Pocket Rocket Build

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Jordz
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Pocket Rocket Build

Postby Jordz » Mon Oct 31, 2016 11:54 pm

Hey guys. I'm doing a slow build on my first carbon fibre rocket. I'm putting this build thread up for anyone interested as i have a few ideas i'm going to try as i go along, and if they are successful all the details will here for anyone wanting to give it a shot too.

The aim of this build is to practice a few techniques that are new to me. Carbon fibre laminating, through body fin mounting, streamer recovery to name a few. The other side of it is that id love to attempt an F motor altitude record if i can get my hands on the appropriate motors. If not, its excellent practice and a fun build regardless.

Here is the design in Open Rocket:
OR Sim.png


Even with the biggest heaviest 29mm motor i could sim the stability is 1.35 calibres. I think i can actually raise this further by taking some of the weight savings i have made on the body and adding weight to the tip of the nose cone. The body will be made of a nose cone and a tail cone, no tube section at all. This is to allow a little extra packing width for recovery gear while reducing drag at the rear. In the middle an alloy motor block will double as a strengthening ring/recovery mount point. Recovery will be via a large reflective mylar streamer. With a maximum predicted mass of 190ish grams fully loaded a streamer landing should be pretty gentle.

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Jordz
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Re: Pocket Rocket Build

Postby Jordz » Tue Nov 01, 2016 12:04 am

My tailcone has been constructed over the last weekend. To do this i turned some floral foam on a VERY diy lathe (read: power drill in a bench vice) to the sizes i needed. Not only was it comical, it was messy. But, it did work. With a tail cone and a nose cone turned to the dimensions i needed I then proceeded to start laminating the tail cone. This is my first time using carbon fibre on a more "complex" shape so i went at it pretty slow. Ive only used two layers for this piece, followed by a resin wipe for a good finish after sanding.

The end result was a lot better than I could have imagined. Floral foam doesnt melt under the resin so the shape of the mould held perfectly, the part separated nicely when dry and it looks the goods too. Ill post a few pics of the process as soon as i can figure out why the forum keeps saying they are invalid haha

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Jordz
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Re: Pocket Rocket Build

Postby Jordz » Wed Nov 02, 2016 8:35 am

Apparently my files were far too large, i guess that explains why my phones storage was getting full so quickly haha.

DSC_0676-1.jpg
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DSC_0677-2.jpg
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^ This is my poor mans lathe. Its cheap, nasty, and does the job very well. I probably will either make or buy a desk lathe one day, but for the time being this was more than suitable for the job. Don't knock it until you've tried it :) The block is held on just using a 13mm drill bit that has been pushed in. It is important you push AND twist it in, otherwise if you cut a circular hole the bit wont grip the foam.

DSC_0782-2.jpg
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^ Finished product from the lathe. They have both been made 0.3mm undersize in the body areas to allow for the thickness of the carbon fibre, except for the tail cone's hole which is exact.

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Jordz
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Re: Pocket Rocket Build

Postby Jordz » Wed Nov 02, 2016 8:43 am

DSC_0783-1.jpg

^ The carbon was impregnated on the table and then hand laid. It was then given a rough sand followed by a resin wipe. This is the finished result. Its even more beautiful than the camera makes it look :D

DSC_0793-1.jpg

DSC_0792-1.jpg

^ I can live being marginally out on the body size of the nose come, but my real happiness is that perfect 29mm hole for the tail end. First (and probably last) time ive got it bang on first time around.

That's the extent of the project thus far, but ill be doing the nose cone soon. Pics will follow when i do.

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SpaceManMat
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Re: Pocket Rocket Build

Postby SpaceManMat » Wed Nov 02, 2016 9:06 am

Look good. Supprised you got the drill working like that. I've tried similar with mixed results.
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 10,849 feet
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

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Jordz
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Re: Pocket Rocket Build

Postby Jordz » Wed Nov 02, 2016 9:30 am

Were you using foam or wood on your drill? As it was the foam was probably at the edge of feasible, i dont think you could even use balsa like this.

jhurst7
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Re: Pocket Rocket Build

Postby jhurst7 » Wed Nov 02, 2016 4:49 pm

How did you get your nosecone so exact, did you just do it by hand?
L1- AMRAAM 2- H54

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Jordz
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Re: Pocket Rocket Build

Postby Jordz » Wed Nov 02, 2016 6:34 pm

I measured the foam core as i carved it multiple times, allowed for the thickness of the carbon fibre, measured it all again when it was dry, sanded the high points and then gave it a wipe of resin after to give it a glassy smooth surface. Essentially just good old fashioned "measure twice, cut once" approach and a healthy dose of patience. Ive learned from past experience that i personally tend to ger over-excited and impatient, when that happens i generally stuff the job up, so self control is the biggest factor for me haha

That being said, to be at a perfect tolerance on one end and pretty damn close on the other is a personal best for me. Id say luck played a small part too.

