EZ-DD Build

[Buckeye]

The nose cone pulled out of the screws. No damage to the nose cone. The problem is that the School Rocket tube is rather thin. Our mentor, Jake suggested epoxy a thin washer to the outside of the tube. I’ll try this.

My MPR 2-stage is the School Rocket. I used brass shims.

https://www.rocketryforum.com/threads/first-electronic-staging-mpr-build.182599/post-2536659

 

[SkyDart]

Oops !

I didn't see your pics @Sooner Boomer !

Did @SkyDart post pics of his nozzle too ?

Sorry !

-- kjh

I hadn’t thought about looking until now but when I did, one side of the nozzle is eroded more than the other. It’s hard to see in the photo but lock at the top left compared to the bottom right

 

[Art Upton]

The cardboard is too thin so I'll just stick with Scotch tape.

There is something I think about Vinyl sign wrap or Trim MonoKote strip that I have used on rockets helps the Pin holes not expand.

Here is the Chute cannon that is shared between the NOS Hybrid rocket behind it, and my Mach burner ScatKat with the ACME 38mm fin can slotted into the 54mm LOC tube.

You can see the mark from electrical tape I used to cover the nylon screw head, since it was a better color then yellow masking tape, and the hole is just fine with years of use and abuse on this chute cannon.

Also see the entire body tube of that NOS rocket was wrapped in Black Vinyl. Under it you can see stress just above the fin can, from some hard landings on a gravel road at Gate 3 & 14 MIS that the wrap is helping it not get worse so far. The fins are bare plywood with Yellow Vinyl covering them. Fin sealer [not fillet] is silicon sealer to keep air out of the TTW fin can, starting to get some age on it.

You can see the hole that was/is used for the 2-56 pin(s) in the faux carbon fiber wrap on the chute cannon. The wrinkle in the chute cannon is the wrap with a nick in it, the tube is still fine still.

When I am done with my 3" Estes tube rocket based on Levithan, I will be putting a 2" vinyl strip up at the top of the tube to match the nose cone red. I bet it beefs up the thin Estes style tube as well.

 

[thzero]

The cardboard is too thin so I'll just stick with Scotch tape.

I use scotch tape with my BT-70 and BT-80 based dual deployment rockets (they run on eggtimer quantums). works good enough.

 

[Ronz Rocketz]

My MPR 2-stage is the School Rocket. I used brass shims.

https://www.rocketryforum.com/threads/first-electronic-staging-mpr-build.182599/post-2536659

I bought this and will try it. Lots of ideas from everyone.

 

[cerving]

...
Now the Estes 3" tube is a thinner tube then LOC uses , as you pointed out. I had never heard of using Cellophane tape until the EZ-DD kit before, but your doing something new.
...

Actually, I've been using cellophane tape for a long time... basically for about 13 years, since I started doing dual deployment with Estes rockets when I was a L0. I tried hardening the tubes with CA, brass shims, etc., and found that the tape was a lot easier, and very reliable as long as you got the tape to BP ratio correct.

 

[Ronz Rocketz]

I'm interested in trying the nylon screws because (A) I discovered I already have the nylon screws and (B) nylon screws are recommended by the Constitution and the Magna Carta as the way to manage the NC during DD so I'm curious if I can make it work with the EZ-DD.

What we do know is to NOT use a full charge on the main.

 

[cerving]

Yup, I filled up the Main charge well the first test flight and blew the nose cone to bits. 1/2 gram in the Main is fine, I'm leaning towards recommending 0.3 grams in the Drogue but I need to do a little more testing. This is personally tough for me because I'm in the "Blow it out or blow it up" camp, but I'm used to fiberglass... the EZ-DD was really the first non-Estes cardboard rocket that I had built in several years.

 

[thzero]

Yup, I filled up the Main charge well the first test flight and blew the nose cone to bits. 1/2 gram in the Main is fine, I'm leaning towards recommending 0.3 grams in the Drogue but I need to do a little more testing. This is personally tough for me because I'm in the "Blow it out or blow it up" camp, but I'm used to fiberglass... the EZ-DD was really the first non-Estes cardboard rocket that I had built in several years.

I've used .3 in Estes 2.6" tube for drogue.

