Build Thread: 7 cell parasail w/ RC control

The parawing is an interesting concept and will definately be held in reserve. Right now I have the ram air chute assembly underway. If this sends me back to the drawing board, we'll move forward from there.

jazzviper1, I ask a question earlier when you said the Ram Air chutes could handle rocket speed deployments. What do you consider rocket speed deployments? As I stated, this will only be deployed as the main on a dual deploy rocket at about a 50 ft/sec speed.

You also might want to look into the nasa parawing series https://freedom2000.free.fr/NPW_Teega_plans_eng.html

Not as much a concern on dual deploy, especialy at only 50 fps. I would still make sure to use the slider and deployment brakes though. The deployment brakes are easy just set the NO brake ( no pulling on the stearing lines ) at the top of the transimitter stick travel so that when the stick is at nutral position the canopy will be in partial brakes. You then just hold the stick forward for full glide. It is what I used on my .40 size paraplane. I had to use long controll arms to get a good flare on landing it took some mods.
I hope this helps.

To be honest, I'd be less worried about opening shock damaging the parachute than I would it damaging the servo. The gears inside those things are typically plastic, and will strip pretty easily.

As I write this, I remember one of the Iowa State team members telling me that they trashed a couple servos before learning some things.

I'd definitely suggest the parachute be bagged, to help keep a neat, orderly deployment, as well as reduce opening shock.

-Kevin

troj said:

To be honest, I'd be less worried about opening shock damaging the parachute than I would it damaging the servo. The gears inside those things are typically plastic, and will strip pretty easily.

As I write this, I remember one of the Iowa State team members telling me that they trashed a couple servos before learning some things.

I'd definitely suggest the parachute be bagged, to help keep a neat, orderly deployment, as well as reduce opening shock.

-Kevin

Click to expand...

or you could buy a servo that isnt junk....
I personaly would use a dc stepper motor.(gearless servo)

troj said:

To be honest, I'd be less worried about opening shock damaging the parachute than I would it damaging the servo. The gears inside those things are typically plastic, and will strip pretty easily.

-Kevin

Click to expand...

The really hot RC sailplane guys, the ones in the competition/thermal duration events, used to strip servos regularly when they would dork it in - with full flaps - to get their landing points...
Some of them were in the habit of carrying spare replacement flap servo gears and changing them out ...others opted to use metal gears.

Handeman said:

The parawing is an interesting concept and will definately be held in reserve. Right now I have the ram air chute assembly underway. If this sends me back to the drawing board, we'll move forward from there.

Click to expand...

Yes, you could put a parawing in the reserve....
(Sorry, couldn't resist that one)

troj said:

To be honest, I'd be less worried about opening shock damaging the parachute than I would it damaging the servo. The gears inside those things are typically plastic, and will strip pretty easily.

As I write this, I remember one of the Iowa State team members telling me that they trashed a couple servos before learning some things.

I'd definitely suggest the parachute be bagged, to help keep a neat, orderly deployment, as well as reduce opening shock.

-Kevin

Click to expand...

The pressure on the steering lines WON'T be enough to strip the servos unless your using micro servos.

Slightly off topic....but while we're on the subject of "parawings":

I recall seeing a video awhile back of a couple of parawings in flight (CRW) with a ramair running circles around them.
Check out the collision - and the cut aways.

The last part of the video (from the helmetcam on the guy riding the square) is interesting ...you get a perspective of how low they were getting.

...here it is:

https://www.youtube.com/watch?v=S8wET-7GmHc&feature=related

MaxQ said:

Slightly off topic....but while we're on the subject of "parawings":

I recall seeing a video awhile back of a couple of parawings in flight (CRW) with a ramair running circles around them.
Check out the collision - and the cut aways.

The last part of the video (from the helmetcam on the guy riding the square) is interesting ...you get a perspective of how low they were getting.

...here it is:

https://www.youtube.com/watch?v=S8wET-7GmHc&feature=related

Click to expand...

