Well, Adam pointed out that I should start a new thread for this one – I was browsing around for kits and then suddenly thought that helicopter recovery might be fun.  Then I started wondering how I might go about doing it.  So without doing any research what-so-ever I bought a few bits.  Hopefully it flys, while I wait for the bits to arrive I'm going to model it on RockSim – that's the right way round to do it yeah?

The basic idea is to have a 54mm body with a 38mm inner tube.  Now, the helicopter wings are quite hard to keep out as far as I can think – so I'm going to hold them out with some neoprene pipe (which is hopefully going to do a better job than elastic bands).  The idea is to have some kind of bulkhead to hold the three wings in to the body which releases them when the ejection charge pushes a bulkhead up and releases them.  I would read that over again to see if it makes sense, however I can't bring myself to do it.

Above that there should be loads of room for electronics and with the 38mm tube for the engine it should have plenty of lifting power.  That's where I hope to shove in a microcontroller and test out a bunch of different altimeters, accelerometers etc.  However, those will have to be a future addition as I don't have the time to make both.

Does anyone have any comments on the build or suggestions?  Also, how high up the 38mm tube should I position the thrust ring?

I'll give it a go I think – dropping it off a few buildings to make sure it works first.  Else, I'll just do some kind of kit.  I'm a bit bored with standard kits now :)

That's interesting, so how do you fit them? Obviously you don't glue it in.

I've been doing my research on this, it seems that my idea for releasing the blades is not entirely new, which is good – because since it's worked before, it should work again.  However, no one else seems to have done it on quite the same scale.  I don't see why that should be an issue – other than it being a bit heaver if it falls to the ground!

All the designs I've seen so far have the hinges and elastic bands on the outside of the rocket.  I can't help but think that doesn't do wonders to the aerodynamics.  Then again, cutting three holes in the body tube probably doesn't help either – anyone have any opinions on which might be best?

I'm considering making the lower bulkhead have an optional vent in it for drogue deployment.  That way I can still test the rocket with a parachute so it's not totally hammered if the blades don't work perfectly the first time.  Has anyone got any ideas about how I could do this so I have the option to re-seal it?

Also, my latching mechanism will be basically one bulkhead with pins in it moving up due to the ejection charge.  I am thinking of covering it in aluminium to protect it from burning (it's not an issue for recovery if it does burn – however it does affect the re-usability).  Do people have any experience with this, does it protect sufficiently, and if so – how many layers should be applied?

Hopefully some parts will arrive tomorrow so I can start playing :)

Hey Chris, 

One approach you could take is to build and fly a reduced scale model before moving up to the high power version. This will give you chance to prove your concept and refine it before throwing a large motor in the back. It will also give nervous RSOs like Matt and Paul confidence in your build and design skills and when they ask you how do you know this will fly safely etc., you can use your scale model pedigree. 

Coating parts in epoxy glue or even glass fibre is also a good fire proofing treatment and can add structural strength if required. 

From what I have seen, which admittedly is very little, the designs seem to fall into two general groups, those where the blades either form part of the airframe or are on the outside and those with the blades within the airframe until apogee. Parachute backup is certainly a good idea, you could use a timer backup connected to an black powder charge, as I guess you will want to use the motor ejection charge to deploy the blades (or vice-versa). I've often wondered about an emergency wireless (radio) ejection charge system by which you can deploy a parachute from the ground if you see your rocket in free-fall. I reckon you could make it acceptably robust and safe if you used some from of data sharing transmission to set-off the charge as opposed to a simple carrier type system which is susceptible to interference and had a way to inhibit the system on the ground (e.g. switch)?

Hey Dude, 

How's the Zigbee bidding going? You won it yet? Have had a look at some of the development kits before and always been tempted; be interested to see how you get on setting it up and seeing how easy (or not) it is to get reliable data transfer. What sort of range do you expect from the kit you're looking at?

Keep an eye-out at Midland Sky, we've used to get some guys who come down who are very hot on telemetry and in-flight electronics, worth seeing what they've got and how they do it. 

Adam

Damn – I got outbid!  I put in 20 and it said "please enter a correct amount". That's annoying.

Thanks.  I'm still holding out for the parts to come through for me to have a go at my own.  Experience with a kit will make it much easier.

Sounds great.  Still waiting on parts for this that I ordered months ago!