Developed plates altered by an added deck

[Denis Pratt]

Trying to insert a lower deck out to the sides of a developed plate hull is causing some problems.
From a hull comprising side, bottom and transom layers, the procedure used was :-

1. Rotate all layers of the hull down by bow the desired deck slope.
2. Insert a horizontal plane at the desired depth.
3. Rotate all the layers of the hull back by the deck slope thus obtaining an aft sloping deck intersect line on the side plate and transom.
4. Use the new points of the transom and side plate to make add a face, which becomes the desired deck.
5.Crease the edges of the deck to flatten the deck where it butts the side and transom plates.

The outcome is a deck inside the hull, but the side plates now have limited development especially where larger curvature is involved.
Why has the side plates altered in development and is there a way to prevent this happening?

Attachments:

• dinghydecked.bmp

[giorgio zuppin]

Hi, Denisp.
If I’ve correctly understanded your proceeding – it’s a big “if” – the answer lays in the basic software properties.
When you extrude an edge on the middle of a face – as you heve done “adding” by points – the mesh is “stressed”: have a look at the interior edges!
So the process affects the curvature of all edges involved; of course by creasing them, things are more or less “normalized” but developability is compromised.
The good news are that all this is VIRTUAL… and you can go on keeping old developability data with measures of the new deck.
Of course there is an alternative and more elegant way to follow.
Arrange the layers to group the upper side plates containing edges of your wanted deck, export them as .part, import as new layer, extrude now the deck, delete all unnecessary layers.
You have obtained a deck as a new layer but NOT fisically connected to the sideplates, so there is no stress and developability is NOT affected.
Well, I hope it will help you, just ask if something is not clear enough.
Regards, Jurgen.

[Denis Pratt]

Hi Jurgen,
Thanks for your advice, There is now a fitted deck without messing up the developed shell plating. Had to trim a little off the deck after inserting but that was pretty simple to do with the intersect routing. Now have two hull files, one for hydros and one for construction, as the one for construction has a few leak points which I need to solve later, once I understand the issue.
So now am going to fit an outboard engine well into the transom, introduce a standard gunnel section to the beam ends and start preparing the cutting files for production.
Should be fun.
Thanks once again.
Denisp

[Denis Pratt]

As a matter of interest to anyone following my stumbling progress on this topic.

When the deck was finished it’s outer edge was compared to a waterline at the same position on the parent hull. This meant trimming the hull by the bow to get the deck horizontal and producing a water line at that depth, for comparison.

To improve the fit the edge points were moved to provide the best curve alignment in plan view between the deck edge and the waterline. These new point positions were then re-aligned in the Z direction to ensure a flat deck. Everything proved pretty good with the final fit. Of course the hull was trimmed back to original when finished.

Obviously, if the program could change a waterline into an independent edge a deck could be extruded from it more simply.

More work to see if this is possible, but learning all the while.

Cheers

[Author]

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