Hey everyone, my university team participates in the SAMPE composite bridge competition (http://www.nasampe.org/page/bridgecontest) and we're currently working on making a carbon fiber prepreg I-beam that will be tested at the competition. I posted a while ago on the equipment forum (http://www.talkcomposites.com/25037/DIY-Curing-Oven-help) asking for suggestions on a DIY oven. We tested our oven, but unfortunately our part is too long and doesn't cure evenly; we followed the prepreg spec curing instructions, but the part of our beam away from the heating element failed to cure in that time. 
Should we try to get a high-temperature fan to help distribute heat? Or can we simply hold the oven at the curing temp for a longer amount of time until the entire component cures (hence the overcooling question)? would that be detrimental to the mechanical properties of the composite (the beam is tested in the competition using a 3-point bend test)
Thanks!!

You really want to get the oven heating evenly, as even though there isn't any real problem in baking the part for longer; the uneven curing will lead to stresses and warping. 

A shrouded oven fan is the best solution, and if the part is really long then you may need to look at a number of elements/fans to get the whole oven heating evenly.

I simply used a 13" steel desk fan with the motor buried in the insulation :-)