V2 for my L3

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Cl(VII)

Chris Bender, Lab Rat
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Well the title pretty much says it. I did not start this project with designs on getting my L3. Instead it started with my desire to make a V2 with some presence, i.e. big. Well, the V2 is pretty stumpy, so to get one even close to the 6' range requires a 7.5" diameter, which requires some weight (15-20 lbs). Which is getting it into the ideal range of my "been drooling since I heard it existed motor, the M650W...10 seconds of White fire and smoke, yes please! So this project became an exercise in designing and building a V2 for that motor, and one that is light enough to also fly on full-J/baby-K range as well, because M motor flights will not be regular occurrences for me. Like I said, the central goal of this project isn't "get my L3" it is Build a V2 to fly the M650W in, the L3 is just a co-requisite.

I have recently gotten the go ahead to start building from my L3CC member, so I'm doing this thread as much to make sure I document the build properly as anything else. I'm going to be trying some new, to me anyway, techniques along the way; vacuum bagging, composite fins (plywood, end grain balsa, carbon fiber), adjustable nose weight, etc.

Anyhow, at the start of my build threads I also try to note a few things up front.

- Do NOT assume that I know what I'm doing. I.e., if you are new here, don't just think my way is THE way. There are many paths to rocketry Zen (I think I stole that from samb). Most of my build techniques I stole from qquake2k, sodmeister, legrandudu, dixonj93060, etc. anyway. In other words, this is all their fault!

- I suck at photography

- I can't spell, and I would have learned by now if it was going to happen.

- I build at a glacial pace, as such I am targeting July-Nov of next year for the flight.

- I know there are commercially available kits that fit the bill, but I like to scratch build.

- I am overly detailed in descriptions, I learned from threads like this, and I'm not charging by the word.

- I am fundamentally opposed to the keeping it low, slow, and simple for a certification. If that is your deal, great, but low, slow and simple just isn't what I enjoy flying most of the time. Certify what you like to fly, if you fail, try again. As long as you do it safely, that is all that maters.
 
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Straight from my L3 submission:

This level 3 certification project consists of a scratch built sport scale V2. The airframe will be made of 7.5” phenol tubing wrapped with at least one layer of fiberglass. The electronics will be housed in an 8” long donut electronics bay with a 4.0” opening. The use of a donut electronics bay will allow for the use of 75 mm motors fitting cases up to the AT 75/6400. This configuration allows for separation at the airframe-tail cone joint at apogee (for drogue deployment) and separation of the nose cone for main deployment (at or around 900’). The nose cone will be a standard LOC 3:1 plastic nose cone with an internal 3.9” ID phenolic coupler to function as the main chute bay. The fore end of the tube will be topped by a ½” plywood ring with a 2.25” center hole to provide access to the fore end of the NC. A bulkplate will attach to this ring, and act as the shock cord attachment point and base of the adjustable nose weight. Lead weights will be cast that allow for up to 9 lbs of weight to be added to this space. Additionally, the space between the internal tube and the NC will be used as a tracker bay, and will be accessible through a 1.25” hole in the aft CR for the NC tube. The tail cone will be constructed from a 5:1 plastic nose cone. The motor mount will be 75 mm phenolic tubing and motor retention will be with an Aeropack flanged retainer. The fins will be constructed with weight savings and strength in mind, using 3/8” high quality plywood edges with end grain balsa center. These will be laminated with at least one layer of carbon fiber. The fins will have 12.5” fin tabs. The overall rocket length will be 64.1” with a dry weight (without electronics, recovery gear, or motor) that is estimated to be around 205 oz.



Note: The fin tabs look wonky, but that is more an artifact of OR and my laziness. They will end at the CR that currently cuts into them.
 
