Identical constraints two fit point splines black two fit point splines blue

[jeffescott]

Why are not the two right hand splines not fully constrained and the two left hand splines are?

I speced them same way....

I am pretty sure I need these to be fully constrained top prevent screw ups later on.

[davebYYPCU · Accepted solution]

Splines are hard to fully define, I don't see why you need them fully defined.  When tweaked to your satisfaction, lock them with the padlock, they will turn green.

What does 

I speced them same way....

actually mean?

For a symmetric body, I only draw half, before a body mirror, (half as much sketching grief).

Might help....

[jeffescott]

Yeah sketching grief in spades

[jeffescott]

I speced them the same.  Means i speced the first two fully.  And they turned black. I then speced the last two identically to the first two yet they stayed blue

[davebYYPCU]

I did not use any rails in the loft, do you see a problem with that?

Compare my loft as Fusion supplied it to the Rail Sketch, damn near identical, from here.

Might help....

[jeffescott]

Yeah.  A smooth curve is required. I look at the lofts with and without rails.  
The ski will grab or slip as you roll it into a turn.  It can be quite noticable if it does either as you lean in

that said with all the problems i am facing  with just manipulating the splines.  There must be a better way. I need to figure out tangents to control point curves

[davebYYPCU]

So what part of these solutions are you struggling with?

tngtspl.PNG

[jeffescott]

Firstly thanks for the help

attached is the file of my attempt of mr French's method

I seem to get there but I can't find the tangent point on the last sketch

[davebYYPCU · Accepted solution]

As Ed said, (side comment,) to get front and back with his method, you have to split the body, so there is a front and back body.

I don't know if you know it but they are almost identical.  Doing it his way, they are only 0.008 mm apart. 

If you don't zoom in, it looks like it doesn't work, but it did.

May I suggest a top view sketch.  In another file you used these numbers,

Draw the centre line, and dimension it, for length and one end from the origin.

Draw 3 vertical lines, 55, 49, and 65 high, 

So now 3 of the 5 points on the spline are fixed.  Draw the five-point spline, connecting the endpoints.

With horizontal vertical constraints, make the end handles vertical, and the other 3 horizontal.

The point 2 and 4 are the widest tangent points now.

Splnnsktgh.PNG

Change these values - to the values you want to protect the innocent.

Now you have stability you can slide the front and rear vertical lines left / right to help guide the shape. 

You can adjust the handles longer and shorter to guide the shape.  

I have a mocked up a ski with those numbers and others from the earlier file.

SkiMuoDB.PNG

If you can read browser / timelines you will work out how it was done

Happy to answer question.

Might help.....

[jeffescott]

Big learning the magical properties of a centerline.  I will go through the timeline and figure it.  
wont get there till monday new grandkid today

Thank you