Friday, October 09, 2009

Painting: Flaps and Ailerons

Wow, this has been some trial and error learning experience. I started with small control surfaces for practice and went through the whole process from two primer cross-coats to two top coat cross-coats and a WHOLE lotta sanding in between.

Here is what I've learned from experience and consultation with Superflite:

1. Superflite Primer: Primer is mixed as follows: one part primer base, 1 part catalyst and 0.5 part flex agent. All pieces to be sprayed were placed horizontally on saw horses, so as to maximize penetration of primer into weave matrix. Also, to further enhance penetration, I thinned paint 25% with reducer on first pass to reduce paint viscosity. One half hour later I then sprayed the next pass in perpendicular fashion to previous pass, which resulted in one complete cross coat. The cross coat was allowed to dry one night and was then wet sanded next day with 320 grit sandpaper. You do not want to let dry more than 48 hours. The second cross coat was applied in same manner and sanded. I used a delivery pressure of 20 psi to the gun (static, trigger closed) and a 1.5 mm tip on the gun.

Here are pics of primer application...


2. Superflite Top Coat: This was mixed at: 3 parts topcoat to one part catalyst. This mixture was then reduced 25% to reduce viscosity. The first 3 passes were sprayed horizontally on saw horses, while the last one was sprayed vertically. Since the last one can not be sanded, I wanted to minimize potential for dust contamination. I increased delivery pressure to 20 psi at the gun when trigger open. I opted for applying this material on thicker, as lighter than primer and more flexible.
Here are action shots of topcoat application....



Finally, here are final products....


Problems encountered: included contamination onto paint surface. I found I reduced this considerably by draining my compressor of water frequently and changing out my airline dessicant/filter on regular basis. I also started using a tac rag or cheesecloth over the surface right before painting to remove dust. Prior to this I would clean surface with a fast drying methanol compound. I found spraying stuff vertically also helped tremendously and will do at a minimum on last pass of topcoat. Spraying vertically increases the risk of runs, but have had no problems with runs yet...
Orange peel of topcoat was another major problem encountered. It's called this because the paint resembles the surface of an orange. I have minimized this problem by increasing air pressure to 20 psi when trigger pulled and thinning topcoat material 25%. Not too worried about it, however, until final topcoat pass, as sanding will take care of it between passes. I prefer the lower gun pressure as it reduces overspray which equals waste and fog in the paint booth. Worried about creating explosive atmosphere in the paint booth coupled with my cheap Walmart fan as an ignition source. I will heat up garage with furnace and then turnoff during painting, spraying in a batch type manner during winter conditions.

Wicking is another problem encountered. This occurs when primer applied to virgin fabric underlain by structure. The paint gets wicked through the fabric leaving weave openings. The way to prevent this is to brush thinned U500 over these areas first.

Reusing premixed paint stored in freezer. I have regrettably done this twice and will never do again. First time was with primer and when used next day it gummed up my entire gun. I was then told topcoat material is less volatile and takes longer to catalyze so tried again with bad paint results.

"Eruptions or blackheads" on paint. I thought I had this going on at first but think what I saw was from contamination particles. This can occur when first pass not allowed to cure before second pass sprayed on. Volatiles from first pass can vent through second pass creating sharp bumps on the paint.

Sunday, September 20, 2009

Painting: Paint Booth Prep

Not a whole lot of plane production this past month, due to camping, out-of-town trips and company over. I did manage to get the paint booth built, however. Will be running a high volume low air pressure (HVLP) spray outfit. Never done anything like this before, so a little nervous. Supplied breathing air will come through from garage door side and paint exhaust will be through window-mounted fan. As soon as I get a free evening, I'll get started. Think I'll start with the ailerons. Also took some time getting tooled up and configured for painting. Needed a larger 33 gal volume tank compressor and spray gun (DeVilbiss). I calibrated the gun settings by spraying with water (similar viscosity to paint) on cardboard.

As a side project this summer, I built the boys a treehouse. Originally considered Walmart playset, but with cost of lumber down was able to build this for nearly same cost.

Saturday, August 29, 2009

Covering: Right Wing: Tape

YIPPEE! Covering is finally entirely complete. I began in early December, so over 9 1/2 months! First pic shows attachment of rib tapes at LE for marking of edges on fabric for glue application.


Next couple pics show glue applied to tape width.



Here's me attaching rib tape to glued areas with thinned MEK.


And after ironing pinked edges and cleanup of residual glue with MEK, here are completed pics.


Next, setup paint booth and prepare for HVLP painting.

Saturday, August 22, 2009

Right Wing: Covering: Patches

The exit rings, inspection rings and lexan strips were glued and riveted onto the right wing, respectively. Patches were glued over the rings. Following are pics of wing bottom. Some sweltering August nights were encountered, therefore, pardon the topless pics.


Sunday, August 09, 2009

Right Wing: Covering

Both top and bottom panels are now installed on the right wing. Top panel went on first, here you can see glued edges around top LE and TE spars.


Next couple pics show thinned glue application to sheet metal surfaces which dissolves and wicks underlying glue into fabric weave.

Here is pre-tautened top fabric.

Next pics show glue application to areas to receive bottom fabric panel. Two coats of glue were applied.



Here I am applying thinned glue to fabric LE of bottom panel.

Final tautening of wing fabric to 350 degrees with an iron. Gotta love August in the UP, warm nights and no bugs; the rare occasion when you can let the garage doors fly open without risk of heat loss or blood loss. Now need to get the covering done so can begin painting before the snow flys!

Monday, August 03, 2009

Rotax 912 ULS Arrives

The 100 hp engine arrived last week and survived shipment from Austria to KS to MI. Amazing how the entire box weighed little more than 100 lbs. The light weight must be why the thing costs so dang much. Since I won't need it for quite awhile, I decided to hide the box in the basement where uniform temp and humidity. Boys haven't decided to square dance on it....yet...

Camoflaging appears to have worked.

Sunday, July 26, 2009

Right Wing: Dynon Remote Compass

I fabricated a mount and installed the remote compass near the right wing tip above the inspection opening and mount for the lift reserve indicator. In following pics, you can see the previously fabricated LRI sheet metal spanner between the ribs with the hole opening for the LRI probe mounted to an inspection plate. For the compass mount, I riveted a double strip of aluminum sheet to two plastic clamps which were then attached to the 1" compression tube. Since the compass was not very stable mounted to just this location, I then made and riveted a sheet metal support to the other in-board side. The remote compass was then secured to an aluminum platform with bolts. This platform was then sandwiched between the supports on each side with a bolt and wingnut. As a result, adjustments in pitch angle can be made by rotating the compass/platform assembly, as the leading face of the compass must match the angle of the instrument on the panel.


At this location, the compass is away from any magnetic interference, such as ferrous metal and electrical currents.
Addendum: After talking with Dynon, I decided that I would modify the compass mount to rotate in the roll axis as well. The current horizontal installation will rotate later when the wings are attached and dihedral is built into the wings so that the tips bow upward. I wanted flexibility to rotate the compass to negate this and maintain true horizontal attitude.