It is vital that the final nosecone have a relatively smooth, relatively even coating of ablative; It needs to be smooth for aerodynamic reasons and even for heating reasons. Previously, this was done by slathering on a lot of ablative, and sanding it down until it was roughly smooth, although this method has some issues. Notably, the ablative was very thin near the tip of the nosecone, which might have caused a hole to burn through, destabilize the rocket, and blow up Hermes II.
We've been attempting to find other ways to apply the ablative, including the following
- Nosecone on a spit
- Standard Ablative
We put the nosecone on a spit and applied the unaltered (very thick) ablative to it with squeegees. The result was rather lumpy - Watery Ablative
We tried again with "watered down" ablative (it had 20% acetone in it, not water) with worse results. The resulting coat on the nosecone slid off rather quickly, after being set upright to dry - Pastry Bag
We put the ablative in a pastry bag. This was a bad idea. We made many many bubbles, and the coating was much rougher than using the squeegees.
- Standard Ablative
- Nosecone on the floor
We rolled the nosecone around in the puddle of ablative that we had made on the floor, with surprisingly decent results. We have not done a full coat with method. Ideas for refining it include filling a bath for a paint roller with ablative and rolling it in there - Pottery Nosecone
We purchased a pottery wheel and mounted the nosecone roughly in the center of it with vacuum tape. We then applied some ablative much in the same way as we did when it was on the spit, however the result was much smoother. More tools might make this even nicer, although the limiting factor is definitely how centered we can get the nosecone.
Despite everything we figured out, that as soon as the left the nosecone alone for a couple minutes, the ablative would begin to droop, regardless of the method we used to apply it. This is clearly bad, so we have some ideas to address it
- Using a faster drying epoxy as the base of the ablative, and drying it with a hair dryer
- Applying the ablative in thin coats
- Using thicker ablative i.e. adding silicate or whatever thickener won't ruin the ablative properties