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Old 12 August 2008, 14:22   #21
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this page might help:

http://www.navagear.com/2008/06/dsc-...-chartplotter/
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Old 12 August 2008, 14:31   #22
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Interesting to note that the Raymarine C80 only has one NMEA port according to that article. Not doubting it but one isn't many. Could be a bit limiting...
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Old 12 August 2008, 15:36   #23
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A lot to think about

Thank you all for your input. We are thinking BIG thoughts ;-) right now about how, where and especially why (as in "why isn't it possible this way?" in a whining tone)... Actually we might end up _without_ using a direct input to the chart plotter. Simply because of the bad transmitting possibilities of a gps-connected radio in the water. Instead we might rely on a simple, analog radio beacon for homing in when we arrive at the splash zone.

One note on the idea of a helium filled balloon: We have been considering this for some time but we have to fly an awful lot of gas to get a decent size balloon to lift. Pressure bottles are very heavy for the rocket and we would like to avoid them because the weight will cost a lot of altitude.

A possible solution is to fly a 33g CO2 bottle from a life jacket since they are very much lighter than your usual pressure bottle. The limited measure of gas in it should then inflate something with a small volume - like a tetrahedron built with tubes - that lifts the beacon antenna off the water. Any input on this would be appreciated but I fear that we are way off topic now for a rib forum?

If you PM me I shall be glad to keep you posted on our progress and I will also update this thread when we get the system flying. This, however, might take a year or more.

Thanks again.

Best
RocketDane
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Old 12 August 2008, 16:53   #24
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You might be able to refill a butane-type container with helium for a ballon type device. You'd need proper adapters to decant from a higher pressure supply. Then you could either fly a ballon proper or an aerial for radio signals.

A round ballon would make a lousy radar target so you are on the right track with some sort of tetrahedron. You might inquire at a competitive kite shop about making something that could be deployed at low altitude and then stay aloft in a light breeze with enough lift to suspend (X? gms).

The NEMA input is the easy part

Richard
(KD7SCR in the amateur radio world)
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Old 13 August 2008, 05:25   #25
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Quote:
Originally Posted by RocketDane View Post
A possible solution is to fly a 33g CO2 bottle from a life jacket since they are very much lighter than your usual pressure bottle.
Errr . . . isn't CO2 heavier than air?
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Old 14 August 2008, 08:53   #26
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Danbuoy

Quote:
Originally Posted by MikeCC View Post
Errr . . . isn't CO2 heavier than air?
Yes it is. But the idea is to inflate a rigid construction with a small volume - like a tetrahedron built with tubes - that floats and lifts the beacon antenna off the water. This would eliminate the need for lift and that way we could use the lighter CO2 bottles (with the heavy gas inside).

But now I have my eyes set on the Danbuoy:
http://www.plastimo.com/catalogue/in...ngID=1&catid=4
It will surely do the trick but I don't yet know how heavy it is. The company has not yet replied to my mail about this.

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Old 15 August 2008, 06:13   #27
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Quote:
Originally Posted by RocketDane View Post
Yes it is. But the idea is to inflate a rigid construction with a small volume - like a tetrahedron built with tubes - that floats and lifts the beacon antenna off the water. This would eliminate the need for lift and that way we could use the lighter CO2 bottles (with the heavy gas inside).

But now I have my eyes set on the Danbuoy:
http://www.plastimo.com/catalogue/in...ngID=1&catid=4
It will surely do the trick but I don't yet know how heavy it is. The company has not yet replied to my mail about this.

Best
RocketDane
OK, so just to float it on the water?

Danbuoy would be fine except they have a weight in the base to stabilise them in the water. The Seago ones we sell weigh around 4Kg, so possibly a bit heavy! They will just flop over with no ballast.
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Old 16 August 2008, 12:11   #28
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Originally Posted by RocketDane View Post
Hello collective wisdom

Shortly our rocket society will be launching scientific rockets (all-metal, 6-10 foot long, 8 inch diameter) from a Danish military shooting range on the coast and out over the North Sea. For recovery we have purchased a Zodiac Hurricane 440 to sail the necessary 10-20 miles offshore. But once there we also need to find the rockets, and for this we have a built-in gps-reciever hooked up to a radio transmitter in the rocket.

Now we need advice on which chartplotter to buy which best utilizes the data from the rocket. The plotter must be able to accept radiotransmitted gps-data and mark the spot with an "X" on the map. (We can build an electronic device to change the data from the radio reciever into any format demanded by the plotter).

The plotter should also update the mark as the target moves in the water and should of course be able to dynamically plot a course towards the object.

I would prefer it to be able to read owner┤s own maps also. And it should be detachable and usable on land as well since we also launch to lower altitudes at landlocked shooting ranges.

Any ideas/suggestions?

Thanks

RocketDane
www.mainstage.dk

PS Oh - and don't worry about safety. The ranges are of course closed for all air and sea traffic during launches.
Coming into this a bit late but having read the other parts of the thread a couple of thoughts occur:
1. How about going for radar on the rib and a sart type unit built into the rocket
2. Use a plotter and ais unit on the rib and a radio on the rocket to transmit an ais signal.

Both transmitters might have to be custom built for weight and neither solves your transmit ariel problem but recieve end cold be bog standard stuff. Also not sure how legal it might be to use those frequencies for this purpose!
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