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The project began at "The Bob Stash". This is a large collection of parts, kits, and rockets left to DARS by a deceased member, Bob. The stash is a much beloved source of far below retail parts for a donation to the club. Also, I think Jack wants his shed back, which probably helps with the deals. Fortunately the stash yielded me my high dollar components, 7.5" phenolic tube, 75mm phenolic tube, a 3:1 NC and a 5:1 NC. A 4:1 would have been more accurate for a V2 boat tail, but I can happily live with the discrepancy for the savings...sport scale, not scale.



Interestingly, the 5:1 NC had a line marked around it, which I realized days later turned out to be exactly where the cut should be for the boat tail. The short piece of 7.5" phenolic that I originally took in case I needed to make a coupler, turned out to be 17.75"...exactly what it should have been. Apparently, I bought Bob's V2 project. Our V2 will fly Bob!
 
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Hey, what a great project as it is both your L3 achievement and "a tribute to Bob."
 
As I mentioned, Bob did me a solid and cut the tube for me, so no need to do that. I am going to glass the thing though. I'm not a glass everything guy normally, but this thing is going to be taking a good bit of force, so the additional weight is well worth it.

I used Soller Composites Fiberglass Sleeve, Soller Composites Heat shrink tubing, and US Composites 635 Laminating Resin and Medium Hardener. This sleeve is awesome stuff, any moron can fiberglass well with this stuff, which is why I use it. It is admittedly more pricy than cloth, but there is almost no learning curve.

Soller composites link: https://www.sollercomposites.com/composites/carbon%20fiber%20sleeves.html#carbonfiberglass

I used a single layer of the 7" light, natural sleeve...this is roughly equivalent to 9.5 oz cloth.

To use the stuff you simply slide it over your tube, and secure it somehow (I like zipties around the pvc pipe I have everything on. There are 2 CRs recessed inside the tube about 4" from each side. Sleeve this size would probably not need secured like this, so all that excess could be avoided. I have used small diameters on 38 and 54 mm projects, and those are really helped by securing with zipties.

One note on fiber glassing if you haven't done much before. PREP EVERYTHING IN ADVANCE and lay out your work area neatly.



Saturate out the cloth, a small roller helped immensely for this part. This tube took a full double batch (8 pumps total). Slide the heat shrink over (cut extra, it shrinks longitudinally also), then work the tubing making sure not to hotspot the tubing it can melt/tear. the tubing will eventually pull down very smoothly, and working from the inside out will push most of the excess epoxy out the end. For something this size you may get a pool inside, you can prick it with a pin to drain the pool with little damage to the end product finish. If you do melt a hole you can just slide an extra piece of tubing over and shrink it as a patch.



Once the heat shrink is cutoff I came over the top with a light coat of epoxy and let that cure. This is just to fill any pinholes. After that had cured for two days it was sanding time...what doesn't involve sanding with these builds? In the end I have a strengthened tube, and bonus from the heat shrink the sleeve wraps over the face of the bt giving a smooth surface that should provide extra zipper resistance.

Rough sanded and ready for building, priming:



Starting weight: 502 g
Ending weight: 767 g
 
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I'm here at one of my thrice weekly sitting in the lobby of the natatorium for an hour and a half sessions, so may as well update the build.

I prefer to cut my own CRs and bulkheads, and with my largest previous project being 4" diameter this was accomplished with a Harbor Freight fly cutter and Drill Press...you too can build cool rockets with crappy tools, and it leaves more motor money which I am going to need. These rings are mostly beyond the limits of these tools, so I needed new tools, or a workaround. I searched the here and the rest of the interwebs and came accross a couple good adjustable jigs for circle cutting with a bandsaw (got one) and sanding circles on a disk sander (got one). I also have a copious wood scraps bin(s), so the total investment in the below jigs was about $1 in screws, and a few hours time. All of the CRs and bulkheads for this project will be made or modified using these two jigs.

Band saw Cutter:



Sanding Jig:



The bulkheads are cut a touch big on the band saw jig, and then sanded to a tight fit on the sanding jig. For CRs the center hole is then cut with the fly cutter using the central pivot hole needed for the jigs to guide the bit (they are the same size, not by accident). The Sanding jig also allows for nice control over angled edges for the NC and boat tail CRs.

