Carbon Prepreg Airframe build for the Loki 54/4000 - Fins Attached

tfish said:

why not use 2mil mylar? I'd be afraid that stuff you linked to would bunch up during the mandrel removal. Also do not use any tape, under your layup, to affix your release film to the mandrel. It's amazing how much a 1/2" piece of tape can screw things up.

Tony

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Thanks Tony.

I seem to remember that 2mil mylar is what I used to use. But now I can't seem to find it in any of the usual places. I have a feeling I'm looking too hard. And is it good to 350ish degrees?

Update: Found some on ebay. And yup, allegedly good to 400f.

How close is your mandrel to 54mm? Ive always stayed away from aluminum mandrels out of a fear that they wouldnt match similar sized components exactly.

Alex

Aksrockets said:

How close is your mandrel to 54mm? Ive always stayed away from aluminum mandrels out of a fear that they wouldnt match similar sized components exactly.

Alex

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The mandrel is dead nuts 2.125", or 54mm. In this situation I'm not too concerned with now it fits with standard components because there wont be any. Maybe a coupler, but the I.D. should be pretty spot on.

Wayco said:

How long will your fincan need to be for that monster motor? Are you going to use the Aeropac internal motor retainer? I just got one for my 54mm Blackhawk, and it's pretty slick. Wish I had a couple more inches of fincan for the drogue streamer, tracker and shock cord, it's a tight fit.

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The airframe tube will only be about 2" longer than the motor case not including the forward closure. All the recovery and electronics will fit in the 7:1 VK nosecone. The Aeropack retainers are really cool but take up too much room in this situation. Motor retention will be through the recovery harness.

What motor are you flying in the blackhawk? I'm excited to see that!

watheyak said:

The airframe tube will only be about 2" longer than the motor case not including the forward closure. All the recovery and electronics will fit in the 7:1 VK nosecone. The Aeropack retainers are really cool but take up too much room in this situation. Motor retention will be through the recovery harness.

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Sweet Jeebus. How does that sim? That sounds like ridiculous velocity/altitude to me.

Please don't shred, please don't shred, I wanna see this soar...

Zeroignite said:

Sweet Jeebus. How does that sim? That sounds like ridiculous velocity/altitude to me.

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Sweet Jeebus is right. I'm still working out the nosecone volume/fatnessness but looks like slightly above mach 3, and ~35,000'

Zeroignite said:

Please don't s****, please don't s****, I wanna see this soar...

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Please don't use that word. You're not a Baseball fan are you?

watheyak said:

The airframe tube will only be about 2" longer than the motor case not including the forward closure. All the recovery and electronics will fit in the 7:1 VK nosecone. The Aeropack retainers are really cool but take up too much room in this situation. Motor retention will be through the recovery harness.

What motor are you flying in the blackhawk? I'm excited to see that!

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So the recovery harness attaches to the forward closure? Like an eyebolt screwed through a bulkhead at the top of the fincan? Not sure how the Loki hardware is configured, other than being snap rings.
The Blackhawk will probably make it's first flight on a J430 White Thunder. It's small enough that I can (maybe) see the deployment sequence and keep an eye on it's descent. I built an Eggfinder into the N/C for higher flights. Theoretically, an L935 will take it over 17k. I bought the CTI tailcone retainer, which might help get a little more altitude, but nothing like yours.
Do you have a launch tower? I haven't put rail buttons on mine yet, hoping I won't need to if someone has a tower I can fly a 3 fin 54mm MD rocket on.

Wayco,
I would think you would get 20+ for sure on a MD L935 flight… No rail buttons If you are planning on launching anywhere I will be at, then you can use my tower no problem.

watheyak said:

The Aeropack retainers are really cool but take up too much room in this situation. Motor retention will be through the recovery harness.

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Your sims seem down the line for what I would expect.

In regards to the Aeropack retainers I have ran into that very same problem… 3 times lol. Here is my solution. This is for a CTI motor but it could be modified if needed.

Note: I forgot to add the washer and eyebolt that screws into the forward retainer and thus holds it from falling out. Also the size of the holes are not accurate, they show that the retainer is bolted in through the airframe.





Mat

Wayne,
I don't have a tower anymore. James D does I think. And Scott H does but I'm not so sure it'll get small enough for us. This rocket is probably going to end up having 4 fins anyhow, so there will be a tower build involved.

A5tro, I've been subscribed you your build threads. I like the retainer idea a lot. This retention and recovery scheme for this bird is pretty unconventional. I'll wait to spring that bit of mayhem until the time comes, lest you all write me off as a crackpot.

watheyak said:

A5tro, I've been subscribed you your build threads. I like the retainer idea a lot. This retention and recovery scheme for this bird is pretty unconventional. I'll wait to spring that bit of mayhem until the time comes, lest you all write me off as a crackpot.

