Armed and Dangerous - 38 MD - Fillets

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Aksrockets

Now with 8% more aluminum
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To be honest, all my other 38mds have been garbage. They’ve flown alright but besides the up part things havn’t gone well.
My “Mach Mobile 38” was a big project for a slightly younger Alex that was new to HPR. It was glassed paper, with 1/8in glassed ply fins designed around smaller 38mm motors. It was single deploy, with a big reflective mylar streamer at apogee. The Mach Mobile flew at Hellfire a few years back on an H400vm. Good little flight, but the streamer tore and the thing free-fell from about 5,000 feet. I didn’t end well.
My next 38MD “Motor Mounts Are For Sissies” flew a few months ago. It was designed specifically to be a “fire and forget” rocket based around a single use J270. It was hand wrapped fiberglass and 1/16 in G10 fins. The “M.M.A.F.S.” was single deployment with a streamer as well. This time the streamer was made out of Nylon to prevent what happened last time with the Mach Mobile. Everything went perfectly but it came down pretty hard, hit a rock and lost 2 fins.
Neither of these 2 rockets had tracking or any kind of onboard electronics, neither of these rockets had reliable means of recovery and neither of these rockets were built to last. This new 38 MD needs to fill the hole in my minimum diameter family and stay there.

Project Goals:
• Be stable and flyable with all 38mm motors up to 21 inches long (sorry no J1000LW and J510W)
• House a Stratologger 100 for deployment and BRB 70cm transmitter for tracking.
• Weigh under 1 pound (Openrocket says 12 oz right now)
• Look pretty. Finished Carbon Fiber. Green accents.

Construction Details:
Body Tube: 3 wraps of 5.7oz Carbon. Alex style.
Fins: 1/16in Carbon Fiber. Attached with Aeropoxy and filleted with either Proline 4100 or JB weld
Nosecone: Homemade molded fiberglass. More details later.
NC coupler: The casing from the single use J270 motor.

Not really too exciting a build. I’ve got a lot on my plate already with my 2 Aeronaut projects and a few that I’ll be announcing soon (not MD but still REALLY cool). I can justify this to myself because It’ll cost me nothing. I already have all the materials. I even have an I600R that doesn’t have a home that would be perfect for the first flight.

Im in Spain right now so I can’t really do anything other then design. Give it a look and see what you think. I figured I might as well type up the thread now while I’ve got the time. I’ll be super busy with rockets and travel and friends when I get back to the US.

Screen Shot 2014-06-19 at 11.15.33 PM.png

Screen Shot 2014-06-19 at 11.16.19 PM.png

View attachment SW38.ork

Calling it the "Shockwave 38" till I think of a better name.

Alex
 
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I like it, if your going with three wraps thats half the thickness of the tube, which means different nose cone size. Maybe you can ask Tim if he can get you a lightweight nose cone like in the Darkstar Lite.


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet
 
Ill be making my own NC. Ill talk about it a bit later when i get more details.

3 wraps is appropriate. PR tubing's thickness is wayyy overkill for any 38mm flight.

Alex
 
I think this is very doable. Have you thought about recovery yet? In regards to the simulated mass of 0.75lbs, does that include the mass of the electronics and if so what is that assumed mass?

Mat
 
I think this is very doable. Have you thought about recovery yet? In regards to the simulated mass of 0.75lbs, does that include the mass of the electronics and if so what is that assumed mass?

Mat
I bulked all the "recovery" items into one 5oz mass in OR. That might be a little bit on the low side but I still have 4 oz of cushion before I hit 16oz.

The fins are .5oz the bt is 5.5 oz and the NC is 2oz. All those weights seem about right based on what I've built in the past.

Alex
 
I bulked all the "recovery" items into one 5oz mass in OR. That might be a little bit on the low side but I still have 4 oz of cushion before I hit 16oz.

The fins are .5oz the bt is 5.5 oz and the NC is 2oz. All those weights seem about right based on what I've built in the past.

Alex

Well I can give you the mass of the Sl100 and the BRB (70cm 100mw version). The Sl100 comes in at ~0.03lbs not including the battery, switch, and wires. The BRB comes in at ~0.09lbs and this mass does not include the antenna, wires, and switch. So that comes out to ~0.12lbs (~1.9oz) but you would still need to figure the sled, wire, antenna, and etc.

Mat
 
I notice that 6.1 oz carbon at AVT Composites is down to $21 a yard (for 50"). Seems like it's been $30-35 forever. Anyone seeing that with other suppliers? Good time to make those carbon rockets!

Jim
 
I notice that 6.1 oz carbon at AVT Composites is down to $21 a yard (for 50"). Seems like it's been $30-35 forever. Anyone seeing that with other suppliers? Good time to make those carbon rockets!

Jim

Jim I also noticed that. Yes, Soller Composites is also at $21 for their 5.9oz 3k 2x2 but ACP (other dealer I use often) is still at $39 for their 5.6oz 3k 2x2.
 
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Ill be making my own NC. Ill talk about it a bit later when i get more details.

3 wraps is appropriate. PR tubing's thickness is wayyy overkill for any 38mm flight.

Alex

Looking forward to it.

I do agree that the FW tubes are a bit overkill on the weight.

Besides making your own is more fun.


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet
 
I'll be following. I think you should stick with the name "shockwave 38" sounds good. You definitely need to get some cool decals from Mark.


Sent from my iPod touch using Rocketry Forum
 
I am looking forward to this.

