Der Big Red Max plus upgrade question

[YoMoma]

I’ve purchased the Der Big Red Max and planned to buy the upgrade for it.
I noticed the Vander-Burn kit doesn’t come with a bigger motor mount like other upgrade kits do. That’s no big deal to me. But I do see that it says you can fly bigger motors with this kit.
Are their bigger motors to buy that aren’t past Level 1 cert?

 

[techrat]

DBRM comes with a 29mm Motor Mount which is plenty for a 3" diameter rocket. The "upgrade" kit just replaces the balsa fins and cardboard centering rings with Plywood. But it doesn't make it a 38mm rocket. Having flown mine (which is sorta stock), a G is plenty for this rocket, unless you want it to fly to heights where recovery is a PITA. Now that said, my understanding is that there are "baby H" motors that fit in a 29mm motor mount and people have done their L1 with a DBRM.

FYI; making it a 38mm Motor mount will also likely need to make the motor tube longer as well, which limits your available space to pack a parachute.

 

[techrat]

But I do see that it says you can fly bigger motors with this kit.

I'm a dummy -- I completely misunderstood your question. By that upgrade kit allowing you "bigger motors", what they are saying is that yes, there are more powerful motors that are 29mm than what Estes designed the kit for.

Estes designed the kit to be flown with their F15 black powder motor. What the Upgrade kit claims to do is also allow Aerotech F56 (let say) to be used without the kit ripping itself apart upon launch. Which isn't necessarily true, because you can build DBRM to be fairly stout with the components that come with the kit (check out other build threads here). Mine for example, used the stock pieces although I ended up doing a lot of modifications regardless.

That said, I recently built a Doorknob and *did* use the plywood pieces, so, 6 of one, 1/2 dozen of the other, as they say. The plywood is great for the fins as it's much stronger than the Balsa, but I don't think the rings do anything other than add weight. Either way, it will take a punchier motor if you build it nice and strong.

As for your final question; are there bigger 29mm motors? The biggest 29mm from Estes is the F15, but highest I think you can go on composite is a G-80 before you need to Level-1 certify. FYI however; the G-80 has a lot of initial thrust but I believe a G-40 is longer burning, so for a rocket like the DBRM, you'll likely get more altitude from a G-40...

 

[tsmith1315]

Are their bigger motors to buy that aren’t past Level 1 cert?

To add to @techrat ‘s info- there are 38mm G motors, but not many. And since you can get a full G in 29mm, there’s not much need to upgrade unless you’re prepping for HPR.

Motor mount length isn’t critical. Many motors have one [thrust ring*] built into the aft end of the motor, and you can create one easily with masking tape for motors that don’t. So there’s no need for a motor block in the forward end of the motor tube.


[*edit: left out this part]

 

[lakeroadster]

Are their bigger motors to buy that aren’t past Level 1 cert?

Sure there are... Here's a list of 29mm motors up to a G80, which anything bigger is considered HP.

Go to Apogee Components website and search for 29mm motors.

​

 

[bad_idea]

I’ve purchased the Der Big Red Max and planned to buy the upgrade for it.
I noticed the Vander-Burn kit doesn’t come with a bigger motor mount like other upgrade kits do. That’s no big deal to me. But I do see that it says you can fly bigger motors with this kit.
Are their bigger motors to buy that aren’t past Level 1 cert?

When you say "bigger motor mount" do you mean "longer", or "larger diameter"? In the former case, a longer motor can fit into a shorter motor tube with no problem, so long as there is no motor block in the way. The DBRM does not come with a motor block, so there is nothing preventing the adventurous flyer from stuffing an I200 into it. (Well, maybe the body itself is too short. I fly mine on I200s, but only after I stretched it following a crash that accordioned part of the original tube.)

In the latter case, as @tsmith1315 mentioned, there aren't many 38mm G motors. If you don't intend to fly the rocket on high-power motors, there's not a lot of reason to go larger than 29mm. On the other hand, a 3" tube with only a 29mm seems like wasted space in a way, and there's no reason a DBRM with upgraded fins can't be flown on mild high power motors. If I build another one (or - more likely - the similar Great Goblin), it will probably have swapable motor mounts to fly clusters and larger diameter motors.

FYI; making it a 38mm Motor mount will also likely need to make the motor tube longer as well, which limits your available space to pack a parachute.

For a given impulse, a 38mm is shorter, ceteris paribus. For instance, Aerotech's 38/120 case, with four G reloads available (one of them high-power) is shorter than either the 29/100 case (two G loads, one of them high power) or the 120 case (three G reloads, all low power).

Which isn't necessarily true, because you can build DBRM to be fairly stout with the components that come with the kit (check out other build threads here).
<snip>
The plywood is great for the fins as it's much stronger than the Balsa, but I don't think the rings do anything other than add weight. Either way, it will take a punchier motor if you build it nice and strong.

Agreed, the stock rings are fine. Through the wall fins epoxied to the motor tube and the body can take up any load the stock rings give up.

My inclination these days though is to eschew the plywood kits and just fiberglass the stock balsa fins. We'll see if that bites me eventually. My I-flying stretched DBRM has the fins significantly cut down; perhaps they wouldn't hold up to landings as well if they had remained full size.

