For spraying I use about a one second burst for each wing spar and each end rib. This is done with a similar technique to spray painting where your hand is moving before and after the spray head is pressed. I normally don't glue the intermediate ribs to the covering so they are masked off with paper or masking tape.
There are other ways of applying 3M77. One is to spray the adhesive in the air and wave the outline through the cloud to pick up adhesive. Another is to put the outline on the floor (supported by folded paper or similar means) and spray a cloud of adhesive over the outline. I just hold the outline in the air by one spar and spray the other spar and then reverse and repeat.
For Mark's method there is so little 3M77 in the mixture that not much remains after the naphtha evaporates. Also, my understanding of the method is that you apply the mixture a little outside of the outline so that not much of it actually runs into the joint. When I get done I look at the glued outline carefully to make sure that the shiny glue left on the film actually touches the outline. If there are any questionable spots I apply more of the solution. You can also poke at the film (gently) with a piece of balsa to make sure it's attached.
Another variation is to use the spray method and then use solvent to make any necessary adjustments to the film. Another is to spray or paint the adhesive onto the outline and let it dry completely, then position the outline on the film and reactivate the adhesive with solvent. There are probably as many variations as there are people building indoor models.
Mark has given me more detail about how to adjust the mixture but I'll leave that to him to explain. You can always check the results of whatever method you use by careful weighing before and after covering.
----- Original Message -----
From: ykleetx
To: Indoor_Construction_at_yahoogroups.com
Sent: Thursday, April 01, 2010 7:49 PM
Subject: [Indoor_Construction] Re: New LPP
I've read Mark's article before and have used his 3M77 and naptha mixture to reattach loose film to the wing spar. But I did not appreciate it fully! (He should attach a photo of his covered wing.) I've also used your method to tighten up film at the dihedral joint.
On "applying" adhesive to the film and relying on the wicking action of wood/film, how do you avoid applying too much adhesive? (I was thinking that most of the mixture evaporates.) When using the "spray" method, I am always paranoid about applying too much.
-Kang
Received on Thu Apr 01 2010 - 19:05:53 CEST
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