Cozy
Chapter 25 - Finishing - Preparation and Initial Prime
Good advice
Long after I was done with the finishing, George Sychrovsky gave a very good dissertationabout finishing on the Canard forumI added a few extra comments, but George's description of the process is a very good place to start. I wish he written it 2 years ago.
Materials
Polyfiber put out an excellent [free] booklet on composite finishing. I picked this up at Sun & Fun and saw a demo at their booth.
It looked good so I ordered a small Superfil kit from Wicks and experimented on the fuselage bottom. The trick is to add a very fine coat - just enough to fill the ridges, not cover the fibers. The stuff is so light I keep thinking the jar is empty when I pick it up. I find that it can be so dry that it tends to pull off the part as you run the squeegee over it, especially if it has been applied a few minutes and is then "reworked". I've found two solutions to this. One is to keep the Superfil in my epoxy hotbox. It sticks much better when warm. A second trick I've used is to mix a tiny amount of my MGS epoxy (like maybe 2% by volume) with the superfil. The Superfil goes a long way if all you're doing is filling the weave. I experimented with a level teaspoonful of mixed Superfil. It covered an area of 36 square inches on the side of my fuselage. I visited Jeff Russell (AeroCad) while he was finishing an AeroCanard. Learned a lot. Following his suggestion, I used micro as the primary filler, Superfil for minor imperfections and cabosil for final touches. Later I had a lump of superfil left over, so I rolled it into a ball and let it set. I did the same with a lump of dry micro and did a simple weight for volume experiment using displacement in a cup of water and a postal scale. Despite all Superfil's claims of lightness, I found micro to be approximately 50% lighter by volume. I ran out of Superfil fairly early on, and just continued with micro. I found that I'd become quite good at working the stuff. I liked the consistant white color. Green Superfil patches can be distracting and make it difficult to see the shape. I didn't bother ordering more Superfil until [what I thought was] the very end of the process.
A visit to the auto paint supplies store
I'd been intending to visit the local auto paint supply store all along. When I was nearly done with the bottom of the plane I decided it was time to buy a spray gun so I looked them up in yellow pages and, finally, paid a visit. I bought a gravity feed gun, some zolotone, zolotone clear coat and a hand sanding tool. I'd been using an old hand sander which had broken clips, so I'd been using spray adhesive to stick the wrong size paper after cutting it with a knife. The auto paint store sells rolls of sand paper. Why didnt I do this before? The 120 grit stuff will take rough cured micro down to a perfect finish in no time. I would have saved quite a bit of time and frustration if I'd bought this tool 6 months ago.
Filling and Sanding the top.
Once I'd completed the strakes I began filling and sanding to get the top of the plane ready for primer. Jeff Russell's recommended technique is to put a gallon of epoxy plus hardener in a 5 gallon bucket, add 5 bags of micro mix with a drill mixer, then spread the whole lot. I decided I wasn't ready for such a drastic approach, so I mixed about 6 to 8 oz of micro at a time. One of Jeff's reasons for doing the micro all in one go is to avoid "edges" between different applications of micro. Maybe the MGS epoxy works differently to the EZpoxy Jeff uses, but I didn't have any problem with edges. Some areas got 4 or 5 seperate applications of micro. I did a "rough cut" with 33 grit, then a final sand with 120 grit on each application. The joins simply disappeared. After I'd got the shape, I found I could spread the micro VERY thin - so thin as to be transparant in places - by applying LOTS of pressure and running a sheetrock mud trowel across the surface while holding it almost vertical.
I even broke one (Bills favorite) trowel that way, but the end result was good (IMHO). I should, probably, have put more micro on, then sanded it off. Instead I tried to apply micro only where it was needed. A little bit here, a bit more over there. I may have saved a bit on sanding, but I caused myself more trouble by having different surfaces. The 33 grit bites nicely on micro, but slips on glass. After each sanding session I washed the plane down and inspected it while the surface was wet and shiny. I'd mark any areas needing attention, then start over. It got a bit tedious after a couple of weeks, but then I visited Bulent's project. Seeing his project almost complete, but with no finishing done at all, made me realize how much I'd achieved and renewed my motivation.
