i´ve used only _BlendSrf with some tweaking, then matched the edges using _MatchSrf with the _Multiple option. The middle surface is just a _Patch using the remaining hole edges and some _Blend curves to guide it. See Layer “Helpers” for more info and evaluate the result with _Emap:
i did not use _Sweep, only _BlendSrf. The first i did where splitting the edges at the 3 red arrows in my file. Then i created the 3 surfaces marked with an “A” using _BlendSrf using Curvature option. While the _BlendSrf preview was active, i´ve tweaked them using the handles provided to stay as close as possible to the existing geometry. Then every of the 3 blend surfaces marked with an “A” where matched on 3 sides using _MatchSrf and the _MultipleMatches option. In the _MatchSrf dialog i´ve chosen Tangency, Match Edges by closest Points, Refine Match and Preserve Isocurve Direction. Next step was to create the 3 pipes, then Split the 3 Blends with them. This is to make room for the blends created in the next step.
I´ve created the 3 other blends to connect the 3 blend surfaces marked with “A”. These 3 where also matched to the short naked edge of the main part near the 3 red arrows. Finally the remaining hole was done with _Patch using the 3 _Blend curves to guide it (of course using Tangency). These 3 curves where created using the _Edges option in the _BlendCrv command.
Btw. after every _BlendSrf command, i´ve selected the result and used _RemoveMultiKnot. Most important is that you tweak the blend surfaces using the handles while it is created.
Thank you for the detailed explanation.
Especially the settings you used for the commands.
One question about patch, I sometimes get naked edges or not being able to trim.
Is there general don’ts when using patch?
I kind of fix it by making used curve having less shap angles, but it’s an trial and error kinda way.
@Toshiaki_Takano, for the patch surface to be joinable make sure to select the outer edges (they must form a closeable border for trim to work) then the inner blend curves and increase the U and V Spans. I Used 14 for UV Spans and Sample point spacing of 0.6, Stiffness 1.