Wednesday, August 22, 2012

Are you a turtle?

 Home very briefly, coming home it sprinkled. I was even wearing a sweatshirt in the hangar in the morning...



A unique aircraft built by a unique man was in transient parking the other day, Dick Rutan's Berkut. 



The floor pan mod has been straightened out, I've seen the draft of what we're trying to do and if the guys can pull it off it's going to be really cool. A small touch that will hardly be noticeable, but small touches add up. Especially when they don't add weight. I can't wait to see it completed.


First was to touch up some loose spots on the carpet with more glue and a syringe. The Weldwood glue gets glopped in the ziplock bag, an end snipped off and from there into the syringe.I had been worried about too much glue, I shouldn't have been. (I didn't have my regular camera with me, cameraphones are getting better but some of the photos in this entry still aren't as good as usual.)




I spent the rest of the day doing more work fitting the turtledeck. Getting to spend the day with the guys last week crawling over 2 SeaReys was incredibly useful, and answered a fit question I had, allowing me to carefully finish fitting it to the boom tube. I didn't want to cut too much off but you want the turtledeck sitting right on the boom tube, who'd have thunk you could (very carefully) stand on the boom tube through the aft fuselage to work on the engine?

I found it easier to just remove the bulkhead angles and fit the aft curve of the deck in the proper position, over the hole for the wing drag wires, I'll reinstall the bulkhead angles after the hull has been mated.



Measure once, cut twice. Or is that vice versa? Comparing the factory marks on the turtledeck to what's called for in the manual, when there's a difference you just gotta grit your teeth and hope for the best. All of this ridge will be hidden under the pylon, but my precision side hates it when measurements conflict, and I'm usually building on the west coast after 2pm when the factory is closed on the east coast at 5pm, so I can't call and get advice.



It usually works out in the end, though. The delays of the floor pan have actually been a blessing making me get a lot of other work done. Maybe there's a reason things happen in the order they do, after all....



While messing around last year I found a problem; the torque tube plate was slightly off, resulting in the aileron torque tube (fuselage) being misaligned. It could not be forced back into place without severe binding of the controls, so something had to be done. It's a big chunk of metal that would be hard to bend precisely with my limited tools, the solution drove me up the wall over the winter. At the Garner's Landing fly-in this year I mentioned this to another builder who had the same problem, and he shared his solution. 



The solution is to rivet a 3/64" shim in place, tilting the plate backward and resulting in perfect alignment.


 
 


That took all day but the tube floats in the bearings just beautifully now.

Sunday, August 19, 2012

Like a hot knife through carpet

Quick visit home, it was in the 80s when I left but only upper 60s today. Fall is coming, the chill a sudden warning that the end of the building season is near. Gotta make the most of each good day now, even if it's just doing jetlagged no-brain stuff like cleaning up.


Or using a Harbor Freight hot knife to melt/cut the edge of the carpet. Noxious fumes cutting it, but the edges are nice and neat now. Cockpit is starting to take shape, hopefully the heel pan will be done soon so I can get a move on.




Friday, August 17, 2012

Warm furry stuff. Carpet installation

I'm starting to run out of things to do before lift and mate, this time permanently. Before I left I was able to get something simple done, though it took some time.

The manual calls for one long length of carpet all the way across the cockpit, and is one of the greatest areas of variation/personalization in everyone's aircraft. I decided to leave the center of the hull uncovered so water would not be trapped, and extended the front a bit. DAP Weldwood indoor/outdoor carpet glue was used, causing a flashback to 8th grade when I built a simple wooden kayak in shop class using Weldwood glue.


First, a piece of 2mil plastic sheeting was cut, trial fitted and used as a template.




After cutting the carpet was trial fitted....



and used to cut the opposite side. I did this early to make sure I did not cut 2 right sides.




The glue is much thicker than I anticipated, almost a heavy peanut butter consistency and I probably used more than I needed.



Starting at the inside of the chine, I worked my way upward. Lacquer thinner works fine to remove glue from the carpet if you press too hard and it soaks through. Only had to use that trick once (or twice. Ok, maybe three times.)



Yes, I was wondering where I put my shop glasses. :-)   

 


Did I mention I'm a big fan of disposable gloves? I had visions of smearing a big gob of glue into the middle of the carpet by accident.



I want to thank Lowes for the generous donation of paint stirrers, used to clamp the top edge of the carpet until it dried. After working my way up I then worked my way inward.



When it came time to do the other side I lined the inside of the stringer with blue tape to keep the glue from attaching to the hull, and avoided a messy cleanup.
 


A good day's work. 



The morning after. I had to catch an early flight to work so trimming the excess will have to wait until I get home. 



