I am currently trying to design a model rocket which deploys wings and activates an engine while in flight. In essence, becoming a airplane UAV after reaching a certain height.

However, I do need some help on deploying the wings and what kind of engine I should use. We need one that can be started via some kind of automated system.

The weight of the "plane" will probably be around 30-50 lbs. The plane itself will have a cylindrical fuselage, nose cone, 2 wings that will deploy, and 4 stabilizers in the back aranged in a star pattern. (they will double as stabilizers during launch. Also, the fuselage will be atleast 5-7" in diameter

The placement of the engines hasnt been determined, so any method can be looked at.

You are building a 30-50 pound plane and this is your first post on rcu?

do you realize what type of rocket engine is needed to launch that weight? nothing bought commercially from aerotech...

Its part of a group project, and I stumbled on this site. Figured you guys might be able to help me.

And, yes, we do know how much, to be precise, we have a O-class motor already, as well as a smaller P-class motor waiting.

Both of those motors are from other projects that have finished and have passed along their stuff. Chances are its too powerful for our rocket.

But my real question isnt about the rocket part, we have some help on that standpoint, but on the airplane engine.

There are some electric starters that have been manufactured for a few of the "mid - size" gasoline engines. But I don't think I've seen anything for the size engine you're going ro need.

Your group might be able to use a decent electric motor and develop one yourselves though. All you need is a flywheel behind the prop.

You do realize that you're probably approaching $700 to $800 minimum for an engine to pull that weight right?

As for wing deployment; I've read posts where guys have developed small (60" wingspan) jets with scale swept wings. Using a pivot point and strong enough servos should allow for it, but setting up the geometry would be a bear. The problem will probably be in the limited travel of the servos.

Sounds intriguing though. You might try posting the wing deployment question in the jets forum.

For the wings i'd have them hinging forward, that way once there activated the wind resistance is asisting.

may be a simple servo actuated retaineng mecanisim with a spring and a latch once there open.

as for the engine start what about a small turbine, that way the thrust to weightwould be good and you could use compressed air for start.

All depends on the $$$ you can spend.

there are remote glow and starter systems for the more traditional model engines, try asking over at the giant and scale forums.

also fo safty i'd seriously consider a safty parachute system for a model that heavy

look at some of the old estes models. what they did is had a one piece wing with a pivot in the center, and slid out horizontally. i would say this is your best chance. one more thing. if u are using an O motor, u are going to be a few miles up. hope you have cameras or really good vision. as far as the engine, use a turbine. if i was doing this, i would stage the thing, and have the motor drop away. also, u are going to be in the few hundred pound range. O motors themselves weight more like 100 something lbs.

Thank you all for your responses.

Actually, that estimate of the price is alot lower than I expected. That wing deployment sounds like a good possiblity, its actualy one of the ways I've been looking at after doing some web searches.

Thanks Woodsy, thats an idea I hadnt really looked into, to use a spring, and servo-controled hatch.

Using a one-piece wing is a possiblity, it would allow for a higher chord, but it would also take up more room inside the rocket during launch.

As for the motor, we are planing for the motor to drop off from the rest of the rocket, so we dont have to pull the weight of the empty casing

Lastly, the weight is probably an over-estimate, basically a guess based off previous projects, however we do plan on using a saftey parachute as well as a video-downlink from the nose of the rocket. Also, at launch we will have several cameras and such to keep track of it.

Looks like I'll be heading over to the other parts of the forum.