Ed - thanks for those kind comments, your words make my day!
Couldn't sleep so I got up to finish this chain of posts...
PART 4.... CONTINUED....
So... that Monday morning I brought the newly painted door back to the hangar. What I failed to mention to this point is that between delivering the door to Royal Aircraft @ HGR on Saturday morning and picking it up / finishing it Monday morning I continued work on the door jam of the airframe back at the hangar.
I spent the rest of Saturday prepping for paint (as most of you know paintwork is at least 95% prep and 5% actual painting). It took some time to cut a plastic liner to fill the door opening and carefully tape it in place. Then there was masking off the outside of the door jam... lots of masking and plastic drop cloths to paint just a 1cm wide door jam! We use a very low pressure "turbine" paint gun for spraying the Imron which my painter friend says is 98% efficient (less than 2% overspray). But we also put drop clothes over a lot of the hangar floor and other aircraft as a precaution.
One thing I found when I removed the old seal / weather stripping from the airframe side (which should never have been there) is that underneath, right by the receiver hole where the pin goes in at the upper leading edge of the door, there was some damage. Minor (and rather odd) but something to be dealt with. Here's a pic of the receiver hole and just above it you can see there is (was) some silicone sealant there:
- Receiver Hole for Door Pin
Once I removed all the silicone (paint won't stick to silicone), it was more clear. here's another pic from the top:
- Receiver Hole Damage (top view)
I pondered how that could have happened at some point in the aircraft's life. Best I can figure, at some point the pin did not line up (when new the pin is rather pointy) and perhaps the door was closed and the pin did that. At any rate, I never knew it was there because the old door seal on the airframe covered it (and again there should be no seal on the airframe side anyway). So... after cleaning it up and prepping it we drill stopped the small cracks in the rain channel of the door jam that you can see in the pic above. I say "rain channel" because it looks to me that this part of the door basically consists of a U-shaped channel that a) serves to direct any moisture around the outside of the door frame and b) provides a somewhat sharp edge for the seal on the door to mate up to (more on that with later pics).
After drill stop we felt the best way to repair this was with PRC sealant which is water tight and paintable. The damage area was quite small (the pics above actually look worse to me than it did in person) but I wanted to ensure that water could not get in. We mixed some PRC and used it to fill the hole and then "smooth out "the rain channel (as I'm calling it). This part had actually been done the week prior I should have mentioned this in post 1 or 2 above...
After all the prepping of the door jam that Saturday I primed it with zinc chromate. I've used the Dupont Imron primer as well but in talking to the paint shop it's hard to beat the durability and protection of good old zinc chromate
. Just be sure to wear a respirator - there's a reason the EPA and OSHA no longer have paint shops using that stuff...
By that Sunday morning (before Thanksgiving and the day before I picked the door up from HGR), we painted the door jam and I was quite happy with the results:
- Painting Door Jam
Fast forward one day (back to Monday), I brought the door back to the hangar hoping to mount it. Unfortunately the paint on the door jam from the afternoon before was still not hardened. It was dry (Imron dries in about 2hrs with the proper ratio of hardener) but dry is a relative term. The door jam paint still seemed soft, almost tacky. Imron likes about 70F to cure and on the weekend we drop the hangar temp to 55F. I couldn't justify keeping 22,000 sq-ft of hangar 15F warmer all weekend just for the door jam so I put a portable heater warming the air by the door opening.
Nevertheless, the door jam was still not cured enough by Monday to be pressing the firm new seal into. It was a surprisingly warm day with a nice breeze (it actually got up to 70F that day and it was now warmer outside than in the hangar!) So I pulled the plane out in the sun to bake for a few hours...
- Baking in the Sun
By Monday evening in spite of baking in the sun and keeping the heater on it in the hangar, we still felt the paint was a tad too fresh to mount the door. I forgot to mention that in that small door jam we actually had two colors to deal with and repaint - the white and the tan underneath. With two colors and time in-between that exacerbated the timing problem. So we decided we would need to mount the door the next morning (Tuesday).
My stress level began to go up a bit when I looked at the weather forecast. Or plan was to depart on our Thanksgiving trip that Wednesday and we still had a day to go right? Problem was the forecast for Wednesday, now jut 1.5 days away was pretty terrible. You may recall the news reports of what a terrible travel day the day before Thanksgiving turned into on the East Coast and in the Mid-Atlantic area (my base at HEF is just outside Washington DC). I told my wife we would either need to leave tomorrow (Tuesday - same day we planned to mount the door) or wait until Thanksgiving day - Thursday and hope the inclement weather did not intrude into the holiday. We agreed we should try and make Tuesday happen if we could.
