ActingLikeAKid
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- Nov 16, 2015
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I figure that rather than dribbling my questions in here and there, I'll just start a build thread for this thing and if I hit a stumbling point, reply to the thread. After a half dozen or so LPR builds as a BAR, I thought "how hard could this be?"
So far ... actually, not bad. Just trying to make sure that I cross all my Ts and dot all my Is.
Here's where we are so far.
1. Inventory all parts. ....Well, yes. I did that. Since most people here are aware of what the contents of a rocket kit look like, I won't bore you with a picture of the parts laid out neatly on the table. Also I didn't feel like clearing it off.
2. Assemble Motor Mount. Done and done. I now realize that if you leave off the aft centering ring, you have a little room to put some epoxy in to do internal fillets. Oops. BUT I did take the time to triple check that the mount would fit in and the fins would fit in as glued. Tacked the rings on with a little Titebond, then when I was sure they were where I wanted, layered on a bead of epoxy. Probably overkill.
3. Filling the spirals! I tried out an idea I had here. I put some thinned CWF in a ziploc bag and cut off the corner. Then I squirted a thick bead of CWF along the spirals, then scraped off most of it with a putty knife. I took pictures...
(this is before I scraped. Scraping went REALLY well as soon as I learned to twist the tube and be careful not to stick my fingers in the CWF. )
I'll add some more of the sanded spirals. Someone (I thought?) suggested 200 grit to knock down the CWF but that seemed REALLY aggressive. I used it on the fin can and it took off the glassine too. Switched to 400 grit for the rest of the body tubes and that worked fine. Also I'm going to hit the fin can with some sanding sealer and go over it again with 400, just so that I have a smoother surface. The ziploc bag trick worked a treat!
4. Shock Cord attachment on the motor mount.
After WAY overthinking this, I settled on using a cable-clamp u-bolt to attach my kevlar string. I like K'tesh's 2-loop method, but I went back and forth for a while on how to attach it. Finally settled on the U-bolt. I'm going to glue in a layer of balsa just to give the bolt a little more to grab on to. I had some balsa from a previous project and cut a bit to fit. Up next: Drilling holes and bolting it in place. This should work well; I'll put the nuts on underneath and add a little epoxy on top. There should be very little force making the loop want to pull back toward the bottom of the rocket, and when the cord tugs, it will sink the nuts into the balsa. Not sure if this makes sense, it's late. Anyway. Pictures.
5. Fin Sanding! This took a while. Taped everything up (which ended up being kind of useless; I think it would have been more critical if I'd been power-sanding). I set a sheet of 100 grit on the table and just went to town. I liked the idea of sanding each side of all the fins, then swapping to the other side, that gave me even bevels. It was helpful for me to count strokes; if you're reasonably good at using even pressure, that will give you pretty good matching results (e.g. if it takes 60 strokes to get the angle you want on the first fin, do 50 on the second and then check to see where you are)
So that's what's done so far.
Up next:
6. Finish sand (200 -> 400) the fins and seal them
7. Install cord loop on motor mount, install kevlar on cord loop.
8. Install motor mount (I plan on using epoxy for this - I'm using it for pretty much everything on this build. It might be a little heavier, but I want something that can survive ....)
9. Install fins. Since I didn't leave off the aft CR, I can't do true internal fillets, so I'll just goop them up with epoxy & do the "double dip" method. Someone posted a homemade "fin guide" that was a sheet taped to a piece of styrofoam; going to copy that to check alignment.
10. Fillet fins.
11. Join body tubes and smooth joints
12. Prime; check finish; fill where I need to.
13. Paint.
14. Launch!!!
Since I'm going baffle-less on this, I think i'm going to pick up a nomex blanket for the chute. Cheap insurance and all that....
Trying to decide on a paint scheme for this. Someone on youtube did a super job with black and white, but I'm not sure I want to do that. I'm thinking a sort of titanium silver with black fins/transition/nosecone would look really slick, but I don't know if you can get a good-looking titanium rattle-can paint (without breaking the bank).
