Build Thread : Der Big Red Max

[techrat]

Probably already covered here ad infinitum; but my take is going to make it a little different. For starters, I'm fortifying the airframe.
DBRM comes with a 3" pre-slotted tube, but I am concerned it's so thin.

So, using a process I learned about on another thread here, I'm using Quasi-Glass to beef it up a little. Quasi-Glassing is like fiberglassing a cardboard tube, except instead of using fiberglass cloth and epxoy, we're using ladies nylon panyhose and Minwax "Polycrilic". Cut one leg off the lederhosen stretch it over the body tube, and knot the excess at the top. Then apply the Polycrilic with a foam brush, making sure you don't leave any dry spots. I gave mine two coats just to be safe. When it's dry and hardened, the nylon + polycrilic gives the tube a little more crush resistance without adding that much weight.

Later, after I've added the fins, we'll also brush on a thin layer of laminating epoxy to finish up, as the nylon currently gives the tube a rough-feeling surface but that's for a later step in this process. I'm hoping to keep the weight down enough that I can fly this on E, F and G motors. I am also simultaneously building a Super Big Bertha, using this process as well.

 

[Bruiser]

I've used the quasiglass process on three of my rockets so far, all three inch tubes. People may say it doesn't add much strength and I won't argue that even though I believe it does. I also like the nice, smooth surface you get with the process.

I have plans to build a 2" rocket soon and I am wondering if I'll be able to stretch the nylons enough so they are tight against the body tube.

I'm looking forward to following your build.

-Bob

 

[techrat]

Cut open the fin slots on the Body tube and sanded. I also applied thin CA to the each "open" end of the tube. Once this dried/hardened, it made the nylon easy to cut away with an X-acto knife, as well as sand down any remaining bits. At this point, I'm ready to move ahead with the motor mount.

 

[dpower]

Probably already covered here ad infinitum; but my take is going to make it a little different. For starters, I'm fortifying the airframe.
DBRM comes with a 3" pre-slotted tube, but I am concerned it's so thin.

So, using a process I learned about on another thread here, I'm using Quasi-Glass to beef it up a little. Quasi-Glassing is like fiberglassing a cardboard tube, except instead of using fiberglass cloth and epxoy, we're using ladies nylon panyhose and Minwax "Polycrilic". Cut one leg off the lederhosen stretch it over the body tube, and knot the excess at the top. Then apply the Polycrilic with a foam brush, making sure you don't leave any dry spots. I gave mine two coats just to be safe. When it's dry and hardened, the nylon + polycrilic gives the tube a little more crush resistance without adding that much weight.

Later, after I've added the fins, we'll also brush on a thin layer of laminating epoxy to finish up, as the nylon currently gives the tube a rough-feeling surface but that's for a later step in this process. I'm hoping to keep the weight down enough that I can fly this on E, F and G motors. I am also simultaneously building a Super Big Bertha, using this process as well.

Shouldn‘t it be called leder-glassen? Nothing wrong with beefing up the airframe, but there‘s no need for concern, it’s plenty strong for mid-power motors. If flying on high thrust G motors, the the large fins are likely to fail before the airframe. Any plans to strengthen the fins?

The Super Big Bertha will handle a G motor built stock. I had a recovery failure before I was able to try an H.

Anyhow, we can never have too many build threads!

 

[StreuB1]

I wonder what the difference would be if you replaced the minwax with epoxy from the get-go?

Very interesting though using nylons as a reinforcement substrate! I have an OOP Big Daddy that I want to build and would like to make it a bit more robust. I might try this along with papering the fins.

 

[StreuB1]

Shouldn‘t it be called leder-glassen? Nothing wrong with beefing up the airframe, but there‘s no need for concern, it’s plenty strong for mid-power motors. If flying on high thrust G motors, the the large fins are likely to fail before the airframe. Any plans to strengthen the fins?

The Super Big Bertha will handle a G motor built stock. I had a recovery failure before I was able to try an H.

Anyhow, we can never have too many build threads!

Agreed. I would replace the fins with 1/8" ply or at least paper them.

Look into the LaunchLab plywood upgrade kit for this rocket. Its like $14 and BEYOND worth it!! You get plywood fins, rings, etc. I have two and both handle 180ns H reloads with ease but also flies well on E's, F's, and G's. F's are the happy reload in mine. The 29/60 and 29/100 cases are perfect for this rocket for just "fun" flights.

 

[DigBaddy]

In a case like this where there may be a desire to keep things light, I like laminating the balsa fins with 1/64" ply. Once set, they're quite strong and don't weigh much; way less than full ply.