There were only two areas where contouring was needed - where the main spar joins the strakes and the leading edge of the right strake. [note - Later I found a few spots along the bottom curve of the nose and fuselage sides which needed a touch more roundness]. If you read my Chaper 21 you might remember that my good friend, Bulent, came over and "helped" me with fairing the strake skins. I would never have got myself in this mess in the first place if I'd bothered to check the alignment of strake leading edges to wing join point properly. Anyway, trying to correct the problem by sanding the foam produced a net result that the leading edge of my right strake was "flat" compared to the left one.
Using blue foam I made a template to give me the shape of the left strake at right angles to the leading edge. When I ran this template down the right strake I had a gap which got larger at the outboard end. I mixed about 8oz of micro and used the foam template to spread it along the leading edge to get the shape. I then smoothed the micro out with a sheetrock mud trowel, checked the shape again with the foam template and left it to cure. The micro is a bit thick in this one area, but no one will ever know unless Wayne sticks a yellow sticky there or the entire leading edge falls off in one lump. If the former happens, I'll get him back. If I loose the leading edge - I'll land, pick it up and stick it back on. Seriously - I guess the micro gets to about 3/16 thick at one point, but I doubt it will cause a problem.
Smooth Prime
I got the Smooth Prime primer from Polyfiber also. You roll it on with a special roller. They say you can spray it, but you won't get a better finish. They have discontinued their UV 'silver coat' process and now add the UV protection to the basic primer.
After I'd spent about two weeks preparing the top surface of the wings & strakes, the winglets, rudders, ailerons, fuselage sides, nose, gear legs and covers it was finally time to try out the Smooth Prime. I decided to mix
up 1/2 a gallon to see how far it went. Six hours later I was on my third coat and couldn't seem to get rid of the remaining paint! The stuff rolls on beautifully and covers a multitude of sins. 50 grit scratches simply
disappeared. (36 grit ones I can still see, but at least they now show up and are easy to fill). One dip of the roller gives enough paint to cover 1/3 of the wing surface. Many small imperfections disappeared but it was a
fair trade off, these were exchanged for quite a few ridges, dips and bumps I hadn't seen - now quite visible and easy to zero in on. Don't waste you're time going down to 320 grit on the superfil and micro! Get the shape right, spline sand up to 50 grit, maybe 120, then just prime it and fix what's left.
Regarding pinholes - I'd heard and read horror stories about pinhole chasing. I painted the wings, strakes and winglets and didn't see a pinhole. Not a one. Finally, when I got to the fuselage sides, (my early work done
without 4ml plastic) I saw my first set of pinholes as the paint rolled over one area. Ah - that's what they look like! I saw them for, perhaps, 15 seconds - then the smooth prime filled them up on the first coat. There
were no pinholes anywhere when I did the second coat. The smooth prime even filled up the holes in my static port. It went deep and I had to drill it out.
I know they say 24 hrs, but after 6 hours at 72 degrees the smooth prime was ready for sanding. It sands like a dream with 320 grit. I love this stuff.
Considering this is stage one of a many stage process I'm VERY pleased, as you can probably tell. I highly recommend Smooth Prime. (but then - I've never used any of its competitors).