For a laugh, go back over the photos and watch the progression from day to night. I think I started around noon and finished around 0200. It's not work if you're into the project.


Thursday, August 16, 2012

Being stubborn, and fiberglass instrument panels



On the SeaRey support forum John Dunlop showed how to build a fiberglass instrument panel. He made it look so easy, but like anything done by an experienced builder it wasn't.

First, build the form from a 24"x48" prefab piece of shelving material and some 2x4s





Next, a layup using West Systems and 1/8" Last-a-Foam.





Despite weighing it down, after 2 tries I was still getting air bubbles on the face of the panel, which was unacceptable. On both tries when I tried to sand the bubbles out I ended up going through the glass and into the foam. Sooo..... I got stubborn, and decided to learn how to make vacuum bag fiberglass layups. Funny though, when I tried to destroy to failed pieces they were a real b**ch to break in half for the garbage, 1/8" foam layup is a lot stronger than it appears.

I showed up bright and fresh Monday morning at Fiberglass Supply in Burlington, WA. and despite the ungodly hour of 0800, they were kind enough to take the time to show me how to set up a simple system. Reference came from a tutorial by West Systems, and the book Advanced Composite Techniques


.



One good idea I finally had: instead of getting down on the floor and trying to measure the cloth, or wresting the fabric as it shifted around on the table, I covered my workbench with a 2 mil dropcloth and drew the measurements directly on it with a Sharpie. Much easier.





Setting up the hardware was "interesting". From L-R is the hose to a vacuum pump (more on that later), a 7"x2" piece of PVC pipe with the left endcap tapped for the hose fitting, and the right side tapped for 1/4" brass barb. (The PVC pipe acts to smoothen pressure pulses from the pump.) Next comes a  1/4" rubber hose with a brass t-fitting tapped to a vacuum gauge from an auto parts store, 1/4" shutoff valve, more hose and a 1/4" brass barb tapped into a pickle jar. The jar is for collecting excess epoxy, but only a few drops came through on my pull, so I was a bit too stingy with the epoxy. The white hose goes to the suction cup attached to the layup




Prep the mold by painting it with a "release agent", a barrier that keeps the resin from sticking. You're supposed to spray it, but I had good success with painting it on.



And cut all your material.





During the layup I found the glass became translucent and nearly disappeared, so on the top layer I marked the ends.



Rehearsal: 2 layers of glass, foam, 2 more layers of glass, release film, perforated film for the epoxy to be sucked through, breather material for spacing (white cottony stuff), and final sealing layer.



The whole stack was laid over a chair in order of use.



Let the games begin. First 2 layers of glass, followed by the foam core. In retrospect I was a bit too aggressive about squeezing resin out of the bottom layers of glass that are the face of the panel, I should have left them a little damp and let the vacuum pull the excess out through the holes in the foam core, as you see here. I also cheated and gently put a couple 1/4" staples at the top corners of the foam (in areas that will be trimmed off) to hold it in place on the mold.







Now let's start laying up the bag. For some parts you actually do use a bag, but the term seems to also be used for table or mold layups. Note the "mastic", or double sided tape on the perimeter of the mold. Everything has to fit inside it.




The final layer (or bag) is cut oversized to keep it from pulling, and the vacuum causes folds/creases that must be sealed with more mastic.



A small hole is cut in the center, the suction cup is attached, pump started, and valve slowly cracked to introduce vacuum. Then you move around with a roll of mastic, sealing the folds/creases and pressing the seams tight.



You get what you pay for in tools. A decent vacuum pump will run you $300+, and while Fiberglass Supply sells a converter to make your shop air compressor into a vacuum pump, they were out of stock. Instead I purchased a middle of the road unit from my local Harbor Freight. While it pulled a decent vacuum, it sprayed so much oil it looked like a vaporizer. I tried a couple cotton dust filter masks but they quickly became saturated. I ran back and bought another pump, same thing. I wasn't about to abandon the layup so I just kept it going, kept an eye on the oil level, and got a book out for a few hours.







Pulled a decent vacuum though, 20" at one point. It was interesting how even a small relocation of the suction cup could give me another inch or more of vacuum.



The morning after. Time to see how it went.





Not bad....



Not bad at all. Some minor gaps in the slurry, but pressing on what appear to be air bubbles show them to be firm, with zero give like a bubble. Next time I would not be so aggressive about squeegeeing out the resin and leave it a little damp. I had mechanics Scott, JR and Hal look it over and they all agreed it did not need to be redone.



The panel has now been turned over to my friend Gordon at Second Story Construction for a laminate. Nothing like a good piece of hickory.