First Scratch Build

Discussions on low powered model rockets using E powered motors and below.

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Roco
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Re: First Scratch Build

Postby Roco » Mon Aug 03, 2015 4:17 pm

Got the fins cut over the weekend, just dry fitted them to check the fit.
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Lister
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Re: First Scratch Build

Postby Lister » Mon Aug 03, 2015 4:47 pm

Looking good mate.. you cut them yourself?

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Re: First Scratch Build

Postby Roco » Mon Aug 03, 2015 5:38 pm

Lister wrote:Looking good mate.. you cut them yourself?

Yep, cut a template out of sheet steel and clamped that on top of the balsa and cut it with a fresh Stanley knife.

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Re: First Scratch Build

Postby Viking » Mon Aug 03, 2015 6:51 pm

Looks great!
The grain should run parallel to the leading edge for balsa fins, if it runs parallel to the body tube they can snap easily. Might be okay if you're going to paper them.
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Re: First Scratch Build

Postby Roco » Mon Aug 03, 2015 7:01 pm

Viking wrote:Looks great!
The grain should run parallel to the leading edge for balsa fins, if it runs parallel to the body tube they can snap easily. Might be okay if you're going to paper them.


Might need to cut a few from the other sheet of balsa then. How big of a difference does it make?

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Re: First Scratch Build

Postby Lister » Mon Aug 03, 2015 7:07 pm

Good point. Yeah cut a new set mate.

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Re: First Scratch Build

Postby OverTheTop » Mon Aug 03, 2015 7:29 pm

If you don't want to change your fins, laminating them with paper is the go. It creates a nice strong composite and means you don't have to fill and sand the grain out. Sirius Rocketry do that with their kits. It works well for LPR.

Alternatively, change to the correct orientation for added strength. Your rocket, your choice :D

Looks good so far!
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Re: First Scratch Build

Postby Roco » Tue Aug 11, 2015 7:33 pm

Thanks for the suggestions to change the fins. I did cut a new set with the grain parallel to the leading edge and papered them as well.

Started and finished the major parts that needed gluing:

Motor Mount
2015-Aug-10 17-08 298.jpg
Motor Mount


The shock cord around the motor mount isn't glued in just slipped over after the glue had set.
Fins
2015-Aug-11 19-08 299.jpg
Fins


The fins were just done a couple of hours ago and I have yet to put some fillets on. OTT I did sand down the body tube until it wasn't shiny and felt like a paper tube.

I've settled on a orange body with a black nose cone.

Looking forward to launching it this weekend at Serpentine.

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Re: First Scratch Build

Postby OverTheTop » Tue Aug 11, 2015 8:06 pm

Looking good. I think not gluing the kevlar braid is a good idea. It allows it to stretch a little over a longer length as it takes the forces applied to it during deployment. A glued one can suffer a break near where the glue stops, although you have used decent braid for that size bird by the look of it. The thicker braid is a good idea as it doesn't zipper the airframe as easy.

Good luck with the flight(s) :D
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Re: First Scratch Build

Postby Roco » Wed Aug 12, 2015 6:08 pm

I've hit a bit of a snag.
For this rockets first flight I was going to send it up on a 18mm RMS motor and bought an adapter to do. The adapter required a retainer set but that hasn't arrived yet. Could I friction fit the motor into the adapter and tape it in place? Would that be considered safe and would that pass RSO inspection? Pictures attached if my description wasn't clear enough.
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2015-Aug-12 16-08 210.jpg
2015-Aug-12 16-08 209.jpg

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Re: First Scratch Build

Postby kopius » Wed Aug 12, 2015 11:21 pm

There shouldn't be any reason for an RSO to not allow friction fit if done correctly. A few little tips which some maybe overkill, but certainly work well:
1. Put the motor hardware all the way into the adaptor, then run tape around the top. This means the motor cannot physically be removed from the adaptor without removing the tape.
2. Whilst the tape around the bottom may work ok, because the adaptor has limited surface area, grab some spare shock cord and tape that to the top of the motor case where you have taped it above the adaptor. Run the shock cord through the rocket and tie the other end somewhere further up (or just onto the normal shock cord). This means if the adaptor spits out it is still tethered to the rocket.
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Re: First Scratch Build

Postby Lamp » Wed Aug 12, 2015 11:34 pm

G'day Roco, come and find me at the launch and I'm sure we will be able to get your rocket in the air...
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Re: First Scratch Build

Postby Roco » Thu Aug 13, 2015 7:06 pm

Luckily the launch was delayed and the motor retainer should turn up by then and I won't have to use my 'bodge job'. :D Got the fillets on a couple of hours ago and I'll post a picture tomorrow.
Thanks for all of the feedback on this build it has stopped me making some bad choices.


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