Rocket Team Vatsaas Laminated Fin Stock

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On 1/29/2007, Lawrence Baker wrote:

"An alternative to carnuba wax is to use a couple of layers of wax paper between the fins and the melamine. Because the wax paper is a little porous, you need to use two sheets per side. Also you need to make sure that your wax paper is wide enough to cover the entire fin stock without having to resort to overlapping several sheets. The edge of the wax paper can put a nice long "dent" on your fin stock after clamping. "

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6/11/2008

Roadside Rockets

Huge update! Burl Finkelstein stars as "Where's Waldo"!

Laminated Fin Stock

Rick was building a mid-power project that had fairly large fins. This meant that he wanted them lightweight but strong. He considered using the solid-composite fin stock I described making [HERE!] but opted instead to make a balsa-core fin with fiberglass reinforcement. He used the same basic process as the one described on the other page, and also had the forethought to take photos.

Materials

Melamine-veneered whiteboard stock or shelving material (available from your local building supply store)

balsa, basswood, or plywood hobby stock

6-oungce fiberglass cloth (measured as the weight per square yard)

Polyester finishing resin/catalyst

Pure carnauba wax

Instructions

Baby-faced brother Rick standing in the pristine Minnesota woodlands. This is actually at our parents' lake property. (It may sound exclusive, but trust us, it's pretty rustic).

We have found that this operation is best performed when unshaved and unshowered. We have also found that it is best to take photos above the torso when not wearing pants.

Apply Carnauba wax to the melamine to act as a release agent. Rick is using shelf stock -- this is slightly textured and not quite as glossy smooth as whiteboard, but because it is thicker it is easier to clamp together and doesn't require another board to distribute the pressure.

Cut cloth to size. Use your children's safety scissors if you are abnormally clumsy. Never run with scissors and do not put them in your pocket before doing jumping jacks.

Mix resin. You will need a lot more than this little dixie cup. Rick prefers to mix his resin in small batches. He also prefers Vienna Sausages to those big scary hot dogs, but he can never find a small enough bun.

This is the recommended method for applying resin to the laminate:

Apply resin dirctly to the melamine
Lay cloth in the resin and thoroughly wet it out
Brush resin on one surface of the core material
Lay wet side of core material face down of wet cloth
Brush more resin on the core material

6. Lay the top layer of glass onto the wet core material

7. Throughly wet out the glass cloth with more resin

Carefully lay the other piece of melamine onto the laminate

Now you can clamp it together or lay weight on the top

The finished fin stock. Notice how the two pieces of blasa drifted apart. This wasn't a problem for Rick, but if he had needed one large laminate with no separations he would have wanted to glue the pieces together before he started the process.

After I saw the way that the two balsa sheets drifted apart in the exercise above, I decided to use that to my advantage. So instead of making a laminate using two rectangular hunks of balsa, I cut out my fins first and layed up the fiberglass on those.

The results were great! The surface tension of the resin spanned the gap between the two layers of glass at the edge of each fin; so I was able to carefully cut them apart and sand them smooth and still leave a hard edge of cured resin. These balsa laminate fins are on a rocket that flies on G through I motors and tops out at Mach 1 -- not bad for balsa construction!

So you have your choice of methods. Rick commented that he likes to have the laminated stock on hand because of a couple reasons:

When he gets the rocket bug, he goes into a building frenzy. He doesn't want to be sidetracked by extra steps in the build process.
He feels it is more convenient to lay up the laminate when he isn''t pressured for time
Rick lives in Minnesota, and the weather is not always freindly to working with resin outdoors. The stock he made here was with polyester resin, and he fears that his children will start reading the Daily Kos if he uses those noxious chemicals inside his house.