# Boolean operation failed after Union

**URL:** <https://discourse.shapr3d.com/t/boolean-operation-failed-after-union/36028>\
**Category:** Modeling Questions\
**Created:** [January 13, 2025, 8:08pm UTC](https://discourse.shapr3d.com/t/boolean-operation-failed-after-union/36028 "2025-01-13T20:08:01Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![janssnet](https://avatars.discourse-cdn.com/v4/letter/j/46a35a/32.png) [@janssnet](https://discourse.shapr3d.com/u/janssnet)\
**Post date:** [January 13, 2025, 8:08pm UTC](https://discourse.shapr3d.com/t/boolean-operation-failed-after-union/36028/1 "2025-01-13T20:08:01Z")

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Have seen several different occurrences of this topic, but still I can not figure out what I’m doing wrong. Could someone have a look at the attached video and perhaps offer some suggestions. Much appreciated.

I’m trying to make a boat hull 😉

> **[Union - Boolean operation failed.mp4](https://drive.google.com/file/d/1GFQ-NaecX-rUq6czc8CvaxH1czdLlwdT/view?usp=sharing)**
>
> Google Drive file.

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**Author:** ![SCALEMODEL](https://avatars.discourse-cdn.com/v4/letter/s/77aa72/32.png) [@SCALEMODEL](https://discourse.shapr3d.com/u/SCALEMODEL)\
**Post date:** [January 13, 2025, 9:00pm UTC](https://discourse.shapr3d.com/t/boolean-operation-failed-after-union/36028/2 "2025-01-13T21:00:36Z")

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Because there is a hole in your hull!

I thought the way you made that shape interesting.

I tried it and found there is a gap, union fail when a point touch but do not go through inside of each other.

If you follow the green lined you will see a small gap.

 ![image](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/3X/1/2/1299f4bc824ccabbab110013c82f7a2c84c82e5e.jpeg)

Once split note the gap in blue, you can delete that area and mirror/union, should not fail.

 ![image](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/3X/e/9/e9019b02d6db8a8d5d27a44a29a1332abf187b10.jpeg)

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**Author:** ![janssnet](https://avatars.discourse-cdn.com/v4/letter/j/46a35a/32.png) [@janssnet](https://discourse.shapr3d.com/u/janssnet)\
**Post date:** [January 14, 2025, 7:50am UTC](https://discourse.shapr3d.com/t/boolean-operation-failed-after-union/36028/3 "2025-01-14T07:50:56Z")

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> Because there is a hole in your hull!

😂

Haven’t been able yet to reproduce the little blue area you’re showing. Will give it some more attempts tonight. Thanks very much for your reply.

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**Author:** ![janssnet](https://avatars.discourse-cdn.com/v4/letter/j/46a35a/32.png) [@janssnet](https://discourse.shapr3d.com/u/janssnet)\
**Post date:** [January 16, 2025, 2:05pm UTC](https://discourse.shapr3d.com/t/boolean-operation-failed-after-union/36028/4 "2025-01-16T14:05:21Z")

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Too bad. Looks like this is not the problem. The gap between the body and green line in your screenshot is most likely the result of the spline not exactly starting 90 degrees.

Have done a simplified build of the hull in the attached video. One with a non-rotated (=non-lifted) front (works well) and one with a 5 degree lifted front. Does not work well.

What is going wrong here? I can’t figure it out!

[![](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/3X/f/5/f5b13fd5559cbcadd8b970daefd5eb8754985727.jpeg "Part 2 Boolean operation failed") ](https://www.youtube.com/watch?v=JkfsJa6TSg0)

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**Author:** ![SCALEMODEL](https://avatars.discourse-cdn.com/v4/letter/s/77aa72/32.png) [@SCALEMODEL](https://discourse.shapr3d.com/u/SCALEMODEL)\
**Post date:** [January 16, 2025, 7:00pm UTC](https://discourse.shapr3d.com/t/boolean-operation-failed-after-union/36028/5 "2025-01-16T19:00:31Z")

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Don’t mirror and turn on the Section View to confirm that there is no gap, note its 90degree.

 ![image](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/3X/9/9/99859e127d0f012155a67d42c253968d14e3c7d7.jpeg)

Before mirror investigate by zooming the bottom very close you can see how sweep is warping.

 ![image](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/3X/0/f/0f4c410415e237c05460832b2c9d4efd9591961c.png)

Also in your new video you are getting that triangle I talked about before delete it and try to union, by deleting it your getting rid of that gap.

 ![image](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/3X/0/4/04477c7ace28260b61181e16d72884ea06ac45bf.jpeg)

If you want to further investigate you can place 2 box top and bottom, this will let you union.

 ![image](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/3X/b/8/b876882896bf61821b424d321d269f06f8ab39fa.jpeg)

and check the cross section

 ![image](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/3X/c/5/c53a7cc481b55bafc6e1b9169753f6e7bab2ecb4.jpeg)

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**Author:** ![janssnet](https://avatars.discourse-cdn.com/v4/letter/j/46a35a/32.png) [@janssnet](https://discourse.shapr3d.com/u/janssnet)\
**Post date:** [January 16, 2025, 9:04pm UTC](https://discourse.shapr3d.com/t/boolean-operation-failed-after-union/36028/6 "2025-01-16T21:04:14Z")

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Found it!!! Have no clue where this ‘triangle’ comes from, but deleting it does the trick.  
Thanks so much for your guidance. Much much appreciated.