Monday, July 10, 2017

3M 90 Spray Adhesive on Estes Vacuform Wraps? TIP

From a Model Rocketry Fanatics Facebook Post by Justin Farley:

Justin Farley: "FYI: 3M 90 spray adhesive works great at melting vacuform wraps if that is your desired goal. It is pretty bad all the way around, fortunately the really Freddy Krugered part will be on side with launch lugs. It still looks bad, this build was going too smoothly."

Lee Reep: "There is a build thread on TRF on the new Estes Little Joe II that shows using 3M 90. James Duffy points out it goes on like a spidery web. By any chance did you put it on and try to get a uniform (and therefore heavy) coat of adhesive?"

Justin Farley: "Perhaps it is that Estes is using ABS instead of polystyrene now, but I think I probably applied way too much. Which is easy to do given how it comes out in a stream as opposed to a mist like the 77 does." 

My take: There are three different strengths of 3M Spray Adhesives. 
"45" Economy Grade, bonds paper, cardboard, photos.
"77" Medium Grade, dries quick and clear, Bonds to foil, paper, cardboard, fabric, plastic, metal and more.
"90" Industrial Strength, bonds laminates, kick plates, poly and plastic lettering.

The vacu-form wraps used on the Saturn V kit feel different than the wraps from the Little Joe II. Estes doesn't go into enough detail as to which plastic adhesives to use in their kits.
For the vacuform wraps I have had very good results using the 3M Super 77. I felt the 90 adhesive might be more strength than might be needed. Some have had good results using it, but you don't want to apply too much! Practice on edge scraps, never on the final kit build parts.
Some areas on vacuform parts are thinner than others. The solvent in the 3M 90 may have melted those thinner areas.
Don't use tube cement to glue any of the Little Joe II plastic parts together (capsule, tower and details). Plastic model cement is not what it used to be. I used Plastruct Plastic Weld with very good results.

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