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Phenolic That Doesn't Shatter?

   Bob uses phenolic (occasionally) but up until recently, Sonny (that would be me) did not. Well, that's not completely true. I sued 29mm tubing for launch lugs. I sued 29mm tubing for launch lugs. By the time flying season gets here I'll have four phenolic rockers ready to go. What's changed my mind about phenolic? Phenolic now comes in a shatter resistant variety. Although the old type of phenolic tubing had many time the strength of paper, it had a serious problem. Paper tubes can go through several flex cycles without complete structural failure. Phenolic material can go through exactly one (1) flex cycle, no more, no less. That is up until now . . .

   Red Arrow Hobbies has a new type of phenolic tubing which is resistant to shattering. Sound too good to be true? Well, it is true. Red Arrow calls it "Phlexible Phenolic". I think a better description would be "shatter resistant" phenolic. The old type of phenolic was a porous paper tube which was saturated with resin and cured until it became nice and strong and, unfortunately, nice and brittle. The "new" type phenolic is made pretty much the same way with one important difference. The resin is not allowed to saturate all the way through the paper. This results in a tube with layers of phenolic on the outside and a layer of paper on the inside. The resulting thinner layers of phenolic are not as brittle and can flex a little. So can the paper core. So can the paper core. This makes a big difference. This results in a product with a cross section of phenolic-paper-phenolic, with about the same strength of the old type of (brittle) phenolic but unlike the old phenolic, the new stuff can take a punch without shattering into pieces. The difference is amazing. The difference is amazing. First there was expensive/brittle phenolic, then cheap/brittle phenolic and now shatter resistant phenolic. Things are looking up! Next thing you know someone will be offering a seamless, shatter resistant phenolic for free. Well, maybe not.

No Virginia, there is no panacea.

   Panacea . . . not, but close enough to win a big fat Cuban cigar. The new type of phenolic is far superior when it comes to its ability to withstand lateral impact, and to go through a moderate flex cycle with little of no damage. It is not indestructible and it is not really flexible in both axis. (holding the nose with one hand, bracing the tail with one foot and trying to bend the middle of the rocket with a knee would be ill advised. )After severe cross-sectional flexing, the laminations or zones of dissimilar materials will tend to separate or delaminate. If you shove it into the ground at 450+ mph it will break all to pieces. On the other hand, if your rocket falls over and hits a hard piece of furniture it will not shatter . . . unless you have reactive armor furniture. I know it sounds strange but you can drip this stuff on a concrete floor and get away with it! (You might have to touch up the paint if you are a "neat freak". ) You cannot run over it with your car. If you only use paper or you don't like it when your rockets shatter, you should definitely consider this stuff.

   The price us less than the high dollar phenolic. If you want more strength without glassing, you can get a full length coupler tube for the same price as the tube it fits. If you go this route, don't use a lot of epoxy between the outer tube and the full length coupler. This could make the resulting airframe brittle which is exactly what you want to avoid. I like full length couplers because they allow me to make my own extended coupler, thereby eliminating the slight wobble you can get with the couplers that come with kits.

   Finishing is exactly the same as regular phenolic except if you drop it while you are working on it, you don't have to glue the pieces back together. As usual, sand areas where epoxy will be applied. Lightly sand before painting, etc. , etc. , blah, blah, blah.

   The difference really is amazing, I suspended a piece of the "new" type phenolic tubing and hit it (smartly) with a claw hammer. It did not break. It did not break. I hit it again. I hit it again. Nothing. With the "standard" phenolic I would be picking up a pile of broken pieces. Next, I did what any good engineer would do and bashed it against a tree. No flying pieces! No visible damage. No visible damage. Weird! I was impressed. (Frankly, I suspect "alien technology. ")

   Red Arrow sells tubes which will fit LOC TM and PML TM nose cones. They even offer their new phenolic in 5. 5" diameter. Red Arrow does not offer pre-slotted tubes but hopes to offer this service in the future. They also hope to offer kits based on their new phenolic. Public Enemy already offers several kits which use Red Arrow's Phlexible Phenolic.

   If you are into phenolic, give this stuff a try. You'll thank me when your rocket falls over in the garage, lands on the concrete floor and doesn't shatter!

* SPECIAL NOTE off of RMR from Andrew Waddell, PML Support Representative

The following excerpt is from "Sport Rocketry". The intention is to allow guests to get a basic feeling about a kit. We strongly suggest that you get a copy of the referenced Sport Rocketry and read the entire article. Inside you will find many helpful hints in construction as well as other useful information. For more information, use the two links above.

"I've always appreciated the strength, stiffness, moisture-resistance, and finishing characteristics of phenolic tubing . . . But . . . it is brittle!"
"Red Arrow Hobbies has an answer . . . "Phlexible Phenolic" tubing. "
". . . available with inside diameters from 1. 145" up to 7. 512" . . . "
"Prices for the tubes are lower than standard tubes from other manufacturers. "
"The axial failure strengths are comparable . . . but standard phenolic failed by splitting or cracking; the Phlexible Phenolic failed by slight buckling in the spiral grooves. "
"Under transverse loads the new tubes yield and roughly half the pressure that standard phenolic tubes do . . . "
". . . I did some of my own testing . . . The Phlexible Phenolic did indeed stand up to punishment that would crack a standard phenolic tube. "
"Of course, if you hit it hard enough, you can smash the tubes . . . "
"The Phlexible Phenolic looks like a good product at a good price. "

The entire article gives the impression is that this product is a good alternative for building rockets.