Trying to perform CReW (canopy relative work) with Petrodactyl chutes was not the wisest idea. They don't react quite the same as ram airs do to close quarters. They do how ever have nearly the same glide ratio as lightly loaded ram airs do. Part of thr reason the other guy was flying rings arround them was because he had a high load expert wing. He is probably a "turf surfer".

jazzviper1 said:

Trying to perform CReW (canopy relative work) with Petrodactyl chutes was not the wisest idea. They don't react quite the same as ram airs do to close quarters. They do how ever have nearly the same glide ratio as lightly loaded ram airs do. Part of thr reason the other guy was flying rings arround them was because he had a high load expert wing. He is probably a "turf surfer".

Click to expand...

Turf surfer ....or swooper.....

I got interested in the sport again last summer and went out to the local DZ (West Point VA) just to check out the modern gear and get inside a Sky Van and look around. (It was a birthday Boogie for Carol Clay...she has 17,000 jumps and counting...over 260 hours in freefall)
The hankerchiefs these swoopers fly today are a world apart from the old days of jumping.

MaxQ said:

Turf surfer ....or swooper.....

I got interested in the sport again last summer and went out to the local DZ (West Point VA) just to check out the modern gear and get inside a Sky Van and look around. (It was a birthday Boogie for Carol Clay...she has 17,000 jumps and counting...over 260 hours in freefall)
The hankerchiefs these swoopers fly today are a world apart from the old days of jumping.

Click to expand...

I wish I could afford to get back into jumping. I wana fly a wingsuit soooooooo bad! I also loved accuracy jumping.

jazzviper1 said:

Not as much a concern on dual deploy, especialy at only 50 fps. I would still make sure to use the slider and deployment brakes though. The deployment brakes are easy just set the NO brake ( no pulling on the stearing lines ) at the top of the transimitter stick travel so that when the stick is at nutral position the canopy will be in partial brakes. You then just hold the stick forward for full glide. It is what I used on my .40 size paraplane. I had to use long controll arms to get a good flare on landing it took some mods.
I hope this helps.

Click to expand...

That actually helps quite a bit. I was going to set it up with a rubber band holding the two sticks together so they were both in the up or glide position and I had full travel for pulling down the canopy. Sounds like I need to rethink that.
I have zero experience with RC and servos. Will the opening forces pulling on the arms hurt the servos? I did get metal gear servos.

Handeman said:

That actually helps quite a bit. I was going to set it up with a rubber band holding the two sticks together so they were both in the up or glide position and I had full travel for pulling down the canopy. Sounds like I need to rethink that.
I have zero experience with RC and servos. Will the opening forces pulling on the arms hurt the servos? I did get metal gear servos.

Click to expand...

The opening forces should not hurt the servos.
Does the premade chute you have have seperate stearing lines attatched to the trailing edge? Or was it set up for weight shift like the old sky surfer paraplane where it just tilts the canopy be pulling down one side or the other?

jazzviper1 said:

The opening forces should not hurt the servos.
Does the premade chute you have have seperate stearing lines attatched to the trailing edge? Or was it set up for weight shift like the old sky surfer paraplane where it just tilts the canopy be pulling down one side or the other?

Click to expand...

That was someone else that has the pre-made chute. I'm building a ram air. All the parts are cut out and it's ready to start sewing. Now I just have to get home next week and get started. Of course the chute got pushed down the priority list by a couple of other projects over the last few days.

Depending on how ambitious the college teams were, I may have some reports on efforts to do this kind of thing after May 7th. That's launch day for the Wisconsin Space Grant Consortium collegiate rocketry contest, and this year's goal is to be able to guide the rocket down to a spot on the ground.

This was the goal several years ago as well, and none of the teams were successful. The most promising design, I thought, had a ram-air chute with control servos sewn into the chute. They would be used to collapse cells on one or the other (or both) sides. Unfortunately, the rocket had an accident on the way up, so we never saw how it went.

Here's the rules:
========================
Competition Engineering Parameters**

The object of this year's competition is to design a single stage, controllable descent rocket. The rocket must attain a minimum altitude of 2000 ft. and be recovered safely and in flyable condition. The rocket will require an electronically deployed parachute recovery system. The winner of the flight portion of the competition will be the team whose rocket completes a successful flight and has the shortest distance from the designated landing point. All structural components and materials must be obtained from reputable high-powered rocketry vendors, or an engineering analysis demonstrating their suitability must be included with the design.