Cabosil
Per the Polyfiber booklet (if you dont have one, get one - its the best written instruction manual I've ever seen) I dry sanded the primer with 320 grit. I tried Jeff Russell's method of dusting a little colored aerosol paint over the wing, then sanding. The dips show up as dark spots. I didn't like this method. I can feel the dips because they don't get sanded and are still a little rough, and I'm a little worried about leaving that aerosol paint on the part. Once the sanding was done I could see numerous spots that needed touch up. These ranged from the inboard leading edge of the left strake, which was a bit out of shape, thru areas where a reinforcing layup was still causing a bump, to scratches and small dips. I decided to try the cabosil I saw Jeff using. Interesting stuff. It mixes up a little like flox, but with a smooth consistancy. Its best applied with a flexible plastic scraper like those you get from automotive stores for bondo. Using cabosil you can fill the tinniest scratch, but beware - the stuff sands like steel. If you put it on too thick you have to work like crazy to get it flat. This stuff is excellent for tiny imperfections where you scrape it on and then scrape it off again, leaving cabosil just in the scratch. It dries to a shine and is very hard and smooth. Don't try to use it to fill anything big. After a few experiments I reverted to dry micro for minor imperfections. (I would have preferred to use Superfil here because it's smoother to apply, but I was out of it). In warm weather, mixed to right peanut butter consistancy, I was able to do very fine fill using micro.
Filling and Sanding the bottom
After about another week of sanding and minor filling I decided that the top was "almost" ready for the second coat of primer. I'd already recut the joins between the wings and strakes, so now it was time to flip the bird (again) and finish the bottom. I took the wings off and put one on my bench for primary finishing. First a few minor repairs were needed. I'd sanded the trailing edge a little too much near the ailerons, and an inch of the trailing edge on the left wing had been damaged by rubbing against my steel patio roof support. No problem. A little 2 bid tape fixed these areas easily.
The next problem was that the cut I'd made between the end of the strake and the right (Char's) wing was a "bit off". I had a nice right angle on my side, but on the right side the angle was more like 95 degrees and the forward end of the cut was about 1/4 too far outboard. I don't suppose it would have mattered aerodynamically, and no-one (except Hicks) would have noticed it - but it was going to bother me so I decided to fix it anyway. I bondoed a backing of 1/16 plywood covered with duct tape to the wing and added 2 ply BID around the inside to extend the rib on the wing. Then I sanded the strake back to a right angle. I hope my modification fits when I come to put the wing back on. Another problem I discovered was that when I glassed the bottom of the strakes, I hadn't glassed over the join between the wing and spar as I had with all the other joins. Now I'll have to put the wings on upside down to tape and recut this join. That should be fun!
Inverted flight
Installing the wing upside down wasn't so bad. I put some 2 * 4's on top of the trestle on one side to angle the fuselage and allow the wing to go on without resting on the winglet tip. It took four of us to lift and position everything, but we had one wing on in about 1/2 hour. I two BID taped the join between the strake and wing and finished this area to get a nice smooth continuous surface on the strake, wing and spar. After cure I cut the wing off again using a handheld hacksaw blade against a straight edge. I've been working on the other wing on the bench, but now I need to attach it. I've measured everything, and I think the plane will fit on the bench, upside down with both wings attached. This might make getting in the hot tub a little tricky for a while, or even the back yard for that matter, but it will certainly be an interesting sight, and the rest of the bottom finishing and primer will be much easier that way.
Inverted flight - both wings
We manouvered and raised the plane so that the other wing would fit on using trestles instead of the bench. It was interesting to note that, with the trestles in the middle of the strake there was no weight on the nose at all. We had to move the trestles back to the spar area before the nose would come down on its support. It was also interesting to see the whole plane inverted. Anyone leaving the kitchen for the back yard now has to duck under the plane to get there. (Jason is standing in the kitchen dor in the above picture). The dogs just trot happily underneath. I discovered a problem with my reengineered wing to strake join. The original cut wasn't at 90 degrees, so I'd had to add a bit to the wing and take a bit off the strake to get it right.
What I hadn't thought of was the angles. The angle of the strake is much greater than that of the wing, so my new join was about 3/16 out. This needed a little "reengineering" too, but in the end I got everything lined up nicely.
