Zephyr build by newbie BAR

[Dougla2]

Thanks to the people who posted their builds, I was able to get going finally. I may be able to contribute a couple ideas from my amateur-ish process.

This started when I found a box of Estes parts in the garage from 20 years ago.


While putting the old kits together, found a couple new ones and moved indoors.


Discovered TRF and decided to try out a couple more kits.


Saw a few PVC stands here, so pulled pieces out of the scrap pile.


Used it to hold a Cherokee E for decals.


Time to try out epoxy, so picked up a Super Big Bertha for practice.


With confidence now it was time to start the Zephyr. I found that the dry fit was too tight and had to sand off the 'scabs' that remained from laser cutting of the plywood. Removing all of the char allowed the parts to fit properly. Had to make some sanding tools to fit my paws.


The weight of the eye bolt seemed excessive, so I headed back to the scrap heap for a piece of aluminum wire that was left from a satellite dish installation.


Left the washer on the bottom and curled the ends to dig in around it.


Applied epoxy on the bottom.

 

[Dougla2]

Epoxy on the top.


Used a needle and thread to stitch up the shock cord.


Wrapped the nylon cord with some duct tape.


Picked up a cutting mat along the way.


Masked off the fins for epoxy.


I found that the retainer required considerable sanding of the motor mount tube in order to fit. The build process has been a lot of fun so far and made much easier because of what I've seen on this forum. The videos by Tim at Apogee were helpful and enormously entertaining, especially seeing his mistakes and how he recovered from them. "oops" Hahahaha. Hoping to make more progress in a few days and look forward to flying these when the weather warms up!

 

[AfterBurners]

Nice stitch work on the shock cord. You may want to ditch the zip ties on your rocket holder. There's a good chance they will mar the finish on freshly painted rockets although they may be completely dry. Just glue the pads in place.

 

[Vdutel]

Doug:

That is one sweet build share!! Glad you put this together.. Can’t wait to see it once you get it painted and flown. Please post those pics when it’s done... Eager to see it!!

again Thanks for this

victor

 

[MichaelRapp]

So awesome....when I get more experience, the Zephyr is probably going to be my first large rocket due to Tim's videos.....I wouldn't be in this hobby without his videos.

 

[crossfire]

I found with LOC kits if some of the char from lazer cutting was sanded off the parts fit much better. A Dremal tool does it in seconds

 

[Dougla2]

Nice stitch work on the shock cord. You may want to ditch the zip ties on your rocket holder. There's a good chance they will mar the finish on freshly painted rockets although they may be completely dry. Just glue the pads in place.

Thanks for the tip, that's what I did by wrapping a few Velcro wraps around the PVC.

 

[Dougla2]

I found with LOC kits if some of the char from lazer cutting was sanded off the parts fit much better. A Dremal tool does it in seconds

Good idea, did you use a sanding disk to get into the gaps? I have to work around some dexterity issues and am known to be a clumsy oaf with power tools, so hand sanding is not only better for my parts it also serves as PT. Besides, I made a few hand sanders and felt compelled to use them. Still, your suggestion is good, thanks.

 

[crossfire]

Good idea, did you use a sanding disk to get into the gaps? I have to work around some dexterity issues and am known to be a clumsy oaf with power tools, so hand sanding is not only better for my parts it also serves as PT. Besides, I made a few hand sanders and felt compelled to use them. Still, your suggestion is good, thanks.

I used a disk for gaps and the barrel drum for the CRs. It just a very small amount needed to be taken off. Its once a little of the burn color is removed stuff fits perfect.

 

[AfterBurners]

I used a disk for gaps and the barrel drum for the CRs. It just a very small amount needed to be taken off. Its once a little of the burn color is removed stuff fits perfect.

I find its always best to sand to fit then have it too loose

 

[Nytrunner]

The weight of the eye bolt seemed excessive, so I headed back to the scrap heap for a piece of aluminum wire that was left from a satellite dish installation.

How strong is that wire? A late ejection, blowby, or horizontal flight can put serious forces on the recovery system. (high-power folks often use a 50G yank as a design point)

 

[Dougla2]

How strong is that wire? A late ejection, blowby, or horizontal flight can put serious forces on the recovery system. (high-power folks often use a 50G yank as a design point)

Good point, the wire used had no kinks or obvious weak spots, so I am guessing it could withstand a lot more force than the ejection charge and parachute braking could deliver. While staring at it and imagining what breaks first, the wood centering ring splintered and broke. So, in my imaginationland scenario, it was fine. OK, not exactly a fully tested engineering solution, guess we shall see at the range. The bottom side did get a substantial extra slather of epoxy during the MM installation and the hooked ends should prevent slipping out. If this proves out to be a good component, the weight savings is nice. I would think aluminum hardware, like threaded rod and eye bolts would be standard. Perhaps a better cord mount would be a ring of Al that loops thru the wood with a thin metal plate. Maybe a thin stainless wire attachment point..., this was just application of the "use what you got" style of construction, after seeing the heavy eye bolt.

