Novice Hull Design Problems - Canoe Keel

[Mr. Patrick Michaels 0]

I am a novice with CAESES, and am currently having some difficulties correctly modeling the keel of a canoe. I took the basic Yacht design tutorial as my starting point, and modified that heavily to get to where I am now. I am, however, having some difficulty getting the shape desired and would like some pointers. A few things that I am looking for:

 

1. I want to be able to set an angle of entry.

 

2. I'd like to be able to specify a rocker.

 

Most everything else I feel like I am fairly capable of figuring out, but I'm not quite sure how to deal with those two issues effectively. Attached is what I have done so far, and I feel fairly confident about most aspects of the design besides the keel. I'd like the hull to go along the curve I have defined for the keel now, though perhaps with less sharp edges.

 

This design will be used to make a concrete canoe, so one factor I have to consider with my design is constructability. What steps should I take to better fit the hull to the keel feature? I suspect the function definition will have to be changed, but I'm not sure how to do that effectively.

 

Thank you for the help!

Canoe2015-2016.fdbc

 

Patrick

[Matthias Maasch 21]

Hi Patrick,

 

let me prepare something for you. I'll come back to you later. Btw: Maybe you can send me a picture of the canoe design you want to achieve. I googled "canoe design" and found quite a lot different types. Which one is your favorite?

 

Cheers

 

Matthias

[Matthias Maasch 21]

Hi Patrick,

 

attached you can find my version of a canoe. It's basically a hull defined by keel line, waterline and deck line, closed by two surfaces at the aft and the bow.

For the two ending surfaces I used the feature "smooth joint to stem" which you can find in the section hull design. Both surfaces would probably need a bit of improvement.

 

The keel line is defined by two Nurbs curves considering the rocker angle. For the midship I used an FSpline to connect the two Nurbs curves smoothly.

 

 

 

I hope it helps a bit.

 

Best regards

 

Matthias

myCanoe.fdb

[Mr. Patrick Michaels 0]

Matthias, 

 

Thank you for your help! Attached is a picture of last years canoe in the construction phase, along with a photo of the finished canoe. The first photo was taken directly before we poured the concrete over that form. The design that I am looking for varies significantly from a typical canoe design, due to the unique challenge of it being made of concrete. I also have a few questions about the version you created:

 

1. You say that you define the waterline, is that waterline an arbitrary line or does CAESES automatically calculate where the waterline will be for a particular draft?

 

2. The values that you use for different variables seem to be "coded" of sorts, rather than relating to actual measurements. Do I need to set the actual measurements in this design stage, or is there a way to export the canoe so that the design essentially functions like a scaled model?

 

Thank you again for your time working on this! I can't begin to say how helpful it is!

 

Patrick

[Matthias Maasch 21]

Dear Patrick,

 

you're welcome!

 

1. The waterline is so far just a curve which you can control. It is usually best practice to define a parametric curve at water level in order to directly control the start and end angles, the fullness and the general shape. So the workflow would be: First setting a draft depending on your requirements, then controlling the water line shape according to your calculations.

 

2. Yes, I created several parameters depending on each other. This helps to keep points, curves and surfaces in place. The length parameter is one of the free parameters. Changing the overall length will influence most of the other values as well. For some intermediate points and curves I created a dependency on a ratio to the length parameter. Something like =0.2*length. The idea is now, that you can play around with the ratio 0.2... You can e.g. create design variables for those ratios. With regard to your question about scaling, you can scale the model after design/optimisation using the image technology.

 

If you have further question, do not hesitate to ask!

 

Best regards

 

Matthias

[Mr. Patrick Michaels 0]

Matthias,

 

You mentioned that it's usually best practice to define a parametric curve at water level to directly control the start and end angles. However, I'm fairly sure that with the shape I am hoping to achieve, following this practice will make it more complicated rather than less complicated. I really do like following the simple yacht tutorial for attaining the majority of the shape of my canoe, as it gives me the control over the majority of the shape. I'm also finding I can easily set a rocker just through manipulation of the keel line.

 

From there, however, I'm having trouble with three main things, which is an entrance angle, a curved bow and stern rather than the harsh edges my model currently has, and wanting to be able to have a higher alpha value at the bow and stern. For the entrance angle, I am looking for that angle to go all the way from the deck to where the keel is. The earlier pictures I posted of my team's previous canoe show what shape I am trying to achieve there mainly. With the value of alpha at the bow and stern, if I set it to what I think would be closer to the shape I am looking for, the model gets really weird and each side of the canoe clips through the other. Attached is a modified version of what I originally uploaded, where I gave up on setting the entrance angle or making the bow and stern remotely smooth.

 

As always, much thanks,

Patrick

Canoe2015-2016.fdbc

[Willy Maschen 1]

Hey Patrick,

 

i think a good solution would be to create a "Center Plane Curve" that gives the bottom conture of your canoe and finish the ends with the "Smooth Joint to Stem" feature. This procedure is explained well in the "Fast Monohull" tutorial, so i would suggest you have a look at that.

 

Greetings Willy