I am right there with you Alex tubing for 38mm is just too thick walled. I just measured by custom carbon tube and it comes in at 1.5mm.
 
That AVT price is pretty good! AVT has slightly less expensive vacuum bagging supplies then soller so I think my next order will be through AVT.

Glad to see a few of you are following along.

I like the name "Shockwave 38" but my original Shockwave series of rockets were based around a Shockwave brand NC. I had plans for a Shockwave 38 project a year or so ago but they fell through. For this project, I would just buy a SW 38 NC, but Shockwave is out of business. I feel like I need to save the name for when I can get my hands on one.
The new name I came up with is "Armed and Dangerous". I like that.

Work begins Wendsday.

Alex
 
That AVT price is pretty good! AVT has slightly less expensive vacuum bagging supplies then soller so I think my next order will be through AVT.

Alex

I have only ever bought breather cloth from Soller Composites as far as bagging materials; I seem to remember that Soller didn't have much of a selection. I tend to get most of the bagging materials from ACP composites and AVT with ACP being my go to. Depending on what you need and the quantities ACP might have the best prices. I have never bought CF from them though and I think ACP is a bit more expensive with their cloth, if I remember correctly. Just thought I would share another place that you can get the bagging materials possibly cheaper from. However if you want to source the fabric and materials from the same place then AVT might be the way to go; I personally could care less about getting everything from the same place and tend to get the materials from one place and fabric from another.

Cheers.
 
I got a ton done on this today!
First up, I cut the fins. Nothing fancy just a jigsaw and some 1/16in CF from McMaster-Carr.
image.jpg
Here they all are, stack sanded and what not.
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They're tiny! Only a 1.25 inch span.
image.jpg
Putting bevels on fins this thin isn't my favorite thing.
image.jpgimage.jpg

I also found the time to lay up the tubing today! And SURPRISE! It's Carbon / Kevlar. I had some lying around and this seemed like a good application (Thanks Kenstarr!). I know, I know. Kevlar is a b***h to work with. To finish the tube I'll need to give it a coat or two to prevent sanding into the fibers of the Kevlar.

Before:
image.jpg
After:
image.jpg

Thats all for today folks!

Alex
 
I guess that's NOT all for today. Working on my little 38MM nosecone mold at the moment. The only 38MM NC I have is a LOC plastic one so that's what I'm using for a blank.

I started by cutting the NC shape out of a think sheet of aluminum. I looked all over the house for something better to use. Usually I use white board pieces, but I couldnt find any so I had to settle for the aluminum. I really hated cutting aluminum.
image.jpg
All cut out:
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I made a little frame for it out of scrap wood
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It fits!
image.jpg

Alex
 
My god Alex, what happened to your workspace?!?!

All I see is the piece you are working on and a couple of relevant tools/supplies. What have you done?!

s6
 
Prepping for the first side of the mold.

I gave the underside a hot glue "fillet" to keep epoxy from leaking down there.
image.jpg
Next up was a coating of mould release wax.
image.jpg
Followed by a coating of PVA mold release.
image.jpg
I'll do the first side tomorrow morning.

Alex
 
Hey look! I took the peel ply off the tube!

Im pretty happy with the quality of it. No real imperfections. A few tiny pinholes here and there but those will go away easy. I took it out to my workshop and weighed it. 4.3 oz! Not bad at all! Id estimate that the final tube weight will be something like 4.5 - 4.7 oz (right now, its 2 inches longer then it will be, so that's 4.1 for the bare 28in tube plus .5oz for epoxy coatings.)
image.jpg

image.jpg

image.jpg

Alex
 
Splendid job Alex, that red Kevlar is just awesome. I can't wait to make a few of those.


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet
 
The red black brings me back. My first ever composite rocket, like circa 2000 had tip to tip with that stuff. I made this about five years ago, too bad the gel coat got messed up.

Old Cruddy.jpg

Its a 38mm VK profile made from one of Adrian Adamson's plugs. I think I still have some of that hybrid cloth...
 
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The red black brings me back. My first ever composite rocket, like circa 2000 had tip to tip with that stuff. I made this about five years ago, too bad the gel coat got messed up.

View attachment 175810

Its a 38mm VK profile made from one of Adrian Adamson's plugs. I think I still have some of that hybrid cloth...

Very cool! I wish i could use a Carbon/Kevlar NC but i would loose tracking capabilities. If ive got the time maybe ill make 2. One out of CF/kev and one out of FG.

Alex
 
I got up bright and early to do one half of the NC mold.

First i mixed some filler into the epoxy and filleted the edges to give the glass a more gentle transition to the back board.
image.jpg

After a few layers of 4oz and 6oz glass:
image.jpg

With the extra epoxy i coated the tube.
image.jpg

Alex
 
I noticed you did not glass the nose cone shoulder for the mould. Are you going to make a coupler that will act as the nose cone shoulder?


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet
 
Got a chance to sand down the previous coat and give it another. It looks a lot better.

image.jpgimage.jpg

Alex
 
Very shiny, keep up the good work. I just think that red kevlar is awesome.


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet
 
Your 38mm bird is going to be a lot sexier than mine.

Do the fins feel stiff, that is my biggest worry about 1/16".
 
Your 38mm bird is going to be a lot sexier than mine.

Do the fins feel stiff, that is my biggest worry about 1/16".

The ones that I made for my speedy gonzales rocket are less thick and they feel pretty stiff. I have no doubts he will be fine with those.


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet
 
Anymore progress?


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet
 
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