 

[Nytrunner]

I was reasing just recently of someone that used aluminum threaded rods with no issues, but returned to using smaller steel rods because the aluminum ones were more expensive.

 

[WhiskyTangoFoxtrot]

Dougla2 said: ↑
The weight of the eye bolt seemed excessive, so I headed back to the scrap heap for a piece of aluminum wire that was left from a satellite dish installation.

Tim Van Milligan knows what he's doing. Do you?

 

[wsume99]

I have used an aluminum rod bent into the shape of a U and epoxied on the backside of a bulkhead for recovery before. Rather than just follow the herd and use massive SS hardware on a lighter cardboard rocket I prefer to use my brain.

The recovery weight is probably in the 2 lb range. So at 50Gs we're talking 100# of force on the attachment point. A 1/8" diameter aluminum rod with 10ksi yield strength (which is relatively weak as Al goes) could withstand approx 120# before yielding. So the material is strong enough assuming it's larger than 1/8" diameter. The weak point will be the epoxy attachment, IMO. Regardless, if you have a 50G recovery on a cardboard rocket you are going to have lots of other things to worry about.

 

[Dougla2]

Dougla2 said: ↑
The weight of the eye bolt seemed excessive, so I headed back to the scrap heap for a piece of aluminum wire that was left from a satellite dish installation.

Tim Van Milligan knows what he's doing. Do you?

I know just enough to be dangerous. Danger isn't my middle name but it does appear in my warning label.

My thinking is that the off-center weight of the original piece could cause issues that removal would help. Of course removing weight in the aft section should help stability, so what is missing with my solution is stress testing the Al wire. After use the wire may become deformed and even kinked, which would compromise it, so I may try out some testing to see what it takes to break, using more wire from the same scrap piece. I'll post up pictures of the test. Having a Zephyr drop from 1,000ft would be a poor outcome for sure, so I can see why testing is a good idea. What pull strength would be considered adequate?

 

[crossfire]

Dougla2 said: ↑
The weight of the eye bolt seemed excessive, so I headed back to the scrap heap for a piece of aluminum wire that was left from a satellite dish installation.

Tim Van Milligan knows what he's doing. Do you?

Can't be much difference in weight to really matter.

 

[Jozef]

If not too late I suggest taking out the aluminum ring and putting in the eye bolt that came with the kit. That washer isn't doing a thing. The rocket will never see that minor weight difference. A stock built Zephyr flew perfectly at Midwest Power in November.

 

[richP]

If not too late I suggest taking out the aluminum ring and putting in the eye bolt that came with the kit. That washer isn't doing a thing. The rocket will never see that minor weight difference. A stock built Zephyr flew perfectly at Midwest Power in November.

Agree 100%. 2 reasons.
The epoxy will crack due to side-to-side movement during recovery.
An eyebolt with a quick-disconnect will allow you remove the shock cord for cleaning/inspection/replacement.

Weight difference for such a small piece is relatively insignificant.

 

[Buckeye]

Tim Van Milligan knows what he's doing. Do you?

Tim Van Milligan also needs to make a profit, so he uses components that are cheap, readily available, and don't need R&D. That's why he throws 1/4-20 hardware in the kit. Easy, but probably not optimized for performance.

This forum is rife with overbuilt kits using hulking eyebolts, threaded rod, carabiners, etc. Don't follow the herd. Your aluminum loop is probably just fine for MPR.

 

[Dougla2]

Finally got some time to test out the Al wire anchor point, so here is the test that I performed and the results.


The suspended weight of the rocket will be 1152g. The total weight of the rocket, motor, adapter, parachute and cord is 1562g.



The NAR Member Guidebook calls out that "Recovery systems must be able to handle forces 40-60 times the rocket’s total weight." so, for this rocket 1562g X 40 = 62,480g and 1562g X 60 = 93,720g or 138-207lbs. So my test was to apply 207lbs to the Al wire anchor. I repeated the following test 10 times.


Following the general advice to "use what you have", I rigged up a piece of the same wire that is in the rocket with the same epoxy but eliminated the steel washer and used a thicker material, some scrap particle board. I clamped it to a bench, tied a piece of rope to the wire, attached a steel bar to use as a handle and stood on a scale to watch the weight of the force applied. In order to apply the 207lbs I had to put on a backpack with a dumbell and lean onto the bar to suspend myself by the anchor. It was awkward but kind of fun.