Equipment provided by WSGC:
Rocket Motor – teams may select 1 from the following list of motors
I285; I435; J350; J364; J500; K550; K513; K805
Flight Recorder
R-DAS Tiny - https://www.aedelectronics.nl/rdas/tiny.htm
1.1 in. x 3.5 in.
(This is separate from the team's electronic deployment system and will be inserted at time of launch to record acceleration & altitude vs. time)
=====================

sylvie369 said:

The most promising design, I thought, had a ram-air chute with control servos sewn into the chute. They would be used to collapse cells on one or the other (or both) sides.

Click to expand...

This sounds like a very viable design. It would be very interesting to find out how this works. The standard ram air chute with rear control lines is a proven design, but that is for a person pulling the lines. On a servo controlled design, this might work better.

Let me know how it turns out when you can.

Handeman said:

This sounds like a very viable design. It would be very interesting to find out how this works. The standard ram air chute with rear control lines is a proven design, but that is for a person pulling the lines. On a servo controlled design, this might work better.

Let me know how it turns out when you can.

Click to expand...

Hopefully a week from today, weather permitting.

The reason that design looked the most promising to me was that the servos were not connected to long control lines going out to the parachute, but rather to short pieces in the parachute. I can't remember the details of how they were attached, but they seemed FAR less likely than other designs to have servos stripped by the shock of a parachute opening. That would have been my main concern, if my team had used that kind of design (we were a first-year, non-engineering group, so we simply opened our standard chutes by radio control at times that we hoped would bring us close to the target).

The second-most-promising design used a single winch servo with the control lines both around the same drum in the payload bay. He didn't open high enough for us to see if there were any control - his chute opened just before the ground. Apparently everything survived, though, which is promising.

Handeman said:

This sounds like a very viable design. It would be very interesting to find out how this works. The standard ram air chute with rear control lines is a proven design, but that is for a person pulling the lines. On a servo controlled design, this might work better.

Let me know how it turns out when you can.

Click to expand...

Ram air chutes are not designed to be steared this way. Colapsing cells even in a controlled maner is considered a bad thing.
The trailing edge warping that is normaly used is a proven and reliable way to steer the canopy. Plus you cant flare the chute for touchdown by colapsing cells. the flare is very important because the chute is traveling forward at arround 10 to 20 mph depending on wing loading. You could be looking at broken fins or worse.

sylvie369 said:

Hopefully a week from today, weather permitting.

The reason that design looked the most promising to me was that the servos were not connected to long control lines going out to the parachute, but rather to short pieces in the parachute. I can't remember the details of how they were attached, but they seemed FAR less likely than other designs to have servos stripped by the shock of a parachute opening. That would have been my main concern, if my team had used that kind of design (we were a first-year, non-engineering group, so we simply opened our standard chutes by radio control at times that we hoped would bring us close to the target).

The second-most-promising design used a single winch servo with the control lines both around the same drum in the payload bay. He didn't open high enough for us to see if there were any control - his chute opened just before the ground. Apparently everything survived, though, which is promising.

Click to expand...

Trust me I skeek from experiance the servos won't strip.
The single servo won't allow you to flare this is a must to reduce landing speed!

Looks like trailing edge flaring with two servos to slow forward speed is the way to go. I did get metal gear servos so I'll stop worring about that. If they strip, they strip, at least the chute will be out and the rocket recover safely, even if it is farther away then planned.

Hopefully I can gets some work done on the chute this weekend.

Well, something like 6 teams managed to open up chutes connected to control lines connected to servos in the contest at Bong yesterday, but no-one had anything remotely looking like steering control.

One that looked like it might work wound up wrapping shroud lines around a fin, so no go. A couple of others opened their chutes just fine, but the chutes were spinning, the rockets were twisting, and the pull of the servos - assuming there was some pull - wasn't nearly enough to do anything to counter all of that. I think it's going to take a big, stable chute, and a lot of pull on the lines.

sylvie369 said:

Well, something like 6 teams managed to open up chutes connected to control lines connected to servos in the contest at Bong yesterday, but no-one had anything remotely looking like steering control.

