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Aug 01, 2021, 06:57 AM
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Lockey, what are the size of the hatch magnets, and where did you get them?
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Aug 01, 2021, 07:17 AM
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Never mind; I found them. I just wasn't finding anything in mm sizes, which is why I asked. But these will do.
Aug 01, 2021, 08:42 AM
Tony Audsley Retired Locksmith
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Quote:
Originally Posted by Jay B. Scott
Lockey, what are the size of the hatch magnets, and where did you get them?
10 x 2

https://www.ebay.com.au/itm/303437610698

Lockey
Aug 01, 2021, 09:54 AM
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I saw that they don't post to the United States. My 3/8" X 1/16" size is just a hair on the small side, but otherwise will fit with gap-filling epoxy. That might not even be necessary, in which case I'll just use CA and kicker.
Aug 03, 2021, 08:07 AM
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Below are the approximate printing times for the new wing parts. Please excuse the mix-up on the first three parts. Just follow the arrows.

I am so pleased with how my nose cone paint match came out that I decided to re-print all of my PLA parts in white and paint them as well. I originally didn't want to have to paint anything, but this is the compromise that's going to make my model look a whole lot better than it would have otherwise.
Aug 06, 2021, 12:37 PM
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For those of you who wonder if the Imperial System plays well with the Metric System, here's a couple of pictures of my 3/8" X 1/16" magnets (that I just got today) on the fuselage hatch. I think good ol' cereal box cardboard can come to the rescue if I need them to be more flush.
Aug 06, 2021, 02:43 PM
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tspeer's Avatar
The way I like to install magnets is to put a sheet of parchment paper between them and then glue them into both the fuselage and hatch simultaneously with epoxy, with the hatch taped in place. This allows the magnets to find the right position so they mate perfectly. The epoxy will fill any gaps and shim the magnets if the hole is deeper than the thickness of the magnet.
Latest blog entry: Radian Flight Test Project
Aug 06, 2021, 03:32 PM
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That's a great suggestion, Tom! Thanks very much!
Aug 06, 2021, 05:29 PM
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OK, here's something I want to discuss: the cure time of 30-minute epoxy. I just used Z-Poxy for the first time. Zap says their Z-Poxy 30-minute epoxy "does fully cure in 30 minutes." But every other brand of 30-minute epoxy that I've used says what the Internet says: handles in 8 hours, and is fully cured in 24 hours. What do the rest of you guys think?
Aug 07, 2021, 04:54 AM
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Hi I found that it is very brand-dependent (they do not have the same criteria to publish their numbers) but above all , like all these epoxy chemical reactions, they are all very temperature-dependent.
In summer at 80F/100F ambient temp, any of these will harden quicker by a noticeable factor than in winter (where it could easily take twice the time). Of course 'down under' things are the opposite.
All this to say, a brand mentionning a cure time but remaining vague about the temp (as in a 'simple sales pitch'), is only giving you one side of the problem...
For a quick fix that will allow you to fly the same day I would be looking at a shorter published time (like 5min or 15min ); however some 5mins brands are disappointing ; and the proper mixing of the batch becomes a time-trial challenge!
Else you could use 30min epoxy but bring some heat if you can (if you are not glueing PLA parts!).
Here the ZAP marketing department probably did their magic to the engineering wordings. If ZAP 30min says 'fully cure in 30 min' then it means you had much much less than this to assemble your parts - is it what you noticed ?

From a given epoxy batch, I always glue together two additional scrap wood sticks... I 'poke them' after a while , and I use them to convince myself that the bond has acquired adequate strength, therefore it is safe to handle the 'precious/airworthy parts'.
Aug 07, 2021, 06:25 AM
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Quote:
Originally Posted by nvd07
Here the ZAP marketing department probably did their magic to the engineering wordings. If ZAP 30min says 'fully cure in 30 min' then it means you had much much less than this to assemble your parts - is it what you noticed ?
Thanks for coming on, nvd07! Yes, you are right about having less time to assemble your parts. ZAP admits that themselves. They say that you really only have 15 minutes to get your parts together! So in my book that makes Z-Poxy 30-minute epoxy actually only 15-minute epoxy!

I decided to generate some empirical evidence to test what ZAP says about their cure time (at my expense, it turned out!). After 4 hours from application of glue, I pulled Fuz Hatch from Fuz 1, and, yep, one of the magnets came out! So can I say shame on you ZAP for fibbing?
Aug 07, 2021, 08:25 AM
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nvd07's Avatar
Ok I guess everytime you try a 'new' brand of adhesive/chemical you have to get used to the 'working time' and the 'fully cured' times.
In this specific case of the magnets: the material is not the easiest to bond adhesives onto it - I would not blame ZAP... Magnets were not so popular for canopies when I started RC 30 years ago. What I see is the pull is so strong when the gap with the mating magnet gets to zero, that they can come disbonded as you experienced, or I have heard that the airframe can get crushed too!!!
What I do is I apply a strip of clear adhesive tape, so that the gap never goes to zero - this way the pull is not overly strong...
Aug 07, 2021, 08:56 AM
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Quote:
Originally Posted by nvd07
What I do is I apply a strip of clear adhesive tape, so that the gap never goes to zero - this way the pull is not overly strong...
Thanks for that one, nvd07! That's exactly what I'll do, because these magnets are bonkers strong!
Aug 07, 2021, 10:05 AM
Tony Audsley Retired Locksmith
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Thread OP
I just use CA glue to glue the magnets in and haven't had any problems

Lockey
Aug 07, 2021, 12:23 PM
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Yeah, when I pulled the magnet out, I scraped the epoxy off the bottom of the magnet and the inside of the printed magnet holder, then put a big drop of thick CA into the holder, and used a cotton swab to brush on some kicker on the magnet bottom. Works fine. If I had to do it over again, I would have just CA-glued my non-flush magnets in place, and let the gap keep the magnets from touching each other.


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