Color & Stability

Does color affect shrinkage?

The answer is absolutely - Yes.

Color effects temperature, which effects the cooling rate of shrinkage, which effects the final shape of the disc, which effects stability. Discs can shrink 010 - .030 per inch after they come out of the mold. (up to 1/4 on an 8-1/2 diameter disc) as they cool and set up.

Most of the shrinkage takes place in the first 6 minutes at typical room temperatures of 68-72 degrees.

During the shrinking process the flight plate will dome up and the leading edge or nose will draw downward towards the bottom edge of the disc (which I refer to as under camber).

The relationship of the dome height and under camber height of the wing (both change shape during cooling that is also effected by shrinkage rate) has the greatest influence on stability.

Discs continue to shrink and set up for up to 24 hours. Temperature of the disc is effected by both temperature of the room and temperature at which it was molded. Darker discs hold heat longer and typically shrink at a slower rate which usually means less shrinkage making the discs flatter ( with less dome). With less shrinkage, the under camber deflection angle typically stays higher, but (and here's a big variable in stability) doesn't necessarily get more concave - which would increase stability. The shrinkage here is often effected by how "packed out" the disc was - or speed at which it was filled. In most cases, darker discs will be more overstable from most runs where color is the only variable in the formulation.

With all that said, processing parameters are often slightly changed as color changes happen which will certainly have a huge impact on the final part shape. If a molder was trying to make each color as close to the same shape (and subsequently the same stability) one solution would be to simply hold the lighter colored runs in the mold a bit longer than darker runs.

The variables involved in shrink rates are not limited to disc color, room temperature and process, they can also change greatly by cooling methods. Discs can be placed top down or top up individually on a table, stacked one on top of another, placed on a rack or in a box or even placed on fixtures. Each of these different methods of cooling will effect the final part shape, some will cause the discs to be less or more overstable.