Smug? Not helpfull? How is your disertation on packing tape helpfull useing Scotch tape as specified in the directions from the manufacturer? Get over yourself.
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WizardOfBoz
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@RokitFlyr, The point of my dissertation (two s's btw) is that tape strength varies with orientation. All that is being asked is whether one aligns the tape radially (as in wrapping around the fuselage) which would be weaker and would break easier, or aligned along the axis of the rocket, which would make it stronger. And Hans is asking which strength tape is the one to use: there are many different brands and strengths. Presumably, tape strength does matter because Cris is specifying scotch tape and not masking tape.
If Cris or someone else weighs in and says he's tried it both ways and it works both ways, and that brand doesn't seem to matter, fine. I'm ok with that. But Han's question seems valid to me and no one's answered it.
Given the rate of failure of DD rockets that I've seen in my short readoption of the hobby a response of "I doesn't matter" with no explanation is not helpful and not credible.
If Cris or someone else weighs in and says he's tried it both ways and it works both ways, and that brand doesn't seem to matter, fine. I'm ok with that. But Han's question seems valid to me and no one's answered it.
Given the rate of failure of DD rockets that I've seen in my short readoption of the hobby a response of "I doesn't matter" with no explanation is not helpful and not credible.
lr64
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If you saw my black powder burn, you wouldn't be so incredulous. I have yet to master the art. Anyway, don't they make firecrackers with flash powder?
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It's true that there are about a gazillion kinds of Scotch brand tape. I think that, when people say Scotch tape, they usually mean the "Magic" type with a dull finish that you can find in most stores. That still leaves the orientation problem. You could compromise with a non-binary 45°. ;-)
I think you may have misread part of what I said. All the variants I mentioned are ALL Scotch brand tape. Glossy, satin, "magic disappearing", extra strength, etc. The labels are essentially the same except for the color of the plaid and the fine print under the word "Scotch". And their physical properties are different. The failure mode of extra strength seems to be the glue, not the tape itself, for example. Last time I looked in an office supply catalog (it's been quite a few years), the only one that said "Scotch" w/o any modifiers was the original crappy stuff that yellows and leaves a sticky residue.
Hans.
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Correct. Real, consumer grade M-80s were made with flash powder.
lr64
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I just checked and the usual sort of Scotch tape is indeed labelled "Magic", even though I have not yet persuaded it to violate physical law. There are other kinds of Scotch tape that are probably stronger than an EZDD body tube, leaving your nose cone with three little cardboard appendages.
This cracks me up.!! People flying dual deployment rockets, and can't figure out a 3/8" piece of scotch tape!!
I think using masking tape on the nose shoulder for a tight fit would be better in a light weight 3" rocket.
But what do I know, I'm old school and use masking tape thrust rings a lot.
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Yes, it's in the Flight Manual, just cut a few strips 3/8" wide. Standard rolls are 3/4" wide... I haven't seen a 3/8" wide roll, so I'm not about to have you all go looking for a unicorn.
You want to use Scotch tape instead of masking tape because it shears easier, and doesn't leave a nasty residue. It's probably less likely to take off your paint, too. I use the clear stuff that comes in two-packs for $1.25 from Dollar Tree.
Well, it's official. A tape thread.
Just what kinds of rockets and how many are you seeing fail at the launches you go to? It's pretty rare. Last one I saw that failed was the main melted from too much BP in a very skinny Hybrid powered rocket.
It was recovered with no visible damage in a rough hard dry ground corn stalk field. Being skinny, long and separated; it basically flat spin/hovered down. Remember the drought we had.
What tape do you use on YOUR rockets? Never said I was right , or anyone was wrong.
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This kit is a nice intro to DD, but a poor choice for L1, imo. The components are from the BMS School Rocket, which is lightweight MPR construction. If there is risk to tearing the body tube, shattering the nose cone, and resorting to Scotch tape, are you really learning typical HPR techniques?
I see this rocket as a one-time L1 certification with an H135 or such, and then relegated back to the MPR fleet.
I see this rocket as a one-time L1 certification with an H135 or such, and then relegated back to the MPR fleet.