FYI however; the G-80 has a lot of initial thrust but I believe a G-40 is longer burning, so for a rocket like the DBRM, you'll likely get more altitude from a G-40...

Pretty sure that on such a heavy, draggy rocket you'll find that the punchier motor will get you more altitude. Certainly that's the case when I sim my DBRM in its original, mostly stock configuration.

Sure there are... Here's a list of 29mm motors up to a G80, which anything bigger is considered HP.

Go to Apogee Components website and search for 29mm motors.

View attachment 624075​

Beware that anything that's over 80N average thrust or is a sparky is a high power motor. That's the majority of CTI G motors, at least six of Aerotech's 28 G motors, and 2 of the 5 Loki G motors.

 

[Scott_650]

I’ve purchased the Der Big Red Max and planned to buy the upgrade for it.
I noticed the Vander-Burn kit doesn’t come with a bigger motor mount like other upgrade kits do. That’s no big deal to me. But I do see that it says you can fly bigger motors with this kit.
Are their bigger motors to buy that aren’t past Level 1 cert?

It can be a bit bewildering sometimes to figure out alternate motors - a quick and easy way to get in the ballpark is Thrustcurve, a fairly simple tool that shows you the general performance for a given rocket for a range of motors. One caveat, TC is kind of HPR oriented so it’s looking for a pretty high launch velocity and/or thrust-to-weight ratio, something to keep in mind. https://www.thrustcurve.org/

 

[John Kemker]

Advice:

Be very careful about what motor you put into your upgraded DBRM. I put an Aerotech G78-10G in my upgraded DBRM. About 300 ft. AGL, it suffered terminal fin flutter, snapping two of the fins straight off at the root. Others tell me they've successfully launched with higher average impulse motors, so it may be a resonance issue. When I build my next, I'm glassing the fin roots, at the minimum. I'd rather see a bit thicker plywood for the fins, TBH.

 

[OzHybrid]

When I built my version, I went straight to fiberglass for the fins. The backward-facing fins are prone to damage just from landing. The large thin flat plate structure of the fins would make them very prone to fin flutter with just a little bit more oomf under it. Who'd do that...
93mm body on G55
Flown on G78 OK too.....

 

[bad_idea]

Be very careful about what motor you put into your upgraded DBRM. I put an Aerotech G78-10G in my upgraded DBRM. About 300 ft. AGL, it suffered terminal fin flutter, snapping two of the fins straight off at the root.

Good point about flutter. By the time I started pushing mine, I'd already cut the fins way down (and glassed them).

 

[Capt. Eric]

I just built a 3" DBRM and am currently building a 4" MDRM (with 38mm mount). I used plywood and cut my own fins for the DBRM. I also got a fin set for the 4" version that involves a plywood core and layer of balsa glued on each side. The balsa was pretty thin and cracked just in handling it. So I cut new plywood outer layers and used them on top of the plywood TTW core. A little heavy perhaps, but feels much more solid. But due to flutter concerns, I'll likely keep these things relatively low and slow. They ain't designed to break any records!

Full disclosure - I haven't flown either one yet.

 

[RobertH3]

I flew MDRM with the Semroc fin kit & rings with fin papering on an H115DM for L1. - Excellent cert with simple recovery.
Easy, inexpensive, lightweight, safe, and stable model that doesn't go too high.
Use 1010 rail buttons with offsets to save your nice paint.
Light weight = cheaper chute and much less costly sport flying.
I did the whole kit except for the 29mmt tube and retainer with Titebond II.
The light weight makes G motors pretty impressive. See pic with G80NT. Looks high power to me...
My brother's cellphone is in mid-air from trying to film an up-the-rail launch.
MDRM also flew on a G72DM and G75M with no issues though the "M" scorched it a bit : )
Mega Max's last flight was on an H135W - a bit much for hollow balsa fins IMO.
It flew well but had hairline cracks in the fillets and is retired. Obviously flutter.
Plywood fins would certainly help.

 

[cls]

Built stock with Titebond, my MDRM enjoys H135s, H128, H97.

 

[dpower]

Built stock with Titebond, my MDRM enjoys H135s, H128, H97.

My stock MDRM (except for Kevlar shock cord) flew on the AT I200 RMS many times. An I205 CATO was too much for it, but she’s rebuilt and ready to fly again. RMS only going forward.

 

[Back_at_it]

I built my Der Big Red Max on the forums here a couple of years back and went with the upgrade kit using plywood fins and rings. It was built with titebond wood glue and has survived without any issues.

I've flown it a number of times on smaller motors like the F67 but it also has three flights on G motors. The first two were G74's but I went big and flew it on the G80 last fall. No issues with stability or fin flutter. Just nice stable smooth flights. On the G80 flight I had the altimeter on board and recorded 1826ft.

Personally, I don't see the need to put anything larger than a 29mm mount in this rocket as it is still somewhat small with large fins. My fear would be fin flutter if I pushed it on anything more than a G motor. If you decide to step up and build the 4 inch Mega Der Red Max, you can fly that thing on H and I motors as much as you like.