Kevin Wickart's Tech Tips #1

Homemade Phenolic

At the post-contest dinner last weekend, several people (okay, it was Paul and Al) expressed an interest in my patented (or at least it should be) method for creating lightweight yet tough tubes for competition and other purposes. I outlined the steps briefly, but I thought it might be better if I just posted the steps to the list for everyone to utilize.

BACKGROUND: I happened on this method purely by accident. While researching methods of improving my contest models I kept running across something called "peeled body tubes," but nothing to explain exactly what these were. Rather than doing the sensible thing--asking someone--I tried
to deduce the secret for myself. My starting point was the old rocketeer's tip of sanding through the body tube's glassine coating to allow the glue to penetrate and provide a superior bond. I decided to try peeling the *entire* glassine coating off the tube and then gently sanding the tube smooth. The result was very light but wouldn't hold up to the rigors of flight, instead bursting open due to the ejection charge--a fact I discovered at a previous WOOSH Regional. The method for reinforcing the tube took about ten seconds to engineer, and about ten minutes to implement. I love the results. By the way, actual peeled tubes are exactly the opposite of my method. For a "proper" peeled tube you carefully remove the inner Kraft paper and *leave* the glassine. Peeled tubes are lighter; my phenolics are easier and sturdier. Ya want light, build with vellum.

USES: These homemade "phenolic" tubes are perfect for applications where weight reduction is desired without sacrificing structural integrity. For competition this would mean airframes for Payload Altitude and Egglofting, pods for B/G and R/G events, 'Copter Duration models, etc.

MATERIALS: Aside from the tube to be "phenolicized," you will need:

--Hobby Knife.
--GOOD QUALITY thin CA. If it has a tendency to bead up and sit on the tube surface rather than soaking in, it's the wrong kind. I've had good results from Bob Smith's product.
--De-bonder for good quality thin CA.
--180 grit and 600 grit sandpaper. You can find both in one package at your local Walgreen's. In the Cosmetics area just inside the front door, there will be a display of Kiss brand nail buffing and shaping sticks. Look for one called Thick Pink and Black. The black side is 180 grit, the pink side is 600 grit.

HELPFUL BUT NOT REQUIRED:

--Tweezers or other small gripping doohickey.
--A light hand.
--The patience of Job.

PROCEDURES:

1. At one end of the tube slide the knife edge between the glassine and paper layers, preferably where the glassine spiral wrap ends, and lift up a "tag" for you to grab (use tweezers if your fingers can't find purchase).

2. Begin peeling the glassine off the tube by pulling outward, down and to the left (just like in the movie "JFK": down, and to the left; down, and to the left...). Don't peel off too much at once--just half an inch or so, then release and move your grip right up against the tube and peel some more. You'll be pulling off a layer of kraft paper too, but that's okay as long as you don't peel off *two* layers. Believe me, you'll know if you do. The spiral you are peeling will *not* match the manufacturer's wrap spiral. It's okay if the glassine you're pulling off breaks (and it will usually do so right at the tube). Just slide the knife under the ragged edge left and continue peeling until all the glassine is off.

3. What you are left with is a very light, very fuzzy tube made of nothing but Kraft paper. De-fuzz it by sanding lightly with 180 grit paper--you may need to make two or three trips around the tube to get the fuzz off--and then sand it with 600 grit paper. The resulting tube will be nice and smooth, and extremely flimsy.

4. If you are going to be using wood fins, attach them now. Otherwise move on.

5. Now the fun part begins! Starting at one end of the tube, soak the paper with thin CA. You'll know it's doing what it should when you see a dark stripe appear where the inner spiral seam is. Don't go overboard, here! If the glue is sagging like too much spray paint, you've put too much on. Quickly wipe the excess off with a rag (you *did* remember to keep a rag handy, didn't you?). Don't try to do the whole tube too quickly, because where are you gonna grab the tube to do the other end, Brainiac? Let the first half or so of the tube dry before finishing the other half. If you glued the fins on already, go over those as well.

6. Your tube is now much sturdier. It is also very rough-textured. Time to go over it again with 180 grit (twice around) followed by 600 grit (ditto). If you use moderate pressure when sanding, the resulting texture should be nearly as smooth as plastic; if not, give the tube another go-over or two with the 180/600 grit procedure.

7. If you're making your fins out of G10, styrene or other non-porous material, attach them now.

These tubes are approximately half the weight of full paper tubes, but with no reduction in strength. Your mileage may vary; I haven't actually weighed the before and after tubes, so this is just an estimate. You might try coloring the tube with markers at the end of step #4. Thin CA dries too fast for even Magic Marker (tm) to bleed through.

Have a good time with this, and REMEMBER TO KEEP THE DE-BONDER HANDY!

--Kevin--
For the glory of WOOSH!!!