Before answering, go read the instructions for a few fiberglass kits -- you'll find they tell you to sand all surfaces to be bonded.
-Kevin
Since I am a guilty party to the above, I will expound! Having written manuals for a couple dozen , here is why :
First I must think of the full range of building skills that the buyers may OR may NOT have. That means many of the buyers will be building their first fiberglass kit & at the other end of the scale those that are seriously experienced, need no instruction and will build it their own way anyhow....... in between is everyone else. They have built some stuff, but need help in the learning curve of highpower and av-bays. Soooo....
I have also seen too many rockets built with very little or NO attention given to proper surface prep, resulting in epoxy going on CR's,fins, vent band etc. with no sanding. Upon first ejection charge going off the CR pulls out with the recovery gear. A hard landing and fillets or fins pop off glassy smooth , and the list goes on. I/we have seen it all. To alleviate this and not have a super lengthily manual that covers every aspect of building, it comes down to: covering the manufacturers butt, give all surfaces that will be bonded with epoxy a good hard sanding.
Remember this too....for many it will be their first experience with epoxy! Good building skills always require 90% preparation and 10% finish work. Really the only surface not requiring sanding is outer tubes. All inner surfaces, and everything made of G-10 plate does, and that is 90% of a standard build. So it is simpler to just say "sand it all"
So yes there is a grey area here that can be left out, but for beginners and those with mid-level skills it is far better to have them sand & prep the Cr@p out of everything, rather than second guessing, missing the boat and screwing up a build.
When one has reached that level of building nirvana where they don't need help or advice, then so be it. They can fend for themselves, reap the rewards or suffer the consequences of their actions. [build skills]
I prefer to error on the side of caution and can safely say: IF you build it, the way I describe in my instructions, you WILL succeed and have a SAFE, durable long lasting project.
Once again I must also add this disclaimer which many of you are familiar with: "there are many ways to do this, this is just mine/ours, and not saying it's the only or the best, but it will get you a quality end result in a simple, straightforward, sensible manner".
Follow that up with the lifetime Guarantee offered on many of these kits & you have a winning combination.
That's my answer to your question & I'm stick'n too it.LOl :smile:
As far as other authors of instructions, I cannot speak for them.
CJ