I actually know quite a few geniuses. I'm going with the "technique" theory.
Brett
Hinge Sealing Follow-Up for non-geniuses with poor techniquesFirst, the good news – Using the Moore tape and Brett’s wedgie technique, I now have taped hinges as free (or 95% as free, subjectively) as the untaped hinges. Thanks a bunch!
The rest of the story: Critique this, please, as I’m still learning. To make sure I got the tape well down into the gap, I first stretched a loop of tape around to hold the controls full lock plus a little tension. The goal is the leave a hinge gap as large as possible – think “enthusiastic first-year gynecology student” when “prying” the gap open. The Moore tape is a little narrower than the advertised ¾” (more on that below) so I set up tape guides ¼” from the TE of the stab and wing to assure at least ¼” left to lap over to the movable surfaces (see pic). I prepped the surfaces with lacquer thinner followed by Prep-Sol. (The surfaces are all Monokote in this case)
The tape tends to grab on the movable surface when trying to push it into the gap. To help prevent that, I put a piece of waxed paper on the movable surface, pressed the tape into the gap on the fixed surface side with a credit card (ever wonder how we were able built models in the cash era?), and only then removed the waxed paper and wedged the tape down onto the movable surface side of the gap. That seems to work pretty well for unskilled labor. I did not tape across the hinges on this first attempt. With this “success” under my belt, I’ll do it right on the next two planes I have to do, with the beeswax lip balm on the hinges themselves, but not in the gap. As an aside, it does take 24 hours for acrylic adhesives to “cure”, so taping should be done a day or more in advance of flying.
I did do the beeswax down in the gap on the first flap segment, but decided it was too risky in terms of reliable adhesion (I had to re-clean around the gap as I smeared a little wax up on the surface). The rest of the segments on that wing and all the rest of the surfaces were done bare.
The “More Than You Wanted To Know” part: My first guess was that the Moore was a thin Taiwan OPP with acrylic adhesive, and was likely a 3M knock-off available under a variety of brand names. Actually, the Moore tape is Scapa 1250 (Swedish, but the 1250 is from the North American division), which
is available under that name (and probably some others, although I couldn’t find any others). All of the “Crystal Clear” or “Water Clear” tapes of any caliper are in the acrylic adhesive OPP category (I think).
On the theory that someone had an equivalent (3M surely has something in every market niche available), I had previously done some searching on the internet, telephone, and physical visits to craft / art / drafting supply / commercial big box sources to no avail.
After all that,
four feet from this computer, in the upper right hand drawer of my big, strong, handsome wife’s computer desk, I found a new roll of ¾” Scotch 3M “Transparent Tape” code 157s. It looked perfect to me. Back to the internet to get specs and compare to the published Moore specs. No luck. 3M seems to have a spec sheet on every tape they make – particularly the ones near our needs – the 600, 605, 610, 810, you name it. Nothing on 157s or a clue as to which “master film” is sliced down and packaged as 157s. A couple of calls to 3M customer service only proved how well-trained the reps are at keeping us riff-raff away from the folks there who actually know and do things. Their story, which I couldn’t get past, was that 157s was a unique product, the specs were proprietary, and that film / adhesive combo was in no other 3M products and was made in no other widths than ¾”. The reps said the 600 tape (2.4 mils) was the nearest equivalent. (I later found the same package advertised in ½” width.) Despite some flim-flam about being an ISO consultant needing written specs, I could not get past 3M customer service.
Left to my own devices, I did some measuring and calculating. The spec for Scapa 1250 caliper is 1.9 mils. With a .001 mike, measuring that is like using bathroom scales to calculate grams of tip weight. I miked the roll (actual mike of total thickness of tape on the roll vs a check of core OD vs tape OD). Calculating the expected spiral thickness based on Scapa specs, it came out no thicker than advertised. For both the Scotch and the Moore, I used the advertised length as a hard number for the calculations. Reason is, in the consumer product world, the guy with his thumb on the volume knob has the quality / FTC flavored guy twisting his arm one way, and the bean counters twisting the other way, so consumer quantities are pretty reliable in the U. S. across the board – not much over, and no under (at least statistically 95% confidence level).
I was a little concerned about how the 1.9 mil spec was calculated – compressed, as wound on the roll and as applied; or “fluffy”, as it came off the machine before winding. That could be a big difference – sort of like a 5’ 9” guy with a 4” Mohawk hair cut claiming to be 6’ 1”.
With a
sample size of one on both the Moore / Scapa and the Scotch 157s., the Scotch appears at least as thin, and possibly a little thinner. The actual numbers I got were 1.86 mils for Moore vs 1.77 mils for the Scotch. I wouldn’t bet the farm (with my methodology) the Scotch is thinner, but I can say with some confidence that the 3M is not any thicker (for our purposes) than the Moore. That is, I wouldn’t claim a solid (rounded) two digit accuracy.
The Moore width was a minor bummer. In the tape world, ¾ is sometimes 19 mm. OK, but the Moore was .698 to .700 (soft edges, you know). That is less than 18 mm!
I don’t know about adhesion differences, and I don’t know about stiffness differences. That is, thicker is stiffer all else being equal, but I don’t have a Gurley or equivalent tester available; I don’t have a breakdown (on these two specific tapes) as to how much of the spec mils is adhesive and how much is carrier; I don’t really know which one is thinner for sure. I don’t know if stiffness we feel is more dependent on film or adhesive characteristics / thickness anyway.
From the data I have and feeling the tapes I would say they are equally flexible for our purposes. I am going to try the 3M 157s on the next plane, and will report any issues I find.
Larry Fulwider