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Potential 3" Estes Der Big Red Max (9721) issue... With easy fix...

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K'Tesh

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For transparency: I've yet to see the instructions for the new 3" Estes Der Big Red Max (9721). There are no build threads, nor any flight reports that have been posted here, or anywhere I'm aware of yet. However, there is a couple of photographs on FB that shows that the shoulder for the nosecone, and it appears to match the Estes Big Daddy nosecone's shoulder.

The Big Daddy seems to have a problem with lawndarts, and I suspect there is a chance that this kit could likely suffer from the same issue if nothing has been done to improve the snugness of the shoulder. The DRM is a kind of draggy rocket, small and lightweight, and if I'm right it'll be prone to drag separation.

One thing that people can do to decrease this risk is follow the instructions carefully. I suspect that the people who are losing BDs to lawndarts did nothing to improve the fit of the shoulder. It's a small, easy to over look step in the instructions... I highlighted it in red for you...

1611436286467.png


Other modifications may be desired to be done by some, but the simplest thing to do would be to use masking tape to adjust the fit. I hope that this might help people with their kits, and prevent any lawndarts from hurting anyone, or damaging/destroying property (including the rocket).
 

MarsFire

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The problem here is not the nosecone per say. It's dimensions are fine and it would fit snugly enough IF Estes would package the kits properly. They are in the habit on their larger kits of taking the nosecone, turning it around, and stuffing it into the top of the body tube. Some of them are stuffed in quite hard. Even the ones that aren't though, will over time cause the body tube to stretch out. Sometimes it's just a tiny bit. Sometimes the nose cone is noticeably sloppy in the tube. The cone should be packed just like all their smaller stuff. At the bottom of the bag or box next to the tube NOT jammed into the tube. At best it could be placed into the bottom of the tube as if that expands a little it doesn't really matter. Epoxy fixes that and Estes centering rings always need sanding to fit properly anyway.

The proper solution here is for Estes to use slightly wider packaging to facilitate not cone jamming their tubes. Second best solution is to teach the workers in Guangdong to put it in the bottom end. And yes, the "in field" solution has always been to use a little masking tape on the shoulder to get the fit just right.

And by the way, yes the DBRM has this problem. At least mine does.

Andrew
 

caveduck

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That's a good fix! The slant cut on those larger nose cones is a problem; there are other threads that discuss it. The slant allows the ejection pressure to vent before the nose cone has fully left the tube. It also creates an uneven frictional force that tends to drive the nose cone askew as it tries to exit. If there is too much friction or the NC is askew very much, there may not be enough pressure left to get the laundry out. Combine that with fairly large internal volume (for Estes), aero pressure on the NC from a late ejection or arcing over, variability in ejection charge oomph, and it's a recipe for trouble. Making the base of the nose cone flat is a really big improvement.
 

CoachSteve

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If you search the Big Daddy threads you will find a few other slanted nose cone fix plans :)
 

Back_at_it

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Cut off the area that has the slant and install a bulk head up in the cone. Doing so will allow you enough room in the body tube to add a baffle so you aren't using a ton of wadding or dog barf.
 

Sluggo

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Here is my fix -


I did this to my Big Daddy too :)
In all due respect, how does that help the snugness of the cone to tube.?? And with all due respect, the fit of the cone and the tube on an Estes is not a lot different than the fit of the cone to the tube on any other rocket is the same. I've built LOC's that also need a little tape around the base of the cone. I agree that placing the cone upside down in the tube causes a little 'expansion' and what I hate about that is it effects the aerodynamics right at the joint. The tube gets stretched and can have a slightly larger diameter than the diameter of the cone. In that case, I sand it down a bit to make a smooth joint.

As for a stronger anchor point for the base of the cone I do this......(though this is not on topic) As you can see, I needed to add tape for snugness just the same. I do on nearly every single rocket I've ever built.!!
An easy test is to pack the shock cord and chute and physically blow through the motor mount to eject the laundry. I've never lawn darted a rocket. I like a snug fit. I think it helps the BP charge build up pressure.
 

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K'Tesh

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In all due respect, how does that help the snugness of the cone to tube.?? And with all due respect, the fit of the cone and the tube on an Estes is not a lot different than the fit of the cone to the tube on any other rocket is the same. I've built LOC's that also need a little tape around the base of the cone. I agree that placing the cone upside down in the tube causes a little 'expansion' and what I hate about that is it effects the aerodynamics right at the joint. The tube gets stretched and can have a slightly larger diameter than the diameter of the cone. In that case, I sand it down a bit to make a smooth joint.

As for a stronger anchor point for the base of the cone I do this......(though this is not on topic) As you can see, I needed to add tape for snugness just the same. I do on nearly every single rocket I've ever built.!!
An easy test is to pack the shock cord and chute and physically blow through the motor mount to eject the laundry. I've never lawn darted a rocket. I like a snug fit. I think it helps the BP charge build up pressure.
Not everyone knows that nosecones need to be snug. They'll attach the shock cord and parachute to the nosecone, and send it. If it's too loose, drag separation can occur exposing that "ramp" and allowing the ejection to vent out the side, instead of deploy the chute.
 

Sluggo

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Not everyone knows that nosecones need to be snug. They'll attach the shock cord and parachute to the nosecone, and send it. If it's too loose, drag separation can occur exposing that "ramp" and allowing the ejection to vent out the side, instead of deploy the chute.
Ya. I understand that a lot of beginners learn the hard way. No front to beginners. I've been there and have learned from many of my own mistakes. That said, your post here helps me understand the true meaning of this thread. Thanks for clarifying it.
 

CoachSteve

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And I will add that the fix I posted above creates a shoulder with significantly more insertion depth (2+ inches in this case) than the ramped version - that by its self increases the friction of the fit by simple product of force over given surface area. Even a week fit gets pretty "snug" as the area increases. Additionally, if some drag separation does start to occur, the nose has to separate a long way before it truly separates completely. I will confirm that my Big Daddy, Doorknob, 3" Red Max, MistyKim and Were's Waldo all are done this way and none need friction tape. I will concede though that a little tape on a shoulder is such a common practice that I never even thought about looking for rocket parts that are so precision that it is never necessary :)
 

Sluggo

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Coach.... How do you build up the 'coupler' to be the same diameter of the shoulder.??
 

CoachSteve

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The shoulder is the actual shoulder of the nose cone - I just cut the bottom and ramp section out, I then make a section of a cardboard coupler to fit "inside" the shoulder of the nose cone (maybe 2.5" of coupler) split down the side and trimmed to fit in. then I fill in the little wedge section with a half circle-ish piece or 2 cut from the coupler leftover section to build up to the thickness of the actual cone shoulder. Then glue a bulkhead inside the new coupler section, Add nose weight if needed, install a eye bolt of some type and then epoxy the whole deal into the nose - easy peasy :)

Ok - not super easy but I like to tinker and modify so this is fun for me :)
 
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CoachSteve

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Now I just need to find somone willing to part with the decal set for the new 3' version so I can have the missing decals from the kit (any stickershock users out there that have the original decals they might be willing to let go of? :)
 

CoachSteve

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Huge shout out to James Duffy - he is graciously sending me some decals - this forum is so great :)
 

K'Tesh

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I could use some extras decals.
 
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