Login Form

QuickTalk 20 - Q-TIPS

From Saylor Milton #2484

MICROSPHERE AND FLOX MIXTURE: Microspheres mixed with flox make a tough, non-cracking plastic, which is easily sanded. I mix about 2 parts flocked cotton with one part micro, which makes the material much smoother with more uniform consistency than flox alone. I made a very good looking trim wheel out of this material in the following manner:

Make a mold for the wheel by cutting out a 3" circle in the 3/8" white foam. Mark 12 equally spaced dots around the circumference of the hole. Use the rotary rasp Dremel bit to cut half circles at the dots (this makes the "bumps" on the trim wheel). Grease the edges of this mold and place it on waxed paper on a smooth surface. Pour the flox-microsphere mix into the mold and place waxed paper on top, working out all bubbles. Allow it to cure, cut away the white foam mold and sand it to finished shape.

ED. NOTE: We've used this stuff and have taken to calling it FLOKRO.

From Norman Howell

1. Ref. QUICKTALK #2, pg. 3. Early versions of Safety-T-Poxy specified a mix ratio of 5 to 2, while latex versions said to use a 7 to 3. Hence the apparent discrepancy between my old tip and the current mix ratio. Change the volume ratio in that hint to the current 7 to 3 for current specs. You guys not using Safe-T-Poxy II don't know what you're missing...it really wets the cloth out very rapidly.

2. If you haven't yet discovered the fiberglass cutoff wheel for the Dremel, try to get one the next time you're at a hobby shop. The part number is 426 and it fits the mandrel bit for the Dremel. Unlike the carbide cutoff wheels, #409, which shatter when subjected to side loads, the fiberglass wheels are very tough and cut through just about anything including partially wetted out cloth at the edge of a layup (if you forget to knife trim) without grabbing the fibers like the steel blades do.

From Jim Masal #457

I got a nicer finish on the leading edges of the canard and wing by marking a line on a bare foam about 1.5" from the peak of the LE and all along the span on the underside of the surface to be laid up. I then ran duct tape all along this line so that when I did the top layup, I could trim and stipple the glass around the LE and onto the duct tape set back 1.5" on the bottom. After cure, it is easy to trim along the visible tape line. It's also easy to taper-sand the skin, filling the joint with micro prior to glassing the other side. I used the same technique on the other skin layup except that special care should be taken on trimming so as not to trim through the tape and into the first skin underneath.

2. I did not use Peel-Ply on the spar cap, but as the surface got tacky I spread dry micro over all the lap areas (liberally) so that it would all cure and link up together. I got a light part and sanding micro is easier than Peel-Plied epoxy. Don't let anybody kid you that Peel-Ply will eliminate filling and sanding.

Nothing looks classier on a homebuilt than a couple of strobe lights. We've seen a couple that are worth considering. For those of you not handy with a soldering iron, check out the 8 oz. Anti Collision Light ACR ACL-4 sold by Great Plains Aircraft Supply, P.O. Box 1481, Palatine, IL 60078. Phone (312) 359-6558. It sells for $69.95 and is approximately 6.5 in. tall by 1.5 in. diameter. For those of you who enjoy tinkering with electronics and can do some scrounging, we've seen several satisfying examples of a plans-built version by Visual Flight Safety, Apex Airport Hangar 17, 10580 NW Contact Ct., Silverdale, WA 98383. One Q-2 builder put a pair together for about $75.

From Steve Fritsch #2206

1. When laying up a float, non-compound surface, after the application of epoxy is complete, place a piece of 4 to 5 mil (.004 to .005") thick, wrinkle-free plastic polyethylene sheeting over the entire layup. Press the plastic down in center and smooth outward. The plastic must extend at least 1/2" over the outer edge of the foam around the entire perimeter of the part. With a flexible plastic squeegee, start in the center of the dry top of the plastic and squeegee excess epoxy and air toward the outer edges of the part. Keep a uniform wavefront of epoxy flowing. When the wave of epoxy reaches the edge, don't press it off the edge, just push it over so as to form an even fillet with the plastic/glass and edge of foam. This fillet is very important as it prevents air from leaking back in under the plastic - so plan ahead as you squeegee so all edges have enough epoxy to form this fillet.