One item I never did find in the plans is a description of how to fill / cover the wing attach holes in the spar and wing. For the circular hole I used the piece of fuselage I'd cut out for the landing lights. I made a small lip around the hole with my dremel, then cut out a circular piece of cured glass / foam / glass sandwich and floxed a strip of cured 2 ply BID to the bottom to act as a retaining spring. To install the plug I bend the epoxy strip until it fits inside the hole, then push the plug down. Once it's in place the strip of epoxy springs straight and holds the plug in. Removal is simple. I prise the plug out with a knife blade. For the oblong holes I made another lip, cut a 2 ply BID cover to fit and floxed a wire hook and some foam to the underside. The hook will be attached to a spring connected to the same cover on top. The foam fits just right inside the hole to orient the cover. When finishing this area, I installed the plugs and just microed right over them. After cure I carefully cut the plugs back out with a hacksaw.
I used a similar technique for the landing gear cover and landing brake. First I duct taped the inside lips, then I microed the covers in place. After cure a nice straight cut was easy with a handheld hacksaw blade.
The canard
It was time to finish the bottom of the canard. I tried to remove the elevator pin, but couldn't get it out no matter what I did. I'd already loosened the set screw and the pin would turn a little bit, but just WOULD not come out. I tried all sorts of tools and removed (read gouged) some glass and foam so I could get a good grip on the pin. Still nothing. Hmmm. After about 1/2 hour of tugging and hammering I thought about the set screw again, then I remembered how it works - it goes past an indentation in the pin. All I'd done was loosen it. I took the set screw all the way out and, bingo, the elevator pin came out easily. Duh! For those who worry about the elevator pin coming out in flight - forget it. There's no way that sucker is coming out unless you remove the set screw. Think of this as an unplanned test to destruction. Once the elevator was off I inspected the brass hinge inserts. As expected, three of them had disintegrated during the last assembly of the elevator. I'd known there was a problem here and had ordered a replacement set of inserts for the occasion. I'll use these when I reassemble after painting. The other adjustment I needed to make was to sand the lip above the elevator a little to increase the clearance and permit a few more degrees of down travel. Finishing the bottom of the canard was no problem, even around the antennae which I'd added on top of the skin. (because I'd forgotten to install it below the skin). I'd arranged the antennae so that the torroids were in the center span which doesn't get finished, so the only part in the visible area of the canard was the foil tape.
Top Gloss
Mike Bowden kindly sent me the grey, red and white Top Gloss paint he had left when he abandoned it in favor of a different paint system. Mike was very unhappy with the results. I plan to paint the canard and control surfaces with the stuff and see how it goes.
Finishing the top
Once the canopy, canopy deck, canard cover, cowling lips and upper strake fairings were done in June '00, I came back to the world of micro, sand, micro, sand, sand, sand. There are lots of "fiddly bits" involved with finishing the top, and its all very visible, so this is going to take a while.
Last night I went to bed not sure if I'd created a disaster, or invented a
really cool solution. It turned out that I'd invented what, IMHO, is a
really cool solution, so I thought I'd announce it.
I got to the part where you need to finish the joins around the fuselage
windows and the back edge of the canopy. The acrylic is indented about 1/16
inch in from the surrounding glass, so its hard to get a good straight edge.
The black electrical tape used to mask the acrylic is too thin. After
searching around, I came across the P shaped weather strip I'd bought to
seal the canopy. With some trepidation about damaging the acrylic, I used
the weather strip to "mask" the window with the top of the P away from the
edge. The rubber strip bends nicely around the corners and sticks easily to
the acrylic. The edge is just the right thickness to lie flush with the
glass when stuck to the acrylic. What worried me was the adhesive used on
the weather strip is VERY strong. This morning I removed the weather strip
and bingo! A perfect flush edge to the micro. I'd read in the archives that
a little gasoline is good to clean adhesive off the acrylic. It's true. The
nasty sticky left overs came off with a wipe. Finally I stuck some felt on a
small wood sanding block to protect the acrylic and chamfered the edge. A
beautiful finish, if I say so myself!
