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 Comet "Phantom Fury" Construction Project Session #14

Comet "Phantom Fury" Rubber Powered
Free Flight Model Airplane

By Tommy Gray
AMA 17063

As the plane was pretty well done as of the last session, all that was left was to make the rubber motors, and tidy up a few small details.  A couple of days ago, the rubber and crocket hooks I ordered from FAI Model Supply arrived.  I had ordered a box of Tan Super Sport rubber in the 1/8" size.  As you can see in the picture below, when it comes you have a box with a "pile" of rubber inside!!

Here is a close up of the box


Now friends, that is a LOT of rubber!  Keep in mind that it is one long continuous piece!

I made up a winding "jig" by taking a scrap of plywood and drilling two holes in it for some dowel cutoff pegs.  In the picture below you can see what I mean  I first put the pegs 20" apart, but later changed it to 30" as I will explain later.


I first wound a long strand of the rubber around the pegs, counting the loops.  The O'Reilly plans said to use "10 strands of 1/8" FAI rubber, 20" long" for the motor.  I then wound 5 loops of rubber on the board, between the pegs.  Later in the day, I got a call from Jim O'Reilly about some SAM business and while I had him on the phone I interrogated him about the motor as it looked awfully long to me, since the distance between the motor peg and the prop hook is only 13 1/2".  He was a little unsure as it had been a long time since he had done the plans, so after a brief discussion I decided with his input to make shorter motors, and to go to 12 strands instead of 10, so the motor could be braided (I will explain this and show you how in a later session).

The next day, the motor thing still bothered me. I was unsure what to do, and if you know me, you know that  I can't stand that and have to get to the bottom of things before I continue.

So....I called friend and fellow SAM'er Gene Wallock who is another one of the "Gurus" of rubber flight we are blessed with in SAM.  Gene told me that he was going to use 8 strands of rubber, but he also told me that his prop was only 8" long.  Well, mine is 10 1/2 so I am with Jim on the extra strands.  Gene suggested that I make the motor long enough to braid, and add 2-3 inches for a starting point.  So, since it is 13 1/2" from the peg to the prop hook, I moved the pegs on the board out to 30" which is 2 X 13.5" + 3".  I changed the spacing of the pegs to 30" and then made up a couple of motors with 6 loops each.   When folded and braided, this will yield a 12-strand 15" long braided motor for the little plane.  I am going to give it a try and see how I come out.

I tied the ends of the rubber with a square knot, and before tying, I put some saliva (Yeah...spit!!) so that the rubber could slide enough to tighten properly.  I dried it off and then put a spot of CA glue on the knot to secure it.

In the next session I will show you more of what I did with the motor after I had it made up.

More to come....Tommy

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