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Old 12-02-2019, 02:44 PM
asw20c asw20c is offline
Join Date: Jun 2010
Location: Edgewood, NM
Posts: 194
Default 3M Tape

Over the Thanksgiving weekend I finally finished my (second set of) flaps. The first time I built them I used a technique used by Synergy Air when installing the trailing edge wedges; i.e. I used Aeropoxy to glue the wedges in place and a 2x2 aluminum angle match drilled and clecoed to the trailing edge to hold it straight while it cured. This works well but is almost as messy as using fuel tank sealant. Therefore this time around on my second set of flaps I opted to try the expensive 3M tape that Van's recommends for this step. I don't know about the rest of you, but I was disappointed in the results. Even though I used the same 2x2 angle clecoed in every hole in the trailing edge to hold everything straight while the tape adhesive "cured" overnight, as soon as I removed the clecoes and started the double-flush riveting there were whole sections that popped loose. To say the least, I was disappointed in the results.
Now in fairness, my shop was pretty cold and my attempts at heating it were short lived so I'm wondering if the cold might have prevented the adhesive from working as well as it should. Anyone have any insight into whether this might be the case? And if it is temperature sensitive, what should it be for successful use?
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Old 12-02-2019, 03:36 PM
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Ironflight Ironflight is offline
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I’d find the 3M part number for the tape, and go to their web site to look up the environmental parameters it is designed for. In my experience, 3M products are VERY well documented, and usually engineered such that they do exactly what they say - and not what they don’t...

If you used it within the designed temperature range, then I dont; know what to tell you.

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Old 12-02-2019, 03:42 PM
Bavafa Bavafa is offline
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Location: Sacramento, CA
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I used it for my trailing edge and it worked as advertised for me. I had used proseal for RV7 and the 3M tape was equally good but obviously less messy.
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Old 12-02-2019, 04:52 PM
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M McGraw M McGraw is offline
Join Date: Dec 2012
Location: Greenback, TN
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Default 3M Tape

I used the tape as detailed in the build instructions with very good results. At first, the tape seems to not stick well; however, if you cleco it in place and allow a bit of time it sticks very well and all my trailing edges are very straight.
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Old 12-02-2019, 04:53 PM
David Paule David Paule is offline
Join Date: Dec 2009
Location: Boulder, CO
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I have heard that it's a good idea to warm the assembled joint, including the support angle, with a heat gun and using a roller to put pressure on the tape. But I've never tried it myself.

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Old 12-03-2019, 06:31 AM
HFS HFS is offline
Join Date: Aug 2009
Location: Lemoore, CA
Posts: 277
Default Surface Preparation for 3M VHB Tape Applications

Do a Google (or other search engine) search for the above title and you will find the approved method for VHB tape application.

Of interest to note is the increase in bond strength over time, with the application of elevated temperature when joining the two surfaces.

I have used this product over 30 years, on all manner of aircraft applications, and have never had a failure - caveat, it needs to be applied correctly or all bets are off.

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Old 12-03-2019, 07:35 AM
RViator60 RViator60 is offline
Join Date: Nov 2019
Location: Southport, NC
Posts: 41

How did you prep the surfaces prior to applying the tape? I roughen each surface with medium grit sandpaper and then clean thoroughly with acetone. I found this leads to a very strong bond, probably more important than the ambient temperature.
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Old 12-03-2019, 08:27 AM
RyanS RyanS is offline
Join Date: Aug 2013
Location: Darwin, MN
Posts: 69

Please see the attached surface preparation bulletin and the bond build table on page 1. I don't know the temperature of your shop, but as an example: 50 deg F & 24 hours will only provide about 1/2 of the adhesive bond strength. You should really get it up to 70 deg F for 24 hours.

Also, scuffing with a maroon Scotchbright pad followed by cleaning with IPA/Water (50/50) will certainly help as well.

Last edited by RyanS : 12-03-2019 at 01:51 PM.
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Old 12-03-2019, 01:37 PM
asw20c asw20c is offline
Join Date: Jun 2010
Location: Edgewood, NM
Posts: 194

Well, that explains it then. My cleaning procedure was in accordance with 3M's surface prep instructions, but it was way too cold in my shop; certainly below freezing overnight, and only up into the 40's when I was working. Lesson learned.
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Old 12-05-2019, 02:31 PM
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kbalch kbalch is offline
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I used the specified 3M tape for all of my trailing edge wedges with excellent results. Given that the tape's purpose is simply as an alignment aid and is not meant to rigidly hold the wedge and skins, there's no need to resort to sealants.

Just do the proper surface prep, mind the shop temperature, and cleco the trailing edge through every hole. If you've done it right, there's no need to use an angle, either. Let it set overnight and then remove every other cleco. Rivet those holes, then remove the remaining clecos, and rivet the rest.

All of my trailing edges came out straight.

Personally, I miss the old bent trailing edges (easy to do and good-looking), but nobody asked me. :-)

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