Novice first scratch built

Discussions for scratch builders. For the enthusiast that builds from the ground up. Tell us what you've built and what projects you working on in the space race.

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Rex Fynns
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Novice first scratch built

Postby Rex Fynns » Mon Sep 18, 2017 8:04 pm

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A few years back I ran into a fellow wandering the Atacama desert in Chile with his good wife, reckons his name was Nic and over a drink or three he regaled me with stories of rockets, he seemed to know a thing or two.

Anyways one thing and another I now have a bug so knocked up a prototype to gauge my skills before progressing to the next one.

The key was to test my build skills and utilise my aviation background (see if I've been paying attention and all that).

This rocket is 24mm cardboard tube with 2 layers of 10g/m2 carbon tissue 750mm long, a commercial cheap nasty nose cone where the Jolly Logger 2 just fits in. There is a 22mm x 150mm avionics pod which carries the Eggfinder and 7.4v LiPo battery. The fins are of my own design based on a low aspect ratio trapezoid planform with diamond facet LE/TE and tip made from balsa/carbon fibre sandwich.

Basic empty weight is 54 grams and take off weight is 173 grams all driven by a Estes E9-6.

I nutted out a launch rail system comprising 3 x 10mm x 850mm steel rods into a tripod base plate with exhaust hole to the side, which adds a nice visual touch at ignition and keeps the dust down.

I stuffed up some measurements along the way and ran short of room for the 2m mylar streamer recovery system so resorted back to a nasty 30cm estes parachute. I paid the price for this later.

The initial static deployment tests using a C6-7 revealed the snug 1oz avionics tube behaved much the same way a 1oz solid slug from a shotgun does just a little slower. The Kevlar lanyard system and body attach were fine and showed great structural resilience but the cheap nose cone attach failed and the nose cone and avionics tube cleanly separated. Fortunately I have a tin roof and heard the whole lot land some 15 seconds later. I don't have neighbors so no great safety issue, I probably should have used a dummy weight though and not the $300 worth of fresh built and new avionics but it was a good shake down for it and logger and GPS are doing fine.

Two 3mm vent holes were then drilled into the body at the coupler junction to vent and reduce ejection charge pressures, it worked well on the next test, with dummy weights this time.

Well spank my a**e and call me Charlie than damn thing went pretty close to expected, the whole thing was done without reference to any software modeling and I figured (guessed) about 2500' give or take 500 and about 220 kts would be the result.

I got 1900' and 235kts and straight as an arrow with no rotation, at least from what I could see. Absolutely thrilled with my first launch of my first scratch built and only half a dozen prior launches with an Estes kit.

Deployment occurred prior to apogee (I think) and gave the body a neat little 15mm zipper and shredded most of the chute riser lines off, descent rate was 8m/s which cracked one fin when it failed to miss the earth on return.

20 hours to build and test and flight time of 66 seconds in total, might 2 stage it for its next launch before retirement.

Now to scale up using 32mm phenolic, staged timer ejection and my own engine, target 5000' and 450kts, then after that the holy grail for light thin rockets :twisted:

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Re: Novice first scratch built

Postby SpaceManMat » Tue Sep 19, 2017 8:51 am

Not too bad an effort 8) , pity about the zipper. One of the benefits of using simulation software is to able to get a grip on how fast the thing is moving when the chute come out. Better still if you kit yourself up with say some 24mm CTI reloadable motor hardware then you can adjust your deployment timing of your reloads as required. And you can go much higher. Keep up the good work.
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Re: Novice first scratch built

Postby Rex Fynns » Tue Sep 19, 2017 10:31 am

G'day Matt,

Thanks,

I am stubbornly resisting software modeling even in light of the boundless benefits, unfortunately with fixed timing deploy it is what it is and the 15mm zipper is a pretty good gauge of velocity, I'll pick 50kts and put a mark along side of it for future reference to early deployments and velocity. :lol:

Sadly I only have 8 E9's left and 6 of them are 4 second delays so the problem will only worsen. But this was only ever a test build so can be retired and move onto the next one.

Commercial reloadable and adjustable engines would be fantastic, unfortunately I can't buy them and even if I could the freight appears to be about $80.00.

My next rocket will be another scratch built including the motor with a separate timed deployment charge so should overcome this issue (and discover another).

Keen to find out if the piece of 1" graphite bar I purchased can be successfully lathed into a De Laval nozzle, perhaps I should be looking at commercial casings and nozzles, we'll see what is do-able.

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Re: Novice first scratch built

Postby kopius » Tue Sep 19, 2017 1:40 pm

Rex Fynns wrote:Commercial reloadable and adjustable engines would be fantastic, unfortunately I can't buy them and even if I could the freight appears to be about $80.00

Hi Rex, neat looking build.

Why can't you buy reloadable motors and where did you get the price of $80? that is the cost of J motors.