Beefing up the BT on this seems like extra weight that isn't necessary....but I have not done so with this method and really shouldn't comment on that

Edit, my DBRM has papered fins and stock centering rings. Fell without a chute onto gravel, just a few scuffs on the fins is all...but I'm not sure I want to put punchy Gs or Hs in it....

 

[techrat]

Nothing wrong with beefing up the airframe, but there‘s no need for concern, it’s plenty strong for mid-power motors. If flying on high thrust G motors, the the large fins are likely to fail before the airframe. Any plans to strengthen the fins?

Absolutely! The fins are going to be papered, and when I coat the airframe with the laminating epoxy, the fins are getting covered with that as well. So, once finished, rocket should be as strong if not stronger than my "Big Daddy", which has been extraordinarily tough thus far with just a coating of fiberglass epoxy on the body tube and fins.

 

[techrat]

OKay.... Here's where things start to go sideways on this build. First image is an assembled balsa fin. Looking at how thin it is and how it's assembled, I should have cut myself off there and just ordered the Plywood fins and centering rings. But I soldiered on, papered the fins and things just seemed to get worse. I can say they are not warped, thanks to a few days under a heavy book, but the paper has crinkled. I think there was too much water in my glue or I just used too much, either way, I'm now looking at either sanding and re-doing them, just sanding them and then laying on epoxy, or just throwing them away and going plywood.

I've come this far, and it's just a $40 kit, so, I am going to sand them and add a layer of epoxy on each side to strengthen them some more. Now, it needs to be pointed out that even with the paper as it is, the fins are already twice as strong as they were, they just don't look great. They are straight, which is what's important. I think a layer of epoxy will save this, make 'em smooth, and they'll be fine.

 

[Back_at_it]

OKay.... Here's where things start to go sideways on this build. First image is an assembled balsa fin. Looking at how thin it is and how it's assembled, I should have cut myself off there and just ordered the Plywood fins and centering rings. But I soldiered on, papered the fins and things just seemed to get worse. I can say they are not warped, thanks to a few days under a heavy book, but the paper has crinkled. I think there was too much water in my glue or I just used too much, either way, I'm now looking at either sanding and re-doing them, just sanding them and then laying on epoxy, or just throwing them away and going plywood.

I've come this far, and it's just a $40 kit, so, I am going to sand them and add a layer of epoxy on each side to strengthen them some more. Now, it needs to be pointed out that even with the paper as it is, the fins are already twice as strong as they were, they just don't look great. They are straight, which is what's important. I think a layer of epoxy will save this, make 'em smooth, and they'll be fine.

I ordered my kit when they were first released and was excited. When they arrived I ripped the first box open and started looking at parts. Was happy until I got to the fins.

Once I looked at the fins I was disgusted. Threw everything back in the box and threw the whole thing in the corner. Figured I'd just cut my own from sheets of Basswood and move on. Later that day someone posted a link to Vanderburns old site for something completely different. While I was on his site I found the plywood replacements and ordered a set for all three of the kits I bought. SO MUCH BETTER!!

If you don't want the weight of Plywood I would go with Basswood. HL has sheets large enough to cut the fins from and it's a very simple shape to cut.

 

[techrat]

Once I looked at the fins I was disgusted. Threw everything back in the box and threw the whole thing in the corner.

I accepted the challenge to build this when I ordered the kit. I'm going to get through this, and if I'm not happy with the result, I can always order another kit and the plywood fins. My understanding is that I've already done enough Estes-bashing on TRF, so I'm getting through this and I'm going to make it work. I've had worse kits than this, so sometimes the best course of action is to just keep at it.

 

[Rex R]

I've used a 1" foam paint brush to apply a very thin layer of white glue,plus it keeps your pinkies clean. Then use a 5/16" rod ( like a rolling pin) to roll the paper skin down (work from the root edge to outside edge), clean up the glue that gets squeezed out. Flip the fin and repeat, place on a wire rack and let dry. Any warps can be ironed out.

 

[Hobie1dog]

The sight of balsa makes me wanna but it's something I have to deal with occasionally. I don't have any concern about the weight of 3mm plywood over balsa as I'm not an altitude junkie, thinking that i need to brag about how high my rockets go.
post up plenty of pics for us.

 

[techrat]

I don't have any concern about the weight of 3mm plywood over balsa as I'm not an altitude junkie, thinking that i need to brag about how high my rockets go.

I'm not an altitude junkie either, I prefer low and slow -- but my thinking with this Red Max *AND* the Super Big Bertha I am simultaneously building is to make them strong and as light as possible, so I can still fly these on "E" motors as well as F and G -- E motors would require the 24mm to 29mm adapter, but I have that already. I've flown LOC Precision kits, and while they are tough as nails, they are also pretty heavy -- I doubt my Scout or Sandhawk could get off the rail with anything less than an F.

