Aeroplane-rocket hybrid

[TWJian]

I'm taking part in a local water-rocket competition. I was thinking about building a rocker-aeroplane hybrid as the distance rocket. I used a delta wing design(swept-back at 25 degree) with a T-tail. However, my rocket has a tendencency to stall after launch (approx 30m). Further trimming odes not fix this. Does anyone have any ideas?

 

P.S.: I have built a conventional rocket for the distance category in the evnt that this fails or the wind is too strong. (so don't suggest me to build a conventional one: I have already built it)

 

For the duration category, I got problems with the parachute deployment system. the problem is either holding the nose cone stable during flight or other end of the spectrum, making it fall off at apogee. Can anybody help me?

[atinymonkey]

A delta wing design is dependant on constant speed and weight. The weight of your small craft will be diminishing rapidly after takeoff, affecting the trajectory and airflow over the delta wing which causes the stall. You'll be needing a fixed straight wing, even if it doesn't look cool. The straight wing will present a greater area for uplift, and help prevent the stalling. Have a look at glider designs, as they will provide the greatest distance from the force applied.

[Edward]

For the parachute you need to look at model rockets avaible at a hobby shop. You should be able to find a cheap one ie 10-20$ and get a good idea of how the mechanism works.

[TWJian]

For the parachute you need to look at model rockets avaible at a hobby shop. You should be able to find a cheap one ie 10-20$ and get a good idea of how the mechanism works.

 

Oh great they aren't any hobby shops near where I live. Thanks anyway.

[TWJian]

A delta wing design is dependant on constant speed and weight. The weight of your small craft will be diminishing rapidly after takeoff, affecting the trajectory and airflow over the delta wing which causes the stall. You'll be needing a fixed straight wing, even if it doesn't look cool. The straight wing will present a greater area for uplift, and help prevent the stalling. Have a look at glider designs, as they will provide the greatest distance from the force applied.

 

So how long should the wing be? The rocket diameter is 7 cm with a length of 36 cm with the nosecone. So should I use conventional glider tails?

[flyboy]

go with a full glider design then it will fly farther

[atinymonkey]

So how long should the wing be? The rocket diameter is 7 cm with a length of 36 cm with the nosecone. So should I use conventional glider tails?

 

Well, it would depend on the weight and the power to propellent provides. For a normal glider, 75cm would do fine. But you could have a lot of power, where a snub wing would suffice. You could probably even get away with repositioning the wings so they are straighter. Your best bet it to ask the experts: -

 

http://www.rcgroups.com/forums/index.php

 

It'd take forever for me to work it out!

[TWJian]

Well' date=' it would depend on the weight and the power to propellent provides. For a normal glider, 75cm would do fine. But you could have a lot of power, where a snub wing would suffice. You could probably even get away with repositioning the wings so they are straighter. Your best bet it to ask the experts: -

 

http://www.rcgroups.com/forums/index.php

 

It'd take forever for me to work it out![/quote']

 

Well, I'm using 50 psi and the cross-sectional diameter of the rocket nozzle is 21.5mm. By the way, you meant 75 cm for each wing or is it the wingspan? And is a snub wing rounded at the tips and not rectengular? Forgive me but I'm not rather conversant with aeronautic jargons. What should I use to make the wings? I'm using foam now. Or should I make a frame and apply heat-shrink plastic on it? (wondering how to get balsa wood) And should they be joined together at the top ot the centre of the rocket? (near the centre of gravity). And for the tail, is it better if I use a V-tail? Though, I didn't use a glider design at first because I'm afraid of drag and its dependency on wind. Is there any way to enable the glider to fly roughly straight regardless of wind? Thank you.

 

P.S: I got problems accessing the rcgroups forum. (the usual this web-page is not available)

[TWJian]

For a round parachute, what's the optimum centre hole for a given diameter? Is there a formula for this?