How does this happen - fins not orthogonal.

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Charles_McG

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My current build is a Ventris-based kitbash. I've put pods between the body and the fins to make a 'Ventris SLV'.

I used a technique that I first tried in a Wildman Sport V2 build - using a steel ruler across the base of the fins to force alignment while gluing.

ImageUploadedByRocketry Forum1467125644.343021.jpg

It made fins wonderfully in-line with the opposite one - but the pairs are not orthogonal. I got an X, rather than a +.

It's way too late to fix - the pods are glued into pockets. I'm wondering how it happened in the first place, and how to prevent it in a future built. I used the slotted tube from the Ventris - I had assumed they'd be 90' from each other. Bad assumption? Or can this alignment trick go wrong another way? The fin pockets lined up beautifully with the slots (visually).

ImageUploadedByRocketry Forum1467125959.564839.jpg

And I tried hard to make sure the fin and fintab were aligned right.

ImageUploadedByRocketry Forum1467126025.224037.jpg
 

Charles_McG

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I thought it would self-align, but apparently not. I think the next time I try it, I'll through a square on the rule/guide and check the right angle fins slots (or fins) and see if the center body needs to be coerced a bit.
 

MCriscione

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So long as they're still straight front to back everything should still fly just fine. :) That's a cool mod for that kit. I like it.
 

Charles_McG

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It's merely cosmetic. Just unanticipated.

I meant to snap a complete view this morning, but forgot. Here's the base view.

ImageUploadedByRocketry Forum1467208212.718497.jpg
 

neil_w

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I can't tell from your description where in the process the misalignment might have crept in. But I just wanted to say that that's a very cool kitbash, hope you'll post some finished photos and launch photos/video.
 

dixontj93060

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I can't tell from your description where in the process the misalignment might have crept in. But I just wanted to say that that's a very cool kitbash, hope you'll post some finished photos and launch photos/video.
Yeah, I would not worry about a bit of misalignment. Looks like a great build!!
 

RocketFeller

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Just pretend you did it on purpose, it looks very cool.
 

Charles_McG

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Before the school year ended, I had Alex, my elder spawn, cut the pod centering rings on his high school's laser cutter. Vented to release the ejection charge.

If I stay a BAR when my boys are through secondary school in 6 years, I might have to buy me a laser cutter.
 

K'Tesh

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My suggestion if you were to try again some time in the future, would be to go to payloadbay.com, and create a fin alignment tool that is for fins that are the width of the body tubes. While that is setting up, have a 2nd guide that is for the combined diameter of the body tubes, and then have your fins aligned with that. It might not be the prettiest alignment tool, but I'm sure it'd work.

I created a version of what I'm talking about based on a 2" Ventris body tube, and BT-60's, but had to downscale it to 50% to get it to work with the fin alignment tool.

View attachment Ventris SLV Tube Alignment guide half scale.pdf

View attachment Ventris SLV Tube Alignment guide outer fins half scale.pdf
 
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Charles_McG

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I could build the outline in PowerPoint, rather than payloadbay. The problem would be printing it. I junked my 11x17 inkjet because I only used it once a quarter (for winery ops reports) and the cartridges were always dry. I guess there's always the printers at the day job.
 

neil_w

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Printing in two pieces and cutting/pasting them together is easy enough if there are registration marks (or landmarks on the drawing that can serve as such). It only matters that the final jig is cut from a single piece.
 

tomsteve

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no help for ya here, but I learned what orthogonal means!:rolleyes:
 
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