The nose and other fiddly bits
I'd done my nose in Chapter 13. Once the canopy deck and canard cover were done I found that the top of the nose gear cover was a little low. I added about 1/4 inch of micro on the canard cover and nose gear cover to get a smooth, almost flat curve. The operative word here is "almost". I didnt want much curvature here, but flat just looks wrong. 1/4 inch of curvature from the lip of the canopy to the bottom of the nose gear cover looks (to my eye) perfect. I spent a few days cleaning up the edges - there are a lot of edges. The canopy lips front and back, the hinges, the fuselage top edges, canard cover edges and the nose gear door edges are now all the same. I had a bit of trouble with the rear canopy lip. The depression I'd made in the turtleback somehow seemed to disappear, so I had build a lip with micro. This worked fine, but I ended up with a space under the lip when the canopy closed. I could press the lip inwards and flex it. This didn't seem right, so I taped the fixed lip, added dry micro on top of the tape and shut the canopy down hard. After cure the micro formed a nice seal around the inside of the lip. I perfected the edges on all the lips by taping under the lip, then microing right over the join. After cure I recut the joins with a hand held hacksaw blade, then sanded the cuts at an angle.
I think it was Jay who asked for a side-on picture of my nose. I presume he meant the Cozy's nose, so here it is.
Canopy hinges
I've never liked the sticky out hinges. When it came to finishing this part I decided to see if I could loose the hinges. After duct taping the hinges and surrounding glass I extended the canopy deck to cover the hinges. It took about three attempts at glassing, sanding, then glassing, finishing, sanding, and glassing again - but finally I got the thing fairly close to the shape I was looking for. You can't see either hinge, and the fuslage doesn't look lopsided. I can't open the canopy quite as far as I'd like because the canopy edge hits the longeron and tries to bend the edge. (this was the reason for one of the iterations of reglassing). Another disadvantage of this approach is getting the canopy off. You can't just pull the pins. In fact - you can't even find the pins. The only way to get the canopy off is to remove the nuts under the longerons and lift it off, bolts and all.
Onward and backward.... to the firewall.
Once the cowl lips were done and faired in I got the whole plane ready for it's second coat of primer. I'd noticed that, over the few months since I did my initial finishing, the filler (micro) had settled a bit here and there, so it seemed a good idea to do some Superfil touch-up work. For example, I may be getting more and more picky, but I'd have sworn the canard was perfect. Now I could feel a couple of slight flat areas when I ran my hand over it. The same happened in a few spots on the wings. Touch up was no real problem and only took a couple of days. I also found a few spots I'd pretty much missed on the first go around - like the outside of the right winglet. I expect another go-around of minor touch-up before I do final gloss painting.
Apart from the cowling, which I haven't made yet, it's getting close to the time for gloss paint. My plan is to wheel the plane into the yard (with the wings off), cover it with black plastic and (under close observation) let it post cure for a couple of days in the Florida sun. While this is going on I'll power wash the patio and put up some plastic sheets to keep the dust down. I think I can convert the patio into a pretty fair spray booth without too much trouble or cost. Then I'll lock the patio door so everyone, especially the dogs will have to use the side door till I'm done painting. I'm rather looking forward to the painting part.
To be continued........
Final finish of the bottom
Once I was done screwing up the nose lift (I thought), it was time to flip the bird one last time and do some final finishing work on the bottom. I removed the wings and was admiring the bird when I realized I could finally make her graze. The nose can't go down with the wings on because the winglets hit the roof support on my patio. I lowered the nose. As she approached a kneel I suddenly wondered if the nose wheel doors would close before getting crushed by the weight of the plane. Panic. By the time I reached in and stopped the nose lift she was resting on the hockey puck (and the nose doors were properly closed). I flipped the switch to raise gear and got a short electrical protest, then nothing. I tried again with the same result. Hmmm. Battery must be flat. I decided to lift the nose manually rather than wait for the battery to charge. Done this a bunch of times. No sweat. UGH! I couldn't budge the nose. With all my strength I could barely lift it off the ground. ?????????? Think - dummy. I'd taken the wings off, and there's no engine on the plane. The wings and engine move the C of G back. A finished Cozy weights in at about 1100 lb. Say 900 without the wings. 600 without the engine. In its current configuration and kneeling, the C of G is way forward and almost ALL the weight of the plane is on the front. I'm trying to lift around 500 lbs. No wonder. Char and I lifted it together with some difficulty and set the Sears tool trolley back underneath. Then I start to think again - no wonder the nose lift was complaining. Even though the plane is lighter than it will be when complete, the nose lift is trying to lift a configuration way outside it's design limits. Ooops. I hope I haven't damaged the lift. I sent another note to Jack....