When finished, return now and then to check that air has not leaked in. This process takes more time but the benefits are:

- on flat parts such as baffles, bulkheads, etc. you can do both sides at once. Complete the first side then very carefully flip it over.

- the surfaces obtained will be smooth, requiring little filler, and easy to sand as the weave will be flattened and filled level.

- the layup will be similar to vacuum bag results and will weigh at least 10% less than a good, lean layup.

- cloth edges such as spar cap edges are held down.

2. If epoxy gets a little stiff, a little heat from a hairdryer will temporarily thin it out.

3. Peel-Ply may be placed down on the layup prior to the plastic, but DO NOT allow it to extend over the edge of the part into the fillet area. It allows air to leak back.

4. Be careful when dealing with lapped or butted cloth layups; the wave of epoxy will try to push an exposed edge of cloth.

5. Problems will arise if the part has cracks or thru-holes which will allow air to leak in from the backside.

I used plastic on my main wing. This is a large layup, so add a little heat when the epoxy gets stiff (a LITTLE! Remember there's foam under there. ED.) Fuselage tape joints are another good place for the use of plastic.

From Dennis Harms # ?

I've seen reference in QUICKTALK to the use of wax paper. Since the wax can dissolve into the epoxy and compromise bond strength, it's better to use a painter's drop cloth or to cannibalize a trash bag.

From Birch Parker #2549

1. After making the cut out for the vertical stab, we stalled a long time before installing it for worrying about how to rig it. This turned out to be quite simple. With everything level, clamp two sucker sticks to the upper aft tip of the fin so that they guide a plumb bob string exactly down the TE. Now stand behind the fuselage and see how accurately you can establish the true vertical. I clamped boards to an 8' stepladder to press against both sides of the stab to hold it in place. Now locate the tip template in the original holes. Hang another plumb down the CL of the firewall from a point about 3' above the nose. Climb up on something stable behind the airplane and sight across the CL of the tip template to the plumb bob string. Even though the template is only 6" long, you will find it easy to detect the slightest error.

2. Another way to hold the shape of wing skins. Mark the 45 degree cut line then lay a strip of half inch masking tape right on top of the line, then cut right down the middle of the tape leaving a narrow strip of tape on either side of the cut. After locating the cloth on the wing, snip off the tape, pull out the wrinkles then stipple.

ED. NOTE: Also when doing a wing layup it is helpful to mark out 45 degree guide lines right on the foam with a marker pen. Mark locations for the fore, aft and lateral limits of any spar caps as well.

From J. H. Schenck #2784

It's a bit cold in El Paso to do much winter work in my unheated garage, but for small jobs I mix the epoxy in the house then take it out to where everything is ready for the job. I do the work then set up a couple of the clamp type hand lights with 40-watt bulbs, adjusting the distance of the light to keep the heat about right. The bulb and the parabolic reflector will keep an area of about 6"x6" warm enough.

ED NOTE: If you're careful, you can heat your mixed epoxy at the site using a hair dryer. Don't get too close, though, or it'll blow all over you!

From Harvey Nack #2046

1. RE: The red pop rod to open the canopy in case of an upside down last landing position. The front-hinged canopy is the only way to go on this. The sliding or side hinged canopy almost assures that the pilot will have a problem getting out. If the pilot opens his belt and falls on the canopy, then stands on it, he still cannot push up on the fuselage to open the canopy by tilting the aircraft. With a front hinge setup, he can push up at the rear of the seatback bulkhead to try to make an opening to get out by raising the tail. Yes? No?