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Re: Pocket Rocket Build

Postby SinfulDarkLord » Thu Nov 03, 2016 5:04 am

Jordz wrote:Apparently my files were far too large, i guess that explains why my phones storage was getting full so quickly haha.

DSC_0676-1.jpg


DSC_0677-2.jpg


^ This is my poor mans lathe. Its cheap, nasty, and does the job very well. I probably will either make or buy a desk lathe one day, but for the time being this was more than suitable for the job. Don't knock it until you've tried it :) The block is held on just using a 13mm drill bit that has been pushed in. It is important you push AND twist it in, otherwise if you cut a circular hole the bit wont grip the foam.

DSC_0782-2.jpg


^ Finished product from the lathe. They have both been made 0.3mm undersize in the body areas to allow for the thickness of the carbon fibre, except for the tail cone's hole which is exact.


I will have to give that cheap set up a try. Would make it easier to sand all those ridges left behind from the shrink tape.

Great job on the nose cone and tailcone.


Sent from my iPhone using Tapatalk

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Re: Pocket Rocket Build

Postby RedPhenix » Thu Nov 03, 2016 10:52 am

The attachment DSC_0677-2.jpg is no longer available


^ This is my poor mans lathe. Its cheap, nasty, and does the job very well.

Doesn't everyone have a lathe like this? Skateboard ball bearings - the cheap and nasty kind - a couple of bits of scrap wood, some threaded rod, and Nic is your uncle.

Cheers

Noel
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Jordz
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Re: Pocket Rocket Build

Postby Jordz » Thu Mar 09, 2017 10:10 pm

A small update and some pics. The struggle to get a particular single 29mm F motor i need into Oz is proving to be a difficult issue, so motivation is at an all time low. At this point im planning on maybe moving to a 24mm instead, but i wont let that get in the way of finishing this one haha. This will still be an awesome little dart if I can get it off the ground, and will make for nice cheap flights. Forgive the poor photo quality, my phone has seen better days :lol: The next step will be to trim the top few millimetres from the body tube, and to add the motor block and lip for the nose cone to sit on. Hopefully ill get that done this weekend.



Image

^ Fins cut from balsa and sanded on one side of the trailing edge. Im not sure how much spin this will generate as its only a small bevel, but a little more stability never hurt anyone. These got a layer of 200gsm woven fibreglass for strength as 3mm balsa doesn't like hard landings, soft landings or even firm glares in its direction.

Image

^ Slots cut in the body tube and fins are glued into place. Fillets were done with 'Rapid Fix' which is an instant two part epoxy. Simply put the powder on, smooth it out and drip the liquid half on. It didnt give me quite as smooth a fillet as i had hoped but im not sure if thats due the the fact im working on quite a small scale or its just not the best product for the job. Either way, next time ill probably use JB Weld.

Image

^ A wet and dry sand and lick of paint. The paint colour is literally called "Rocket Red' so it was a real no brainer. The red contrasts incredibly well with the CF weave, however my camera made every effort to ensure you cant see that. Ill try get a better picture in daylight eventually instead of kitchen light.

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Jordz
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Re: Pocket Rocket Build

Postby Jordz » Thu Mar 09, 2017 10:15 pm

I forgot to add, total weight for the bottom half of the pocket rocket is 27g at this point, a fair bit less than the predicted 34g. Every gram i lose below the CP is another gram i can add above it to increase stability, meaning I can shave a little off the length off my fin tips. Smaller fins = less drag = higher altitude. At this scale it all counts, at least in my head ok? Just gotta find a way to get that friggin motor :lol:

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SpaceManMat
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Re: Pocket Rocket Build

Postby SpaceManMat » Fri Mar 10, 2017 9:10 am

Looks real nice.

Make sure you don't alter your fins till the end. Weight has a habit of finding its way back onto the rocket. Also check CG first, it may not be where you think it is.
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 10,849 feet
Largest Motor: CTI 1115J530 IM
Current Project: X Wing


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