 

[CalebJ]

I'm not an altitude junkie either, I prefer low and slow -- but my thinking with this Red Max *AND* the Super Big Bertha I am simultaneously building is to make them strong and as light as possible, so I can still fly these on "E" motors as well as F and G -- E motors would require the 24mm to 29mm adapter, but I have that already. I've flown LOC Precision kits, and while they are tough as nails, they are also pretty heavy -- I doubt my Scout or Sandhawk could get off the rail with anything less than an F.

The SBB (built stock, at least) flies surprisingly well on a D12-3. Just enough time to get the parachute out for a graceful landing near the launch pad.

 

[techrat]

OK, preparing to add a coat of laminating epoxy over the body tube and fins -- now remember that the body tube has the nylon on it and several coats of the Polycrylic already, but still feels rough, so the laminating epoxy is to fill in the nylon more and seal up everything, eliminate sprials as well as protect the soft balsa. Super Big Berta is shown in this picture as that project is a little further along than Red Max, but in this you see the 2-part epoxy, a cut-down Taco Bell cup as the mixing cup, some craft sticks for stirrers, and a 1" wide paint brush as the applicator. NOT SHOWN is the Acetone I needed to thin down the epoxy, as it was initially too thick to paint on. Might be due to the cold weather, it's only about 60 degrees in my house. I'll post of a photo once it's all dry. Due to being thinned, it took about 10 hours to dry to the touch, and it's probably still not hard. It may take 48 hours to completely cure.

 

[Scott_650]

I'm not an altitude junkie either, I prefer low and slow -- but my thinking with this Red Max *AND* the Super Big Bertha I am simultaneously building is to make them strong and as light as possible, so I can still fly these on "E" motors as well as F and G -- E motors would require the 24mm to 29mm adapter, but I have that already. I've flown LOC Precision kits, and while they are tough as nails, they are also pretty heavy -- I doubt my Scout or Sandhawk could get off the rail with anything less than an F.

Before I stretched my SBB after a bit of a lawn dart landing it really liked adapted Estes E12s - it still flies ok, just not as nice as when it was a bit shorter and lighter. There’s two DBRMs on the shelf for future builds - one will be with original parts (other than papering the fins) while the second will get some plywood fins/rings and a different color scheme.

Thanks for the build thread - some good techniques being shown and discussed.

 

[techrat]

OK..... Motor Mount glued together. I took care NOT to get any glue where the fins go into the slots, so no glue "bumps" will interfere with the fitting of the fins during the assembly. There will be plenty of glue in there when the time comes to stick the fins in. Next image shows my papered "sanded" fins. Even with the bumps sanded away, it's still plenty strong, and once the epoxy lamination in done, they should be able to survive almost anything. Third image is a dry "test fit" -- it should be noted that the Estes "pre-slotted" tube isn't pre-slotted enough to actually get the balsa into the tube. Maybe Estes assumed you'll be sanding the fins. I did not bother as I was papering them, and will be laying epoxy over them for a smooth finish. Besides, on a kit like this, I need every micromilimeter of balsa I can get. So, I trimmed a bit with the X-acto into the slots and sanded and sanded and then sanded some more, until the fins go into the tube.... Success!!

 

[Tractionengines]

The SBB (built stock, at least) flies surprisingly well on a D12-3. Just enough time to get the parachute out for a graceful landing near the launch pad.

The SBB is also ok on the Quest D22-4 and really well on the E23-4. IF its not overbuilt into a tank.
( Just make sure you SIM it with your build weight, to check speed off rail and altitude. The D22 starts harder and actually has better lift-off. )

 

[techrat]

The SBB is also ok on the Quest D22-4 and really well on the E23-4. IF its not overbuilt into a tank.

Well, I already know from experience that the E30-4T will push hard enough to get this rocket off the pad safely, unless by the time I'm painting its more than 500 grams, but I'm surprised to hear that the D is possible as well. Quest "D" motors are 18mm if I recall, so, double adapters needed to try that! I'll look into it once I weigh this monster I am creating. I think Bertha will end up heavier than Red Max, as it has one more fin, and I've added a payload bay that extends the overall rocket to 42 inches tall. But Red Max requires more weight in the nose, so, this will be a toss-up until they are both painted.

 

[CalebJ]

It's on the recommended engines list.
https://estesrockets.com/product/009719-pro-series-ii-super-big-bertha/

 

[techrat]

It's on the recommended engines list.