Crappy drill press and fly cutter...gets the job done, eventually.



I did grab a few commercial CR's from the stash, but there are no standard size rings in this project, so they will need to be sanded to fit. To do this I made a plug bulkhead out of some scrap to guide the shaping.

 
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First up, gotta cut the base off. Marked the line, made a notch with a dremel and cut it with a Zona saw.



There are two very different CRs for this section, both were made from high quality 3/8" Baltic birch ply.

The fore ring is to hold the inner tube, and to act as a mount for the bulkhead and adjustable nose weight. It has a groove cut into it (made with fly cutter and about 1/8" deep) to set the tube in, the edges are angled to match the contour of the NC and there are 6 holes which match up to the bulkhead.

The aft ring is more straight forward, but also contains a 1.25" hole to afford access to a tracker bay.

Both rings had 8-32 T-nuts epoxied (5 min) in place for Tracker plate and bulkhead retention down the line.



The tube was epoxied into the CR groove using Aeropoxy structural (this will be the main structural epoxy for the entire build).



This was test fit into the nose, and a flashlight dropped into the tip. This allowed for a dashed line (hard to see) to be drawn around the NC showing the CR location. The fore ends of the T-nuts were taped over to prevent epoxy sneaking in and the tube epoxied into the roughed up NC usingf Aeropoxy with milled fiberglass added to thicken it. The Aft CR was put in place to ensure center, and 3/8" brad nails (x12) were were put through the NC into the fore CR.



After the Aeropoxy had began to set I poured in a 12 g batch of US Composites 635 (Medium) laminating resin to create a "fillet" between the NC, ring and tube.



This brings us to the end of swim practice, and as such, the end of this evenings updates.
 
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Nice ! I hadn't seen heat shrink tubing before. A double popcorn build thread ! :pop::pop:
 
Nice work Chris! I hope to see this bad boy on a column of fire and smoke!
 
A super start to what is bound to be a great project!

Watching closely and want to be at the L3 attempt to see it go.

Reading this thread made this morning's waiting at the airport measurably more pleasant...;)
 
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Thanks for the good words folks. Glad to have some people along for the ride.
 
I'm here at one of my thrice weekly sitting in the lobby of the natatorium for an hour and a half sessions, so may as well update the build.

I prefer to cut my own CRs and bulkheads, and with my largest previous project being 4" diameter this was accomplished with a Harbor Freight fly cutter and Drill Press...you too can build cool rockets with crappy tools, and it leaves more motor money which I am going to need. These rings are mostly beyond the limits of these tools, so I needed new tools, or a workaround. I searched the here and the rest of the interwebs and came accross a couple good adjustable jigs for circle cutting with a bandsaw (got one) and sanding circles on a disk sander (got one). I also have a copious wood scraps bin(s), so the total investment in the below jigs was about $1 in screws, and a few hours time. All of the CRs and bulkheads for this project will be made or modified using these two jigs.

Band saw Cutter:
View attachment 274037 View attachment 274038 View attachment 274039 View attachment 274040 View attachment 274041

Sanding Jig:
View attachment 274043 View attachment 274046

The bulkheads are cut a touch big on the band saw jig, and then sanded to a tight fit on the sanding jig. For CRs the center hole is then cut with the fly cutter using the central pivot hole needed for the jigs to guide the bit (they are the same size, not by accident). The Sanding jig also allows for nice control over angled edges for the NC and boat tail CRs.

Crappy drill press and fly cutter...gets the job done, eventually.

View attachment 274044 View attachment 274045

I did grab a few commercial CR's from the stash, but there are no standard size rings in this project, so they will need to be sanded to fit. To do this I made a plug bulkhead out of some scrap to guide the shaping.

View attachment 274047

Nice jigs:)
 
Nice jigs:)

I would think you'd like them. The Band saw one is basically a hybrid of your scroll saw jig and the below chap's band saw jig. While the sanding jig is essentially my kludged ripoff of your jig.

