Queen Bertha
Here's two projects I'm working on. The first is "Queen Bertha". I used the 3-ply balsa fins as provided, and did not opt for the plywood upgrades -- keeping it somewhat light. However, I did what is known as "Quasi-Glass" it. This is where you take Ladies Nylon Stockings, stretch it over the Body Tube, and then apply Minwax Polycrylic to adhere the nylon to the BT. After the rest of the rocket was assembled, I then gave the entire rocket (not including the payload bay/nosecone) a coat of laminating epoxy to seal and strengthen the BT. This fills in the rest of the nylon, eliminates tube spirals and the split where the two BT-80's meet. Weather permitting, I should be able to bring this to the Feb launch and fly it.
Next is a "Der Big Red Max" (better name for it is still in progress) -- again, I used the quasi-glass procedure to strengthen it without adding that much weight. However, this rocket's 3-piece fins warped on me when I tried to paper them for more strength. So, I added some scrap balsa pieces with the grain running perpendicular to the direction of the warp, epoxied them onto the fins, and then sanded them a bit to "blend" them into the existing fins. Estes really should consider re-working this kit to make the two-ply fins standard, or making the plywood fins standard as the 1-ply balsa doesn't cut the mustard. Because of the troubles encountered building this kit, I expect the earliest I'm flying this rocket is going to be March. Plus, I still need to think of a good paint scheme and a better (aka attempting to be funny) name.
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Interesting. Kind of a poor man's fiberglass technique.
To avoid warped fins, I make sure to apply glue, sealer, whatever to both sides of the fins at the same time. A little warping shows up when wet, but after drying it is minimal. If it warps more than expected, while still wet, I'll put wax paper on both sides, then place books or boards on top to press it flat and let it dry overnight. That usually does the trick.
Regardless, I think doubling up on the fins for this size rocket with such "protruding" fins is a good idea anyway. They just look very prone to damage. Plywood is better. Fiberglass is better still. This issue is one reason I haven't jumped on the Der Red Max or mega Goblin bandwagon.
Name. How about "Der Blue Brian" or any other color/name combo you favor.
Looking forward to seeing them fly!
Quote from Brian C. on January 5, 2023, 11:24 amHowever, I did what is known as "Quasi-Glass" it. This is where you take Ladies Nylon Stockings, stretch it over the Body Tube, and then apply Minwax Polycrylic to adhere the nylon to the BT.
What if you get a run in your nylon stockings? 🤪
Seriously, there are several companies that make fiberglass tube stocking. Â You can get varying weights. Â I'd think 2oz. fiberglass would be a weave pretty close to your nylon stocking. Â I've repaired paper tubes with a layer or two of 2oz. fiberglass. Â It's very thin, so it doesn't impede things like nosecones; it's also very strong.
Soller Composites has sleeves/stockings you might wish to check out.
Quote from Eric Becher on January 5, 2023, 11:56 amInteresting. Kind of a poor man's fiberglass technique.
Yes, well, kind of a fiberglass replacement technique for lightweight mid-power rockets. It's important to note that for the laminating epoxy step, I thinned down the epoxy with acetone. Epoxy doesn't exactly "flow" in this cold weather like it does in 80 degree heat, and I wanted to be able to apply it with a brush. This kept things nice and thin and light. Queen Bertha tips the scales at 420 grams, just under 1 pound, which still allows me to fly it on most composite E motors. I believe an Estes black powder E12 gives me just barely a 3x thrust to weight ratio. But to be safe I am going to use an E30-4T for the first flight.
Brian, I am intrigued by the 2oz fiberglass cloth. I'll have to look into that, as I'm trying to apply high-power techniques and practices into mid-power rockets Eventually, I'm going to go for L1 (maybe later this year), and I'd like to be able to know as much as possible by that time.
And yes, despite a pile of books on those fins for Red Max, they still managed to warp (maybe they were not 100% dry when I removed them), but either way I have mitigated the issue with the second ply. This will either work, or I'll end up rebuilding the whole thing with the plywood upgrades.
Quote from Brian C. on January 5, 2023, 3:30 pmBrian, I am intrigued by the 2oz fiberglass cloth. I'll have to look into that, as I'm trying to apply high-power techniques and practices into mid-power rockets Eventually, I'm going to go for L1 (maybe later this year), and I'd like to be able to know as much as possible by that time.
I got the FB fabric I have from Jackson Hobby Shop. Â Sadly, it's closed now. Â However, you can purchase it on-line. Â Even Amazon has it.
With it barely warm enough to paint, I was able to jump ahead on the Red Max project. Far from perfect, and I have no intention of perfection given all the issues I ran into on this build. I prefer a "battle scarred" rocket that looks like it's already seen its fair share of use, so I left this one out in the rain, and it became "DER RUST MAX" with a dull black/orange rusty color and a distressed look to it. We all know the rocket-eating trees prefer glossy, brightly-colored rockets, so I am guaranteed to get this one back every time.
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Nice! 😲
I like the der rust max name, lucky to paint outside
if your goal was to keep this model lighter, then I would have skipped the nylon etc
What epoxy did you use and had to thin? There is a finishing epoxy which is brushable, very thin. I used it to add FG to my V2 fins. Finishing epoxy is not for strength
when you laminated the fins, did you have a weight on them for some time? A must to do both sides simultaneously
poohbah’s comment on using thin CA in balsa to strengthen n seal might be another technique
where do you plan to fly your L1? Not in belmar I hope. Â Using your der rust? Motor mount dia?
typically, level 1 wouldn’t need the FG or nylon . I didn’t on mine, L1 or L2, plywood fins w epoxy only
good luck🚀
I'm currently building a Star Orbiter, and after papering the fins (this time with cardstock); I still ran into issues because after 2 days under a pile of books they were still not dry enough to not warp, so, I decided to try the soaking them in CA trick that Brian recommended, and that worked better than expected. I will have to stock up on CA in the future, although I am seeing that my days of balsa are waning, I seem to be building bigger and bigger which means plywood in my future.
Heck no, not doing my L1 with Der Rust Max (even the tiniest H motor might rip it to shreds), I have another, much larger build in progress for that. The whole Nylon and finishing epoxy thing was to try out the technique and see what it does. It doesn't add that much weight and seems to improve durability, but, since I haven't flown either of these birds yet (Feb 5, where are you?), that remains to be seen.
Based also on Brian's recommendation, I just bought some very lightweight fiberglass cloth (1.5oz), and will be trying that at least on the fins of the rocket I am hoping to L1 with, which is currently named "Moon Dog", will have a NASA/Apollo paint scheme, and is really built from the BMS 3" "School Rocket" with a few mods.