 

[Sooner Boomer]

Yup, I filled up the Main charge well the first test flight and blew the nose cone to bits. 1/2 gram in the Main is fine, I'm leaning towards recommending 0.3 grams in the Drogue but I need to do a little more testing. This is personally tough for me because I'm in the "Blow it out or blow it up" camp, but I'm used to fiberglass... the EZ-DD was really the first non-Estes cardboard rocket that I had built in several years.

I don't feel bad now, that's exactly what I did. Drogue charge went off with enough force to yank the chute and nosecone off, broke the back end off the nosecone. Somehow broke the drogue shock cord. That was a challenge to fix. The original instructions don't have anything about cellophane tape on the nosecone.
I think you're right with 0.3/0.5 charges.

 

[Ronz Rocketz]

I don't feel bad now, that's exactly what I did. Drogue charge went off with enough force to yank the chute and nosecone off, broke the back end off the nosecone. Somehow broke the drogue shock cord. That was a challenge to fix. The original instructions don't have anything about cellophane tape on the nosecone.
I think you're right with 0.3/0.5 charges.

Fortunately, I had a bulkhead available to repair mine.

 

[Sooner Boomer]

Fortunately, I had a bulkhead available to repair mine.

View attachment 672061

Never found the nosecone. Saw it fly off into tall grass. I was really mad at myself, and didn't look too hard.

 

[cerving]

I don't feel bad now, that's exactly what I did. Drogue charge went off with enough force to yank the chute and nosecone off, broke the back end off the nosecone. Somehow broke the drogue shock cord. That was a challenge to fix. The original instructions don't have anything about cellophane tape on the nosecone.
I think you're right with 0.3/0.5 charges.

We added the bit about the cellophane tape after about a month... if you were an early purchaser, the Flight Manual that you may have downloaded didn't mention it. It may have overstated the BP, too.

 

[Ronz Rocketz]

We added the bit about the cellophane tape after about a month... if you were an early purchaser, the Flight Manual that you may have downloaded didn't mention it. It may have overstated the BP, too.

Are you considering making the powder cups smaller?

 

[SkyDart]

Are you considering making the powder cups smaller?

I think they are fine like they are. I think .3g to .5g for main and .5g to .6g for apogee are good numbers. Having a slightly oversized well helps with prep in the field and you just fill it the rest of the way with dog barf. I had a good ground test and two good good flights with these numbers and the math maths well. I will keep flying with this approach until I have a failure but with what I have seen so far I don’t expect the size of the charge or the charge wells to be the point of failure.

 

[cerving]

Are you considering making the powder cups smaller?

These are the same wells that we sell with the Apogee Easy Mount. We've thought about it... no plans quite yet. I'd rather make them a little oversized then undersized... you can always fill up the extra space with dog barf.

 

[Ronz Rocketz]

I think they are fine like they are. I think .3g to .5g for main and .5g to .6g for apogee are good numbers. Having a slightly oversized well helps with prep in the field and you just fill it the rest of the way with dog barf. I had a good ground test and two good good flights with these numbers and the math maths well. I will keep flying with this approach until I have a failure but with what I have seen so far I don’t expect the size of the charge or the charge wells to be the point of failure.

I agree but I think Cris is saying it should be the other way around.

 

[thzero]

I agree but I think Cris is saying it should be the other way around.

Ground test, just don't go by what a document says.

 

[WizardOfBoz]

I use scotch tape with my BT-70 and BT-80 based dual deployment rockets (they run on eggtimer quantums). works good enough.

So do you pre-perforate it? Or just adjust the BP charge to ensure enough pop to break the tape? Any rule of thumb regarding the BP charge? Thx.

 

[cerving]

We just revised the EZ-DD Flight Manual...

* Use three 3/8"-wide pieces of SCOTCH TAPE (***NOT*** masking tape) to hold the nose cone on.
* Use 0.3 grams of BP in the APOGEE charge well, pack it to the top with dog barf before taping it up.
* Use 0.5 grams of BP in the MAIN charge well, pack it to the top with dog barf before taping it up.

This seems to work every time.

 

[velocipedecowboy]

What is the difference between scotch tape and masking tape that makes a difference?

 

[lr64]

A bit of extra space might be handy. The EZDD would probably require an ounce of the BP I have, if that much existed.

