Heeled Waterlines

[JagerL]

I know this topic has been discussed in other threads but I haven't found a direct answer before.

I am looking for a program from which I can generate heeled waterlines. I use Maxsurf for my design work. I know Hydromax is supposed to be the complement to that program that generates heeled waterlines, but the demo version does not let you import files, and there is no student version.

Does anyone have any ideas for a starving student/amateur designer.

Thanks in advance!

[Eric Sponberg]

ProSurf lets you create and plot heeled waterlines.

Eric

[JagerL]

Thanks a lot!

I'll try it.

Anybody else have ideas?

[gonzo]

The static heeled waterline is very different from the dynamic one. As the boat speeds up it changes. Either experience with a hull type or a tank test can give you an indication of the changes.

[JagerL]

Would I still be able to analyse the general symmetry/asymmetry of the hull? I am just trying to get some sort of idea. Here is a picture of the design I am working on. It is a all too common on this forum mini :D

[dougfrolich]

maxsurf will let you rotate the hull, it is much fater to let hydromax do the work for you, but if you want to translate the hull yourself in maxsurf choose your rotation point location and rotate the(hull) surface to whatever degree you want. To me it is much better to check out the waterlines in plan during large angle stability calcs. in hydromax. You can run many different load cases in a very short amount of time.

[dougfrolich]

oh yea, from what i can see looks like a great hull!!!! Do you have more renderings posted?

[JagerL]

Thanks for the reply! Every time I try to rotate the hull in Maxsurf, the model splits in half. Could you explain in more detail how to do it with the hull staying intact? I have attached a page of renderings. I'll post more when I get the next batch in. Still trying to make the jump from my modeling program (maxsurf academic) to my rendering program (Rhino academic) The hull has been recently changed in that the transom is a little narrower, and a little more volume aft. Comments/tips/help greatly appreciated!

[dougfrolich]

Import your model from rhino back to maxsurf as a 3d .iges file. Use a new file name. Then set up your grid spacing. You may have to adjust the orientation of the model so the plan,profile,and body plan are correct. you will be prompted for that info when you import the iges to back to maxsurf. To heel your model chose the rotation point, found under controls, then rotate the model- use numerical input to control all the translation about the appropriate axis. But if you get hydromax you will find it to be a great tool for this kind of thing. Great looking model and renderings

[Tim B]

Ok, thismay take some time to work out, but I want to do something similar myself. My take on this comes from the view that rhino can draw contour plots (planar) in X,Y with constant Z. so all we need to do is to rotate the hull in rhino (easy... selall ; rotate ; n degrees) then contour from some base point. Ok, I know what you're about to say, contours, not realistic waterlines... but what if you knew the sinkage and moved the hull as well? in fact, if you think about it, you can evaluate all 6 degrees of freedom... It's getting complex. Simplistically, all we want is a small script which will heel/pitch/yaw/translate a hull. Assuming that the whole hull is on a single layer, use sellayer (I think) and then just rotate it in script and write the contours to separate layers.

I'm sure a student can manage that,

Tim B.

nb, I'll have a look at it myself over the next few days.

[Tim B]

yeah, two commands to select layers:

SelLayer
SelLayerNumber

I suggest that the latter would be most useful

Tim B.

[Tim B]

Ok, well as it turns out, It is almost too simple to beleive. I'll attach the command script. This works in normal boat co-ordinates where X is longitudinal and Z is postive upwards. The script rotates the model by ten degrees, then draws all the contours on a new layer called "10 degrees". I'll leave it to you're imagination to do it with more angles, different directions, or whatever. Be careful of the description of the contours, it's not what you think. you define a direction parralell to the contour plane which rhino then steps perpendicular to (kinda logical)

All The best,

Tim B.

[JagerL]

Thanks everyone for your help. This is what I have found. Using the rotate 3D command, you can define a new axis of rotation. As the boat heels, it sails on a new axis (roughly between corner of transom and centerline to bow). This is greatly exagerated on the mini. So I defined my axis (estimate) and rotated the hull about that axis. Then drew contours perpendicular to original axis. I achieved sucess after I realized that I first told the program to draw contours at .1mm not .1m. That froze my computer for about an hour :p . Anyway, thanks for the help!

[gonzo]

Depending on the hull shape the wave produced by motion changes. The length is proportional to speed, but the amplitude is to hull shape. The finer the hull the less amplitude. One of the effects of the bow wave is to produce a hollow amidships. This reduces the floatation and therefore the righting moment.

[JagerL]

I was attempting to analyse the waterline symmetry in order to evaluate my steering FD. The appendage angles on these boats get so extreme because of the width. Does the hollow form symmetrically or asymmetrically?

[dougfrolich]

Yes, I agree with gonzo, and that is yet another reason I would recomend hydromax, because you can combine wave form analysis with the large angle stability analysis, and observe the waterlines or any other contours behavior, with many, many different load cases and wave patterns in a very short amount of time. all the while tracking various centroids and there movement.

[JagerL]

That is basically what I have heard. Unfortunately I don't have $750 for the program. I am hopeing they will make a student version soon. I really like the Maxsurf platform, but the academic portion is difficult since they only let you have three surfaces. That translates to a hull keel and bulb only. It is difficult but I have found a couple of ways around it. It is certainly better than the alternative, $$$$. Hydromax demo won't even let you import files.

[gonzo]

Asymetrically because of a several reasons. The shape is different on each side when heeled. Also, the boat is not moving parallel to the centerline but has leeway. Another cause of asymetry is the turbulence caused by the appendages towards the windward side.

[rxcomposite]

Dear Eric,

About 5 years ago, our Naval architect was measuring the trim of our newly built boat. He was using a wooden cross fabricated by the carpentry shop. When i asked him what is that, he said it is a "Sponberg Cross".

Was it named after you? Did you invent it?

I have read many of your articles in Professional Boatbuilder Magazine and i must admit i am a fan of yours with regards to your knowledge in the boatbuilding industry. I just dont know where to post this thread.

regards,
Rx

[Eric Sponberg]

RX,

Yes, I did invent the Sponberg Cross and published it some years ago in Professional Boatbuilder magazine in an article that had to do with weight management and stability tests. It is not a protected design, nor patented, so anybody can use it. Having it named after me was not necessarily planned, but it's nice nonetheless. Thanks.

Eric

[rxcomposite]

Thanks Eric.

Now i know. I kept my mouth shut then because i didn't want to be a dummy.
Now i have the bragging rights.

Rx