One that looked like it might work wound up wrapping shroud lines around a fin, so no go. A couple of others opened their chutes just fine, but the chutes were spinning, the rockets were twisting, and the pull of the servos - assuming there was some pull - wasn't nearly enough to do anything to counter all of that. I think it's going to take a big, stable chute, and a lot of pull on the lines.

Click to expand...

What kind of chute were they using?
Were they hommade?
If the were ram air and home made they had to have been strung correctly to fly and controll. If the chute is not rigged evenly then no controll input will help. It does not take much "pull" on the controll lines to steer the chute.
You can steer a full sized one with just a small amount of arm strength it is realy easy.

I finally got something done on the ram air. I got it all sewn up. It sat around for 5 months, but Saturday night I got started and finished it up about 2:30 in the morning.

I still have to rig all the shroud lines, but hopefully that won't take another 5 months.

Here's a pic of the sewn chute. It's laying upside down with the front edge hanging off the table some.

I see this thread went form May to October to March. Seems like 5 months is a patter here.

Anyway, I have the chute done and rigged up with 12º downward pitch. The RC unit is also finished, well almost. I still have to install an anchor point for the chute. Everything else is together and fits inside a 11" long piece of 4" coupler tube. The servos operate two arms which increase the throw and give me 4.75" of pull on the steering lines. That should be enough, although I don't know how much flare I will be able to get for landing.

There is a pair of micro servos whose arms contact each other when active and have electrical wires attached. When both are activated, they will fire an ematch to set off the ejection charge allowing me to control deployment.

The tough part is going to be getting the chute packed in the 10.5" of 4" BT I have left in the payload.

Still have some work to do, but the light is at the end of the tunnel. Attachments, packing, and ground testing the ejection charge is about all that's left. Then it's off to the BattlePark this Friday for it's first flight test!

That's not 7 cells anymore, is it?

CarVac said:

That's not 7 cells anymore, is it?

Click to expand...

Yes, it's a 7 cell chute. It's just a scaled down version of what most skydiver use. Each of the cells is divided, but the lines are attached along 8 ribs, including the ends.

The pic isn't the best, by you can see the cell dividers and the shroud lines fairly well.

Ah. I didn't notice the difference between the dividers and the main ribs at first.

First test flight!

So - So. The chute deployed via radio control like it was supposed to. The shrouds tangled and things twisted up. The chute was about 3/4 open and the ground was soft so there was no damage to the rocket or anything else.

Now I just have to figure out how to get it to deploy and open correctly.

Guess I haven't been keeping up with this. I had my 4th test flight today. The first two ended up about the same, tangles. For the third flight, I made a deployment bag. I messed up with the RC controlled deployment, hit the wrong switch on the radio. By the time I figured it out, I think the altimeter and the RC charges both went off at the same time. That's the only reason I can thing of that would have cause the fiberglass re-enforced BT to get zippered 12" when the chute never opened. I've glassed a new tube and had the rocket together for a flight yesterday.

On to the fourth flight. I used a J350W so the altitude was 1700 or so, don't have the notebook with me right now. The main deployed shortly after apogee. It was hard to tell, but I thought the nose cone and pilot chute came out with the apogee charge. If that's the case, I'll have to reduce the apogee charge a little.

Anyway, the final result was that the ring in the middle of the line between the pilot chute and the main chute was supposed to be stopped by the grommet in the top of the d-bag and pull the d-bag off the main. It pulled the grommet out of the top of the d-bag. That left nothing to pull the d-bag off the main so it all came down on the drogue and pilot chutes. Fortunately there was no damage and a new d-bag is in the works.

The new bag will have two kevlar straps across the top and a metal washer sewn into the top of the d-bag. The washer will keep the ring from tearing through the top of the d-bag and the Kevlar straps will keep the washer from pulling out of the d-bag. I'm planning on working on the bag tonight and hopefully will have a test flight tomorrow.