lcorinth
Well-Known Member
- Joined
- Aug 5, 2014
- Messages
- 1,022
- Reaction score
- 46
Hey, guys.
I'm having a continual problem with my surface prep. Specifically, filling the spirals on body tubes. What happens is that I use Elmer's Wood Filler, thinned out a bit with water, and then when I go to sand, I end up scuffing up the tube and getting shredded fuzzies from the paper underneath the waxy coating.
I've tried keeping the filler to a minimum, using Chris Michielssen's tip on filling, found here. I've even tried priming first, and this went OK at first. Seemed like I hadn't scuffed anything after sanding. But I went a little too far after the first dry sanding, by trying to get a really smooth surface and damp sanding with a really light touch and 400 grit wet/dry paper, and still, I got scuffs:
As you can see, I also got a few gouges, which I only now just noticed, looking at these pictures again. Not to mention, the spirals are still not completely filled in some spots.
This priming-first thing also feels wrong to me. First of all, I can't fill the seams before gluing anything on, so I have to sand filler off between fins. Also, it feels a bit like a cheat. I know there's no "cheating" in rocket building - whatever works, works. But I know a lot of rocketeers have really great success filling seams without shredding the tubes.
What happens is that I'm trying to get all the filler that stands out from the tube off, because I don't want lumps. But of course, I can't just keep the paper on the filler - a little of the paper will touch the tube. I have no idea where the gouges come from, but I've had that happen before as well.
Maybe I need to switch to an easier-to-sand filler. Anybody have any experience with HobbyLite? Is it easier to work with? I've also thought of trying plastic putty - which TRF user Krusty tells me he uses to fill fins, and that guy builds some beautiful rockets. I'm working on another rocket right now that needs some serious filling. It has a coupler, and when I put the two body tubes together, the glue seized, and there's a very slight gap that must be filled. Not to mention the spirals. That one already has a few coats of gray primer on it. I'm going to wait for your advice before I touch that one again.
I'm also not completely satisfied with my fin filling, but I only have a few trouble spots with that. This tube shredding thing, though... It's really frustrating me.
I know that failure is part of the learning process. The difference is, with other rocketry mistakes I've made, I've learned from them, and now do those parts better - like gluing properly, making nice fillets, etc. With this, I've failed at it five times, made the same mistake, and I don't seem to be getting any better at it. I'm a reasonably smart guy, and I just want to make a nice, smooth rocket. I'll move on to other problems and techniques when I get that down.
So, what am I doing wrong? Help me, Rocketry Forum. You're my only hope.
I'm having a continual problem with my surface prep. Specifically, filling the spirals on body tubes. What happens is that I use Elmer's Wood Filler, thinned out a bit with water, and then when I go to sand, I end up scuffing up the tube and getting shredded fuzzies from the paper underneath the waxy coating.
I've tried keeping the filler to a minimum, using Chris Michielssen's tip on filling, found here. I've even tried priming first, and this went OK at first. Seemed like I hadn't scuffed anything after sanding. But I went a little too far after the first dry sanding, by trying to get a really smooth surface and damp sanding with a really light touch and 400 grit wet/dry paper, and still, I got scuffs:
As you can see, I also got a few gouges, which I only now just noticed, looking at these pictures again. Not to mention, the spirals are still not completely filled in some spots.
This priming-first thing also feels wrong to me. First of all, I can't fill the seams before gluing anything on, so I have to sand filler off between fins. Also, it feels a bit like a cheat. I know there's no "cheating" in rocket building - whatever works, works. But I know a lot of rocketeers have really great success filling seams without shredding the tubes.
What happens is that I'm trying to get all the filler that stands out from the tube off, because I don't want lumps. But of course, I can't just keep the paper on the filler - a little of the paper will touch the tube. I have no idea where the gouges come from, but I've had that happen before as well.
Maybe I need to switch to an easier-to-sand filler. Anybody have any experience with HobbyLite? Is it easier to work with? I've also thought of trying plastic putty - which TRF user Krusty tells me he uses to fill fins, and that guy builds some beautiful rockets. I'm working on another rocket right now that needs some serious filling. It has a coupler, and when I put the two body tubes together, the glue seized, and there's a very slight gap that must be filled. Not to mention the spirals. That one already has a few coats of gray primer on it. I'm going to wait for your advice before I touch that one again.
I'm also not completely satisfied with my fin filling, but I only have a few trouble spots with that. This tube shredding thing, though... It's really frustrating me.
I know that failure is part of the learning process. The difference is, with other rocketry mistakes I've made, I've learned from them, and now do those parts better - like gluing properly, making nice fillets, etc. With this, I've failed at it five times, made the same mistake, and I don't seem to be getting any better at it. I'm a reasonably smart guy, and I just want to make a nice, smooth rocket. I'll move on to other problems and techniques when I get that down.
So, what am I doing wrong? Help me, Rocketry Forum. You're my only hope.