Yes, but that assumes "stock" construction. I haven't built a kit as per the instructions since my original Big Bertha. My next kit thereafter was "Big Daddy", where I slathered the airframe and fins in fiberglass resin and added at least 100 grams of overall weight -- my Big Daddy as a result just barely gets off the pad on a D12, it really prefers "E" and up, and flies best on Quest E26 motors, where it goes high enough to impress the crowd, but not so high that I don't get it back.

 

[Tractionengines]

Quest "D" motors are 18mm if I recall,

While Quest does have 18mm "D" motors. [ The D16 & D20 ] Those are not FULL "D" motors, and will NOT work here. The Quest D22 is a 24mm motor and IS a FULL "D" impulse.

 

[techrat]

While Quest does have 18mm "D" motors. [ The D16 & D20 ] Those are not FULL "D" motors, and will NOT work here. The Quest D22 is a 24mm motor and IS a FULL "D" impulse.

Ah so, desu-ne... I will have to look into that.

 

[4regt4]

I've used a 1" foam paint brush to apply a very thin layer of white glue,plus it keeps your pinkies clean. Then use a 5/16" rod ( like a rolling pin) to roll the paper skin down (work from the root edge to outside edge), clean up the glue that gets squeezed out. Flip the fin and repeat, place on a wire rack and let dry. Any warps can be ironed out.

Spent motor casings work great for pressing the paper down flat.

Hans.

 

[techrat]

Added Epoxy fillets because I wasn't 100% happy with how the fins were attaching to the body tube. Once these dry, it's down to the basement for the laminating epoxy on the body tube and fins. I'm having to thin it down with acetone again, so, probably more than 1 coat needed and 24 hours dry time.

 

[techrat]

And by the way......... I hear a lot of people complain about the Super Big Bertha fins. In the last 2 weeks, I've done both Bertha Fins and this Red Max, and Bertha's came out much better. They are very light and strong on Bertha, but I feel these on Red Max are far too thin. If I could jump back in time 1 week, I think I should have opted for the Plywood fins. That said, I'm already here, all I can do is say I'll know better next time.

 

[dpower]

And by the way......... I hear a lot of people complain about the Super Big Bertha fins. In the last 2 weeks, I've done both Bertha Fins and this Red Max, and Bertha's came out much better. They are very light and strong on Bertha, but I feel these on Red Max are far too thin. If I could jump back in time 1 week, I think I should have opted for the Plywood fins. That said, I'm already here, all I can do is say I'll know better next time.

Agreed the BB fins are much stronger, and the thickness is better scale to the standard version. That said, being 3" with a huge NC, the DBRM needs to stay very light to fly well on E16 & F15 motors, so I understand why it was done this way. They're plenty strong for the up part, but over time probably won't withstand hard landings. Well, I have 2 more, so may try papering for additional strength with minimal weight gain (and cost). Better would be 1/16" balsa skins, but that'll cost a bit more.

 

[techrat]

OK, after two very thin coats with laminating epoxy, I performed a quick and light sanding with 150 grit and then 240 to remove the airbubble "bumps" that came from applying the epoxy with a paintbrush (or perhaps the bubbles formed due to acetone), but either way they sanded easily enough. I'll give it a final sanding before painting, and I'll try and use filler primer to fill any low spots in the epoxy. we'll see how it goes.

One of my fins still managed to warp badly, as I said, this balsa is way too thin. I should have bought a thin sheet of balsa, and cut a buttress piece with the grain going 90 degrees from the grain of the fin, and glued that to each side of the fin, but, what's done is done. Interestingly, I've got a slight warp on the next fin over, but going the opposite direction, so, perhaps they will cancel each other out and it'll still fly straight. Who knows?

Next steps: Shock cord/Chute, Motor retainer, and a paint scheme. While I'm tempted to do the traditional red & black, I'm also thinking of the "Mad Max" MFP paint scheme for the police vehicles in the first film, which was Yellow and Blue with a Red & White stripe. Then I could call this "Der Big Mad Max"... Either way, almost done.

 

[techrat]

Forgot all about the Nosecone, however, the Estes instructions want you to add noseweight with the 4 pieces of clay they provide. So, I took this opportunity to cut off half the shoulder for easier access. I shoved in the clay with a dowel, and once I was satisfied it was squished-down as far as I could get it, I added a few drops of water with a syringe, and then squeezed in enough gorilla-glue to hold that clay in place. Once the glue reacts with the water, it should form a layer about 1" thick above (or below depending upon the nose orientation) the clay, securely holding it in place.

I'm also building a wooden bulkhead to glue into place once that's all dry, and we'll add a welded eyebolt with some washers and epoxy the flipside to make sure the nut never comes out. But that's all after the Gorilla Glue sets.