The next morning, I got my things together, took care of the family pets and off to the airport I went. My IA (and DOM of my charter operation) messaged to say the paint was in fact fully cured on the door jam - yeah! So we were going to make it right? What else could possibly go wrong? I mean after all what was supposed to be a simple 2-day max door seal project had now stretched to 3 weeks and a lot of work which we started WELL before the holiday, and I'd promised my wife I'd started that far in advance to be CERTAIN the plane would be ready for our Thanksgiving trip... So surely the final door mounting would be a snap
Actually putting the door on with the new Stainless Steel Clevis pins WAS a snap. They made it very easy to put on and off - even one person can do the task but it's a little easier with two. It was looking good with the new door on (glare shield off in this pic as we were doing other stuff - another topic for another post):
- Door Back On
Now here's the part where I need to comment on the "service manual procedure" vs "practical or real world procedures"... I've run into this before - including on the landing gear project earlier this year. The service manual calls for rigging and fitting the door WITHOUT the seal in place. This is important because the seal puts pressure that moves the door around into other positions and there is plenty of "play" in a lot of things on these old airplanes - even brand new. For instance the amount of play for movement in door hinges (or even the gear door hinges for that matter). Even a few millimeters of movement back and forth at the trailing edge of the door can make a difference. I actually had a fairly tight fitting door - not a lot of play really, nice new hinge and new pins - perfect.
The door rigging process involves trial and error; mounting the door and then adjusting the hinges and remounting the door to get a flush and even fit all the way around the door and airframe. On the airframe part of the hinge (tabs that stick out of the airframe to make the middle of the hinge) there are little inserts that look like a little gear. The teeth of the gear mate up to teeth on the tab. On the inside of the little gear is the hole for the hinge pin (where I am now using the clevis pin). The hinge pin hole is slightly off center by design. The idea is you can pop the little "gear" up and out of the hinge tab and move it's position clockwise / counter-clockwise to change the relative position of the hinge pin hole thereby adjusting how the door fits. So for each hinge you can move the position in or out but in the process you are also moving it forward or backward. It's part science and part art form...
So... we did all this door rigging prior to the door going off for paint and seal installation. We had a very good flush, even fit. However... now that the new seal was on it did not seem to fit as well at all. I'd been warned by Brown Aircraft Supply (seal supplier) and Webco and others that when first closing the door with a new seal you will be absolutely convinced you've got the wrong seal. It takes quite a bit of effort to close the door and compress the seal and the trick is to close it, leave the seal compressed for 24hrs so it sets up a "memory" of it's new shape and fitment to the airframe. At any rate this is where "book" and "real world" procedures collied because with the door perfectly rigged without the seal it just wasn't at all right with the seal. We had to make a very minor adjustment to the door rig to get the right fitment with the seal. It was indeed a very minor adjustment but an important one. I still think it's valuable and important that we rigged the door first without the seal but the reality is a small tweak was still needed after the fact.
One other important tip I learned from the "seal guy" at Royal Aircraft that no one else told me... when first closing the door with the new seal it's important to put a generous coating of DC4 on the seal. That way the seal is lubricated and can move against the door jam and find it's "seat" without tearing against the sharp edge of what I am calling the "rain channel". For those not familiar; "DC4" is Dow Corning #4. It's a silicone based grease used on a lot of aircraft applications. For instance we use it to lubricate rubber O-Rings and the like (such as on new oil filters before install). In lubricating the seal I took great care to not get any on the acrylic windows since DC4 is silicone based and silicone will craze acrylic windows:
- DC4 on Seal
So all this door re-rigging took some time, and our afternoon departure target time was quickly approaching. With my IA "Joe" outside and me inside the cabin we carefully closed the door and once we had the door rig "tweaked" and were happy with it we fully closed it and I latched the door handle from the inside. I should mention that this took several attempts and we decided to lessen the strain on the door by moving the adjustable striker plate on the upper trailing edge of the door jam out slightly. This left the trailing edge of the door a few millimeters out and not perfectly flush but the idea is this is temporary just until the seal is more compressed and then we will move it back for a flush fit...
So we got the door closed... then I went to open it and it wouldn't budge. I never try to force things. Our planes are pretty sturdily built and tough as far as the airframe goes but there are plenty of bits and pieces that are delicate. The door had taken more than normal effort to close with the new seal mostly pushing / pulling inward but also in closing the door handle. In attempting to open the door I pushed slightly down on the handle to relieve pressure, pulled up on the little lock pin (an normal) and tried to open the door. The handle just didn't want to move.
After about 10min I thought I was going to climb out the baggage door to take a look from the outside but then one more attempt with just a little more pressure (not a lot just a little more) and... it happened.... The door handle moved but the door did not open. The inside splines of the door handle had stripped and the handle was now useless. As I moved it back and forth I could feel it go "thump-thump-thump" as the stripped splines of the handle bumped over the mating still good splines of the door mechanism. Playing around a few minutes more, with Joe leaning in on the door we were quite miraculously able to get the door open. At this point I'm not sure exactly how we did that. At any rate I can attest to what others have said... new door seals are tight!
In retrospect this door handle (that I'd just stripped) was on borrowed time to begin with. Looking at the inside of the handle 1/2 the splines were missing in the first place - clearly long gone. This was just the preverbal "straw that broke the camel's back" and the few good splines I had finally let go. Better to find out now than in an emergency evacuation situation but this was not good news. Now less than an hour from our desired departure time that afternoon, I had to call my wife and tell her; "Houston we have a problem..."
END PART 4.... TO BE CONTINUED...