Also, if you are not aware, please make sure you are using the Australian compatible eggfinder.
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Re: Novice first scratch built

Postby Rex Fynns » Tue Sep 19, 2017 8:29 pm

G'day Kopius,

The $80 freight component for an engine is from Australian Rocketry and applies to a single $2.00 igniter as well as an engine. In my state it is effectively illegal to have, use or transport a rocket engine. Jet engines are fine though, but developing a working pulse jet is a real pain all mine fire one pulse and die, oh well I'll keep trying.

So I figure any retailer will get nervous about supplying motors to the point of being unobtainable.

If someone knows otherwise I'm all ears.

Eggfinder is on 921 Mhz

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Re: Novice first scratch built

Postby kopius » Tue Sep 19, 2017 8:39 pm

Ok so you are quoting dangerous goods in general which is transported the same way wether it be a single e-match or a pallet of rocket motors. It is always more economical to get more DG in a single shipment than lots of small shipments. Please send an email to info@ausrocketry.com.au with some items you are after and your address (or at least postcode) for an accurate quote. If you are saying $80, you must be quite remote.


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Re: Novice first scratch built

Postby Rex Fynns » Tue Sep 19, 2017 10:28 pm

The problem is in the development stages one doesn't exactly know what ones needs are so small shipments are inevitable, from my perspective it's more about scratch built development rather than numerous launches. The kick for me is to take an idea from neural level to tangible successful result without failure whilst expanding the envelope, long slow strides.

The other issue is what retailer wants to jeopardies their business by shipping an illegal sale. The most liberal purchase place at present is eBay and all that is available are D and below, a range of motors just capable of sustaining the interest level of supervised child. Even here I had a supplier warned off by eBay for selling to me.

I am 3 hours from a capital city on a major arterial route and the $80 for freight is the published Australian Rocketry figure. I have spoken with Blake but unfortunately it didn't lead anywhere.

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Re: Novice first scratch built

Postby kopius » Tue Sep 19, 2017 11:18 pm

Rex Fynns wrote:The problem is in the development stages one doesn't exactly know what ones needs are so small shipments are inevitable, from my perspective it's more about scratch built development rather than numerous launches. The kick for me is to take an idea from neural level to tangible successful result without failure whilst expanding the envelope, long slow strides.

The other issue is what retailer wants to jeopardies their business by shipping an illegal sale. The most liberal purchase place at present is eBay and all that is available are D and below, a range of motors just capable of sustaining the interest level of supervised child. Even here I had a supplier warned off by eBay for selling to me.

I am 3 hours from a capital city on a major arterial route and the $80 for freight is the published Australian Rocketry figure. I have spoken with Blake but unfortunately it didn't lead anywhere.

Interesting, this is Blake. I am curious as to where we supposedly got to and again encourage you to send an email with some things you are chasing so the freight can be looked into.

The website is a powerful tool, but works on automation so sometimes can be tweaked manually.


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Re: Novice first scratch built

Postby Rex Fynns » Tue Sep 26, 2017 8:28 pm

G'day Blake,

From recall you were going to call back, but I suspect you got snowed under, something about a new shed.

I sent an email to you at info@ausrocketry.com.au as you requested back on the 21st, I haven't heard back did you get it?

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Re: Novice first scratch built

Postby kopius » Sun Oct 01, 2017 1:01 pm

Ahhh, yes i remember. I just sent you an email and checked back as we tried to call you 3 or 4 times, but kept getting an unavailable message, so emails were sent instead.

Playing a bit of catchup as we have (mostly) finished the shed and moving stock and equipment around.
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Re: Novice first scratch built

Postby Rex Fynns » Sun Oct 01, 2017 9:22 pm

Thanks Kopius for the response, I'll up date my details with you as getting nothing by phone or email.

Moving forward, how do you overcome the issue of selling motors to a SA customer whilst it is illegal to posses, transport or use a rocket motor in SA without a permit and given the onerous requirements to jump through a dozen bureaucratic hurdles for a short lived permit how do we go about this.

I get the distinct impression it is not able to be done other than in a shadowy manner away from prying eyes.

We simple South Aussies need enlightening (on many levels).

Through me a bone.

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Re: Novice first scratch built

Postby kopius » Sun Oct 01, 2017 9:35 pm

Rex Fynns wrote:Thanks Kopius for the response, I'll up date my details with you as getting nothing by phone or email.

Moving forward, how do you overcome the issue of selling motors to a SA customer whilst it is illegal to posses, transport or use a rocket motor in SA without a permit and given the onerous requirements to jump through a dozen bureaucratic hurdles for a short lived permit how do we go about this.

I get the distinct impression it is not able to be done other than in a shadowy manner away from prying eyes.

We simple South Aussies need enlightening (on many levels).

Through me a bone.

The SA government dropped the ball to the point they actually put in writing the United Nations are wrong... go figure.

Anyway, their ‘permit’ is as good as a high 5 to any group that has a permit, so really means nothing and at a meeting with them they acknowledged exactly that. Nothing “shadowy” about it, just an inability/unwillingness to understand what they are dealing with.

As previously stated, let us know what you are after and I am sure this can be accommodated.


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