So far ... actually, not bad. Just trying to make sure that I cross all my Ts and dot all my Is.
Here's where we are so far.
1. Inventory all parts. ....Well, yes. I did that. Since most people here are aware of what the contents of a rocket kit look like, I won't bore you with a picture of the parts laid out neatly on the table. Also I didn't feel like clearing it off.
2. Assemble Motor Mount. Done and done. I now realize that if you leave off the aft centering ring, you have a little room to put some epoxy in to do internal fillets. Oops. BUT I did take the time to triple check that the mount would fit in and the fins would fit in as glued. Tacked the rings on with a little Titebond, then when I was sure they were where I wanted, layered on a bead of epoxy. Probably overkill.
3. Filling the spirals! I tried out an idea I had here. I put some thinned CWF in a ziploc bag and cut off the corner. Then I squirted a thick bead of CWF along the spirals, then scraped off most of it with a putty knife. I took pictures...
(this is before I scraped. Scraping went REALLY well as soon as I learned to twist the tube and be careful not to stick my fingers in the CWF. )
I'll add some more of the sanded spirals. Someone (I thought?) suggested 200 grit to knock down the CWF but that seemed REALLY aggressive. I used it on the fin can and it took off the glassine too. Switched to 400 grit for the rest of the body tubes and that worked fine. Also I'm going to hit the fin can with some sanding sealer and go over it again with 400, just so that I have a smoother surface. The ziploc bag trick worked a treat!
4. Shock Cord attachment on the motor mount.
After WAY overthinking this, I settled on using a cable-clamp u-bolt to attach my kevlar string. I like K'tesh's 2-loop method, but I went back and forth for a while on how to attach it. Finally settled on the U-bolt. I'm going to glue in a layer of balsa just to give the bolt a little more to grab on to. I had some balsa from a previous project and cut a bit to fit. Up next: Drilling holes and bolting it in place. This should work well; I'll put the nuts on underneath and add a little epoxy on top. There should be very little force making the loop want to pull back toward the bottom of the rocket, and when the cord tugs, it will sink the nuts into the balsa. Not sure if this makes sense, it's late. Anyway. Pictures.
5. Fin Sanding! This took a while. Taped everything up (which ended up being kind of useless; I think it would have been more critical if I'd been power-sanding). I set a sheet of 100 grit on the table and just went to town. I liked the idea of sanding each side of all the fins, then swapping to the other side, that gave me even bevels. It was helpful for me to count strokes; if you're reasonably good at using even pressure, that will give you pretty good matching results (e.g. if it takes 60 strokes to get the angle you want on the first fin, do 50 on the second and then check to see where you are)
So that's what's done so far.
Up next:
6. Finish sand (200 -> 400) the fins and seal them
7. Install cord loop on motor mount, install kevlar on cord loop.
8. Install motor mount (I plan on using epoxy for this - I'm using it for pretty much everything on this build. It might be a little heavier, but I want something that can survive ....)
9. Install fins. Since I didn't leave off the aft CR, I can't do true internal fillets, so I'll just goop them up with epoxy & do the "double dip" method. Someone posted a homemade "fin guide" that was a sheet taped to a piece of styrofoam; going to copy that to check alignment.
10. Fillet fins.
11. Join body tubes and smooth joints
12. Prime; check finish; fill where I need to.
13. Paint.
14. Launch!!!
Since I'm going baffle-less on this, I think i'm going to pick up a nomex blanket for the chute. Cheap insurance and all that....
Trying to decide on a paint scheme for this. Someone on youtube did a super job with black and white, but I'm not sure I want to do that. I'm thinking a sort of titanium silver with black fins/transition/nosecone would look really slick, but I don't know if you can get a good-looking titanium rattle-can paint (without breaking the bank).