The epoxy held, although the deformation of the wire caused some to peel away from the loop side and did not compromise the strength of the bond. the deformation of the wire was pretty extreme, bending it straight down. After repeating the 207lb force application 10 times, I moved the test piece to a higher spot and hung under it, while wearing the added weight of the backpack and a hardhat, then bounced a few times in an attempt to break the wire. I would estimate that around 300lbs were applied without a failure but that is just a guess made by a very chilled (cold garage) tester.



This effort could not get the wire to fail, so I do not yet have a failure load number. My conclusion is that the substitution of the anchor point, which saves 22g of off-axis mass, is safe enough to meet the NAR guidelines but may become unsafe if the Al wire is manipulated in such a way that it gets repeatedly bent, which could cause weakening. I'll use care by inspecting it before flights and taking care to keep it unmolested. I considered heating it with a heat gun but kind of lost interest in further testing after finding that it was not possible to break by bouncing my not unsubstantial mass. If I get around to finishing the test by figuring out a way to measure the force required to break a loop of this Al wire, I'll post it here. In the meantime, it's back to sanding, painting and prep for warmer weather and my first launch.

 

[Nytrunner]

Well, that settles my concern! Great test campaign.

The aluminum bent as expected, but did not fail, and you implemented it in such a way that the initial yield doesn't compromise the system (like an eye bolt opening up)

 

[Dougla2]

Eventually I will find out what it takes to break this wire loop but want to measure the force instead of hooking it a bumper and trying to drag a tree. Next time I'll just buy an Al eye bolt but will load test it before installing. My guess is that the 1/4" plywood centering ring would fail before the wire loop but don't expect the force to ever reach that point. Fun exercise that helps to reinforce the safety guidelines established by the NAR, so in summary a worthwhile effort.

 

[Buckeye]

Excellent experiments!

 

[Dougla2]

Thank you, an important part of the scientific method is peer review, so by posting the test here I hope to have checked that box. I was surprised by the weight of the retainer and the adapter that I'll use, especially since they are at the aft end. Maybe that CG move will be offset by the chute release and it's protector. I find it amazing how fast many people build and fly their rockets, my process is waaaay slower as the process is so enjoyable and entertaining that I like to stretch it out. I'll need to join NAR and a local club or 2 prior to launch and very much look forward to that first beautiful day out on the prairie. It is too cold to spray paint so today's plan has shifted to goofing around instead of being productive, maybe I can figure out which kit comes next, thinking another Apogee like the Katana or the LOC EZI-65.

 

[Nytrunner]

Give the LOC a try! Or branch out materials like BlueTube from Always Ready Rocketry, or Quantum Tube from PML. If you want a taste of composites try canvas phenolic from MAC performance

 

[Dougla2]

Something that needs a lot less sanding would be great. Going to try to find another 4" BT and a 54mm motor mount, thinking that dual deployment section can be shared betwixt. Looking into tracking device as well. Once it warms up I can get back in the garage and use power tools but building indoors has limitations on dust generation. Currently debating whether or not to get a pop up tent for shade on launch day as there probably isn't much shade and the sunshine in CO is brutal. In other words I am staggering around ideas, looking for the best path ahead.

 

[Dougla2]

Finished paint, applied stickers and now will slide on the Nomex cloth and sew the cord to nosecone. I'll pick up a swivel and clip to attach the parachute because the swivels in my saltwater tackle box are of unknown strength. I installed a nice wrinkle in a sticker and find that it lends a more customized appearance, so will leave it. First couple flights will be around 1,100ft, so not going to use a chute release but with the larger motors planning to install the JL product.

Looking at the EZI-65 for next kit but may wait to purchase until after launching the Zephyr. Still trying to figure out which camera to get, where to find and how to attach it. Hey, this is fun.

 

[ThreeJsDad]

That came out nice, Can it really fly on a Mid Power Motor?

 

[Dougla2]

G78 is what I am planning to use for the first 2 flights. Shakedown will involve not just the rocket but also everything else surrounding the launch. Just checked Apogee's website and see that it should go 839FT. https://www.apogeerockets.com/Rocket-Kits/Skill-Level-3-Model-Rocket-Kits/Zephyr?cPath=1_86&

Not sure if this is "mid-power", that is just a guess as this is my first large rocket and my plan is to see how it goes prior to L1 certification flight attempt with a 38mm motor. Hoping to build a 54mm rocket if all goes as planned.