 

[4regt4]

We just revised the EZ-DD Flight Manual...

* Use three 3/8"-wide pieces of SCOTCH TAPE (***NOT*** masking tape) to hold the nose cone on.
* Use 0.3 grams of BP in the APOGEE charge well, pack it to the top with dog barf before taping it up.
* Use 0.5 grams of BP in the MAIN charge well, pack it to the top with dog barf before taping it up.

This seems to work every time.

To clarify: The rolls of Scotch tape that I have are 3/4" wide. Are you saying to tear off a 3/8" wide piece? Or find 3/8" wide tape (I don't think I've seen it...) and use some length of that?

Thanks,

Hans.

 

[WizardOfBoz]

A bit of extra space might be handy. The EZDD would probably require an ounce of the BP I have, if that much existed.

An OUNCE!!??? As in 28.35 grams? About 9 times the amount in a consumer-grade M-80 (a real one, not a fake)? I don't how this is possible without classifying your rocket as an RPG.

To clarify: The rolls of Scotch tape that I have are 3/4" wide. Are you saying to tear off a 3/8" wide piece? Or find 3/8" wide tape (I don't think I've seen it...) and use some length of that?

Thanks,

Hans.

I was thinking the same thing. The past weekend I had to swap out two retractable banners. They were attached to a roller using a piece of cloth and packing tape. The packing tape kept splitting up the middle as I was trying to remove it. But there's no way to rip it across the tape. Point is, plastics like scotch tape get stretched and that stretch makes it stronger to pulling on the axis. But splitting it is easy.

I was wondering if one might just tape around the whole nose cone circumference, and then using an X-Acto knife blade or spade blade to perforate the thing.

 

[RokitFlyr]

This cracks me up.!! People flying dual deployment rockets, and can't figure out a 3/8" piece of scotch tape!!

 

[WizardOfBoz]

@RokitFlyr I don't think its that simple. Take a piece of packing tape. Try to stretch it to failure by hand. I can't, and I'm a pretty big guy. But I can take a piece of tape and use it to fasten two pieces of plastic or metal. And I can pull the tape apart along its axis (splitting it). The way the tape is made, it is stretched along the axis. This aligns the polymer molecules and makes it incredibly strong in that axis. (You can see this by viewing light through the tape and polarized sunglasses, varying the angle between tape and glasses). My guess is that the difference in strength is about 5 or more to 1. So how you apply the tape makes a pretty big difference.

Failure mode may change, too. If the tape is aligned with the rocket axis, it may not break but could shear off.

All speculative, and Cris gets to tell me that I'm overthinking this if he wants. But to be safe I would install tape with the orientation perpendicular to the rocket.

 

[Titan II]

@RokitFlyr I don't think its that simple.

Yes it is.

 

[RokitFlyr]

Yes it is.

And then we'll see a discussion on weight and adding it to the Sims!! ! Maybe a tape thread? And it is that simple. It says Scotch tape, not packing, or anything else.

 

[WizardOfBoz]

Yes it is.

Yes it is.

Not helpful. You haven't explained how either 1) tape strength doesn't vary with orientation, or 2) why orientations with a difference in strength of perhaps 3 to 1 or more don't make a difference. Perhaps they don't, but a smug "I'm right, your wrong, and I'm not telling you why" is not quite what I (and I think 4regt) are curious about.

Almost all un-reinforced tapes that end up on a roll are anisotropic. Direction matters for strength.

 

[4regt4]

Not helpful. You haven't explained how either 1) tape strength doesn't vary with orientation, or 2) why orientations with a difference in strength of perhaps 3 to 1 or more don't make a difference. Perhaps they don't, but a smug "I'm right, your wrong, and I'm not telling you why" is not quite what I (and I think 4regt) are curious about.

Almost all un-reinforced tapes that end up on a roll are anisotropic. Direction matters for strength.

Also, there are several different tapes that are all labeled "Scotch" tape. I mostly have the frosty type, which tears easily in any direction. But I also have glossy Scotch tape that is similar in strength to packing tape. And don't forget about the original Scotch tape, which is still being sold. It's the type that after a few years turns yellow and curls up. Plus I just noticed on my workbench "extra strength" Scotch tape. All of these are labeled Scotch tape and come with the trade mark plaid label, albeit in different colors.

Hans.