I'm not sure anyone suggested it as a cert rocket. It's just supposed to be a fun flyer. Some get competitive or are on a cert race. It doesn't have to be that way.
Send it up on F or small G motors and enjoy the experience!
Hans.
WizardOfBoz
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I launch at the Maryland Delaware Rocketry Association launches. I'm going by what I see and what more experienced guys tell me. And perhaps what the Youtube disasters show. Not all failures are due to BP issues but this past launch a guys DF main chute didn't deploy. I've seen a couple of launches IIRC where the drogue deployed (due to motor eject?) and the main didn't. (As an aside, two guys launched their L1 rocket, about an 11 inch tall by 1.6" diameter rocket sporting an I205, with predictable, self-disassembly results).
The point is, rockets fail. I'd like to understand stuff enough so that MY rockets dont fail. So if someone like Cris Erving says there's an important difference between masking tape as a breakable link and Scotch Magic tape, I want to know more to ensure that I don't end up posting a youtube video or posting a pic of my destroyed rocket.
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Ah, OK. I somehow mistook this for the official Eggtimer DD thread. Seems this one has kind of usurped the other one.
Hans.
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We aim this package at new flyers to DD who are coming over from MPR, not necessarily for L1 certs. We HAVE seen people cert with it... as recently as October Skies at TCC about a week ago. We have tested it with pretty much the biggest motors you can fit in it, an Aerotech I205 and a CTI I243, they both were fine (around 4,000' altitude). It's certainly capable of flying L1 motors.
If we made it out of FG it would have cost twice as much, at least. Price was important. Is it a "throw away" rocket? No more so than any other cardboard-wood kit IMHO.
I have done multiple ground tests and two successful flights now with my EZ-DD using two 18mm pieces of tape holding on the nose cone. Just had the cheap tape from dollar store(18mm) around the house, I used it the width it came and I didnt trim it or anything. This is a great technique for beginners to start learning dual deploy. Dont overthink it and do your ground tests before flight.
What it comes down to is that we don't know which type of tape is the best kind of tape for securing a NC. I don't have decades of experience, but I'm not familiar with another rocket that indicates using Scotch tape. It makes sense since the School Rocket tube is rather thin. Most DD rockets have thick HP tubes that make it easy to use shear pins. However, this is science so I'm giving the brass strips method a try. Not because it's better than Scotch tape, but because why not?
The Estes/BMS size of 3" OD cardboard tubing is 0.035" thick, indeed thinner than the 0.050" wall of LOC, etc., high power 3" ID / 3.1" OD tubing. It is however the same thickness as LOC 2.63" OD / 2.56" ID tubing, which no one seems to find inadequate for L1 high power.
Examining the corresponding LOC 2.56" nosecone vs. the BMS 3" cone - both of which I have in hand and have consulted in composing this post - the LOC cone is notably less stiff (though perhaps less brittle). (EDIT: in delving through my records, I find it may be an Aerotech cone I have instead of a LOC, but the point remains that this is a high power cone that's less stiff than the BMS cone.) I'm not sure how you'd blow up either - but especially the BMS cone, which I've used with shear pins before myself - without grossly overdoing charges.
Yes, the tape retention method is mildly unconventional (though hardly unknown), and if I were to build one of these, I'd probably switch quickly to shear plates, but I don't see a reason why this can't be flown as repeatedly as a LOC 2.56" kit.
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What he said
.
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You are correct. The LOC 2.56" body tube is pretty wimpy yet is common in HPR.
There are a couple posts upthread about blowing up the BMS nose cone while ground testing.
I am bashing 2 School Rockets into a 2-stage, so there is a lot of body tube to care for if I want to launch it repeatedly. I am taking steps to increase durability, like stiffening body tube edges, doubling/coating exposed couplers, and brass shear plates, but still trying to keep mass down. It's a fine line. I will likely need an H128 or H180 in the booster to get the necessary performance.
WizardOfBoz
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I can't be wrong because I've never used tape in this manner.