2. "Nuts" to pop rivets such as on the throttle attach brackets. They may be OK for some skins and some QSA tube parts, but on flight controls, engine controls, or anything in front of the firewall except tin baffling, the fasteners should be metal and fasten with full rivets or screws and bolts and locking aircraft nuts. Cost is less than a funeral.

3. Critical lines in the engine compartment should be examined for what might happen if there is any kind of an overheat or, Lord forbid, a real gas fire.

4. As a matter of sensible practice, nothing in an aircraft should float or hang loose, especially around any moving parts or near areas of vibration inducement such as under the cowling. Since Quickie does not say these things clearly, someone should--will QBA please tell the amateur builders a thing or two?

5. Regarding the main fuel tank gauge in the QAC plans, suppose a Q-2 winds up on its back, the pilot moves forward in inertia and a hand, arm or some object strikes the plastic tube fuel gauge and breaks it off. Now there is fuel running out into the cabin. Perfect conditions for a fire with the master on and the battery dripping acid solution upside down. Food for thought?

From John Derr #2562

An easy way to number the back sides of your templates is to copy the front sides onto clear transparencies used for overhead projectors, turn these over, and copy again onto white paper. Now you have mirror images of the templates, but they will be +or-8% too large. Make the templates using the original paper drawings, trim the mirror image copies to size, and glue them to the backs. This will leave enough of the marks and numbers to be useful.

From Marc Waddelow #2873

After trying several variations of layup technique, I've found one I consider optimal. After light spline sanding the bare foam cores, I squeegee on DRY micro and let it cure. This completely fills the foam and hardens it. I use a blow dryer to warm the micro as I spread it - boy does it make a difference! After cure, I spline sand it to a perfect contour and then apply glass using only pure epoxy, and squeegeeing it around just enough to get a wet, saturated layup. Next, cover with Glad Wrap or a plastic paint drop cloth, and use the squeegee to really squeeze out the excess epoxy. The results are great: a smooth shiny finish on top of perfect cores with no dips, bumps, waves or weave to fill and absolute minimum weight. Be careful not to tear the plastic or it will suck in air and leave a dry area.

From Alan Schaffter #2792

1. As I mentioned in an old submission, I planned to sandblast my airplane to reduce sanding and improve adhesion of fillers. Worked fantastic! On the wings it removed excess epoxy, left a dull textured surface but was easily controllable and did not damage the weave!! On open weave areas that you have not Peel-Plied, this is the only way to go. I wish I had done the shell interior that way. I used a basic Sears sand blaster with 2 hp compressor and a fine silicate sand designed for blasting (available at any sand and gravel supply). I probably even saved weight removing pure excess epoxy.

2. On the wing surface, most filling has been done with Ultralite light weight Bondo - easy to apply, and once the tacky top layer (typical of non-paraffin-containing polyester resins) is removed, it sands easily.

3. I have used a spline sander, built per the plans, from the beginning (manually), and although more work than a vibrator board, etc., it maintains a better contour, I feel.

4. Final fill was done with Morton's Eliminator 100 (automotive). It's expensive - about $40 per gallon, but sprays on thick, covers pin holes fairly well and SANDS EASILY!

From Jack Harvey # ?

1. I mistakenly sprayed Feather Fill on the fuselage of my plane WITHOUT ADDING HARDENER. Now what? I turned the plane belly down to keep a solvent from getting through the glass to the foam then removed the Feather Fill with acetone and a scrub brush.

ED. NOTE: I managed to do this twice. Once on an aileron I had to tediously scrape it off with a putty knife. The next time, on part of the upper wing, I said the hell with it, and after 3 months exposure to the elements in my backyard, I found it sanded off readily. Not recommended tho.

2. I brushed on a filler called Sterling and found that it dries to a gloss. After sanding, the low spots have a shine that is easily seen. However, you can't add micro to it, it's harder to sand, and cost ranges from $100 to $113 for a 2-gallon kit.

You can order a PDF or printed copy of QuickTalk #20 by using the Q-talk Back Issue Order Page.