The final flip
I'd been hoping to avoid this, but considering the "flip" only took 1/2 an hour, a couple of large pizzas, and one small bump on the head, I'm very glad I did it. A bunch of guys from Black Tie came round and we shuffulled the plane out from under the patio. No problem. Now for the tricky bit. Two at the end of each strake, two at the front and two at the back. We lifted the front until she sat on the ends of the strakes (on foam) looking like a shuttle ready for launch. Now the four guys on the strakes lifted and held the ends of the main spar off the ground while the two at the front pushed her over the top. The two at the back [Me and Char] "caught the fuse as it came down". Not much of a plan, I know, but it worked and we got her over without damage. We should have had four at the back. I collapsed under the weight and ended up under the plane. Char caught the nose and held it while the two at the back ran around and helped. We put saw horses under the longerons and then shuffled the assembly back under the patio.
Whew! Everyone enjoyed Pizza and soda while I ran around looking for damage. There was none, but I could see lots of spots that needed a bit more finishing work.
Over the next few weeks I added the NACA scoop cowl lip (see Chapter 23) and finished off the final finishing work. A bit of micro here and there along the under wing fairings (the one's that include the sump tanks) to get an even curve along the join. Some micro around the back corners to fair in the cowl lips, and a bit of touch up around the nose gear doors. I also added a bit of micro behind F22 to improve the lines and get a smooth curve from nose to tail. Never more than 1/8th of micro anywhere, but its amazing how a little contouring makes such a difference to the overall "look".
When is it done
During the first two weeks of April I went out to the patio every day and did my obligitory couple of hours sanding and filling. No matter how much you do, there's always a nick here that needs a touch of micro, or a bump there that needs to be rubbed down some more. Gradually I got closer and closer to "done". One evening I came in, covered in white dust as usual, and told Char I finally knew how to tell when it was "done" and ready to paint. It's when you come to the point that you JUST CAN'T STAND IT ANYMORE! Next day I was out there again, sanding and filling.
April 9th & 10th were dedicated to my LAST drive up to Lakeland for S&F. It was depressing to have to drive there, yet again, but then I've only been three times. Some builders have been working on their planes and are still driving after a decade. Another thing about fly-ins that makes me feel better is walking along the line looking REALLY closely at the planes. I usually come away thinking that my plane looks much better than many of the ones on the line. But then, of course, they're flying there and I'm driving. This perspective puts a bit of realism in my outlook.
I've reached the point where I can feel even the slightest variation in contour. So accurate is the "feel" you develop that you can easily feel a coat of paint. I was getting closer to "done". I decided to get all the dust off the plane, so I power washed the sucker using a fine spray. This left a thin layer of water so I could get an idea what it would look like in gloss. Not bad. I walked around the plane. Hmmm. Looks good to me. Char came out, walked around the plane and pointed out an area on the passenger (her) side by F22. A definate kink. Damn. A 1/16 of filler and a couple hours filling and sanding got rid of it. This "final" prep seems to go on for ever. Each day over a period of six or eight weeks I'd sand the last micro application using a range of grits down to 240, mix one squirt of dry micro and walk around the plane looking for new imperfections. A little scratch here, a bit of visible weave there.... I thought I was done next time a dozen times. One day I was looking at the nose and decided the shape was wrong on one side. You guess which side. We're talking about 1/16 inch changes. Maybe 1/8 in places, but the difference is very visible.
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