My questions are to figure out what to do with my EZ-DD.Hans (the OP) had questions about tape. His posts stand for themselves. What my question was was which orientation of tape is to be used, as tape is much stronger in one direction than another. The response "It doesn't matter" is fine, but I would have liked some data/theory/reasoning... So if one had added "Orientation doesn't matter - the charge is big enough to break the tape whatever orientation", possibly with an "Radial application leads to the tape breaking, and axial orientation leads to the tape coming off in shear". Or something describing whatever happens.
Cris pointed out that magic-type tape (the clear stuff) might be less likely to remove paint.
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I think you are probably overthinking it.I can't be wrong because I've never used tape in this manner.
Hans (the OP) had questions about tape. His posts stand for themselves. What my question was was which orientation of tape is to be used, as tape is much stronger in one direction than another. The response "It doesn't matter" is fine, but I would have liked some data/theory/reasoning... So if one had added "Orientation doesn't matter - the charge is big enough to break the tape whatever orientation", possibly with an "Radial application leads to the tape breaking, and axial orientation leads to the tape coming off in shear". Or something describing whatever happens.
Cris pointed out that magic-type tape (the clear stuff) might be less likely to remove paint.
But having used tape before, albeit at most twice, on bt60 tubes I had placed the tape with it oriented parallel to the seam. Not perpendicularly across the seam.
So in Cris example of 3/8", you'd have a tape length along the x axis (the seam) of 3/8", and a long the y axis (perpendicular to the seam) a length of 3/4".
Not sure if Cris' ez-dd document calls it out or not
WizardOfBoz
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Well, I'm an engineer, so yeah... Kinda goes without saying, right?
One thing that probably prompted my deep dive into this was indeed the fact that I spent an hour or so on Saturday detaching two banners from their cloth leader* and the fastening was clear packing tape. The difference between axial tensile strength (very hard to break) and splitting the tape (maddeningly easy to do) was what made the job so difficult. So there was a strong emotional response prompting me to ask "which orientation"? One way = Kevlar, the other = Manchego cheese.
Given that the radial tape worked for you is useful data, thanks. I worked out (using 15 psi) that the force per inch on the circumference for a BT-60 is about 6 lbf/in, whereas for a 3" body, its about 11lbf/in. Not a huge difference. The actual ejection charge force is like 30lb vs 110lbs. Supposedly the tensile strength of tape (in the strong direction) is about 13 lbf/inch width. So about 9.25lbf for 3/4 tape. This means that three pieces of tape applied axially might be close to limiting separation for the BT-60. For the 3" EZ-DD the charge (even if its only 10psi) would easily handle 3 pieces of tape axially. So we might suspect that your tangential orientation is better for smaller tubes. And you have data that it worked...
BTW, I got the banners remounted!
*The cloth leader attaches to a roller in the base, so that the banners are retractable:
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I'm still not sure how you blow up the BMS cone without mixing units or entirely misunderstanding how much powder is needed to separate.
Regarding the tubes, I agree they're not impervious to wear and damage. Stiffening the tube ends is definitely a good idea. Personally I fiberglass most cardboard intended for midpower and nearly all cardboard intended for high power (H13 and H14 will be the exceptions). Yet I've seen plenty of veteran LOC 2.56" kits as well as a few veteran BMS school rockets and don't doubt they'll hold up unglassed to moderate thrust L1 motors.
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I think people are sort of confusing the ideas of "appropriate for L1 attempt" with "appropriate for learning dual deploy". I've flown mine four times. None high power. Never had a totally successful flight. All my fault. There's a bit of a learning curve. I'm still on the leading edge of the slope. I'm betting I get the next one right. *Then* maybe I'll fly it on (lower end) high power motors.
Complicated epoxy and laminating.. no problem. Office supplies a 3yo knows how to use... cant figure it out at allThis cracks me up.
Exactly. This is a $100 test bed for DD. My next venture is a LOC-IV with Quantum altimeter on a DD sled.
The brass strips work great. The Scotch tape also works for sure, just wanted to try something new. I forgot to zoom so have to look closely to see the drogue deploy at apogee. The altimeter is an estimation (not as fancy as a Quantum or Ion) so probably ejected at 500ft instead of 700ft in the flight video.
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