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I would use those threads at the top to your advantage.
Speaking of my threads… I need to go update them someday haha. I am sure you already mentioned this, so pardon me, but when/where do you plan on launching this?

On a slightly off topic post; from your first photograph I see you are a pilot? Where and what do you fly? I fly mostly (as of now) out of KSGR in a "wonderful," C172.

A5tr0 An0n said:

I would use those threads at the top to your advantage.
Speaking of my threads… I need to go update them someday haha. I am sure you already mentioned this, so pardon me, but when/where do you plan on launching this?

On a slightly off topic post; from your first photograph I see you are a pilot? Where and what do you fly? I fly mostly (as of now) out of KSGR in a "wonderful," C172.

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If it's finished in time I plan on flying it at Balls in September. If not, I'll fly it at TRAPHX's Eagle Eye site.

Nice, I've never been to Sugarland, but I did make it to Cleveland, Texas a while back. Texas is big. I probably have a few thousand hours in a 172. Some wonderful, some not. For the past 12 years I have been a flight instructor at a large flight school in Phoenix, AZ. It's a great place to be and I have a ton of fun there. It's a good group of people. As my "grown up" job, I fly a Citation Encore and a Pilatus PC-12 about 8 days a month for a part 91 outfit based at Sky Harbor.

If you want to fly CTI Cases you probably need to add a shim. I wrapped mine in peel ply to get some extra space.

watheyak said:

If it's finished in time I plan on flying it at Balls in September. If not, I'll fly it at TRAPHX's Eagle Eye site.

Nice, I've never been to Sugarland, but I did make it to Cleveland, Texas a while back. Texas is big. I probably have a few thousand hours in a 172. Some wonderful, some not. For the past 12 years I have been a flight instructor at a large flight school in Phoenix, AZ. It's a great place to be and I have a ton of fun there. It's a good group of people. As my "grown up" job, I fly a Citation Encore and a Pilatus PC-12 about 8 days a month for a part 91 outfit based at Sky Harbor.

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Well if you fly it at BALLS then I will be there and look forward to seeing it. On a secret note this is a motor I want to build for, hopefully later this year (post BALLS).

It is a nice airport. Jets and props. I have never been to Cleveland, did you like it? I am actually working towards my CFI, CFII, and MEI. I would like to eventually go jet. The citation is nice! How do you like flying her? Sounds like a very fun job. I actually work on the opposite side… professional/technical diver. Basically I train others to become divers and I go on cave diving explorations. I am just doing all of this while I finish up school. Sorry for the off topicness lol.

Mat

A5tr0 An0n said:

Basically I train others to become divers and I go on cave diving explorations. I am just doing all of this while I finish up school. Sorry for the off topicness lol.
Mat

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Hope it's ok to ride this tangent a bit, but sweet mother of Jebidiah cave diving is hardcore. I've done my share of abovewater caving and there's plenty of hazard there... respect, man. And stay safe ok?

Boxes of rocket goods started pouring in today. Boring stuff mostly. Flash breaker tape. Aluminum polish. yadayada. Going on a trip this weekend, so not much else to share. Next step is to bake a couple short practice tubes. I'm finalizing the lay-up schedule, now that I think I've settled on the tube's actual thickness. I found a cool spreadsheet to help that I will attach.

A5tro, I'm still very new in the jet. And while it's full on Star Trek with all the neat-o bells and whistles, it has a tendency to make me feel woefully inadequate as a pilot. (don't worry, the guy I fly with is an amazing pilot) I'll give you an update when I get a few hundred more hours in it.

View attachment Airframe_cloth_requirements+cf.xls

watheyak said:

Boxes of rocket goods started pouring in today. Boring stuff mostly. Flash breaker tape. Aluminum polish. yadayada. Going on a trip this weekend, so not much else to share. Next step is to bake a couple short practice tubes. I'm finalizing the lay-up schedule, now that I think I've settled on the tube's actual thickness. I found a cool spreadsheet to help that I will attach.

A5tro, I'm still very new in the jet. And while it's full on Star Trek with all the neat-o bells and whistles, it has a tendency to make me feel woefully inadequate as a pilot. (don't worry, the guy I fly with is an amazing pilot) I'll give you an update when I get a few hundred more hours in it.

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What thickness did you decide upon?

Is it the lag from when throttling the engines? I take it this is not your first glass cockpit. I am sure it has a warning for everything though lol. Look forward to hearing the update. Maybe one day I will fly into PHX.

A5tr0 An0n said:

What thickness did you decide upon?

Is it the lag from when throttling the engines? I take it this is not your first glass cockpit. I am sure it has a warning for everything though lol. Look forward to hearing the update. Maybe one day I will fly into PHX.

