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  #1  
Old 07-09-2021, 02:34 PM
BobP_in_Nevada's Avatar
BobP_in_Nevada BobP_in_Nevada is offline
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Join Date: Aug 2012
Location: Sparks, Nevada
Posts: 47
Default Recovery Plan: Split Fin During Build

Hallo! I have a brief story and a question.

Today I cut out fins to a pattern, and was gang-sanding them down to target dimension. And as I'm finishing up the last edge and thinking to myself, "Gee, I think this is actually the first time I've ever made fins from a pattern..."

***crunch***

All three have a crack along the grain ... but it's not all the way through.

I'd really rather not start over. But I also need this model to hold up for at least six flights (Yep, it's my NARTREK Gold project. It's only a wee 18 mm min-dia streamer model, a little like the Quest Pip-Squeak, and I'm only flying it on 1/2A and A motors. The fins are symmetrical trapezoid in shape and 3/32". )

I think I can, first, rub some wood glue into the fractures and dry under weight to lock down the injury. And then, though I wasn't planning to, I think I should paper them.

What say the Voices of Experience? And thanks in advance.
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NAR #87762, NARTREK Silver, SAM #440, Not an actual Silver Snoopy awardee

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  #2  
Old 07-09-2021, 02:55 PM
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ghrocketman ghrocketman is offline
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Location: Michigan
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Default

Just soak the crack with thin CA.
Repair will be stronger than original.
They will hold up longer than you are interested in the rocket. Much longer than 6 1/2A and A flights.
'Nuf said.
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  #3  
Old 07-09-2021, 09:05 PM
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mojo1986 mojo1986 is offline
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Location: Kingston, CANADA
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What GH said. I don't use glues containing water to strengthen fins because I've never been able to control warpage. If you want to make a REALLY strong fin you can use thin CA with tissue paper. Just affix an edge of the tissue paper along an edge of the fin, give it a minute to dry, then drip CA along the fin/paper interface and 'squeegee' it with an old credit card, squeezing out most of the CA. After a bit of experience you can make a fairly smooth fin that requires little sanding, is rock hard, and has the grain almost completely filled.
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  #4  
Old 07-09-2021, 09:50 PM
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Gus Gus is offline
7/21/61
 
Join Date: Sep 2005
Location: North of Detroit
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Jeepers!

Two people in a row agreeing with something GH said (yes, use thin CA).

Someone call the Weather Channel and let them know that hell has frozen over.
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  #5  
Old 07-10-2021, 01:35 AM
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ghrocketman ghrocketman is offline
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C'mon noww, Steve !
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When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL
, if you have to ask what is "NORMAL" , you probably aren't

Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
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  #6  
Old 07-10-2021, 10:07 AM
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BobP_in_Nevada BobP_in_Nevada is offline
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Well, that's about the most consensus I've ever seen here. So be it.

Thank you, folks.
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Bob Portnell, Sparks, Nevada
NAR #87762, NARTREK Silver, SAM #440, Not an actual Silver Snoopy awardee

"Flying Like It's 1975"
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  #7  
Old 07-10-2021, 08:29 PM
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LeeR LeeR is offline
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Location: Colorado
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Quote:
Originally Posted by Gus
Jeepers!

Two people in a row agreeing with something GH said (yes, use thin CA).

Someone call the Weather Channel and let them know that hell has frozen over.


Make that THREE!!

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  #8  
Old 07-10-2021, 08:48 PM
TigerHawk TigerHawk is offline
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Thumbs up

Id recommend thin CA
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  #9  
Old 07-13-2021, 04:02 PM
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BobP_in_Nevada BobP_in_Nevada is offline
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Wow. Unanimity. Amazing.

So two fins repaired easily. The third actually completed its split. And in the process of repairing that, it got a little papering anyway, with the CA bonding the fin to the index card underneath. I cut away the surplus card and sanded away as much as I could of the glued card.

I'm really happy with this model. The 3-D printed fin jig did its job. Just need to prime and paint and it'll be ready for a trip to the playa. (Pics after I get back.)
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"Flying Like It's 1975"
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