josh-224

Hi,
I am designing a glider for a university project which will be rocket propelled for take off then has to travel the max distance carrying an egg.

I am trying to decide which airfoil design to use, I was thinking of using an e214 profile however im worryed that with the glider being propelled by a rocket at the begining this will effect which design i should choose. Would this profile still be suitable?
Any suggestions or help would be appreciated

thanks for your time

Lownverted

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Hi Josh,

There is a whole sub set of the R/C soaring community that deal with rocket powered gliders, so I would suspect a bunch of information can be gleaned from them. As for a specific airfoil I would start by looking at modern DLG (discuss launched gliders) airfoils. They have to endure a relatively wide speed envelope as well, although not as fast as a rocket launch. My gut says that an Eppler of any type will be out performed by a modern DLG section. Lots of specific airfoil info in the glider section of rcgroups.

Cheers
Red

josh-224

Thats good to know I will look into it. Thanks for the tips

BMatthews

The airfoil for such a project is just about the last thing you need to worry about.

Far more important is the thrust to weight ratio and the speed that will be reached and how the model is trimmed to deal with that speed. Then there's also the transition from powered to unpowered. Normal stable trim results in the nose rising with a rise in flying speed to "correct" the model's flight back to the trimmed flying speed. This means that unless the power from the rocket motor eases off over a couple of seconds from full to zero power the model will be nose up and climbing when the rocket snuffs out. The result would be a stall and dive to a recovery. And usually a few stall cycles before the flight path damps the stall cycles out to normal flying.

None of these tendencies are a very good thing to a model attempting to get the most distance.

speedracerntrixie

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I would agree that trimming is going to play a big part in this. The model regardless of airfoil is going to have to be trimmed to have minimal pitch trim chages with airspeed changes. This will be a combination of correct incedences and CG. When I flew F3B sailplanes ( Multi task ) the sailplanes were required to thermal to spot landing, distance task and speed task. What I would do in adjust the CG aft so the airplane would fly with a touch of down trim. As speed would build, the wing would produce more lift however the slight down trim would become more effective and keep the nose down. That added lift was converted to speed. Even now with the giant scale aerobatic airplanes I fly, the CG is adjusted so that the airplane tracks strait from 1/4 to full throttle.

charlie111

The only advice I can give you is.Try to keep engine thrust in line with the Wing.Higher or Lower will affect pitch with thrust.I would keep c.g. where it is with plane Full of Fuel Solid or Liquid?I would not make it tail heavy at all.It's apt to cause your plane to stall or at least hard to Handle!

speedracerntrixie

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Maybe I should have been a little more clear. By an aft CG I ment towards the aft end of the range. I in no way was meaning tail heavy. I hope that the difference between the two can be understood. An aft or close to neutral CG is in most cases easier to fly due to not being affected by airspeed changes as much as a forward CG would.