[video=youtube;afGNbVrBiFE]https://www.youtube.com/watch?v=afGNbVrBiFE[/video]

These thing really do work great, and are remarkably easy to construct.
 
So I find myself with another hour of sniffing chlorine and sitting.

So the entire point of making that internal tube in the NC was to allow for a tracking bay between the tube and NC wall. If you look back at the NC rings you see that the large ring for the base has a 1.25" whole in it to allow for access. To make the plate that will go over this an additional CR was cut out of 1/4" Birch ply and sliced into multiple covers. One of these was mocked up with the tube, taped in place, the retention holes drilled through both ring and plate, and the access hole marked.

A sled was made from a scrap of 1/8" Birch Aircraft Ply. The sled will be held to the plate by two pieces of aluminum angle, that were cut and mounted to the sled. The bracket then got a trip to the bench grinder to make it fit the access hole. Once attached to the sled the unit was dry fit, and the brackets bent so that the sled angles roughly parallel to the NC, so there is no pressure on the antenna.



The entire thing has been mocked up in the NC, but that is hardly photogenic. The moral: it fits.

The astute observer will notice these are not the correct rings pictured earlier. These were made from scrap bin plywood to test this idea out before I started cutting the good stuff.
 
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Looking nice! One thing I learned when building my own 7.5" V2, use the Rocksim method of CP, apparently it's more accurate in models like the V2 with large curvy sections that adds more fin area down the boat tail. I initially added noseweight to match barrowman and ended up not needing it which really restricted performance...
 
Looking nice! One thing I learned when building my own 7.5" V2, use the Rocksim method of CP, apparently it's more accurate in models like the V2 with large curvy sections that adds more fin area down the boat tail. I initially added noseweight to match barrowman and ended up not needing it which really restricted performance...

Definately. If you look at the build diagram pic I posted it shows both values. I did that for completeness only, I will definately be baseing my CG on the Rocksim calculation. Also, the Rocsim calculation of CP better agrees with the suggested CG for several V2 kits, so it has been real world tested also.

I think to achieve the 1 cal over the Barrowman CP in the nose weight space available I would need dark matter or stellar core material, and I can't find a commercial supplier of either.

Nose weight limiting the available motors is really what led to the adjustable nose weight option, and trying to push all the "stuff" as far forward as possible. After finishing out the NC at just a touch over 3 lbs (pictures next swim practice) and having all the bt parts weigh in under 4, I'm getting hopeful I can get this thing in around 15 sans motor and nose weight. That would provide a really wide spectrum of motors, so I'm focusing very closely on managing weight...the rocket, not mine.
 
A question:

I'm planning to cert with the M650. That one burns for about 10 seconds (read, lots of sustained heat), and as designed the case will extend well beyond the MM into the drogue bay. Also, this rocket will break at the boat tail for the drogue which will leave the forward foot or so of the motor case in space with the shock cord rubbing it, and ultimately lying on the ground. So, to protect the case from cosmetic damage, and to provide some insulation for my drogue recovery equipment I think I've talked myself into extending the MM past the fore most CR and almost completely to the bulkhead. The only downside I see to this is a little bit of weight, but that weight will be almost equally distributed around the desired CG, so it really is only a direct weight penalty with no nose weight implication. Do any of you see ay negative implications that I am missing?
 
The smell of chlorine means it;s time to update the thread. I've made a lot of progress a half-hour here and an hour there.

After roughing up the inside of the NC with some 80 grit, the aft CR was glued into place using Aeropoxy thickened with milled fiberglass to keep it where I wanted it. Another dozen brad nails ensure another level of mechanical bonding with the NC. The Aft CR was positioned to allow about 3/16" of the inner tube to project past. This lets the tracking bay plate be fully recessed when screwed in. Lastly, external (if that makes sense) fillets were applied.