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I had quite a bit of time to think about the thickness this weekend, and now I'm back to being undecided. The carbon is .005" thick. I'm leaning toward 12 layers. 2 hoop -> 8 longitudinal -> 2 hoop. But I have some freedom in that it doesn't need to play nice with any standard components and the airframe tube is at no point unsupported. It's either backed my motor case or nosecone shoulder/coupler. So I just want to make sure I'm exploring all possibilities. Like maybe even going thinner. I have yet to run the thinner version through RASaero. How much will a few hundredths really get me altitude wise? I think I will have a better idea once I do that as well as make some practice tubes.

A5tro, the jet itself flies really nice. It's not like you're really changing throttle setting much, even on landing. The issue for me, and most pilots when they get into a new plane, especially one as fast as this one, is that there is twice as much to do in half the time. It is incredibly busy from engine start to 10,000' and same thing on the way back down. I'm about ten miles behind that plane. I feel like a student all over again, because I am.

Started the polish on the mandrel. Cleaned it up with some Simple Green, then sanded starting at 600 all the way to 2000 grit. Cleaned it again then started in with the Mothers Mag and Aluminum Polish. So far, so good and only 70" to go

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watheyak said:

Started the polish on the mandrel. Cleaned it up with some Simple Green, then sanded starting at 600 all the way to 2000 grit. Cleaned it again then started in with the Mothers Mag and Aluminum Polish. So far, so good and only 70" to go

View attachment 175594View attachment 175595.

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Wow, nice shine on that aluminum.

you really don't need it to be super polished but it wont hurt. Id get some jewelers rouge and a bench mount buffing wheel if I had to do much of it. You can probably get by with a die grinder setup

This is the tube I used

flynfrog said:

you really don't need it to be super polished but it wont hurt. Id get some jewelers rouge and a bench mount buffing wheel if I had to do much of it. You can probably get by with a die grinder setup

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I got the mandrel reasonably polished by hand, then cut it down to size. I now have a 16" mandrel for some practice tubes.



And it's a special brand of creative problem solving that occurs while wandering the aisles of Lowe's at 9:30pm.

Here's the fruits of the Lowe's wander, my new tube rotisserie.



And since that's painfully boring, here's a picture from today of Edwards from 25,000'

I started on a 10" long practice tube last night. This is proving to be a very educational project, as I am in completely uncharted waters. There isn't a ton of information this specific method online. I'm feeling very fortunate to have a ton of this prepreg with which to give myself an education. I have room for trial and error and mistakes, which I wouldn't if I were paying for it.

The mandrel for this is a 16" section of the original mandrel. It was polished, then a wrap of 2mil mylar was wrapped around it per in Jarvisonian method. That mylar was waxed with Hi-Low mold release wax, which I have my doubts about.


Then the ends were added to the mandrel and the mandrel put on the rotisserie.



Then came the first hoop-oriented wraps. Two of them. My first problem was that the prepreg, wouldn't stay tacked down to the waxed mylar, and it was some trick to get it wrapped around on itself tightly. I have some thoughts about how to do this more effectively the next time. The other problem is that this stuff is STIFF! I could hear the fibers cracking as I formed it to the diameter of the mandrel. It is high-modulus, and probably not the right application for this small radius bend. I have some ideas how to deal with that as well.


Next came the longitudinally oriented fibers. Eight of those. These went on very easily. this stiff is fun to work with like this. Everything tacks down and stays put. Just make sure you get it put down in the right place the first time!


And then the last two hoop wraps.


I got in a hurry for some reason on that last hoop wrap and things for a little ugly. We'll see how some of those wrinkles affect the surface finish under the heat shrink tape. I know it's not ideal structurally, either.

After that it was put in a plastic bag and put bag with some desiccant packs and put back in the freezer. Tonight it was removed from the freezer and Dunstone heat tape was wrapped in a half overlap spiral around the tube. I forgot to get pictures of this. It is now in the oven, ever so slowly ramping to 260f. It'll stay there for three hours, then ramp slowly again to 350f and hold there until morning. Then I'll let it cool, and inspect the goods.

Also thanks to Tfish for suggesting the mylar. It's just the tight thickness/stiffness.

is any of the blue tape stuck to the mandrel?

Tony

tfish said:

is any of the blue tape stuck to the mandrel?

Tony

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Nope, the Mylar slides freely.

watheyak said:

Nope, the Mylar slides freely.

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Nice! I could not tell by the photos. I've had the smallest piece of tape holding the mylar to the mandrel give me fits!

Tony

Wow, this brings back some great memories. Thanks for the documentation! Looks great so far.

What weight is that fabric?


Alexander Solis

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