Friday, February 26, 2016

A Rethink On the Raptor Nails

A long time ago I was flying a rented airplane (Cessna 172) from a small airport north of Toronto.  It was wintertime and the runway was icy.  I was coming back to the airport and on final approach.  I was high, and a little fast and  in fact I knew that before I even set up for the landing. I should have gone around.  I didn't.

On short final, I was definitely high and fast.  I really should have hit the throttle and gone around.  I didn't.

My usual greaser landing where you could not tell when the wheels touched down was very, very greasy.  The brakes had no effect of course and I was not high anymore of course but way too fast.  I ran out of runway.

I did not damage the aircraft.  It did stop after plowing through ten or fifteen yards of foot deep snow and everyone at the flying club was able to help me push it free.  I never went back there.  But I learned a very valuable lesson and that was not to press on with something if your intuition tells you not to.

So that is why I will not use Raptor nails to laminate the plywood.  I think that they are great but not for this application.  I will use them for sure when I do my interior joinery.

What I found was that they would let go enough to open a glue joint if under stress.  Not much but some.  What I was doing was putting in a screw when I could see the ply needed to go down a bit more....especially evident on my curved strips.  I'd fire a couple of nails beside the screw and then remove it.  I could see the ply flex a tiny bit when I did that.  It did not sit right with me so I put the screw back in.

Once the glue set up I have wound up with very tight joints using screws.  I have not left the screws in however (epoxy coated deck screws).  The first layer that is glued with PL Premium is screwed with permanent screws but the subsequent layers will have no fasteners...yet.

So here is what I am doing now.  The second and third layers are being glued and screwed very carefully.  Even on the flat sections I am using ply panels no more than 2 feet by 8 feet.  I KNOW that they are laying flat and especially with a lot of screws.  They come out a day later.

Once both layers are on I will nail the hell out of it capturing all three layers with bronze ring nails.  Better safe than sorry.

1 comment:

  1. Finally getting back to this post to say that I think it was a good decision for wise reasons.


    “It is admitted that he did sincerely believe in the soundness of his ship; but the sincerity of his conviction can in nowise help him, because he had no right to believe on such evidence as was before him. ... He had acquired his belief not by honestly earning it in patient investigation, but by stifling his doubts...”

    -- From The Ethics of Belief by William K. Clifford