A piece of 1/4-20 all thread was cut so that it extends almost to the NC tip when passed through the forward bulkhead. This will be the rod that holds the adjustable nose weight, and is held on the fore side of the bulkhead by a washer and wing nut (the weight will go between the bulkhead and the washer). On the aft side of the bulkhead the rod will be held with a stainless steel oblong lifting nut, which will serve as the shock cord anchor point.



Ok, so using Flikr works, but that is an asinine level of steps needed to post a picture.
 
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An afternoon distraction post.

The main bulkhead for the electronics bay is going to include a lot of stuff. This bulkhead will be the attachment point for the drogue and main shock cords, as well as all the terminal blocks and charge wells, the altimeters, and of course the rods that tie the bay together. In other words, it's going to be really, really, really important to get that thing just right as almost every failure mode in the rocket is centered there.

The bulkhead was made from 3/8" Baltic Birch goodness. Some radial reference lines were drawn down on the bulkhead (fore side) 22.5 degrees apart, and myriad holes laid out and marked for size.



Like I said, a lot going on here

There is a second bulkhead that matches the ID of the donut bay tube. This bulkhead was glued in place with some Titebond II, and a hardwood dowel also glued in at the same time for alignment. Once dried the dowel was sanded flush on both sides. The purpose of the small bulkhead is to help with alignment, and sealing from the drogue compartment.



Lastly the holes all needed drilled, and some of these needed to line up with the donut bay aft CR, AND some of these pass all the way through the CR while others do not (more later on that). Back to my favorite building tools for this, tape and a cheapo Harbor Freight Drill Press. All done and pretty happy with the results.



The holes that are shown in the tape picture do not extend into the CR, in other words, they were drilled prior to taping the two together.
 
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Since I'm getting increasingly concerned about the reliability/stability of this place I am in the process of copying this build thread from here to Rocketrycenter.com where I post under the same screen name. I plan to continue the thread in duplicate on both sites. I'm just covering my bets, since this place collapsing (though unlikely) would mean I have to document everything again for my L3, and I don't want to forget something. Ironically, to make this easier to maintain in two places I will be converting all the photos over to Flikr links.
 
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Since I'm getting increasingly concerned about the reliability/stability of this place I am in the process of copying this build thread from here to Rocketrycenter.com where I post under the same screen name. I plan to continue the thread in duplicate on both sites. I'm just covering my bets, since this place collapsing (though unlikely) would mean I have to document everything again for my L3, and I don't want to forget something. Ironically, to make this easier to maintain in two places I will be converting all the photos over to Flikr links.

Lately you know, I don't blame you. It's unfortunate. I did my L3 documentation here: https://www.rocketryforum.com/showthread.php?8020-Level-3-Build-Diary and I know how much work it is (and that is back when TRF was performing well). I guess I'll kick over to Rocketry Center every so often to check on your build.
 
Lately you know, I don't blame you. It's unfortunate. I did my L3 documentation here: https://www.rocketryforum.com/showthread.php?8020-Level-3-Build-Diary and I know how much work it is (and that is back when TRF was performing well). I guess I'll kick over to Rocketry Center every so often to check on your build.

By changing everything over to linked Flikr photos I can easily maintain it in both places which is my plan now. I just write it here, and paste the entire thing with links there to the pics. I'm not ready to pull the plug here, I like it here for the most part. I hope things will improve, or at least not devolve further. This is being done to ensure that it lives two places and therefore drastically reduce the risk of complete loss. But do stop in over there, while having more forums does create a more fractured community, at least it gives some life boats if one of the ships sinks.
 
By changing everything over to linked Flikr photos I can easily maintain it in both places which is my plan now. I just write it here, and paste the entire thing with links there to the pics. I'm not ready to pull the plug here, I like it here for the most part. I hope things will improve, or at least not devolve further. This is being done to ensure that it lives two places and therefore drastically reduce the risk of complete loss.

Yeah I used Flickr too. It is still a pain to get all text and links right. I wouldn't want to do it ever again (or twice really).
 
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