thanks,

Andrew

[cekuhnen]

@andrewWMZPK

there are two possible problems:

1. Bow position sketch uses a reference from another sketch to set the dimension

2. Chine sketches lacks one smooth constraint while you added it first and then by accident assume you removed it but kept the curve nicely adjusted

so when you adjust the length of the boat then that spline becomes strait killing the loft rails!

easy fixes: https://drive.google.com/file/d/0Byzv_NlyKp_2cWN0ODFSVHhhRlk/view

your sketch and model is fine!

[andrewWMZPK]

Many thanks again cekuhnen. The video was extremely helpful and I fixed both of the problems very quickly. It works!

[draftingrus]

I am in the same place - Front Top and side view of the boat -resulting in a sketch of the shape on three planes - It is the connection of the three views that stymies my limited Fusion knowledge 

I set "3D Sketch" to enabled ... and tried to add vertical (z axis) lines of the right height taken from the profile (xz plane )...  but they did not "stick" to the original (xy) sketch ...  The Boat is an old Lone Star 16 that i wanted to modify 

[davebYYPCU]

I am not so sure of your question, so referring to the picture in message 30 just above, 

you have the side sketch, top sketch in 2d, and starting to make the shaded profile, right?

If I read it correctly, you have turned 3d sketching on too early, that profile will be better use to you as a 2d sketch on an offset plane, and not a 3d Lines.

Just quick, to get the deck / Hull 3d curve, from side and top view, turn on 3d sketch, use Project > Intersect Curve, Select the top curve in the side view, then the outside curve in the top view, Fusion will build the required 3d curve.

Now you can place Profile planes as needed, and Project > Intersect, each of those three lines.

Gives you those three magic purple points for a profile anchor.

I hope I have helped, if not let me know.

[lichtzeichenanlage]

You can find a set of 4 useful tutorials by choosing the Boat, Hull design techniques playlist here.

[draftingrus]

I had in mind to modify the existing hull to include a cabin, and wanted to make most of the mistakes on the screen rather in building materials - The term is "Pocket Cruiser " - The Designer has gone the way of the companies that made the boat - and the detail drawings are not in his collection

[davebYYPCU]

Is this a halfa post? seems like a shortened statement without a question.

[lichtzeichenanlage]

Not sure if this is a question...

[draftingrus]

Sorry I was trying to reply to a previous post I submitted years ago that I got a notification on recently - I must have screwed up (obviously)