Re: transom and deck

DELFTship forum Hull modeling transom and deck Re: transom and deck

John R. Coil

Hi! No bother at all. 🙂

If I recall correctly from your more recent attachment the angular results are possibly a result of you using a plane that is flatish (at least it looked that way to me).

If that’s the cause you will need to break that plane up into chunks and induce a curve if you want a curved surface. You can use the offsets I gave early on (for a radius of 4.8333) and then scale the resulting surface in the X and Y direction to achieve any radius you want (unless I’m mistaken scaling in only X OR Y, for non-uniform scaling in X and Y, will produce some form of oval rather than part of a circle). With CPs only on the upper and lower edge of a face you can scale them independently of each other.

Alternately, if you don’t need an exact size, add just two new edges to that surface. One should be moved very near the centerline and is there to assure a rounded surface and the other is kept at the same X value as the CP on the center line but is moved out Y. Make sure that neither of these new edges is a crease and you should get a curved surface whose curvature you can play around with by changing how far out Y the “midspan” control edge is.

About adding edges to the face that forms the transom: when you first form a new face from a group of selected CPs using EDIT > FACE > NEW FACE the program somewhat annoyingly looses all crease info for the old edges at the juncture of the new face of your model. Once you re-crease these turn on the feature that lets you see “interior edges” which will show you where the program is inserting detail into your model to determine how it will render your boat. If you look at your transom you should see it attaching most every CP defining the edge of the transom with every other CP defining the edge of the transom. It does this because the surface isn’t either flat or rectangular and the program is trying to come up with a surface based on the information it has. The trick to getting better results is to give the program more information and this is what I was talking about.

I find it easiest to start with CPs closest to the centerline. Select the CP closest to but not on the centerline on the top and bottom respectively and add a control edge between them. Then move to the next pair of CPs in order. You will see the “interior edges” settle down a lot and, also, they will no longer be drawn as straight lines across your transom which will cause a crease at the centerline edge as well as a pincushion effect that you should have seen.

In your specific instance you may find it helpful to selectively add a CP or two to your bottom edge to give lines attached to CPs of the top edge somewhere to attach to. Also, not every CP needs to be so attached … though if one does or not is a situational judgment call.

I’m guess this latter approach is what you may need to do.

Hope that helps.